Influence of Genetic Variants and Sialylation of Purified Κ-Casein on Peptide Release During in Vitro Digestion

In the present study, digestion pattern of purified bovine κ-casein (κ-CN) variants A, B, E as well as desialylated variant B, using INFOGEST 2.0 in vitro gastrointestinal digestion were investigated using peptidomics. Peptide profiles of the digests were identified and quantified using ion abundancies by liquid chromatography electrospray quadropole time of flight mass spectrometry (LC-ESI/Q-TOF MS/MS). Results showed that the κ-CN variants A and E had comparable digestion patterns at most digestion time points. In the in vitro gastric and in the initial intestinal phases fewer peptides and with lower total abundances were identified for variant B compared to variants A and E, indicating a slower digestion rate for κ-CN B. By desialylation, the digestion rate of desialylated variant B in both gastric and initial intestinal phases increased compared to the natural sialylated counterpart. Bioinformatics search revealed nine potential bioactive peptides released from all three variants A, B and E by the in vitro intestinal digestion, with four additional potential bioactive peptides being released after desialylation of κ-CN B.