Influence of protein oxidation of whey protein isolate on emulsifying properties and foaming properties by a free radical-generating system

The objective of the present study was to investigate the effects of protein oxidation on carbonyl content, emulsifying capability and foaming ability of whey protein isolate (WPI) after exposures to a hydroxylradical-generating system (HRGS) in different concentrations of H2O2(1～20 mmol/L)or FeCl3(0.1～2 mmol/L)for 1, 3 and 5 h. The results showed that emulsifying capability and foaming ability were significantly increased in the lower oxidative conditions. But the deleterious effect was greater in high concentration of the oxidants. We found that protein oxidation reduced emulsifying ability(up to 60%) and foaming ability(up to 20%) under the higher concentration for 5 h in FeCl3 system compared with thcontrol. And the emulsifying capability and foaming ability of WPI were closely related to carbonyl content. The overall effect of HRGS on the functionality of WPI appeared to depend on the extent of protein oxidation. So reasonable control of protein oxidation was necessary in production.