JIMÉNEZ-CARVELO ET AL.: JOURNAL OF AOAC INTERNATIONAL VOL. 100, NO. 2, 2017 345 Fast-HPLC Fingerprinting to Discriminate Olive Oil from Other Edible Vegetable Oils by Multivariate Classification Methods ANA M. JIMÉNEZ-CARVELO, ANTONIO GONZÁLEZ-CASADO, ESTEFANÍA PÉREZ-CASTAÑO, and LUIS CUADROS-RODRÍGUEZ University of Granada, Department of Analytical Chemistry, c/ Fuentenueva, s.n. E-18071 Granada, Spain A new analytical method for the differentiation of olive oil from other vegetable oils using reversed- phase LC and applying chemometric techniques was developed. A 3 cm short column was used to obtain the chromatographic fingerprint of the methyl-transesterified fraction of each vegetable oil. The chromatographic analysis took only 4 min. The multivariate classification methods used were k-nearest neighbors, partial least-squares (PLS) discriminant analysis, one-class PLS, support vector machine classification, and soft independent modeling of class analogies. The discrimination of olive oil from other vegetable edible oils was evaluated by several classification quality metrics. Several strategies for the classification of the olive oil were used: one input-class, two input-class, and pseudo two input-class. V egetable oils constitute one of the main sources of fats in the diet. Olive oil is one of the oils favored by consumers due to its valuable nutritional properties, making it different from other edible oils. The International Olive Council (IOC), based in Madrid, Spain, is the only intergovernmental organization in the world in the field of olive oil. It enables meetings between government representatives and experts to discuss problems and concerns, to draw up quality standards, and to advise governments on the decisions they should make. Olive oil is regulated in the European Union (EU) by two legal provisions: (1) “Commission Regulation (EEC) No. 2568/91 of 11 July 1991 on the characteristics of olive oil and olive-residue oil [actually named olive-pomace oil] and on the relevant methods of analysis,” which has been amended 28 times since its publication in 1991 (more than once per year), with the last amendment dated in October 2015; and (2) “Commission Implementing Regulation (EU) No. 29/2012 of 13 January 2012 on marketing standards for olive oil,” amended in December 2013. In October 2010, the US Department of Agriculture (USDA) published the notice “United States Standards for Grades of Olive Oil and Olive- Pomace Oil,” followed in May 2012 by the Grading Manual for Olive Oil and Olive-Pomace Oil. This manual defines the standardized process for inspection, testing, and authentication and provides a path for authentication and USDA certification through voluntary laboratory testing. Other countries that have similar regulations are the People’s Republic of China (in force since March 2009) and Australia (although the first edition of the standard has not yet appeared). Verification of the requirements specified in these regulations requires (when it is possible) rapid and straightforward analytical methods suitable for the characterization of olive oil and the detection of potential frauds due to the adulteration of olive oil with other, cheaper vegetable edible oils as a way of reducing cost and achieving illicit profits. These analytical methods are upgraded regularly upon consideration of the recommendations proposed by the IOC. The major analytical methodologies applied to authenticate olive oil are focused on the characterization of specific analytical profiles from major components (saponifiable fraction) and minor components (unsaponifiable fraction). The composition of triglycerides (1), fatty acids (2), and phytosterols (3) has been determined by chromatographic methods in order to detect whether an olive oil has been adulterated with other vegetable edible oils (4). The scope of these methods is limited, however, and not all adulterations of olive oil with other vegetable oils are easily detectable, i.e., some vegetable edible oils have a compound profile similar to that of olive oil. For instance, there is not a well-established analytical method to detect the adulteration of olive oil with hazelnut oil due to the fact that they both have similar triacylglycerol and fatty acid compositional profiles. The IOC has claimed for many years that such a method should be developed. Therefore, it is advisable to develop reliable, rapid, and simple methods to control the authenticity of olive oil. An attractive and innovative analytical strategy, which uses the chromatogram as a whole, has recently been applied. This strategy, known as chromatographic fingerprinting (5), starts from the premise that the chemical information necessary to properly characterize and authenticate a particular foodstuff is contained in the chromatographic profile. This critical and useful information is nonevident (i.e., hidden) but could be extracted by applying appropriate chemometrics tools. In recent years, the authentication of olive oil based on instrumental fingerprinting has increased, and the analytical spectroscopy methods most used are near-IR, FTIR, Raman, and NMR. These methods are advantageous because the sample does not suffer any alteration and is not destroyed, and the analysis is quick (6, 7). When chromatographic fingerprinting is applied, a poorly resolved chromatogram is used as a whole SPECIAL GUEST EDITOR SECTION Guest edited as a special report on “Application of Multivariate Statistical Techniques in Chromatographic and Spectroscopic Fingerprinting of Complex Food and Environmental Samples” by Paweł K. Zarzycki. Corresponding author’s e-mail: amariajc@ugr.es DOI: 10.5740/jaoacint.16-0411 Downloaded from https://academic.oup.com/jaoac/article/100/2/345/5654149 by guest on 05 June 2022