Fabrication and characterization of whey protein isolates- lotus seedpod proanthocyanin conjugate: Its potential application in oxidizable emulsions

Emulsified omega-3 polyunsaturated fatty acid have expanding application in different food matrix with improved water solubility while still prone to oxidation. Lotus seedpod proanthocyanidin (LSPC) was grafted to whey protein isolate (WPI) to create nature-derived antioxidant emulsifiers. 1HNMR, SDS-PAGE and multiple spectrometry showed that the structure of protein was changed after grafting. DPPH and FRAP measurements showed that WPI-LSPC conjugate (90.53 +/- 1.48% of DPPH scavenging, 691.85 +/- 4.54 mu g/mL for FRAP assay) possessed a much better antioxidant ability than WPI (17.06 +/- 3.34% of DPPH scavenging, 10.43 +/- 0.26 mu g/mL for FRAP assay). Ultrasonic emulsification and DSC experiments showed that WPI-LSPC conjugate were more effective at forming and stabilizing the flaxseed oil emulsions than pure WPI, with higher thermostability. Likewise, low levels of primary and secondary oxidation products were formed for the conjugate than the pure protein in O/W systems after storage, again suggesting WPI-LSPC could be used as fine antioxidant emulsifiers in oxidizing delivery systems.