Raman spectroscopy study of edible oils and determination of the oxidative stability at frying temperatures

Samples of edible oils of different degrees of unsaturation were studied by Raman spectroscopy. We demonstrate the potential of this technique for discriminating these oils. In addition, the Raman spectra for the macadamia, pecan, and Brazil nut oils are for the first time reported here. The fatty acid profile of each type of oil was established by GC. The analytical results obtained from the spectra were highly correlated with those provided by GC as regards the contents in monounsaturated and PUFA of each oil type. Spectra were examined separately in the wavenumber zones 2800-3100 and 800-1800 cm(-1), which were those exhibiting the greater differences between oils. Also, as shown in this work, Raman spectroscopy is an effective tool for assessing oxidation in various grades of olive oils. Based on the results, extra virgin olive oil efficiently resists oxidation in the short term by virtue of its increased antioxidant contents. Practical applications: Both the amount of total oxidized monomeric TAGs called total oxidized products (TOP) and the amount of di- and polymerized TAGs (DPTG) can be used to describe the fat degradation at all stages. These parameters are less dependent on the fat composition but proportional to the heating time and applied temperature. A procedure is proposed to compare thermal and oxidative stability of vegetable oils and effectiveness of oxidative stabilizing agents.