Standard reagents, namely, fatty acid methyl standards, Vitamin E reference standards (d-α-, β-, γ-, and δ-tocopherol), 2,2,5,7,8-pentamethyl-6-hydroxychroman, and (E)-2-decenal, were purchased from FUJIFILM Wako Pure Chemical Corporation (Osaka, Japan). A custom alkane blend standard of C6–C16 was obtained from Restek Corporation (Bellefonte, PA, USA). Hydrochloric acid was purchased from Kanto Chemical Company Limited (Tokyo, Japan). Hexane, methanol, acetic acid, isopropanol, butylated hydroxytoluene, potassium hydroxide, 2,4-dinitrophenylhydrazine (2,4-DNPH), and n-butanol were purchased from FUJIFILM Wako Pure Chemical Corporation. Among them, Hexane and isopropanol were chromatography grade and all other chemicals were analytical grade.
The camellia oil and frozen par-fried French fries were purchased in the local market (Akita, Japan). The frying process involved frying French fries at 180 °C in a restaurant-style stainless steel electric fryer (TF-20A, Taiji & Company Limited, Kanagawa, Japan) using three liters of oil. The temperature of the frying oil was kept constant at 180 °C during frying, and 75 g of French fries were fried for 3 min at 27 min intervals. This operation was repeated for 5 h per day for 5 consecutive days, with 150 mL of frying oil taken every 2.5 h, without adding additional oil to the fryer. Oil samples were stored at −18 °C before analysis.
The camellia oil and frozen par-fried French fries were purchased in the local market (Akita, Japan). The frying process involved frying French fries at 180 °C in a restaurant-style stainless steel electric fryer (TF-20A, Taiji & Company Limited, Kanagawa, Japan) using three liters of oil. The temperature of the frying oil was kept constant at 180 °C during frying, and 75 g of French fries were fried for 3 min at 27 min intervals. This operation was repeated for 5 h per day for 5 consecutive days, with 150 mL of frying oil taken every 2.5 h, without adding additional oil to the fryer. Oil samples were stored at −18 °C before analysis.