Abstract
The studies were made to establish the reliable and simplified methods of hydrolyses of several food proteins for microbial assay of the amino acids composing these proteins. Assay using the titrations of the acid produced by the test organisms gave maximum values of the amino acids when the proteins were hydrolysed in sealed-tubes at 120°C for 1 hour for glycine, 2 hours for cystine, 3 hours for tyrosine, 4 hours for lysine and serine, 6 hours for methionine, leucine, isoleucine, aspartic acid, glutamic acid, histidine and proline, 8 hours for alanine and valine, 10 hours for arginine all with 4N hydrochloric acid, while 8 hours for threonine and phenylalanine both with 3N hydrochloric acid. Tryptophan was well assayed, with minimum loss, from a hydrolysate prepared by 15-hour sealed-tube hydrolysis at 120°C with 4N hydroxide solution, and the value obtained was compared with that determined by colorimetric method. Effects of the presence of varied quantities of starch upon the assay values of several amino acids were also examined following these hydrolysis procedures.
Twenty four food proteins were analyzed by these hydrolysis methods and their amino acid compositions were determined, comparing the lysine contents with those determined as available lysine by Carpenter's method.
