Today, the use of natural antioxidants is attracting the attention of consumers. Black plum peel is the waste of plum processing and is the source of antioxidants. In this research, the effect of black plum peel extract (BPPE) (0, 400, and 800 ppm) as a natural antioxidant and storage time (0, 8, and 16 days) on the oxidative stability parameters (peroxide value, free fatty acids, thiobarbituric acid, conjugated dienes, and carbonyl value) of sunflower oil with response surface methodology (RSM) method was studied. The predominant polyunsaturated and monounsaturated fatty acid (MUFA) in sunflower oil were C18:2C (63.77%) and C18:1C (24.86%), respectively. Increasing the storage time up to 8 days caused to increase the peroxide value and thiobarbituric acid and there were reduced from 8 to 16 days (p < 0.05). Increasing the storage time increased the conjugated dienes sharply, however it was reduced very slow by increasing the BPPE (p < 0.05). Free fatty acid content and carbonyl value of the oil increased non-linearly by the storage time (p < 0.05). The best conditions for sunflower oil were 3 days and 472.73 ppm black plum peel concentration (R² = 0.71). The RSM was usable for determining the optimal concentration of BPPE for oxidative stability of sunflower oil.

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