Impact of milk processing on the generation of peptides during digestion

Milk processing may induce changes in dairy product composition and influence digestibility and nutrient bioavailability. Differences in protein degradation and peptide generation were studied for β-lactoglobulin and α_S1-casein from commercially available dairy products before, during, and after in vitro digestion. All major milk proteins, except β-lactoglobulin, were degraded to smaller peptides during the gastric phase in all investigated products. After the gastric phase, a shortened fragment of β-lactoglobulin was identified in the non-fermented dairy products, underlining differences in protein conformation due to the fermentation process. During the gastric phase, greater numbers of small peptides were generated from α_S1-casein than from β-lactoglobulin. The monitoring of generation of specific β-lactoglobulin and α_S1-casein peptide profiles by liquid chromatography–mass spectrometry allowed the identification of potential bioactive peptides. Peptides with satiety-influencing DPP-4 inhibiting properties were monitored and quantities were compared between products to identify promising targets for the development of new health promoting products.