Vol. 31, 2013, No. 5: 474–482 Czech J. Food Sci. Authentication of Riesling Wines from the Czech Republic on the Basis of the Non-flavonoid Phenolic Compounds Pavel PAVLOUšEK and Michal KUMšTA Department of Viticulture and Oenology, Faculty of Horticulture, Mendel University in Brno, Lednice, Czech Republic Abstract Pavloušek P., Kumšta M. (2013): Authentication of Riesling wines from the Czech Republic on the basis of the non-flavonoid phenolic compounds. Czech J. Food Sci., 31: 474–482. Eighteen non-flavonoid phenolic compounds comprising hydroxybenzoic acids, hydroxycinnamates, and stilbenes were analysed in 43 monovarietal wines originated from five wine-growing regions in the Czech Republic. The non-flavonoid phenolic compounds in wine were analysed by a HPLC method. The methods of multivariate statistical analysis were used for the wine discrimination on the basis of the geographical origin. The canonical discriminant analysis (CDA) proved the possibility to discriminate wines according to their provenance on the basis of the following parameters: protocatechuic acid, p-hydroxybenzoic acid, caftaric acid, p-coutaric acid, trans-resveratrol, and cis-resveratrol. On the basis of statistical analyses, 95.4% of the wine samples were correctly classified. The results therefore indicate that the non-flavonoid phenolic compounds can be used to discriminate the geographical origin of white wines. Keywords: high-performance liquid chromatography; multivariate analysis; wine; terroir; chemotaxonomy The grapevine (Vitis vinifera L.) is the most the authenticity based on geographical origin is widespread cultural plant in the world. The plant- under way emphasising thus the importance of this ing location is situated between 52° northern and study. Particularly wine is a product with a very 40° southern latitude. Wine, the main product close relation to its terroir. The wine origin has made from grapes, has a very close relation to its been considered to be the quality indicator and geographical origin. The terms of authenticity and wine consumers often require information on the traceability are therefore very important for the provenance and prefer it (Atkin & Johnson 2010). wine producers and consumers. Generally, the differentiation and classification of Wine ranks among the food products which are wine samples on the basis of their chemical com- often subject to falsification from the point of view position, geographical origin, variety, or quality of the variety or geographical origin. The authen- belong to the basic applications of chemometric ticity of food products has also a significant value methods in enology (de Villiers et al. 2005). for the consumers. It is especially important for Wines have been classified on the basis of their ge- wine which is influenced by many factors related ographical origin according to the profile of phenolic to a certain wine-making region: variety, soil and compounds (Galgano et al. 2011; Li et al. 2011; climate, technology of wine production. There are Soto Vázques et al. 2011), aromatic compounds strict rules for defining the geographical origin of (Green et al. 2011), amino acids (Bouloumpasi et wine according to the region in many wine-growing al. 2002), mineral elements (Paneque et al. 2010; countries (Cynkar et al. 2010). Pérez-Trujillo et al. 2011), isotope ratios (Adami In the Czech Republic, the progressive transition et al. 2010), or a combination of mineral elements of wine authenticity based on grape variety towards and isotope ratios (Dutra et al. 2011). 474 Czech J. Food Sci. Vol. 31, 2013, No. 5: 474–482 Phenolic compounds are significant secondary very often used for differentiation of the origin plant metabolites which are found in grape skin, and authentication of wines (Makris et al. 2006; seed, and pulp of the berry and are extracted into Pour Nikfardjam et al. 2006; González-Neves wine (La Torre et al. 2006). They are a group et al. 2007; Rodriguez et al. 2011). of secondary metabolites with various chemical There is a relative lack of information published structures and functions, and are formed during in relation to the comparison of individual non- the physiological plant growth or in a response to coloured phenolic compounds in wines made from different forms of environmental stress (Naczk one cultivar but from different wine-growing areas & Shadidi 2004). Phenolic compounds can be (Li et al. 2011). successfully used for wine authenticity assessment The Czech Republic belongs with its natural as they are characteristic for the type of wine and and climatic conditions among the wine-growing can provide information on geographical origin states of “cool climate viticulture” and its vineyards (Andreu-Navarro et al. 2011). Gambelli and cover the area of approximately 20 000 ha. Ries- Santaroni (2004), Pereira et al. (2006), Rastija ling belongs among the typical varieties for “cool et al. (2009), and Li et al. (2011) observed differ- climate viticulture” and the same applies to the ences in the concentration of phenolic compounds Czech Republic as well. Riesling is cultivated on the in wines of different geographical origins. area of 1266 ha in all wine-growing regions and it The wines from four Austrian regions can be dif- is the fourth most cultivated variety of grapevine ferentiated on the basis of their geographical origins in the Czech Republic. with the use of phenolic compounds, preventing The aim of this study is to characterise 43 mono- thus the wine falsification (Jaitz et al. 2010). varietal wines from five wine-growing regions in Phenolic compounds are among of the most the Czech Republic on the basis of the concentra- significant qualitative parameters. They are di- tion of non-flavonoid phenolic compounds, i.e. vided into two main groups: non-flavonoids and hydroxybenzoic acids, hydroxycinnamates, and flavonoids. In the case of white grapes and wines, stilbenes and, in addition, with the use of multivari- the group of non-flavonoid phenols is more sig- ate statistical analysis and among the non-flavonoid nificant. Non-flavonoids involve hydroxybenzoic phenolics to find markers which enable to differenti- acids, hydroxycinnamates, and stilbenes (Li et al. ate wines on the basis of their geographical origins, 2009; Rentzsch et al. 2009; Cheynier et al. 2010). i.e. individual wine-growing regions. Hydroxycinnamic acids in wine originate from hydrolysis of hydroxycinnamic and tartaric esters during the fermentation (Cheynier et al. 1986). MATERIAL AND METHODS Hydroxycinnamic acids in wine cause its brown- ing, they are oxidation substrate and contribute to Wines. 43 commercial monovarietal wines of the bitter taste in wine. Hydroxybenzoic acids are the variety Riesling were sampled in five wine- a minor group of phenolic compounds contained growing regions in the Czech Republic. All wines in wine (Waterhouse 2002). Stilbenes are a sub- were produced over the years 2005–2008. Eight group of phenolic compounds naturally present in wines come from the 2005 vintage, 11 from 2006, various plants, but grapes and wine are the most 13 from 2007, and 11 from 2008. Seven wine sam- significant dietetic sources of these compounds. ples originated from the wine-growing region of More analytical methods are applicable to the Mikulov, 12 from Slovácko, 3 from Velké Pavlovice, identification and determination of phenolic com- 13 from Znojmo, and 8 from the Litoměřice region. pounds, but high-performance liquid chromatog- Determination of non-flavonoid phenolic com- raphy is the most used one (Fanzone et al. 2010). pounds. In all wine samples of the variety Riesling, For the wine authenticity assessment, chemical the following non-flavonoid phenolics were analysed: analysis and chemometric methods are used. Wine hydroxybenzoic acids (gallic acid, protocatechuic is composed of a large amount of compounds, and acid, p-hydroxybenzoic acid, vanillic acid, syringic some of them can serve as chemometric markers acid), hydroxycinnamates (caffeic acid, caftaric acid, for the determination of the geographical origin of p-coumaric acid, p-coutaric acid, ferulic acid, fertaric wine. Methods of multivariate analysis comprised acid, ethyl caffeate, p-coumaric acid ethylester, feru- of principal component analysis (PCA) and ca- lic acid ethylester) and stilbenes (trans-resveratrol, nonical discriminant analysis (CDA) are therefore cis-resveratrol, trans-piceid, cis-piceid). 475 Vol. 31, 2013, No. 5: 474–482 Czech J. Food Sci. HPLC analysis. The concentrations of the individ- p-hydroxybenzoic acid, gallic acid, syringic acid, ual phenolic compounds were determined using the p-coumaric acid, trans-resveratrol, trans-piceid, method with direct injection of the sample (Kumšta caffeic acid, ferulic acid, and perchloric acid were et al. 2012). The method is described here briefly. obtained from Sigma-Aldrich (St. Louis, USA). The samples of wine were centrifuged at 3000 g for Other chemicals used were at least of analytical 6 min and diluted with 100 mmol/l HClO4 in a ratio of grade and were obtained from local suppliers 1:1. The chromatographic system Shimadzu LC-10A (Lachema-Penta, Brno, Czech Republic). consisted of two pumps LC-10ADvp, a column ther- The stock standard solutions were prepared by mostat with manual injection valve, a DAD detector accurately weighing about 10 mg of each phenol SPD-M10Avp, and a personal computer running the in a 25 ml volumetric flask. The standards were chromatographic software LC solution (all Shimadzu, dissolved in 10 ml of acetonitrile and made up to Kyoto, Japan). The chromatographic separations volume with distilled water. were performed on a column Alltech Alltima C18 cis-Resveratrol was obtained by exposing the (3 μm, 3 × 150 mm; Grace, Deerfield, USA) equipped trans-resveratrol standard solution to direct UV light with a guard column (3 × 7.5 mm i.d) filled with the for 10 minutes. The source of UV light was the fluo- same sorbent. The temperature of the separations rescent tube Philips Ultraviolet TUV 30W/G30 T was 60°C. The mobile phases were the following: A = (Philips, Rosemont, USA). The sample was placed 15 mmol/l HClO4 and B = 15 mmol/l HClO4, 10% directly under the tube in a sealed quartz cell.