Extra-virgin olive oils, adulteration

Fragaki, G., Spyros, A., Siragakis, G., Salivaras, E., and Dais, P. (2005). Detection of extra virgin olive oil adulteration with lampante olive oil and refined olive oil using nudear magnetic resonance spectroscopy and multivariate statistical analysis. J. Agric. Food Chem. 53, 2810-2816. 

Rohman, A. and Che Man, Y. B. 2010. Eourier transform infrared (ETIR) spectroscopy for analysis of extra virgin olive oil adulterated with pahn oil. Food Res. Int. 43 886-892. 

The first application of ANNs to pyrolysis mass spectra from biological samples was by Goodacre, Kell, and Bianchi.96,97 This study permitted the rapid and exquisitely sensitive assessment of the adulteration of extra-virgin olive oils with various seed oils, a task that previously was labor intensive and difficult. Since this study other laboratories have increasingly sought to apply ANNs to the deconvolution and interpretation of pyrolysis mass spectra, the aim being to expand the application of the PyMS technique from microbial characterisation to the rapid and quantitative analysis of the chemical constituents of microbial and other biological samples. 

Lai YW, Kemsley EK, Wilson RH. 1995. Quantitative analysis of potential adulterants of extra virgin olive oil using infrared spectroscopy. Food Chem 53 95-98. 

These tests are, or have been, used to check for adulteration of extra virgin olive oil (EC Council, 1991 Ntsorankoua et al., 1994). A quicker method for looking for terpene alcohols has been described (Blanch et al., 1998), while esters in waxes have also been examined further (Bianchi et al., 1994). In both of these cases the oil examined was olive but it is likely that this would be useful, though possibly looking for different components, with other oils. 

One hundred and thirty-eight (138) oil samples were analyzed with visible (vis) and near-infrared (NIR) transflectance spectroscopy. Forty-six of them were Greek pure extra virgin olive oils and the same oils adulterated with 1% (w/w) and 5% (w/w) sunflower oil. However, no significant difference was found between the spectrum of pure sunflower oil and that of olive oil, which can be detected by the naked eye. Olive and sunflower oils differ in their composition principally in their content of linoleic and oleic acids. Accordingly, typical figures for olive oil were quoted at 12.3% and 66.3%, respectively, while for sunflower oil the corresponding mean values of 66.2% and 25.1%, respectively. 

Downey, G., McIntyre, P., and Davis, A.N. Detecting and quantifying sunflower oil adulteration in extra virgin olive oils from the eastern Mediterranean by visible and near infrared spectroscopy. Journal of Agriculture and Food Chemistry, 50, 5520-5525. 2002. 

Goodacre, Kell and Bianchi (1993) were successful in detecting adulteration of extra virgin olive oil by using ANNs and PyMS. Extensions to this work are described below in the section on pyrolysis mass spectrometry. 

The wax ester content of olive oil varies widely in different grades of olive oil, being low in extra virgin or virgin olive oil, but it is much higher in solvent-extracted grades of olive oil and this has been accepted as a method of detecting adulteration of pressed olive oil with solvent-extracted olive oil (Nota et al., 1999). 

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