EFFECTS OF CHEMICAL INTERESTERIFICATION ON THE PHYSICOCHEMICAL PROPERTIES OF PALM STEARIN AND RICE BRAN OIL BLENDS

Palm stearin (PS) and rice bran oil (RBO) were blended in the mass ratio of 100: 0, 70: 30, 50: 50, 30: 70 and 0: 100. The oil blends were subjected to chemical interesterification (CIE) catalyzed by sodium methoxide (0.2% w/w). The following analysis were carried out before and after CIE: triacylglycerol (TAG) composition, slip melting point (SMP), solid fat content (SFC), microstructure, polymorphism and hardness index (HI). After chemical interesterification, there were decrease and increase in the amount of several TAG. Changes in TAG composition caused changes in the physical properties of the blends. Both SMP and SFC of all blends decreased significantly (p<0.05) after interesterification except for RBO. Chemical interesterification also reduced the eutectic interaction at 5 degrees C. However, for hardness index, only blends with 50% and 100% PS decreased significantly (p<0.05) from 33.197 to 26.097 and 5.397 to 3.720, respectively. The crystals of the blends became smaller and reduced in number after interesterification. Interesterification promoted the formation of more beta' crystals than beta in all blends. The 30: 70 PSRBO blend was the most suitable for margarine production as it melted close to body temperature.