Rapid Determination of Degradation of Frying Oil Using Near-Infrared Spectroscopy

The degradation of frying oil was determined using near-infrared (NIR) spectroscopy and partial least-squares (PLS) regression. One hundred and fifty six samples of frying oil (104 in a calibration set and 52 in a validation set) were obtained after use in an actual potato frying process. NIR transmission spectra of the samples were acquired directly using glass test tubes (13 mm dia.) and a NIR spectrometer. Calibration models with very high accuracy were developed for predicting acid value (AV) and total polar compounds (TPC) using PLS regression with full cross-validation. The coefficients of determination for calibration (R-2) and standard error of cross-validation (SECV) were 0.99 (SECV: 0.17 mgKOH/g) and 0.98 (SECV: 1.25%) for AV and TPC, respectively. The accuracy of the NIR calibration models was tested using the validation set, yielding values for the root mean square of the prediction (SEP) of 0.17 mgKOH/g and 1.04% for AV and TPC, respectively. The results demonstrate that frying oils can be successfully monitored to a very high accuracy using NIR spectroscopy combined with glass tubes of 13 mm diameter as cells.