Abstract: The aim of this study was to investigate the emulsifying properties and antioxidant stability of laccase (LAC)- mediated cross-linked products of rice protein (RP) and ferulic acid (FA). RP emulsion showed marked phase separation at pH 5 and 3, while only partial aggregation was observed at pH 7 and 9, suggesting even lower stability in the acidic pH range than in the basic pH range. The particle size and creaming index of cross-linked RP/FA/LAC emulsion were less than those of RP emulsion at pH 5, 7 and 9, but higher at pH 3, suggesting that emulsion stability of crossed RP/FA/LAC emulsion was improved at pH 5, 7 and 9, but was unstable at pH 3. Moreover, the contents of hydroperoxide (11.12 mmol/kg), TBARS (0.73 mmol/kg) and hexanal (0.986 mg/L) in RP emulsion were significantly higher than those in cross-linked RP/FA/LAC emulsion (3.59 mmol/kg, 0.23 mmol/kg and 0.191 mg/L, respectively), suggesting that RP/FA/LAC cross-linking had better oxidative stability at the emulsion interface. Enzymatic cross-linking between RP and FA will have potential application in emulsion system for food processing.

Key words: rice protein, ferulic acid, laccase, cross-linking, emulsifying property, antioxidant stability, oil oxidation