Authentication of olive oil

This chapter presents an overview of the methods of extraction, together with descriptions and designations, of olive oils (European Community Council regulations EC 136/66 and EC 1638/98), and explains and comments on the purpose and scope of the relevant official methods of olive oil analysis according to the European Community (EC) regulation EC 2568/91 and subsequent additions and amendments (EC Council, 1991).a 

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Flor et al. (1993) were the first to develop criteria for the authentication of olive oil based on vegetable oil HPLC data. They observed that corn, cottonseed, soyabean, sunflower and safflower oils, to mention the most important commercial products, have large peaks for LLL, LLO and LLP but generally smaller LOO and LOP peaks (abbreviations P, palmitic O, oleic S, stearic L, linoleic Ln, linolenic Po, palmitoleic). Additional typical peaks were observed LnLL peak (ca. 7%) in soyabean and LnLO peak (ca. 7%) in rapeseed oils, respectively. Other relevant compositional pictures were observed peanut oil displays a relatively small LLL peak (ca. 3.5%) but larger LLO and LLP peaks (ca. 18.2, 5.9%, respectively). 

Joint Food Safety and Standards Group (of the Ministry of Agriculture, Fisheries and Food and the Department of Health) (1999) Authenticity of olive oils. Food Surveillance Information Sheet No. 180. Food Standards Agency, UK. 

Tay, A., Singh, R.K., Krishnan, S.S., and Gore, J.P. Authentication of olive oil adulterated with vegetable oils using Fourier transform infrared spectroscopy. Zeitschriftfur Lebensmittel Untersuchung und Forschung, 35, 99-103. 2002. 

Among the different chemometric methods, exploratory data analysis and pattern recognition are frequently used in the area of food analysis. Exploratory data analysis is focused on the possible relationships between samples and variables, while pattern recognition studies the behavior between samples and variables [95]. Principal component analysis (PCA) and partial least-squares discriminant analysis (PLS-DA) are the methods most commonly used for exploratory analysis and pattern recognition, respectively. The importance of these statistical tools has been demonstrated by the wide number of works in the field of food science where they have been applied. The majority of the applications are related to the characterization and authentication of olive oil, animal fats, marine and vegetable oils [95], wine [97], fruit juice [98], honey [99], cheese [100,101], and so on, although other important use of statistical tools is the detection of adulterants or frauds [96,102]. 

By the nature of the process by which olive oil is extracted from the olive, the oil is susceptible to contamination. The high price associated with olive oil of the highest purity— extra virgin olive oil — also leads to falsification by unscrupulous vendors who blend with less costly oils such as com, peanut, and soybean oil. Various analytical techniques have been devised to authenticate the purity of olive oil by detecting certain oil components. 

There are a number of minor oils, all of high value, most of which are marketed mainly either for medical purposes or for their flavour. Olive, evening primrose, borage, fish oils and cocoa butter are described elsewhere. Others include hazelnut, walnut, macadamia, almond, apricot, pumpkin, poppy-seed and rice bran oils. The process of testing for authenticity of these oils should be approached in the same way as for the bulk oils above, i.e. fatty acid profile, sterols, tocopherols and triglyceride composition. However, there is little generally available published material on the ranges of values to be expected... 

Spangenberg, J.E. and Ogrinc, N. (2001) Authentication of vegetable oils by bulk and molecular carbon isotope analysis with emphasis on olive oil and pumpkin seed oil. J. Agric. Food Chem., 49, 1534-1540. 

Official analytical methods provide data and results that give soundproof of the authenticity and quality of an olive oil, or, alternatively, elements that permit the uncovering of altered and sophisticated over-classified oils. This section is not to be regarded as a comprehensive presentation of olive oil chemistry and analysis but is intended only to give the reader an overall perspective of the origin and fate, and the chemico-physical properties, of the classes of compounds constituting olive oil. 

Wherever it is considered useful there is the development of simple analytical and structural chemistry elements, as well as of reaction mechanisms, to explain the chemical properties and the induced or spontaneous transformation of the natural oil products. We do not pretend that the official methods presented, and commented on, in this section are the most important for the determination of olive oil authenticity, but we do hope that the methodologies illustrated will represent a foundation upon which the interested reader will achieve familiarity with some of the original classes of compounds and those of new formation that make up olive oil. 

The results of analysis were compared with the limits specified in the Commission Regulation (Joint MAFF and Department of Health Food Safety and Standards Group, 1999a,b). For the purposes of the survey, and in line with the usual practice followed by UK enforcement authorities, where samples were found to lie outside the statutory limits, an additional tolerance was added to take account of potential variations in the analytical methodology. The Commission Regulation makes it clear that an oil may not be considered to fit its description if any one of its characteristics lies outside the limits laid down. On this basis, the majority of the oils analysed were found to be correctly described and only four samples were found to exceed European Commission limits for one or more chemical criteria used to distinguish and authenticate the different grades of olive oil. 

TAG are increasingly used in the food industry as a tool to assess the quality and authenticity of vegetable oils [118,119], particularly adulteration of olive oil with hazelnut oil [120,121]. 

Simpkins and Harrison (1995a) summarize many of the methods used for detection of authenticity in olive oils and many other food products. They note that most new applications they reviewed relied on advanced statistical procedures for data analysis. 

The methods used to attain the correct identification of olive oils will also have to take into account the potential large variability arising from variety, location and environmental differences in the compositional characteristics of pure virgin olive oils thus the availability of reliable methods for authentication of the geographical origin of the oils will be crucial. As discussed above, one possible method is Curie-point PyMS (Section 10.3.2) combined with a powerful multivariate or chemometric analysis technique such as ANNs (Section 10.4.9) (Fig. 10.14). 

L. Mannina and A. P. Sobolev, High Resolution NMR Characterization of Olive Oils in Terms of Quality, Authenticity and Geographical Origin , Magn. Reson. Chem., 2011, 49(S1), S3. 

Bohacenko, I. and Kopicova, Z. 2001. Detection of olive oils authenticity by determination of their sterol content using LC/GC. Czech J. Food Sci. 19 97-103. 

Lerma-Garcra, M. J. 2012. Characterization and authentication of olive and other vegetable oils. Springer Theses, pp. 228. 

Lerma Garcia M. J., (2012). Characterization and Authentication of Olive and Other Vegetable Oils New Analytical Methods, Springer Science Business Media. 

Mannina L, Sobolev AP. High resolution NMR characterization of olive oils in terms of quality, authenticity and geographical origin. Magn Res Chem 2011 49 S3-S 11. 

Louren o, M., G. Van Ransl, B. Vlaeminck, S. De Smet and V. Fievez, 2008. Influence of different dietary forages on the fatty acid composition of rumen digesta as well as ruminant meat and milk. Anim. Feed Sci. Technot 145,418-437. Spangenberg, J.E., S.A. Macko and J. Hunziker, 1998. Characterization of olive oil by carbon isotope analysis of individual fatty acids bnpUcations for authentication. J. Agric. Food Chem. 46,4179-4148. 

E. Bertran, M. Blanco, J. Coello, H. Iturriaga, S. Maspoch and I. Montoliu, Near infrared spectrometry and pattern recognition as screening methods for the authentication of virgin olive oils of very close geographical origins, J. Near Infrared Spectrosc., 8, 45-52 (2000). 

Cosio, M. S., Ballabio, D., Benedetti, S., and Gigliotti, C. (2006). Geographical origin and authentication of extra virgin olive oils by an electronic nose in combination with artificial neural networks. Anal. Chim. Acta 567(2), 202-210. 

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). 

The presence of vegetable oils of high linoleic acid content in olive oil can be detected by measuring its authenticity factor (Au) as follows ... 

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