Hydrogen peroxide and ferulic acid-mediated oxidative cross-linking of casein catalyzed by horseradish peroxidase and the impacts on emulsifying property and microstructure of acidified gel

Abstract

Horseradish peroxidase (HRP, EC 1.11.1.7) was used in this study to catalyze oxidative cross-linking of casein in the presence of hydrogen peroxide and cross-linker ferulic acid. Cross-linking of casein was demonstrated by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and ultraviolet absorbance analysis. Oxidative cross-linked casein mediated by hydrogen peroxide and ferulic acid was prepared at casein concentration of 5% (w/ w), HRP addition of 3 mkat·g-1 proteins, ferulic acid addition of 6 mmol·l-1, 3% (w/w) H2O2 addition of 1 ml, reaction temperature 37°C and reaction time 3 h. Analysis results showed that the emulsifying activity index and emulsifying stability index of cross-linked casein prepared were enhanced compared to that of untreated casein totally. Microstructure of chemical acid-induced gel of cross-linked casein was observed under scanning electron microscopy and appeared to be more compact and uniform than that of casein. Hydrogen peroxide and ferulic acid-mediated oxidative cross-linking of casein catalyzed by horseradish peroxidase might have a beneficial to the emulsifying property or gelation of casein.