Secondary structures and their effects on antioxidant capacity of antioxidant peptides in yogurt

The pH, thermal, urea, and trifluoroethanol treatments were used to denature yogurt antioxidant peptides, and their antioxidant capacities and secondary structures were analysed. Results showed that yogurt peptides treated at pH 6.0 or above 50 degrees C exhibited higher antioxidant activity than the control, whereas trifluoroethanol treatment resulted in a reduction and urea treatment held invariability. Peptide secondary configuration analyses revealed that these treated peptides significantly decreased their -helical conformation but enhanced the -sheet presence as well as an obvious alteration on -turn and random coil structures. These peptide conformation alterations contributed to their antioxidant property increase.