The use of in-situ Raman spectroscopy to monitor at real time the quality of different types of edible oils under frying conditions

Abstract

When edible oils are exposed to high temperatures, this leads to several chemical changes. Therefore, it is important to have an analytical method (rapid, reliable, multi-parametric, cost-effective and environmentally friendly) capable of monitoring the quality of edible oils at real time. In this sense, the herein presented work focused on the application of Raman spectroscopy for in situ and real-time monitoring of the quality of four different edible oils (vegetable, corn, peanut and sunflower oil) during a 16-h heating at 180 °C. The quality of the edible oils was assessed through the determination of the peroxide and acid values and total polar compounds (TPC). A total of 68 samples were assessed (17 samples for each edible oil type) and the collected analytical data were processed by means of principal component analysis (PCA) and partial least squares (PLS) regression chemometric tools. The accuracy of the developed PLS models was evaluated in terms of coefficient of determination of prediction (R2P), range error ratio (RER) and residual predictive deviation (RPD). RER values of 12.8, 9.3 and 16.5 and RPD values of 3.4, 2.5 and 5.0 were obtained for the determination of acidity values, peroxide values and TPC, respectively. The reliability of the obtained results indicates that the PLS models developed for the determination of acidity and TPC can be used for quality control while the PLS model implemented for the determination of the peroxide values can only be used for screening purposes.