Study on the Purification and Reusability of Burnt Cooking Oil and Assessment of Its Physicochemical and Safety Parameters

Aims: The aim of the study was to investigate the reusability of edible oils and to find which temperature the refined oils could be used for cooking purposes. Study Design:  The study followed a completely randomized design (CRD). Place and Duration of Study: The study was conducted at the Department of Agro Product Processing Technology and its corresponding laboratory on Jashore University of Science and Technology, Jashore, Bangladesh. The study took three consecutive months to complete the study. Methodology: The study adopted several methods to refine the burnt cooking oils and analyze their physicochemical as well as cooking qualities. At first, the heat was applied to commercially purchased palm, soybean, and rice bran oil. Produced burnt oil was refined using a base and hexane mixture. After that, these refined oils were repeatedly heated for 15, 30 and 60 minutes and physicochemical quality like peroxide value (PV), saponification number (SN), acid value (AV), etc were analyzed for each oil sample at each time interval. Furthermore, cooking quality of the refined oils was determined by frying sausages using each oil and the flavor, color, texture and overall acceptability were determined using hedonic scale. Results: The study found that the refining rate of each oil was at the peak when the base -to-hexane ratio was 9:1. An increasing trend was observed in the case of the peroxide value of the refined oils during repeated heating. This trend was most predominant in case of palm oil. In palm oil sample, PV of palm oil increased from 4.950±0.6 to 14.432±0.86 meqo2/kg oil at the third time of heating. The other two sample oils also crossed the standard PV of the respective oil at the third time of heating. It means all the refined oil can be used for a maximum of three times. Acid value of the oils also showed the same trend of increasing with an increase in temperature. In the case of SN, palm oil showed a higher degree of saturation with increased heating time among the refined oils. The flavor, color, texture, and overall acceptability of the sausages fried in these three showed significant differences at p<0.05. This is an indicator that burnt cooking oil that was refined can be reused in cooking.    Conclusion: Due to the increasing price of edible oils and limited resources, they can be refined from their burnt stage and reused for cooking. Therefore, refining can be a good method to solving edible oil scarcity.