Effect of microwave heating of linseed oil on the formation of primary and secondary oxidation products

摘要

The purpose of the present study was to explore the influence of microwave heating for different periods on the primary and secondary oxidation, total oxidation as well as conjugation of stripped and non-stripped linseed oils. Color index of the oil samples was also evaluated to show changes of color during periodical heating. It was generally found that a significant increase in peroxide value, p-anisidine, total oxidation, conjugated diene and conjugated triene for microwave heating periods of 1,2,3,4 and 5 min. Two samples (stripped and non-stripped) of linseed oil (microwave treated) were analyzed individually in triplicate, and the results were reported as mean ±SD. Statistical significance of the differences between mean values was assessed by one-way ANOVA. It was found that stripped linseed oil (absence of antioxidants) is prone to heat effect than the non-stripped oil (with antioxidants). Generally, it is recommended that polyunsaturated oils have to be prevented from heat treatment for cooking purposes (e.g. soybean and linseed oils), since they contain linoleic and linolenic acids which are sensitive to oxidation.