ACE-inhibitory activity of probiotic yoghurt

In this study, the in vitro angiotensin-converting enzyme (ACE)-inhibitory (ACE-I) activity of peptide fractions from different yoghurt batches was assessed. Inhibition of ACE activity resulted in an overall antihypertensive effect. Yoghurts were prepared either using a sole yoghurt culture including Lactobacillus delbrueckii ssp. bulgaricus Lb1466 and Streptococcus thermophilus St1342, or L. acidophilus L10, L. casei L26 and Bifidobacterium lactis B94 in addition to yoghurt culture. ACE-I activity was determined at weekly intervals during 28 days of cold storage. Peptide fractions showing high ACE-I activity were further purified using multiple-steps of RP-HPLC. All probiotic yoghurts showed appreciable ACE-1 activity during initial stages of storage compared with the control yoghurt, with a significant (p < 0.05) decrease afterwards. The ACE-I activity ranged from IC50 of 103.30-27.79 mu g mL(-1) with the greatest ACE inhibition achieved during first and third week of storage. The in vitro ACE-I activity could be related to the peptide liberation via degradation of caseins. In total, 8 ACE-I peptides were characterized originating from alpha(s2)-casein (1), K-casein (2) and beta-casein, of which two well-known ACE-inhibiting peptides, namely Val-Pro-Pro (VPP) and Ile-Pro-Pro (IPP), were identified. These peptides are already used in commercial products. (c) 2007 Elsevier Ltd. All rights reserved.