Antioxidant and antibacterial activities of bioactive peptides in buffalo's yoghurt fermented with different starter cultures.

The effect of Lactobacillus acidophilus 20552 ATCC (T2) or Lactobacillus helveticus CH 5 (T3) in combination with yoghurt starter (1:1) on the antioxidant and antibacterial activities of the bioactive peptides present in buffalo's yoghurt was studied. The SDS-PAGE results indicate that all caseins were completely hydrolyzed by both strains, whereas whey protein fractions were still present. All starter cultures have the ability to produce low-molecular-weight bioactive peptides, most of which were originated from β-casein and fewer from αs1 casein. The antioxidant activity (%) of the water-soluble peptide extract from yoghurt samples increased in all samples during storage. Samples containing Lb. helveticus CH 5 showed the highest values. All yoghurt treatments displayed antibacterial activity against Escherichia coli. Control yoghurt and T3 showed higher antibacterial activity on E. coli, Staphylococcus aureus, and Bacillus cereus as compared to T2.