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 preschool 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 proteolysis 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 fermented 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.