Evaluation of oxidative stability and quality parameters of sunflower oil fortified with varied levels of retinyl palmitate under diverse storage conditions

Fortificated vegetable oils with forms of vitamin A is highly effective in reducing the prevalence of vitamin A deficiency worldwide. Vitamin A, an antioxidant, also protects the oil from oxidation and can enhance oil's quality. Therefore,this study aims to evaluate the effect of fortifited sunflower oil with varying amounts of retinyl palmitate on the oil's oxidative stability and quality parameters. In this context, five different groups with varying levels of retinyl palmitate (control, 15 mcg/g, 30 mcg/g, 60 mcg/g, 90 mcg/g) were created. Sunflower oil were stored at 26-32 oC under varying conditions (light/dark; transparent/brown glass bottle) for 6 months. Rancimat analysis was performed on sunflower oils before storage, and retinyl palmitate level, peroxide value, conjugated diene, conjugated triene, free acidity and photometric color analyzes were performed on the stored samples once a month. The results showed no statistically significant difference was found between the groups in terms of Rancimat (p>0,05) (lowest 5,83±0,14 hours, highest 6,47±0,14 hours). The peroxide and free acidity values of the sunflower oil increased over time (p<0,05). In the same months, in each retinyl palmitate group, the analysis results of sunflower oil in light and transparent bottles were generally highest; the results of sunflower oil in dark and brown bottle were generally lowest. As the amount number of retinyl palmitate in the sunflower oil increased in same months, the peroxide value and free acidity values generally decreased during storage. Retinyl palmitate levels measured in the study generally decreased during storage (p<0,05). In the same months, the retinyl palmitate levels of the sunflower oil in the light and the transparent bottle were the lowest in each group, and were generally zero at the end of the 6th month (p<0,05). The preservation of retinyl palmitate is generally optimal in dark and brown bottles. In the study, no specific increase or decrease was detected in terms of measured conjugated diene and triene values and photometric color analysis L*, a* and b* values. However, statistically significant differences were detected in terms of time, group, environment and bottle color and their interactions (p<0,05). Consequently, time, amount of retinyl palmitate (group), light/dark and transparent/brown bottle color and their interactions have significantly impact some oxidation and quality parameters of sunflower oil fortified with retinyl palmitate. Oil fortificated with retinyl palmitate should be consumed as soon as possible after production. However, exposure to light should be minimized by storing in dark and in light-proof bottles. In light of this study, further research is needed, involving a larger number of parameters are measured from sunflower oil stored under varying storage conditions for extended periods.