COMPARATIVE EFFECTIVENESS OF RED SANDY SOIL AND SILICA IN IMPROVING THE QUALITY OF REPEATEDLY HEATED FRYING OILS: EFFECT ON PHYSICAL PROPERTIES

This study aimed to evaluate the effectiveness of Red Sandy Soil as a natural agent for improving the physical properties of used frying oils, and to compare its effectiveness with Silica and combined treatment methods. Three different samples of used oil were examined: potato frying oil, fish frying oil, and restaurant frying oil. The potato frying oil was heated for 20 minutes daily for one month (180°C), while approximately 2 kg of fish were fried daily for 10 days. Restaurant frying oil was collected directly from a local restaurant. The physical properties of these oils were analyzed to assess the effects of prolonged heating and deep frying. These included refractive index, viscosity, colorimetric measurements, and specific gravity. The oils were analyzed before and after purification using four different treatments: Silica-only treatment, Red Sandy Soil-only treatment, sequential treatment (Silica followed by Red Sandy Soil), and finally sequential treatment (Red Sandy Soil followed by Silica). The results showed a significant deterioration in all measured physical parameters (refractive index, viscosity, colorimetric measurements, and specific gravity) as a result of the repeated heating process, compared to the control samples. After purification, Red Sandy Soil alone achieved the highest improvement in the physical properties of the used oils. The combined treatment (Red Sandy Soil followed by Silica) ranked second in efficiency. Red Sandy Soil represents a promising solution as a natural purification agent for used frying oils, demonstrating significantly superior performance in restoring physical properties compared to Silica.