Effect of heating at frying temperature on the quality characteristics of regular and high-oleic acid sunflower oils

Background.Understanding of oil deterioration during heating/frying process is important as oils are nor- mally kept hot at commercial food outlets during intermittent frying cycles. An increased level of consumer awareness toward fat composition and its impact on human health could have an effect on selection of fats in the food industry. The rate of quality deterioration during heating depends on fatty acid composition and also the content and composition of minor components. Therefore, the use of more stable frying oils would be desirable. The present study compares the heat stability at frying temperature of regular sunflower oil (RSFO) with that of high-oleic acid sunflower oil (HSFO). Material and methods. Heating test was carried out at 185 ±5°C for the samples RSFO and HSFO using electric fryer for 8 h/day for 3 consecutive days. The samples were collected every 4 h. The changes in phys- icochemical properties of the samples were monitored by analytical and instrumental methods. Results.In this study, refractive index, free fatty acid content, peroxide value, p-anisidine value, TOTOXvalue and polar compounds of the oils all increased, whereas C /C ratio decreased as heating progressed.The percentage of linoleic acid tended to decrease, whereas the percentages of palmitic, stearic and oleic ac-ids increased. The sample HSFO exhibited better heating performance compared to RSFO. However, a higher amount of free fatty acids was found in HSFO compared to RSFO at the end of heating trial. Moreover, heat- ing process decreased the total tocopherol content and higher reduction was detected in RSFO. Conclusion.In conclusion, the heating caused the formation of comparatively lower amounts of some deg- radative products in HSFO compared to RSFO indicating a lower extent of quality deterioration of HSFO.