Acid and peroxide values are indicators of lipid oxidation of foods. Lipid oxidation is a major cause of quality deterioration of foods containing high levels of lipids and results from exposure to high temperature. But, lipid oxidation can be induced by some non-thermal treatments. Zheng et al. (2010) reported that pulsed electric field-treated peanut oil showed higher peroxide values than that of the control. Another study confirming that peanut butter treated by electron beams showed increased peroxide values was also reported (El-Rawas et al., 2012). Gao et al. (2011) reported that peroxide values of almonds increased after RF heating. But in this study, acid and peroxide values were not affected by microwave heating (Table 1). Acid and peroxide values of microwave heat-treated samples were not significantly different from those of non-treated samples. Both acid and peroxide values slightly increased after microwave heating but these differences were not significant (P > 0.05).
able 1.