Extending the Lifetime of Frying Oil through Optimization of Fryer Cleaning

With increases in consumer demand for fried foods in Japan over the last several decades, the consumption of frying oil has also steadily increased. Fryers used in restaurants to cook large quantities of food are typically cleaned using neutral kitchen detergents at the end of the day after removing the oil from the tank. However, significant amounts of debris can remain in the fryer after cleaning, possibly accelerating oil deterioration and thus reducing the quality of the fried foods. In this study, debris obtained from fryer tanks used in actual restaurants was assessed using scanning electron microscopy-energy dispersive X-ray spectroscopy together with Fourier transform infrared spectroscopy, and were determined to comprise polymerized oil and carbonized organic matter. Experiments using artificially prepared debris confirmed that these materials increased the acid value (AV) of frying oil. Trials in two restaurants serving similar amounts of fried chicken, French fries and doughnuts examined the effects of cleaning the fryer with either an alkaline detergent or a neutral kitchen detergent on debris removal and oil life. The alkaline detergent was found to completely remove debris while the neutral detergent left significant amounts of debris. After cleaning, the fryers were operated with new oil as usual and the deterioration of this oil was monitored by assessing the color difference, AV, carbonyl value and peroxide value. These indices increased 1.3 to 2.0 times faster in the case that the neutral kitchen detergent was used, suggesting that cleaning fryer tanks with an alkaline detergent could contribute to extending the lifetime of frying oil, reducing food losses and thus achieving sustainable development goals.