Effect of heating on clot formation and milk protein digestion during in vitro infant gastric digestion

Samenvatting

Background: Heating of milk proteins can influence their gastric clot formation and protein hydrolysis. Usually only the soluble proteins are analyzed, leading to an incomplete picture of protein digestion. Therefore, we aimed to study the effect of heating on infant gastric digestion of milk proteins by analyzing both the soluble digesta and the insoluble clot.

Methods: Unheated and heated skim milk (80°C, 30 min) was digested by use of in vitro infant gastric digestion. The protein compositions of both the soluble digesta and clots were measured to determine protein hydrolysis. The clot structure was analyzed by confocal laser scanning microscopy.

Results: A tight clot with small pores was formed from unheated milk, whereas a looser clot with larger pores was formed from heated milk. Intact caseins were absent in soluble digesta, but were present in the clots along with intact whey proteins and peptides. Caseins were digested more slowly in the clots from heated milk than in those from unheated milk.

Conclusion: Heating leads to a looser gastric clot structure and a slower casein digestion. Intact caseins were only detected in the clots, showing that analyzing both soluble digesta and insoluble clots is needed to study gastric milk protein digestion.