Antioxidative activity and structural stability of microencapsulated gamma-oryzanol in heat-treated lards

Abstract

Using the central composite design, we have designed the experimental platform for optimizing gamma-oryzanol (GO) microencapsulation. Response surface methodology (RSM) was applied to explore maximal microencapsulation yield (MY) using three independent variables; the ratio of core materials to coating materials (X-1), temperature of dispersion fluid (X-2), and emulsifier concentration (X-3). As a result of least-square regression (RSREG) analysis, the regression model equation for the MY (%) to the change of independent variables could be predicted as follows; YM = 102.71 - 2.88X(1)(2) - 2.97X(3)(2). Applying this model equation to the surface plot and canonical analysis, the optimal conditions for the GO microencapsulation were determined to be 4.8:5.2 (X-1), 24.99 (X-2) and 0.38% (X-3). The resulting MY, with statistically optimized parameters, was 95.7%. The thiobarbituric acid-reactive substances (TBARs) values of heated lard were determined to evaluate the effect of microencapsulation on the stability against heat-induced lipid oxidation. The MGO (micro-encapsulated gamma-oryzanol)-treated lard displayed significantly greater oxidative stability than did the GO-treated lard up to a 10-day heating period. During the heating process, a substantially larger amount of GO remained in the MGO-treated lard as well. Apparently, microencapsulation could be used as a good potential technique to protect GO from the heat-induced loss of its antioxidant effect.