Effects of alpha-tocopherol on oxidative stability and phytosterol oxidation during heating in some regular and high-oleic vegetable oils.

摘要

Oxidative stability of high-oleic rapeseed oil, palm olein, refined olive oil, low erucic acid rapeseed oil and sunflower oil was determined. Oxidative stability, determined by the Rancimat method, decreased in the order: palm olein > high-oleic rapeseed oil > refined olive oil > low erucic acid rapeseed oil > sunflower oil. Addition of alpha-tocopherol at high levels (<=0.2%) increased the oxidative stability of refined olive oil, whereas the opposite effect was generally observed in the other oil samples. In the second part of the study, high-oleic rapeseed oil, palm olein, refined olive oil and refined olive oil containing 0.2% alpha-tocopherol were heated for 3, 6, 9 and 12 h at 180 degrees C. Peroxide and p-anisidine values generally increased over time in the samples, including olive oil containing 0.2% alpha-tocopherol. High-oleic rapeseed oil contained the highest amounts of total sterols and total phytosterol oxidation products (POPs), but during heating total POPs contents increased moderately (by approx. 10%), in contrast to the 3x increase after 12 h of heating in palm olein and refined olive oil. Very high levels of 6-hydroxy derivatives of brassicastanol, campestanol and sitostanol and of 7-ketobrassicasterol were observed in high-oleic rapeseed oil samples. Addition of 0.2% alpha-tocopherol during heating significantly decreased POPs formation in refined olive oil (P < 0.05).