Quality Change of Three Kinds of Edible Oil during Frying Process

Physicochemical changes of soybean oil,sunflower oil,and palm oil when used to fry potato chips for consecutively 4 h/d a day in 5 consecutive days were evaluated in this study.The color of the three kinds of edible oil became dark and an increase in their viscosity was observed with increasing frying time.Moreover,the acid value(AV) showed an obvious increase but did not exceed the national standard,whereas increasing frying time resulted in gradually reduced iodine value(IV).All these edible oils revealed an initial increase followed by a decrease in peroxide value(POV),and soybean oil and sunflower oil showed fluctuant variations.Soybean oil and sunflower oil revealed a carbonyl value(CV) exceeding or very close to 50 meq O2/kg of the national standard as a result of repeated use for 3 days.On the fourth day,the content of total polar materials(TPM) in both oils exceeded the national standard.In contrast,CV and TPM of palm oil remained lower than those of soybean oil and sunflower oil during the whole frying process.