M.A. Thesis:

Study of The Antioxidant Activity of Seed Extract of Securigera Securidaca .L on Soybean Oil

One method of preventing oxidation of oils using synthetic antioxidant which is very common, But like other chemical additives, their use because of potential toxicity and carcinogenicity in humans is limited. Therefore, research in connection with natural antioxidants and safe in order to replace the synthetic compounds are required to appear. In this research, we first obtained the ethanol seed extracts of Securigera Securidaca .L and the extracts were then added at various concentrations (100,200,300, and 400 ppm) to purified antioxidant-free soybean oil.The inhibition of the activity of the free radicals by the extracts and the oxidative stability of the oil at 65 degrees centigrade were studied for five days by measuring the peroxide index, the TBA index, the acid index, and the duration of induction. Finally, the activities of the extracts were compared with those of the synthetic antioxidant TBA that, at the concentration of 200ppm, had been added to the purified soybean oil.Results obtained showed that addition of 100 to 400 ppm seed extract of securigera securidaca .L to soybean oil at a given storage time increased the oxidative stability index, the quantities of polyphenolic compounds, and the inhibition of the activities of the free radicals in the oil, but decreased the peroxide index, the TBA index, and the acid index.However, at a given concentration of the extracts, the peroxide index, the TBA index, and the acid index increased by increasing the storage period of the oil from one to five days, but the duration of induction decreased. Therefore, results obtained from investigating the oxidative stability of the oil containing various concentrations of the extracts indicated that extracts at the concentration of 400 ppm, as compared with the other concentrations of extracts and the control sample, were more effective with respect to the oxidative stability of soybean oil. The reason for this was that they contained more of polyphenolic and flavonoid and tocopherol compounds, and were more effective than the BHT synthetic antioxidant added at the concentration of 200 ppm to the oil. The result seed extract of securigera securidaca .L can be useful as a source of natural antioxidant-rich and can be used.

Keywords: Securigera Securidaca .L, Soybean Oil, oxidative stability, Natural antioxidants, free radicals