Impact of casein-to-whey protein ratio on gastric emptying, proteolysis, and peptidome profile of fermented milk during in vitro dynamic gastrointestinal digestion in preschool children

The effects of casein-to-whey ratios (i.e., 4:1, 2:1, 1:1, 1:1.5) in fermented milk on gastric emptying, proteolysis and intestinal peptidome were investigated using an in vitro dynamic stomach-intestine system mimicking pre-school children digestion. The gastric emptying rate varied insignificantly among the milk samples. After 120 min digestion, the protein digestibility was found in the range of 73.3-93.5 %, with the highest extent of pro-teolysis observed at a casein-to-whey ratio of 2:1 due to the fewest gastric protein aggregates and relatively abundant caseins. Intestinal peptides derived from caseins or whey proteins showed a positive correlation with their parent protein content. The most abundant bioactive whey peptides were found at casein-to-whey ratio of 1:1.5 after intestinal digestion. These findings demonstrated the importance of protein compositions in fer-mented milk on the gastrointestinal proteolysis and peptide release in vitro. This will be meaningful for future development of milk products that are more suitable for children.