Effect of Defoamers on the Deterioration of Frying Oil Used for Fried Soybean Curd (Abura-Age)

Abstract

In the process of Tofu manufacturing, defoamers such as calcium salts mixed with used frying oil, monoglyceride and silicone resin are employed. In order to clarify the effect of the defoamers on the deterioration of frying oil, 5 commercial defoamers were addedseparetely to the soybean oil and heated at 180°C for 48 hours. The effect of defoamers was estimated by changes of CO. V., I. V., mean molecular weight and viscosity of heated oils. As a result, calcium salts mixed with frying oil ('Awa-KeshiYu') gave undesirable influences, but the other deformers had no effect on frying oil.'Awa-Keshi-Yu was fractionated into 4 fractions by solvent extraction. Among these fractions, benzene-insoluble fraction (10.8%), which was a mixture of calcium sal tof fatty acids and calcium carbonate, gave the most deteriorative effect. This effect was also confirmed by using synthesized calcium palmitate. Addition of calcium carbonate to calcium palmitate accelrated the deterio ration.