Effects on functional groups and zeta potential of SAP₁<MW<3kDa treated by pulsed electric field technology

BACKGROUND SAP 1 < MW < 3kDa was chosen to investigate the improvement of antioxidant activity of peptides treated with pulsed electric field ( PEF ) technology. The effects of electric field intensity and pulse frequency on SAP 1 < MW < 3kDa were evaluated using 2,2‐diphenyl‐1‐picrylhydrazyl ( DPPH ) radical inhibition, as well as the zeta potential and functional groups. RESULTS One‐factor‐at‐a‐time tests indicated that the PEF ‐treated sample had the strongest antioxidant activity ( P < 0.05) and the lowest zeta potential value. The increase of antioxidant activity of SAP 1 < MW < 3kDa may be attributed to a loss of C = C and the amide band. Using a response surface methodology ( RSM ) experiment, it was shown that DPPH radical inhibition of SAP 1 < MW < 3kDa increased to 90.22 ± 0.90% at the optimal conditions (electric field intensity 15 kV cm −1 , pulse frequency 1600 Hz and flow velocity 2.93 mL min −1 ). Furthermore, the PEF ‐treated SAP 1 < MW < 3kDa under optimal conditions lacked the characteristic absorbance of N–H, C = C and the amide band and the zeta potential was reduced to −18.0 mV . CONCLUSION Overall, the results of the present study suggest that the improvement of antioxidant activity of SAP 1 < MW < 3kDa is a result of the contribution of the functional groups and the change in zeta potential when treated with PEF .