| People have focused on the natural antioxidants because of the advantage of security. However, the antioxidant effect of natural antioxidants applied into rice bran oil has seldom reported. Lipid-soluble rosemary extract, lycopene, VE and β-carotene were selected as the antioxidant applied in rice bran oil. The synergistic antioxidative activity of lipid-soluble rosemary with L-ascorbyl palmitate applied in rice bran oil was studied, and the TBHQ was taken as the control. The role of associative antioxidant played in deep frying oil was also researched. The results showed as follows:1. Lipid-soluble rosemary extract had excellent antioxidant effect on rice bran oil. The induction period of rice bran oil could be respectively prolonged1.37times,2.62times and2.93times when the oil was added0.01%,0.03%,0.05%and0.07%(m/m) of lipid-soluble rosemary extract. Temperature and sunlight had few effects on the antioxidant activity of lipid-soluble rosemary extract when the addition amount was0.05%, but2mg/kgFe3+and2mg/kgAl3+could significantly reduced the antioxidant activity. The antioxidant effect of lycopene in rice bran oil was not obvious when the dose range was0-0.03%. VE showed a slight antioxidant effect when the dose was0.01%, while others addition would contribute to the oxidation of bran oil mildly. The antioxidant effect of β-carotene was similar to VE, β-carotene slightly facilitated oxidation of rice bran oil when the addition was0.005%, the antioxidant effect of others addition was fewer.2. The best synergistic antioxidative activity of lipid-soluble rosemary with L-ascorbyl palmitate was that the ratio of lipid-soluble rosemary to L-ascorbyl palmitate was4to1. Lipid-soluble rosemary was the master antioxidant. L-ascorbyl palmitate as synergistic antioxidative had an optimum level, the antioxidantive effect was lower when L-ascorbyl palmitate supplement was higher or lower than the optimum level. The associative antioxidant had excellent antioxidant effects on rice bran oil when the dose range was0.01-0.05%.The addition of0.02%associative antioxidant had the best efficiency, the induction period could be prolonged3.15times, and could effectively inhibit the change in fatty acid content of rice bran oil such as SFA, MUFA and linoleic acid. However, the antioxidant effect was inferior to0.02%TBHQ.3. The changes of the peroxide value in rice bran oil had no regularity. The maximum peroxide value was40.63meq/kg and reached at10h. The peroxide value of rice bran oil decreased with the frying temperature increased. The acid value of rice bran oil generally increased with the increasing of frying time and frying temperature.The polar compound in rice bran oil increased with the increasing of frying time, the temperature increased could improve the polar compound content in the frying oil. Both0.02%associative antioxidant and0.02%TBHQ could effectively inhabit the changes of peroxide value, acid value and polar compound,0.02%associative antioxidant effect was better than that of0.02%TBHQ.4. The relative content of total saturated fatty acid in rice bran oil increased with the increasing of frying time. At begin period of deep frying, the relative content of total monounsaturated fatty acid significantly increased. However, the relative content began to reduce after2h, the relative content decreased by12.65%at12h.The changes in the relative content of linoleic acid in rice bran oil had no regularity, the relative content had reduced9.13%after12h. The relative content of total saturated fatty acid in rice bran oil increased with the increasing of frying temperature, frying temperature was inversely proportion to the content of unsaturated fatty acids. Both0.02%associative antioxidant and0.02%TBHQ could effectively inhabit the change in fatty acid content of rice bran oil, such as SFA, MUFA and linoleic acid, the inhibitory effect of two was similar. |
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