Qualitative Enhancement and trans-Fat Depletion of Different Used Frying Oils with Adsorbents

Abstract

This study was conducted to enhance the quality of deteriorated frying oils by employing various types of adsorbents. Four vegetable oils─sunflower, soybean, rice bran, and palm olein oil─whose quality deteriorated after deep frying, were treated with six adsorbents─activated carbon, Fuller’s earth, ash, silica gel, aluminum hydroxide gel, and magnesium oxide─at 150 °C for 30 min to reduce the already elevated free fatty acid (FFA %), peroxide value (PV), total polar material (TPM), p-anisidine value (p-AV), and trans-fat. The physical characteristics (color, specific gravity, and refractive index) were also reformed after treatment. Activated carbon outperformed all other adsorbents for palm olein in terms of FFA % and PV reduction. Fuller’s earth lowered the maximum TPM of soybean oil, whereas MgO reduced the p-AV of palm olein. The trans fatty acids of practically all fried oil were lowered to their fresh state except sunflower oil with the adsorbents.