Rheological and Physicochemical Modification of trans-Free Blends of Palm Stearin and Soybean Oil by Chemical Interesterification

In this study, binary blends of palm stearin and soybean oil were interesterified using sodium methoxide. The changes in free fatty acids (FFA), slip melting point (SMP), solid fat content (SFC), plastic range, induction period of oxidation at 120 degrees C (IP120) and rheological properties of fat blends, before and after interesterification, were investigated. All blends were trans-free and contained high essential fatty acids content. Interesterification modified the melting properties of fat blends by reducing SMP and SFC. FFA increased and IP120 decreased after interesterification. Strain sweep, frequency sweep and temperature sweep tests were used to evaluate the rheology of fats. Briefly, the 10:90 and 30:70 (palm stearin:soybean oil) interesterified blends displayed increased storage (G) and loss (G) moduli, as compared with the initial blends. However, G and G moduli of interesterified 50:50 blend were lower than those of initial blends. The elastic character of interesterified 10:90, 30:70 and 50:50 blends was predominant up to 28.8, 37.9, and 41.8 degrees C, respectively. The interesterified blends of palm stearin and soybean oil showed desirable characteristics suited for production of trans-free soft tub, stick and Baker's margarine, all-purpose shortening and Iranian vanaspati. Practical ApplicationsIntake of high amounts of trans fatty acid (TFA) has been correlated with increased risk of heart diseases. In this context, chemical interesterification is an important technological option for production of trans-free fats with different food applications. The results obtained here provide information about the scientific aspects of the effect of interesterification on rheological and physicochemical properties of palm stearin and soybean oil blends. Practically, this study can find its application in development of formulations for production of trans-free fat products such as liquid, soft tub, stick and baker's margarine, all-purpose shortenings and Iranian vanaspati.