534 SHORT PAPERS Analyst, Vol. 102

Effects of Emulsifiers and Stabilisers on the Determination of Salt in Meat Products

M. Kapel, J. C. Fry,* J. Manii and D. R. Shelton Procter Defiartment of Food and Leather Science, The University of Leeds, Leeds, LS2 9JT

Keywords : Salt determination ; meat products ; emulsifiers ; stabilisers

In a paper on the determination of salt in meat and meat products,l it was mentioned that the method recommended by the British Standards Institution2 occasionally failed to yield a result. The procedure concerned consists of aqueous extraction of the salt and clarification of the extract with potassium hexacyanoferrate(I1) and zinc acetate, followed by Volhard titration of chloride. As is well known, the success of the last stage depends upon the coagulation of the silver chloride precipitate formed and the protection of its surface with nitrobenzene to prevent reaction with the thiocyanate titrant. In certain instances, how- ever, it was found that the silver chloride entered into a colloidal condition and failed to coagulate, with the result that no end-point could be obtained. As there had clearly been some modification of the colloidal properties of silver chloride, it seemed feasible to suppose

* Present address : County Analyst's Laboratory, 184 High Street, Hull, Humberside.

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July, 1977 SHORT PAPERS 535 that the presence of surface-active substances might be responsible for the failure of the Volhard titration, and this view received support from the fact that all of the unsuccessful determinations involved samples that contained emulsifiers or stabilisers. Indeed, the effects of such substances on the coagulation of silver halides have been noted by several

Accordingly, an investigation was mounted to determine the effects which the various types of surface-active materials commonly found in meat products might exert upon the Volhard titration. It should be mentioned that another method which has been recommended for the determination of salts obviates this difficulty by oxidation of the interfering materials with potassium permanganate.

Experimental Reagents

All of the inorganic reagents used were of analytical-reagent grade. Silver nitrate solution, 0.1 N. Potassium thiocyanate solution, 0.1 N. Indicator. A saturated solution of ammonium iron(II1) sulphate in water. Potassium hexacyanoferrate(II) solution. Potassium hexacyanoferrate(I1) trihydrate

Zinc acetate soZution. Zinc acetate dihydrate (220 g) and 30 ml of acetic acid, sp. gr. 1.05,

Nitric acid, 4 N. Nitrobenzene. AnalaR grade. Sodium chloride solution, a$proximately 10% ml V .

(106 g) was dissolved in water and diluted to 1 1.

were dissolved in water and diluted to 1 1.

Determination of Chloride in Meat An amount (approximately 100 g) of minced beef was prepared and the chloride content

determined on a 10-g aliquot in accordance with the method specified by the British Standards Institution.2 The chloride content was found to be negligible. The determination was repeated with the addition of 4 ml of 10% sodium chloride solution immediately before the extraction stage. The whole process was again repeated with the addition not only of the salt but also of an emulsifier or stabiliser as detailed in Table I.

TABLE I DETERMINATION O F CHLORIDE ADDED TO MEAT I N T H E PRESENCE OF

EMULSIFIERS OR STABILISERS Amount of

emulsifier or stabiliser Chloride found added, as NaC1,

Emulsifier or stabiliser Supplier Type* % % Fixa Rank Hovis McDougal Ltd. PP 0.25 3.7

3.7 Butterfield E P Butterfield Laboratories Ltd. PP 0.25 3.7

3.7 MSB Sol 7 Foodtech Ltd. PP 0.26 3.8

3.7 Admul GMS Food Industries Ltd. GMS 2 3.8

3.8

3.8

cellulose British Celanese Ltd. Carb 2 -3.6 3.8

-

-

-

- Hymono Food Industries Ltd. GMS 2 3.9

- Sodium carboxymethyl-

- Hydroxypropylmethyl-

cellulose British Celanese Ltd. Carb 2 2.7-3.7 6 3.7 -

* PP = polyphosphate; GMS = glyceryl monostearate; Carb = carbohydrate.

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636 SHORT PAPERS Analyst, Vol. 102

Determination of Chloride in Sodium Chloride Solution An amount of sodium chloride (4 ml of 10% m/V solution) was treated with an emulsifier

or stabiliser as listed in Table 11. A 20-ml aliquot was removed by pipette and its chloride content was determined by the titrimetric procedure specified in the British Standard.2

Some of the surface-active substances used could be brought into solution only by adherence to the instructions provided by the manufacturers.

The mixture was diluted to 200 ml.

TABLE I1 DETERMINATION OF CHLORIDE IN SOLUTION IN THE PRESENCE OF

SURFACE-ACTIVE SUBSTANCES

Emulsifier or stabiliser Fixa

Butterfield EP

MSB Sol 7

Admul GMS

Hymono

Sodium carboxymethyl-

Hydroxypropylmethyl-

Acacia

Agar

Glucose

Sucrose

Pectin

Starch

Gelatine

Albumin

Lecithin

cellulose

cellulose

Supplier Rank Hovis McDougal Ltd.

Butterfield Laboratories Ltd.

Foodtech Ltd.

Food Industries Ltd.

Food Industries Ltd.

British Celanese Ltd.

British Celanese Ltd.

BDH

BDH

British Sugar Corporation Ltd.

Extracted from lemons

Cornflour

BDH

BDH

Type* PP

PP

PP

GMS

GMS

Carb

Carb

Carb

Carb

Carb

Carb

Carb

Carb

Prot

Prot

Ph

Amount of emulsifier or

stabiliser added to 200 ml of solution/g

0.025

0.026

0.026

0.2

0.2

-

- -

-

-

0.2 -

0.2

0.2

0.2

0.3

-

-

-

- 0.4

0.2

0.2

0.2

0.2

0.2

-

-

-

-

-

-

Chloride found in 200 ml

(as NaCl)/g 0.37 0.37 0.37 0.37 0.39 0.39 0.38 0.38 0.39 0.39

0.25 0.38

--t 0.37

0.38 0.36 0.38 0.38

0.38 0.38

No end-point 0.38

0.38 0.24 0.39

0.38 0.39 0.39

No end-point

0.38

-t

--t

* PP = polyphosphate; GMS = glyceryl monostearate; Carb = carbohydrate; Prot = protein; Ph =

t End-point imprecise, value not easily repeatable. phospholipid.

Discussion As can be seen from the two tables, the surface-active materials used have been classified

under five headings : polyphosphates, glyceryl monoesters, phospholipids, proteins and carbohydrates. Those members of the first three categories which were examined did not appear to cause any difficulty in the Volhard titration.

Gelatine occasioned the type of interference described above, while albumin reacted chemically with silver nitrate. It must be pointed

Of the proteins, only two were investigated.

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Jzcly, 1977 SHORT PAPERS 537 out, however, that both of these substances would be removed in the clarification stage and could not be the source of any real difficulty in the British Standard method.

Glucose and sucrose did not appear to interfere, but all of the polysaccharides tried gave rise to the unfavourable effect on the colloidal properties of the precipitated silver chloride. In addition, sodium carboxymethylcellulose and hydroxypropylmethylcellulose also compli- cated the clarification stage, so that great difficulties in filtration were experienced. It must accordingly be concluded that the British Standard method for the determination of chloride in meat products is inapplicable to samples containing emulsifiers or stabilisers that are polysaccharide in nature. The same applies to those meat products which contain corn- flour as an ingredient.

We thank Professor A. G. Ward for his interest and encouragement and Rank Hovis McDougal Ltd., Butterfield Laboratories Ltd., Foodtech Ltd., Food Industries Ltd. and British Celanese Ltd. for gifts of samples. Dr. J. E. McKay kindly supplied a sample of lemon pectin. One of the authors (J.C.F.) thanks J. Sainsbury Ltd. for a maintenance grant and another (D.R.S.) thanks the Science Research Council. We also gratefully acknowledge the general financial assistance provided by J. Sainsbury Ltd.

References 1. 2.

3. 4. 5. 6. 7. 8. 9.

Kapel, M., and Fry, J. C., Analyst, 1974, 99, 608. British Standards Institution, “Methods of Test for Meat and Meat Products, Determination of

Schneider, L., J . Am. Chem. SOC., 1918, 40, 591. Kolthoff, I. M., 2. Analyt. Chem., 1927, 71, 235. Kolthoff, I. M., Lauer, W. M., and Sunde, C. J., J . Am. Chem. SOC., 1929, 51, 3273. Lottermoser, A., and Lorenz, W., Kolloidzeitschrzft, 1934, 60, 201. Stalzer, R. F., Dillon, E. S., and Vosburgh, W. C., Analyt. Chem., 1950, 22, 952. Dean, R. B., Wiser, W. C., Martin, G. E., and Barnum, D. W., Analyt. Chem., 1952, 24, 1638. Hanson, N. W., Editor, “Official, Standardised and Recommended Methods of Analysis,” Second

Received October lSth, 1974 Amended February 9th 1977

Accepted February 23rd. 1977

Chloride Content,” British Standard 4401 : Part 6 : 1970.

Edition, Society for Analytical Chemistry, London, 1973, p. 165.

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