The release of peptides and glycopeptides by the action of heat on cow's milk

Abstract

Summary The release, as a result of heat treatment on cow's milk, of peptides and glycopeptides which are soluble in the 12% trichloroacetic acid (TCA) filtrate of the milk has been studied. The results showed that the amount of peptides released increased with temperature and duration of the heat treatment. There were differences between milks in their response to a given heat treatment. Glycopeptides were released at temperatures as low as 50 °C but not at 37 °C. A comparison was made of the glycopeptides released by heat treatment and of those released from κ-casein by the action of rennin on the milk. This showed that N-acetyl neuraminic acid, D -galactose and 2-acetamido-2-deoxy- D -galactose were invariably present in both groups of glycopeptides. D -Mannose was also present in the glycopeptides released by heat but was detected on the glycopeptides released by rennin in only one of 6 experiments. It is suggested that glycopeptides released by heat may be derived from κ-casein but that a definite conclusion cannot be reached at present because of lack of information on the carbohydrates attached to other milk proteins.