Rapid analysis of major components and potential authentication of South African olive oils by quantitative 13C nuclear magnetic resonance spectroscopy
We have developed a rapid, quantitative 13C NMR spectroscopic method for the determination of the major fatty acids (oleic, linoleic and saturated acids) contained as triacylglycerides in South African extra-virgin olive oils. With the judicious use of a shiftless NMR relaxation agent, Cr(acetylacetonate)3, it is possible to determine the principal fatty acids in 0.4 g of olive oil within 20 min. This method also allows for the estimation of the distribution of the oleic and linoleic acids in the naturally occurring triacylglycerides in olive oils, expressed as α/β ratios for the triacylglycerides. Moreover, a fake product, marketed in South Africa as an 'extra-virgin olive oil', was also analysed to demonstrate the use of 13C NMR spectroscopy as a rapid means of establishing the authenticity of the claimed product on the local market. We further examined a selection of extra-virgin olive oils produced in various regions of the Western Cape province in 2002 and 2003, using 13C NMR spectroscopy, in a preliminary attempt to determine their major fatty acid compositions, and to establish whether any regional and cultivar-based differences in these products can thereby be detected.