The efficiency of tocopherol (Toc) in bringing about the oxidative deterioration of emulsified fatty foods was compared with that of other antioxidants, and the synergistic effects of the antioxidants and several synergists with Toc were investigated. Margarine, as a model of an emulsified fatty food, was prepared from lard with vitamin A and β-carotene. Its stability toward oxidation was evaluated on the basis of changes in POV, and content of vitamin A and β-carotene during storage at 25°C.
1) Isopropyl citrate had little effect on the oxidative deterioration of margarine. But, other antioxidants did so to a much greater degree than Toc in the order of propyl gallate (PG) _??_t-butylhydroquinone (TBHQ) >dibutyl hydroxytoluene.
2) The addition of PG or TBHQ along with a mixture of d-Tocs (m-Toc) was found to provide the most protection of margarine against oxidative deterioration. However, the addition of PG or TBHQ to margarine resulted in brownish discoloration during storage.
3) Citric acid and L-ascorbyl stearate (AS) enhanced synergistically the effects of m-Toc on the oxidative deterioration of margarine. The effects of AS along with m-Toc, in particular, were almost the equivalent of these of PG. However, such effects were not observed in case of L-ascorbic acid and erythorbic acid, on being added to aqueous phase of margarine.
4) PG and TBHQ disappeared within a month durig storage. Thus, some of their oxidative products appear to preserve their antioxidant activity on margarine.
