Amino acid composition of some fish products and casein.

It has been shown that when vacuum-dried cod muscle is heated under controlled conditions of temperature and moisture the value of the protein as a supplement to cereal proteins diminishes (Carpenter, Ellinger, Munro & Rolfe, 1957). After heat treatment of the cod muscle, lysine was found to be the limiting amino acid in the gross protein value (GPV; Heiman, Carver & Cook, 1939) chick test and quality could be related to the available lysine content of the material. Yet, the supplementation of heated cod muscle with free lysine did not raise the GPV to the level obtained with the unheated cod muscle. Analyses were carried out to determine whether damage by heat treatment was reflected in the amino acid composition of acid hydrolysates prepared from heated cod muscle. Analyses are also reported for two other protein concentrates. Casein was chosen as the standard used in the GPV determinations and for comparison with other analyses in the literature. A sample of white-fish meal of known history and GPV was chosen as a protein used as standard in practical feeding trials, and for comparison with the cod-muscle preparations.