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 beta-lactoglobulin and alpha(S1)-casein from commercially available dairy products before, during, and after in vitro digestion. All major milk proteins, except beta-lactoglobulin, were degraded to smaller peptides during the gastric phase in all investigated products. After the gastric phase, a shortened fragment of beta-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 alpha(S1)-casein than from beta-lactoglobulin. The monitoring of generation of specific beta-lactoglobulin and alpha(S1)-casein peptide profiles by liquid chromatographyemass 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. (C) 2013 Elsevier Ltd. All rights reserved.