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SEPA

---. - - . I ., -. .-. ...,-- " , - . I - 8 1 > Y"" L 1 v -"L - .-- -.-.-- Environmental Protection Laboratory September 1978

- a,,/ I r /

Cincinnati OH 45268 _ . . Agency

Research and Development

Commercial Feasibility of Recovering I omato Processing Residuals 'for Food Use

RESEARCH REPORTING SERIES

Research reports of the Office of Research and Development U S Enviroqmen!al' Protection Agency have been grouped into nine series These nine broad cate- gories were established to facilitate further development and application of environmental technology Elimination of traditional grouping was consciously planned to foster technology transfer and a maximum interface in related tields The nine series are

En v i r o n menta I Ye a It h Effects Research E riv i ron me n ta I Protect i on Tech no logy Ecological Research Environmental Monitoring Socioeconomic Environmental Studies Scientific and Technical Assessment Reports (STAR) Interagency Energy-Environment Research and Deveioprnent 'Special" Reports Miscellaneous Reports

This report has been assigned to the ENVIRONMENTAL PROTECTION TECH- NOLOGY series This series describes research performed to develop and dem- onstrate instrumentation equipment, and methodology to repair or prevent environmental degradation from point and non-point scurces of pollution This work provides the new or improved technology required for the control and treatment of pollution sources to meet environmental quality standards

-- This document is available to the public through the National Technical Intorma- tion Service Spririgfield Virginia 221 61

3

EPA-60012-78-202 September 1978

COMMERCIAL FEASIBILITY OF RECOVERING TOMATO PROCESSING RESIDUALS FOR FOOD USE

W . G. Schu l t z , H. J. Neumann , J. E. Schade J. P. Morgan, P. F. Hanni

Western Regional Research Center , Sc ience and Educat ion Adminis t ra t ion U.S. Department of A g r i c u l t u r e , Albany, C a l i f o r n i a 94710

and

A. M. Katsuyama, H. J. Maagdenberg Na t iona l Food P rocesso r s Assoc ia t ion , Western Research Laboratory

Berkeley, C a l i f o r n i a 94710

In te ragency Agreement EPA-IAG-D5 -07 9 5

P r o j e c t O f f i c e r

H. W. Thompson Food and Wood Products Branch

I n d u s t r i a l Environmental Research Labora tory C o r v a l l i s F i e l d S t a t i o n

C o r v a l l i s , Oregon 97330

INDUSTRIAL ENVIRONMENTAL RESEARCH LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT

U. S. ENVIRONMENTAL PROTECTION AGENCY C I N C I N N A T I , OHIO 45268

DI S CLAIMER

Th i s r e p o r t has been reviewed by t h e I n d u s t r i a l Environmental Research Labora tory , U.S. Environmental P r o t e c t i o n Agency, and approved f o r publ ica- t i o n . Approval does not s i g n i f y that t h e c o n t e n t s n e c e s s a r i l y r e f l e c t t h e views and p o l i c i e s of t h e U.S. Environmental P r o t e c t i o n Agency, n o r does mention of t r a d e names o r commercial p roducts c o n s t i t u t e endorsement o r recommendation f o r use.

ii

a

FOREWORD

When energy and material r e sources are e x t r a c t e d , p rocessed , conver ted , and used , t h e r e l a t e d p o l l u t i o n a l impacts on ou r environment and even on ou r h e a l t h o f t e n r e q u i r e t h a t new and i n c r e a s i n g l y more e f f i c i e n t p o l l u t i o n c o n t r o l methods b e used. The I n d u s t r i a l Environmental Research Laboratory- C i n c i n n a t i (IERL-Ci) assists i n developing and demonst ra t ing new and i m - proved methodologies t h a t w i l l m e e t t h e s e needs bo th e f f i c i e n t l y and econo- m i c a l l y .

This r e p o r t p r e s e n t s t h e r e s u l t s of a 2 y e a r s t u d y on t h e techno- economic f e a s i b i l i t y of r ecove r ing a food g rade material from t h e p e e l r e s i d u e a s s o c i a t e d w i t h t h e "dry" c a u s t i c p e e l i n g of tomatoes. The o v e r a l l purpose of t h e p r o j e c t w a s t o develop a b e n e f i c i a l u s e of a food p r o c e s s i n g r e s i d u a l which i s c u r r e n t l y cons idered a waste material. The r e s u l t s of t h i s s tudy should b e of i n t e r e s t t o tomato p r o c e s s o r s , r e g u l a t o r y agenc ie s , manufac turers of s p e c i a l t y food chemicals and food r e s e a r c h e r s . Fo r f u r t h e r i n fo rma t ion on t h i s s tudy , c o n t a c t t h e Food and Wood Products Branch, I n d u s t r i a l P o l l u t i o n Con t ro l D i v i s i o n , IERL-Ci .

David G . Stephan D i r e c t o r

I n d u s t r i a l Environmental Research Laboratory C i n c i n n a t i

iii

ABSTRACT

In t h e United S t a t e s tomatoes are t y p i c a l l y pee led f o r commercial canning by f i r s t immersing them i n a c a u s t i c ba th t o loosen the s k i n ; t hen , t h e p e e l i s removed e i t h e r mechanical ly wi th rubber d i s c s o r wi th water s p r a y s . When the pee l i s removed mechanica l ly , t h e pee l s o l i d s are n o t d i l u t e d and t h e r e f o r e , are similar t o t h e pu lp of whole tomatoes. Since t h i s removed p e e l i s a t least 12% of t h e unpeeled weight and the p e e l i s about 96% pu lp , t h i s pee l pu lp i s a good source of p o t e n t i a l food material. There are about 1.3 m i l l i o n tons of tomatoes peeled each year i n the United S t a t e s , r e s u l t i n g i n a t least 1S0,OOO t / y r of r ecove rab le pulp. Cur ren t ly t h a t pulp i s d i sca rded as p e e l a t an expense of a t least $2.50/ t o r $12.00/hr. P u l p recovery i s a t t r a c t i v e economically because i t has a p ro jec t ed n e t worth of $187/hr f o r a t y p i c a l 40 t / h r p e e l i n g ope ra t ion . o v e r a l l n e t r e t u r n p e r cannery i s $199/hr , i nc lud ing process ing expenses. This i s a $7,500,000/yr p o t e n t i a l g r o s s r e t u r n 'to t h e United S t a t e s tomato process ing i n d u s t r y and provides a corresponding a b i l i t y t o main ta in lower product p r i c e s t o t h e consumer.

*

The es t ima ted

A 2-year p r o j e c t was undertaken t o determine the commercial f e a s i b i l i t y of recover ing pu lp from t h e pee l ings of c a u s t i c pee led tomatoes. In 1975, pee l from r e g u l a r cannery ope ra t ions w a s processed through a 20-gpm ( 5 t / h r ) continuous-flow l i n e . This process ing c o n s i s t e d of a c i d i f y i n g t h e p e e l t o pH 4.2 w i t h food-grade hydrochlor ic a c i d , then s e p a r a t i n g the pulp from t h e s k i n wi th a paddle f i n i s h e r ( sc reen ) . t o be of food q u a l i t y but conta ined h igh peel ing-aid r e s i d u e s (150-450 ppm). P r a c t i c a l l y a l l tomato pee l ing ope ra t ions use a pee l ing a i d i n the c a u s t i c ba th t o f a c i l i t a t e uniform pee l ing . Pee l ing a i d s i n c u r r e n t use are approved f o r pee l ing bu t no t a s a d d i t i v e s t o the f i n a l product . In 1976, a l - t / h r p i l o t pee l ing l i n e w a s set up a t a cannery t o s tudy mod i f i ca t ions i n the pee l ing process f o r t h e purpose of reducing peel ing-aid r e s i d u e i n t h e recovered pulp. The p r i n c i p a l mod i f i ca t ion w a s t o pretreat t h e tomatoes by immersion i n a 150°F aqueous b a t h (approximate ly pH 3.6) con ta in ing about 0.15% food-grade oc tano ic ( c a p r y l i c ) a c i d ; subsequen t ly , t h e tomatoes were immersed i n c a u s t i c . The p e e l was removed wi th rubber-disc p e e l e r s . Recovered pulp m e t USDA Qua l i ty Grade A, and t h e o c t a n o i c a c i d l e v e l s were low (0 t o 30 ppm). b i n a t i o n wi th tomato pulp from regu la r sou rces f o r canned products such

Recovered p e e l pu lp w a s found

The proposed use of t h i s recovered p e e l pu lp i s i n com-

*This r e p o r t fo l lows t h e p r e v a i l i n g canning i n d u s t r y practice of us ing the m t e r n a t i o n a l Sys tem of Un i t s ( S I ) i n t h e l a b o r a t o r y and U.S. u n i t s i n t h e manufactur ing ope ra t ions . See TABLE OF CONVERSION FACTORS f o r U.S. t o S I u n i t s .

i v

a s tomato sauce , c a t s u p , p a s t e , and f i l l j u i c e f o r peeled tomatoes. Compo- s i t i o n s of t h e s e products a re governed by t h e FDA S tanda rds of I d e n t i t y , c u r r e n t l y being r e v i s e d ; t h e c u r r e n t r e g u l a t i o n s a l l o w t h e use of l i q u i d from p e e l s and c o r e s but do no t a d d r e s s t h e use of pulp from c a u s t i c pee l s .

This p r o j e c t w a s funded j o i n t l y by United S t a t e s Department of Agriculture-Western Regional Research Cen te r , Na t iona l Food P rocesso r s Association-Western Laboratory, Environmental P r o t e c t i o n Agency, and t h e C a l i f o r n i a tomato p rocesso r s . This r e p o r t was submit ted i n f u l f i l l m e n t of In t e ragency Agreement EPA-IAG-D5-0795 under t h e p a r t i a l sponsor sh ip of t h e U.S. Environmental P r o t e c t i o n Agency, and cove r s a pe r iod from May 1, 1975 t o August 3 1 , 1977. The experimental and a n a l y t i c a l work w a s completed a s of J u l y 15, 1977.

V

CONTENTS

Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii Abs t r ac t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i v F i g u r e s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v i i i Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v i i i Abbrevia t ions and Symbols . . . . . . . . . . . . . . . . . . . . . i x Conversion Fac to r s f o r Uni t s . . . . . . . . . . . . . . . . . . . . Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . x i

1 . I n t r o d u c t i o n . . . . . . . . . . . . . . . . . . . . . . . 1 2 . Conclusions . . . . . . . . . . . . . . . . . . . . . . . . 4 3 . Recommendations . . . . . . . . . . . . . . . . . . . . . . 5 4 . Materials and Control Ins t ruments . . . . . . . . . . . . . 6 5 . Experimental Procedures . . . . . . . . . . . . . . . . . . 9 6 . R e s u l t s and Discussion. General . . . . . . . . . . . . . . 26

Washing and S o r t i n g . . . . . . . . . . . . . . . . . 2 8 Pee l ing Aids . . . . . . . . . . . . . . . . . . . . . 28 Carboxyl ic Acid Pee l ing . . . . . . . . . . . . . . . 30 Peeling-Aid Pre t rea tment . . . . . . . . . . . . . . . 30 Modified-Caustic Pee l ing . . . . . . . . . . . . . . . 31 Peel Removal . . . . . . . . . . . . . . . . . . . . . 31 P e e l F l o w . . . . . . . . . . . . . . . . . . . . . . 32 P e e l A l k a l i n i t y . . . . . . . . . . . . . . . . . . . 32 A c i d i f i c a t i o n . . . . . . . . . . . . . . . . . . . . 34 S a l t (Sodium Chlor ide) . . . . . . . . . . . . . . . . 34 Pulp E x t r a c t i o n . . . . . . . . . . . . . . . . . . . 35 Vacuum Evaporat ion . . . . . . . . . . . . . . . . . . 38 Uni t Opera t ion T i m e s . . . . . . . . . . . . . . . . . 39 Product Color. F lavor . and Vitamins . . . . . . . . . 40 Consis tency. V i scos i ty . and P e c t i n . . . . . . . . . . 41 Amino Acids . . . . . . . . . . . . . . . . . . . . . 45 Product Mold. I n s e c t Fragments. and Bacterial Counts . 45 P e s t i c i d e s . . . . . . . . . . . . . . . . . . . . . . 46 U.S. S tandards of I d e n t i t y . . . . . . . . . . . . . . 47 E f f l u e n t s and Wastes . . . . . . . . . . . . . . . . . 49 Economics . . . . . . . . . . . . . . . . . . . . . . 51

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Bib l iography . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 Appendices

A . Vitamin A A c t i v i t y Method . . . . . . . . . . . . . . . . . 56

..

B . Photometr ic Determinat ion of Anionic Pee l ing Aids . . . . . 59 C . Determinat ion of F a t t y Acids i n Processed Tomato Products . 62

v i i

FIGURES

Number Page

1 Tomato p e e l component diagram . . . . . . . . . . . . . . . . . 2

2 1975 process f l o w diagram . . . . . . . . . . . . . . . . . . . 10

3 1975 equipment p r o f i l e . . . . . . . . . . . . . . . . . . . . 11

4 P e e l tank . 1975 . . . . . . . . . . . . . . . . . . . . . . . . 12

5 Hot b reak vessel. 1975 . . . . . . . . . . . . . . . . . . . . . 13

6 Tramp metal t r a p . 1975 . . . . . . . . . . . . . . . . . . . . . 14

7 Modif ied c a u s t i c pee l ing . 1976 . . . . . . . . . . . . . . . . . 17

8 Acid r e q u i r e d t o reduce pH of c a u s t i c p e e l and pu lp . . . . . . 33

TABLES

Number Page

1 Summary of Typ ica l 1975-1976 Recovered P e e l Pulps . . . . . . . 27

2 A c i d i f i c a t i o n Data. 1975 . . . . . . . . . . . . . . . . . . . . 35

3 Summary of 1975 P rocess ing Condi t ions and S o l i d s Recovery . . . 37

4 Uni t Opera t ions T i m e s . 1975 . . . . . . . . . . . . . . . . . . 40

5 S to rage S t a b i l i t y of Recovered Pulp. 1976 . . . . . . . . . . . 42

6 1976 Canned Samples of Recovered Pulps . 1976 . . . . . . . . . . 43

7 P e s t i c i d e Residues i n Recovered P e e l Pulp . . . . . . . . . . . 48

8 P r o j e c t e d Economics of a Commercial I n s t a l l a t i o n . . . . . . . . 5 1

v i i i

ABBREVIATIONS AND SYMBOLS*

American Chemical Soc ie ty degrees Ce l s ius ( a l s o , carbon i n chemical formulas) about chemical oxygen demand degrees Fahrenhei t f o o t gram g a l l o n s p e r t on gas - l iqu id chromatography g a l l o n s per minute hydroch lo r i c a c i d horse power inch I n t e r n a t i o n a l Un i t s pounds p e r g a l l o n l i t e r s per minute m i 1 1 i g r a m m i l lil i te r m i 11 imole s m i l 1 i m i c rons s o l u t i o n normal i ty sodium c h l o r i d e Na t iona l Formulary n a t u r a l tomato s o l u b l e s o l i d s n a t u r a l tomato t o t a l s o l i d s hydrogen i o n c o n c e n t r a t i o n , l o g 1 / ( H + ) p a r t s p e r m i l l i o n pounds per square i n c h , gauge p r e s s u r e q u a l i t y c o n t r o l r e v o l u t i o n s per minute tons per hour t o n s per yea r t o t a l s o l i d s weight p e r volume weight p e r weight

*This r e p o r t fo l lows t h e p r e v a i l i n g canning i n d u s t r y pract ice of us ing U.S. (Eng l i sh ) u n i t s i n t h e manufactur ing o p e r a t i o n s and Metric ( S I ) u n i t s i n the l a b o r a t o r i e s . See CONVERSION FACTORS FOR UNITS on page i x . -.

CONVERSION FACTORS FOR UNITS

U.S. Uni t s Metric ( S I ) U n i t s

- F (F-32 ) 0.5556 - f t ( f t ) 0.3048 -

( g a l ) 3.785 - g a l (gpm) 3.785 -

g a l / t ( g a l / t ) 4.172 x - - hp ( e l e c t r i c ) (hp ) 746.0 - i n . ( i n . ) 0.02540 - l b / g a l ( l b / g a l ) 0.1198 - P,s i g ( p s i g + 14.7) x 6894 =

- - - i2 Pm

- - -

- t ( s h o r t ) ( t ) 907.2 -

X

C , deg rees Ce l s ius m , meter 1, l i t e r s l / m , l i t e r s p e r min l / k g , l i t e r s per ki logram W , watts m , meter g / c$ , gram p e r cub ic cen t ime te r N / m , newton per sq. meter

( a b s o l u t e ) kg , ki logram

ACKNOWLEDGMENTS

The a u t h o r s a p p r e c i a t e t h e s u p p o r t g iven t o t h i s p r o j e c t by t h e tomato p rocess ing i n d u s t r y ; n o t on ly d i d it ease t h e burden, but t a s k s and judgments were o f t e n sho r t ened and made p o s s i b l e i n a f e w months which o t h e r w i s e might have r e q u i r e d s e v e r a l yea r s . In p a r t i c u l a r , we wish t o thank T i l l i e L e w i s Foods and Hunt-Wesson Foods a t whose c a n n e r i e s t h e f i e l d work was performed. The i r p a r t i c i p a t i o n allowed a p r a c t i c a l approach t h a t could no t be d u p l i c a t e d i n a l a b o r a t o r y o r p i l o t p l a n t . The U.S. Environmental P r o t e c t i o n Agency supported t h i s expe r imen ta t ion in p a r t , t h u s e n a b l i n g t h e work and development t o be c a r r i e d o u t i n t h e short p e r i o d of 2 yea r s .

xi

SECTION 1

INTRODUCTION

In t h e United S t a t e s tomatoes are normally pee led by loosening the s k i n wi th a ho t - caus t i c b a t h and removing t h e p e e l ( s k i n wi th adher ing pu lp , see Figure 1 ) e i t h e r mechanica l ly , such as wi th rubber d i s c s , o r wi th water sp rays . The use of water s p r a y s has dec l ined because of t h e l a r g e amount of water needed (500-1,500 g a l / t * ) and the subsequent problem of waste d i s p o s a l of t h e d i l u t e s o l u t i o n . Removal of t h e p e e l mechanical ly wi th rubber d i s c s reduces t h e water consumption t o a n e g l i b l e amount so t h a t t he p e e l has about t h e same s o l i d s c o n t e n t as f r e s h tomatoes. This material i s c u r r e n t l y d i s - carded as s o l i d waste and c o n s t i t u t e s a t least 12% of t h e o r i g i n a l tomato weight. Since t h i s p e e l i s about 96% pu lp , i t i s a p o t e n t i a l source of food m a t e r i a l . a t y p i c a l 4 0 t / h r pee l ing o p e r a t i o n , a t least 5 t / h r of p e e l i s a v a i l a b l e wi th a g r o s s va lue of $250/hr of ope ra t ion . Cur ren t ly t h a t pulp i s d iscarded as p e e l a t an expense of a t l eas t $2.50/t . Since t h e r e are about 1 .3 m i l l i o n tons of tomatoes peeled each year i n the United States r e s u l t i n g i n a t least 150,000 t / y r of recoverable pu lp , t h e r e i s a p o t e n t i a l g r o s s va lue of $7,500,000/yr , and a corresponding oppor tun i ty t o hold down the product price t o consumers.

This pulp h a s a va lue of up t o $50 / t a s recovered pulp , and from

D e s p i t e t he economic i n c e n t i v e , t h e r e were s e v e r a l t e c h n i c a l o b s t a c l e s such as i n s e c t i c i d e r e s i d u e s , r e s i d u a l s of t h e c a u s t i c and s u r f a c t a n t s from t h e caus t i c -pee l ing a p p l i c a t o r , a c i d i f i c a t i o n of t h e a l k a l i n e peel, recovered- pulp q u a l i t y , product l a b e l i n g , e tc . With t h e s e p o t e n t i a l s and o b s t a c l e s i n mind, a two-year p r o j e c t , beginning i n 1975, w a s undertaken j o i n t l y by t h e U.S. Department of A g r i c u l t u r e (USDA)-Western Regional Research Center , Nat iona l Food Processors Assoc ia t ion (NFPA)-Western Research Labora tory , and t h e tomato process ing indus t ry . The i n i t i a l p l ans were desc r ibed i n Apr i l 1975 ( 1 ) and were based on t r e n d s i n commercial practice and p r i o r in format ion on pu lp recovery p o t e n t i a l (2) ( 3 ) ( 4 ) (5) .

U t i l i z a t i o n of tomato p e e l w a s cons idered dur ing p i l o t tests on the mechanical , rubber-disc p e e l removal system i n 1973 (2 ) . I n a s i n g l e , l a rge - sca l e test conducted i n 1974, pu lp w a s prepared from tomato p e e l ( 3 ) . U n t i l r e c e n t l y tomato pee l w a s removed wi th water s p r a y s a f t e r c a u s t i c immersion, r e s u l t i n g i n too d i l u t e a pee l f o r p r a c t i c a l pulp recovery. A s more of t h e rubber d i s c , mechanical pee l removal u n i t s have been i n s t a l l e d , more p e e l i s a v a i l a b l e that r e t a i n s t h e s o l i d s c o n c e n t r a t i o n of a f r e s h tomato; t h u s p u l p recovery from t h e p e e l i s now p r a c t i c a l .

*This r e p o r t fo l lows t h e p r e v a i l i n g canning i n d u s t r y practice of using U.S. (Engl i sh) u n i t s i n t h e manufactur ing o p e r a t i o n s and Metric ( S I ) u n i t s i n the l a b o r a t o r i e s . See CONVERSION FACTORS FOR UNITS on page i x .

1

a

1 PEEL

PEELED TOMATO

SKIN \ PULP

Figure 1. Tomato peel component diagram.

2

Cons ide ra t ion w a s a l s o g iven t o u t i l i z a t i o n of a d d i t i o n a l tomato s o l i d s d e r i v e d from tomato pomace through an a c i d t r ea tmen t similar t o t h a t demonstrated wi th macerate ( 4 ) ( 5 ) .

The recovery i s accomplished by a c i d i f y i n g t h e p e e l , t hen s e p a r a t i n g t h e p e e l i n t o p u l p (96%) and s k i n ( 4 % ) f r a c t i o n s . Skin i s d iscarded . The recovered p e e l pu lp c o n t a i n s sa l t and could be used i n formula t ing tomato sauce o r similar s a l t e d products . The expe r imen ta t ion , developments, and a n a l y s e s spanned two process ing seasons from June 1975 through December 1976. The 1975 expe r imen ta t ion c e n t e r e d on a cont inuous p rocess ing of p e e l from a r e g u l a r cannery p e e l i n g o p e r a t i o n , t a k i n g t h e p e e l as d ischarged from nor- m a l ope ra t ions . The pr imary g o a l w a s t o e v a l u a t e t h e commercial f e a s i b i l i t y of recover ing tomato pee l pulp as food-grade material from tomato pee l ings and pomace. The material eva lua ted was 100% p u l p (from p e e l ) wi thout combi- n a t i o n wi th o t h e r tomato material as would be expec ted i n normal cannery ope ra t ion . This pe rmi t t ed t h e t r u e i d e n t i t y and c h a r a c t e r of t h e recovered pulp t o be eva lua ted i n terms of t h e USDA Standards f o r Grade and FDA Stand- a r d s of I d e n t i t y .

* During t h e f i r s t yea r of expe r imen ta t ion , t h e p e e l e r s were ope ra t ed by t h e cannery personnel t o conform t o product ion needs , and exper imenta t ion involved o n l y t h e p u l p recovery which had t o a d a p t t o t h e cannery o p e r a t i o n without any i n f l u e n c e by t h e experimentors . O r i g i n a l l y , 1976 w a s p ro j ec t ed t o emphasize p rocess o p t i m i z a t i o n w i t h t h e c a u s t i c p e e l r e s i d u a l . However, a s a r e s u l t of t h e h igh peel ing-aid r e s i d u e s found i n 1975, work i n 1976 w a s p r i m a r i l y developmental and emphasized t h e r e d u c t i o n of t h i s peel ing-aid r e s i d u e i n t h e recovered pulp.

The p r e s e n t FDA Standards of I d e n t i t y f o r tomato pulp a l l o w material from s e v e r a l sources . One source i s t h e l i q u i d ob ta ined from p e e l r e s i d u a l s r e s u l t i n g from tomato pee l ing ope ra t ions . The p r e s e n t (1976) S tandards were w r i t t e n when steam and water pee l ing were p reva len t . Those S tandards are be ing r e v i s e d , and i t i s expected that t h e r e v i s e d S tandards w i l l be a v a i l - a b l e i n 1978.

3

a

SECTION 2

CONCLUSIONS

1. Tomato pulp can b e recovered from c a u s t i c p e e l which amounts t o 15% o r more of t h e f r e s h tomato weight . Curren t p r a c t i c e i s t o d i s c a r d t h e c a u s t i c p e e l . When a c i d i f i e d and sc reened , about 96% of t h e p e e l i s r ecove rab le pulp , and 4% i s waste s k i n . Therefore , waste d i s p o s a l volume is reduced by 96%.

2. Recovered pulp can meet USDA Grade A S tandards f o r c o l o r , f l a v o r , and absence of d e f e c t s .

3. The recovered pulp c o n t a i n s s a l t , has a n i n t e n s e r e d c o l o r (maximum Grade A s c o r e ) , has a t h i c k cons i s t ency t h a t i s due t o i n s o l u b l e mate- r ia ls , and is s u i t a b l e f o r u se i n s a u c e s , e tc .

4. The p r e f e r r e d method of c o n t r o l l i n g t h e p e e l i n g a i d level i n t h e recovered pu lp is an o c t a n o i c ( c a p r y l i c ) a c i d p re t r ea tmen t of t h e tomatoes, i n s t e a d of u s ing p e e l i n g a i d d i r e c t l y i n t h e c a u s t i c app l i ca - t o r . Although s team-peelable tomatoes can be pee led by o c t a n o i c a c i d a l o n e (wi thout c a u s t i c ) , c a u s t i c is g e n e r a l l y needed f o r c u r r e n t C a l i f o r n i a varieties such as VF-145B-7879.

5. Pulp recovery is an economical ly f e a s i b l e process i n which t h e c a p i t a l inves tment can be recovered i n l -year ; t h e r e a f t e r , t h e n e t r e t u r n is about $200/opera t ing hour f o r a 40 t / h r c a u s t i c p e e l i n g ope ra t ion .

4

S E C T I O N 3

RECOMMENDAT I O N S

1. I n d u s t r y should seek r e g u l a t o r y c l a r i f i c a t i o n and accep tance of t h e p rocess and p roduc t s a s s o c i a t e d w i t h the r ecove ry of p u l p from c a u s t i c p e e l , p a r t i c u l a r l y on t h e : ( a ) pu lp , ( b ) a c i d i f i c a t i o n , and ( c ) use of o c t a n o i c ( c a p r y l i c ) a c i d .

2. I n d u s t r i a l ( long-term) demonstrat ions on a f u l l - s c a l e p rocess ing b a s i s are needed t o determine: ( a ) t h e p r e t r e a t m e n t ba th s t a b i l i t y and replenishment f requency, ( b ) t h e e x t e n t of peel ing-aid ca r ryove r t o the c a u s t i c b a t h and i n t o t h e p r o d u c t , and ( c ) t h e s a f e t y requirements such as t h e need f o r f low-divers ion of o f f - c o n t r o l material.

3 . Each cannery needs t o determine t h e optimum process f low, equipment, and pu lp use f o r i t s l o c a l s i t u a t i o n .

4 . A r a p i d , f a t t y - a c i d a n a l y s i s should be developed t o f a c i l i t a t e c o n t r o l of t h e o c t a n o i c a c i d ( c a p r y l i c a c i d ) peel ing-aid c o n c e n t r a t i o n i n the , p re t r ea tmen t b a t h t o a i d p rocess c o n t r o l by cannery p roduc t ion personnel .

5

SECTION 4

MATERIALS AND CONTROL INSTRUMENTS

Tomatoes--In both yea r s t he tomatoes were f i e l d run as used by t h e canne r i e s . There w a s no s e l e c t i o n f o r exper imenta l use; i t was f e l t t h a t any s e l e c t i n g would b u i l d i n b i a s , and such s e l e c t i o n would no t be r e a d i l y i d e n t i f i a b l e . i t i s t h e extremes of tomato peela- b i l i t y t h a t sets t h e c o n d i t i o n s r a t h e r than the average tomato. Tomato p e e l a b i l i t y was judged us ing 10-lb samples taken from each run of 2,000 l b s . In 1975, t h e cannery processed the v a r i e t y VF-145 almost s o l e l y . In 1976, t h e v a r i e t y w a s u s u a l l y t h e UC-134, w i th o c c a s i o n a l v a r i e t i e s 198 and VF-145. S ince a c o n t r o l run w a s made each day, t h e comparisons i n pe'eling were based on pee l ing v a r i a b l e s , e l i m i n a t i n g t h e need t o cons ide r t h e tomato v a r i e t y , h a r v e s t pe r iod , o r growing l o c a t i o n .

I n a pee l ing ope ra t ion

Sodium Hydroxide--The t t caus t i c ' l (50% w/w sodium hydroxide aqueous so lu- t i o n ; a l s o c a l l e d c a u s t i c soda o r l y e ) used by c a n n e r i e s and i n the p i l o t pee l ing s t u d i e s w a s a s t anda rd food grade manufactured by t h e e l e c t r o l y t i c diaphragm process . Cur ren t ly , t h e c h l o r - a l k a l i i n d u s t r y g e n e r a l l y uses an a s b e s t o s diaphragm t o produce the sodium hydroxide. A d i s c u s s i o n on a s b e s t o s w i t h respect t o t h e c h l o r a l k a l i i n d u s t r y and i t s products was presented i n 1975 (35) .

Proposed r u l e s have been publ ished by t h e Food and Drug Adminis t ra t ion r ega rd ing a s b e s t o s f i b e r s i n foods (6,7). n e i t h e r conc lus ions about t h e medical s i g n i f i c a n c e of i n g e s t e d a s b e s t o s f i b e r s nor r e g u l a t i o n s promulgated on t h i s s u b j e c t .

However, as y e t t h e r e have been

Limited ana lyses were made i n both y e a r s t o determine the a s b e s t o s con ten t i n t h e recovered p u l p , i n t h e c a u s t i c b a t h , and on f i e ld - run tomatoes be fo re and a f t e r washing. Although washing reduced t h e q u a n t i t y of so i l -borne a s b e s t o s on t h e whole tomatoes, a s b e s t o s f i b e r s were found i n the recovered pulp. The l e v e l s were about t h e same as have been repor- t ed a s background i n C a l i f o r n i a d r ink ing waters. Resu l t s from t h e l i m i t e d number of a n a l y s e s i n d i c a t e t h a t the major c o n t r i b u t i n g source of a s b e s t o s i s f i e l d s o i l , no t t h e c a u s t i c bath.

The e l e c t r o l y t i c mercury c e l l w a s former ly used by t h e c h l o r - a l k a l i i n d u s t r y , bu t c a u s t i c soda from t h i s process i s no l o n g e r g e n e r a l l y a v a i l a b l e . There i s a newer c a u s t i c product ion process which u t i l i z e s an ion-exchange

so produced i s a l s o no t g e n e r a l l y a v a i l a b l e (8) . .membrane, hence avoid ing t h e use of e i t h e r mercury o r a s b e s t o s , bu t m a t e r i a l

Hydrochlor ic Acid--In both y e a r s , t h e hydroch lo r i c a c i d w a s a s t anda rd commercially a v a i l a b l e food grade 22" Baume (35.21% w/w H C 1 , 9.84 l b / g a l ) .

6

In 1975 i t was r ece ived from a bu lk t r u c k and s t o r e d i n a 500 g a l p l a s t i c t ank provided wi th a ca lc ium carbonate scrubber t o c o n t r o l ac id fumes.

Pee l ing Aids--These were commercially a v a i l a b l e sodium 2-ethylhexyl s u l f a t e (40% aqueous s o l u t i o n ) , sodium mono- and di-methyl naphtha lene su l fo - n a t e s ( 4 0 % aqueous s o l u t i o n ) , a p r o p r i e t a r y mix tu re of C5 t o Cg s a t u r a t e d f a t t y a c i d s w i t h an odd number of carbons (Faspee l , BASF Wyandotte Corp., Wyandotte, Michigan) , hexanoic a c i d ( c a p r o i c a c i d , 99%), and oc tano ic a c i d ( c a p r y l i c a c i d , 92%). Faspee l i s a v a i l a b l e o n l y from t h e one source ; a l l t h e o t h e r s have m u l t i p l e sou rces and are s o l d under a v a r i e t y of t r a d e names.

P e e l pH Recording Control ler--This Leeds and Northrup (North Wales, PA) pH equipment w a s a s t anda rd commercially a v a i l a b l e in s t rumen t , o r i g i n - a l l y purchased i n 1969, and used wi thout m o d i f i c a t i o n o t h e r t han t o r e p l a c e e l e c t r o d e s . It c o n s i s t e d of Leeds and Northrup Type No. 992-820-0925-6- 008-485 having a Model R r e c o r d e r , S e r i e s 80 e lec t ro-pneumat ic c o n t r o l l e r w i t h a pH 0 t o 10 range and 3 t o 15 p s i g o u t p u t , and used an E l e c t r o d e Assembly No. 7782 c o n t a i n i n g Measuring E lec t rode No. 117089, Reference E l e c t r o d e No. 117106, and Temperature Compensator No. 352145. These u n i t s were s u i t a b l e f o r tomato pulp a t tempera tures ranging from 80 t o 212°F.

F i n a l Pu lp pH Recorder--Same type of u n i t a s t h a t used f o r Peel pH - Recording C o n t r o l l e r .

Incoming Peel pH Recorder--Prior t o a c i d i f i c a t i o n and i r r e s p e c t i v e of t h e p l a c e of a c i d i f i c a t i o n , t h e incoming c a u s t i c p e e l w a s monitored by a Beckman ( F u l l e r t o n , CA) Type No. 8710-2-04-4-1-0-0-1 Recorder w i th a pH 4 t o 14 range and us ing a pH E lec t rode S t a t i o n Model No. 300-0-1-03-1-2-1-0, con ta in ing a No. 636460 Remote Ampl i f ie r -Transmi t te r , No. 19033 Reference E l e c t r o d e , No. 19505 Measuring E l e c t r o d e , and a No. 19586 Temperature Com- pensa to r .

Labora tory pH Meter--Corning (Corning S c i e n t i f i c Ins t ruments Co., Medford, MA) Model 475010 bench-type i n d i c a t i n g meter w i t h a pH 0 t o 14 range and having a Beckman Combination E l e c t r o d e No. 476051 and Corning Automatic Temperature Compensator No. 476097.

Acid Con t ro l Valve--Acid a d d i t i o n w a s modulated by a Research Cont ro l Valve (Research Cont ro l CO., Tulsa , OK) Type 75HB (Has ta l loy B) wi th a 1/4- - - i n . body, a n o r i f i c e of Cv = 0.30 equal pe rcen tage , and wi th a pneumatic a c t u a t o r f o r 3 t o 15 p s i g s i g n a l from t h e pH Recording C o n t r o l l e r , a i r - to - open.

Hot-Break Temperature Controller--A s t a n d a r d thermocouple type i n s t r u - ment and pneumatic a c t u a t e d steam modulat ing v a l v e were used. c o n t r o l l e r was a Honeywell ( P h i l a d e l p h i a , PA) No. Y152P(13)-PH-96-K1-(13) wi th a 0 t o 300°F range , 3 t o 15 p s i g pneumatic o u t p u t , and tempera ture sens ing wi th a Honeywell No. 2TlM13G6-5 Type T copper cons t an tan shea thed tiiermocouple. reset , but w i th t h e r e l a t i v e l y l a r g e volume of l i q u i d t o be h e a t e d , t h e p r o p o r t i o n a l band was q u i t e adequate wi thout reset.

The r eco rd ing

The c o n t r o l l e r w a s equipped w i t h both p r o p o r t i o n a l band and

7

Pre t r ea tmen t Temperature Controller--Same as t h e Hot Break Temperature C o n t r o l l e r .

Lye App l i ca to r Temperature Controller--Same as t h e Hot Break Temperature C o n t r o l l e r .

8

SECTION 5

EXPERIMENTAL PROCEDURES

1975 EXPERIMENTATION--PEEL PROCESSIIJG AND PULP CHARACTERIZATION

A f low diagram of t h e 1975 cannery peel-pulp recovery s y s t e m i s shown i n F igure 2. P e e l w a s expe r imen ta l ly processed on a d a i l y b a s i s dur ing 1975 us ing p e e l as r ece ived from convent iona l c a u s t i c pee l ing a t t h e T i l l i e L e w i s Foods, P l a n t W , Ant ioch, C a l i f o r n i a . This cannery processed VF-145 tomatoes through washing and s o r t i n g , then about 40 t / h r were d i v e r t e d t o t h e i r pee l ing ope ra t ion . The d i v e r t e d tomatoes were nex t immersed i n a c a u s t i c ba th ; t h i s was a t y p i c a l i n d u s t r i a l s i t u a t i o n us ing 10-12% w/w sodium hydroxide with up to,. but no t exceeding , 0.2% w/w sodium 2-ethylhexyl s u l f a t e a t 200-210°F and wi th a nominal h a l f - m i n u t e immersion. From t h i s b a t h t h e tomatoes went i n t o two types of mechanical pee l removers, a f l a t -bed d i s c type fol lowed by pee l - t a g removal r o l l s (FMC PR-20 Tomato P e e l Remover, 1 machine; FMC Corpora t ion , San J o s e , C a l i f o r n i a ) o r ro t a ry -cy l inde r , rubber d i s c types (Magnuson Model C Peel Scrubbers , 4 machines; Magnuson Engineers , Inc . , San Jose , Cali- f o r n i a ) . c e n t r a l screw conveyor which i n t u r n emptied i n t o a r e c e i v i n g tank. A t t h i s tank t h e pee l ings were picked up by a c e n t r i f u g a l pump and s e n t through a 3-in. s t a i n l e s s t ube a d i s t a n c e of 200 f t t o a n o u t s i d e yard where t h e exper imenta l p rocess equipment w a s l oca t ed . A t t h i s yard the pee l ings passed i n t o t h e exper imenta l p rocess system (F igure 3) o r i n t o t h e cannery waste- pee l tank. In g e n e r a l , t h e exper imenta l system u t i l i z e d peel pumped d i r e c t l y from normal cannery pee l ing o p e r a t i o n s , and r ece ived t h i s about 5.4 minutes a f t e r t he c l e a n tomatoes f i r s t e n t e r e d the c a u s t i c a p p l i c a t o r . This pee l was "normal" material r a t h e r t han c l o s e l y c o n t r o l l e d l a b o r a t o r y samples.

All of t h e s e p e e l removers d ischarged the tomato pee l ings i n t o a

The primary exper imenta l v a r i a b l e s i n the pulp recovery system were: (1) t h e e x t r a c t o r s c reen s i z e and paddle c l e a r a n c e , (2) p l a c e of a c i d i f i - c a t i o n , e i t h e r be fo re o r a f t e r f r a c t i o n a t i o n of pu lp from the s k i n and misce l laneous seeds and f i b e r s , (3 ) hot-break tempera ture , (4) l a g t i m e between t h e h o t break and canning, ( 5 ) evapora to r tempera ture and degree of pu lp-so l ids c o n c e n t r a t i o n , and ( 6 ) t h e hea t -process ing time of cans. These v a r i a b l e s were eva lua ted i n terms o f : ( 1 ) pu lp y i e l d , ( 2 ) product q u a l i t y , and (3) tomato S tandards of I d e n t i t y .

Peel w a s r ece ived cont inuous ly a t 10-30 gpm, and a c i d i f i e d wi th food- grade hydroch lo r i c a c i d e i t h e r immediately i n t h e Pee l Tank (48 g a l pu lp volume, F igure 4 ) o r l a t e r i n the Hot-Break Vessel (250 g a l pulp volume, F igure 5 ) ; t h i s a c i d i f i c a t i o n was cont inuous ly c o n t r o l l e d by an au tomat ic pH record ing c o n t r o l l e r . Peel flowed cont inuous ly i n t o each of t h e s e v e s s e l s and c o n s t a n t volumes were maintained by overf low weirs. A tramp- metal t r a p (F igu re 6 ) w a s used t o p r o t e c t t h e pumps and o t h e r equipment.

9

CONVENTIONAL PROCESSES EXPERIMENTAL PROCESS I t l 1

FIELD RUN TOMATOES

PUREE PEELING

c-. 0

WASH

I I J(

SORT

CRUSH

WASH

SORT

$0

t CAUSTIC DIP@ ACID

= PEELINGS (ACIDIFICATION)

@ I 0 0

HOT BREAK PEEL REMOVAL

EXTRACTOR -SKIN lo

INSPECT t

PULP

t CANNING

f t

t

FINISH

CONCENTRATE

CANNING

@ =SAMPLE POINT

PULP f HOT BREAK (HEATING)

I 3. 0 J.

CAN 0 J.

CONCENTRATE

I HEAT

P R O'C E S S

0 COOL

F i g u r e 2. 1975 p rocess flow diagram.

f

u

11

PEEL pH RECORD

(SUBMERGED INLET) Assye PEEL RECEIVED 19" HT.

/ I / \

BAFFLE EXTENDS TO TANK I BOTTOM

(-PEEL &I CONTROLLER ELECTRODE ASSY.

/ PEEL TANK

ACID DIFFUSER m 33%" I.D. X 361/2" HT. (1" ABOVE AGITATOR 141 GAL. GROSS VOL.

10" O.D. (1" OFF BOTTOM)

350 rpm

LEVEL) AGITATOR, 48 GAL. OPERATING VOL.

Figure 4. Peel tank, 1975.

U

STEAM COIL, 69 rpm 24" COIL OD, 1.5'' OD TUBE, 23 TUBE TURNS, TWO 4" x 84" PADDLES ON COIL OD, 55 s q ft HEATING SURFACE COIL DRIVE, 3 hp STEAM FLOW CONTROLLED AUTOMATICALLY BY PULP TEMPERATURE

.

CONDENSATE OUT

Figure 5 . Hot-break vessel, 1975.

1 3

SHELL 6" 0 . 0 6 2 " w

IN 2 " ACME SANITARY 1

FERRULE -=-&

DIA. x ALL, x 24" LEN.

TYPE 3 0 4 S.S.

1 OUT

F i g u r e 6 . Tramp metal t r a p , 1975.

14

A Hot-Break Vessel ( F i g u r e 5 ) w a s provided t o i n a c t i v a t e enzymes t h a t might be p r e s e n t and t o reduce subsequent m i c r o b i o l o g i c a l growth by avoiding hold ing a t t h e incoming 120°F pu lp tempera ture f o r an extended per iod . This hea t ing a l s o provided thermal-exposure t e s t i n g s i n c e c a u s t i c exposed tomato pulp i s more s u s c e p t i b l e t o c o l o r and f l a v o r changes than material which has o n l y been processed a t t h e normal tomato pH of 4.2-4.5.

Next t h e pulp flowed i n t o t h e Pulp Tank f o r a f i n a l check and record- i ng of pH. A material (mass) ba lance w a s made f o r each t r i a l by weighing t h e E x t r a c t o r waste ( p r i m a r i l y s k i n and seeds ) and measuring t h e volume of t h e recovered pulp. Recovery w a s determined wi th 400-1,000 g a l . ba t ches ; t h e weight of t h e recovered pulp and E x t r a c t o r waste was e q u a l t o t h a t of t h e incoming pee l . Recovered p e e l pulp was concen t r a t ed i n 1,000 g a l . ba t ches a t 160-200°F t o c o n c e n t r a t i o n s of 10-20% TS ( t o t a l s o l i d s ) i n the cannery s ing le - s t age vacuum evapora tor .

The pH w a s measured and recorded a t t h r e e p o s i t i o n s i n the process : (1) t h e incoming p e e l pH w a s con t inuous ly recorded , (2 ) t h e a c i d i f i c a t i o n was c o n t r o l l e d and recorded a t t h e p e e l t ank o r o p t i o n a l l y a t t h e h o t b reak , and ( 3 ) t h e f i n a l pulp w a s con t inuous ly recorded. The a c i d d i f f u s e r i n t h e p e e l tank w a s a 1/2-in. Schedule 80 p l a s t i c (Kynar) p ipe d r i l l e d wi th 1 4 h o l e s , 0.062-in. d iameter on 1/2-in. c e n t e r s . Th i s a c i d d i f f u s e r w a s posi- t i o n e d as shown i n F igure 4. Mixing w a s q u i t e v i o l e n t a t t h e 350 rpm a g i t a t o r speed , and t h e a l k a l i n e p e e l reached pH 4.2 w i t h i n an e s t i m a t e d f i v e seconds of e n t e r i n g t h e mixing p o r t i o n of t h e tank . The d i f f u s e r f o r t h e Hot Break Tank had 16 h o l e s , 0.062-in. d iameter on 2.75-in. c e n t e r s , and w a s pos i t i oned a t t h e i n l e t end of t h e t ank , p a r a l l e l t o t h e c o i l a x i s ; t h e pH e l e c t r o d e assembly w a s on t h e o u t l e t end.

Both f r e s h and canned samples were made up f o r subsequent ana lyses . A l l canned samples were hand f i l l e d i n t o s i z e 211 x 400 unenameled c a n s , s e a l e d wi th a double seamer, h e a t processed i n b o i l i n g water f o r 40 minutes , and cooled t o 100°F i n 75°F water. on a 100% recovered-pulp b a s i s without b lending i n t o o t h e r tomato m a t e r i a l s .

These canned samples were ana lyzed and judged

1976 LABORATORY STUDY ON PEELING AIDS

The 1976 l a b o r a t o r y expe r imen ta t ion w a s p r i m a r i l y d i r e c t e d towards so l - v ing t h e pee l ing-a id r e s i d u e problem which w a s i d e n t i f i e d du r ing t h e 1975 pulp-recovery exper imenta t ion . In t h e s p r i n g , l a b o r a t o r y p e e l i n g tests were conducted on tomatoes us ing about 70 compounds, i n c l u d i n g many s u r f a c t a n t s ( s u r f a c e - a c t i v e a g e n t s ) , t o determine t h e chemical s t r u c t u r e t h a t b e s t a i d e d pee l ing . The we t t ing a c t i o n ( i n t e r f a c i a l t e n s i o n ) of t h e p o t e n t i a l pee l ing a i d s w a s checked, but sur face-wet t ing a c t i o n a lone was found t o provide l i t t l e a s s i s t a n c e i n s e l e c t i n g pee l ing a i d s because enhancement of pee l ing seemed t o be p r i m a r i l y due t o chemical a c t i v i t y . P o t e n t i a l pee l ing a i d s were a p p l i e d i n two ways: ( 1 ) d i r e c t l y i n t h e c a u s t i c b a t h i n t h e t r a d i - t i o n a l - manner, i n t he c a u s t i c enough pee l ing e f f e c t i v e l y i n

and ( 2 ) - a s a pre t rea tment p r i o r t o immersing t h e tomatoes ba th . The purpose of t h e p re t r ea tmen t w a s t o apply on ly a i d t o permeate t h e s k i n and assist t h e c a u s t i c t o ac t more the c a u s t i c a p p l i c a t o r . It w a s a l s o assumed that the

15

optimum tempera ture and immersion t i m e f o r apply ing t h e pee l ing a i d might d i f f e r from those used f o r t h e c a u s t i c a p p l i c a t i o n .

1976 PILOT SCALE MODIFIED CAUSTIC PEELING

Modified c a u s t i c pee l ing i s t h e term used t o i n d i c a t e t h e a p p l i c a t i o n of t h e pee l ing a i d as a p re t r ea tmen t p r i o r t o immersion of t h e tomatoes i n t o c a u s t i c ( F i g u r e 7) . The b e s t pee l ing c o n d i t i o n s found i n t h e l a b o r a t o r y tes ts were inco rpora t ed i n a l - t / h r p i l o t l i n e a t Hunt-Wesson Foods, P l a n t A , Hayward, C a l i f o r n i a du r ing t h e 1976 tomato process ing season. This l i n e ope ra t ed on t h e r e g u l a r cannery tomatoes, u s u a l l y Var i e ty UC-134. F i n a l washing, s o r t i n g , and pee l ing were c a r r i e d out s o l e l y on t h e p i l o t equipment. Pee l ing w a s performed con t inuous ly , t y p i c a l l y i n 45 minute r u n s , wi th samples t aken du r ing s t eady- s t a t e cond i t ions .

This Hayward cannery r ece ived tomatoes u s u a l l y i n bu lk 20-t l o a d s ( t r a c - t o r w i t h two trailers) as i s t y p i c a l f o r C a l i f o r n i a canners . The tomatoes were removed from the t rucks by t h e cannery personnel through a water wash- out .and c a r r i e d by a flume i n t o a sump; from t h e sump, they were e l e v a t e d ou t and s p r a y washed, passed over a sc reen t o remove g r o s s t r a s h and toma- t o e s less than 1.2-in. i n d iameter and t h e n flumed. P r i o r t o f u r t h e r cannery washing and s o r t i n g , p a r t of t h e tomatoes were d i v e r t e d from t h i s flume t o t h e p i l o t - p e e l i n g l i n e .

I n t h e exper imenta l system these tomatoes were immersed i n wa te r , e leva- t e d o u t , and passed over a l - f t x 10-f t rubbe r d i s c f l a t -bed scrubber having water sp rays (10 gpm t o t a l ) ; t h i s w a s t h e f i n a l washing. The tomatoes were then passed over a s o r t i n g b e l t f o r hand s o r t i n g ; t h e degree of hand s o r t i n g was v a r i e d t o compare mold counts i n the recovered pulp. The pre t rea tment immersion w a s i n a 17-in. x 10- f t t rough having a paddle t y p e , p o s i t i v e d i s - placement conveyor which c o n t r o l l e d t h e immersion t i m e . Immersion t i m e could be v a r i e d from 15 seconds t o t h r e e minutes . The hea ted s o l u t i o n w a s r ec i r cu - l a t e d from e n t r y t o e x i t a t about 2O-gpm, and w a s c o n t r o l l e d and v a r i e d from 75°F t o 200"F, depending on t h e experiment. From t h i s p r e t r e a t m e n t , t h e tomatoes were removed on an open-mesh e l e v a t o r f o r a v a r i a b l e d r a i n i n g t i m e of 10-seconds t o 2 minutes . A f t e r d r a i n i n g , t h e tomatoes dropped i n t o t h e Caus t i c App l i ca to r f o r a 10-sec t o 2-min immersion t i m e i n 11% (w/w) sodium hydroxide a t 210°F. A commercial a p p l i c a t o r , such as t h e FMC Hi-Ton Tomato P e e l e r , h a s a d r a i n per iod of about 50% of t h e immersion t ime, which n o t o n l y removes excess c a u s t i c s o l u t i o n but provides a f u r t h e r pe r iod f o r t h e c a u s t i c t o act on t h e tomato. The p i l o t c a u s t i c a p p l i c a t o r d i d no t have a s i m i l a r d r a i n per iod so t h i s w a s s imula ted by a va r i ab le - speed , open-mesh b e l t normal ly he ld t o 11 seconds r e s idence t i m e . Tomatoes then passed over r o t a t i n g s l i t t i n g b l ades and onto a 12-in. x 10-f t set of f l a t -bed rubber-disc pee l removers which were ope ra t ed -wi thou t water s p r a y s t o provide und i lu t ed pee l . This uni t w a s t h e same as that used f o r washing and had d i s c s of 4.25-in. diameter, spaced 0.9-in. a p a r t , on 3-in. c e n t e r s , and t u r n i n g a t 425 RPM i n t h e d i r e c t i o n of t h e tomato t r a v e l ; t h e bed w a s p i t ched upward lO-in./lO-ft i n t h e d i r e c t i o n of . t h e tomato t r a v e l which gave a nominal tomato r e s idence t i m e of 30 seconds. This d ry removal of p e e l i s i n c r e a s i n g l y being p r a c t i c e d commercially.

16

c

WASH

MATERIAL

SORT PR ETREATM ENT - L

BALANCE

HOLD SLIT PEELED TOMATOES (pdt) 85.0% I

SKIN (waste) 0.6% - 14.4%

100.0%

PEEL PULP (product)

v I}- PEELINGS

Figure 7. Modified-caustic peeling, 1976.

Peel dropped onto a f u l l - l e n g t h pan and flowed down t o a 10-gal. p o t where t h e p e e l w a s a c i d i f i e d , t hen sepa ra t ed i n t o s k i n and pu lp f r a c t i o n s wi th a Langsenkamp Indiana Laboratory Pulper (Langsenkamp Inc . , I n d i a n a p o l i s , Ind iana ) equipped w i t h a 0.033-in. sc reen . f i l l e d a t 115-190°F i n t o 211 x 400 enameled c a n s , p rocessed f o r 45 minutes i n b o i l i n g water, and cooled t o about 100°F i n 75°F water. For a m a t e r i a l ba lance on each t r i a l , both t h e recovered pulp and pee led tomatoes were weighed, t y p i c a l l y 1,000 t o 2,000 l b / t r i a l .

Th i s recovered pulp w a s hot

A t y p i c a l set of exper iments would invo lve a l t e r i n g one v a r i a b l e , such a s p re t r ea tmen t tempera ture , r e s idence t i m e , pee l ing-a id c o n c e n t r a t i o n , o r t he type of pee l ing a i d . The f i r s t run would be w i t h p l a i n c a u s t i c preceded by a p re t r ea tmen t , f o r example, a t 150"F, 0.5 minute immersion i n t h e pre- t r ea tmen t b a t h , wi thout pee l ing a i d . The weight pe rcen t of peeled tomatoes was c a l c u l a t e d from t h e tomatoes i n a 10-lb sample which had a t least 99% of t h e p e e l removed. The pan under the rubber d i s c s would c a t c h t h e p e e l which would be swept i n t o a pot and a c i d i f i e d every 4 t o 8 minutes wi th hydroch lo r i c a c i d . This a c i d i f i c a t i o n t i m e corresponded t o t h e de l ay between p e e l removal and a c i d i f i c a t i o n exper ienced i n 1975. lb /h ' r , t h e r e was i n s u f f i c i e n t p e e l t o s c reen con t inuous ly ; t h e r e f o r e , t h e a c i d i f i e d p e e l w a s accumulated u n t i l t h e end of a run , t hen weighed and put batchwise through t h e f i n i s h e r t o s e p a r a t e recovered p e e l pulp from t h e s k i n and misce l laneous seeds and f i b e r . The 0.5 i n c h c l e a r a n c e used i n 1975 when process ing cont inuous ly w a s inadequate wi th t h e s m a l l ba tches . Therefore , a 3/32-in. c l e a r a n c e was used; even so , t h e 1976 pomace was wetter than i n 1975.

When pee l ing a t 2,000

SAMPLE LOCATIONS

1975 S t a t i o n s

Samples of tomato materials were c o l l e c t e d a t s e v e r a l l o c a t i o n s (Fig- ure 2 ) i n bo th t h e commercial and exper imenta l p rocesses du r ing each of t h e test runs. These l o c a t i o n s were similar f o r bo th 1975 and 1976.

S t a t i o n l--Peel r e s i d u a l s were sampled a t t h e p e e l t ank preceding t h e e x t r a c t o r . du r ing t h e middle , and toward t h e end of each test run. w a s made of t h e s e a l i q u o t s i n l -quar t p l a s t i c c o n t a i n e r s . I n a l l cases, samples c o l l e c t e d a t t h i s s t a t i o n were ob ta ined p r i o r t o a c i d i f i c a t i o n .

A l iquo t s of approximate ly 300 m l were c o l l e c t e d a t t h e beginning , A composite sample

S t a t i o n 2--Recovered pulp samples were c o l l e c t e d a t t h e d i scha rge from t h e e x t r a c t o r i n t h e same manner desc r ibed above. When a c i d i f i c a t i o n of t h e pulp w a s conducted a f t e r e x t r a c t i o n , samples c o l l e c t e d a t t h i s p o i n t were a l k a l i n e ; when a c i d i f i c a t i o n was conducted b e f o r e e x t r a c t i o n , t h e samples were a c i d i c .

_ _ S t a t i o n 3--Acidified and hea ted pulp was sampled from t h e pulp t a n k

Al iquo t s of 400 t o 500 m l were c o l l e c t e d about fo l lowing t h e h o t break. 1/4 hour a f t e r s t eady- s t a t e c o n d i t i o n s were achieved and toward the end of each run. These a l i q u o t s were composited and cooled i n l -qua r t p l a s t i c

18

c o n t a i n e r s . These samples were i d e n t i f i e d as "Sample 3." When a d d i t i o n a l t es t c o n d i t i o n s were imposed (such as c o n c e n t r a t i n g , b lending , o r h o l d i n g ) , a d d i t i o n a l s i n g l e samples of approximate ly one l i t e r were ob ta ined and i d e n t i f i e d by an a l p h a b e t i c a l s u f f i x (e.g. , 3A, 3B, e t c . ) .

S t a t i o n 4--Recovered pulp w a s canned a t t h e end of each tes t run. The ho t pu lp w a s ob ta ined from t h e pu lp t ank fo l lowing t h e h o t b reak , p laced i n t o 211 x 400 un l ined c a n s , s e a l e d and h e a t processed by immersion i n b o i l i n g water (100°C) f o r 40 minutes . (23°C) water. When a d d i t i o n a l tes t c o n d i t i o n s were imposed, as desc r ibed above, a d d i t i o n a l cans of material were preserved i n a l i k e manner. Each set of cans w a s a s s igned an a p p r o p r i a t e code. t h e a d d i t i o n a l samples were a s s igned a l p h a b e t i c a l s u f f i x e s (4A, 4B, e t c . ) .

The cans were cooled by immersion i n c o l d

However, f o r a n a l y t i c a l purposes ,

S t a t i o n 5--Samples of tomato s k i n and seeds e j e c t e d by t h e e x t r a c t o r were c o l l e c t e d i n p l a s t i c bags. Approximately 100 t o 200 g of material were c o l l e c t e d a t t h e beginning , dur ing t h e middle , and toward the end of each run. These p o r t i o n s were composited f o r l a b o r a t o r y a n a l y s i s .

* S t a t i o n 6--Whole tomatoes e n t e r i n g t h e conven t iona l c a u s t i c a p p l i c a t o r s ( b a t h s ) were sampled. beginning and a t t h e end of each tes t run. The two p o r t i o n s were composited i n p l a s t i c bags f o r l a b o r a t o r y a n a l y s i s .

About 8 t o 12 tomatoes were randomly picked a t t h e

S t a t i o n 7--Peeled tomatoes e x i t i n g t h e d i s c p e e l e r s were sampled. About 8 t o 12 tomatoes were randomly picked from t h e v a r i o u s u n i t s a t t h e beginning and end of each run; t h e two p o r t i o n s were composited i n p l a s t i c bags.

S t a t i o n 8--Juice d ischarged from t h e conven t iona l f i n i s h e r s was co l - l e c t e d dur ing t h e middle and a t t h e end of each run. The 450 t o 500 m l a l i q u o t s were composited and cooled i n 1-quart p l a s t i c c o n t a i n e r s .

S t a t i o n 9--Conventionally prepared tomato p a s t e was sampled about 1/2 hour a f t e r each tes t run. bags. When o t h e r conven t iona l ly prepared tomato p roduc t s , such as j u i c e o r s auce , w a s used t o blend wi th t h e recovered p u l p , a d d i t i o n a l samples were obta ined . The l a t t e r materials were i d e n t i f i e d by a n a l p h a b e t i c a l s u f f i x . Appropr ia te codes were a l s o a s s igned t o cans of t h e s e materials.

About 300 g o f material were c o l l e c t e d i n p l a s t i c

S t a t i o n 10--Pomace from the convent iona l p u l p e r s w a s c o l l e c t e d i n plas- Each sample c o n s i s t e d of 100 t o 200-g p o r t i o n s which were c o l l e c - t i c bags.

t e d dur ing t h e middle and toward t h e end of each tes t run .

A l l uncanned samples were h e l d on ice dur ing t h e composi t ing pe r iod , as w e l l as du r ing t r a n s p o r t from- t h e test s i te t o t h e l a b o r a t o r y . Upon d e l i v e r y t o t h e l a b o r a t o r y , t h e samples were immediately p laced under r e f r i g e r a t i o n (4°C). Analyses were performed as qu ick ly t h e r e a f t e r as p r a c t i c a b l e .

_ _ Samples which were c o l l e c t e d f o r a s c o r b i c a c i d (Vitamin C) determina-

t i o n s (dichlorophenolindophenol method) were immediately weighed (20 g) and mixed w i t h a s o l u t i o n of metaphosphoric - g l a c i a l acetic a c i d . The a c i d i f i e d samples were he ld on ice u n t i l d e l i v e r y t o t h e l a b o r a t o r y . These samples

19

were then f rozen u n t i l a n a l y s i s could be performed. Samples c o l l e c t e d f o r B-carotene (Vitamin A) de t e rmina t ions and p r o t e i n a n a l y s i s were a l s o i ced u n t i l d e l i v e r y and f rozen i n t h e l a b o r a t o r y p r i o r t o a n a l y s i s .

The canned samples were cooled a t t h e test s i t e , t r a n s p o r t e d t o t h e l a b o r a t o r y , and he ld under r e f r i g e r a t i o n (4°C). This p recau t iona ry mea- s u r e w a s t aken t o prec lude s p o i l a g e , a concern due t o t h e u n c e r t a i n t y of adequate process ing a t 100°C.

1976 S t a t i o n s

The 1976 sample p o s i t i o n s corresponded t o those i n 1975. Recovered p e e l pu lp w a s canned as a s i n g l e s t r e n g t h , a c i d i f i e d p u l p , t hen hea t proces sed a f t e r s e a l i n g . A l l samples were taken from the p i l o t l i n e , none from t h e cannery. For i n s t a n c e , t h e f r e s h , washed tomatoes came from t h e p i l o t s o r t i n g b e l t which corresponded t o t h e 1975 S t a t i o n 6 , and so f o r t h . Some samples , such as t h e c a u s t i c b a t h , were from a similar s t a t i o n a s i n 1975, but of a d i f f e r e n t character. For i n s t a n c e , t h e c a u s t i c i n 1976 had t o be changed between each t r i a l t o e l i m i n a t e p r i o r materials a f f e c t i n g subsequent tests; t h e r e f o r e , t h e 1976 c a u s t i c w a s " f r e sh" and t h e 1975 c a u s t i c w a s "mellowed", a p o i n t which would n o t show up based on c a u s t i c con ten t . A "water dip" was used t o cushion t h e f a l l of t h e tomatoes a s t h e y came o f f t h e d i s c p e e l e r , and served t o r i n s e t h e tomatoes b e f o r e they were e l e v a t e d i n t o b a r r e l s f o r weighing. Since t h i s was n o t a t y p i c a l cannery b a t h o r f lume, s a m p l e s would n o t have been r e p r e s e n t a t i v e of a commercial s i t u a t ion .

ANALYTICAL METHODS

I n bo th y e a r s t h e c o l l e c t e d samples were ana lyzed f o r parameters con- s i d e r e d most s i g n i f i c a n t f o r t h e r e s p e c t i v e sampling l o c a t i o n . Emphasis w a s p laced on o b t a i n i n g da ta r e l a t i v e t o t h e q u a l i t y of t h e recovered pulp. The s i g n i f i c a n c e and major parameters eva lua ted f o r each sampling l o c a t i o n are i d e n t i f i e d below. Most of t h e s e a n a l y s e s were conducted on f rozen and canned samples a t t h e NFPA, Berkeley and t h e WRRC, Albany l a b o r a t o r i e s . Fresh material w a s ana lyzed i n t h e l a b o r a t o r y t ra i le r a t t h e exper imenta l s i te. c o l o r s , s a l t , pH, and a l k a l i n i t y , c a r r i e d out on t h e incoming pee l and a c i d i - f i e d pulp ; i n 1976, t h e s e ana lyses were NTSS, pH, a l k a l i n i t y ( f o r a c i d r equ i r emen t ) , p e e l i n g e f f i c i e n c y , l y e c o n c e n t r a t i o n , and serum v i s c o s i t y . The purpose w a s t o provide guidance f o r t h e exper imenta l p rocess ing because t h e Berkeley and Albany l a b o r a t o r y d a t a would no t be a v a i l a b l e u n t i l a f t e r t h e exper imenta l per iod . Where t h e r e w a s d u p l i c a t i o n of d a t a from t h e f i e l d and r e s e a r c h l a b s , t h e . c o r r e l a t i o n w a s good. Add i t iona l d e t a i l s per- t a i n i n g t o t h e a n a l y t i c a l procedures may be found i n t h e r e f e r e n c e s c i t e d .

F i e l d a n a l y s e s du r ing 1975 were p r i m a r i l y Agtron (M500-A) and Munsell

@--The pH of a l l samples w a s measured t o de te rmine the r e l a t i v e a c i d i t y o r b a s i c i t y of each. S ince t h e pH of s o l u t i o n s g r e a t l y i n f l u e n c e s t h e r e s i s t a n c e of microorganisms t o h e a t , as w e l l as t h e i r a b i l i t y t o grow, t h e F e d e r a l Food and Drug Adminis t ra t ion has a r b i t r a r i l y e s t a b l i s h e d pH 4.6 a s t h e va lue d i f f e r e n t i a t i n g low-acid products from high-acid commodities.

20

Thermal process ing r e g u l a t i o n s have been promulgated f o r low-acid foods ( 9 ) . The n a t u r a l pH of raw tomatoes processed i n C a l i f o r n i a normally f a l l pH 4.2 and 4.4.

Measurements were made e l e c t r o m e t r i c a l l y by d i r e c t i n s e r t i o n of a combinat ion e l e c t r o d e i n t o f l u i d sample. The pH of semi-dry pomace/skin samples was ob ta ined by adding 2 t o 3 p a r t s ( b y weight ) of water t o 1 p a r t of sample, s t i r r i n g , and measuring a f t e r e q u i l i b r i u m had a p p a r e n t l y been a t t a i n e d (about 30 minutes) . measurement . Whole tomatoes were homogenized p r i o r t o pH

T o t a l S o l i d s (TS)--Since most commercial tomato products are concentra- t e d t o va ry ing degrees , t h e amount of moi s tu re p r e s e n t i n tomato p u l p i s of i n t e r e s t . A d d i t i o n a l l y , t h e amount of moi s tu re p re sen t i n tomato pomace may serve as an index of t h e o p e r a t i n g e f f i c i e n c y of p u l p e r s and f i n i s h e r s which are used t o e x t r a c t pulp ( j u i c e ) from crushed tomatoes. Moisture was determined by d ry ing a n a p p r o p r i a t e weight of s a m p l e , based on a n approximation of t h e s o l i d s percentage i n t h e sample, i n a vacuum oven (29 inches ) f o r 4 hours a t 70°C. T o t a l s o l i d s were t h e n c a l c u l a t e d and expyessed as "percent d r y weight" (10). A s t a b u l a t e d , t h e t o t a l s o l i d s d a t a inc lude s a l t .

Na tu ra l Tomato So lub le S o l i d s (NTSS)--Estimation of t h e t o t a l s o l i d s and s p e c i f i c g r a v i t y of tomato products may be ob ta ined by measuring t h e r e f r a c - t i v e index ( B r i x ) of t h e tomato serum (11) . Na tu ra l tomato s o l u b l e s o l i d s are a l s o t h e b a s i s f o r e s t a b l i s h i n g United S t a t e s S tandards f o r Grades of tomato products . The re fo re , r e f r a c t i v e index i s commonly used by t h e i n d u s t r y i n q u a l i t y c o n t r o l . Direct r ead ings a t 25°C were taken f o r most of t h e samples c o l l e c t e d dur ing the s tudy. Serum from samples con ta in ing h i g h e r s o l i d s percentages w a s ob ta ined by c e n t r i f u g a t i o n . A l l a c i d i f i e d samples were c o r r e c t e d f o r s a l t ; r e s u l t s are expressed as "percent sucrose."

S a l t (Sodium Chloride)--Sal t i s a commonly used seasoning f o r many tomato products . S ince sodium c h l o r i d e i s formed by n e u t r a l i z a t i o n of sodium hydroxide wi th hydroch lo r i c a c i d , t h e q u a n t i t y of s a l t i n t h e recovered tomato pu lp w a s o f i n t e r e s t . T o t a l c h l o r i d e s were measured by po ten t iome t r i c t i t r a t i o n wi th s i lver n i t r a t e and t h e use of a s i lver elec- t r o d e (12) . Labora tory r e s u l t s are expressed a s "percent s a l t (sodium c h l o r i d e . )I1.

A l k a l i n i t y , Total--Total a l k a l i n i t y measurements were conducted t o determine t h e r e l a t i v e q u a n t i t y of r e s i d u a l c a u s t i c (sodium hydroxide) conta ined i n t h e c o l l e c t e d samples. A 5.0 g sample w a s t i t r a t e d wi th 0.1N H2S04 t o an a r b i t r a r i l y s e l e c t e d end-point of pH 4.2.

Cons is tency and Viscosity--The c o n s i s t e n c y of tomato products i s a f f e c - t e d by t h e amount of and e x t e n t of deg rada t ion of p e c t i n , as w e l l a s t h e s i z e , shape and q u a n t i t y of t h i x o t r o p i c and i n s o l u b l e materials conta ined t h e r e i n . The United S t a t e s S tandards f o r Grades of tomato products s p e c i f y l i m i t s f o r t h i s parameter . Therefore , cons i s t ency measurements were made w i t h a Bostwick Consis tometer ; r e s u l t s are expressed i n c e n t i m e t e r s i n 30 seconds (14 ) . V i s c o s i t y measurements, performed on f ree- f low samples , were

21

made by t iming a s p e c i f i e d volume through a c a p i l l a r y tube (15). usage , “cons i s t ency” i s t h e term f o r t h e f lu id - f low r e s i s t a n c e of v i scous foods , such as tomato pulp , w i t h a r e l a t i v e l y g r e a t amount of i n s o l u b l e s o l i d s ; “v i scos i ty1 ‘ i s used f o r t hose f l u i d s wi thou t a p p r e c i a b l e i n s o l u b l e s o l i d s , such as tomato serum.

In g e n e r a l

Samples ( c h i l l e d , t hen f rozen) were checked f o r p o s s i b l e p e c t i n enzyme a c t i v i t y b e f o r e t h e h o t break. t o approximately pH 4.2 e i t h e r : ( b ) a u t o m a t i c a l l y i n t h e p rocess ( b e f o r e t h e hot-break). cooled below 70°F w i t h i n 5 minutes of a c i d i f i c a t i o n , packed i n ice f o r about 3 hours , and s t o r e d a t 0°F u n t i l eva lua ted f o r p e c t i n enzyme a c t i v i t y . In one case t h e process a c i d i f i e d sample w a s h e l d , w i thou t hot-break, f o r 90 minutes a t 100 t o 120°F b e f o r e c h i l l i n g and t h e n s t o r e d c o l d i n t h e manner descr ibed above; t h i s ho ld was t o check s h o r t term c o l o r and mic rob io log ica l s t a b i l i t y .

Samples of a l k a l i n e p e e l pu lp were a c i d i f i e d ( a ) manually i n t h e f i e l d l a b o r a t o r y o r

Then they were

The a c t i v i t y of t h e p e c t i c enzymes i n t h e a c i d i f i e d samples was d e t e r - mined i n 1975 . b y measuring changes i n c o n s i s t e n c y a f t e r mixing t h e tes t samples wi th a h igh cons i s t ency tomato j u i c e , which se rved as a p e c t i n sub- s t ra te . The test sample was added t o t h e s u b s t r a t e a t a r a t i o of l:lO, and t h e cons i s t ency w a s measured a t 25°C over a pe r iod of 1 hour o r more by t h e ef f l ux -p ipe t method.

Fu r the r serum v i s c o s i t y tests were made i n 1976 by n e u t r a l i z i n g t h e c a u s t i c w i t h a c i d be fo re p e e l removal so as t o i s o l a t e v i s c o s i t y changes occur r ing i n t h e c a u s t i c b a t h from those t ak ing p l a c e a f t e rward .

Vitamins--Tomatoes and tomato products are cons ide red t o be s i g n i f i - c a n t s o u r c e s of Vitamin A (B-carotene) and Vitamin C ( a s c o r b i c a c i d ) i n a normal a d u l t d a i l y d i e t . Both of t h e s e n u t r i e n t s can be degraded through chemical t r e a t m e n t , h e a t , and /o r ox ida t ion . S ince t h e recovered pulp w a s s u b j e c t e d t o a l l t h r e e of t h e s e c o n d i t i o n s , t h e v i t a m i n c o n t e n t of t h e f i n a l recovered material was of concern. Vitamin A w a s determined spectrophotome- t r i c a l l y ; r e s u l t s are expressed as ” I n t e r n a t i o n a l u n i t s p e r 100 g” (16). (Appendix A).

The i n i t i a l a n a l y s i s of Vitamin C ( a s c o r b i c a c i d ) w a s made by t h e 2,6-dichlorophenolindophenol v i s u a l t i t r a t i o n method, which i s u n s u i t a b l e i f t h e r e are o t h e r reducing a g e n t s p re sen t o r i f some of t h e Vitamin C act i - v i t y i s due t o dehydroascorb ic a c i d (25). u s u a l l y minimal i n tomato products but o rgan ic reducing subs t ances , c o l l e c - t i v e l y termed r educ tones , are o f t e n formed i n products which have undergone e x t e n s i v e h e a t t r ea tmen t . Such reductones are formed by t h e a c t i o n of a l k a l i on sugar . An a l t e r n a t i v e method t h a t avo ids i n t e r f e r e n c e by i n o r g a n i c reducing a g e n t s and a s s a y s t o t a l Vitamin C by i n c l u d i n g dehydroascorbic a c i d i s t h e method of Roe and co-workers (17). This method invo lves t h e o x i d a t i o n of a s c o r b i c a c i d t o dehydroascorb ic a c i d , subsequent t r ans fo rma t ion of dehydroascorb ic a c i d t o d ike togu lon ic a c i d , and coupl ing of t h i s product wi th 2,4-dinitrophenylhydrazine under c a r e f u l l y c o n t r o l l e d c o n d i t i o n s t o g i v e red-colored osazones. A comparison of t h e c o l o r produced i n samples and

Ino rgan ic reducing a g e n t s are

22

a s c o r b i c a c i d s t a n d a r d s i s used as a means of de te rmining a s c o r b i c a c i d con- t e n t . of 510 t o 520 mu. S ince any reductones p r e s e n t form osazones t h a t absorb i n the r e g i o n of 450 t o 490 mu and these absorb more i n t e n s e l y than the r ed osazone of a s c o r b i c a c i d ( i . e . , d ike togu lon ic a c i d ) , a more a c c u r a t e a s s a y of a s c o r b i c a c i d i n t h e presence of reductones i s ob ta ined by reading absorp- t i o n a t 540 mu r a t h e r than a t 510 t o 520 mu. However, i f reductones are p r e s e n t i n l a r g e amounts, h i g h estimates of a s c o r b i c a c i d w i l l n e v e r t h e l e s s be ob ta ined due t o t h e i n t e r f e r i n g a b s o r p t i o n of t h e reductones ; t h e r e f o r e , a chromatographic s e p a r a t i o n i s r equ i r ed t o s e p a r a t e t h e osazones of a s c o r b i c a c i d from those of t h e reductones b e f o r e making a b s o r p t i o n r ead ings a t 520 mu.

The a b s o r p t i o n o f l i g h t by t h e pigment formed i s maximum a t a range

The u s u a l chromatographic s e p a r a t i o n of osazones by bo th column and th in - l aye r chromatography w a s modif ied t o a s e p a r a t i o n by column chromatography a l o n e , us ing a development s o l v e n t of acet ic a c i d , e t h y l acetate , and methylene c h l o r i d e (3:20:97). a s c o r b i c a c i d added was a l s o assayed by chromatographic i s o l a t i o n and co lo r - metric de te rmina t ion of t h e osazone a t 520 mu.

In a l l cases,a sample wi th a known l e v e l of

* P e e l i n g Aids--Peeling a i d a d d i t i v e s are c a r r i e d o u t of t h e c a u s t i c ba ths by t h e tomatoes. Residues are removed from t h e pee led product dur ing the p e e l removal and wash ing l r in s ing o p e r a t i o n s . peel r e s i d u a l and i n t h e e f f l u e n t wash waters whenever t h e l a t t e r o p e r a t i o n i s performed. Samples c o l l e c t e d from t h e test sys tem were ana lyzed f o r pee l ing a i d s ; s e l e c t e d samples from convent iona l o p e r a t i o n s se rved as con- t r o l s . Concent ra t ions of sodium 2 -e thy lhexy l su l f a t e and sodium mono- and di-methyl naphtha lene s u l f o n a t e s i n a p p r o p r i a t e samples were determined by a methylene-blue dye t r a n s f e r method (Appendix B). were determined by e s t e r i f i c a t i o n of t h e f a t t y a c i d and q u a n t i f i c a t i o n by gas - l iqu id chromatography (GLC) (Appendix C ) .

These r e s i d u e s appear i n t h e

Fa t ty-ac id pee l ing a i d s

Pesticides--The samples were e x t r a c t e d by t h e method i n t h e Food and Drug Admin i s t r a t ion ' s P e s t i c i d e A n a l y t i c a l Manual ( 1 9 ) . The extracts were c leaned through a c t i v a t e d f l o r i s i l . Toxaphene and th iodan were d e t e c t e d i n t h e i r r e s p e c t i v e f l o r i s i l eluates by GLC u s i n g t h e e l ec t ron -cap tu re d e t e c t o r . Pa ra th ion w a s d e t e c t e d by GLC us ing t h e flame photometr ic phosphorus de tec- t o r . A l l p e s t i c i d e a n a l y s e s were performed by Stoner L a b o r a t o r i e s , Santa Clara, C a l i f o r n i a .

Toxaphene i s a complex mixture of compounds manufactured by t h e c h l o r i - n a t i o n of camphene and r e l a t e d compounds. Treatment w i t h base c a u s t i c i n t h e l a b o r a t o r y causes dehydroch lo r ina t ion which a p p e a r s dur ing GLC as a s h i f t t o ear l ie r e l u t i n g compounds ( u s i n g methyl o r phenyl s i l i c o n e columns). similar s h i f t t o earlier e l u t i n g compounds can be seen i n o l d toxaphene residues i n environmental s o i l s ,. and similar s h i f t s were v i s i b l e i n some samples.

A

By vary ing t h e s t r e n g t h of base used du r ing h y d r o l y s i s , s t a n d a r d s were s y n t h e s i z e d w i t h va ry ing degrees of decomposi t ion ( a s evidenced by t h e i r s h i f t t o s h o r t e r r e t e n t i o n t i m e s ) . l i k e t h e (S tone r ) m i l d l y decomposed s t a n d a r d , and some were l i k e t h e (S tone r ) s t r o n g l y decomposed s t anda rd .

The toxaphene i n some of t h e samples w a s

23

Mold and I n s e c t Fragments--The Federa l Food, Drug, and Cosmetic A c t i n Sec t ion 402(a ) (4 ) p rec ludes t h e sale of products which "may have become contaminated wi th f i l t h " , whether o r no t such contaminants may pose hazards t o h e a l t h . n a t u r a l o r unavoidable d e f e c t s i n foods f o r human use where no h e a l t h hazards e x i s t . Mold and i n s e c t f ragments , r e su l - t i ng from f i e l d , t ranspor- t a t i o n o r s t o r a g e c o n d i t i o n s , f a l l i n t o t h i s ca tegory . S ince these exis t l a r g e l y on t h e s u r f a c e of t h e r a w product , t h e r e w a s i n t e r e s t whether t h e pulp recovered from peel r e s i d u a l s might c o n t a i n e x c e s s i v e l y h igh counts of t h e s e contaminants . Randomly s e l e c t e d canned samples were microscop- i c a l l y examined f o r mold and i n s e c t f ragments (20) . Mold i s r epor t ed as pe rcen t of p o s i t i v e microscope f i e l d s ; i n s e c t f ragments are r epor t ed as t o t a l counts of f ragments p e r 200 g. (Note: d e f e c t a c t i o n l e v e l s are e s t a b l i s h e d f o r Drosophila f l y eggs and/or l a r v a e p e r 100 g ) .

"Defect a c t i o n l e v e l s " have been e s t a b l i s h e d by t h e FDA f o r

Bacterial Counts--Tomato pulp samples were taken be fo re and a f t e r t h e ho t b reak , and checked f o r mesophi l ic (3OOC i n c u b a t i o n ) , thermophi l ic (50'C i n c u b a t i o n ) , and t o t a l p l a t e counts (30°C incuba t ion ) . P l a t i n g w a s on g lucose- t ryptone agar . labi ' le than the spo res ( the rmoph i l i c ) so comparing t h e counts can i n d i c a t e s u r v i v a l and r e i n o c u l a t i o n , equipment c l e a n l i n e s s and h e a t process ing adequacy.

Vegeta t ive ce l l s (mesophi l ic ) are more hea t

Qua l i ty Factors--The United S t a t e s S tandards f o r Grades of Canned Tomato Puree (Tomato Pulp) e s t a b l i s h e s t h e c r i te r ia c l a s s i f y i n g t h e q u a l i t y of canned product (21 ) . Fac to r s f o r which s c o r e s are ass igned are c o l o r and d e f e c t s (da rk specks , s e e d s , tomato p e e l , and o t h e r ex t raneous mate- r i a l s ) ; non-scored f a c t o r s are s u b j e c t i v e e v a l u a t i o n of f l a v o r and odor. The t e x t u r e of graded samples are a l s o r o u t i n e l y noted.

The above q u a l i t y f a c t o r s were eva lua ted by i n s p e c t o r s of t h e F r u i t and Vegetable Qua l i ty Div i s ion , Food S a f e t y and Qua l i ty Se rv ice , U.S. Department of A g r i c u l t u r e , S tockton , C a l i f o r n i a . Color s c o r e s were de te r - mined by t h e s p e c i f i e d Munsell co lo r d i s c comparison procedure o r by t h e use of a Hunter co lo r ime te r . Color and d e f e c t s c o r e s are based on a maximum of 50 p o i n t s f o r each f a c t o r . Canned recovered pu lp samples were submi t ted f o r q u a l i t y e v a l u a t i o n . would l a r g e l y determine the commercial a c c e p t a b i l i t y and u t i l i t y of t h e recovered materials. In the l a b t r a i l e r , c o l o r w a s measured wi th t h e Agtron and Munsell i n s t rumen t s dur ing 1975 bu t no t du r ing 1976.

These r e s u l t s were of primary concern s i n c e they

Nitrogen and Amino Acids--Tomato pulp samples were analyzed f o r t o t a l n i t r o g e n c o n t e n t and b a s i c amino a c i d s be fo re and/or a f t e r c e n t r i f u g a t i o n i n t o s o l u b l e and i n s o l u b l e f r a c t i o n s . The two f r a c t i o n s were obta ined by c e n t r i f u g i n g samples a t 35000.G f o r 10 minutes. The i n s o l u b l e s o l i d s were washed twice by re-suspending i n d i s t i l l e d water t o about 1.5 times t h e o r i g i n a l volume and c e n t r i f u g i n g . f r a c t i o n , and the s o l u b l e s were concent ra ted by vacuum d i s t i l l a t i o n a t 45-50"C t o near t h e i r o r i g i n a l volume. In a l l cases t h e a s s a y r e s u l t s f o r a f r a c t i o n ( s o l u b l e o r i n s o l u b l e ) were expressed on t h e b a s i s of t h e whole sample weight equ iva len t . determined by Kje ldah l procedure (22 ) .

The washes were combined wi th t h e s o l u b l e

The t o t a l n i t r o g e n c o n t e n t of each sample w a s On the b a s i s of t h e Kje ldahl r e s u l t s ,

2 4

samples of 0.8 t o 3.2 mg N were hydrolyzed i n 6-N H C 1 (33) . A f t e r t h e H C 1 was thoroughly removed by vacuum d i s t i l l a t i o n a t 45 - 50"Cy t h e sample was concen t r a t ed t o dryness wi th a r o t a r y evapora to r and suspended i n a measured volume of pH 2.2 b u f f e r . Then t h e sample w a s f i l t e r e d and t h e p r o t e i n hydro- l y s a t e w a s ana lyzed f o r amino a c i d s us ing an au tomat ic amino a c i d ana lyze r (Beckman Model 120, Phoenix Model K8000 B y o r Durrum D-500) (23) .

25

SECTION 6

RESULTS AND DISCUSSION

The r e s u l t s from 1975-76 showed that tomato pulp recovered from c a u s t i c p e e l i n g s has food p o t e n t i a l . i n g method, and these r e s u l t s showed t h e n e c e s s i t y of p rocess ing the tomato pulp wi th care s o as t o achieve i t s f u l l p o t e n t i a l . Experimentat ion spanned two yea r s . In 1975, tomato p e e l was t aken d i r e c t l y from a commercial c a u s t i c pee l ing ope ra t ion ; t h i s recovered pulp w a s c h a r a c t e r i z e d as t o i t s c o l o r , g r a d e , and conformity t o t h e S tandards of I d e n t i t y . were made, t hen t r i e d on a p i l o t pee l ing l i n e t o minimize t h e pee l ing-a id r e s i d u a l s found i n the 1975 recovered pulps .

Product g rades v a r i e d accord ing t o t h e process-

I n 1976 p rocess changes

While t h e 1975 r e s u l t s (Table 1 ) showed t h e r e i s food p o t e n t i a l i n recovered pulp , t h e r e w a s one major de t rac t ion- - the p e e l i n g a i d r e s idue a t 150-450 ppm. Of t h e c u r r e n t l y used commercial p e e l i n g a i d s (sodium 2- e t h y l h e x y l s u l f a t e , sodium mono- and di-methyl naphtha lene s u l f o n a t e s , o r f a t t y - a c i d mix tu res con ta in ing predominately odd-numbered ca rbons ) , none seem s u i t a b l e f o r c l e a r a n c e as food a d d i t i v e s . Even i f a n addi t ive-grade p e e l i n g a i d were c u r r e n t l y a v a i l a b l e , t h e 150-450 ppm r e s i d u e i s l a r g e enough t o raise q u e s t i o n s about d e c l a r i n g i t on t h e product l a b e l as an add i t i v e .

While i t i s p o s s i b l e t o p e e l tomatoes wi thout a pee l ing a i d , i t i s g e n e r a l l y acknowledged that h ighe r c a u s t i c c o n c e n t r a t i o n o r i nc reased tem- p e r a t u r e i s r equ i r ed ; t h e s e l e a d t o h ighe r p e e l l o s s e s , and as a r e s u l t , t h e pee led tomato q u a l i t y s u f f e r s s i n c e t h e v a s c u l a r v e i n s become more pronounced. less than t h a t found i n 1975, but i t w a s cons ide red improbable t o reduce t h e r e s i d u e t o n e a r ze ro once a pee l ing a i d w a s i n t roduced i n t o t h e c a u s t i c pee l ing system. The re fo re , a modif ied c a u s t i c pee l ing w a s developed i n 1976 by us ing food g rade chemicals as pee l ing a i d s and app ly ing them as a p r e c a u s t i c t rea tment i n s t e a d of adding d i r e c t l y t o t h e c a u s t i c ba th .

The pee l ing a i d r e s idue l e v e l p o s s i b l y could be reduced t o

In normal cannery o p e r a t i o n s , t h e j u i c e and p u l p s u p p l i e s are i n t e r - connected so t h a t t h e s e materials can be shunted between t h e d i f f e r e n t sou rces and u t i l i z a t i o n p o i n t s t o s a t i s f y changing product ion requirements . The re fo re , i n actual cannery p r a c t i c e recovered p e e l pu lp could be combined wi th j u i c e and macerate from o t h e r sou rces be fo re p rocess ing i n t o s t anda rd p roduc t s such as tomato sauce , c a t s u p , f i l l j u i c e f o r whole-canned tomatoes, o r o t h e r s a l t e d products . During a c i d i f i c a t i o n and p o s s i b l y a t t h e rubber- d i s c p e e l removal p o i n t , a small amount of water might be inco rpora t ed i n t o

26

TABLE 1. SUMMARY OF TYPICAL 1975-1976 RECOVERED PEEL PULPS

Typ ica l S ingle-St rength Tomato Pulps

I t e m 1975 1976 Conventional Process ing

--_---I_- (a>--

Recovery of p e e l %w/w

NTSS, ( n a t u r a l tomato s o l u b l e s o l i d s ) , %w/w

S a l t , (sodium c h l o r i d e ) , g/100 gm

T o t a l s o l i d s , ( s a l t f r e e ) , %w/w

Vitamin A , (be ta -caro tene) , I . U . / l O O gm

Vitamin C , ( a s c o r b i c a c i d ) , mg/100 gm

Color g rade , ( p e r puree s t d )

F lavor g rade , ( p e r puree s t d )

Peel ing-aid r e s i d u e , pu lp ppm (c)

I n s e c t i c i d e r e s i d u e , pu lp product , toxaphene ppm ( f )

I n s e c t i c i d e r e s i d u e , s k i n waste, toxaphene ppm

96.7%

5.3

3. - 5.6

665

n i l

A-C

C

150 - 450

0.4

5-60

95%

5. '2

1.1

5.9

--- (b)

n i l

A

A-C

0 - 30

trace

34

n/ a

5.4

0.08

5.71

516

10.7

A

A

0 (d)

trace

7 ( e )

p o s i t i v e amount less than 0.08 ppm. n o t a p p l i c a b l e (no c u r r e n t commercial recovery) . i n d u s t r y 4-yr ave rages , except s a l t which i s 2-yr average. no t analyzed. sodium 2-ethylhexyl s u l f a t e i n 1975, o c t a n o i c a c i d i n 1976. no pee l ing a i d used i n conven t iona l j u i c i n g / p u l p i n g . pomace from j u i c i n g , s e e d s wi th p r o p o r t i o n a l l y less s k i n than i n peel-pulp recovery. t o l e r a n c e is 7.0 ppm i n canned and f r e s h tomatoes

27

t h e pee l . This water must be removed, e i t h e r th rough subsequent concentra- t i o n such as f o r tomato sauce , o r dur ing t h e evapora t ion t h a t occurs from hold ing t anks . w i th o t h e r pu lps . There seems l i t t l e p rocess ing j u s t i f i c a t i o n f o r keeping recovered pulp i s o l a t e d f o r use i n a s p e c i a l product s i n c e t h e r e i s a n i n s u f f i c i e n t q u a n t i t y of r ecove rab le pu lp t o ma in ta in a s e p a r a t e proces- s i n g l i n e .

This water could be removed e i t h e r b e f o r e o r a f t e r combining

The v a r i o u s process and product a s p e c t s are d i scussed below, inc lud ing the u n i t o p e r a t i o n s , recovered pulp character is t ics , and economic and regula- t o r y c o n s i d e r a t i o n s .

Washing and Sorting--Peel pulp recovered du r ing t h e 1975 season from t h e t y p i c a l cannery pee l ing o p e r a t i o n ( T i l l i e Lewis Foods, P l a n t W) had low mold, i n s e c t f ragment , and b a c t e r i a l counts t h a t were w e l l w i t h i n r e g u l a t o r y t o l e r a n c e s . This showed t h a t t h e cannery had a n e x c e l l e n t washing and s o r t - i n g system c o n s i s t i n g of counter -cur ren t water f low and f i n e s p r a y s , a l l w i th a r e l a t i v e l y low t o t a l water usage of 750 g a l / t o n of tomatoes f o r t h e e n t i r e p l a n t . Tomato washing c o n s i s t e d of t h e primary dump t a n k s , a secon- d a r y f lume, a t h i r d f lume, and a f i n a l f resh-water r i n s e as t h e tomatoes passed over r o l l e r conveyors. Water w a s c h l o r i n a t e d t o 5 ppm. I n 1976 tomatoes were rece ived b e f o r e commercial p rocess ing and washed i n t h e p i l o t systems; t h e f i n a l r i n s e over rubber -d iscs corresponded t o the prev ious y e a r ' s u se of r o l l e r s . S o r t i n g i n 1976 was v a r i e d from z e r o t o 20% of t h e pee led tomato weight ; t h e h ighe r s o r t i n g w a s necessa ry when the C a l i f o r n i a S t a t e Grade C e r t i f i c a t e showed 3% mold. While t h e Grade C e r t i f i c a t e i s an i n d i c a t i o n of mold on in-coming raw produc t , t h e tomatoes were graded up t o 24 hours p r i o r , s o t h e a c t u a l mold count could have been h ighe r a t t h e t i m e of expe r imen ta l p rocess ing . An a l t e r n a t i v e t o hand s o r t i n g i s t h e use of h igh-pressure water s p r a y s (70-120 p s i g ) as p r a c t i c e d f o r a number of yea r s by most canne r s t o remove broken and moldy tomatoes.

Washing and s o r t i n g methods t o remove contaminants from raw commodities va ry between canne r i e s . o r unavoidable d e f e c t s " i n tomato p roduc t s , such as mold, r o t , i n s e c t s , etc. , i s publ i shed p e r i o d i c a l l y by FDA (30).

A gu ide t o the t o l e r a n c e s f o r t h e so c a l l e d " n a t u r a l

P e e l i n g a g e n t , w e t t i n g agen t ) i s used by a l l commercial c a n n e r i e s i n t h e c a u s t i c a p p l i c a t o r ( b a t h ) . The purpose of t h e p e e l i n g a i d i s t o promote uniform pee l removal. Without i t , ye l low shouldered areas on t h e tomato tend no t t o be peeled. While a c a u s t i c pee l ing s o l u t i o n a l o n e may p e e l s a t i s f a c - t o r i l y on occas ion , t h e r e are t i m e s when changing t h e tempera ture , immersion t i m e , o r c a u s t i c s t r e n g t h i s not s u f f i c i e n t t o e f f e c t q u a l i t y pee l ing . P a r t i c u l a r l y a t such t i m e s , t h e a d d i t i o n of a pee l ing a i d can improve p e e l i n g i n a r a t h e r empir ical manner. I f t h e tomato i s g iven a prolonged submergence i n t h e c a u s t i c o r i f t h e c a u s t i c c o n c e n t r a t i o n i s i n c r e a s e d , t h e pee l ing l o s s e s rise and t h e v a s c u l a r (wh i t e ) v e i n s of t h e towato become more prominent. g r e a t e r l o s s . VF-145 p rocess ing tomato v a r i e t y which accoun t s f o r perhaps 60% of t h e p rocess ing tomatoes grown i n t h e U . S . A .

Aids--A pee l ing a i d ( a l s o c a l l e d s u r f a c t a n t , su r f ace -ac t ive

The r e s u l t i s a poorer q u a l i t y product and These comments p e r t a i n more t o t h e r e l a t i v e l y "tough skinned"

There are v a r i o u s m a t e r i a l s

28

permi t t ed as washing o r pee l ing a i d s (261, but none of t h e s e are permi t ted a s a d d i t i v e s i n tomato products . The i r use is pe rmi t t ed w i t h t h e p rov i s ion t h a t a f t e r l e a v i n g t h e c a u s t i c a p p l i c a t o r , t h e tomatoes w i l l be washed wi th water, and t h e r e w i l l be n e g l i g i b l e pee l ing a i d remaining on t h e whole tomato. The permi t ted a i d s are water s o l u b l e ; hence , water i s t h e conven- t i o n a l means of removal.

Sodium 2-ethylhexyl s u l f a t e (Emersal 6465; Emery I n d u s t r i e s Co., C i n c i n n a t i , Ohio) was used a t t h e cannery du r ing 1975. t a t i o n showed t h a t sodium mono- and di-methyl naphtha lene s u l f o n a t e s and f a t t y a c i d s responded s i m i l a r l y w i t h r e s p e c t t o r e s i d u e s i n t h e recovered pulp . The s e n s i t i v i t y of t h e a n a l y t i c a l method f o r sodium 2-ethylhexyl s u l f a t e i s about 25-50 ppm because n a t u r a l tomato c o n s t i t u e n t s i n t e r f e r e s l i g h t l y wi th t h e a n a l y s i s . The r a t i o of pee l ing a i d t o sodium i n t h e c a u s t i c a p p l i c a t o r was about t h e same as t h a t found i n t h e recovered p e e l pulp. The l e v e l s of p e e l i n g a i d i n t h e p e e l pulp were u s u a l l y i n t h e range of 150-450 ppm; such l e v e l s are n o t a c c e p t a b l e f o r tomato products . No p e e l i n g a i d r e s i d u e w a s found on pee led whole tomatoes a f t e r p e e l removal. The d e t e c t i o n l e v e l w a s about 25 ppm f o r sodium 2-ethylhexyl s u l f a t e and 1 ppm f o r f a t t y a c i d s .

Subsequent experimen-

During t h e s p r i n g 1976 l a b o r a t o r y p e e l i n g s t u d y , t h e c6 and C8 s a t u r a t e d , monocarboxylic f a t t y a c i d s were t h e most e f f e c t i v e pee l ing-a ids . Octanoic ( c a p r y l i c ) a c i d w a s t h e p r i n c i p a l one used because i t w a s a s e f f e c t i v e and l e s s v o l a t i l e t h a n hexanoic ac id . It i s commercially a v a i l a b l e i n a food g rade (27 ) a t a p r i c e compe t i t i ve wi th pee l ing a i d s c u r r e n t l y used i n commercial tomato pee l ing . The 150°F p re t r ea tmen t w a s as e f f e c t i v e , o r more s o , as us ing t h e pee l ing a i d d i r e c t l y i n t h e c a u s t i c a p p l i c a t o r . For easy- p e e l i n g tomatoes, such a s those s u i t a b l e f o r steam p e e l i n g , i t w a s p o s s i b l e t o peel wi thout c a u s t i c by us ing a 1 t o 2 min. immersion i n a 150°F aqueous b a t h c o n t a i n i n g 0.2% w/w oc t ano ic a c i d . t h e pee l ing a i d wi th c a u s t i c , t h e r e i s no i n h e r e n t r eason why i t r e q u i r e s t h e same a p p l i c a t i o n tempera ture , pH, and immersion t i m e as t h e c a u s t i c .

While i t may be convenient t o app ly

Pee l ing a i d s are commonly r e f e r r e d t o as "wet t ing agents" , but t h e most e f f e c t i v e ones may do more t h a n reduce t h e i n t e r f a c i a l t e n s i o n between t h e tomato s u r f a c e and t h e c a u s t i c . Some we t t ing a g e n t s , such as sodium o l e a t e o r sodium l a u r y l s u l f a t e , w i l l show high-wetting improvement, bu t t hey w i l l have l i t t l e e f f e c t on pee l ing whether a p p l i e d as a p re t r ea tmen t o r d i r e c t l y i n t h e c a u s t i c ba th . O the r s , such as sodium 2-ethylhexyl s u l f a t e and sodium mono- and di-methyl naphtha lene s u l f o n a t e s , perform b e t t e r when a p p l i e d d i r e c t l y i n t h e c a u s t i c b a t h t h a n when used a s a p re t r ea tmen t . e f f e c t i v e pee l ing a i d s appear t o react chemica l ly and ( o r ) t o d i s r u p t t h e c e l l s t r u c t u r e and a l l o w enzyme a c t i o n . This i s i l l u s t r a t e d by pee l ing tomatoes w i t h o n l y a n a c i d i c aqueous s o l u t i o n of o c t a n o i c a c i d a t 150°F; t h i s i s d i scussed f u r t h e r under "Carboxyl ic Acid Peel ing".

The most

Octanoic a c i d does have a characteristic aroma ( r a n c i d , cheesy ) , and i s used a t up t o about 400 ppm i n s y n t h e t i c b lue cheese. I n s i n g l e s t r e n g t h tomato juice, less than 10 ppm i s i n d i s t i n g u i s h a b l e from p l a i n tomato j u i c e . The f l a v o r t h r e s h o l d i s about 20 ppm, and 50 ppm h a s a f l a v o r i d e n t i f i a b l e as a f a t t y a c i d . This t h r e s h o l d would be h ighe r i n sp i ced sauces . This 20 ppm t h r e s h o l d i s s i g n i f i c a n t l y h ighe r t h a n t h e 10 ppm proposed l e v e l f o r

29

g e n e r a l use i n t h e GRAS a f f i r m a t i o n under good manufactur ing p r a c t i c e as a d i r e c t food i n g r e d i e n t as publ i shed i n t h e June 1977 Fede ra l Reg i s t e r ( 2 8 ) . People d i f f e r i n t h e i r t h re sho ld s e n s i t i v i t y t o c a p r y l i c a c i d , but i n ano the r s tudy , 19 ppm w a s found t o be t h e odor t h r e s h o l d f o r a normal person t o c a p r y l i c a c i d i n bu f fe red water a t pH 4.8 (32) .

Carboxyl ic Acid Peeling--The c a r b o x y l i c a c i d p e e l i n g w a s accomplished w i t h a 150°F aqueous s o l u t i o n con ta in ing 0.2% o c t a n o i c ( c a p r y l i c ) a c i d a t about pH 3.6 and wi th a one t o t h r e e minute immersion. peeled t h e tomato var ie t ies Trop ic , Walter, Roma-VF, and VF-145-21-4 (con- t a i n s a uniform-ripening gene) . For t h e VF-145B-7879, UC-134, 198, and 13L , which are t y p i c a l C a l i f o r n i a p rocess ing tomatoes, t h e s k i n w a s loosened and p e e l i n g a i d e d , but a subsequent c a u s t i c a p p l i c a t i o n w a s g e n e r a l l y needed. The pee l ing l o s s averaged about 5% wi th o c t a n o i c a c i d a s compared t o 1 2 % f o r c a u s t i c us ing commercial pee l ing a i d s . d rama t i c because c a u s t i c p e e l w a s r e d due t o t h e adhe r ing p u l p , whereas t h e oc t ano ic a c i d pee l w a s a t r a n s l u c e n t , p a l e ye l low because no pulp adhered. Other secondary t r e a t m e n t s t han c a u s t i c were a tmospher ic steam (30 sec . ) and 900°F supe rhea ted steam (7 sec . ) . Both steam t r e a t m e n t s provide addi- t i on21 peel loosening c a p a b i l i t y , p a r t i c u l a r l y t h e 900 "F steam which s p l i t s t h e s k i n and makes p e e l removal easier.

Th i s completely

The d i f f e r e n c e w a s v i s u a l l y

While o c t a n o i c a c i d performed b e s t among t h e c a n d i d a t e s as a pee l ing a g e n t , a l l t h e C4 t o C8 s a t u r a t e d monocarboxylic a c i d s showed t h e most promise. T ime w a s l i m i t e d and an e x t e n s i v e p u r s u i t of t h e i d e a l p e e l i n g agen t o r a i d was n o t f e a s i b l e . Octanoic a c i d occurs n a t u r a l l y i n coconut o i l and b lue cheese , i s r e a d i l y a v a i l a b l e commercially i n a food g r a d e , and i s p r i ced similar t o the c u r r e n t l y used pee l ing a i d s . be b i o l o g i c a l l y metabol ized i n p r e d i c t a b l e f a s h i o n by both humans and an imals o r microorganisms a s s o c i a t e d w i t h man, and o c t a n o i c a c i d f i t s t h i s r equ i r e - ment. This i s c u r r e n t l y being cons idered i n a proposed a f f i r m a t i o n of t h e G U S s t a t u s of c a p r y l i c a c i d (28) . i n Europe, t h e carboxyl ic -ac id p e e l i n g seems t o be p o t e n t i a l l y compe t i t i ve o r an a i d t o steam pee l ing because of pee l ing var ie t ies such a s t h e San Marzano and Roma (31) . The use of oc t ano ic a c i d n o t o n l y could improve p e e l removal, but i t could reduce t h e d u r a t i o n of steam exposure and h e a t which s o f t e n s t h e tomatoes unduly and i n c r e a s e s p e e l l o s s .

A food-grade pee l ing a i d should

With t h e wide-spread use of steam pee l ing

Pee l ing Aid Pretreatment--During the 1976 t e s t s p re t r ea tmen t tempera- t u r e s were v a r i e d from 75°F t o 210°F. be below enzyme-inact ivat ion temperature . Exper imenta t ion showed t h a t below about 140°F t h e pee l ing a i d p re t r ea tmen t w a s less e f f e c t i v e o r r e q u i r e d long immersion, such a s up t o 10 minutes. Above about 170"F, even w i t h a s h o r t d i p , t h e tomatoes became i n c r e a s i n g l y s o f t and t h e p e e l l o s s i nc reased . O v e r a l l , 150°F w a s b e s t , w i t h . t h e 140°F t o 160°F range be ing p r a c t i c a l . Even a 150°F water (100%) p re t r ea tmen t u s u a l l y showed some p e e l i n g improvement, but use of a pee l ing a i d was d e f i n i t e l y b e t t e r .

I n i t i a l l y , 150°F w a s chosen so a s t o

_ _ When a p re t r ea tmen t i s used , f a t t y a c i d s o f f e r a p o t e n t i a l advantage

over sodium 2-ethylhexyl s u l f a t e (SEHS) and sodium mono- and di-methyl naphth lene s u l f o n a t e s (SNS) because t h e y tend t o loosen t h e tomato s k i n whi le i n an aqueous s o l u t i o n as d i scussed under "Carboxyl ic Acid Peel ing".

30

The l i m i t e d d a t a and v i s u a l obse rva t ion i n d i c a t e b e t t e r pee l ing when hexanoic ( c a p r o i c ) and o c t a n o i c ( c a p r y l i c ) a c i d s were used a s a p re t r ea tmen t t han when used d i r e c t l y i n t h e c a u s t i c a p p l i c a t o r . When t h e pee l ing a i d i s used d i r ec - t l y i n t h e c a u s t i c a p p l i c a t o r , t hen a l l f o u r of t h e s e pee l ing a i d s were about e q u a l l y e f f e c t i v e on an a c t i v e i n g r e d i e n t s b a s i s . A s commercially s o l d , t h e f a t t y a c i d pee l ing a i d s c o n t a i n 100% a c t i v e i n g r e d i e n t s , and t h e SEHS and SNS c o n t a i n 50% as t h e s e l a t t e r ones are d i s t r i b u t e d as water s o l u t i o n s . Although a l l pee l ing a i d s were used s i n g u l a r l y i n t h i s expe r imen ta t ion , mix tu res of f a t t y a c i d s and o t h e r chemicals may o f f e r a d d i t i o n a l pee l ing b e n e f i t s , and f u r t h e r s tudy would be b e n e f i c i a l . One example i s t h a t oc t ano ic a c i d has a l i m i t e d s o l u b i l i t y of 0.12% i n water a t 150"F, and t h i s l e v e l can be inc reased by t h e a d d i t i o n of a c e t i c a c i d which w i l l ac t a s a co-solvent . The o b j e c t of t h i s work w a s t o f i n d a food-grade peeli .ng a i d and a p p l i c a t i o n method t o o b t a i n t h e f u l l b e n e f i t s of a pee l ing a i d and t o minimize r e s i d u a l s i n t h e recovered pulp. Hence, t h e d a t a were no t n e c e s s a r i l y o f a n a t u r e t o d i f f e r - e n t i a t e r e l a t i v e e f f e c t i v e n e s s of c u r r e n t l y used pee l ing a i d s .

Modif ied-Caus t ic Peeling--The term "Modified Caus t i c Pee l ing" i s used t o i n d i c a t e t h e tomato p re t r ea tmen t w i th a pee l ing a i d p r i o r t o the c a u s t i c a p p l i c a t o r i n s t e a d of t h e s t anda rd commercial p r a c t i c e of p u t t i n g pee l ing a i d i n the c a u s t i c ba th .

The 1976 cannery p i l o t pee l ing was most ly wi th t h e tomato v a r i e t y UC-134 T h i s v a r i e t y i s a l s o cons idered a t least a s d i f f i c u l t t o peel as t h e more p reva len t VF-145-7879. When t h e VF-145, 198, and 1 3 L were pee led , t h e y responded s i m i l a r l y t o that of t h e UC-134 wi th r e s p e c t t o pee l ing a i d pre- t r ea tmen t e f f i c i e n c y and r e s i d u e i n t h e recovered pulps .

because i t w a s u s u a l l y t h e o n l y tomato a v a i l a b l e a t t h e cannery.

When comparing pee l ing methods wi th a p i l o t l i n e , i t i s p o s s i b l e t o s i m u l a t e commercial c o n d i t i o n s b u t n e a r l y imposs ib le t o s imula t e a l l a s p e c t s of t h e a c t u a l scale. t h e load. Dup l i ca t ing c a u s t i c s o l u t i o n i s more t h a n similar tempera ture and c a u s t i c c o n c e n t r a t i o n s because t h e usua l cannery s o l u t i o n t a k e s about one week t o r each e q u i l i b r i u m between c a u s t i c and d i s i n t e g r a t e d tomato s o l i d s . E i t h e r t h e i n d u s t r y c o l l e c t i v e l y , o r each p rocesso r i n d i v i d u a l l y , w i l l need t o c o n s i d e r long term process f a c t o r s such as: ( a ) p re t r ea tmen t ba th s t a b i l - i t y and replenishment f requency , ( b ) pee l ing a i d ca r ryove r t o t h e c a u s t i c b a t h and t h e p e e l i n g a i d ( o c t a n o i c a c i d ) l e v e l i n t h e recovered p u l p , and ( c ) s a f e t y f e a t u r e s such as t h e need of f low d i v e r s i o n f o r o f f - c o n t r o l material.

Tomatoes change wi th each t r u c k load and even w i t h i n

P e e l Removal--Any p e e l removal system can be used t o supp ly a pulp recovery system i f t h e recovered pulp i s n o t d i l u t e d wi th water . Water s p r a y s may e x i s t on p e e l removal systems e i t h e r t o provide l u b r i c a t i o n , r i n s e p e e l from t h e equipment, o r t o remove pee l from t h e tomato. I f t h e water added t o t h e p e e l i s i n c i d e n t a l , such as 1% of t h e p e e l weight , t h e n t h i s amount probably would n o t be s i g n i f i c a n t i f i t i s removed dur ing fur - t h e r p rocess ing o r by normal evapora t ion from ho ld ing tanks . FMC PR-20 Tomato Pee l Remover and the Magnuson Model C Pee l Scrubbers sup- p l i e d p e e l f o r t h e 1975 recovery. I n t h e FMC remover, t h e p e e l i s removed i n two s t a g e s ; t h e f i r s t s t a g e i s a h o r i z o n t a l bed of rubber d i s c s , and the second i s a f l a t bed of "pinch" r o l l e r s . I n t h i s case, p e e l was t aken on ly

Both t h e

31

from the rubber d i s c s e c t i o n because the r o l l s e c t i o n had water s p r a y s . In t h e Magnuson, t h e p e e l comes o f f i n a one-stage r o t a r y cage , d i s c u n i t . Both machines can provide recoverable p e e l i n a product ion s i t u a t i o n , and t h e choice between t h e s e o r o t h e r machines would seem t o be a matter of i n d i v i d u a l preference .

A f l a t - b e d d i s c u n i t was used i n t h e 1976 p i l o t pee l ing tests. The peeler w a s q u i t e s e n s i t i v e t o t h e degree of l oad ing because p e e l removal depends n o t only on t h e d i s c s c o n t a c t i n g t h e tomato but a l s o on t h e i n t e r - tomato c o n t a c t and rubbing. With a 1-f t wide p i l o t peeler loaded a t 1- t /hr of tomatoes, t h e r e w a s not s u f f i c i e n t in te r - tomato c o n t a c t f o r optimum p e e l removal. An 8-in. width would have been more a p p r o p r i a t e , bu t t h e width would have in t roduced ano the r v a r i a b l e and w a s t h e r e f o r e kept a t a cons t an t 12-in. f o r a l l t r ia l s . When the f l a t -bed type i s used commercially, i t i s o f t e n used i n combination wi th "pinch" r o l l s as on t h e MC u n i t ; t h e p i l o t sys t em would have b e n e f i t e d from such "pinch" r o l l s .

P e e l Flow--In 1975 t h e equipment w a s i n i t i a l l y ope ra t ed a t 20-30 gpm, which w a s t h e f u l l f low coming from t h e cannery. Although t h e f u l l f low coulh be handled by t h e exper imenta l equipment u n i t s , s u r g e s i n t h e f low taxed the hea t ing c a p a c i t y of t h e hot break t o the l i m i t of t h e a v a i l a b l e steam p r e s s u r e ( 4 5 ps ig ) . d i scharged i n t o the p e e l t roughs , c r e a t i n g an a c i d demand t h a t exceeded the a c i d f low c a p a c i t y ; t h e c a u s t i c overflow w a s a l o c a l c o n d i t i o n which could n o t be modif ied a t t h e t i m e . Subsequent ly , p e e l f low i n t o the p e e l t ank was c o n t r o l l e d t o about 15 gpm by i n s t a l l i n g a 1-inch a n g l e va lve a t t h e p e e l tank. This va lve c o n t r o l l e d the p e e l f low reasonably w e l l , reduced t h e e f f e c t of t h e c a u s t i c overf low, and provided more s t a b l e hea t ing and pH c o n t r o l . However, tomato s k i n o c c a s i o n a l l y c logged t h e v a l v e po r t . These f low stoppages were c o r r e c t e d by i n s t a l l i n g a posi t ive-displacement pump (Waukesha 55 DO, 130-520 rpm variable-speed d r i v e , Waukesha Foundry Co., Waukesha, Wisconsin) t o meter i n t h e p e e l material. Later, t h e c a u s t i c ca r ryove r i n t o the p e e l rose t o the e q u i v a l e n t of 3% sal t ; t o avoid exces- s i v e a c i d consumption, t h e p e e l f low was reduced t o about 10 gpm.

Also, overflows from t h e c a u s t i c a p p l i c a t o r s were

The 1976 system pee l dropped from the rubber d i s c s onto an underlaying pan. about eve ry 4 t o 8 minutes. tomato immersion i n t h e c a u s t i c a p p l i c a t o r c a t i o n were similar t o 1975. The 1976 o p e r a t i o n s imula ted a normal pee l ing ope ra t ion and d i d no t have t o contend wi th t h e unreasonable c a u s t i c v a r i a t i o n s experienced i n 1975. The c o n t r a s t between t h e s e two y e a r s se rved t o emphasize the product ion c o n t r o l requi red .

This p e e l w a s t h e n manually scraped i n t o t h e a c i d i f i c a t i o n c o n t a i n e r P e e l f low w a s t y p i c a l l y 0.4 gpm. The t i m e s from

t o p e e l removal, and t o a c i d i f i -

P e e l Alkalinity--The d a i l y (1975) measured a c i d use i s shown i n Table 2 , and l a b o r a t o r y pH a d j u s t e d a l k a l i n e ( c a u s t i c ) pu lps are shown i n F igure 8. This provides guidance f o r e s t ima t ing a c i d requirements which are expressed a s pounds of a c i d used per pound of tomato s o l i d s (w/w). a p p l i c a t o r s had no t been piped t o overf low i n t o t h e p e e l , t h e s a l t i n the recovered a c i d i f i e d p e e l pu lp would have been about 1 .1% as i n 1976. The present t r e n d among p rocesso r s i s t o r e c y c l e any over f low a s m a k e q t o t h e

I f t h e c a u s t i c

32

0 0 c

.2 5 1 PEEL F R O M 1975 CANNERY PEELING OPERATION, INITIALLY AT pH 12.8

COMMERCIALLY C A N N E D T O M A T O PUREE INITALLY ADJUSTED T O pH 12.5

.o * 0 5 M M 0 14 13 12 11 10 9 8 7 6 5 4

Figure 8 . Acid required to reduce pH of caustic p e e l and Pulp.

33

a p p l i c a t o r s a f t e r s e p a r a t i n g suspended s o l i d s , and t o empty t h e c a u s t i c a p p l i c a t o r s less f r e q u e n t l y than once per week.

Acid i f ica t ion- -Ear ly and r a p i d a c i d i f i c a t i o n i s necessa ry because t h e tomato c h a r a c t e r i s more s t a b l e a t t h e n a t u r a l pH 4.2 than a t pH 11-12. A t t h e h igh pH bo th c o l o r and f l a v o r d e t e r i o r a t e w i t h t i m e and tempera ture , though mic rob io log ica l growth i s i n h i b i t e d . a r a p i d dec rease , i n less than 10 seconds, from pH 11 t o 4.2 i s necessary because an o f f odor was sometimes d e t e c t e d when t h e a c i d i f i c a t i o n paused a t pH 6-10 f o r s e v e r a l minutes .

Once a c i d i f i c a t i o n commences,

A c i d i f i c a t i o n t i m e f o r t h e incoming p e e l was e s t i m a t e d t o be 5-10 seconds t o reach pH 4.2 i n t h e pee l t ank , and 30 seconds when a c i d i f i c a t i o n was i n t h e h o t break v e s s e l . I f t h e p e e l was al lowed t o s t a n d between approximate ly pH 6 t o 10 f o r about 30 minutes , p a r t i c u l a r l y above 100"F, o f f odor ( s u l f u r y ) was pronounced; t h e odor seemed most o b j e c t i o n a b l e a t about pH 9. improved below pH 5. r ece ived and h e l d a t pH 12 g e n e r a l l y had a b e t t e r c o l o r t han i f reduced and he ld a t pH 7-10.

Color i n c r e a s i n g l y darkened from pH 10 down t o about pH 7 , t hen Below pH 5 , t h e c o l o r w a s good down t o pH 2. Pee l

A c i d i f i c a t i o n can be performed e i t h e r b e f o r e o r a f t e r t h e s k i n i s s e p a r a t e d from t h e pulp. l i t t l e r eason t o be concerned wi th a c i d economy by a c i d i f y i n g a f t e r t he s k i n removal, a l t hough both were t r i e d . Th i s l e a v e s t h e p rocesso r t h e freedom of u l t i m a t e l y s e p a r a t i n g pulp and seeds e i t h e r i n an i n d i v i d u a l machine o r combining t h i s s e p a r a t i o n wi th o t h e r pu lp ing o p e r a t i o n s i n t h e cannery. For g e n e r a l pH c o n t r o l , ease of o p e r a t i o n , and product q u a l i t y , a c i d i f y i n g i n t h e p e e l tank w a s b e s t . diagram (F igure 4 ) w a s s u i t a b l e f o r pH c o n t r o l a t f lows up t o 20 gpm.

S ince p u l p recovery was 96% o r b e t t e r , t h e r e w a s

The t ank c o n f i g u r a t i o n shown i n t h e

There i s a d e f i n i t e p re fe rence f o r a c i d i f y i n g t h e pulp b e f o r e h e a t i n g s i n c e pu lp he ld i n t h e a l k a l i n e s ta te i s more s u s c e p t i b l e t o thermal d i s - c o l o r a t i o n (browning). There was no s i g n i f i c a n t recovery d i f f e r e n c e i n product o r e x t r a c t o r o p e r a t i o n whether t h e p e e l w a s e x t r a c t e d i n an alka- l i n e o r a c i d cond i t ion .

S a l t (Sodium Chlor ide) - -Acid i f ica t ion of t h e 1976 c a u s t i c p e e l r e s u l t e d i n about 1.1% s a l t i n t h e recovered p u l p (Table 6 ) . Th i s sa l t c o n t e n t i s s i m i l a r t o t h a t found i n tomato sauces . R a w whole ( u n s a l t e d ) tomatoes c o n t a i n 0.08% w / w s a l t ; canned pee led whole tomatoes, 0.4%; canned tomato j u i c e , up t o 0.8%; c a t s u p , 2.7%; and s p e c i a l s auces , such as c h i l i , c o c k t a i l , and p i z z a , up t o 3% s a l t .

The amount of s a l t i s a r e f l e c t i o n of t h e c a u s t i c i n t h e pee l . A s pre- v i o u s l y exp la ined i n t h i s r e p o r t , t h e ( h i g h ) 3% sa l t i n 1975 (Table 2) was a unique, a t y p i c a l c o n d i t i o n due t o the c a u s t i c b a t h overf lowing i n t o t h e peel. The re fo re , i t i s t h e nominal 1.1% sal t which needs t o be cons idered when u t i l i z i n g recovered pu lp both a s a source of p u l p and s a l t . t h e s a l t c o n t e n t i n t h e f i n a l p roduct , t h e sa l t from a c i d i f i c a t i o n can be managed i n a number of ways, two of which are: cont inuous ly monitored (ana lyzed) through e i t h e r au tomat i c o r manual t i t r a t i o n

To c o n t r o l

(1 ) t h e sa l t c o n t e n t can be

34

f o r c h l o r i d e o r by s e l e c t i v e i o n e l e c t r o d e f o r sodium, and when blended w i t h conven t iona l u n s a l t e d pu lp material , t h e s a l t normally added t o products can be a d j u s t e d acco rd ing ly , o r ( 2 ) t h e recovered pulp can be blended wi th con- v e n t i o n a l u n s a l t e d pulp s o that t h e sal t c o n t r i b u t i o n w i l l be i n s i g n i f i c a n t , and t h e r e g u l a r s a l t i n g procedure can be used.

Pulp Extraction--The b a s i c pulp e x t r a c t i o n in fo rma t ion w a s ob ta ined i n 1975 on a cont inuous f low b a s i s a t rates which would be similar t o a

TABLE 2. ACIDIFICATION DATA (1975)

Acidi fy ing Pee l pulp Caus t i c Acid Used S a l t i n

(1975) (minutes) (gpm) (% w/w NaOH) g tomato s o l i d s ( % NaC1) Date pe r iod f low App l i ca t ion g 100% H C 1 P e e l pu lp

( a ) ( b )

Sep 03 05 08 0 9 11 16 1 7

a m 19 pm 19

22 a m 23 pm 23

24 25 26 29 30

O c t 0 1 02 03 07

a m 08 pm 08

14 15 16

Avg

180 90

180 120 237 105

135 100

90 114

90 120 222 120 150 225 126 190 22 8 153 114

72 205 115

51

-- --

10.6 10.6

10.0 11.4 11.2 10.6 11.3 10.7

11.3

10.5

10.4 10.5 10.8

--

I

-- I

20. 30.

6.9 16.7 15.5 16.7 17.5

9.6 10.

8 . 8. 7.9 7.7 7.9 7.7

10.1 8.7 8.6

12. 7.9 6. 8.7 9.1

14.5 6.9

11. 11.3

0.19 0.15 0.22 0.17 0.30 0.--

0.34 0.21 0.42 0.34 0.32 0.39 0.41 0.34 0.25 0.27 0.30 0.23 0.29 0.41 0.33 0.28 0.15 0.46 0.51 0.30

--

1.8 1.9 5.4

2.6 3.3 2.6 3.3 3.4 3.0 3.5 3.7 3.0 3.0 3.4 2.6 2.9 5.1 4.4 3.3 2.7 1.7 3.9

3.2

--

-- -

( a ) Average of a l l c a u s t i c a p p l i c a t o r s i n o p e r a t i o n (normal ly 3). ( b ) To b r i n g p u l p t o pH 4.2.

35

I

t commercial ope ra t ion (Table 3 ) . In 1976 the q u a n t i t i e s were too small so e x t r a c t i o n was on a ba tch b a s i s and t h e r e f o r e t h e d a t a were i n a p p r o p r i a t e f o r e v a l u a t i o n of y i e l d s . In 1975 wi th t h e E x t r a c t o r (FMC Model 50; FMC Corpora t ion , San J o s e , C a l i f o r n i a ) pos i t i oned as shown i n F igures 2 and 3, t h e bes t pulp recovery and s k i n e x t r a c t i o n w a s ob ta ined wi th a 0.033-in. s c reen and 0.5-in. paddle-screen c learance . Larger s c r e e n s i z e s (0.060 and 0.125-in.) and small c l ea rance (0.187-in.) a l lowed too many s k i n par t ic les and seed fragments from broken tomatoes t o p a s s through t h e sc reen and remain wi th t h e pulp. Within the 1975 c o n d i t i o n s , r e c o v e r i e s g r e a t e r than about 98% had v i s u a l l y obvious s k i n and seeds going through t h e s c r e e n i n s t e a d of being sepa ra t ed from the pulp. This 0.033-inch sc reen i s t y p i c a l of many cannery ope ra t ions . Normal recovery wi th t h e s e s e t t i n g s averaged 96.8% on a w e t b a s i s (82.7% dry-so l ids b a s i s ) .

The 0.5-in. c l e a r a n c e was necessa ry because c l o s e r c l e a r a n c e s , such as t h e common 0.05-in. cannery p r a c t i c e , ground t h e s k i n and inco rpora t ed i t i n t o t h e pulp. Caus t ic a c t i o n had a l r e a d y loosened t h e tomato ce l l s s o a wider c l ea rance w a s necessary . Skin and seed fragments are undes i r ab le be- c a q e they are graded as phys ica l d e f e c t s i n products ; a l s o , t h e waxy s k i n l a y e r c a r r i e s t h e i n s e c t i c i d e s i n c e t h e i n s e c t i c i d e s are f a t so lub le . Thus, r e j e c t i n g the s k i n i s impor tan t bo th as a grade phys ica l d e f e c t and as an i n s e c t i c i d e r e s i d u e c o n t r o l f o r products. The 1975 r e g u l a t o r y t o l e r a n c e f o r toxaphene w a s 7.0 ppm. toxaphene and t h e s k i n waste had 5-60 ppm.

T y p i c a l l y , t h e recovered pulp conta ined 0.4 ppm

To e l a b o r a t e on the paddle-screen c l e a r a n c e s , 0.5-in. and 0.19-in. Pulp recovery w a s about 96% on a w e t b a s i s w i th t h e 0.5-in. were used.

and 99% wi th t h e 0.19-in. The 99% recovery occurred because the s k i n was comminuted and passed through t h e sc reen w i t h t h e pulp. the t r ia l s w a s t h e r e any tendency f o r t he sc reen t o become clogged a t e i t h e r c l ea rance . The e x t r a c t o r was te -out le t g a t e was open a t a l l times t o minimize the back p r e s s u r e on t h e waste and a l low i t t o pass through wi thout r e s t r i c t i o n . The 0.5-in. c l ea rance has t h e added advantage of g r e a t e r machine l i f e due t o much l e s s machine v i b r a t i o n and less p res su re on t h e screen .

A t no t i m e dur ing

A 750 rpm e x t r a c t o r speed w a s used throughout 1975. This i s a s tandard speed f o r t h e machine, normally g i v i n g good equipment l i f e , and wi th a 96.8% average pulp recovery , t h e r e was no need t o experiment w i th va r ious speeds which would have d e t r a c t e d from more impor tan t exper imenta t ion .

Vacuum Evaporation--In 1975 f o u r 1,000 g a l ba tches of pu lp were con- c e n t r a t e d ; t h r e e were recovered p e e l pu lp and t h e f o u r t h w a s convent iona l cannery j u i c e . temperature i n t h e evapora to r c o i l s and a 15-in Hg vacuum; t h i s was t o o h igh a temperature and darkened the pulp excess ive ly . an 180°F temperature and 20-inch Hg vacuum and gave improved co lo r . Even lower tempera tures should be cons idered because t h e a c i d i f i e d , recovered p e e l i s more a p t t o darken on exposure t o h e a t t han i s t h e convent iona l j u i c e . During 1976 recovered pulp was n o t vacuum concen t r a t ed because i t was f e l t t h a t t h e r e w a s adequate informat ion from t h e p r i o r year.

The f i r s t t r i a l on recovered pulp used a 200°F h e a t i n g

The o t h e r t h r e e runs used

36

TABLE 3. SUMMARY OF 1975 PROCESSING C O N D I T I O N S AND SOLIDS RECOVERY

Pee 1 S o l i d s - Recovery- Date Peeler Flow Pulp E x t r a c t o r Temperature, (F) Wet Dry

(% w/w> ( p p d (gpm) Poin t S i z e ( i n c h ) P e e l Break (%I (%I (1975) NaOH PA Rate Acid. Screen Clear Inc . Hot Basis Basis

- ( c ) __ ( d ) __I_I____ __- ( a 1 (b ) ( i n c h )

9 / 3am 9/5am 9/8am

Pm 9/9am 9/11am

a m Pm

9/16pm 9 /17 9/19am

Pm 9/22pm 9/23am

Pm 9/24am 9/25am 9/26pm 9/29am 9/30am

-- -- -- -- -- -- -- -- 9.98 --

12.85 12.85 10.6 10.6 10.6

9.97 11.40 11.17 10.63 11.27

-- -- -- -- --

1780

1780 1780

1780

993 --

-- -- --

1137 97 7

1535 1280 1206 1510

20.0 30.0

5.45 8.33

16.67 16.7

14.3 16.7 17.5

9.6 10.0

8.0 8.0 7.9 7.7 7.9 7.7

10.1 8.7

--

W e ) HB HB HB HB HB HB HB HB HB

PT PT PT HB HB PT PT HB PT

PT(f)

0.125 0.125 0.125 0.125 0.125 0.060 0.060 0.060 0.060 0.060 0.060 0.060 0.060 0.033 0.033 0.033 0.033 0.033 0.033 0.033

0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.187 0.187 0.187 0.187 0.5 0.5 0.5 0.5 0.5 0.187

0.5 0.187

-- -- -- -- -- -- --

123 122 120 120 129 1 2 7 1 2 7 131 136 1 2 1 120 117 130

-- -- -- -- --

2 00 198 2 00 198 195 200 2 00 201 2 00 199 201 199 2 00 195 200

96.7

98.7 98.1 97.3 97.4 97.1 97.5 98.9 95.7 99.4 99.1 97.4 97.1 96.5 97.1 98.7

98.8

--

98.9

--

85.9

91.6 90.4

85.2 83.9 87.3 94.6 82.2 93.9 91.7 87.0 81.8 69.1 85.0 91.9 88.3 90.1

--

aa. 6

--

( cont inued)

TABLE 3. (cont inued)

S o l i d s Recovery P e e l -

(1975) NaOH PA Rate Acid. Screen Clear Inc . Hot Basis Basis Date Peeler Flow Pulp E x t r a c t o r Temperature? (F) Wet Dry

(% w/w> (ppm) (gpm) Poin t S i ze ( i n c h ) P e e l Break (XI (%I ____ (C> ( d L _ - _ - -______-______- (a) ( b ) ( i n c h )

10/lam 10.67 10/2am -- 10/3am 11.33 10/7am -- 10/8am 10.48

pm 10.48 10/14am 10.44

co a m 10.44 10/15am 10.51 10/16am 10.80

1133 1492 1640

960 1262 1283 1465 1465 1058 1275

8.6 11.3

7.9 6.0 8.7 9.1

12.3 16.6

6.9 11.0

PT(f) PT PT PT PT

PT PT PT PT

HB(e)

0.033 0.033 0.033 0.033 0.033 0.033 0.033 0.033 0.033 0.033

0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5

132

140 141 130 126 112 113 138 137

-- 200 194 201 1 2 7 200 198 193 199 131 137

96.4 96.4 97.1 96.7 96.9 96.8 95.7 96.0 96.6 --

82.5 82.3 84.6 82.4 85.0

82.1 83.3 82.6

--

--

-____ ____ Average, of a l l t r ia ls 97.4 85.9 Average, for t r ia l s with 0.033-inch sc reen and 0.5-inch c l ea rance 96.8 82.7

( a ) PA = Peel ing a i d , sodium 2-ethylhexyl s u l f a t e ( b ) A c i d i f i c a t i o n po in t ( c ) Paddle-screen c l ea rance ( d ) Incoming ( e ) Hot break ( f ) PT = P e e l tank

P r i o r t o the 1975 cannery exper iments , l a b o r a t o r y expe r imen ta t ion w a s undertaken t o de te rmine i f t h e c o l o r darkening , due t o h igh a l k a l i n e condi- t i o n s o r h e a t , occur red i n t h e tomato pigment, t h e non-serum s o l i d s , o r i n t h e serum. I n bo th cases, darkening w a s i n t h e serum. Sepa ra t ions were made of t h e s e t h r e e f r a c t i o n s by c e n t r i f u g i n g and s o l v e n t e x t r a c t i o n s , and t h e f r a c t i o n s were cyc led from pH 4.2 t o 11, down t o pH 2, and r e tu rned t o pH 4.2. They were observed v i s u a l l y f o r s i g n i f i c a n t changes. The pigment f r a c t i o n s ( lycopene and ca ro teno ids ) and s o l i d s f r a c t i o n s had only s l i g h t c o l o r changes. The serum f r a c t i o n s had s u b s t a n t i a l darkening a t pH l e v e l s above 8. Th i s darkening w a s semi- revers ib le (perhaps 95%) , but w i th each a l k a l i n e c y c l e (more seve re and no t commercially t y p i c a l ) t h e serum f r a c t i o n s became p r o g r e s s i v e l y da rke r . Resu l t s were s i m i l a r whether whole p u l p o r f r a c t i o n s were cyc led .

Uni t Opera t ion T i m e s

An e a r l y cho ice was f aced on exper imenta l equipment l o c a t i o n . E i t h e r i t could be p laced i n s i d e t h e cannery a d j a c e n t t o t h e p e e l removal o r out- side'. Each had an advantage. I f i n s i d e , t h e t i m e between c a u s t i c app l i ca - t i o n and a c i d i f i c a t i o n could be reduced perhaps by t h r e e minu tes , bu t t h e r e w a s n o t s u f f i c i e n t space a v a i l a b l e t o l o c a t e a l l t h e equipment t o g e t h e r , and t h e exper imenta l f l e x i b i l i t y would have been d r a s t i c a l l y reduced and c o n t r o l impaired. With t h e equipment o u t s i d e , f u l l f l e x i b i l i t y i n u t i l i - z ing t h e exper imenta l equipment was r e t a i n e d . Subsequent exper imenta t ion i n 1975-76 i n d i c a t e d t h a t even a c i d i f y i n g t h e p e e l d i r e c t l y out of t h e caus- t i c a p p l i c a t o r d i d n o t a p p r e c i a b l y change t h e product ove r that ob ta ined from t h e 1976 modif ied c a u s t i c pee l ing l i n e .

Time increments f o r each u n i t o p e r a t i o n are shown i n Table 4 f o r t h e p e e l recovery performed i n 1975 a t t h e cannery. A similar t i m e sequence was fol lowed i n 1976. I d e a l l y , t h e t i m e exposure t o t h e c a u s t i c should be z e r o t o minimize p o t e n t i a l f l a v o r and c o l o r changes. On a p r a c t i c a l b a s i s , immersion i n t h e c a u s t i c i s necessa ry f o r p e e l i n g , and i t i s i n t h i s immer- s i o n t h a t t h e p r i n c i p a l changes and cond i t ion ing occur .

When t h e p e e l w a s r ece ived a t l lO"F, t h e c o l o r w a s v i r t u a l l y t h e same as a t t h e t i m e of p e e l removal; p e e l r ece ived a t 140°F was a p p r e c i a b l y d a r k e r , such as when t h e c a u s t i c a p p l i c a t o r s o l u t i o n overf lowed i n t o t h e pee l . The 30°F tempera ture i n c r e a s e , r a t h e r t h a n t h e h i g h e r c a u s t i c c o n t e n t , was proba- b l y t h e predominant cause of t h e darkening. A s d i s c u s s e d under vacuum evapora t ion , a c i d i f i e d recovered p e e l pu lp i s more s e n s i t i v e t o thermal darkening than conven t iona l juice. This d i s p l a y s t h e importance of con t ro l - l i n g t h e p rocess throughout , no t j u s t t a k i n g any p e e l and ' 'throwing" i n ac id .

The t i m e between t h e pee l removal and a c i d i f i c a t i o n (about 4.4 minutes) could be sho r t ened , bu t t h e r e was no t s u f f i c i e n t i n d i c a t i o n that a s h o r t e r time would improve q u a l i t y apprec i ab ly . I n 1976 tomatoes were taken d i r e c t l y from t h e c a u s t i c a p p l i c a t o r and q u i c k l y plunged i n a mi ld hydroch lo r i c a c i d s o l u t i o n t o "immediately" a c i d i f y t h e tomato pee l ; t hen t h e p e e l w a s removed by hand and t h e p u l p judged f o r p e c t i n c o n t e n t , c o n s i s t e n c y , enzyme a c t i v i t y , and co lo r . There w a s no major d i f f e r e n c e between t h e pulp from t h i s " ins tan- taneous" a c i d i f i c a t i o n and p u l p t h a t w a s he ld a t pH 11 f o r 5-10 minutes a t

39

100-110°F. If t h e r e i s a cho ice , t h e quicker a c i d i f i c a t i o n i s p r e f e r r e d as i t reduces p o t e n t i a l adverse changes i n c o l o r and f l a v o r .

Product Color , F lavor and Vitamins--Product c o l o r and f l a v o r d i f f e r e d between 1975 and 1976, i l l u s t r a t i n g how t h e pee l ing o p e r a t i o n and recovery techniques a f f e c t t he recovered pulp. A s s t a t e d be fo re , when the c a u s t i c a p p l i c a t o r overf lowed, t h e recovered pu lp darkened, had poor f l a v o r , and 2 t o 3 times t h e normal sa l t con ten t . But even under t h i s very a d v e r s e , a t y p i c a l c o n d i t i o n , t h e c o l o r and f l a v o r could be a food g r a d e , a l b e i t a t times a s t anda rd Grade C r a t h e r than Grade A.

TABLE 4 . UNIT OPERATIONS TIMES - 1975

Operat ion

T i m e (minutes ) Nominal Temperature

Equipment Increment T o t a l ( O F )

Lye a p p l i c a t i o n

P e e l Removal

P e e l Conveyor

Peel Pump and Pipe

P e e l Tank ( d )

Ex trac t o r

Hot Break

Pulp Tank

Canning

Heat Process ing

Cooling

C

C

C

C

E

E

E

E

E

E

E

0.5

0.5

0.6

3.8

5.0

0.5

25.0

0.8

10.0

35.0

30.0

0.5

1.0

1.6

5.4

10.4

10.9

35.9

36.7

46.7

81.7

111.7

210

200

180

180-110 ( c )

120

110

2 00

2 00

185

212

90

( a ) C = cannery system, E = Experimental system ( b ) A f t e r e n t e r i n g c a u s t i c a p p l i c a t o r ( c ) P e e l cooled as pumped through 200 f t pipe. ( d ) A c i d i f i c a t i o n t o pH 4.2 about 0.1 minute a f t e r e n t r y i n t o pee l

tank , o r about 5.5 minutes a f t e r tomato e n t e r e d c a u s t i c a p p l i c a t o r .

40

A s shown i n Table 1, t h e Vitamin A w a s about t h e same i n t h e canned p e e l pu lp a s i n t h e processed convent iona l pulp. Beta-carotene i s q u i t e s t a b l e , and s i n c e the o u t e r s u r f a c e ( p e e l ) of t h e tomato i s r i c h e r than the whole tomato i n t h i s provi tamin , t h e recovered pu lp had a h i g h e r c a r o t e n e va lue than convent iona l tomato pulp.

Ascorbic a c i d i s so e a s i l y decreased i n the presence of h o t c a u s t i c that i t w a s no t p r e s e n t i n pulps from e i t h e r y e a r (Table 1 ) . Samples of recovered p e e l pulp were o r i g i n a l l y analyzed f o r a s c o r b i c a c i d by v i s u a l t i t r a t i o n , b u t , i n view of t h e f a i r l y h igh appa ren t l e v e l s of a s c o r b i c found, and t h e p o s s i b l e presence of reductones , i t was d e s i r a b l e t o s tudy r e p r e s e n t a t i v e canned samples t o determine w h a t p o r t i o n of t h e appa ren t a s c o r b i c a c i d t i t e r was due t o i n t e r f e r i n g subs tances . A d i r e c t photometr ic reading ( a t 540 mu) of t h e a s c o r b i c a c i d osazone i n t h e presence of t h e osazones of i n t e r f e r i n g compounds gave a va lue of 7 mg of a s c o r b i c a c i d p e r 100 g of product i n s t e a d of t h e 11 mg found by t h e v i s u a l t i t r a t i o n of t h e reduced a s c o r b i c a c i d . S ince i t became apparent that t h e r e w a s a l a r g e q u a n t i t y of reductones p re sen t i n t h e sample, i t was necessa ry t o chromatographica l ly separate t h e a s c o r b i c a c i d osazone from o t h e r i n t e r f e r i n g osazones i n o r d e r t o p rope r ly measure the totral a s c o r b i c a c i d conten t . The c o l o r i m e t r i c de t e rmina t ion of t h e i s o l a t e d a s c o r b i c osazone a t 520 mp showed that t h e samples a c t u a l l y conta ined less than 0.6 mg a s c o r b i c a c i d per 100 g. It w a s concluded that f o r 1975 and 1976 p rocess ing , a l l s i g n i f i c a n t a s c o r b i c a c i d a c t i v i t y i n the p e e l pulp w a s l o s t by exposure t o h igh pH, h igh tempera tures , and a i r (oxygen) c o n t a c t s dur ing the pee l ing process and subsequent process ing .

Canned samples of 1975 and 1976 materials were s t o r e d t o check t h e c o l o r s t a b i l i t y . The 1975 samples were s t i l l a b r i g h t r ed a f t e r s i x months a t 100°F i n t i nned l i n e d cans ( s t anda rd can f o r tomato products ) . check and t o e l i m i n a t e the p o s s i b l e "bleaching" o r i n h i b i t i n g a c t i o n of t h e t i n , t h e 1976 samples were s t o r e d i n double enameled cans. A f t e r n i n e months a t 100"F, t h e s e samples were s t i l l "br ight" ; t h e r e w a s a " s l i g h t " darkening of t h e serum as happens t o tomato products on s t o r a g e , bu t t h i s w a s less than t h a t of a Grade A commercial puree ( 2 1 ) . The c o l o r and f l a v o r s c o r e s f o r t h e 1976 products are shown i n Table 5. Color s c o r e s are based on t h e Hunter Color-Difference Meter and f l a v o r s were determined o r g a n o l e p t i c a l l y ; both were eva lua ted by t h e USDA, Food Sa fe ty and Qua l i ty S e r v i c e , F r u i t and Vegetable Qua l i ty Div i s ion , Processed Products Branch, S tockton , CA.

A s a f u r t h e r

Cons is tency , V i s c o s i t y , and Pectin--In t h e recovered pee l pu lp t h e r e w a s a d e s i r a b l e , above average number of tomato whole ce l l s which gave the - pu lp a h e a v i e r , - t h i c k e r appearance compared t o conven t iona l tomato pulps . In g e n e r a l though, when t h e cons i s t ency o r v i s c o s i t y w a s measured, t h i s pu lp showed t h e cons i s t ency and v i s c o s i t y of a good cold-break processed pu lp (Table 6 ) . Serum v i s c o s i t y approached t h a t of water which i n d i c a t e s deg rada t ion of t h e p e c t i n as would be expected from t h e c a u s t i c exposure. I n s o l u b l e s o l i d s are g e n e r a l l y t h e primary c o n t r i b u t o r s t o tomato-product cons i s t ency , bu t p e c t i n i s impor tan t because i t s e r v e s t o hold t h e i n s o l u b l e s o l i d s i n suspens ion and reduce the tendency f o r serum s e p a r a t i o n . The con- s i s t e n c y of t h i s recovered peel-pulp would be a p p r o p r i a t e f o r p i zza sauce o r soups which normally may use a cold-break pu lp because i t i s d e s i r a b l e t o th i cken wi th s t a r c h . For o t h e r sauces o r pu lps where a hot-break

41

material i s normally used , combining recovered pulp wi th convent iona l pulp i n a r a t i o of 1:3 r e s u l t s i n a material wi th t h e c o n s i s t e n c y and c h a r a c t e r of a hot-break pulp.

Samples of p e e l pulps were eva lua ted f o r p e c t i c enzyme a c t i v i t y i n both 1975 and 1976, bo th i n t h e l a b o r a t o r y and from t h e exper imenta l equipment. It w a s concluded t h a t t h e 1975 recovered p e e l p u l p had l i t t l e o r no p e c t i c enzyme a c t i v i t y as rece ived when sampled b e f o r e t h e h e a t i n g ; t h e r e f o r e , a h o t break i s cons idered unnecessary because t h e r e are no enzymes t o i n a c t i v a t e . I f , however, t h e p rocess i s modif ied so t h a t t h e r e i s s u b s t a n t i a l l y less exposure t o c a u s t i c , t hen the h o t break could be necessary . Adequate sub- s t ra te was a v a i l a b l e i n t h e tes t s i n c e t h e a d d i t i o n of 0.03% commercial enzyme (Rohm and Haas No. 59-L, Rohm and Haas Inc . , P h i l a d e l p h i a , Penna.) t o t h e t e s t mix tu re r e s u l t e d i n a r a p i d l o s s of cons i s t ency . Without s u b s t r a t e a d d i t i o n , t h e r e w a s no change i n pulp c o n s i s t e n c y ove r a per iod of 1 t o 3

TABLE 5. STORAGE STABILITY OF RECOVERED PULP - 1976

Color Score ( b ) T o t a l

F l avor ( b ) S o l i d s Sample S to rage Temp. & T i m e S to rage Temp. & T i m e s a l t

( a > 34 "F 100 O F 34 "F 100°F f r e e 9 mos. 1 mo. 3 mos. 9 mos. 9 mos. 1 mo. 3 mos. 9 mos. ( % )

76007 51.0 7 600 9 51.5 7601 1 51.9 7601 3 51.6 76021 50.9 76023 50.8 76025 50.2 76027 49.7 7603 1 49.3 Com" 1 ( c ) 46.9

51.0 51.3 51.1 51.6 50.8 50.9 50.1 49.3 48.5 46.7

50.9 50.4 50.9 50.6 50.8 50.8 51.2 51.2 50.5 50.1 50.7 49.5 49.9 49.3 48.9 48.2 48.0 47.0 46.0 43.1

F G F G F G G

G G G G

F G F G G F G G G G G G G

F G F G

F G F G F G F G F G

G F G

G G

F G

F G 6.6 F G 6.8 F G 6.2 F G 7.1 F G 7.2 F G 6.1

G 5.6 G 6.1 G 6.4

F G 14.4

( a ) Sample number as embossed on l i d s of canned samples; 76 = yea r an OXX i s the sample and t r i a l number.

( b ) Color Grade A, i s 45-50, Grade C i s 40-44 f o r canned tomato pulp. Color determined us ing t h e Hunter Lab Color-Difference Meter D25D- o p t i c a l head and formula: ( a / m).

wi th type A 3 Score = -122 + 4.139L - 0.081883L + 130.572 For f l a v o r , F G = f a i r l y good. G = good.

(-c) Pu lp samples judged a t t o t a l s o l i d s shown, except commercial sample was d i l u t e d t o 8.5% NTSS.

42

TABLE 6. CANNED SAMPLES OF RECOVERED PULPS, 1976 --

T o t a l Flowtube Sample PH Na C 1 NTS S Solids V i s c o s i t y Qua l i ty (1976) (% w/w) (% w/w) (% w/w) ( s e c Grade (a 1 (b) (C) - ( d ) ( e (f)

76003 76004 76005 7 600 6 76007 7 60Q 9 7601 1 76013 76015 7601 7 7601 9 76021 76023 76025 7602 6 76026 OM 7602 7 7602 9 76031 76033 76035 75037 76039 76041 76043 7 6045

3.7 4.2 4.0 4.1 4.15 4.25 4.3 4.45 4.15 4.05 4.1 4.1 4.05 4.1 4.3 4.2 4.05 4.1 4.25 4.0 4.15 4.1 4.1 4.1 4.15

1.07 1.24

.97 2.22 1.72

.93

.94

.92

.90 1.31 1.38 1.13 1.42

.94 1.04 1.12 1.04 1.46 1.16 0.98 0.99 1.0 0.92 1.08 0.84

3.8 4.7 4.6 4.5 5.6 5.6 5.0 5.8 5.2 5.0 6.3 5.7 4.5 4.5 4.2 4.0 5.9 5.7 6.0 4.6 4.8 4.3 4.6 4.6 4.6

5.4 6.7 6.2 7.3 9.1 7.7 6.8 7.6 7.2 7.5 8.6 7.8 6.6 6.5 5.8 5.9 7.1 7.7 7.7 6.3 6.4 6.0 6.2 6.6 6.4

50 146 158 206 2 86 2 52 213 232 2 42 40 6 534 2 80 218 140 173 261 181 122 180 178 229 196 21 7 304 3 02

A A A A

A A A A A

A A

A A A

A

C

C C

C C

C C C C

C 4.1 0.92 4.9 6.6 312 A

AVR 4.13 1.14 5.0 6.9 231 62 %A CC?J ( g ) 4.2 0.50 6.4 6.7 70 (i) A t o C CCTP (h) 4.3 0.17 12.2 12.75 -- (j) A t o C

( con t inued)

43

TABLE 6. (cont inued)

( a ) Sample number as embossed on l i d s ; miss ing even-numbered cans conta ined pee led , whole tomatoes.

( b ) N a C 1 , sodium c h l o r i d e ( s a l t ) . ( c ) NTSS, n a t u r a l tomato s o l u b l e s o l i d s ; does n o t i n c l u d e NaCl from a c i d i f i -

( d ) T o t a l S o l i d s , i n c l u d e s N a C l from a c i d i f i c a t i o n . ( e ) Flowtube V i s c o s i t y , seconds p e r 5 m l sample. ( f ) Qua l i ty Grade (except CCTJ), samples graded as tomato puree f o r c o l o r ,

d e f e c t s , and f l a v o r using puree s t a n d a r d s (Reference 211, without s o l i d s con ten t q u a l i f i c a t i o n , by USDA F r u i t and Vegetable Qua l i ty Div i s ion , Food S a f e t y and Qua l i ty Se rv ice , Stockton, C a l i f o r n i a . Ten samples graded C because of speck d e f e c t s ; samples had good f l a v o r except n i n e which were f a i r l y good, and one which had a t i n f l a v o r . Tr ia l c o n d i t i o n s v a r i e d as process v a r i a b l e s were being i n v e s t i g a t e d , p r i m a r i l y as r e l a t e d t o p re t r ea tmen t and pee l ing a i d s .

s i n g l e s t r e n g t h .

conc en t ra t ed .

cat ion.

( g ) CCTJ, commercial canned tomato j u i c e ; t y p i c a l ave rages , s a l t e d product ,

( h ) 'CCTP, commercial canned tomato puree; t y p i c a l averages , u n s a l t e d product ,

( i ) J u i c e range w a s 28-148 seconds. ( j ) Puree i s much more v iscous than j u i c e , measured by a Bostwick cons i s to -

meter, and Bostwick r ead ings are no t c o n v e r t i b l e t o Flowtube Viscos i ty .

hours . The l i t e r a t u r e (29 ) i n d i c a t e s t h e s e n s i t i v i t y of p e c t i n t o c a u s t i c cond i t ions ; f o r example, a s o l u t i o n a t room tempera ture and con ta in ing 0.03 g of p e c t i n per 100 m l w a s completely hydrolyzed i n 30 minutes wi th 0.42 sodium hydroxide, o r i n about 10 minutes with 0.08% sodium hydroxide. By c o n t r a s t , t h e tomato s u r f a c e i s exposed i n cannery o p e r a t i o n s t o 10 t o 18% c a u s t i c a t 200 t o 210°F f o r 30 seconds, then f u r t h e r exposed t o about 1.5% c a u s t i c f o r 5 minutes a t tempera tures d e c l i n i n g t o 110°F. Caustic pee l ing depends no t o n l y on apply ing t h e c a u s t i c t o t h e o u t e r s u r f a c e of t h e tomato but a l s o on t h e c a u s t i c permeating the s k i n ; t he re fo re , i f p e c t i n i s t o be r e t a i n e d i n t h e recovered pulp , c o n s i d e r a t i o n must be g iven t o w h a t occurs i n the c a u s t i c ba th .

The re fo re , t r i a l s were made on a c i d i f y i n g t h e tomato s u r f a c e be fo re p e e l removal i n l i e u of a c i d i f y i n g t h e p e e l a f t e r removal. dipped and cooled i n d i l u t e hydrochlor ic a c i d immediately a f t e r removal from t h e c a u s t i c bath. s k i n , and serum v i s c o s i t y and peroxidase a c t i v i t y were checked. tomato pulp w a s r a i s e d t o pH 11, hea ted , r e - a c i d i f i e d , and checked. Resu l t s were similar i n both cases though some "v i rg in" pulp w a s i n e v i t a b l y inc luded when hand pee l ing and t h e p e c t i n and peroxidase t h e r e f o r e appeared ( incor - r e c t l y ) t o have been on ly p a r t i a l l y a f f e c t e d by t h e c a u s t i c . serum v i s c o s i t y approached 1 cp and the peroxidase was i n a c t i v a t e d when t h e tomato o r pulp w a s exposed t o pH 11.4 and 180°F f o r 40 sec; a t 80°F and 40 sec exposure serum v i s c o s i t y w a s s t i l l n i l and t h e r e w a s no peroxidase a c t i v i t y .

Tomatoes were

The p e e l w a s removed manual ly , t h e p u l p taken from t h e Also, raw

In g e n e r a l , t h e

44

From t h e s e 1975 and 1976 r e s u l t s t h e r e i s no apparent need t o f u r t h e r cons ide r enzyme i n a c t i v a t i o n , whether p e c t i n a s e o r peroxidase. However, s i n c e t h e a c i d i f i e d pulp h a s a temperature of 100 t o 130"F, c o n s i d e r a t i o n should be g iven i n a commercial i n s t a l l a t i o n t o h e a t i n g a c i d i f i e d p e e l wi th a h o t macerate going t o a pu lpe r - f in i she r ; t h i s a v o i d s p u t t i n g i n a hea t ing o p e r a t i o n s o l e l y f o r recover ing p e e l pulp. by both product ion and r e g u l a t o r y c o n s i d e r a t i o n s .

Such a d e c i s i o n w i l l be a f f e c t e d

Amino Acids--Since t h e r e i s on ly about 1% p r o t e i n i n tomatoes, t h i s would no t normally be cons idered a s i g n i f i c a n t d i e t a r y sou rce of p r o t e i n . This i s r e f l e c t e d i n the g e n e r a l use of tomatoes i n sauces and ca t sup , t h e main excep t ion being tomato j u i c e which i s cons idered a sou rce of a s c o r b i c a c i d (Vitamin C ) . However, amino a c i d s are worthy of a n a l y s i s because they can i n d i c a t e t h e amount of exposure t o a l k a l i and hea t . Such a chemical index of process ing e f f e c t s could be used f o r f u t u r e process mod i f i ca t ions t o o b t a i n optimum product q u a l i t y . than o t h e r s by h i g h pH and h e a t , and, t h e r e f o r e , t h e i r r e l a t i v e changes can be used as i n d i c e s of process induced changes.

C e r t a i n amino a c i d s are a f f e c t e d more

* Amino a c i d l e v e l s i n the a c i d hydro lysa t e s of 1975 and 1976 samples of recovered p e e l pu lps were determined and compared wi th t h o s e of f r e s h and conven t iona l ly processed tomato pulp. Exposure of tomato pulp t o c a u s t i c dur ing t h e pee l ing process r e s u l t e d i n t h e deg rada t ion of c e r t a i n amino a c i d s , t h e degree of which depended on the exposure ( t i m e , pH, and tempera- t u r e ) . Argin ine , which i s known t o be u n s t a b l e t o c a u s t i c , was s i g n i f i c a n t l y lower i n t h e recovered pulp samples than i n e i t h e r t he f r e s h o r t he conven- t i o n a l l y processed samples. The r a t i o of a r g i n i n e t o a more s t a b l e amino a c i d , such as i s o l e u c i n e o r h i s t i d i n e , w a s chosen as a n index of t h e product cond i t ion . l a t e d f o r conven t iona l ly processed tomato (A/H = 1.30) was c l o s e r t o that of r a w tomato (A/H = 1.30) than w a s that of recovered pu lp (A/H = 0.35 i n 1975 and 1.06 i n 1976). Thus, t h e da t a i n d i c a t e t h a t t h e u n s t a b l e amino a c i d s i n t h e recovered pu lp samples were a l t e r e d t o a g r e a t e r degree than those i n conven t iona l ly processed tomatoes. I n conven t iona l ly c a u s t i c pee led tomatoes, such changes occur a t t h e tomato s u r f a c e , which i s r i n s e d , and do no t a l t e r the g e n e r a l amino a c i d conten t . recovered p e e l pu lps were a l t e r e d much less than i n 1975. A/H r a t i o was found t o be a s e n s i t i v e and o b j e c t i v e i n d i c a t o r of pulp proces- s i n g h i s t o r y t h a t w a s a l s o i n g e n e r a l agreement w i t h c o l o r and f l a v o r grades.

For example, t h e mean a r g i n i n e t o h i s t i d i n e (A/H) r a t i o calcu-

Never the l e s s , t h e 1976 There fo re , t h e

On t h e b a s i s of t h e Kje ldahl a s s a y s , i t appea r s that about 24 t o 27% of t h e t o t a l n i t r o g e n ( p r o t e i n ) con ten t of t h e tomato samples e x i s t s i n t h e i n s o l u b l e f r a c t i o n of bo th t h e convent iona l and the exper imenta l products . Th i s s i m i l a r i t y s u g g e s t s that t h e r e w a s l i t t l e o r no change i n p r o t e i n so lu- b i l i t y r e s u l t i n g from exposure t o h e a t and h igh pH.

Product Mold, I n s e c t Fragments and Bacterial Counts--In 1975 t h e p e e l taken from t h e commercial pee l ing o p e r a t i o n w a s a lmost devoid of mesophi l ic and the rmoph i l i c b a c t e r i a , and t h e l e v e l s were i n s i g n i f i c a n t compared t o those i n normal cannery o p e r a t i o n s a t a comparable p o i n t i n processing. Bacterial counts were made t o check t h e c l e a n l i n e s s of t h e equipment, t o see i f t h e r e was a s i g n i f i c a n t d i f f e r e n c e b e f o r e and a f t e r t he hea t ing

45

( h o t b r e a k ) , and t o judge the mic rob io log ica l s t a b i l i t y of t h e p e e l coming from t h e commercial pee l ing . A s i t tu rned o u t , t h e c a u s t i c p e e l i s inher- e n t l y m i c r o b i o l o g i c a l l y s t a b l e and normal c leanup and s a n i t a t i o n procedures would be adequate . Therefore , i t can be assumed that t h e caus t i c -pee l ing o p e r a t i o n a t h igh pH and 200-210°F does have a s t r o n g b a c t e r i c i d a l e f f e c t and t h a t t h e c a u s t i c remaining on t h e p e e l has a b a c t e r i s t a t i c a c t i o n .

Also i n 1975, t h e mold and insect-fragment counts on the canned, recov- e red pulp were uniformly low and r e f l e c t t h e thorough washing and s o r t i n g sys t em a t t h e cannery which w a s desc r ibed ear l ie r ( s e e Washing and S o r t i n g ) . These microscopic counts were w e l l under t h e maximum mold count t o l e r a n c e f o r tomato j u i c e (20% of t h e Howard s l i d e f i e l d s ) and t h e r e f o r e similar t o that normally encountered i n commercial products . In s o f a r a s t h i s cannery w a s t y p i c a l of t h e i n d u s t r y , t h e e x i s t i n g raw product c l ean ing procedures would seem q u i t e adequate i f p e e l pu lp i s recovered. mental freedom t o va ry s o r t i n g . Truck l o a d s wi th a C a l i f o r n i a S t a t e Grading C e r t i f i c a t e showing 1% o r less mold r e q u i r e d minimal o r no s o r t i n g t o s t a y w i t h i n mold t o l e r a n c e ; i f graded as 3% mold, up t o 20% of t h e tomato weight might need t o be removed so a s t o s t a y wi th in to l e rance . This 20% inc luded both tomatoes showing mold and broken tomatoes which would subsequent ly d i s i n t e g r a t e i n t h e c a u s t i c b a t h o r not y i e l d p r o p e r l y pee led whole tomatoes. I n g e n e r a l , when the C a l i f o r n i a S t a t e l oad grade c e r t i f i c a t e shows 3% o r more, p a r t i c u l a r a t t e n t i o n must be g iven t o s o r t i n g . between p i ck ing , S t a t e g rad ing , and p rocess ing , as w e l l as t h e seasonal p e r i o d , w i l l modify t h e amount of s o r t i n g needed.

In 1976 t h e r e was exper i -

The e lapsed t i m e

Bacterial p l a t e counts were made on samples from t h r e e consecut ive days i n 1975 (October 14 , 15 , 16) w i th vary ing t y p e s of “cleanup”. Up t o October 14 , t h e equipment w a s f l u shed wi th water a t t h e end of t h e ope ra t ing day and t h e tomato pu lp r e s i d u e s i n open v e s s e l s were removed by hand scrubbing. For October 15, t h e equipment w a s washed as u s u a l , bu t a 10 ppm c h l o r i n e s o l u t i o n w a s p u t i n t o t h e equipment overn ight ; t h e upper s u r f a c e of ho r i - z o n t a l p ipes w a s assumed t o be f r e e of tomato material. P repa ra to ry t o October 1 6 , t h e p ip ing and equipment w a s d i sassembled , hand scrubbed, and r i n s e d wi th 100 ppm c h l o r i n e s o l u t i o n , d r a i n e d , and r i n s e d wi th po tab le water. Pulp samples were taken be fo re and a f t e r t h e h o t b reak , a t t h e pu lp t a n k , and from t h e 200-gal holding tanks used f o r t h e m a t e r i a l balance. On October 1 4 , t h e t o t a l p l a t e count v a r i e d from 6,000 t o 17,000 pe r m l of tomato p e e l pu lp depending on sample l o c a t i o n ; t h i s i s a much lower count t han might be expected i n convent iona l cannery o p e r a t i o n s a f t e r t h e h o t break s t a g e , and i s a t t r i b u t e d t o the c a u s t i c pee l ing ope ra t ion . In the October 14 samples , v e g e t a t i v e ce l l s were found but no spores . The impli- c a t i o n i s t h a t t he h o t c a u s t i c pee l ing reduced the coun t , bu t that t h e r e was some re - inocu la t ion , p o s s i b l y from unclean exper imenta l equipment o r from t h e atmosphere s i n c e t h e v e s s e l s were open. t h e counts were zero f o r both v e g e t a t i v e cel ls and spores . S ince t h i s equipment w a s n o t opera ted on a 24-hour b a s i s , t h i s in format ion should n g t be e x t r a p o l a t e d t o a round-the-clock ope ra t ion .

On October 15 and 16 ,

Pest ic ides--Various p e s t i c i d e s are a p p l i e d i n t h e tomato f i e l d t o p r o t e c t c rops from t h e t i m e of p l a n t i n g through h a r v e s t i n g . Although t h e use and a p p l i c a t i o n of a l l p e s t i c i d e s are c l o s e l y r e g u l a t e d by t h e

46

Enviromental P r o t e c t i o n Agency, p e s t i c i d e r e s i d u e s a r e unavoidably on t h e s u r f a c e of d e l i v e r e d produce. To a s s u r e t h a t t h e l e v e l s of p e s t i c i d e s i n t h e f i n a l p roducts are w e l l below t o x i c c o n c e n t r a t i o n s , maximum pe rmis s ib l e l e v e l s have been e s t a b l i s h e d by t h e FDA. Prev ious s t u d i e s have shown t h a t p e s t i c i d e r e s i d u e s on raw tomatoes are conta ined almost e x c l u s i v e l y i n t h e waxy l a y e r ove r l ay ing t h e s k i n . Since t h e p e e l r e s i d u a l , from which pu lp was being recovered dur ing t h i s s t u d y , con ta ined an ex t remely h igh percentage of s k i n , samples c o l l e c t e d from t h e tes t system were ana lyzed f o r p e s t i c i d e r e s i d u e s (Table 7 ) . Crop h i s t o r i e s of t h e tomatoes d e l i v e r e d t o t h e p l a n t i n d i c a t e d t h a t toxaphene ( a c h l o r i n a t e d camphene c o n t a i n i n g 67-69% c h l o r i n e ; a l s o c a l l e d camphechlor) w a s used most widely. Thiodan ( a c h l o r i n a t e d hydrocarbon) and p a r a t h i o n ( a n organophosphate) were used t o a lesser e x t e n t . A l l of t h e s e are d e t e c t a b l e by g a s chromatography. Appropr ia te samples were ana lyzed f o r each of t h e t h r e e p e s t i c i d e s . The p e s t i c i d e coun t s i n 1976 were s i m i l a r t o 1975, but t h e 1976 s k i n waste and recovered pu lps were obta ined from a s h o r t t i m e ( two minutes) ba tch s e p a r a t i o n of pulp. The re fo re , t h e 1975 r e s u l t s are cons idered t o be more i n d i c a t i v e of a commercial ope ra t ion .

The l e g a l t o l e r a n c e (maximum) f o r toxaphene r e s i d u e on foods w a s 7.0 ppm i n 1975 and 1976. Table 7 shows both t h e average and range of toxaphene i n t h e recovered pu lp f o r 1975 wi th an average of 0.4 ppm i n t h e recovered (100%) pu lp , i .e. about 6% of to l e rance , and none of t h e samples were above t o l e r a n c e . The 35 ppm average i n t h e s k i n f r a c t i o n i l l u s t r a t e s t h e need t o separate t h e s k i n from t h e pulp. The e f f e c t s of t h e f i n i s h e r c l e a r a n c e and s k i n s i z e on s e p a r a t i o n of t h e s k i n from t h e pulp w a s d i scussed under t h e heading “Pulp Ex t rac t ion” . A c l o s e c l e a r a n c e between t h e f i n i s h e r paddles and s c r e e n w i l l cause t h e s k i n t o pass through t h e s c r e e n wi th t h e p u l p , and t h i s h igh s k i n c o n t e n t can r e s u l t i n a h igh p e s t i c i d e c o n t e n t i n t h e pulp. Regula t ions p r o h i b i t b r ing ing over - to le rance materials i n t o compliance by d i l u t i o n . The re fo re , p rudent manufactur ing p r a c t i c e d i c t a t e s t h e need f o r an adequate f r a c t i o n a t i o n of s k i n from t h e pulp .

U.S. S tandards _______ of Ident i t j - -S ince t h e proposed p rocess mod i f i ca t ions and materials may o r may no t be t o t a l l y covered by t h e e x i s t i n g U.S. Food and Drug Regu la t ions , t h e FDA Bureau of Foods was consu l t ed on t h e fo l lowing concerns: (1 ) u t i l i z a t i o n of p u l p de r ived from c a u s t i c p e e l i n g s , ( 2 ) a c i d i - f i c a t i o n of t h e c a u s t i c p e e l w i th food-grade hydroch lo r i c a c i d , ( 3 ) use of food-grade c a p r y l i c ( o c t a n o i c ) a c i d a s a p e e l i n g a i d wi th r e s i d u e p resen t i n t h e recovered pulp , and ( 4 ) t h e l a b e l i n g requi rements when recovered pulp i s u t i l i z e d . Whether a commercial i n s t a l l a t i o n and product would meet t h e e x i s t i n g , and c u r r e n t l y being r e v i s e d , r e g u l a t i o n s , o r whether f u r t h e r t e c h n i c a l and r e g u l a t o r y c o n s i d e r a t i o n s are needed, w i l l depend on FDA judg- ment. P e r t i n e n t r e g u l a t i o n s i n 1975-76 were t h e former 21 CFR 53.10-0.40, tomato products ; 21 CFR 121.1070, food-grade f a t t y a c i d s ; and 121.1091, chemicals used i n l y e pee l ing . . A r e o r g a n i z a t i o n and r e p u b l i c a t i o n of regu- l a t i o n s on food f o r human consumption appeared on March 15, 1977 i n 42 FR 14302-14306; t h i s c r o s s r e f e r e n c e s t h e o l d and new s e c t i o n numbers. The United States Standards f o r Grades of Canned Tomato Puree and Canned Tomatoes are set f o r t h i n 29 FK 9838 (1964) and amended i n 35 FR 3651 (1970) and 29 FR 7909 (1964).

47

TABLE 7. PESTICIDE RESIDUES I N RECOVERED PEEL PULP __ - .____~_____-________________I_______ ___

P a r a t h i o n Thiodan ____ --- No. of Average Range No. of Average Range No. of Average Range

Sample, 1975 Samples (ppm) (ppm) Samples ( p p d ( p p d Samples (ppm) ( P P ~

-~ ___ --- Toxaphene

( a ) (a, ____ __ ___- ( a ) - ____

3 0.01 nd-0.02 3 nd nd-nd

3 nd nd-nd 3 nd nd-nd

Whole tomatoes 3 0.2 0.2 - 0.3 ( f r e s h )

( b e f o r e canning)

pu lp e x t r a c t i o n

pu lp e x t r a c t i o n ) ( b )

p u l p e x t r a c t i o n ) ( b )

Pee led tomatoes 3 nd nd

0.2 nd - 0.4 5 O.OO(2) nd-0.01 5 0.01 nd-0.06

0.03 nd-0.08

e Caus t i c pee l ings be fo re 5 aJ P e e l s k i n ( a f t e r 20 35. 3. - 150. 7 0.04 nd-0.15 7

10 nd nd-nd P e e l pulp ( a f t e r 27 0.4 nd - 4.8 10 O.OO(1) nd-0.01

nd = none d e t e c t e d ( a ) De tec t ion l i m i t = 0.1 ppm f o r Toxaphene; 0.01 ppm f o r Thiodan and Para th ion . ( b ) Pulp E x t r a c t o r normally set wi th 0.5-inch paddle-screen c l ea rance ; s c r e e n ho le s i z e v a r i e d from

0 .033 t o 0.125-inch. Range a l s o i n c l u d e s o t h e r s c r e e n s and clearances.

C u r r e n t l y , t h e tomato S tandards of I d e n t i t y are being r ev i sed and r e -wr i t t en by FDA wi th c o n s i d e r a t i o n g iven t o t h e p re sen t CODEX r e g u l a t i o n s and p resen t day needs. To t h e r e a d e r s of t h e s e o r pas t r e g u l a t i o n s , t hey should be aware of t h e f a c t t h a t i t is not on ly t h e wording of r e g u l a t i o n s t h a t are of consequence, but t h e i n t e n t ( u n w r i t t e n ) as w e l l .

A proposed a f f i r m a t i o n of G U S s t a t u s f o r c a p r y l i c a c i d a s an i n d i r e c t and d i r e c t human food i n g r e d i e n t w a s publ ished on June 14, 1977 (28) . This proposa l i s s u b j e c t t o p u b l i c comment, r e v i s i o n , and approval . The s i g n i f i - cance of t h i s GRAS s t a t u s would p l ace c a p r y l i c a c i d i n t h e s t a t u s of an i n g r e d i e n t r a t h e r than that of an a d d i t i v e , though p o s s i b l y j u s t as a f l a v o r . Use l e v e l s are proposed i n t h e new paragraph. The new paragraph 184.1025d (28) proposes that the i n g r e d i e n t ( c a p r y l i c a c i d ) be used i n foods a t l e v e l s no t t o exceed good manufactur ing practices (GMP) and t h a t f o r food c a t e g o r i e s no t s p e c i f i c a l l y mentioned, GMP r e s u l t s i n maximum l e v e l s , a s se rved , of 0.001% (10 ppm) o r less. The expected use of recovered p e e l pu lp i n tomato p roduc t s , a s consumed, would be below t h i s 0.001% l e v e l . t i o n s (S tandards of I d e n t i t y ) do n o t addres s u t i l i z a t i o n of recovered tomato p e e l pulp d i r e c t l y , a l though t h e l i q u i d from p e e l s and c o r e s may be used as a pa6king media f o r canned tomatoes and f o r manufactur ing canned puree and ca t sup (155.190-.194). The Standards of I d e n t i t y are now being r ev i sed and w i l l i n f l u e n c e t h e f u t u r e u t i l i t y of recovered p e e l pulp.

The c u r r e n t regula-

E f f l u e n t s and Wastes--One of t h e prime c o n s i d e r a t i o n s when i n i t i a t i n g t h e p r o j e c t was no t on ly t o reduce l i q u i d and s o l i d e f f l u e n t s i n terms of c a u s t i c , BOD, and COD, but t o avoid c r e a t i n g new ones; t h i s w a s s u c c e s s f u l l y managed. There w a s no cont inuous l i q u i d d i scha rge except from washing the tomatoes, and t h i s is presen t commercial practice. In t h e 1976 Modified Caus t i c Pee l ing sys tem, t h e r e w a s a ca r ryove r of pee l ing a i d from t h e Pre- t r ea tmen t t o the Caus t i c App l i ca to r , and from t h e App l i ca to r t o the d i s c pee l remover. These ca r ryove r s were food-grade materials, n o t i n e d i b l e pee l ing a i d s n o r e f f l u e n t s . S ince 96% of t h e peel i s recovered as pulp , t h e normal p e e l e f f l u e n t was d r a s t i c a l l y reduced. It w a s reduced by f r a c t i o n a t i n g t h e 96% e d i b l e material from t h e 4% non-edible s k i n and seeds (from tomatoes d i s - i n t e g r a t e d dur ing process ing) . The s k i n , s e e d s , and f i b e r s s epa ra t ed by t h e E x t r a c t o r are normal process ing wastes. S ince t h e s e s k i n s and seeds have been r e - a c i d i f i e d , t hey are more accep tab le and i n smaller q u a n t i t y than the c u r r e n t c a u s t i c pee l f o r d i s p o s a l on a g r i c u l t u r a l l and o r i n t o a pub l i c s a n i t a r y l a n d f i l l s i te. extended p e r i o d s , and though BOD and COD measurements were made, t h e s e l i k e l y do no t r e p r e s e n t w h a t might be experienced under commercial cond i t ions .

The p re t r ea tmen t b a t h l i q u i d w a s no t opera ted f o r

Some canners c u r r e n t l y ope ra t e t h e i r c a u s t i c a p p l i c a t o r s t h e f u l l 3-mo. process ing season wi thout changing s o l u t i o n s ; o t h e r s change t h e c a u s t i c once a week. The pre t rea tment s o l u t i o n of oc t ano ic ( c a p r y l i c ) a c i d and water is b iodegradable , whereas some of t h e c u r r e n t pee l ing a i d s are not . A f t e r p e e l removal, a l l canners r i n s e o r flume t h e pee led tomatoes and t h i s p r a c t i c e wou.ld be una f fec t ed by modif ied c a u s t i c pee l ing . The re fo re , t h i s modif ied c a u s t i c pee l ing and p e e l recovery , wh i l e n o t a f f e c t i n g l i q u i d e f f l u e n t s , would decrease c u r r e n t p e e l s o l i d s d i scha rge by 96%, and t h e d i scha rge would have an improved pH c h a r a c t e r .

49

_____ Economics--The economics f o r a cannery-peel ing o p e r a t i o n of 40 t / h r are summarized i n Table 8. This assumed i n s t a l l a t i o n has t h e g e n e r a l f e a t u r e s of a p r o j e c t e d average s i t u a t i o n con ta in ing t h e components of t h e Modified Caus- t i c Pee l ing System. An a c t u a l i n s t a l l a t i o n , i n a s p e c i f i c cannery , w i l l vary accord ing t o a v a i l a b l e space , e x i s t i n g equipment, and product ion requi rements f o r tomato products . Such a pee l ing o p e r a t i o n might use two c a u s t i c app l i ca - t o r s , such as t h e FMC Hi-Ton, and e i t h e r two FMC PR-20 P e e l Removers, f o u r Magnuson Model C Pee l Scrubbers , o r e q u i v a l e n t d r y mechanical p e e l removers t h a t do no t add water t o t h e pee l . The c o s t s and v a l u e s shown are presented as an example and should be a d j u s t e d w i t h l o c a l d a t a . These c o s t s are based on 1976 in fo rma t ion , a 12% recove rab le p e e l , 60 days of o p e r a t i o n per y e a r , 16 hours of pee l ing each day , and a $50/ t p u l p va lue . c o s t s i s upward and i s expected t o cont inue up, t h e r e l a t i v e sp read between c o s t s and v a l u e i s expected t o remain about t h e same f o r t h e coming few years .

While t h e t r e n d of

C a p i t a l and ope ra t ing expenses i n c l u d e o n l y t h o s e d i r e c t l y a s s o c i a t e d wi th p re t r ea tmen t and pu lp r ecove ry , no t t h e ba l ance of t h e p e e l i n g process t h a t i s presumed t o a l r e a d y e x i s t . The c a p i t a l c o s t could e a s i l y be smaller o r g r e a t e r , depending on whether e x i s t i n g equipment and u t i l i t i e s are r e a d i l y ad'aptable o r e n t i r e l y new equipment would be needed. One example i s t h a t t h e p re t r ea tmen t could be a p p l i e d w i t h an e x i s t i n g flume t h a t i s conver ted t o h e a t e d , r e c i r c u l a t e d l i q u i d , o r i t might r e q u i r e a s p e c i a l t ank wi th con- t r o l l e d immersion t i m e f o r t h e tomatoes, such as t h a t used i n t h e p i l o t i n s t a l l a t i o n dur ing 1976.

There i s a s i g n i f i c a n t c o s t r educ t ion i n p e e l waste d i s p o s a l because 96% of t h e p e e l can be recovered as p u l p and only 4% remains as t r u e waste f o r d i s p o s a l . p e e l , and t h i s i s a minimum as t h e range i s $2.50 t o $5.00/ t . For t h e i n s t a l l e d C a p i t a l Equipment, a s i g n i f i c a n t p o t e n t i a l d i f f e r e n c e e x i s t s between t h i s estimate and a n a c t u a l i n s t a l l a t i o n . The amount of e lectr ical and p ip ing supply i n s t a l l a t i o n i s s u b j e c t t o e x i s t i n g f a c i l i t i e s ; f o r i n s t a n c e , i f a flume i s used f o r t h e p re t r ea tmen t w i th p e e l i n g a i d , a 50 hp e lec t r ic motor might be r e q u i r e d f o r a r e c i r c u l a t i o n pump, and such a load could r e q u i r e adding major e lec t r ica l power c a p a c i t y i n t h a t area. The ba lance of t h e f i x e d and v a r i a b l e c o s t s are f a i r l y p r e d i c t a b l e , but f o r each yea r a f t e r 1976, about 10% p e r yea r should be added as a n i n f l a t i o n f a c t o r .

A c o s t of $2 .50/ t was used f o r t h e c u r r e n t d i s p o s a l of c a u s t i c

The c a p i t a l c o s t s a s s o c i a t e d w i t h p e e l pu lp r ecove ry can p o t e n t i a l l y be recovered w i t h i n one year as i n d i c a t e d i n Table 8. The re fo re , t h e recovery of p e e l pulp appea r s t o be s e l f s u p p o r t i n g , hence economical ly v i a b l e and a t t r a c t i v e . pu lp recovery , t h e economic r i s k i s cons idered t o be l i m i t e d t o t h e recovery process .

S ince o t h e r p l a n t o p e r a t i o n s are n o t a f f e c t e d by

50

TABLE 8. PROJECTED ECONOMICS OF A COMMERCIAL INSTALLATION

___ Based on: 40 t / h r tomatoes x 1 2 % peel 1st Year 2nd Year

= 4.8 t / h r pee l 96% recovery Operation and = 4.608 t / h r pulp recovered. Thereaf te r 60 dy/yr x 16 hr /dy = 960 h r / y r -. ( $ /hr)- ($ /h r )

Recovered Peel-Pulp Value Based on $50/ t g r o s s va lue of pu lp . + 230.40 + 230.40

Fixed Cos t , i n s t a l l e d C a p i t a l Equipment Depreciated i n 1 y r , 960 hr .

Pretreatment ( c i r c u l a t i o n , temp. c o n t r o l ) - 15,000 Chemical Suppl ies ( t a n k s , pumps, p ip ing) - 16,000 Ex t rac t ion ( p u l p e r , p ip ing ) - 14,000 A c i d i f i c a t i o n (pH c o n t r o l , a g i t a t o r ) - 15,000 General ( u t i l i t i e s , p ip ing , e t c . ) - 35,000 Contingency - 20,000

( i n s t a l l e d t o t a l ) -115,000- - 119.79 0.00

Variab le Cos ts Direct Labor ( o p e r a t o r , c leanup, QC, supv.) - 12.48 S t a r t u p l a b o r , 1st year - 24.96 I n d i r e c t l a b o r (mechanic, c l e r k ) - 3.13

Super i n t endenc e - 0.94

-_____- - 40.57 - 15.61

- 0.94 - 0.94 U t i l i t i e s , steam, 7,230 l b / h r - 10.84

water, 10 gpm - 0.07 e l e c t r i c i t y , 78 kw - 1.57

Chemicals, f a t t y a c i d , 1.33 l b / h r - 1.33

Maintenance Suppl ies , 5%/yr of c a p i t a l - 5.99

- 12.48 - 12.48

I_ hydrochlor ic a c i d , 150 l b / h r - 6.00 - 7.33 - 7.33

- 5.99 - 5.99

- 1.00 - 1.00 Miscellaneous (ope ra t ing & cleanup suppl ies ) - 1 .OO

Value + $230.40 + $230.40 c o s t s NET RETURN O N PEEL PROCESSING Saving on Caus t i c Peel Disposal ($2.50/t)

OVERALL RETURN ON PEEL PROCESSING

- 188.10 - 43.35 + $ 42.30 + $187.05 + 12.00 + 12.00 + $ 54.30 + $199.05

o r o r $52,128.00 $191,088.20 1st year t h e r e a f t e r

51

REFERENCES

1. Schu l t z , W. G. , R. P. Graham, and M. R. Hart. Pulp recovery from tomato Proceedings of 6 t h Na t iona l Symposium on Food Processs ing p e e l r e s i d u e .

Wastes, Madison, Wisconsin, A p r i l 5-11, 1975.

2. H a r t , M. R., R. P. Graham, G. W. W i l l i a m s , and P. F. Hanni. Lye pee l ing of tomatoes us ing r o t a t i n g rubber d i s c s . Food Technology 28:38, 1974.

3. O s t e r t a g , R . , and K. Robe. Waterless p e e l removal. Food Process ing 36:60, Jan. 1975.

4.' S c h u l t z , W. G., R. P. Graham, W. C. Rockwell, J. L. Bomben, J. C. Miers, and J. R. Wagner. des ign . J. Food S c i . 36:397, 1971.

F i e l d process ing of tomatoes, P a r t 1 , p rocess and

5 . Miers, J. C . , J. R. Wagner, Nut t ing , M-D., W. G. S c h u l t z , R. Becker, H. J. Neumann, W. C. D i e t r i c h , and D. W . Sanshuck. F i e l d process ing of tomatoes, P a r t 2 , q u a l i t y and composition. J. Food Sc i . 36:400, 1971.

6. 38 FR 27076. Asbestos P a r t i c l e s i n Food and Drugs, Sept . 28, 1973.

7. 40 FR 26683-4. E l e c t r o y l t i c Diaphragm Process f o r S a l t , 1975.

8. Dahl, S. A. Chlo r -a lka l i c e l l f e a t u r e s new ion-exchange membrane. Chem. Engr. 82:17, 1975.

9. 21 CFR 113. s e a l e d c o n t a i n e r s , 1977.

Thermally Processed Low-acid Foods Packaged i n Hermet ica l ly

10. Horowitz, W i l l i a m (ed.) . t i o n of O f f i c i a l A n a l y t i c a l Chemists. AOAC, Washington, D.C., 11th ed. , 1970. p 560.

O f f i c i a l Methods of Ana lys i s of t h e Associa-

11. i b i d . p 560.

12. Na t iona l Canners Assn. sors , Vol. 2. pp 291 - 292.

Laboratory Manual f o r Food Canners and Proces- The A V I Pub l i sh ing Co., Inc . , Westport , Conn., 1968.

13. i b i d . p 341.

14. w. pp 294 - 296.

52

15.

16.

17.

18.

19.

20.

21.

22

23.

24.

25.

26.

27.

28.

29.

30.

31.

32.

f lorowitz , W. l o c . c i t . p 369.

i b i d . pp 769 - 771.

Assoc. Vitamin Chem. "Methods of Vitamin Assay", 3rd Ed., 1966. pp. 320-327,

i b i d . pp 332 - 338.

Food and Drug Adminis t ra t ion . P e s t i c i d e A n a l y t i c a l Manual, Vol. 1. U.S. Dept. of H E W , Washington, D.C., 1971 §212.13a(2).

Nat iona l Canners Assn. l o c . c i t . pp 300 - 316, 324 - 325.

3 5 FR 3651. Canned Tomato Puree (Tomato Pu lp ) , 1970.

Assoc. O f f i c . Agr. Chem. " O f f i c i a l Methods o f Ana lys i s , 448, 1960.

Spackman, D. H., W. H. S t e i n , and S. Moore. Automatic record ing 'apparatus f o r use i n t h e chromatography o f amino a c i d s . Anal. Chem. 30: 1190, 1958.

Wagner, J. R., and J. C. Miers. Consis tency of tomato products . Food Technology 21:920, 1967.

Horowitz, W. l o c . c i t . pp 777-778.

21 CFK 173.315. P e e l i n g of F r u i t s and Vegetab les , 1977.

Chemicals Used i n Washing o r t o Assist i n t h e Lye

21 CFR 172.860. F a t t y Acids, 1977.

42 FR 30390-1. Capry l i c Acid, 1977.

J o s l y n , M. A. "Methods of Food Analysis" , Academic Press, 1950. pp 455-56.

USDHEW, P u b l i c Heal th S e r v i c e , Food and Drug Adm., HFF-342, Washington, D.C. 20204. "The Food Defect Act ion Levels", 11-12, August 1977.

Method of Pee l ing F r u i t s and Vegetab les wi th Carboxyl ic Acids , SN 714, 229. Nat iona l Technica l Informat ion S e r v i c e , U.S. Department of Commerce, 425 T h i r t e e n t h S t . , NW, Washington, D. C. 20204.

Amoore, J. E. , D. Venstrom-, and A. R. Davis. Measurement of S p e c i f i c Anosmia. Pe rcep tua l and Motor S k i l l s . 26: 143-164, 1968.

33. Kohler , G. O., and Pal ter R. S t u d i e s on methods f o r amino a c i d a n a l y s i s of wheat products . Cereal Chem. 44:512, 1967.

34. Mar t in , J. T . , and B. E. J u n i p e r . "The C u t i c l e s of P lan ts" . Arnold Publ . , 1970.

53

35. Beaman, D. R. , F. P. Boer, C. T. Lichy, R. J. Moolenaar, F. W . S p i l l e r s , 0. C. Tay lo r , and D. M. Young. Abestos i n Water i n t h e Chlor-Alkali Indus t ry . The Chlorine I n s t i t u t e , 17 th Ch lo r ine P l a n t Managers' Seminar, New Orleans, Lou i s i ana , February 5, 1975.

54

BIBLIOGRAPHY

29 FR 7909 Grades of Canned Tomatoes, Ju ly 24, 1969.

21 CFR 155.190(a) -.190(b), -.19O(c) -.191, -.192, and -.194. Standards of I d e n t i t y - Canned Tomatoes, Tomato Paste, Tomato Puree, Catsup, 1977.

U.S.D.A. “Composition of Foods’’, Agr i cu l tu re Handbook No. 8. U.S. Govern- ment P r i n t i n g Of f i ce , Washington, D. C. , 1963.

Wilson, L., and S t e r l i n g , C. S tud ie s on t h e C u t i c l e of Tomato F r u i t . Z e i t s c h r i f t f u r Planzenphysiologie, Vol. 7 7 , pp. 359-371, 1976.

42 P R 10004-10009. Grades, 1977.

Canned Tomatoes, proposed United S t a t e s Standards f o r

42 FR 1000-100013. Canned Stewed Tomatoes, proposed United S t a t e s Standards f o r Grades, 1977.

55

APPENDIX A

Vitamin A A c t i v i t y Method*

Reagents

Acetone: Dry, a l coho l - f r ee reagent grade. Petroleum E the r : Adsorbent: mix f o r 1-2 hours 1+1 a c t i v a t e d magnesia (MgO from Merck Co.,

Rahway, New J e r s e y ) and Hyflo Super-Cel (diatomaceous e a r t h from F i sche r S c i e n t i f i c Company, F a i r Lawn, New J e r s e y ) .

r e d i s t i l l i n a l l - g l a s s a p p a r a t u s c o l l e c t 60-70" f r a c t i o n

E x t r a c t i o n

Work i n subdued l i g h t . Weigh 10-50 grams sample i n t o b lender cup.

amount of I n t e r n a t i o n a l Un i t s per 100 grams sample: less than 100 t o 200 I . U . / l O O g. needs 50 grams sample, 200 t o 1000 I.U./lOO g. needs 25 grams sample, and more than 1000 I L U . / l O O g . needs 5-10 grams sample.

Sample s i z e depends on

Add 200 ml 50:50 petroleum e the r : e thano l . Add approximately 2 grams F i l t e r through f a s t f low f i l t e r a i d .

Whatman f i l t e r paper on Buchner funnel i n t o 500 m l Erlenmeyer f l a s k connected t o vacuum. funnel .

Blend a t high speed f o r 5 minutes.

Rinse b lender cup with water and then with petroleum e t h e r i n t o

Trans fe r f i l t r a t e t o 500 m l s epa ra to ry funne l r i n s i n g f i r s t w i th petroleum e t h e r t h e n wi th water.

Scrape r e s idue from f i l t e r paper back i n t o b lender cup. Add 100 m l Blend a t medium speed f o r t h r e e minutes . 50:50 petroleum e the r : e thano l .

F i l t e r c o n t e n t s from second blending through same f i l t e r paper i n t o same 500 m l Erlenmeyer f l a s k . same manner u n t i l c lear , each t i m e t r a n s f e r r i n g f i l t r a t e q u a n t i t a t i v e l y t o s e p a r a t o r y funne l .

I f f i l t r a t e i s co lo red r e - e x t r a c t i n t h e

Drain water l a y e r i n s e p a r a t o r y f u n n e l t o an Erlenmeyer f l a s k . Swir l v igo rous ly wi th 50 m l petroleum e t h e r . Drain and d i s c a r d water l a y e r . u n t i l water l a y e r i s c l e a r , about f i v e times.

sodium s u l f a t e i n t o a p p r o p r i a t e s i z e beaker .

Add back t o s e p a r a t o r y funnel . Wash f i l t r a t e w i th 100 m l p o r t i o n s of water

Swi r l w i th a r o t a r y motion. .Drain off as much water as poss ib l e . F i l t e r through 10 grams anhydrous

Rinse s e p a r a t o r y funne l and

*For r e g u l a r tomato materials @pH 4.0 t o 4.5.

56

sodium s u l f a t e w i th 50 m l petroleum e t h e r i n t o beaker . Evaporate e x t r a c t t o 50-25 ml under w a r m a i r i n hot water ba th .

Chromatographic tube should be 175 mm long wi th a n o u t e r d iameter of A r e s e r v o i r f o r ho ld ing 22 mm and a c o n s t r i c t i o n a t t h e bottom of 10 mm.

e l u a n t ( s o l v e n t ) a t t h e t o p i s convenient .

Plug base of t ube wi th g l a s s wool. Add l o o s e adso rben t t o 15 cm depth. Apply vacuum and tamp w i t h t i g h t f i t t i n g rod t o 7 cm depth making s u r e sur - f a c e i s f l a t . Add 0.5 cc anhydrous sodium s u l f a t e .

E l u t i o n

Pre-wet column wi th petroleum e t h e r . Adjust f low rate t o 2-3 drops per second by a i r p r e s s u r e from above. Do n o t l e t column go dry. T rans fe r e n t i r e e x t r a c t t o column. Load by r i n s i n g beaker and r e s e r v o i r w i th small p o r t i o n s of petroleum e t h e r j u s t as e x t r a c t h a s reached about 1 c m above column.

E l u t e f i r s t c a r o t e n e band wi th 5% ace tone i n petroleum e t h e r . C o l l e c t i n graduated c y l i n d e r . E l u t e second xan thophy l l band wi th 10% ace tone i n petroleum e t h e r and c o l l e c t i n graduated c y l i n d e r .

C a l i b r a t i o n of SDectroDhotometer

s l i t

Standard Stock So lu t ion : 1.0 mM d r y c r y s t a l l i n e 1-(Phenylazo)- 2-napthol (C.I. Solvent Yellow; Sudan I) t o c o n s t a n t weight i n 70°F vacuum oven. Disso lve 0.1241 g i n 500 m l acetone-isopropanol (1 + 1). S t o r e i n dark.

Working So lu t ion : 0.04 mM D i l u t e 20 m l s t o c k s o l u t i o n t o 500 m l w i t h ace tone- i sop ropano l (1 + 1). S t o r e i n dark.

Working s o l u t i o n should read 0.460 a t 436 my and 0.561 a t 474 my wi th width of 0.03. The ins t rument d e v i a t i o n f a c t o r , f , i s t h e r a t i o of t h e

t h e o r e t i c a l absorbance t o t h e a c t u a l . Assume that t h e working s o l u t i o n of dye has t h e same A as 2.35 mg ca ro tenes per l i t e r a t 436 mp and 2.38 mg xanthophyl l s per l i t e r a t 474 mp.

R e a d ' f i r s t band a t 436 my and second band a t 474 my.

57

C a l c u l a t i o n

Carotenes

I . U . / l O O g = A436 x f x f i n a l volume x 1667 x 100 196 x g on column x b

where f = ins t rument d e v i a t i o n f a c t o r , 1667 = i n t e r n a t i o n a l u n i t s v i tamin A a c t i v i t y p e r gram, and 196 = t h e e x t i n c t i o n c o e f f i c i e n t (A = .460/2.35 mg ca ro tenes per l i t e r ) , and b = c e l l l e n g t h i n cm.

Xanthophyl ls

I . U . / l O O g - A474 x f x f i n a l volume x 1667 x 100 236 x g on column x b x 2

The a c t i v i t y i s d iv ided by two s i n c e t h i s group of ca ro teno ids have about 50% b i o l o g i c a l a c t i v i t y .

Reference: AOAC 39,014 - 39,023, Eleventh E d i t i o n , 1970.

58

APPENDIX B

Photometr ic Determina t ion of Anionic P e e l i n e Aids*

[Sodium 2-ethylhexyl s u l f a t e and sodium mono- and d i - m e t h y l naphtha lene s u l f o n a t e ]

S o l u t i o n s and Chemicals

1. 2. Methylene B l u e I n d i c a t o r .

Chloroform (Spec t rophotometr ic and Technica l g r a d e ) .

0.03 grams Methylene B l u e (N. F. Powder). 12.00 grams Concentrated S u l f u r i c Acid (ACS). 20.00 grams Sodium S u l f a t e (anhydrous) ACS. Disso lve t h e above i n g r e d i e n t s t o 1 l i t e r w i t h de ion ized water ( d e t e r g e n t f r e e ) . E x t r a c t i n a 1 l i t e r s e p a r a t o r y f u n n e l by shaking wi th Techn ica l grade Chloroform u n t i l t h e Chloroform l a y e r does not show any v a r i a t i o n when compared t o an a l i q u o t of Technica l g rade a t 600 wavelength.

3. Deionized water ( d e t e r g e n t f r e e ) . 4 . S u l f u r i c Acid 5N.

D i l u t e 140 m l of Conc. S u l f u r i c Acid (ACS) t o a l i t e r wi th de ion ized wa te r ( d e t e r g e n t f r e e )

Apparatus

I. Volumetric flasks-100 m l . 2. Volumetric p i p e t t e s - 1, 2, 4 , 5, 10, 20 m l . s i z e s . 3. Separa to ry f u n n e l , 250 m l & 1 l i ter . 4. 30 m l screw cap tes t tubes . 5. Photometer capab le of measuring a t 600 mv.

Procedure

P i p e t t e 5 m l . of c a u s t i c peel sample i n t o a 100 m l vo lumet r i c f l a s k and

Add 5 m l of f i l l w i t h de ion ized water ( d e t e r g e n t f r e e ) t o t h e mark, shake and p i p e t t e 5 m l of t h i s d i l u t e d s o l u t i o n i n t o a 250 m l s e p a r a t o r y funne l . 5 N s u l f u r i c Acid and 20 m l of Techn ica l g rade ch loroform, s t o p p e r f u n n e l , and shake f o r one-half minute. Permit time f o r the chloroform l a y e r t o separate and d i s c a r d . Add ano the r 20 m l of ch loroform, s t o p p e r f u n n e l , and shake f o r one-half minute. P e r m i t t i m e f o r t h e chloroform l a y e r t o

*Modif ica t ion of a methods pub l i shed by I n t e r c o n t i n e n t a l Chemical Co., P.O. Box 15318, Sacramento, CA 95813 and Union Carb ide Inc. , 270 Park Ave., New York, NY 10017.

59

¶

separate and d i s c a r d . Add 20 m l of Methylene Blue s o l u t i o n and 20 m l of Spectophotometr ic g rade chloroform t o a s e p a r a t o r y f u n n e l , shake f o r one f u l l minute and a l l o w l a y e r s t o s e p a r a t e a s b e f o r e . Very c a r e f u l l y draw o f f t h e chloroform l a y e r i n t o a 30 m l screw cap tes t tube. form t o Photometric Cuvette and measure the o p t i c a l d e n s i t y a t 600 mp.

T r a n s f e r chloro-

To e s t a b l i s h a s t a n d a r d i z a t i o n c u r v e , make s o l u t i o n s c o n t a i n i n g e x a c t l y 0, 5 , 10, 20, 30, 4 0 , 50 ppm of p e e l i n g a i d and analyze acco rd ing t o t h e out- l i n e d p rocedure , o m i t t i n g t h e Techn ica l g r a d e chloroform s t e p s . In a graph, p l o t ppm of c o n c e n t r a t i o n of p e e l i n g a i d a g a i n s t t h e o p t i c a l d e n s i t y as t h e examples i n F igu re B-1.

60

0.7

0.4

0.5 * c v) -

0.4 n

Q\ 2 0.3 c1

c 8

SODIUM 2-ETHYLHEXYL SULFATE - AT 600 m p WAVE LENGTH (TYPICAL STANDARDIZATION CURVE) -- TOMATO SAMPLE, 10% TS

- - AQUEOUS STD

-

0-

MONO- AND DI-METHYL NAPHTHALENE SULFONATES AT 6 4 5 m p WAVE LENGTH

0.2 -

-- TOMATO SAMPLE, 10% TS 0.1 - AQUEOUS STD

1 I I I I I I I 5 2 0 25 3 0 35 4 0 45 0 5 10 15 0

PEELING AID, AS 100% ACTIVE INGREDIENT (PPM)

I

k

Determinat ion of F a t t y Acids i n Processed Tomato Products .

Ana l y t ica 1 Procedure

P r i n c i p l e

Th i s method involves t h e e x t r a c t i o n of f a t t y a c i d s (and t h e i r s a l t s ) from processed tomato products and t h e format ion of t h e i r p ropyl esters f o r t h e i r q u a n t i t a t i v e de t e rmina t ion by gas l i q u i d chromatography. This method i s a p p l i c a b l e t o the a n a l y s i s of C 6 t o C have been t r e a t e d wi th such materials dur ing t h e i r p rocess ing ( p e e l i n g ) .

f a t t y a c i d s i n tomatoes t h a t 10

This procedure d e f i n e s t h e chromatographic r e t e n t i o n t i m e and response of t h e propyl esters of hexanoic ( c a p r o i c ) a c i d , hep tano ic ( enan th ic ) a c i d , oc t ano ic ( c a p r y l i c ) a c i d , nonanoic (pe l a rgon ic ) a c i d , and decanoic ( c a p r i c ) ac id . The r e s i d u e of any one o r more of t h e s e f a t t y a c i d s i s c a l c u l a t e d on the b a s i s of t he a r e a of t h e peak(s) i n t h e sample e x t r a c t r e p r e s e n t i n g the f a t t y a c i d i n ques t ion . f a t t y a c i d ( s ) p re sen t i n the sample, s i n c e the area of t h e propyl e s t e r ( s ) of t h e r e s idue i s compared t o t h e area of t h e propyl e s t e r of a similar f a t t y a c i d t h a t i s added t o the sample as an i n t e r n a l s t anda rd .

This procedure r e q u i r e s p r i o r knowledge of t h e

Apparatus

1. E x t r a c t i o n equipment: a . 60 m l and 250 m l s e p a r a t o r y funne l s . b. 25 and 50 m l g radua te s . c. 50 m l b o i l i n g f l a s k , 2 4 / 4 0 t a p e r j o i n t . d. 300 mm West condenser w i th 2 4 / 4 0 t a p e r j o i n t s . e. steam bath. f . 250 m l c e n t r i f u g e b o t t l e s . g . c e n t r i f u g e . h. 10 m l vo lumetr ic f l a s k s o r o t h e r v e s s e l s w i th g l a s s s toppe r s . i. 10 m l beakers . j . k. P i p e t s : 1 m l , 2 m l , 5 m l .

Pas t eu r t r a n s f e r p i p e t s and bulb.

2. Gas chromatographic ins t rument wi th t h e fo l lowing minimal charac-

Column oven opera ted wi th tempera ture programmed between 80°C and 170"C, a t a ra te of 2" t o 5" rise p e r minute. Sample i n j e c t i o n po r t wi th h e a t e r c h a r a c t e r i s t i c necessary f o r o p e r a t i n g about 85°C h ighe r than t h e maximum necessary column oven temperature ( 2 5 5 "C) .

teris t ics : a .

b.

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c. De tec to r of t h e flame i o n i z a t i o n type. If s e p a r a t e l y thermo- s t a t e d , i t should be maintained a t 255-265°C.

d. Column, 8- lof t l ong , 1/8 inch o u t s i d e d i ame te r , made of s t a i n - less s tee l o r g l a s s , packed with 10% by weight FFAP l i q u i d phase on 60-80 mesh a c i d washed DMCS Chromosorb W.

e. Recorder, 1 t o 100 mv range , 1-sec. f u l l scale d e f l e c t i o n with a c h a r t speed of 1 mm per minute and a n a t t e n u a t o r swi t ch t o change t h e r e c o r d e r range r equ i r ed . The r e c o r d e r should be equipped wi th a n i n t e g r a t o r i f p o s s i b l e .

f . Helium, n i t r o g e n , o r argon; minimum p u r i t y 99.95 mol %. g. Hydrogen, minimum p u r i t y 99.95 mol %. h. A i r , d r y , dew po in t -75°F max.

3. Syringe (1 m i c r o l i t e r ) f o r sample i n j e c t i o n .

Reagents

1.

2 .

3.

4.

5.

6.

7.

8.

Reagent P u r i t y . Reagent g rade chemica ls s h a l l be used i n a l l tests. Unless o the rwise i n d i c a t e d , i t i s in t ended that a l l rea- g e n t s s h a l l conform t o the s p e c i f i c a t i o n s of t h e Committee on A n a l y t i c a l Reagents of t h e American Chemical S o c i e t y , where such s p e c i f i c a t i o n s are a v a i l a b l e . Other g r a d e s may be used provided i t i s f i r s t a s c e r t a i n e d t h a t t h e r e a g e n t i s of s u f f i c i e n t l y h igh p u r i t y t o permit i t s use without l e s s e n i n g t h e accuracy of t h e de t e rmina t ion .

Chlorof o m .

Boron T r i f l u r o i d e - propanol (14% w/v). (Applied Sc ience Labs, Inc. , *S ta t e Col lege , PA 16801).

S t o r e i n r e f r i g e r a t o r .

6 N - Hydrochlor ic Acid.

S a t u r a t e d s o l u t i o n of ammonium s u l f a t e .

Anhydrous sodium s u l f a t e .

I n t e r n a l Standard. Use heptanoic a c i d when ana lyz ing f o r hexanoic o r o c t a n o i c ac id . Use decanoic a c i d when ana lyz ing f o r nonanoic a c i d o r a mixture of c6 t o C9 f a t t y a c i d s t h a t i n c l u d e heptanoic a c i d . Standard s o l u t i o n should be prepared i n chloroform.

Standard Mixture of F a t t y Acids. Q u a n t i t a t i v e l y p r e p a r e a mixture of t h e f a t t y a c i d s t o be analyzed i n approximate ly e q u a l amounts, i nc lud ing t h e f a t t y a c i d chosen as t h e i n t e r n a l s t a n d a r d , e .g . , about 2 mg of each f a t t y a c i d i n a t o t a l of 2 m l chloroform.

Procedure -- 1. E x t r a c t i o n

a. For samples of tomato pulp wi th expec ted f a t t y a c i d r e s i d u a l s

63

b. C.

d.

e.

f .

g *

h.

i.

j -

k.

of up t o about 150 ppm, weight a c c u r a t e l y about 40 grams of pu lp i n t o a 250 m l s e p a r a t o r y funne l . For l a r g e r r e s i d u a l s use a p r o p o r t i o n a t e l y smaller sample s i z e . Acid i fy wi th 1 m l 6N HC1. Add about 130 m l chloroform and an a c c u r a t e l y measured amount of i n t e r n a l s t a n d a r d (ca 3 mg, p r e f e r a b l y a s a n a l i q u o t from a s t anda rd s o l u t i o n prepared wi th ch loroform) . Mix thoroughly f o r about 2 minutes. I f n e c e s s a r y , t r a n s f e r t o a 25 ml c e n t r i f u g e b o t t l e and c e n t r i f u g e s u f f i c i e n t l y t o break any emulsion t h a t forms; t hen t r a n s f e r t o t h e o r i g i n a l s e p a r a t o r y funne l . Remove t h e chloroform e x t r a c t ( lower phase) t o ano the r 250 m l s e p a r a t o r y f u n n e l . Add 20 m l 0.5N NaHC03 and mix thoroughly t o e x t r a c t f a t t y a c i d s from chloroform. Allow phases t o s e p a r a t e and d i s c a r d chloroform ( lower phase) ; i f necessa ry , c e n t r i f u g e . Acid i fy wi th 2 m l 6N HC1. Mix thoroughly u n t i l e f f e rvescence s t o p s . I f necessa ry t o improve p u r i t y of t h e e x t r a c t , r e p e a t s t e p s ( c ) t o ( h ) , u s ing 5 ml i n chloroform i n s t e p ( c ) and 5 m l 0.5N NaHC03 i n s t e p ( f ) and 0.5 m l 6N H C 1 i n s t e p ( h ) i n a s m a l l s e p a r a t o r y funnel . Do n o t add more s t anda rd when r e p e a t i n g e x t r a c t i o n . T rans fe r a c i d i f i e d aqueous phase t o 60 m l s e p a r a t o r y funne l and e x t r a c t f a t t y a c i d s wi th 2 m l chloroform. Trans fe r chloroform e x t r a c t ( lower phase) t o a 10 m l beaker con ta in ing 0.4 g anhydrous Na2S04.

2. Ester format ion

a. Decant t h e clear chloroform e x t r a c t i n t o a 50 m l b o i l i n g

b. Add 2 m l of boron t r i f l u o r i d e (14% w/v) propanol reagent . c. Reflux on steam ba th f o r 15 minutes . d. Cool t o room temperature; add 5 m l s a t u r a t e d ammonium s u l f a t e

s o l u t i o n and mix throughly. T r a n s f e r t o 60 ml s e p a r a t o r y funne l and a l l o w phases t o s e p a r a t e .

e. Discard lower (aqueous) phase , and w i t h a P a s t e u r p i p e t t r ans - f e r o rgan ic phase t o a 10 m l g lass -s toppered f l a s k con ta in ing about 0.4 g anhydrous Na2S04.

f l a s k .

f . R e f r i g e r a t e u n t i l chromatographic a n a l y s i s .

3. C a l i b r a t i o n

a. P repa re t h e propyl esters of t h e s t anda rd mixture of t h e f a t t y a c i d s by us ing 2 m l o f a chloroform s o l u t i o n of t h e f a t t y a c i d s ( c a . 2 mg each) i n s t e p ( a ) of ester formation. Complete s t e p s b-f of ester format ion as f o r sample e x t r a c t s .

b. Chromatograph t h e ester s o l u t i o n and a d j u s t t h e chromatogra- p h i c c o n d i t i o n s such t h a t t h e r e are s u i t a b l e r e t e n t i o n times and good r e s o l u t i o n of t h e f a t t y - a c i d propyl esters.

64

I

C. Techniques p e r t a i n i n g t o column c o n d i t i o n i n g , s e l e c t i o n of car r ie r gas f low rates , peak r e s o l u t i o n , s e n s i t i v i t y s e t t i n g s , sample i n j e c t i o n , and a t t e n u a t i o n c o n t r o l , e tc . , should be p a t t e r n e d a f t e r ASTM Method D 1983-69, AOCS Method Ce 1-62 o r any o t h e r method s u i t a b l e f o r t h e de t e rmina t ion of f a t t y a c i d esters, inc lud ing those sugges ted by t h e in s t rumen t manu- f a c t u r e r .

e s te r r e l a t i v e t o that of t h e chosen i n t e r n a l s tandard . The d e t e c t o r response f o r esters of f a t t y a c i d s of similar mole- c u l a r weight should be ve ry similar. For a l l p r a c t i c a l purposes , t h e r e l a t i v e d e t e c t o r response f o r a d j a c e n t peaks (e.g. , C 7 and c8 f a t t y a c i d propyl e s t e r s ) may be assumed t o be i d e n t i c a l . The re fo re , i t i s p r e f e r a b l e t o use hep tano ic a c i d as a n i n t e r n a l s t anda rd f o r a s say ing oc tano ic a c i d .

d. Determine the d e t e c t o r response f o r each f a t t y - a c i d propyl

4 . Chromatographic a n a l y s i s

a . Once t h e optimum chromatographic c o n d i t i o n s have been esta- b l i s h e d ( s e e c a l i b r a t i o n ) , chromatograph t h e propyl esters of t h e sample e x t r a c t , which i n c l u d e s a n i n t e r n a l s t anda rd of f a t t y a c i d (e .g . , heptanoic a c i d ) .

i n t e r n a l s t anda rd peak i n t h e chromatograph o f t h e sample e x t r a c t .

response c h a r a c t e r i s t i c s of each propyl ester.

h a l f h e i g h t o f each peak i n o r d e r t o estimate i t s area.

b. I d e n t i f y t h e f a t t y a c i d propyl e s t e r ( s ) peak(s ) and t h e

c. I n t e g r a t e on ly t h e s e peaks, c o r r e c t i n g f o r t h e d e t e c t o r

d. I f no i n t e g r a t o r i s used, measure t h e he igh t and wid th a t

e. C a l c u l a t e t h e r e s i d u e of each f a t t y a c i d as fo l lows:

f a t t y a c i d r e s i d u e , ppm = Ra 5 x 10 6 , W

where Ra = r a t i o of t h e s u b j e c t peak area t o t h e i n t e r n a l s t anda rd peak area

S = weight of i n t e r n a l s t anda rd i n grams W = weight of tomato sample i n grams

5. I n t e r f e r e n c e

Ana lys i s of tomatoes n o t t r e a t e d wi th f a t t y a c i d s may show s m a l l amounts of v a r i o u s n a t u r a l l y occur r ing compounds wi th r e t en - t i o n t i m e s s imilar t o those of t h e c6 t o C l 0 f a t t y a c i d propyl esters. I n d i v i d u a l l y , t h e s e u s u a l l y amount t o less than 1 ppm ( f a t t y - a c i d e q u i v a l e n t ) , and ve ry o f t e n they can be d i f f e r e n t i a t e d from t h e peaks of t h e esters be ing analyzed. I f t h e f a t t y a c i d used i n process ing t h e tomatoes h a s a n impur i ty similar t o t h e f a t t y a c i d used as t h e i n t e r n a l s t a n d a r d , t h e r e s u l t s (compared a g a i n s t t h e s t anda rd ) w i l l be s l i g h t l y low.

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TECHNICAL REPORT DATA (Please read Instmctzons on the reverse before completing)

. REPORT NO. 12. 13. RECIPIENT'S ACCESSION NO.

EPA- 600 /' 2 - 7 8- 2 0 2 ____I

5. REPORT DATE . TITLE A N D SUBTITLE

C, 02 P E , i 1 AL YEAS I C I L I TY OF RECOVERING TOMATO September 1978 i s s u i n g d a t e PROCESSTNG EESIDUALS FOR FOOD USE 6. PERFORMING OR(

AUTHOR(S) 8. PERFORMING ORGANIZATION REPORT N O :?. G . S c h u l t z , 11. J . Xeumann, J . E . Schade, J . F . Norgan, P. F. Hanni, A . ?I . Latsuyama & H. Maagdenberg

USDA, Western Regional Research Center

Na t iona l Food P rocesso r s A s s o c i a t i o n , Western Research

10. PROGRAM ELEMENT NO. . PERFORMING ORGANIZATION NAME A N D ADDRESS

1BB610 Albany, CA, and 11. CONTRACT/GRANT NO.

Laboratory, Berkeley, CA EPA-IAG-D5-0795 2. SPONSORING AGENCY NAME A N D ADDRESS I n d u s t r i a l Environmental Research Lab. - Cinn, OH FINAL REPORT 5/75-8177 O f f i c e of Research and Development

13. TYPE O F REPORT A N D PERIOD COVERED

14. SPONSORING AGENCY CODE

U.S. Environmental P r o t e c t i o n Agency C i n c i n n a t i . Ohio 45268 1 EPA/600/12

I

5. SUPPLEMENTARY NOTES

6. ABSTRACT A 2-year p r o j e c t w a s undertaken t o determine t h e commercial f e a s i b i l i t y of r ecove r ing p u l p from t h e p e e l i n g s of c a u s t i c pee led tomatoes. cannery o p e r a t i o n s w a s processed through a 20-gpm (5 t / h r ) continuous-flow l i n e . This process ing c o n s i s t e d of a c i d i f y i n g t h e p e e l t o PI.! 4.2 wi th food-grade hydro- c h l o r i c a c i d , then s e p a r a t i n g t h e pu lp from t h e s k i n w i t h a padd le f i n i s h e r ( s c r e e n ) . Recovered p e e l pu lp w a s found t o be of food q u a l i t y bu t con ta ined h igh pee l ing -a id r e s i d u e s (150-450 ppm). Pee l ing a i d s i n c u r r e n t u se are approved f o r p e e l i n g b u t n o t as a d d i t i v e s t o t h e f i n a l product . a cannery t o s tudy m o d i f i c a t i o n s i n t h e p e e l i n g p rocess f o r t h e purpose of r educ ing pee l ing -a id r e s i d u e i n t h e recovered pulp. t h e tomatoes by immersion i n a 150'F aqueous b a t h (approximately pIi 3 .6) c o n t a i n i n g about 0 .15% food-grade o c t a n o i c ( c a p r y l i c ) a c i d ; subsequen t ly , t h e tomatoes were immersed i n c a u s t i c . m e t USDA Q u a l i t y Grade A , and t h e o c t a n o i c a c i d levels were low (0 t o 30 ppm). proposed u s e of t h i s recovered p e e l pu lp i s i n combination w i t h tomato pu lp from r e g u l a r sou rces f o r canned p roduc t s such as tomato sauce , c a t s u p , p a s t e , and f i l l j u i c e f o r pee led tomatoes.

I n 1975, p e e l from r e g u l a r

I n 1976, a l - t / h r p i l o t p e e l i n g l i n e w a s set up a t

The p r i n c i p a l m o d i f i c a t i o n w a s t o p r e t r e a t

The p e e l w a s removed w i t h rubber-disc p e e l e r s . Recovered pu lp The

Economic a n a l y s i s i n d i c a t e s an a t t r a c t i v e R O I .

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7 . K E Y WORDS A N D DOCUMENT ANALYSIS

DESCRIPTORS

Food Process ing Canning Byproducts Economic Ana lys i s -.

8. DISTRIBUTION STATEMENT

RELEASE TO PUBLIC

;ANI~ATION CODE

i.IDENTIFIERS/OPEN E N D E D TERMS IC. COSATI Field/Group

Tomato P e e l Pulp Recovery 68D

19. SECURITY CLASS (ThisReport)' 121. NO. OF PAGES

UNCLASSIFIED 78 122. PRICE '0. SECURITY CLASS (This page)

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