Comparative study of protein-lipid co-oxidation in whey protein isolate-stabilised oil-in-water emulsions prepared by different homogenisation methods

The present study mainly assessed the effects of different homogenisation methods on protein-lipid co-oxidation in whey protein isolate (WPI)-stabilised oil-in-water (O/W) emulsions during storage. The results revealed that the changes in levels of adsorbed proteins induced by different homogenisation methods could significantly affect the occurrence of protein-lipid co-oxidation. The level of oxidative stress was higher in adsorbed proteins extracted from microfluidisation homogenisation (MFH) emulsions than in those extracted from ultrasound homogenisation (UH) and high-pressure homogenisation (HPH) emulsions. This was indicated by increased levels of N′-formyl- L -kynurenine (NFK) and carbonyl, decreased fluorescence intensity and more serious aggregation. Moreover, MFH emulsions showed the highest oxidative stability, which was indicated by lower levels of primary and secondary lipid oxidation products. These findings clearly illustrate that adsorbed proteins play a crucial role in affecting protein-lipid co-oxidation in O/W emulsions, which tend to sacrifice themselves to protect lipids from oxidation under a better physical stability of O/W emulsions.