Effect of heat pretreatment on the yield and composition of oil extracted from corn fiber

Previously, hexane extraction of corn fiber was reported to produce a uniqu e and potentially valuable oil that contained high levels of several phytos terols (which have been noted for their cholesterol-lowering properties). C urrent studies revealed that heat treatment (over the range of 100-175 degr ees C) of corn fiber in either a convection oven or a vacuum oven caused on ly a modest reduction in the levels of the phytosterol components. However, these same heat pretreatments caused a considerable increase (up to 10-fol d) in the levels (increasing from 0.34 wt % to a maximum of 3.64 wt % gamma -tocopherol in the oil) and yields (increasing from 5.4 mg of gamma-tocophe rol/100 g of corn fiber to a maximum of 52.1 mg of gamma-tocopherol/100 g o f corn fiber) of gamma-tocopherol in corn fiber oil. The main differences b etween the convection oven and vacuum oven pretreatments were associated wi th the disappearance of free fatty acids and free phytosterols at the highe r temperature pretreatments in the vacuum oven, probably due to the lower b oiling points of these lipids. Microwave pretreatment was also effective bu t caused a much smaller increase in the levels of gamma-tocopherol.