The changes in tocopherol content of oil used for deep-fat frying of p
otatoes have been studied. It has been found that alpha-tocopherol is
lost much faster than beta-, gamma- or delta tocopherol, with a reduct
ion of 50% alpha-tocopherol after 4-5 frying operations compared with
values of about 7 and 7-8 frying operations for beta- and gamma-tocoph
erol, respectively, in the absence of added antioxidants. However, the
presence of a rosemary extract or ascorbyl palmitate in the frying oi
l caused a marked reduction in the rate of loss of the tocopherols.