Effects of Temperature and UV Light on Degradation of α-Tocopherol in Free and Dissolved Form

Abstract

The effects of heat and UV exposure on the degradation of free α-tocopherol (oil form), α-tocopherol dissolved in methanol, and α-tocopherol dissolved in hexane were measured. Results showed that degradation of free α-tocopherol due to heat followed first order kinetics, with the samples held at 180 °C showing the greatest degradation rate. Free α-tocopherol degraded faster at high temperatures than dissolved α-tocopherol. In contrast, free α-tocopherol did not degrade when exposed to UV light for as long as 6 h, but the hexane and methanol samples degraded significantly as a matter of time. The α-tocopherol dissolved in hexane and methanol degraded by 20 and 70%, respectively over this time span. A mechanism for degradation of α-tocopherol was proposed to explain the higher degradation rate of α-tocopherol in methanol, as compared to hexane for times longer than 180 min. Knowledge of degradation kinetics of pure α-tocopherol as a result of temperature or exposure to UVA light whether in free or dissolved form is critically needed to understand how different processing parameters affect the amount of α-tocopherol during extraction, stabilization, storage or encapsulation processes. © 2009 AOCS.