Infrared Spectroscopy of Heat-Treated Oils

The infrared spectra of untreated and heat-treated oil samples for 4 h and 8 h, respectively, were recorded at room temperature (25 °C) in the range from 400 to 4000 cm⁻¹ with a Shimadzu FTIR-8400S spectrometer (Shimadzu Corporation, Kyoto, Japan) equipped with an Attenuated Total Reflectance (ATR) accessory interfaced to a computer operating under Windows based on the Shimadzu IR solution software. The infrared spectra were obtained by subtracting the air reference spectrum. Reference and samples were measured with a scan time of 60 s and a resolution of 4 cm⁻¹. A total of 1 mL of the SFO sample was disposed in a thin layer and used to record the FTIR spectra. The spectra were recorded in triplicate as absorbance values at each data point. The fixed-point method was applied to all recorded infrared spectra for baseline corrections [43 (link)].