Oxidative properties and moisture content in repeatedly used oils for French fries and breaded chickens during frying

Changes of oxidation parameters including acid value (AV), total polar materials (TPM), conjugated dienoic acid (CDA), and p ‐anisidine values ( p ‐AV) were evaluated in repeatedly used frying oils for French fries and breaded chickens. As frying time increased, all the oxidation parameters including AV, CDA, p ‐AV, and TPM content increased significantly ( p < 0.05). Frying oils for French fries suffered lesser oxidative deterioration compared to those for breaded chicken although the same oils were used. The 7.7 h heating for oil with water, 115 frying cycles for French fries, and 42 frying cycles for breaded chickens generated about 0.76, 0.78, and 0.78% CDA, respectively, 0.75, 0.78, and 1.69% AV, respectively, and 19.95, 15.99, and 25.20% TPM by column chromatography, respectively. Moisture content in frying oils for French fries was the lowest and that in breaded chicken was the highest. Different values of AV, CDA, p ‐AV, color changes, and TPM were observed depending on frying condition especially the moisture content in frying oils. Practical application: Oxidation parameters and moisture content in frying oils for French fries and breaded chickens were determined. Moisture content in oils affected the oxidative stability a lot. Therefore, controlling the amounts of moisture in frying oils is one of critical steps to retard the rates of lipid oxidation in oils. The results of this study can be applied to extend the usage of frying oils in fast food restaurants. (i) The oxidation parameters were monitored in heated oils with moisture supplement, in frying oils for French fry and in frying oils for breaded chicken. (ii) Frying oils for French fries suffered lesser oxidative deterioration compared to those for breaded chicken although the same oils are used. (iii) Moisture content in frying oils for French fries is the lowest and that in breaded chicken is the highest.