Spectro-Electro Array: Authenticity and Contamination in Food Products

Secondary metabolites, including polyphenols, alkaloids, and terpenoids, provide food products with pigmentation, health benefits, and sensoric qualities. These compounds may lend disease protection to botanicals and supplements and, in the case of polyphenols, enhance the quality of tea, wine, and beer.^1,2,3,4 Recently, Paul Ullucci et al.⁵ released a comprehensive approach that uses metabolite patterns to evaluate food products for authenticity and adulteration. Using UltiMate 3000 gradient high-performance liquid chromatography (HPLC) technology that couples photodiode array detection (UV array) with coulometric electrode array electrochemical detection (EC array), they profiled and quantified secondary metabolites in various beverages, including wine, tea, and fruit juice (Thermo Scientific). The researchers relied upon Chromeleon CDS and CoulArray software for data analysis. For the wine samples, the researchers measured several hundred analytes, including known and unknown compounds, from four Cabernet Sauvignon samples and one Burgundy sample. They used principal component analysis (PCA) to distinguish among samples and to demonstrate the approach’s proficiency in differentiating among grape varietals, blends, and even growing regions. They also used this approach to measure several hundred known and unknown analytes in green, white, black, and Earl Grey tea samples. They were able to distinguish among the tea varieties and note that even the metabolite profiles of black and Earl Grey teas were distinct. It is unknown whether these differences result from the bergamot flavoring of the Earl Grey tea or subtle dissimilarities inherent in the black tea base of the Earl Grey sample and the black tea sample itself. Finally, they applied spectro-electro array detection, combined with PCA, to analyze orange juice. In this way, they detected as little as 10% juice adulteration with grapefruit juice, orange peel, or pulp wash in the samples. They also created a dendrogram to demonstrate the relationships between orange varietals and growing location. Ullucci et al. note that spectro-electro array detection allows researchers to take advantage of the universality of UV technology combined with the sensitivity and selectivity of EC array detection. Specifically, EC array boasts low pg limits for sensitive detection and voltammetric resolution of coeluting compounds. The researchers also report that the EC array can be used with gradients to increase the number of measurable analytes. Applications for spectro-electro array technology include the evaluation of food products for adulteration, contamination, composition, and stability. For wines and juices, the pattern of secondary metabolites may allow researchers and producers to determine key differences among varietals and growing regions and the effects these differences play in the sensorial qualities of the product. Additionally, this approach may prove useful in the fields of botanical and supplement testing, fuel and oil testing, drug testing, and testing to identify counterfeit products. References 1 Cheynier, V. (2005) ‘Polyphenols in Foods Are More Complex Than Often Thought.’ American Journal of Clinical Nutrition, 81 (Suppl. 1), pp. 223S–229S. 2 Garrido, J. and Borges, F. (2011) ‘Wine and Grape Polyphenols: A Chemical Perspective.’ Food Research International, 44 (10), p. 3134. 3 Soares, S. et al. (2013) ‘Different Phenolic Compounds Activate Distinct Human Bitter Taste Receptors.’ Journal of Agricultural and Food Chemistry, 61(7), pp. 1525–1533. 4 Lesschaeve, I. and Noble, A.C. (2005) ‘Polyphenols: Factors Influencing Their Sensory Properties and Their Effects on Food and Beverage Preferences.’ American Journal of Clinical Nutrition, 81 (1), 330S–335S. 5 Ullici et al. (2013) ‘Product Authentication and Adulteration Determination Using a Novel Spectro-Electro Array Platform.’ Application Note 1064, Thermo Fisher Scientific, Chelmsford, MA, USA.