The effects of heat treatment on the nutritive value of coconut meal, and the prediction of nutritive value by chemical methods

Abstract

Coconut meal, the residual product after extraction of oil from the dried flesh of the coconut, is available in many parts of the world. In large areas of the tropics it is the only locally produced ingredient of feeding-stuffs that contains moderate amounts of protein (18-25 yo of the dry matter). The results of research on the nutritive value of this product are, however, disappointing, and the tendency is to use coconut meal in ruminant feeding rather than in the diets of non-ruminants, although it is for the latter that the need is more urgent. Results for the nutritive value of coconut meal have been reviewed by Mitchell, Hamilton & Beadles (1945) and Curtin (1958). It would seem likely that a considerable amount of damage is done to the protein of coconut meal during processing and that a product of better quality could be obtained were less severe methods used. Jones, Finks & Johns (1923) found no difference in biological value between solvent-extracted and screw-pressed meals, but later experiments by Mitchell et al. (1945) demonstrated that coconut meal produced by an extraction process in which the temperature never exceeded 75" had a higher biological value than a product prepared by the 'usual drastic methods'. Various workers (Lea & Hannan, 1950; Henry & Kon, 1950; Bensabat, Frampton, Allen & Hill, 1958) have shown that one of the changes accompanying severe processing conditions is a combination of the e-amino group of lysine with the keto group of a carbohydrate. It has been suggested that this reaction biologically inactivates the amino acid and it has been shown that for certain proteins the measurement of ' available lysine ' provides an indication of nutritive value (Carpenter, Ellinger, Monroe & Rolfe, 1957; Lea, Parr & Carpenter, 1960; Clegg, 1960; Boyne, Carpenter & Woodham, 1961). In view of the fact that figures quoted by Curtin (1958) and Peters (1960) indicate that lysine is the most limiting amino acid in coconut protein, it is probable that inactivation of lysine during processing is one factor contributing to the low nutritive value of commercially produced coconut meal. I t has been shown for other feed ingredients that the solubility of protein in various solvents is decreased by heating and that this effect may be indirectly related to