Effect of cross-linking of interfacial sodium caseinate by natural processing on the oxidative stability of oil-in-water (o/w) emulsions.

This study investigated how enzymatic cross-linking of interfacial sodium caseinate and emulsification, via high-pressure homogenization, influenced the intrinsic oxidative stability of 4% (w/v) menhaden oil-in-water emulsions stabilized by 1% (w/v) caseinate at pH 7. Oil oxidation was monitored by the ferric thiocyanate perioxide value assay. Higher homogenization pressure resulted in improved intrinsic emulsion oxidative stability, which is attributed to increased interfacial cross-linking as indicated by higher weighted average sedimentation coefficients of interfacial protein species (from 11.2 S for 0 kpsi/0.1 MPa to 18 S for 20 kpsi/137.9 MPa). Moderate dosage of transglutaminase at 0.5-1.0 U/mL emulsion enhanced intrinsic emulsion oxidative stability further, despite a contradictory reduction in the antioxidant property of cross-linked caseinate as tested by the 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay. This implied the prominent role of cross-linked interfacial caseinate as a physical barrier for oxygen transfer, hence its efficacy in retarding oil oxidation.