Abstract
The antioxidant activity of catechin (CT), (-)-epigallocatechin gallate (EGCG), gallic acid (GA), butylated hydroxytoluene (BHT), tert-butylhydroquinone (TBHQ) and mixed tocopherol (M-Toc) added in oils containing basic (sodium, ammonuim, calcium and magnesium hydroxides) and acidic materials (acetic, citric and tartaric acids) was assessed by C.D.M. (Conductometric Determination Method) so as to determine the rancid point (induction time) and the oven test. C.D.M. in all cases was conducted with a E 679 Rancimat (Metrohm Co. Ltd., ). The oils (3g) were examined at 120°C with air passing through (20L/h) them. In the oven test, the oils (20g) were oxidized in a beaker (4×4.4cm) at 60°C, and peroxide was determined by the JOGS official method 2.4.12-71.
The order of antioxidative activity of the antioxidants was TBHQ>GA>EGCG>CT>BHT>M-Toc. TBHQ had the strongest antioxidant effects for oil deterioration. TBHQ and EGCG had no effect on oils containing sodium hydroxide. The antioxidative activity of BHT and M-Toc in oils containing sodium hydroxide was much greater than in those containing only BHT and M-Toc. The addition of acetic acid appeared to accelerate the oxidative deterioration of oil. This effect was prevented by TBHQ, EGCG, BHT and M-Toc.
