Olive adulteration

The application of 13C NMR for the rapid analysis of the oil composition of oil seeds is well known [16], 13C NMR has recently been applied to the quantitative analysis of the most abundant fatty acids in olive oil [17]. The values obtained by this method differed by only up to 5% compared with GLC analysis. The quantitative analysis was applied to the olefmic region of the high resolution 13C NMR spectrum of virgin olive oil to detect adulteration by other oils which differed significantly in their fatty acid composition. The application of the methodology for the detection of adulteration of olive oil by hazelnut oil is more challenging as both oils have similar chemical profiles and further experiments are in progress. 

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. 

Goodacre, R. Kell, D. B. Bianchi, G. Rapid assessment of the adulteration of virgin olive oils by other seed oils using pyrolysis mass spectrometry and artificial neural networks. J. Sci. Food Agric. 1993, 63, 297-307. 

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. 

Samples. Eleven hazelnut oils, 25 olive oils, and 7 other types of oil (canola, soybean, corn, sunflower, sesame, walnut, and peanut) were purchased from local grocery stores and Internet suppliers. For the adulteration studies, 10 olive oil and 10 hazelnut oil brands were randomly chosen from the samples purchased, and blends of olive oil... 

B. M. Cordero, and M. Forina, Electronic Nose Based on Metal Oxide Semiconductor Sensors as a Fast Alternative for the Detection of Adulteration of Virgin Olive Oils, Anal. Chim. Acta 2002,459, 219 C. L. Honeyboume, Organic Vapor Sensors for Food Quality Assessment, J. Chem. Ed. 2000, 77, 338 E. Zubritsky, E-Noses Keep an Eye on the Future. Anal. Chem. 2000, 72. 

El-Fizga (108) developed a simple, rapid method for the detection of oils high in linoleic acid in olive oil by RP-HPLC and a simple authenticity factor and a derived equation to determine the extent of adulteration with a one short chromatographic step, completed in less than 15 min. They used two 150 X 4.5-mm ID stainless steel columns packed with an octyl-bonded silica stationary phase (Supelcosil-LC 8) (Supelco. Bellefonte, PA, USA) and a differential reffactometric detector. The isocratic mobile phase was acetone-acetonitrile (70 30, v/v) (Table 5). 

F Dionisi, J Prodolliet, E Tagliaferri. Assessment of olive oil adulteration by reversed-phase high-performance liquid chromatography/amperometric detection of tocopherols and tocotrienols. J Am Oil Chem Soc 72 1505-1511, 1995. 

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. 

A major incident of TOCP poisoning affected 10,000 people in Morocco in 1959. The victims had eaten food cooked in olive oil adulterated with TOCP-contaminated lubricating oil. A number of cases of permanent paralysis resulted from ingestion of the contaminated cooking oil. 

It is certain that not all of the oils consumed today are completely authentic with respect to all the descriptions on the label (Grob et al., 1994 Firestone, 2001 Working Party on Food Authenticity, 1996). Although there are published expected chemical compositions of the major edible oils (Codex Alimentarius Commission, 1997), the only oil that has a defined legal composition is olive oil (EC Council, 1991). This does not mean that adulterated oils cannot be identified, but it does mean that, in many cases, doing so is not an easy matter. 

In the UK at least, the Adulteration Act of 1860, the result of the deliberations of the above committee, was the beginning of a more scientific approach to authentication of fats and oils. However, it was still being stated after the turn of the century (Sloane 1907) that, in the USA, butter was being adulterated by oleomargarine and lard, and cream by cottonseed oil and other fats. Indeed the USA equivalent of the UK Adulteration Act, the 1938 Federal Food, Drug and Cosmetic Act, was only passed after a series of even later cases of adulteration coconut and cottonseed replacing cocoa butter and milk-fat (1922), peanut oil in olive oil (1923), lard contaminating butter (1926) and sesame oil in olive oil used in tinned sardines (1936) (Kurtzweil, 1999). 

Three other GC analyses now used in authentication, largely for olive and other oils which should not be refined or solvent extracted, are the determination of waxes, aliphatic alcohols, triterpene alcohols (uvaol and erythrodiol), and stigmastadiene and other sterol-dehydration products (EEC, 1991). These analyses are used at present not to detect adulteration with other oils, but with solvent-extracted or refined oils. However, it is possible that, with solvent-extracted oils, wax, aliphatic alcohol and terpene alcohol compositions, could prove useful in differentiating or detecting different oils. 

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. 

Blanch, G.P., Caja, M.M., Leon, M. and Herraiz, M. (2000) Determination of (E)-5-methylhept-2-en-4-one in deodorised hazelnut oil. Application to the detection of adulterated olive oils. J. Sci. Food Agric., 80, 140-144. 

Misbranding. Olive oil is unique in that it is the oil from one fruit marketed in nine different categories. Seed oils, instead, are almost all oils refined from a single seed species or a mixture of different seeds. Thus, on considering fraud and adulteration practices, it is advisable in the olive oil field to avoid misunderstanding by using the following words in accordance with their clearly strict definition ... 

In some cases where extreme refining conditions have been used, complete removal of the sterols, both free and esterified, may occur (Grob et al., 1994). By removing the sterols from an oil in this way, it is possible to prepare an adulterant that is undetectable by sterol analysis. As with adulteration of virgin olive oil with refined olive oil, this type of adulteration may be detected by analysis of sterol degradation products. 

In some cases, analysis of tocopherols can be used to detect adulteration of oil. Both palm oil and grapeseed oil are relatively unusual in containing significant levels of tocotrienols, which are absent or present at much lower levels in most vegetable oils (Table 6.3). Detection of these compounds can be used to identify adulteration in olive oil at levels as low as 2% (Dionisi et al., 1995). 

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). 

The major conceptual limitation of all regression techniques is that one can only ascertain relationships, but one can never be sure about underlying causal mechanism. The explanation of conclusions with the assistance of other sciences would avoid reaching nonsense conclusions. A hypothetical paradigm can be to use the electronic nose for detecting the adulteration of refined olive oil with refined seed oils when these kinds of oils do not contain volatiles (refined process of vegetable oils includes the deodorization). 

Baeten, V., Meurens, M., Morales, M.T. andAparichio, R. (1996) Detection of virgin olive oil adulteration by fourier transform raman spectroscopy. J. Agric. Food Chem., 44, 2225-2230. 

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