Angiotensin converting enzyme-inhibitory activity in Cheddar cheeses made with the addition of probiotic Lactobacillus casei sp.

The aim of the study was to examine the release of ACE-inhibitory peptides in Cheddar cheeses made with starter lactococci and Lactobacillus casei 279 or Lb. casei LAFTI(R) L26 during ripening and to isolate, purify and identify such peptides. Addition of probiotic organisms increased the ACE-inhibitory activity of the cheeses during ripening at 4 degrees C possibly due to the increased proteolysis. The IC50 (concentrations of ACE needed to inhibit 50% of ACE activity) was the lowest after 24 weeks of ripening in the probiotic cheeses (0.23-0.25 mg.mL(-1)) compared to 36 weeks for cheeses without any probiotic (0.28 mg.mL(-1)). Water-soluble extracts of each cheese were subjected to several stages of chromatography fractionation. Inhibitory activity found in the crude fractions ranged from 0.1 to 2.0 mg.mL(-1). The fraction with the highest activity was purified using a second stage chromatography. Various ACE-inhibitory peptides corresponding to the alpha(s1)-casein N-terminal peptides [(f 1-6), (f 1-7), (f 1-9), (f 24-32) and (f 102-110)] and beta-casein N-terminal peptides [(f 47-52) and (f 193-209)] were found. Our results suggested that ACE inhibition in Cheddar cheeses was dependent on proteolysis to a certain extent. Probiotic organisms used in this study can be added successfully in Cheddar cheeses in order to provide health benefits while simultaneously producing bioactive peptides for additional health attributes.