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The active substance of turmeric rhizome (curcumin) was extracted and identified with TLC and NMR. To evaluate the antioxidant efficiency of different concentrations of curcumin (120, 160 and 200 ppm) compared with tert-butylhydroquinone (TBHQ) (120 ppm) and α-tocopherol (200 ppm) at two different temperatures (25°C and 55°C) under dark and light conditions during 90 days, the soybean oil with no added antioxidant was used as a food model, and its fatty acids profile was determined by GC. Results indicated that increasing concentration of curcumin leads to significantly decreased oxidation rates. The soybean oil containing curcumin at 25°C in darkness with the lowest rate of increased peroxide value indicated the same antioxidant activity with α-tocopherol and TBHQ. Moreover, the results of acid value and iodine value indicated that samples with curcumin were more effective in preventing oxidation at both temperatures compared with control. However, light did not have any significant effect.

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Background: Annatto dye is used extensively in food industry that has antibacterial and antioxidant properties. Objectives: Aim of this paper was comparison of the antibacterial and antioxidant properties of annatto dye was extracted by conventional and ultrasound-assisted extraction (UAE) methods. Materials and Methods:In this experimental study minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of annatto dye against the bacteria were determined by agar dilution method. Antioxidant activity of annatto dye was evaluated by DPPH method. Results: Gram-positive bacteria show more sensitivity to annatto dye than Gram-negative bacteria. Annatto dye extracted by UAE has more antibacterial and antioxidant activity compared to conventional method. Bacillus subtilis and Escherichia coli have the highest and the lowest sensitivity to annatto dye, respectively. Conclusions: Annatto dye extracted by UAE showed a bactericidal effect against Salmonella enteritidis, however the dye extracted by conventional method the opposite is true.

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