A collaborative study was designed to examine the applicability of a sensory test which determines the life span of frying oil. Soybean oil (500g) was heated at 170°C for 8 hours a day using an electric fryer. Six types (pork fillet, chicken fillet, sardine, Spanish mackerel, sweet pepper or potato) of foods (50g) were deep fat-fried every 4 hours. Frying was continued until the flavor score dropped to 3, which was defined as the rancid point of frying oil. Anicidine value, carbonyl value, acid value and tocopherol content of the rancid frying oil were also determined.
The life spans of the frying oils to reach the flavor score to 3 were shorter in meat or fish frying than vegetable frying. The life spans were not significantly different among pork, chicken and fishes in spite of the marked differences in their polyunsaturated fatty acid contents. The chemical scores of rancid oils were similar among all frying oils used for different foods. These results suggest that meats and fishes promote the organoleptic deterioration of frying oils more rapidly than vegetables. The examination of the flavor score of frying oil was suggested to be useful to determine the life span of frying oil.