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Cholesterol oxidation in lard as affected by CLA during heating – A kinetic approach



The objectives of this study were to determine the effect of two CLAs , 9-cis, 11-trans CLA and 10-trans, 12-cis on cholesterol degradation and cholesterol oxidation products (COPs) formation in lard during heating for varied length of time. No CLAs and approximately 1770.1 µg/mL of cholesterol were detected in lard. Additionally, there was no significant change in the level of cholesterol and COPs in lard during heating at 100°C over a period of 240 min. But, at 150 or 200°C, the degradation of cholesterol was prominent with substantial amount of COPs being formed. Formation profiles of 7-OOH, 7-OH, and 7-keto at 150°C as well as 5,6-epoxides at both 150 and 200°C were fitted by a first-order equation, while a pseudo-second-order model described the kinetic pathway of 7-OH and 7-keto formation at 200°C. The formation of 7-OOH at 200°C were fitted as multiple first-order formation and first-order degradation curves as its level reached a peak at 60 min and declined to zero. Incorporation of 100 µg/mL CLA showed antioxidant activity, whereas a prooxidant activity was observed for CLA at 500 µg/mL. The outcome of this study demonstrated the potential of CLA to be an antioxidant in oil system.