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UNU - WHP guidelines

Guidelines for preparing food-grade groundnut (peanut) flour


Guidelines for preparing food-grade groundnut (peanut) flour

1. Introduction

Preserving the nutritive value of groundnut (peanut) flour and maintaining optimum sanitary conditions in its preparation are the vital objectives of the processing and quality standards here proposed, because groundnut flour may be used as a major source of protein in foods for infants and children. The quality limits proposed are considered to be minimal for safe, sanitary products. Special care in all phases of preparation - selection of raw materials, control of processing, packaging, and handling - is necessary. The overall technology for the processing of peanuts and production of peanut flour is described in available references.

2. Process

Conventional equipment for heating, blanching, removal of oil, grinding, etc. should be used end operated in a sanitary manner. Maximum temperature in cooking and in oil-removal by pressing should not exceed 120C (250F). If solvents are used they should be food grade (PAG Guideline No. 1). Hexane is to be preferred. Desolventization should be done at temperatures between 80C (178 F) and 1 20C (250 F) and the meal rapidly cooled.

2.1 Raw Materials Raw materials shall consist of cleaned, split, deskinned, and dehearted kernels, derived from high-quality groundnuts containing less than 9 per cent moisture by removal of foreign material, shell, culls, or otherwise defective kernels. Hand-picking and/or electronic sorting is recommended as a final step to remove mouldy kernels which may carry aflatoxin.

3. Product

3.1 Composition
3.1.1 Chemical (AOAC Official Methods of Analysis)
(see refs. 2 - 5)

Moisture (%) 7.0 to 11.0
Fat (%) 8.0 maximum
Free fatty acid (% of oil) 1.0 maximum
Protein, N x 6.25 (%) 48.0 minimum
Available lysine, 9/16 9 N 2.5 minimum
Ash (%) 4.5 maximum
Crude fibre (%) 3.8 maximum

3.1.2 Physical

Particles: No course or gritty particles
Colour: Light tan or buff

3.1.3 Organoleptic characteristics

Odour: Should be free of mustiness, the smell of solvent or anything unpleasant
Taste: Should be smooth to the tongue

3.1.4 Sanitary

3. 1.4. Bacteriological

Total bacteria plate count Less than 20,000/9
E. cold 0/109
Salmonella 06309
Other pathogens 0 Insect and rodent contaminations Free of insects, insect fragments, rodent hairs, and rodent excrete Extraneous mineral matter such as sand and dirt Acid insoluble ash7 Less than 0.1%

3.1.5 Nutritional In peanut flour, a high value for available Iysine (also frequently referred to as free epsilon-amino Iysine) is desirable since it appears to be correlated positively with protein nutrition values as determined by con trolled rat-feeding trials. Soluble protein value determined by the AOCS or AACC9 procedure for NSI (Nitrogen Solubility Index) may be used to monitor heat treatment employed during processing. NSI values of 55 - 85 per cent are preferred to assure inactivation of enzymes and assure high avail" able Iysine values.

3.1.6 Toxicological Because of the possibility of contamination of groundnuts with aflatoxin, a chemical assay should be com ducted on the final groundnut product prior to use by humans. A product should contain less than 30 - 50 micrograms/kg (30 - 50 ppb) total aflatoxins. For method, see AOAC 26.065.2

3.2 Precautions and Warnings Prior to roasting and blanching, the kernels should contain less than 9 per cent moisture and the oil less than 0.5 per cent free fatty acids. Lubricants used should be free from chlorinated or brominated compounds and must be of a type suitable for the processing of food.

A minimum moisture value of 7.0 per cent was specified because values below this are associated with acceleration of fat rancidity during storage.


1. J. G. Woodroof.1973. Pliant: Production, Processing and Products, 2nd ad. Avi Publishing Co., Westport, Conn,, USA.

2. Association of Official Agricultural Chemists.1975. Official Methods of Analysis, 12th ad. AOAC, Washington, D.C.

3, R. F. Hurrell and K. J. Carpenter. 1976. Proc. Nutr. Soc. 35:23A. See also R. F. Hurrell and K. J. Carpenter.1975. Br. J. Nutr. 33:101.

4. A. L. Lakin.1973. In Proteins in Human Nutrition (J. W. G. Porter and B. A. Rolls, editors), p.179. London and New York: Academic Press.

5. L. Sandler and F. L.Warren.1974.Analyt. Them. 46:1870.

6 . Bacteriological Analytical Manual for Foods, 1976, 4th ed. AOAC; Washington, D. C.

7. A. G. Woodman. 1941. Food Analysis. McGraw-Hill, New York.

8. American Oil Chemists Society, Official Methods of Analysis. Method Ba 11 - 65 (reapproved 1975).

9. American Association of Cereal Chemists, Official Methods of Analysis. Method 46 - 23 (1965).

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