Release and Identification of Angiotensin Converting Enzyme-Inhibitory Peptides as Influenced by Ripening Temperatures and Probiotic Adjuncts in Cheddar Cheeses

The aim of the study was to examine the release of angiotensin-converting enzyme (ACE)-inhibitory peptides in Cheddar cheeses made with starter lactococci and Bifidobacterium longum 1941, B. animalis subsp. lactis LAFTI B94, Lactobacillus casei 279, Lb. casei LAFTI L26, Lb. acidophilus 4962 or Lb. acidophilus LAFTI L10 during ripening at 4 and 8 degrees C for 24 weeks. ACE-inhibitory activity of the cheeses was maximum at 24 weeks. Cheeses made with the addition of Lb. casei 279, Lb. casei LAFTI L26 or Lb. acidophilus LAFTI L10 had significantly higher (P < 0.05) ACE-inhibitory activity than those without any probiotic adjunct after 24 weeks at 4 and 8 degrees C. The IC50 of cheeses ripened at 4 degrees C was not significantly different (P > 0.05) to that ripened at 8 degrees C. The lowest value of the IC50 (0.13 mg mL-1) and therefore the highest ACE-inhibitory activity corresponded to the cheese with the addition of Lb. acidophilus LAFTI L10. Several ACE-inhibitory peptides were identified as k-CN (f 96e102), as1-CN (f 1e9), as1-CN (f 1e7), as1-CN (f 1e6), as1-CN (f 24e32) and b-CN (f 193e209). Most of the ACE-inhibitory peptides accumulated at the early stage of ripening, and as proteolysis proceeded, some of the peptides were hydrolyzed into smaller peptides