Influence of heat treatment of bovine skim-milk on in vivo digestion in rat stomach

Abstract

The effect of heat treatment on in vivo gastric digestion of bovine milk proteins was studied on rats given skim-milk, UHT sterilized skim-milk and autoclaved skim- milk at 120 oc during 20 min. Stomach contents were analysed after 30, 60 and 240 min of digestion. The heat treatment resulted in an acceleration of the acidification of stomach contents and of gastric emptying rate and appeared to increase the hydrolysis of the caseins remaining into the stomach. These phenomena were ail more prononced as the heat treatment was more important. With raw skim-milk the clotting of the diet induced a preferential emptying of whey proteins. After the heat treatment a slow down of gastric emptying of these -proteins was observed. Consequently the amino acid composition of the stomach contents reached those of the whole whey during digestion a- time. b-lactoglobulin is resistant to the action of gastric proteinases although lactalbumin, at favorable pH conditions, become susceptible to these enzymes.