OXIDATIVE STABILITY OF NATURAL AND CHEMICALLY INTERESTERIFIED COTTONSEED, PALM AND SOYBEAN OILS

Abstract

ABSTRACT The effect of interesterification on oxidative stability of cottonseed, palm and soybean oils stored under oven conditions at 45, 60 and 75C was evaluated by measuring the peroxide values (PV), anisidine values (AV) and Totox values at different time intervals. Fatty acid composition and tocopherol contents of oil samples were determined before and after interesterification. Interesterification reduced the tocopherol content of oils. The interesterified oils showed lower PV and AV than their non‐interesterified counterparts in all temperatures and time intervals. The primary and secondary oxidation reaction constants and reaction orders were investigated as a function of the reaction temperature. The interesterified oils showed lower reaction rate constants than the non‐interesterified samples. Based on PV, AV and reaction rate constants, the oxidative stability of interesterified oils were higher than their non‐interesterified counterparts. PRACTICAL APPLICATIONSThe actual shelf‐life of oils can be evaluated by following the deterioration process as a function of time and temperature. Kinetic models were predicted for further estimation of oxidation rate of natural and interesterified oils. It was observed that the reaction order dramatically decreased from first order to zero order as the reaction temperature increased from 45 to 75C. It means that the oxidation process is more concentration dependent at lower temperatures. However, according to our observations, reducing the tocopherol content during interesterification does not inversely affect the oxidative stability of cottonseed, palm and soybean oils, but interesterification reduces the nutritional value of oils. α‐Tocopherol has the highest vitamin E activity. Tocopherol supplementation of interesterified oils with equal amounts of eliminated tocopherols can be applied by related industries. Tocopherol loss is the most important and probably the only known disadvantage of chemical interesterification.