Combining FTIR on-device strategies for continuous analysis of virgin olive oil, avocado oil, and lipid matrices degradation

Fourier transform infrared (FTIR) spectroscopy is a highly effective technique for monitoring chemical changes in edible oils throughout their shelf life. This study combined FTIR accessories with different incubation procedures to track the degradation of virgin olive and avocado oils under moderate temperature (35 °C) and light exposure from the early stages. The FTIR procedures were also tested with lipid standards that were used as molecular models and subjected to the same incubation conditions. While conventional ATR-FTIR analysis of off-site incubated samples revealed only minor spectral changes, on-device strategies—temperature-controlled ATR-FTIR and mesh cell-FTIR—enabled continuous spectral acquisition, with key spectral bands appearing on scale, informing on the oil susceptibility to degradation caused by mild heating and photooxidation. The combination of these techniques provided comprehensive insights of the chemical changes. One technique (ATR-FTIR) detected changes in triacylglycerol bands, while the other (mesh cell-FTIR) highlighted oxidation-related absorptions. Notably, bands associated with hydroperoxides, free fatty acids, and cis double bonds exhibited the highest formation rate slopes. Compared to edible oils, triolein showed fewer spectral changes, with free fatty acid slopes in oils being 16 times higher. These findings emphasize the influence of minor compounds on the spectral behavior of oils when exposed to light and mild heat.