Production of Food and Cooking

Cooking of porridges of rolled oats and rye meal implies only minor effects on their tocopherol and tocotrienol contents. About 4-9% of tocopherols and 0-5% of tocotrienols were lost in rolled oats and rye meal porridges, when the cereals were of good quality (Piironen et al., 1987). Malting had no effects on tocopherol and tocotrienol concentrations of barley and brewers coproduct of barley rich in these vitamers (Peterson, 1994). 

In deep-fat frying, the temperature reaches 170°C, and tocopherols are unstable. The order of stability of different tocopherols remains similar to that at lower temperatures, i.e., a y 8 (Gordon and Kourimska, 1995 Lampi and Kamal-Eldin, 1998). However, an opposite order of stability has also been found. During deep-fat frying, the relative stabilities of natural tocopherols and tocotrienols in soybean oil were a-tocopherol 8-tocopherol P-tocopherol y-tocopherol, in corn oil were a-tocopherol y-tocopherol 8-tocopherol y-tocotrienol, and in palm oil were a-tocopherol S-tocotrienol a-tocotrienol y-tocotrienol, respectively (Simonne and Eitenmiller, 1998). The authors assumed that tocotrienols were less stable than tocopherols, because they acted more effectively as antioxidants. 

Tocopherol losses during microwave cooking are mainly caused by the effect of high temperature and not by microwaves as such. When sunflower oil was subjected to microwaves discontinuously for 120 min at two constant temperatures namely, 170°C and 40°C, tocopherol losses were 72% and 21%, respectively (Albi et al., 1997). During continuous microwave cooking of soybean oil, the temperature increased and reached 170°C after 8 min and 210°C after 25 min This caused greater losses of tocopherols, i.e., 5% and 10-30% after 8 and 25 min of heating, 

Functional Foods BiocFiemical and Processing Aspects, Volume 2 

---