Abstract/Summary

In this study, ultrafiltered goat milks fermented with the classical starter bacteria Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarus subsp. thermophilus or with the classical starter plus the Lactobacillus plantarum C4 probiotic strain were analyzed using ultra-high performance liquid chromatography-quadrupole-time-of-flight tandem mass spectrometry (UPLC-Q-TOF-MS/MS) and/or liquid chromatography-ion trap (LC-IT-MS/MS). Partial overlapping of the identified sequences with regard to fermentation culture was observed. Evaluation of the cleavage specificity suggested a lower proteolytic activity of the probiotic strain. Some of the potentially identified peptides had been previously reported as angiotensin converting enzyme (ACE)-inhibitory, antioxidant and antibacterial and might account for the in vitro activity previously reported for these fermented milks. Simulated digestion of the products was conducted in presence of a dialysis membrane to retrieve the bioaccessible peptide fraction. Some sequences with reported physiological activity resisted digestion but were found in the non-dialyzable fraction. However, non-previously detected sequences such as the antioxidant αs1-casein 144YFYPQL149, the antihypertensive αs2-casein 90YQKFPQY96 and the antibacterial αs2-casein 165LKKISQ170 were found in the dialyzable fraction of both fermented milks. Moreover, in the fermented milk including the probiotic strain, the k-casein dipeptidyl peptidase IV inhibitor (DPP-IV) 51INNQFLPYPY60 as well as additional ACE-inhibitory or antioxidant sequences could be identified. With the aim to anticipate further biological outcomes, quantitative structure activity relationship (QSAR) analysis was applied to the bioaccessible fragments and led to propose potential ACE inhibitory sequences.