The synergistic antioxidant effects of d-tocopherol (Toc) and L-ascorbyl stearate (AS) on several solid fats having different physical properties were investigated by storage tests at 30°C or 40°C. The effects were compared to those in the liquid state by AOM tests. The fats were fully hardened beef tallow mixed lard olein or stripped safflower oil, and fully hardened palm kernel oil mixed stripped safflower oil at different ratios.
1) In the storage test at 40°C, AS synergistically enhanced the antioxidant effect of a mixed tocopherols concentrate (m-Toc) on fully hardened beef tallow mixed lard olein in the solid state, as well as that in the liquid state by the AOM test. However, the synergistic effect in the solid state was more pronounced than that in the liquid state. These effects were also observed on the hardened tallow mixed stripped safflower oil.
2) Fully hardened palm kernel oil mixed stripped safflower oil had less SFC and was softer but much more stable against oxidation than fully hardened beef tallow mixed with liquid oil in the same ratio. Thus, the synergistic effect of AS with m-Toc could not be clearly detected in the solid state by the storage test at 30°C. However, the results of the AOM test indicated AS to possibly enhance antioxidant effect of m-Toc on mixed fats in the solid state as well as that in the liquid state.
3) The remnant ratios of Toc and AS following storage at 30°C or 40°C for 100 days indicated Tocs to decompose with the production of hydroperoxides in substrates, and AS to rapidly decompose in all cases.

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The synergistic antioxidant effects of tocopherol (Toc) with L-ascorbyl palmitate (AP) were investigated by the oven test at 60°C and AOM test using lard, palm oil, stripped safflower oil and fish oil.
1) In the oven test, AP showed a rather prooxidant effect but synergistically enhanced the antioxidant effect of the mixed tocopherols concentrate (m-Toc) on lard. On palm oil, AP inhibited oxidation and enhanced the effect of m-Toc. These effects became more pronounced with at increase in the amount of AP, particularly, AP more than 500 ppm, 0.02 % m-Toc was found markedly effective for inhibiting the oxidation of lard and palm oil.
2) Even the addition of AP with m-Toc essentially failed to inhibit the rapid rise in peroxide content of stripped safflower oil and fish oil rich in polyunsaturated fatty acids.
3) Such effects of AP were also observed in the AOM test, and were basically the same as those of L-ascorbyl stearate (AS).
4) In lard and palm oil, the remnant ratio of Toc after 20 d in the oven at 60°C increased with the amounts of AP and AS suggesting the protective effect of AP and AS on oxidative deterioration of Toc.

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Following the same procedure described in the previous report Yukagaku, 34, 48 (1985), the fry test was conducted so as to compare the efficiency of tocopherol (Toc) with those of other several antioxidants and investigate the synergistic effects of antioxidants along with those of Toc on the oxidation of fried foods. This test was also carried out on L-ascorbyl stearate (AS), lecithin and sucrose fatty acid esters (SE).
1) In the case of potato chips fried in a lard system containing only one of the antioxidants at a time, the time required to attain POV 30 of the chip lipid fraction and for odor to be perceivable during storage at 60°C was in the order of a mixture of d-Tocs (m-Toc) =t-butyl hydroquinone (TBHQ) >propyl gallate (PG) >dibutyl hydroxytoluene (BHT). This order agreed with the results from the transference ratio of each antioxidant to the potato chips (=proportion of antioxidant content in the chip lipid fraction to that added to the lard system).
2) Synergistic effects on the oxidation of potato chips come about as a result of TBHQ treatment or that of PG with m-Toc. However, the effects resulting from treatment with BHT with m-Toc were the equivalent of the combined effects of all the components. However, treatment with isopropyl citrate and m-Toc together was almost the same as that resulting from m-Tocalone.
3) All tested synergists were found to cause m-Toc to have greater effect on the potato chips. The time required to attain POV 30 during storage at 60°C of lecithin>AS>SE. However, addition of lecithin or SE to the fry fat resulted in browning of the potato chips and bubbling of the fat.

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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.

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Synergistic antioxidant effects of butyl caffeate (BC) and mixed tocopherol concentrate (m- Toc) on lard and palm oil were investigated by the oven test at 60°C and AOM test. The antioxidant effect of BC was also studied. BC was synthesized from caffeic acid and n-butyl alcohol, and its purity was found to be 94.5% by HPLC.
1) On lard, BC showed strong antioxidant effect, and synergistically enhanced that of m-Toc in the oven and AOM tests. These effects were more pronounced than those of caffeic acid reported previously [Yukagaku, 37, 606 (1988)].
2) On palm oil, BC showed definite antioxidant effect, while no synergistic effect with m-Toc could be detected.
3) The addition of BC prevented the oxidative deterioration of Toc in lard and palm oil.

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