Abstract:
Feasibility of using natural antioxidant in vegetable cooking oil was studied by the determination of the antioxidant activity of oil extracted from fermented soybean in soybean oil. Peroxide value (P.V.) was used as a relative measure of the degree of oxidation, with higher P.V. indicating greater degrees of oxidation. The oxidative stability of seven samples of soybean oil combined with different additives were compared with refined soybean oil. One of the samples contained 0.02% BHT (a synthetic antioxidant) (S). Two of the samples were refined soybean oil which contained 5% (B+T5) and 10% (B+T10) crude fermented soybean oil, respectively. The other two samples were refined soybean oil which contained 0.5% (B+RT0.5) and 1.0% (B+RT1) refined fermented soybean oil, respectively. The last two samples were prepared at first by mixing crude soybean oil with 5% [(CB+T5)R] and 10% [(CB+Tl0)R] crude fermented soybean oil, then both were refined. The experiment was conducted under three different conditions. The first condition, the samples were stored at 50 ͦC for 21 days while the other were exposed to ultraviolet light for 1 hour before being stored at room temperature for 21 days. In last condition, the samples were used for deep frying to evaluate the carry through property of the additives. Comparison of P.V. of the samples showed that (CB+T5)R was significantly more stable (p<0.05) at room temperature (exposing ultraviolet light for 1 hour before storing) or elevated temperature (50 ͦC) than any other samples. The results of (CB+T5 )R used for deep frying turned out the same as using the refined soybean oil, while P.V. of the oil extracted from khaw kriab kung (object used for deep frying in this experiment) fried in (CB+T5)R was significantly (P<0.05) lower than that of fried in refined soybean oil.