Computational Modelling of FTIR Spectra

The Gaussian 16 software (Frisch et al. , 2016) was used for all computational modelling and calculations. Oleic acid, palmitic acid, and lauric acids were used as the fatty acids present in TOs required to simulate the photooxidation of TOs (Cheng et al., 2018). The initial geometries of the fatty acids were optimised, and the vibrational frequencies were obtained. The geometry optimisation and vibrational frequency calculations were performed with the density functional theory (DFT) in the gas phase (Pereira et al. , 2017). The basis set used was Becke’s three parameters, and the Lee-Yang-Parr nonlocal correlation functional (B3LYP) at the 6-311++G (d, p) basis set. The final geometries of the fatty acids after the vibrational frequencies were visualised with GaussView (version 6.0.16) (Dennington, Keith and Millam, 2016). A scaling procedure (Palafox, 2019) was implemented to improve the wavenumbers and transmittance of the simulated spectra to match those of the experimental data.

Statistical Analysis

All data were obtained from at least three measurements, and each replicate was reported as the mean standard\(\pm\) deviation. OriginPro (version 2020, Northampton, MA, USA) and SPSS (IBM Corp., 2020, version 27, Armonk, N.Y., USA) were used for the one-way analysis of variance (ANOVA). The significant difference was evaluated by the P-values (P < 0.05).