Study on the solubilizing,gelling and emulsifying properties of whey protein isolate modified by a free radical-generating system

The objective of the present study was to investigate the changes in solubility,gel-forming ability and emulsifying capability of whey protein isolate(WPI)after exposures to a hydroxyl radical-generating system(HRGS)in different concentrations of H2O2(1~20mmol/L)or FeCl3(0.1~2mmol/L)for 1,3,5h.The results showed that oxidation reduced solubility(up to 35%)and gel strength(up to 85%)under the oxidative conditions investigated.The deleterious effect was greater by FeCl3 than by H2O2.However,while extensive protein oxidation impaired emulsification of WPI,mild oxidation with low concentrations of the oxidants and short oxidizing times favored emulsion formation and enhanced the emulsion stability in the WPI-oil system.The gelation and emulsifying ability of WPI were closely related to protein solubility but the gelation was more sensitive to the solubility change.The overall effect of HRGS on the functionality of WPI appeared to depend on the extent of physicochemical modification of the proteins.