Physicochemical Quality and Thermal Stability of Vegetable Oils during Deep-Fat Frying of Potato Chips

Background: Deep-fat frying induces organoleptic and physicochemical changes in both oils and fried products. Excessive use of frying oils accrues decomposition products with potential hazards to human health. Optimizing frying conditions and selecting the best frying oils are needed for better-fried products. Objective: This study was conducted to investigate the physicochemical changes and thermal behavior of vegetable oils (olive, canola, corn, sunflower and soybean oils) during deep-fat frying of potato chips, and determine the optimum conditions required to produce the best quality fried product. Methods: Thermal behavior, organoleptic characteristics, physicochemical properties (color index, viscosity, specific gravity, peroxide value, free fatty acids, total polar compounds), and fatty acid compositions of oils were investigated during the frying process every 8 hours up to 40 hours of heating. Results: Oils showed different quality and thermal stability. The optimum time and temperature for frying were 10 minutes and 180°C. Sensory attributes, physicochemical characteristics and fatty acid composition of oils were markedly affected by heating. Olive oil was the most stable for frying. Total polar compounds of 27% (the rejection point for frying oils) would be reached upon heating olive oil at 180°C for 114 hours. The corresponding times were 45, 43, 30 and 26 hours for canola, corn, sunflower and soybean oils, respectively. Conclusion: Olive oil showed the highest stability and produced the best-fried product, followed by canola oil. Frying time increased with extended heating, and it could be used as a good indicator of oil quality and when it should be discarded.