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WHP guideline

Guideline for edible cottonseed protein flours and related products


Processed cottonseed protein products in the form of defatted flours with 45 to 50 per cent protein have been produced commercially for food use in several countries for many years and have been shown to be entirely suitable as protein supplements in cereal food mixtures (maize, wheat, rice) (1, 3, 4, 5, 11, 26, 28;. For example, the corn based product "Incaparina" has been marketed in the Central Americas since the 1950s (3). Concentrates with protein levels greater than 65 per cent have been produced on a semi-commercial scale by various technologies (13). Production of functional protein concentrates, isolates (90 per cent or more of protein), and textured protein products have been demonstrated (9, 18, 21). Utilization of cottonseed protein materials in processed foods has not, however, achieved the level that has been attained by similar products derived from soybeans (1).

Generally, defatted edible cottonseed protein materials are produced following removal of the edible oil, although full-, medium-, and low-fat flours have also been manufactured. Ready to eat cereall-cottonseed protein mixtures have been prepared by a simple extruder-cooker technology (16). Various traditional oil recovery processes are normally not operated by the cottonseed oil industry in a manner that safeguards the quality of the residual protein However, these technologies can be upgraded in terms of selection of suitable raw materials, more careful control of heat in processing, and better sanitary supervision, to permit production of safe and nutritious food-grade products

A primary technical objective in the processing of edible cottonseed protein flours, as well as products used for feeding monogastric animals (swine, poultry), is the reduction in toxic impact of the pigment gossypol, a characteristic constituent of cottonseed (2, 3, 5, 27). Some concentrate processes may strive for the virtually complete removal of gossypol (13,17). Raw cottonseed used for such purposes may be selected for lower than-normal gossypol levels and for freedom from the fungal toxin, aflatoxin. Wherever available, the new "glandless" (i.e., genetically gossypol-free) cottonseed varieties may be used (19, 22).

It should be recognized that a primary limitation to the availability of cottonseed of a quality ideal for the production of safe, sanitary, edible protein products relates to the obvious fact that the cotton varieties grown almost everywhere are chosen, not for the food-use quality of the seed protein, but on the basis of desirable agronomic characteristics and maximum yield of cotton with preferred fibre properties. The new glandless varieties referred to may prove an exception in this regard (22).

In this discussion, emphasis will be placed on desirable quality and sanitary characteristics of cottonseed protein products whose processing is feasible in developing countries, following good food manufacturing practices, and using indigenous technologies and oilseed processing facilities frequently available in their cotton-producing regions.


Aflatoxin-free, high quality cottonseed should be cleaned, delinted, and dehulled to release kernels or meats. The meats should be suitably prepared for oil recovery employing either continuous screw-pressing, pre-press solvent extraction, or direct solvent extraction. Cleanliness is mandatory during processing of kernels for oil to allow production of edible-grade meal. Minimization of heat, moisture, and processing time is essential to maintain protein quality and a free gossypol content of not more than 0.045 per cent in the meal. Temperatures should not exceed 120 C (2, 3, 13). An important processing objective using such technology is to "bind" most of the free gossypol to the protein in such a manner that the protein nutritive quality is minimally impaired.

Other processes aiming at virtually complete removal of gossypol, but that are not now in commercial use, include the liquid cyclone process (13), the application of acetone (25), the membrane isolate process (17), and the aqueous extraction process 113).


Cottonseed, suitable for preparing edible products, should have not more than 1.0 per cent foreign matter, not more than 10 per cent moisture, not more than 1.8 per cent free fatty acids in the oil, and less than 5 per cent of discoloured kernels.

The total gossypol should occur in the seed as free gossypol i.e., the seed should not be subjected to conditions before processing that cause gossypol to bind to Iysine. During storage, cottonseed should be maintained at moisture levels of less than 12 per cent and at temperaturas below 50 C. Sodium propionate as a preservativa (fungal inhibitor) may be present at a maximum level of 0.3 per cent by weight. Solvents and lubricante should be food-grade. Hexane is preferred as the solvent. Benzene or chlorinated hydrocarbon solvents should not be used.

Another source of food-grade material is glandless cotton varieties producing gossypol-free cottonseed (22). This crop should be grown separately to prevent cross-pollination with glanded varieties. Additionally, the glandless cottonseed should be handled and processed with equipment thoroughly free of glanded material (23).

4.1 Composition

Component Meal/flour products
By screw press or pre-press solvent extraction By degossypolization processes (typical values)
Moisture, max. % (6, 7, 8) 10 5.0
Crude protein (NX6.25), min. %(7) 45 65
Fat, max. % (8) 6 1.5
Total ash, max. % (8) 5 9
Acid-insoluble ash, max. % (7) 0.1 0.1
Crude fibre, max. % (8) 5 2.5
Free gossypol, max. % (8) 0.06 0.045
Total gossypol, max. % (8) 1.2 0.3
Available Iysine, min. (g/16gN) (15, 24, 26) 3.6 3.9
Soluble protein (% of total protein) min. (7, 20) 65 99
Hexane, max. ppm (12) 170 60
Arsenic, max. ppm (10) 0.2 0.2

4.2 Microbiological and Sanitary Characteristics

4.2a Microbiological (for methods see 6, 7). The following product characteristics are recommended for edible cottonseed products.

Organism Total plate count of cottonseed product
Viable organisms, max. 50,000/gm
Yeast and mould count, max. 100/gm
Coliform Negative
E. coli Negative
Staphylococci Negative
Salmonella Negative

4.2b Acid Insoluble Ash (for method see 7). This analysis indicates relative contamination with extraneous minerals originating from sand and dirt. The value in any event should not exceed 0.1 per cent.

4.2c Insect and Rodent Contamination (7). Edible cottonseed products, or their mixtures with cereal foods, should be essentially free of insects, insect fragments, rodent hairs, and rodent excreta, as determined by the method indicated.


Several chemical and biological tests have been proposed to evaluate and control the protein quality of processed cottonseed protein materials. For routine testing and process control, the Protein Dispersibility Index (PDI) is useful (for method see 6, 7, 20), since it reflects the degree of insolubilization of the protein component in proportion to the extent (temperature/time) of heat treatment. Available Iysine (for method [s] see 15, 24, 26) is a chemical method considered to provide a good prediction of protein nutritive quality when the latter is determined by biological procedures. Protein nutritional quality evaluation by animal (rat) assay is considered to be a primary laboratory reference procedure. The Protein Efficiency Ratio (PER) should be 1.6 or higher, corrected to a value of 2.5 for a control casein diet (for method see 8).


Because of the possibility of contamination of cottonseed with aflatoxin due to exposure to excessive moisture levels before harvesting and in storage, the raw material used for food processing should be selected following careful sampling for freedom from this fungal toxin. A chemical assay may be conducted for this purpose (for method[s] see 8, 29). Ideally, the product should contain less than 30 - 50 micrograms (mcg) per kilogram (30 - 50 parts per billion) of total aflatoxin. The Indian Standards institution suggests a maximum aflatoxin level of 60 mcg/kg for edible products produced in that country.

Review and General

1. Journal of the American Oil Chemists Society (special issue March 1979). Vol 56, no. 3,483 pp., "Proceedings of a World Conference on Vegetable Food Proteins." (American Oil Chemists Society, 508 S. Sixth St., Champaign, III.)

2. Processed Plant Protein Foodstuffs, A. Altschul, ed. (Academic Press, New York, 1958).

3. Protein-Enriched Cereal Foods for World Needs, Max Milner, ed, (American Association of Cereal Chemists, St. Paul, Minn., 1969).

4. Protein Resources and Technology: Status and Research Needs, 629 pp. ed. by Max Milner, N.S. Scrimshaw, and D.l.C. Wang. (Avi Publishing Co., Inc., Westport, Conn., 1978.)

5. The PAG Compendium, (Worldwork Press Ltd., New York, 1975.)

Analytical Methods and Literature Citations

6. American Association of Cereal Chemists, Cereal Laboratory Methods (AACC, St. Paul, Minn, 1968).

7. American Oil Chemists Society, Official and Tentative Methods (third ed. AOCS, Champaign, III.,1968)

8. Association of Official Analytical Chemists, Official Methods of Analysis (twelfth ed., and supplements. AOAC, Washington DC, 1975)

9. Berardi, L.C., W.H. Martinez, and C.J. Fernandez, "Cottonseed protein isolates: two-step extraction procedure," Food Technol., 12 (10) :75 (1969).

10. Berkhout, H.W. and C.H. Jangen, "Colorimetric determination of arsenic after volatilization as arsine," Chemist Analyst, 43:60 (1954).

11. Cater, C.M., K.F. Mattil, W.W. Meinke, M.V. Taranto, and J.T. Lawhon, "Cottonseed protein food products," J. Am. Oil Chem. Soc., 54:90A (1977).

12. Fore, S.P. and H.P. Dupuy, "A rapid procedure for determination of residual hexane in oilseed meals and flours," J. Am Oil Chem. Soc., 49:129 (1972).

13. Gardner, H.K., R.J. Hron, and H.L.E. Vix, "Removal of pigment glands (gossypol) from cottonseed," Cereal Chem., 53:549 (1976).

14. Green, J,R., J.T. Lawhon, C.M. Cater, and K.F. Mettil, "Utilization of whole undefatted glandless cottonseed kernels and soybeans to protein-fortify corn tortillas," J, Food Sci., 42:790 (1977).

15. Hurrell, R.F. and K.J. Carpenter, "An approach to the rapid measurement of 'Reactive Lysine 'in foods by dye binding," Proc. Nutr. Soc, 35:23A (1976).

16. Jansen, G.R., J.M. Harper, and L. O'Deen, "Nutritional evaluation of blended foods made with low cost extruder cooker," J. Food Sci., 43:912 (1978).

17. Lawhon, J.T., D. Mulsow, C.M. Cater, and K.F. Mattil, "Production of protein isolates and concentrates from oilseed flour extracts using industrial ultrafiltration and reverse osmosis,"J. Food Sci., 42 (2):): 289 (1977)

18. Lawhon, J.T., L.W. Rooney, C.M. Cater, and K.F. Mattil, "Evaluation of a protein concentrate product from glandless cottonseed flour by a wet extraction process," J. Food Sci., 37:778 (1972).

19. Lusas, E.W" J.T. Lawhon, S.P. Clark, S.W. Matlock, W.W. Meinke, D.W. Mulson, K.C. Rhee, and P.J. Wan, "Potential for edible protein products from glandless cottonseed," in Proceedings of Glandless Cottonseed Conference, Dallas, Texas, 13 - 14 Dec. 1977 (USDA, Agricultural Research Service, Beltsville, Md.)

20. Lyman, C.M., W.Y. Chang, and J.R. Couch, "Evaluation of protein quality in cottonseed meals by chick growth and by a chemical index method," J. Nutr., 49:679 (1953).

21. Martinez, W.H., L.C. Berardi, and L.A. Goldblatt, "Potential of cottonseed: products, composition and use, 3rd International Congress," Food Sci. Technol., 3:248 (1970).

22. McMichael, S.C., "Hopi cotton: a source of cotton free of gossypol pigments, "Agron. J., 51:630 (1959).

23. Miravelle, R.J., "Evaluation of production of glandless cotton, in Proc. Conf. on Protein-Rich Food Products from Oilseeds, New Orleans, La. 15 - 16 May 1968. (USDA Southern Regional Research Center, P.O. Box 19687, New Orleans, La.)

24. Nair, B.M., A. Laser, Burvall, and N.G. Asp, "Gas chromatographic determination of available Iysine," Food Chem., 3:283 (1979).

25. Pons, W.A. and P,H. Eaves, Aqueous acetone extraction of cottonseed. U.S. patent 3,557,168 (1971).

26. Rao, S.R., F.L. Carter, and V.L. Frampton, "Determination of available Iysine in oilseed meal proteins, "Anal. Chem., 35:1927 (1963).

27. Smallwood, N.J., "Significance of gland pigments in processing, storage, handling and utilization of cottonseed oil," n: Proc. Conf. Glandless Cotton- Its Significance, Status and Prospects (US Dept. of Agriculture, Agricultural Research Service, New Orleans, La., 1978).

28. Wadsworth, J.l., R.E. Hayes, and J.J. Spadaro, "Optimum protein quality food blends," Cereal Foods World, 24 (7):274 (1979).

29. Whitaker, T.B., M.F. Whitten, and R.S. Munroe, "Variability associated with testing cottonseed for aflatoxin," J. Am. Oil Chem. Soc" 53:502, (1976).

Note: These Guidelines must be reviewed and revised periodically; criticisms, comments, and additions will therefore be welcomed by the UN University

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