Effects of oxidative modification on thermal aggregation and gel properties of soy protein by malondialdehyde.

Malondialdehyde (MDA) was selected as a representative of lipid peroxidation products to investigate the effects of oxidative modification on thermal aggregation and gel properties of soy protein by lipid peroxidation products. Incubation of soy protein with increasing concentration of MDA resulted in gradual decrease of particle size and content of thermal aggregates during heat denaturation. Oxidative modification by MDA resulted in a decrease in water holding capacity, gel hardness, and gel strength of soy protein gel. An increase in coarseness and interstice of MDA modified protein gel network was accompanied by uneven distribution of interstice as MDA concentration increased. The results showed that degree of thermal aggregation of MDA-modified soy protein gradually decreased as MDA concentration increased, which contributed to a decrease in water holding capacity, gel hardness, and gel strength of MDA-modified soy protein gel.