Quality Indices of Recycled Cooking Oil Used in Frying Fish

Student: Abubakar Usman (Project, 2025)
Department of Biochemistry
Northwest University, Kano, Kano State

Abstract

The study evaluates the quality indices of recycled vegetable oil used in frying fish. Repeated use of oil during frying exposes it to high temperatures and oxidation, leading to chemical deterioration. Samples of fresh and recycled oil were analyzed for peroxide value, free fatty acid, iodine value, and saponification value using standard analytical methods. The results showed significant increases in peroxide and free fatty acid values in recycled oil compared to fresh samples, indicating oxidative rancidity and loss of nutritional quality. Iodine values decreased, suggesting reduced unsaturation due to repeated heating. These findings confirm that continuous reuse of oil during frying adversely affects its chemical stability and may pose health risks when consumed. The study recommends proper monitoring of frying oil quality and discourages multiple reuse to maintain food safety and nutritional standards.

Keywords
recycled oil frying fish quality indices vegetable oil peroxide value free fatty acid iodine value saponification value oxidation oil degradation food safety repeated heating edible oil thermal stability
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