Effect of heating and Re-heating on physico-chemical properties of rice bran oil and soybean oil

Abstract

This study investigates the thermal stability and suitability of rice bran oil (RBO) and soybean oil (SBO) during deep-oil frying of French fries, with a specific focus on the 6th time oil usage. The purpose is to determine the impact of repeated heating cycles on the physical, chemical, and fatty acid composition of these oils. Results reveal that RBO is more stable than SBO. Both oils maintain peroxide values below 10 meqO2/kg in the initial four heating cycles, with acceptable acid values (<0.6 mg KOH/100 g) up to the 5th cycle for RBO and the 3rd cycle for SBO. Saponification values exceed recommended levels initially but stabilize subsequently. Free fatty acids (FFA) and total polar materials (TPM) exhibit remarkable stability after repeated heating, showcasing the resilience of both oils. Fatty acid composition analysis demonstrates RBO's enhanced stability, with an increase in total saturated fatty acids and a concurrent decrease in unsaturated fatty acids. This highlights RBO's superior resistance to degradation compared to the more vulnerable SBO, rendering it more suitable for extended usage. In conclusion, the study provides valuable insights into the physical and chemical changes in these oils during prolonged deep-frying, underscoring RBO's greater thermal stability. This research offers a novel perspective on the suitability of cooking oils for enduring high-temperature culinary applications, emphasizing the importance of RBO for extended usage in deep-frying processes.