A relationship between the amount of polar compounds and the sensory scores of fried foods and deep-frying oil

Abstract

A relationship between the evaluation of fried materials and the amount of polar compounds was investigated. Fresh oil and the used oil with three degrading degrees (Acid value: about 1, 2 and 4.5) were used in this study. The fried materials (fried batter, maitake tempura and croquette) and frying oil itself were sensory evaluated by the Ranking Method. There were significant differences among the evaluation scores of the oils and of the fried materials prepared with different degrading oils (Kruscal-Wallis test, n = 40, P<0.01). In proportion as the oil was degraded the flavor of the fried materials fell off. Sensory evaluation panelists distinguished the quality of fried materials prepared with different degrading oils, but it tended to be difficult to distinguish highly deteriorated oils containing higher than 15% polar compounds (Turkey's method, P<0.05). Fried batter and maitake tempura fried with the oil containing less than 15% polar compounds and the oils themselves were evaluated to be good by the panel. Croquette was rated high when it was fried with the oil containing about 24% polar compounds. When the polar compound content increased higher than 15% level, the evaluation scores of the fried materials tended to lower and the acid value exceeded the standard value to discard the used oil. Therefore, it is our opinion that the measurement of polar compounds is useful in judging whether deep-frying oil is usable or not.