Comparison of near and mid infrared spectroscopy as green analytical tools for the determination of total polar materials in fried oils

Total polar materials (TPM) are used as an indicator of the quality in the frying oil because of high values may be harmful for human health. Spanish legislation establishes the maximum level of total polar materials for frying fats and oils for human consumption around 25% (w/w). Official methods to monitor oil quality are time consuming and use a lot of chemicals; therefore it is necessary a simple and quick analytical technique to evaluate fried oils. Transmittance near-infrared (NIR) and attenuated total reflection mid-infrared (ATR-MIR) spectroscopy measurements, combined with partial least squares (PLS) regression, offer alternatives to determine TPM in fried oils with relative root mean square error of prediction (RRMSEP) of 7.6% and 11.8% and residual predictive deviation (RPD) of 9.1 and 5.8 by using PLS-NIR and PLS-ATR-FTIR models, respectively.