Physicochemical assessment of vegetable oil used to fry some Nigerian food items

Abstract

The escalating global energy demand, projected to rise from 442 EJ in 2023 to between 623 and 710 EJ by 2035, has intensified the search for sustainable energy alternatives to fossil fuels. Biodiesel, particularly from waste cooking oil (WCO), presents a promising solution due to its affordability and environmental benefits. This study investigates the physicochemical properties of neat and waste sunflower oil used to fry bean cakes (Akara), fish, and puff-puff in Nigeria, aiming to identify the impact of frying duration and fried substances on oil quality. The study’s findings reveal significant changes in the oil’s properties post-frying, with notable variations in pH, moisture content, boiling point, density, viscosity, flash point, saponification value, protein content, fat content, acid value, free fatty acids (FFA), and fatty acid methyl esters (FAME). The results indicated that the moisture content increased from 34.6% in neat oil to 47.9% in oil used for frying bean cakes, while the boiling point decreased from 243 °C to 226 °C in oil used for frying fish. The kinematic viscosity and density also varied, with the lowest viscosity (26.48 mm2/s) observed in oil used for frying fish and the highest density (911 kg/m3) in oil used for frying bean cakes. The flash point of WCO samples ranged from 248 to 258 °C compared to 260 °C in neat oil, and the saponification values varied significantly, indicating different levels of oxidation and deterioration. The study concludes that frying fish has the most detrimental effect on oil quality, as evidenced by the highest acid value (7.2 mgKOH/g) and significant changes in FFA and FAME concentrations. These insights into the physicochemical alterations of WCO highlight the potential for its optimized use in biodiesel production, offering a sustainable energy source while addressing waste disposal challenges.