Biological activities and peptidomic profile of in vitro-digested cow, camel, goat and sheep milk

In vitro digestibility, selected biological activities and digested products of proteins from skimmed cow, camel, goat and sheep milk were compared. The harmonised in vitro INFOGEST digestion model and mass spectrometry were combined to identify peptides. Goat milk had the highest digestibility, sheep milk the highest angiotensin-converting enzyme (ACE)-inhibitory activity after digestion and cow milk the highest dipeptidyl peptidase-IV (DPP-IV)-inhibitory activity. After in vitro digestion of the milk samples, 522 peptides were identified. Goat and sheep milk showed the highest peptide sequence similarity with 151 common peptides. Thirteen, forty-three and twenty peptides with previously demonstrated antioxidant, ACE-inhibitory and DPP-IV-inhibitory activities, respectively, were found. Nineteen bioactive peptides in common were released from the different milk types. Despite limitations related to analysis of one milk sample for each species, possible differences in physiological functions after ingestion of milk from different species are suggested; this requires confirmation by in vivo testing.