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Two methods based on polyethylene‐film‐based Fourier transform infrared (PE‐film‐based FTIR) and attenuated total reflectance–Fourier transform infrared (ATR–FTIR) spectroscopy are developed for the determination of the total polar compound (TPC) content of frying oil. The TPC contents of oil samples are analyzed in accordance with the guidelines set by American Oil Chemists’ Society. Calibrations of the PE‐film‐based FTIR and ATR–FTIR spectroscopy measurements, combined with partial least‐squares regression, provide correlation coefficients (R‐values) of 0.9930 and 0.9972, respectively, and root mean error of calibration of 1.55 and 0.75%, respectively. The validation of the calibrations indicates that the R‐values of validation and precision analyses are close to 1. PE‐film‐based FTIR and ATR–FTIR are considered adequate for analytical purposes and provide root mean error of prediction values of 2.90 and 3.10% for blind sample validation, respectively. However, the prediction accuracy of PE‐film‐based FTIR spectroscopy is better than that of ATR–FTIR spectroscopy. Results indicate that the PE‐film‐based FTIR and ATR–FTIR methods can be efficiently applied as environmentally friendly tools for the determination of the TPC content of frying oils. Practical Applications: PE‐film‐based FTIR and ATR–FTIR spectroscopy techniques are compared to develop a convenient and rapid method for the determination of the TPC content of frying oil. A total of 127 oil samples corresponding to unfried and fried domestic oils are used. Among the samples, 107 and 20 samples are allocated to the calibration set and the blind sample validation set, respectively. The ATR–FTIR technique is more rapid than the PE‐film‐based FTIR technique given that it does not require data preprocessing. However, the PE‐film‐based FTIR technique provides better prediction results than the ATR–FTIR technique and lower RMSEP values for the regression between the validation and blind sample validation sets. The superior prediction results provided by the PE‐film‐based FTIR technique may be attributed to its high precision and spectral sensitivity, as well as optical path length. The PE‐film‐based FTIR and ATR–FTIR techniques can be applied as environmentally friendly tools for the determination of the TPC contents of frying oils. Two methods based on PE‐film‐based FTIR and ATR–FTIR spectroscopy are developed for the determination of the TPC content of frying oil. The validation of the calibrations indicates that the R‐values of validation and precision analyses are close to 1. PE‐film‐based FTIR and ATR–FTIR are considered adequate for analytical purposes and provide root mean error of prediction values of 2.90 and 3.10% for blind sample validation, respectively.

Introduction Vegetable oils are important food ingredients and provide humans with essential unsaturated fatty acids UFA and numerous fat-soluble vitamins, whereas oils can oxidize during transport and storage 1. Oil oxidation is an important quality criterion for food industry because this results in off-flavor compounds and also decreases the nutritional quality of food 2. Therefore, it is necessary to monitor and determine the oil oxidation parameters, such as acid value AV , peroxide value, iodine value, saponification value, and moisture content. During the oxidation, oils are prone to hydrolysis and produce free fatty acids FFA under the effects of light, oxygen, microorganisms, and enzymes 3. The American Oil Chemists Society AOCS define the degree of oil hydrolyzation as AV, which represents the content of FFA. Therefore, AV is typical considered to evaluate the oil quality in practical analyses. AOCS has recommended a standard method for AV determination in edible oils, expressed as the number of milligrams of Potassium hydroxide required to neutralize the FFA in 1 g of sample. The titration method involves a large amount of highly toxic, carcinogenic, and environmentally unfriendly organic solvents. The method requires a simple procedure, but it is time consuming, costly, and labor intensive; moreover, the results are largely dependent on the operation of the analysts.