Abstract
Soy protein isolate (SPI) was enzymatically modified to produce oligopeptide mixtures having methionine at approximate levels of 1% and 3%. Each of them had an average molecular weight of slightly lower than 1, 000 daltons, They were compared with corresponding amino acid mixtures as well as with SPI for protein efficiency ratio (PER) and several other parameters. Normal and protein-malnourished rats were used as subjects for the comparison tests. When malnourished rats were subjected to a feeding test at a methionine level of 100 in nitrogen source, the oligopeptide mixture, OPM1, gave a significantly higher PER value than any of SPI and the amino acid mixtures. At a methionine level of 3%, both normal and malnourished rats utilized the oligopeptide mixture, OPM3, with higher efficiency than the amino acid mixture. These results suggest that the oligopeptide mixtures were utilized similarly to or more efficiently than SPI from which they were derived and the amino acid mixtures with exactly simulated amino acid composition.
