Identification of Lard Adulteration of Cooking Oil Products Using Fourier Transform Infrared Spectroscopy Combined with Chemometrics

This study employed Fourier-transform infrared (FTIR) spectroscopy in conjunction with chemometrics to identify the main ingredient used to produce cooking oil products as well as their adulteration by lard. However, lard and ingredient fraud in cooking oils occurred. The use of FTIR spectroscopy to detect lard adulteration and ingredient fraud combined with chemometrics was employed at wavenumbers ranging from 4000 to 400 cm⁻¹. The oils’ standard concentrations are made from 0 to 100% crude palm oil (CPO) or virgin coconut oil (VCO). This study employed two main ingredients, VCO and CPO. Antioxidants in commercial cooking oils, such as vitamin E and tert-butylhydroquinone (TBHQ), and butylated hydroxytoluene (BHT) must be removed to avoid interference with FTIR spectra. In this study, the antioxidant used in cooking oil products is BHT, which was extracted using methanol for 120 min and then centrifuged to separate the antioxidant and oil layers. Finally, the extracted oils were analyzed using FTIR, and their spectral data was analyzed using chemometrics to determine the best coefficient determination (R²) and the smallest root-mean-square error of calibration (RMSEC). The findings were used to predict the main ingredient source and lard adulteration in cooking oil products using principal component analysis (PCA). The quantitative analysis of lard-CPO, conducted at wavenumbers 1500–1085 cm⁻¹ and 1800–1600 cm⁻¹, revealed a high R² of 0.9989 using the calibration equation Y = 1.0013x + 0.4712 and a minimum RMSEC value of 1.001%. In contrast, the quantitative analysis of lard-VCO at the wavenumber 1500–1085 cm⁻¹ found R² = 0.9994 using the equation Y = 0.9985x + 0.1352 and an RMSEC of 0.918%. These findings were applied to determine the main ingredient source in cooking oil products and to investigate lard contamination. Based on the PCA results, the characteristics of cooking oil products exhibited more similarity to CPO than others, with the best qualitative analysis observed first derivative FTIR spectra at wavenumbers 1500–1085 cm⁻¹. Therefore, it was concluded that cooking oil products were made primarily with CPO as the main ingredient and none of these products contained lard. CPO is the main component of cooking oil products identified using first derivative FTIR spectra at wavenumbers 1500–1085 cm⁻¹. Furthermore, because the items did not contain lard, all commercial cooking oils were considered halal.