Oxidative changes of vegetable oils during microwave heating

The oxidative stabilities of pork lard, sunflower, zero-erucic rapeseed, peanut and high-oleic peanut oils were tested under microwave heating conditions. Vegetable oils and lard were heated in a microwave oven for up to 40 min between 25°C and 200°C. The peroxide value, the contents of conjugated dienoic and trienoic acids, and polymers were used as markers of lipid degradation. Sunflower oil was found the least stable oil because of a high polyenoic acid content and a low content of γ-tocopherol. Rapeseed oil was more stable because of a lower polyenoic acid content and a high γ-tocopherol level. Conventional peanut oil was relatively stable, but substantially less stable than high-oleic peanut oil. Pork lard and high-oleic peanut oil formed only low levels of polymers due to a low polyenoic acid content.