A collaborative study was designed to examine the applicability of an organoleptic test which determines the limit for using frying oil. We first examined the relationship between deterioration of frying oil and its flavor by using flavor scores 5,4,3,2 and 1 (flavor score 5 was defined as fresh oil; flavor score 1 as the most deteriorated oil). Flavor score 3 was defined as the frying oil's rancid point (heavy flavor reversion, slighty rancid and buttery). To determine the heating time for the oil to reach flavor score 3, potatoes were successively fried every 4 hours in soybean oil at 180°C for 4 minutes. Anisidine and carbonyl values of the frying oil with flavor score 3 were also measured. This experiment was carried out 11 different laboratories, and the data varied: the shortest and longest times for the oil to reach flavor score 3 were 16 and 50 hours, respectively.
To minimize this difference in time, soybean oils with different stages of thermal oxidation were prepared flavor scores 5 to 1; and all the researchers decided upon the standard flavor of those oils. After standarization, the second experiment was carried out in the same manner as that of the first experiment. The data were relatively consistent: the shortest and longest times for the oil to reach flavor score 3 were 16 and 22.5 hours, respectively, and the average time was 19.5 hours. Frying oil with flavor score 3 had anisidine and carbonyl values of 150 and 13.7, respectively.
These results suggest the possibility that this organoleptic test can be used to determine the limit for using frying oil. This test may help us to get fried foods with good flavor.