Abstract: This study attempted to investigate the effect of Lactobacillus helveticus on proteolysis and angiotensin-converting enzyme (ACE) inhibitory activity in Cheddar cheese during ripening. Those inoculated with L. casei, L. rhamnosus or nothing were used as controls for comparison. The digestion stability of cheese was evaluated at the time of the maximum ACE inhibitory activity. The results showed that during ripening, there was no significant difference (P > 0.05) in the number of viable bacteria among cheeses supplemented with probiotic bacteria, but they were all higher than that in the control cheese samples. The degree of proteolysis and ACE inhibitory activity in probiotic cheeses were higher than those in the control cheese samples significantly (P < 0.05). L. helveticus cheese had the strongest proteolysis degree and ACE inhibitory activity (79.71%). After simulated digestion, the viable bacterial count of L. helveticus cheese decreased by 14.30%, the ACE inhibitory activity increased significantly up to 86.06% (P < 0.05), and the polypeptide concentration increased to 2.81 mg/mL. Furthermore, it was found that the ACE inhibitory activity of peptides above 10 kDa increased while the ACE inhibitory activity of peptides below 10 kDa decreased after digestion. In addition, addition of L. helveticus did not influence the overall acceptance of cheese. Therefore, L. helveticus can promote the production of ACE inhibitory peptide and enhance its activity. The increased activity after digestion is mainly related to the degradation of macromolecular peptides.

Key words: Lactobacillus helveticus; Cheddar cheese; angiotensin-converting enzyme inhibitory peptide; gastrointestinal digestion; molecular mass