extraction of a pharmaceutical jelly from avocado

MOI UNIVERSITY

EXTRACTION OF A PHARMACEUTICAL JELLY FROM

AVOCADO PULP

A Design Project Presented to the

DEPARTMENT OF CHEMICAL AND PROCESS ENGINEERING

SCHOOL OF ENGINEERING

In partial fulfillment of the requirements for the award of Bachelor of Engineering in

Chemical & Process Engineering

Moi University

DIAR ELIJAH GARANG CPE/1021/08

JOAKIM KISUA PIUS CPE/09/08

SUPERVISOR

Dr. Menzwa

i

DECLARATION

We declare that this project entitled Extraction of pharmaceutical jelly from avocado

pulp is the result of our own research except as cited in the references. The report has

not been accepted for any degree and is not concurrently submitted in candidature of

any other degree.

Signature: .

Name of candidate: DIAR ELIJAH GARANG (CPE/1021/08)

Signature: .

Name of Candidate: JOAKIM KISUA PIUS (CPE/09/08)

DATE: 21st May, 2013

ii

ACKNOWLEDGEMENT

We would like to thank the Almighty for the strength, inspiration and encouragement

given to us throughout the completion of this project without any obstacle. A lot of

experiences and knowledge has been gained along the way.

We wish to express our sincere appreciation to our supervisor, Dr. Menzwa, for his

critic, advice, motivation, friendship and input of ideas, relentless support, guidance and

endless encouragement throughout our entire project

We are also very thankful to our parents for their support and motivation. Without their

endless support and interest, this project would not have been same as presented here.

Unfortunately it is not possible for us to list all those involved in this limited space. We

are therefore grateful to everybody that was involved directly or indirectly in helping us

to complete this project.

iii

ABSTRACT

Avocado fruit is one valuable tropical produce which is highly utilized in Kenya and

even in most of African countries only on the nutritious aspect. This is due to the proven

presence high content of positive effects on lowering total blood cholesterol, controlling

weight and providing humans with essential nutrients and vitamins. Various studies

have also proven high content of tocopherols (vitamin E) and antioxidants in

unsaponifiable fraction in avocado oil which can help to hail skin ailments. Cosmetic

industries have taken up these studies positively and they have been producing

cosmetic products for years. However pharmaceutically, much attention has not been

paid to get high concentration of this unsaponifiable fraction so as it could be used to

treat skin ailments. However, this project will be targeting un-saponifiable fraction of

the oil obtained from molecular distillation which is in the light components of the

fractionated oil. During the molecular distillation, substantial amount of unsaponifiable

fraction is achieved in the light component. Process operating conditions (temperature

and pressure) are chosen so that much of this unsaponifiable fraction is obtained in the

light components without interfering with the desired pytochemicals.

iv

TABLE OF CONTENTS

DECLARATION --------------------------------------------------------------------------------------------- i

ACKNOWLEDGEMENT ---------------------------------------------------------------------------------- ii

ABSTRACT ------------------------------------------------------------------------------------------------ iii

LIST OF TABLES --------------------------------------------------------------------------------------- viii

LIST OF FIGURES -------------------------------------------------------------------------------------- viii

CHAPTER ONE -------------------------------------------------------------------------------------------- 1

1.0 Introduction -----------------------------------------------------------------------------------------------------------1

1.1Objectives of the Design project ----------------------------------------------------------------------------------2

CHAPTER TWO ------------------------------------------------------------------------------------------- 3

2.1: Literature review ----------------------------------------------------------------------------------------------------3

2.2: Historical Origin of the Plant--------------------------------------------------------------------------------------3

2.3: Agronomy -------------------------------------------------------------------------------------------------------------3

2.3.1: Growth Requirements ----------------------------------------------------------------------------------------3

2.3.2: Fertilization------------------------------------------------------------------------------------------------------4

2.3.3: Avocado Fruit & Human Health ----------------------------------------------------------------------------6

CHAPTER THREE --------------------------------------------------------------------------------------- 20

3.0: JUSTICATION -------------------------------------------------------------------------------------------------------- 20

CHAPTER FOUR ----------------------------------------------------------------------------------------- 21

4.0: PROCESS DESCRIPTION ------------------------------------------------------------------------------------------ 21

4.1 Pre-process treatment -------------------------------------------------------------------------------------------- 21

4.2 Extraction process-------------------------------------------------------------------------------------------------- 21

4.3 Preheating ----------------------------------------------------------------------------------------------------------- 21

BLOCK DIAGRAMS------------------------------------------------------------------------------------------------------- 28

CHAPTER FIVE ------------------------------------------------------------------------------------------ 31

5.0: MASS AND ENERGY BALANCES -------------------------------------------------------------------------------- 31

5.1.1: Mass balance ------------------------------------------------------------------------------------------------- 31

5.1.2: ENERGY BALANCE ----------------------------------------------------------------------------------------------- 37

CHAPTER SIX -------------------------------------------------------------------------------------------- 40

6.0 EQUIPMENT SELECTION, SIZING AND SPECIFICATION ---------------------------------- 40

6.1 CHOICE OF MATERIALS FOR EQUIPMENT FABRICATIONS ----------------------------- 40

CHAPTER 7 ---------------------------------------------------------------------------------------------- 44

7.0 Design of a centrifugal separator by DIAR ELIJAH GARANG CPE/1021/08 -------- 44

v

7.0.1 INTRODUCTION -------------------------------------------------------------------------------------------------- 44

7.0.2 SEDIMENTATION CENTRIFUGES ------------------------------------------------------------------------------ 44

7.0.3 CENTRIFUGE DESIGN THEORY -------------------------------------------------------------------------------- 47

7.0.4 CHEMICAL DESIGN ----------------------------------------------------------------------------------------------- 50

7.0.4.1 Bowl diameter ---------------------------------------------------------------------------------------------- 50

7.0.4.2 Disk diameter ----------------------------------------------------------------------------------------------- 50

7.0.4.3 Terminal velocity ------------------------------------------------------------------------------------------- 50

7.0.4.5 Sigma value -------------------------------------------------------------------------------------------------- 51

7.0.4.6 Number of discs -------------------------------------------------------------------------------------------- 51

7.0.4.7 Inner radius of the discs ---------------------------------------------------------------------------------- 51

7.0.4.8 Radius of the interphase --------------------------------------------------------------------------------- 51

7.4.0.9 Disc length --------------------------------------------------------------------------------------------------- 52

7.4.0.9 Bowl axial height ------------------------------------------------------------------------------------------- 52

7.4.0.10 Disc spacing ------------------------------------------------------------------------------------------------ 52

7.4.0.11Disc perforations ------------------------------------------------------------------------------------------ 53

7.4.0.12 Centrifugal force ------------------------------------------------------------------------------------------ 53

7.4.0.13 Centrifugal settling velocity ---------------------------------------------------------------------------- 53

7.4.0.14 Retention time -------------------------------------------------------------------------------------------- 53

7.4.0.15 The centrifugal pressure -------------------------------------------------------------------------------- 53

7.4.0.16 Power consumption ------------------------------------------------------------------------------------- 54

7.0.5 MECHANICAL DESIGN ------------------------------------------------------------------------------------------- 56

7.0.5.1 Stresses involved ------------------------------------------------------------------------------------------- 56

7.0.5.2 Material of construction --------------------------------------------------------------------------------- 57

7.0.5.3 Vibration problem ----------------------------------------------------------------------------------------- 57

7.0.5.4 Thickness of the centrifuge shell ----------------------------------------------------------------------- 58

7.0.6 SUMMARY OF CENTRIFUGAL --------------------------------------------------------------------------------- 58

7.1 Design of a wipe film evaporator by JOAKIM KISUA PIUS CPE/09/08 -------------- 60

7.1.1 Functions of an evaporator------------------------------------------------------------------------------------ 60

7.1.2 DESIGN METHODOLOGY OF WIPED FILM EVAPORATOR ---------------------------------------------- 61

7.1.3 Wiped Film Evaporator Principle ----------------------------------------------------------------------------- 62

7.1.4 Thermal Design Calculations ---------------------------------------------------------------------------------- 64

7.1.5 Calculations ------------------------------------------------------------------------------------------------------- 66

7.1.5.1 Log mean temperature difference (LMTD) method ----------------------------------------------- 67

7.1.6 MECHANICAL DESIGN ------------------------------------------------------------------------------------------- 69

vi

7.1.7 AGITATOR DESIGN ----------------------------------------------------------------------------------------------- 69

7.1.7.1 Number of blade calculations --------------------------------------------------------------------------- 69

7.1.7.2 ----------------------------------------------------------------- 70

7.1.7.3 ---------------------------------------------------------------------------------------- 70

7.1.7.4 ------------------------------------------------------------------------------------------ 70

7.1.7.5 Jacket thickness -------------------------------------------------------------------------------------------- 71

7.1.7.6 Feed nozzle -------------------------------------------------------------------------------------------------- 71

7.1.7.7 Design temperature --------------------------------------------------------------------------------------- 71

7.1.7.8 Design pressure -------------------------------------------------------------------------------------------- 72

7.1.8 Design summary ------------------------------------------------------------------------------------------------- 73

CHAPTER 8 ---------------------------------------------------------------------------------------------- 74

8.0 PROCESS CONTROL AND INSTRUMENTATION -------------------------------------------- 74

8.1 Introduction --------------------------------------------------------------------------------------------------------- 74

8.2 Objectives of process control and instrumentation ------------------------------------------------------- 75

8.3 Classification of process variables ------------------------------------------------------------------------------ 75

8.4 Control principles -------------------------------------------------------------------------------------------------- 75

CHAPTER NINE ----------------------------------------------------------------------------------------- 79

9.0 ECONOMIC AND PROFITABILITY ANALYSIS ------------------------------------------------ 79

9.1 INTRODUCTION ----------------------------------------------------------------------------------------------------- 79

9.2 Economic Evaluations --------------------------------------------------------------------------------------------- 79

9.2.1 Estimation of fixed capital investment ------------------------------------------------------------------ 83

9.2.2 Total capital investment estimates ---------------------------------------------------------------------- 84

9.2.3 Total product cost -------------------------------------------------------------------------------------------- 84

9.2.4 Raw materials cost estimates ----------------------------------------------------------------------------- 85

9.2.5 Annual utilities cost estimates ---------------------------------------------------------------------------- 85

9.2.6 Depreciation --------------------------------------------------------------------------------------------------- 85

9.2.7 Operating labor cost estimates --------------------------------------------------------------------------- 87

9.2.8 Annual Cash Flow Analysis --------------------------------------------------------------------------------- 89

9.2.9 Cumulative cash flow analysis ----------------------------------------------------------------------------- 91

9.2.10 Profitability Analysis---------------------------------------------------------------------------------------- 92

9.2.11 Break-Even Point (BEP) Analysis ------------------------------------------------------------------------ 95

CHAPTER 10 --------------------------------------------------------------------------------------------- 97

10.0 SAFETY AND ENVIRONMENT IMPACT ASSESSMENT ----------------------------------- 97

10.1 INTRODUCTION --------------------------------------------------------------------------------------------------- 97

vii

10.2 SAFETY --------------------------------------------------------------------------------------------------------------- 98

10.3 ADMINISTRATIVE CONTROLS ------------------------------------------------------------------------------- 99

10.4 ENGINEERING SAFETY CONTROL --------------------------------------------------------------------------- 100

10.5 DEVELOPMENT OF A SAFETY AND HEALTH PROGRAM ----------------------------------------------- 101

10.6 HAZARD COMMUNICATION --------------------------------------------------------------------------------- 101

10.7 ENVIRONMENTAL IMPACT ASSESSMENT (EIA) ---------------------------------------------------------- 102

10.8 ENVIRONMENTAL IMPACT AND MITIGATION MEASURES ------------------------------------------- 103

10.9 LEGISLATION ----------------------------------------------------------------------------------------------------- 105

10.10 HAZARD AND OPERABILITY ANALYSIS (HAZOP) ------------------------------------------------------- 107

CHAPTER 11 --------------------------------------------------------------------------------------------114

11.0 PLANT LOCATION AND LAYOUT ------------------------------------------------------------114

11.1 INTRODUCTION ------------------------------------------------------------------------------------------------- 114

11.2 SITE LAYOUT ----------------------------------------------------------------------------------------------------- 115

11.3 PLANT LAYOU ---------------------------------------------------------------------------------------------------- 117

CHAPTER 12 --------------------------------------------------------------------------------------------118

12.0 CONCLUSION AND RECOMMENDATIONS -------------------------------------------------118

APPENDICES --------------------------------------------------------------------------------------------120

Appendix A: Data --------------------------------------------------------------------------------------120

Table A-1: specific heat capacities of key components ------------------------------------------------------ 120

Appendix B: Detailed Sample Mass Balances --------------------------------------------------120

Table B-2: Summary of mass balance around peeler machine -------------------------------------------- 121

Appendix C: Sample energy balance calculation ---------------------------------------------121

Appendix D: Equipment Sizing Calculations ---------------------------------------------------123

viii

LIST OF TABLES

Table 1: Varieties of avocado --------------------------------------------------------------------------------------------4

Table 2: Typical analysis results of Avocado oil Composition -------------------------------------------------9

Table 3: Vitamin content of avocado oil (seasonal range) per 100g -------------------------------------- 10

Table 4: A Typical analysis of the Fatty Acid composition of Avocado Oil ------------------------------- 11

Table 6: Laboratory analysis equipment used for avocado oil compositional analysis ------------- 18

Table 7: mass balance around the stone remover -------------------------------------------------------------- 32

: mass balance around the stone remover -------------------------------------------------------------- 32

Table 11: mass balance around the tricanter --------------------------------------------------------------------- 34

Table 14: mass balance around the wiped film molecular evaporator ----------------------------------- 36

Table 15: energy balance around the wiped film evaporator ----------------------------------------------- 39

LIST OF FIGURES

Figure 1: Tocopherols structure -------------------------------------------------------------------------------------- 14

Figure 2: Key elements of a wiped film evaporator ------------------------------------------------------------ 23

Figure 3: L-type and P-type rotors ----------------------------------------------------------------------------------- 24

Figure 4: R-type rotor and the inside of a glass lined evaporator ------------------------------------------ 24

Figure 5: wiped film evaporator rotor blade operation ------------------------------------------------------- 25

Figure 6: Wiped film evaporator rotor onsite installation --------------------------------------------------- 26

Figure 7: Virgin avocado oil processing line ---------------------------------------------------------------------- 26

Figure 8: Simplified diagram showing installation of a wiped film evaporator ------------------------ 27

Figure 9: Disk bowl centrifuge ---------------------------------------------------------------------------------------- 46

1

CHAPTER ONE

1.0 Introduction

The avocado is a tropical tree which grows well and abundantly in Kenya. It is one of the

many agricultural produce which is highly utilized in the country only on the nutritious

purposes. Various industries for example Olivado limited company, are utilizing this

market niche to produce avocado oil. Besides being nutritious, avocado fruit is also rich

in vitamins e.g. A, B, C and antioxidants lutein and at the same time components which

lower cholesterol (all this vital components are present in unsaponifiable fraction of

avocado oil). Despite avocado being rich in pytochemicals, cosmetic and pharmaceutical

industries in the country have not been keen enough to venture in richness of this fruit

to produce their respective product leaving the monopoly to the nutritious ventures.

This has resulted in viewing avocado as being a nutritious plant only and the farmers

are therefore not motivated to plant avocado plants in large quantity since the market is

not wide enough to give them a reason of widening their produce.

It has been noted the richness of avocado in nutrients, high in proteins, antioxidants and

dietary fiber. He observed that this high content of avocado in high fat and calorie

content has led nutritionists and dieticians either to advise against it or to use it . Many

studies and research however have proven avocado to be highly advantageous for

human health due to its healthy fat composition. All this goodness of avocado is well

preserved in avocado oil and thus presents an excellent alternative for utilization of the

fruit.

However, avocado oil has been produced and used by South Americans for centuries but

only as a skin ointment. On the other hand these alternative cosmetic and

pharmaceutical aspects of avocado oil are being utilized in American and French

industries among others to produce pharmaceutical and cosmetic products.

2

1.1Objectives of the Design project

The objectives of the design project are listed below:

i. To provide an alternative method of producing pharmaceutical jelly from

avocado oil

ii. To design the selected process for the pharmaceutical avocado oil production

iii. To locate the best site for the plant

iv. To carry out an economic cost analysis of the design plant

v. To assess the impacts of the processes wastes to the environment

3

CHAPTER TWO

2.1: Literature review

2.2: Historical Origin of the Plant

The avocado (alligator pear or aguacate as commonly known) is scientifically known as

Persea americana of the family Lauraceae and is a native plant of Southern Mexico and

Central America . Historical records of the usage of the plant exist from 7000 B.C. of its

cultivation from 6000 B.C. and continuous use in all the well known archeological sites

of Mexico.

In Kenya, avocado (Persea americana) also called Mwembe mafuta in Kiswahili was

introduced by the Portuguese in the 16th and 18th centuries. By 1939, improved

cultivars such as Puebla, Nabal, Lyon, Lula, Linda and at least 2 strains of Fuerte - one

from California and one from South Africa - had been introduced .These varieties

especially Fuerte and Puebla were adapted to the highlands of Kenya. Statistics show

that during 1970 only 23 t of avocado were exported. In 1984, 1400 tonnes of avocado

were exported from Kenya. The cultivars introduction programme commenced in 1965

with a focus to evaluate cultivars suitable for highlands and also lower altitudes and/or

agro-ecological zones.

2.3: Agronomy

2.3.1: Growth Requirements

The avocado plant grows well in warm areas with tropical to subtropical climates. The

plant at various stages does not tolerate climate that is too cold, too wet, too hot or too

dry. Its flowers are very sensitive to very low temperatures and freezing temperatures

tend to kill the plants. Frost and very hot weather results in a substantial loss of fruits

and too much wind is also highly unfavorable. The plant is tolerant to a wide range of

soil types (acidic and alkaline) with the exception of saline conditions. It does require

well aerated soils and will not survive in areas with poor drainage due to excess water.

It tends to grow well on hillsides but should never be grown near stream beds. The use

of phosphorous (P) fertilizers after one year of growth for young plants and nitrogen

(N) and potassium (K) for the older trees is very favorable for growth and fruit yields.

The plant can be grown in the shade but is productive only in full sun. It has been

reported that fruits continuously exposed to the sun were more hardy and tolerant to

conditions like high and low temperatures, had a slower rate of ripening, and more

resistant to pathogen invasion than those growing in the shade. The sun exposed fruits

were also higher in oil, dry matter and minerals. This supports the importance of

sunlight and temperature on avocado fruit development and qualities.

4

2.3.2: Fertilization

The pollination of avocado with its flowers is a classic example of protogyny. This

means the females mature before the males, so the flower cannot self pollinate but

requires pollen from another flower or another plant and this type of pollination is

called cross pollination. Growing plants bearing the two different types of flowers

together will allow cross pollination to occur and increase the chances of production. A

typical tree produces around a million flowers a year but only produces a dozen to a few

hundreds of fruits

Varieties & Cultivars

There are three known varieties or horticultural races of avocado and these are the

Mexican, Guatemalan and the West Indian Types. The Mexican types thrive in

Mediterranean climate and are native to dry subtropical plateaus. The Guatemalan

types are native to cool, high altitude tropics while the West Indian variety thrive in

humid, tropical climates. There are now many hybrids resulting from cross-breeding of

these three varieties and also from the selection of certain favorable attributes. The

three varieties can be differentiated from each other using various attributes as

provided in Table 1.

Table 1: Varieties of avocado

PROPERTIES

Main Attribute Specific

Attribute

Mexican Guatemala Indian

Oil Scent Nice None None

Leaf Size Small Various Various

Size Thin Warty Leathery

Seed Skin Big Small Big

Cavity Loose Tight Loose

Tolerance Cold Yes No No

Salt No No No

Fruits Oil content High Medium Low

Maturity

(month)

6 9 6

5

Growers however tend to identify the fruits by cultivars rather than varieties. A list of

various existing cultivars is provided on and only a few of the most popular cultivars are

listed and noted below.

Haas Guatemalan race and regarded as the industry standard fruit. Tree and fruit are

medium sized, thick skin, roundish and purple at full maturity. Has a good shelf life,

wide consumer acceptance and oil content is around 19 30%. It produces from April

to

September and is the most popular cultivar used around the world. It bears well only in

alternate years and is an A cultivar.

Fuerte This tall tree is a hybrid and produces a shiny green, round pear shaped, large

to very large fruits. Oil content around 18-26%, good flesh but also tends to bear fruits

in alternate years. Season is December and is a B cultivar.

Gwen The most popular and productive dwarf tree. Fruits are small, elongated and

remain green when ripe. Season is February to October and is an A cultivar.

Pinkerton A dense productive tree and is an A cultivar. Fruits look like long pears

with pebbly green skin. The fruits darken when ripe, have small seeds and are in season

in November.

Reed Known as the summertime variety avocado. Is an A cultivar and produces a

large fruit with thick green skin which stays green when ripe. Its season is August and

its flesh becomes buttery yellow when ripe.

Zutano A hybrid and is a columnar tree bearing medium to large fruits. Fruit has a

shiny yellow skin and is pear shaped. It is similar to a Fuerte but is inferior and has

fibres. Is a B cultivar and its colour remains the same when ripe.

Propagation

Growing avocado directly from the seeds is not favorable because it bears fruits only

after 4-6 years of growth and it rarely resembles the parent cultivar. The avocado has

Hypo-geal germination meaning the shoot grows directly from the epicotyl in the soil.

Commercial orchards are thus usually propagated by either grafted trees or rootstocks.

Rootstocks are propagated by seeds (seedling rootstocks) and layering (clonal

rootstocks). One common method is the etiolation technique used for propagating the

desired clonal rootstocks specific for disease and soil conditions. Lateral and terminal

grafting is normally used and carried out for young plants after one year of growth in

greenhouses.

Pests & Diseases

6

A soil borne fungus known as Phytophthora cinnamomi is a very severe disease which

causes root rot of the trees. The disease is easily transported by equipment, tools and

shoes from infected soil and farmers are highly encouraged to use disease free and

certified plants or rootstocks. Once a tree is infected it is difficult to treat except to cut

back on water supply. Dothiorella (Botryosphaeria ribis) canker is another fungus which

infects the trunk and results in dead patches which spread to maturing fruits causing

rancid smelling, darkened spots on the flesh. This disease which starts upon harvest

cannot be detected on the outside and has no means of control. A viral disease known as

sun blotch causes crinkling of new leaves, yellowed streaking of young stems, cracking

of the trunk and occasional fruit deformation. It is spread by the use of contaminated

tools and scions and so using virus-free propagating wood is a must. Pests include rats,

leaf caterpillars, avocado brown mite, six spotted mite and also snails

Harvest and postharvest

Avocado fruits are strange in that they only start to ripen and turn soft when they are

picked. They remain hard and continue to grow when mature on the tree until they fall

off. The fruits can be left on the tree (4-6 months) after being fully developed and will

ripen very quickly once picked. The taste of the fruits at the time of harvest depends on

their oil content which in turn is dependant on their stage of maturity. Avocados can

ripen quickly when stored together with other fruits like bananas and apples due to the

production of ethylene gas. The fruits must be handled with care when harvested to

minimize physical damage and bruising which results in undesirable discoloration and

softening of the pulp. The fruit ripening process like many is slowed considerably by

low temperatures. Report show that it is high activities of wall hydrolytic enzymes

during ripening that result in ultrastructural changes in the cell walls of ripened

avocado fruits. Extended cold storage results in chilling injury, which is marked by

improper softening, off flavour development and discoloration of the mesocarp. The

major storage component of the avocado fruit is the oil contained in its mesocarp. It is

the breakdown of the structure of these specialized oil cells during prolonged cold

storage that results in chilling injury.

A study conducted and reported noted that differences in postharvest quality were

attributed to differences in cultivars, growing conditions, location and fruit maturity.

2.3.3: Avocado Fruit & Human Health

Avocado Benefits

Bergh described the avocado fruit to be nutrition-rich while others in the industry call it

a functional food due to its additional health benefits from certain phytochemicals. It

contains high amounts of vitamins A ,B, C, E, and other nutrients like folacin, niacin, iron

(Fe), magnesium (Mg),

7

folate, pantothenic acid and contains 60% more potassium than bananas.

Most of these nutrients are deficient in most typical diets and are all abundantly present

in avocado. In its unmodified natural state the avocado represents a more balanced and

wholesome diet than most food or even concentrated supplement pills. Vitamins E, C

and beta carotene (vitamin A precursor) are natural antioxidants which protect against

dangerous free radicals which are by-products of life processes due to oxygen . These

free radicals result in cataracts from eye tenses, cancer due to cell mutation, arthritis,

advanced aging process, and heart disease due to cholesterol buildup. These

antioxidants are specifically effective in reducing the oxidation of the low density

lipoprotein (LDL) which leads to plaque deposits in arteries. The role of Vitamin Es role

in slowing down the aging process makes avocado very important in the cosmetic

industry. Avocado protein has also been proven to contain all the essential amino acids

for human nutrition attributes not provided by any other plant source. Its fiber content

was also noted to be high in both the soluble and insoluble forms and this is considered

very advantageous due to fibers lowering effects on cardiovascular disease,

hypertension, diabetes, and obesity. Pectin in particular a water-soluble fiber is known

to be most effective in maintaining heart health.

The avocado fruit contains more calories per gram than most other foods and thus

people tend to avoid it because of the well known adverse effects of cholesterol on

humans. The fat content of avocado which is the cause for many misconceptions

however is another valuable aspect of the fruit. More than 70% of its fat is

monounsaturated fat with low levels of polyunsaturated and saturated fat with slight

variations according to cultivars and fruit maturity stage. Monounsaturated fat in

particular has been noted to be highly beneficial in that it not only lowers the level of

the harmful cholesterol (LDL) but also maintains the level of the beneficial high-density

lipoprotein (HDL) or good cholesterol which protects the heart. The desirable HDL is

lowered with diets low in fat, or high in complex carbohydrates which is usually used by

many people wanting to lose weight. A diet high in polyunsaturated fat on the other

hand not only reduces HDL but is highly prone to oxidation at the site of unsaturation in

its structure.

The use of avocado in human nutrition controlled experiments have either proven or

claimed the following findings:

Subjects on avocado enriched diets had a decrease in total cholesterol level

A reduction in body weights and;

A reduction in stroke incidences due to high potassium content.

Avocados are also highly recommended food for infants. The smooth, delicate flavor,

creamy consistency makes it an excellent food choice. More importantly it provides

them with essential nutrients and monounsaturated fat which is beneficial for babys

development. The more traditional uses of the fruit in particular for the South American

people is its use as a sexual stimulant.

Avocado Disadvantage

8

There is documented evidence that feeding any part of the avocado tree including its

fruit to any non-human animal is life threatening and lethal for some animals. Thus total

avoidance of any part of the tree is recommended by most animal organizations

Avocado Oil

Avocado oil is the major avocado product which utilizes this otherwise not very popular

fruit in Kenya. Only a few countries are actually involved in the production of oil namely

Mexico (34%), USA (8%), Israel (4%), South Africa (

9

Arpaia also noted differences in oil content for the same cultivar due to different

locations and growth conditions such as soil fertility. Sun exposed fruits were also found

to yield higher levels of oil than those fruits in the shade.

Biochemical Composition & Physiochemical Properties of Oil

Understanding the biochemical composition and physiochemical properties of the oil

help explain its functional properties and uses. Most of the beneficial attributes

associated with eating avocados are mostly preserved in the oil and for this reason is

very valuable.

The composition and in particular properties of the oil varies according to how it is

produced whether it be crude, virgin or refined according to the method and number of

successive operations involved in its production.

Various analyses have been done on the composition of avocado oil and Table 2 lists

typical results.

Table 2: Typical analysis results of Avocado oil Composition

Parameter Avocado Oil

Acidity Value (as oleic) (%) 2.0-0.8

Peroxide value (meq/kg fat) 3.3-0.1

Iodine value (from GLC) 87-75

Color (chlorophyll) (ppm) 40-70 virgin, 1-10 RBD

Specific Gravity (25o C) 0.912-0.916

Beta-sistosterol (%) 0.45-1.0

Total Vitamin E (mg/kg) 112-200

Alpha-tocopherol (mg/kg) 130

Beta/gamma-tocopherol

(mg/kg)

15

Delta-tocopherol (mg/kg) 5

Flash point 150-2550 C

Un-saponifiables 5.0-18%

Cholesterol 0

Sodium 0

Carbohydrate 0

10

The comparison of the compositional make up of avocado and olive oil shows very

similar results for most parameters. The Vitamin E, Beta-sistosterol and alpha

tocopherol levels however are much higher in avocado oil, the micronutrients with

significant proof of health benefits. The flash or smoke point of avocado oil is another

noticeable feature. This makes the oil highly applicable for high temperature cooking as

it will not burn until it reaches temperatures well above 1500C. The acidity value and

peroxide values indicate stability in terms of minimal hydrolysis and lipase activities.

The oil is also free of cholesterol and carbohydrate. Table 3 shows a Vitamin analysis of

avocado oil.

Table 3: Vitamin content of avocado oil (seasonal range) per 100g

Vitamins Result

Vitamin A (carotene) 370-870 IU

Vitamin B2 (Riboflavin) 0.08-0.16

Pyrodixine 0.19-0.26 mg

Pantothenic acid 0.78-1.2 mg

Folic acid 0.022-0.105 mg

Thiamine Hcl 0.08-0.125 mg

Ascorbic acid 4.0-13.0 mg

Niacin 1.05-2.42 mg

Choline 12.0-22.2 mg

Biotin 2.3-4.2 mg

Vitamin E 0.8-4.2 IU

As seen in the above table, the vitamin content of oil varies within a range for the

various parameters and the usual influential factors of cultivar, maturity and processing

method is likely to impact on these values. The list is extensive and most of the vitamins

is lacking in most diets. The presence of most of these vitamins in avocado oil gives it

the properties which makes the oil highly valuable in the cosmetic industry.

Fatty Acid Composition

As seen in Table 2 the iodine value is high indicating a high degree of unsaturation.

11

Typical avocado oil is comprised mostly of monounsaturated fatty acids (74%), 11%

polyunsaturated fatty acids and about 13% saturated. These percentages vary slightly

with cultivars and other influential factors but the oil is very similar to olive oil. It is this

high level of monounsaturated fat which gives the desirable effect of being

anticholesterol as it prevents the formation of clots the major cause of coronary heart

disease.

Table 4: A Typical analysis of the Fatty Acid composition of Avocado Oil

Fatty Acids Saturation Africa oil

analysis (%)

New Zealand oil Analysis

(%)

Palmetic Acid C16:1 11.85 12.5-14.0

Palmitoleic Acid C16:1 3.98 4.0-5.0

Stearic Acid C18:0 0.87 0.2-0.4

Oleic Acid C18:1 70.54 70-74

Linoleic Acid C18:2 9.45 9.0-10.0

Linolenic acid C18:3 0.87 0.3-0.6

Arachidic Acid C20:0 0.50 0.1

Gadoleic Acid C20:1 - 0.1

Eliosenoic Acid C20:1 0.39 -

Table 4 lists results from two different countries and their analysis of avocado oil

confirms the healthy composition of the oil in terms of fatty acid composition.

The analysis reported in Table 4 was done using the Fatty Acid Methyl Ester (FAME)

analysis on a Gas Chromatograph.

Phytochemicals

The naturally occurring phenolic compounds found in vegetables and fruits have been

proven to have equal or greater cholesterol lowering properties than unsaturated fatty

acids. Beta-sitosterol (a phytosterol) is one of the healthy plant compounds found to be

most abundant in avocado. It is widely proven to be responsible for the non-absorption

of the bad cholesterol (LDL) and maintaining the good HDL cholesterol in the intestine

which then lowers total plasma cholesterol. This compound was also reported by the

British Medical Journal the Lancet to be very effective in offering relief to men above 50

years who suffered from benign prostatic hyperplasia resulting in significant

improvements in urinary difficulties. The phytosterol content has the same skin

penetrating abilities of lanolin and for this reason avocado oil is highly valuable in the

cosmetic industry. Lutein or carotenoid is also highly abundant in avocado oil. This

12

phytochemical is effective in providing protection against prostate cancer, eye diseases

and mascular degeneration. Lozano noted that the unsaponifiable fraction from

immature fruits contained a much higher level for both total sterol (1.1 6.2%) and

tocopherol compared to matured fruits (sterol 0.8-2.0% & tocopherols 5.7-10.3 mg/100

g oil). This is very significant for the extraction of enriched amounts of these

Compounds as they are of high health significance.

Antioxidants

Phytochemicals in plants is reported to have greater antioxidant effects than minerals

and vitamins. Lutein for example is one very effective antioxidant. Vitamin E represents

a mixture of chemicals known as tocopherols and

tocotrienols and is another well known vitamin with antioxidant effects. tocopherol

is one powerful antioxidant which neutralizes the free radicals produced under the

normal metabolism of lipid compounds. As noted in table 2 this is also abundant in

avocado oil. All these antioxidants found in high levels in avocado oil neutralize the free

radicals which would otherwise result in the following:

eye deterioration;

inflammation of the joints;

damage to nerve cells in the brain;

accelerating the ageing process and;

Certain cancers.

Chlorophyll & Carotenoids

Crude and virgin oils have high chlorophyll and amounts of other soluble pigments

(carotenoids) which give it their distinctive brown green or emerald green colour. The

virgin oil with high chlorophyll content is highly desired by consumers due to the health

benefits associated with the presence of these micronutrients. The high chlorophyll

content makes the oil highly prone to oxidative effects upon exposure to light and for

this reason must be packed in dark bottles. Other carotenoids like lutein are also

present in high amounts while others like neoxanthin, violaxanthin, antheraxanthin are

present in very minute amounts. Further processing and refining removes the

chlorophyll and other pigments giving oil that is pale yellow in colour and also more

stable.

Unsaponifiable Fraction

The healthy plant micronutrients which have anti-oxidant, anti-inflammatory, and

cholesterol lowering properties are mostly contained in this portion of the oil. This part

of avocado oil is highly valued in the pharmaceutical and cosmetic industries for the

high skin penetration coefficient and the specific biological actions of its sterols.

13

Human journal also reported this fraction to contain an unknown factor known as the H

factor which has healing properties. Eyres reported that the healing properties may be

linked with lysyl oxidase which initiates cross linking in collagen and inhibits enzyme

activity. This would be very important for the treatment of wounds and burns.

The unsaponifiable fraction is also high in nutrients which are another reason why it is

highly sought after by the cosmetic industry. The French pharmaceutical industry filed

two separate patents No 17/245 and No 102888 for the extraction of this fraction

indicating its high value. Lozano reported that the unsaponifiable matter in oil from

immature fruits (15-40%) was always higher than the matured fruits (4-9%). This

fraction of the oil is where most of the healthy plant sterols are concentrated. This is

interesting as it presents another valuable option for farmers in using immature fruits

for extracting this highly valuable unsaponifiable matter from oil.

Oil Utilization

Cosmetic Industry

Avocado oil is well known for its anti-bacterial, anti-wrinkle and healing properties. The

multiple properties of avocado oil namely stability, emolliency, skin penetration,

softening and moisturizing results in its wide applicability for cosmetic products. The

high penetration ability of the oil in particular makes it very successful in its use as a

natural and effective beauty aid. It is used in a wide variety of creams and oils for skin

application as it acts as an effective carrier of other supplements incapable of

permeating the skin. The high content of lecithin and phytosterols facilitates its

spreadability. It is easy to emulsify as its low surface tension makes smoother creams

and soaps. Vitamin A helps prevent dry skin while Vitamins E and D are effective against

skin wrinkling and slow the process of ageing. A few New Zealand and US companies

now manufacture various skin care products using avocado oil, like body moisturizer,

replenishing facial crme, skin repair crme and natural oil for everyday use.

The oil is an ingredient for up-market skin care cosmetics, shampoos and baby

products.

The oil is highly priced to those with skin problems and is used as a base for ointments

used for treating dermatitis, acne, lacerations and other skin conditions. It is also used

as a post-operative dressing to prevent adhesions to wounds and skin burns while

accelerating the healing process. It also has strong UV absorption properties making it a

very good effective sunscreen.

Avocado oil for skin

As mentioned previously, avocado oil has been many a times as used on skin purposely

to provide protection of skin. The underlying reasons of its protective aspect are largely

due to the presence of antioxidant components (in Vitamin E) which are of course

tocopherols and tocotrienol. Tocopherols are best known and most widely used

antioxidants.

14

Figure 1: Tocopherols structure

Tocopherols function as antioxidants by donating the hydrogen of the hydroxyl group to

the lipids peroxyl radical. The hydrogen donating power of tocopherols is in fats and

oils is in the order >>. Tocopherol can also function as inhibitors of lipid

oxidation by scavenging singlet oxygen molecules and free radicals.

Food The oil is highly applicable for food preparation and because of its high quality

(Similar to olive oil) it provides another healthy alternative for consumers. It is

marketed as healthy oil due to its high content of monounsaturated fat, presence of

essential amino acids and high vitamin content. The high sterol content in particular

and its cholesterol lowering effect is what makes this oil a must for modern society. It

has a high smoke point making it suitable for high temperature cooking. It also has a

bland flavor which does not disguise the natural flavor of food. It is also used as a

dressing which does not disguise the natural flavour of food. It is also used as a dressing

for salads and vegetables and also as a dip for hot food like bread. There are naturally

infused oil available with different flavours like garlic, chilli, lemon and orange which

provide consumers more choices to choose from

Dietary supplement One of the most exciting products produced by New Zealand

based Olivado and Elysian Isle companies is the avocado oil capsule. It simply takes all

the beneficial attributes found in avocado oil and seal it in a health capsule which can be

taken daily. It contains all the healthy micronutrients and vitamins available in the oil

which can help fight bad cholesterol, inflammatory, osteoarthritis and prostate

problems.

Extraction of Avocado Oil

15

To produce a quality product requires high quality raw materials. For this reason it is

imperative that the fruits used are of high grade in particular must contain high

proportion of pulp, have high oil content, free of diseases and must not be physically

damaged as evident in pulp discoloration and/or off-flavors. The fruits have to be

carefully matured and ripened to allow for maximum oil development before they are

used. Various methods have been used in the extraction of oil from avocado fruits. The

methods vary in their degree of effectiveness for oil extraction and also subsequent

effect on the resultant oil quality. Heating and chemical extraction have been the

traditional methods used and now a new method has been developed in New Zealand

which allows oil to be expressed from the fruits with very minimal processing. Human

journal lists various methods used in the past for the extraction of avocado oil involving

steam pressure, hydraulic pressing, solvent extraction, centrifugation, freeze-drying,

rendering process and the use of a tube press plant. However the specific application of

the oil should determine the process and method chosen. Only the most practical and

suitable methods are discussed below.

Pre-Process Treatment

Avocado fruits destined for oil production must be firstly inspected for physical damage

and other abnormalities. They are then washed before being processed to remove the

skin and seed. The means used for washing, de-stoning and de-skinning of the fruits

vary but all processes involve this first critical step.

Rendering process

This method involves heating of the avocado pulp in avocado oil.

The moisture evaporates off leaving the oil and the dry matter behind. The oil can then

be decanted off while the remaining slurry is subjected to hydraulic pressure to press

out more or the remaining oil. It is reported that laboratory experiments resulted in

94% recovery of the oil using this method.

Tube Press Plant

This consists of either one or two tubes. The tubes are filled with avocado pulp and

then subjected to hydraulic pressure to press out the oil through perforations within the

inner tubes. This method was developed my Mess Alfa Laval and aims at extracting out

most of the oil with minimal damage to the oil quality.

Solvent Extraction

This is one of the traditional methods commonly used. Various solvents could be used

and organic solvents have mostly been utilized. Botha reported experimental solvent

extractions using hexane and a Soxhlet extractor on a 10g dried sample for 8 hours.

Subsequent removal of the solvent is followed by vacuum evaporation and drying until

constant mass. The resultant oil has a high chlorophyll content meaning the chlorophyll

is co-extracted along with the oil. Chlorophyll levels as high as 192.9 ppm was reported

by Werman & Neeman to have been extracted in the laboratory by ethanolic extraction.

16

Human journal reported this method to have the highest yield but industrial equipment

is very expensive to install plus the highly flammable solvents used are very dangerous.

The recovery and total removal of the solvent is also an issue which requires a highly

sophisticated plant. Thus because the raw material is an expensive fruit and the oil yield

is at maximum around 22% of the whole fruit it is not economical to extract avocado oil

in this way. Xiao reported the method does have other disadvantages like loss of volatile

compounds, long extraction times, toxic solvent residues and degradation of valuable oil

compounds.

Centrifugation

After the pre-processing treatment, the fruits are fed into a mill where it takes the form

of a guacamole. The malaxing (mixing) takes up to several hours until the release of the

fine emulsion of oil. The paste is then fed to a centrifugal decanter where the oil is

separated from the guacamole. Reported that extraction of oil was most efficient using

centrifugal force 12,300 kg, a 5:1 water to avocado ratio, temperature 75 OC, with a pH

5.5 and a 5% concentration of either NaCl, CaCO3 or CaSO4.

Cold Press

This relatively new method of extracting oil makes use of the modern Alfa

Laval centrifugal extraction method so is a variation of the above method. The fruit flesh

is firstly macerated by high speed grinders before the mixture is mixed in malaxers.

When this process is complete, a three phase decanter then separates the mixture into

oil, water and solids before polishing takes place with a multi-cone centrifuge. Extra

virgin oil is produced after the first press. The extraction efficiency is dependent on such

things like pH, centrifugation rate, salt, mixing temperature (

17

for baked goods. It can also be used as a simple drizzle on vegetables and

potatoes and also for shallow pan-frying of poultry and fish

The production of cold pressed oil requires little investment and the process

itself is simple. However the process has inefficiencies in that around 6-15% of

the oil remains in the pressed residue

Supercritical CO2

Botha reported extraction results for avocado oil extracted using supercritical carbon di

oxide under four different extraction conditions.

Spectroscopic quantification of the color of avocado oil extracted with

supercritical carbon dioxide at four different conditions:

Extraction Condition Absorption Value Visual Quantification

370C/350 atm 0.325 Straw-yellow

370C/532 atm 0.410 Straw-yellow greenish tint

810C/350 atm 0.526 Straw-yellow with strong

greenish tint

810C/532 atm 0.765 Green with yellow tint

The above Table 5 indicates that at higher temperatures and pressures, chlorophyll can

be co-extracted along with the oil. Xiao reported that the power of solubilization for

supercritical CO2 can be achieved with higher densities which are achieved at higher

pressures. This allows large amounts of organic compounds to be dissolved which can

later be separated from the fluid by means of reducing the temperatures or pressures.

Thus the extraction of the phytochemicals was only possible at higher pressures and

temperatures only due to the solubilisation of the organic compounds. Lower

temperatures and pressures will extract only the oil without chlorophyll. This method is

very important as it basically proves that more stable oil without chlorophyll can be

extracted this way which eliminates the need to refine the oil of its color pigments. The

oil however does not contain the healthy plant compounds which are highly attributed

for its health benefits.

Before analyzing the free fatty acid of the oil the CO2 must be totally removed as it

increases the acidity level. This can be done by subjecting the oil to vacuum evaporation.

The degree of oxidation of the oil in the dried material used for extraction is also

important as volatile acids are also co-extracted by this method. The free fatty acid

content however of the oil extracted by this method was not different to the FFA of the

oil extracted by hexane indicating no effect on pressure, temperature or supercritical

CO2 on the hydrolysis of the parent glycerides.

18

An important outcome of extracting with supercritical fluid as reported by Botha was

that the unsaponifiable fraction of the oil was found to be higher for the first fractional

extraction (20 minute intervals) and tend to decrease with subsequent extractions.

Thus the unsaponifiable fraction of the oil can be enriched by extracting at time

intervals.

The use of supercritical fluid is proven to be a cost-effective technique for laboratory

scale while large scale units still require experimentation for accurate economic

valuations. This method has advantages such as low operating temperatures, shorter

extraction periods, high selectivity in the extraction of compounds and no undesirable

solvent residue. It also uses a safe, readily available gas.

Effect of processing on the quality of the oil

The phenolic compounds which are well publicized for their health benefits are lost or

destroyed by most processing methods. Extra virgin oil loses its highly beneficial

micronutrients during the refining process and the cholesterol lowering and anti-

oxidant properties are significantly reduced as a result. The color or chlorophyll content

of the oil is noticeably lower than that of virgin oil due to the removal of these plant

compounds.

Xiao noted that the usual methods of hydrodistillation and organic solvent extractions

present problems like toxic solvent residues, degradation of the unsaturated

compounds and vitamins, and giving objectionable off-flavours due to heat. The change

from NaOH to Na2CO3 or NaHCO3 when refining is reported to achieve the same results

when refining with the extra benefit of retaining the phenolic compounds. Thus a more

stable and healthy oil can still be achieved after refining if Na2CO3 or NaHCO3 is used.

The cold pressing and supercritical fluid methods appear to be the most suitable and

beneficial methods to extract the avocado oil. Both utilise low temperatures which help

retain the healthful composition of the oil, involves minimal processing and requires

less capital investment.

Analysis Methods for Oil Components

The analysis of the various biochemical and physiochemical composition of the oil can

be analyzed using the following equipment given in Table 6.

Table 5: Laboratory analysis equipment used for avocado oil compositional

analysis

Equipment Components Extraction

Method

19

Gas Chromatography

FAME analysis

For fatty acid

composition

Cold press

centrifuge

Gas Chromatography

Mass Spectrometric

Major compounds Supercritical CO2

High Performance

Liquid

Chromatography

Triacylglycerols,

sitosterol &

tocopherol, lutein and

total chlorophyll

Other detailed analysis as given in tables 2 & 3 do not specify the methods of analysis

used. However the analysis equipment used for analysing other vegetable oils will

undoubtedly be suitable for the analysis of avocado oil.

20

CHAPTER THREE

3.0: JUSTICATION

The high content of pharmaceutical components like the unsaponifiables( which is rich

in tocopherols and lutein-are very effective in healing skin ailments and preventing skin

aging ) in avocado fruit and the abundance of the raw materials and specifically the

furte avocado variety in central and eastern provinces of Kenya presents a perfect

viability of the project since there will be continuous supply of the raw material.

Secondly, the extraction processes for both the virgin oil and the unsaponifiable fraction

of the avocado oil are comparatively cheap. Cold Press method of extraction of avocado

oil involves low temperature and minimal processing and as a result the oil retains all

its natural flavor, nutrients and healthy properties.

On the other hand, unsaponfiable fraction of avocado oil is extracted in a substantial

quantity without affecting the chemical properties of the fraction.

The oil which becomes the co-product is can be availed for further refining.

21

CHAPTER FOUR

4.0: PROCESS DESCRIPTION

4.1 Pre-process treatment

Do fruits destined for oil production must be firstly inspected for physical damage and

other abnormalities. They are then washed before being processed to remove the skin

and seed. The seed removal and skin removal are done by the de-stoning machine and

de-skinning machine respectively.

4.2 Extraction process

The fruit flesh is firstly macerated by high speed disintegrator before it is then is mixed

in mixer (malaxor). When this process is complete, the three phase decanter then

separates the mixture into oil, water and cake. Extract virgin oil is produced after the

first press. The process is carried out at normal temperature. At no time along the whole

process is the oil subjected to light or oxygen as this has a deteriorating effect on the

quality of the oil. The resultant oil is of high quality and is considered virgin oil because

of the minimal processes involved. The virgin oil is then pumped to a centrifuge for

polishing. Here the suspended solids and water traces are removed.

4.3 Preheating

The degassed oil is passed through heat exchangers for the purpose of temperature

elevation before the oil finally enters the wipe film molecular distiller where it

undergoes fractionation into a light phase that is rich in unsaponifiable fraction i.e.

sterol esters and a heavy phase that is rich in triglycerides and a small fraction of

esterified sterols that do not vaporize under the temperature conditions in the

evaporator.

Molecular evaporation

The wipe film molecular mollecular evaporator is widely applied in industry,in

which,the wiper renews the evaporating liquid film continously,and so the local

overheating of the materials is avoided and the internal mass and heat transfer

processes are enforced.this evaporater has the following advantages that make it

suitable for our process;

Low residence time

No liquid hold up

Very low pressure drop

Suitable for extremely heat sensitive products because of the short path

involved.

The traditional theory of molecular evaporation is based on mean free path theory of

gas molecule, and an equation given by Langmuir is as follows;

m=(k/2)(T/d2P)

this equation shows that mean free path m is related to temperature T(K),pressure

P(Pa) and size of the molecule d(m).k is the Boltzman constant 1.38010-23 J.K-1

22

How a molecular evaporator works

The process fluid enters the unit tangentially above the heated zone, and is distributed

evenly over the inner surface of the body wall by a distribution ring mounted on the

rotor. The rotor blades spread over the entire heated wall, and generate highly

turbulent flow conditions in the thin layer of liquid.

The product spirals down the wall, while the turbulent conditions developed by the

rotor blades generate optimal heat flux, rapidly evaporating volatile components. The

resulting vapors flow upwards through the unit into a centrifugal separator, which

returns entrained droplets or froth directly back to the heating zone. Clean vapors pass

through the vapor outlet ready for condensing or further processing. Meanwhile, the

concentrated liquid stream leaves the evaporator through its bottom conical outlet.

Continuous washing by the bow waves generated by the rotor minimizes surface fouling

of the thermal wall, where the concentrated liquid or residue is most prevalent.

23

Figure 2: Key elements of a wiped film evaporator

The wipe film evaporator is merely a single evaporation tube fitted with a mechanical

rotating device called a rotor. The distributer is welded to the rotor according to the

propriety design. This ensures that the liquid feed is evenly distributed on to the heated

surface of the evaporater.it then flows downwards in a spiral motion which is created

by the blades of the rotor. Turbulent eddies are formed at the rotor tips, which

continuously agitate and remix the liquid film. The resulting vapor normally rises

upwards, counter-currently to the liquid flow.it passes through a gas-liquid separator

mounted at the top of the evaporator and is then normally directed to the downstream

condenser the concentrate leaves the unit via the bottom of the evaporator.

The upper part of the rotor incorporates a liquid distributor and a centrifugal separator

to effectively dis-entrain liquid droplets from the vapor flows, rotating baffles mounted

24

on the rotor are complemented by static ones. The figures below show the different

rotor types used in this evaporator.

Figure 3: L-type and P-type rotors

Figure 4: R-type rotor and the inside of a glass lined evaporator

25

The figure below shows a cross-section of a wipe film evaporator showing the blade and

bow wave formed in front of it.

Figure 5: wiped film evaporator rotor blade operation

26

Figure 6: Wiped film evaporator rotor onsite installation

Figure 7: Virgin avocado oil processing line

27

Fig: Virgin avocado oil processing line.

Figure 8: Simplified diagram showing installation of a wiped film evaporator

Evaporation of virgin avocado oil is a fractionation step which at the end gives:

The distilled fraction that is rich in unsaponifiables generally representing 5% to

15% by weight of the starting virgin oil. This fraction is composed mainly of non-

esterified sterols.

The fraction that is rich in triglycerides representing 80% to 85% by weight of

the starting virgin oil. In this fraction there is a 0.5% to 1.5% unsaponifiables

(esterified sterols) in the form of fatty acid esters.

The high triglyceride content of virgin avocado oil and its low partial (mono and

di) glycerides content demonstrates that the oil is very pure and guarantees a

low degree of hydrolysis and good stability. This gives an assurance of no

chances of hydrolysis.

28

BLOCK DIAGRAMS

S5

MIXER (Malaxor)

Water (S4)

C3

(S3)

Skins

(S2)

DISINTEGRATOR

Pulp C2

(C2)

Seeds (S1)

Avocado fruits (C1)

SKIN REMOVER

STONE REMOVER

29

Oil (S11)

Cake S7

S5

STORAGE TANK 1

THREE PHASE

DECANTER

CENTRIFUGAL

SEDIMENTATION TANK

STORAGE TANK 2

S6

Virgin oil (S9)

Water (S8)

Water (S10)

Solids

(S12

)

30

S14

HEAT EXCHANGER

S12

S17

S15

WIPED FILM MOLECULAR

EVAPORATOR

S13

CONDENSER

STORAGE TANK 5

STORAGE TANK 4

S16

31

CHAPTER FIVE

5.0: MASS AND ENERGY BALANCES

5.1.1: Mass balance

Introduction

Material balances are the basis of process design. A material balance taken over the

complete process will determine the quantities of raw materials required and products

produced. Balances over individual process units set the process stream flows and

compositions.

Material balances are also useful tools for the study of plant operation and trouble

shooting. They can be used to check performance against design; to extend the often

limited data available from the plant instrumentation; to check instrument calibrations;

and to locate sources of material loss.

All mass/material balances are based on the principle of conservation of mass that is

mass can neither be created nor destroyed with an exception of nuclear processes

according to Einsteins equation; E=mc2.

The general conservation equation for any process system can be written as:

For a steady state process the accumulation term is zero and thus for a continuous

steady state process, the general balance equation for any substance involved in the

process can be written as:

In a case of a physical process as most of our operations are the general balance

equation reduces to:

Material In = Material Out

If no chemical reaction takes place, material balance is computed on the basis of

chemical compounds mass basis that are used whereas if a chemical reaction occurs

molar units are used.

Also it is worthwhile to note that when a reaction occurs an overall balance is not

appropriate but a reactant balance (a compound balance) is.

Choosing the basis

The correct choice of the basis for a calculation will often determine whether the

calculation proves to be simple or complex.

32

A time basis was chosen in which results will be presented.

Our basis of calculation shall be one hour and hence results will be presented in kg/hrs.

Basis

One hour

Avocado feed = 4999kg

STONE REMOVER

Table 6: mass balance around the stone remover

SKIN REMOVER

: Mass balance around the stone remover

INLET STREAMS OUTLET STREAM

Streams components Mass

(kgs)

streams components Mass (kgs)

C1 Pulps 4999 C2 Pulps 4999

Seeds 1365 Skins 580

Skins 580 S1 Seeds 1365

TOTAL 6944 TOTAL 6944


Streams Components Mass

(kgs)

Streams Components Mass (kgs)

C2 Pulps 4999 C3 Pulps 4999

Skins 580 S2 Skins 580


SKIN REMOVER

C2

C3 S2

C1

C2

DE-STONING

MACHINE

S1

33

THE MIXER (Malaxor)



(Kgs)

Streams Components Mass (Kgs)

S3 Pulps 4999 S5 Slurry 7251

S4 Water 2252


MIXER

S3

a

S5

S4

34

THE THREE PHASE DECANTER

Table 8: mass balance around the tricanter



(kgs)


S6 Virgin oil 868 S7 Water 5031

Cake 1041 S8 Sludge 1437

Water 5342 S9 Virgin oil 783


S7

S9

S6

S8

THREE PHASE

DECANTER

35

CENTRIFUGE

N/B: mass of cake coming out from centrifuge (S 16) is assumed to be negligible.



(kgs)


S9 Virgin oil 781 S10 Water 2

Water 2 S11 Virgin oil 781

TOTAL 783 TOTAL 783

CENTRIFUGE

S10

S9

S11

36

WIPED FILM MOLECULAR EVAPORATOR



(kgs)

streams components Mass (kgs)

S13 Preheated

oil

781 S14 Light phase 117.15

Steam S15 Heavy phase 663.85

Condensate

TOTAL 781 TOTAL 781

Table 9: mass balance around the wiped film molecular evaporator

S14 S15

S13

WIPE FILM MOLECULAR

EVAPORATOR

37

5.1.2: ENERGY BALANCE

The law of conservation of Enthalpy states that Enthalpy can neither be created nor

destroyed, but can only be transformed from one form to another. The general equation

of Enthalpy balance is given by;

For these calculations, Kinetic Enthalpy and Potential Enthalpy are assumed negligible.

In any unit operation that does not involve a chemical reaction, the Enthalpy balance

equation will take the form;

For these calculations, Kinetic Enthalpy and Potential Enthalpy are assumed negligible.

In any unit operation that does not involve a chemical reaction, the Enthalpy balance

equation will take the form;

Q = cpdt ; dt = T (change in temperature)

Cp (light phase) = 2.33 kj/kg O C

Cp (heavy phase) = 3.20 kJ/kg O C

CP (virgin oil) = 3.01 kJ/kg O C

Datum temperature = 25 O C

Assumptions

There are negligible energy losses in all the unit operations

Energy in Energy out + Energy generated + energy consumed Work done = Accumulation

Energy In Energy Out = Accumulation

Q = QFeed- QProduct

38

HEAT EXCHANGER

WIPE FILM MOLE CULAR EVAPORATOR


streams Component Mass

(kgs)

Enthalpy

(kJ/hr)

streams components Mass

(kgs)

Enthalpy

(kJ/hr)

S17 Virgin Oil 781 0 S18 Virgin Oil 781 293851.25

S20 Heavy

phase oil

663.85 362411.26 S21 Heavy

phase oil

663.85 68564.29

TOTAL 1484 362411.26 TOTAL 1484 362411.26

HEAT EXCHANGER

S17 S21

S18 S20

S20

S18

S19

WIPE FILM MOLECULAR

EVAPORATOR

39


streams Component Mass

(kgs)

Enthalpy

(kJ/hr)

streams components Mass

(kgs)

Enthalpy

(kJ/hr)

S13 Degassed

Oil

781 293851.25 S13 Light phase 117.15 35439.99

QGEN 104,000 S15 Heavy phase 663.85 362411.2

6

TOTAL 781 397851.25 TOTAL 781 397851.

25

Table 10: energy balance around the wiped film evaporator

40

CHAPTER SIX

6.0 EQUIPMENT SELECTION, SIZING AND SPECIFICATION

INTRODUCTION

The basis of material selection and specification is largely derived or brought about by

the specific operation of equipment. During the operation, the equipment are dutied to

withstand high pressures, high temperature conditions, equipment capacity among

other operating conditions which are likely to impact wears to the equipment. It is in

this light that the equipments materials are chosen so that they are not frequently

replaced. However, the cost of purchasing the equipment with these specifications is

high and therefore the factor of functionality is paramount when choosing the

equipment for various operations.

The equipment for extracting pharmaceutical avocado jelly from avocado pear fruit are

chosen in consistence with the type of operations they are expected to carry out.

6.1 CHOICE OF MATERIALS FOR EQUIPMENT FABRICATIONS

The main factors governing the choice of materials of construction for a specific

equipment unit include:

the corrosiveness of the content that it handles

the cost of material fabrication

the temperature of operation

the pressure of operation

the end use of the material

the ease of fabricating the equipment

41

The following are the equipment with their specifications used during the project

Units Specifications

De-stoning machine Code: DM

Service: removes avocado pear seeds

Type:

Material: stainless steel

Peeling machine: Code: PM

Service: removes avocado pear peels

Type: counter rotary drum

Material: 15 gauge stainless steel

Diameter: 0.41m

width: 0.10m

perforated drum: round holes diameter 0.64cm

Disintegrator: Code: SR

Service: reduces avocado pear pulps sizes

Type: high speed grinder


Capacity: 5m3/hr

Mixer (malaxor): Code: MIX

Service: reduces avocado pear pulps into slurry

Type: flat topped


Capacity: 1.578m

Diameter: 1.262m

Height: 2.524m

Surge tank 1 Code: ST 1

42

Service: temporal storage of water/avocado pulp mixture

Type: flat topped


Capacity:1.6m3/hr

Three phase decanter: Code: DC 001

Service: separates oil, water and cake

Type: solid-liquid-liquid decanter


Bowl:

Inner diameter: 500mm

L/D: 4.0

Speed maximum: 3450rpm

G force: 3333g

Centrifuge: Code: CF

Service: Separates solid particles from oil

Type: disc bowl

Material: Stainless steel

Capacity: 3.44m

Length: 2.59m

Height: 0.65m

Surge tank 2: Code: FT 001

Service: for temporal storage of crude oil

Type: dome topped


Capacity: 3.44m

43

Length: 2.59m

Diameter: 0.65m

Heat exchanger Code: HE 001

Service: for preheating crude oil and cooling oil product

Type: shell and tube

Material: carbon steel

Length: 3m

Cross-sectional are: 0.2m2

Number of tube: 87

Length of tube: 2.8m

Area of a tube: 0.01m2

Wiped film molecular

distiller

Code: C 001

Service: separating unsaponifable fraction of oil from the

saponifiable fraction of avocado pear oil

Type: Vacuum column


Condenser: Code: CD 001

Service: Cooling the light phase oil

Type: Water cooler

Material: Stainless steel

Capacity: 0.2 m3

44

CHAPTER 7

7.0 Design of a centrifugal separator by DIAR ELIJAH GARANG CPE/1021/08

7.0.1 INTRODUCTION

Centrifuges are extensively used for separating fine solids from suspension in a liquid.

They are classified according to the mechanism used for solids separation:

Sedimentation centrifuges: in which the separation is dependent on a difference

in density between the solid and liquid phases (solid heavier).

Filtration centrifuges: in which separation of the phases is by filtration. The walls

of the centrifuge basket are porous, and the liquid filters through the deposited

cake of solids and is removed.

The choice between a sedimentation or filtration centrifuge for a particular application

will depend on:

Nature of the feed

Product requirements.

A variety of centrifugal filter or sedimentation designs are classified according to:

Mode of operation - batch or continuous.

Orientation of the bowl/basket - horizontal or vertical.

Position of the suspension and drive - overhung or under-hung.

Type of bowl - solid, perforated basket, disc bowl.

Method of solids cake removal.

Method of liquid removal.

7.0.2 SEDIMENTATION CENTRIFUGES

In solid liquid separations, the weaker force of gravity can be replaced by more

powerful centrifugal force to ensure more rapid settling.

Mode of operation

If a solid suspension in a liquid is rapidly whirled in a cylindrical container about the

cylinders axis, the vessel imparts to the solid liquid system centripetal force acting in

the direction towards the center of rotation. The content in return, exerts an equal and

opposite force, called the centrifugal force, outward on the walls of the container. It is

the centrifugal force that brings about the sedimentation of heavy i.e. coarse solid

particles through a layer of liquid.

A sedimentation centrifuge consists of the following parts:

A bowl or rotor where the centrifugal is employed to effect phase separation

A drive shaft to transmit power from the prime mover to the rotor

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Drive shaft bearings

A drive mechanism (usually an electric motor or turbine)

Seal system

A supporting framework

A casing to segregate the separated products

Types of sedimentation centrifuges

There are four main types of sedimentation centrifuges:

1. Tubular Bowl Centrifuge

It is a widely used machine. It comes in the popular ranges of 102-127 mm bowl

diameter and 760 mm length. The bowl is suspended from an upper bearing and drive

assembly is rotated at speed of about 15000 rpm. The feed suspension enters the bowl

under pressure through a statutory feed nozzle at the bottom of the bowl, gets

accelerated to rotor speed, moves upward and discharges out from the top.

Under the impressed centrifugal-force field both the solid particles and liquid receive

radial velocity. The particles whose trajectories intercept the wall deposited and the

rest escape with the effluent. Manual removal of the solids deposited against the bowl

wall is done when the mass of sediment solid is sufficient to degrade the quality. Solid

removal is facilitated by lining the bowl wall with parchment paper so that the

deposited solids can be taken out as a cylindrical package.

2. Multi-chamber Centrifuge.

This is a modified design of tubular-bowl centrifuge driven from below. It has a multi-

chamber bowl consisted of a series of tubular sections of increasing diameter arranged

to form a continuous tubular passage of stepwise increasing diameter.

The feed is charged to the smallest-diameter tube and as it passes through the

increasingly larger diameter tubes, it experiences increasingly higher magnitude of

centrifugal force. The heaviest particles settle in the smallest diameter tube while the

smaller and lighter particles migrate to the larger diameter zone where higher

centrifugal force comes into play. Such types of centrifuges may contain up to 6 annular

chambers in the bowl and the outer tubes may be spaced closer together to improve the

performance of the unit. Bowl holding capacity may range up to 75 liters of solids.

3. Disk Centrifuge

It consists of a stack of sheet metal disks 50-100 in number spaced at 0.4 to 3 mm and

set obliquely to form a half vertical angle of 35-50. These closely spaced disks are

actually cones of sheet metal set one above the other. Each disk is perforated (hole size

of 6mm to 12.75mm) and when the disks are assembled in the bowl, the perforations

give rise to several channels through which the liquid rises.

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Feed is admitted to the center of the bowl and it rises through the stack of disks whose

primary objective is to reduce the sedimentation distance. Once a solid particle reaches

the underside of one of the disks, it is virtually removed from the liquid as its chances of

re-entrainment in the effluent are very little. However due to the centrifugal force, it

continues to move outward until it is deposited on the bowl wall.

In hermetic disk centrifuge, characterized by closed feed and discharge, the feed

suspension enters the bowl through a hollow spindle at the bottom. The deposited solid

is removed manually, for which the machine is periodically stopped, the bowl is

disassembled and the disk stack is removed. The clarified liquid leaves through the

central port at the top.

Disk centrifuges range in diameters from 100mm to 500mm and develop settling forces

as high as 4000 to 14000 times the force of gravity. They are nearly as effective as

tubular centrifuges.

Figure 9: Disk bowl centrifuge

4. Continuous Horizontal Helical-Conveyor Centrifuge

It consists of a solid-wall bowl with a horizontal axis of rotation. The bowl may be

conical or cylindrical or very often a cylindrical bowl with conical end section. Feed

suspension enters the centrifuge through a stationary axial pipe to an appropriate point

in the bowl and it is sprayed radially outward onto an annular layer of liquid inside the

bowl. The clarified liquid flows through the overflow ports at the larger radius and

discharge out continuously.

The heavy solid sediment through the liquid phase, and are deposited on the inner

surface of the bowl. A helical screw conveyor extending the full length of the bowl

continuously transports the deposited solid to the other end of the bowl. Wash liquid

may be sprayed on the sedimented mass during its transport to dissolve out soluble

impurities. However washing becomes fairly effective on solid particles no smaller than

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80m.provided the deposited solid phase is reasonably porous. Drained sludge and

clarified liquor are drawn out through the different ports.

A differential speed is maintained between the bowl and the conveyor. The latter is

turned at a speed lower by 20 to 80 rpm than that of the bowl. Bowl diameter ranges

from 150mm to 1370mm; speed is 16 to 135 Hz (I