Relationship between tocopherols depletion and polymerised triacylglycerols formation during heating of vegetable oils

Abstract

Alpha tocopherol and total tocopherols depletion in relation to polymerised triacylglycerols formation were studied during the heating of nine vegetable oils (olive, palm, peanut, sunflower, rapeseed, soybean, grapeseed, maize and rice) at oil temperature 180°C (as a typical temperature during frying practise). It was observed that the rate of tocopherols depletion (expressed as the function of polymerised triacylglycerols content) decreased with the increasing degree of unsaturation and total antioxidant capacity of the tested oils (P < 0.05). Consequently, no tocopherols were present in olive, peanut and palm oil at their half lifespan (i.e., at 6% of polymerised triacylglycerols), whereas tocopherols in maize, sunflower, grapeseed, rice and, particularly, soybean oil were present even at the end of their lifespan, (i.e., at 12% polymerised triacylglycerols). These findings have not been published yet, or only little published.

Keywords

• frying
• lipid oxidation
• plant oils
• vitamin e