Chemical characteristics of potato chips fried in repeatedly used oils

The objective of the study was to evaluate chemical properties of potato chips fried in repeatedly used oils. Potato chips were deep-fat fried in refined coconut oil (PC: potato chips), refined soybean oil (PS), pure olive oil (PO), and vegetable shortening (PH) used up to 80 times repeatedly. Oils were extracted from PC (OC: extracted oil), PS (OS), PO (OO), and PH (OH) and analyzed for oxidative stability. The PH was higher in hexanal than the PS and PO (p < 0.05). Nonanal and 2-decenal were most detected in the PO (p < 0.05) and rarely in the PS. 2,4-Decadienal was least detected in the PC (p < 0.05). Fatty acid compositions of frying oils affected levels of nonanal, 2-decenal, and 2,4-decadienal in the potato chips during frying. Total polar compounds in the OC were lower than in the other extracted oils at the 80th repeated frying (p < 0.05). Peroxide value of the OC continuously increased during the repeated frying (p < 0.05), while those of the OO and OH little changed. Conjugated dienes, p-anisidine value, and total oxidation value of the OC were the lowest at all the repeated fryings (p < 0.05). Total polar compounds, peroxide value, and conjugated dienes of the oils extracted from potato chips did not exceed the rejection limits until 80 times repeated use of the oils. In this study, the PC might have less oxidative products, suggesting that the refined coconut oil was the most stable during the repeated frying.