A collaborative study was designed to assess the applicability of a sensory test to determine the life span of frying oil. Soybean oil (500 g) was heated at 170°C using an electric fryer. Fifty gram of three types of foods, Spanish mackerel, chicken fillet and potato, were deep-fat fried every 15 minutes. Frying was continued until the flavor score of oil dropped below 3.
The life spans of the frying oils defined as the frying time until the flavor score reached to 3 were shorter by fish and meat frying than potato frying. The life spans were not significantly different between Spanish mackerel and chicken, in spite of a marked difference in their polyunsaturated fatty acid contents.
The flavor scores of the fried foods tended to be affected extensively by the flavor of frying materials and by personal preference. On the other hand, the flavor scores of frying oil decreased with the progress of frying independently of the frying materials. In the sensory test, the foods fried in the oils with a flavor score 5 or 4 showed good flavor. However, the flavor of the foods fried in the oils with a flavor score 3 began to deteriorate. These results suggest that the flavor score of frying oil is useful to determine the life span of frying oil.