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Abstract
Frying, a prevalent cooking method, subjects oils to high temperatures, causing chemical changes and the formation of harmful by-products. Repeated oil use poses health risks, necessitating effective restoration methods. Agricultural waste ashes, including rice, barley, and oak hulls, were investigated for their adsorption capabilities in comparison to conventional adsorbents. Refined sunflower oil was used, and five filter aids, including Magnesol XL, diatomaceous earth, and agricultural waste ashes, were employed. Rice, barley, and oak hull ashes were prepared and characterized for metal content. Scanning electron microscopy (SEM) and Fourier Transform Infrared (FTIR) spectroscopy assessed the surface morphology and chemical structure of ashes. The frying process involved heating oil daily for five consecutive days, with each session lasting 4 h, followed by treatment with filter aids. Comparing the agricultural waste ashes, oak hull ash (OHA) exhibited the highest content of silicate which was almost equal to the conventional adsorbents. SEM revealed the surface properties and superior performance of OHA in adsorbing degradation products. FTIR analysis showed similarities in chemical structure between pure silica and oak hull ash. Initial sunflower oil quality was confirmed through various physico-chemical properties. Frying led to quality deterioration, evidenced by color changes, increased refractive index, viscosity, acidity, peroxide levels, and decreased iodine value. This study underscores the potential of agricultural waste ashes, particularly oak hull ash, as effective adsorbents for enhancing the quality of fried sunflower oil. Their comparable performance to conventional adsorbents, cost-effectiveness, and lack of harmful effects position them as viable alternatives in restoring used frying oils for sustainable culinary practices.