Tocopherol retention in physically refined rapeseed oil as a function of deodorization temperature

The effect of deodorization temperature (between 220 and 270 °C) on tocopherol retention in physically refined rapeseed oil during deodorization in a plant-scale semi-continuous tray-type deodorizer was investigated. Among the three tocopherol homologues detected in the samples of rapeseed oils under study, the α- and γ-tocopherol homologues, with the latter predominating, constituted the most abundant part of total tocopherols, accompanied by a small amount of δ-tocopherol. The retention values calculated for both total and individual tocopherols decreased linearly with increasing deodorization temperature. The retention of total tocopherols decreased considerably from 91.5% at 220 °C to 54.7% at 270 °C, approaching a value of about 80% in the main area of concern between 230 and 240 °C. The retention values of individual tocopherols as well as the slopes resulting from the equations relating these retentions to deodorization temperature were observed to decrease in the same order as their molecular weights. Since the retention of α-tocopherol is slightly higher than that of γ-tocopherol, the average proportion of α-tocopherol during deodorization slightly increases at the expense of γ-tocopherol.