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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