THE INFLUENCE OF THE VINE CULTIVATION TECHNOLOGY ON THE PHENOLIC COMPOSITION OF RED GRAPES Victoria ARTEM 1,2 , Arina Oana ANTOCE 1 , Ioan NAMOLOSANU 1 , Aurora RANCA 2 , Anamaria PETRESCU 1,2 1 University of Agronomical Sciences and Veterinary Medicine of Bucharest, Faculty of Horticulture, Department of Bioengineering of Horti-Viticultural Systems, 59, Mărăşti Ave., Sector 1, 011464 Bucharest, Romania. 2 Research Station for Viticulture and Oenology Murfatlar, Calea Bucuresti str., no. 2, 905100, Murfatlar, Constanta Corresponding author email: arina.antoce@horticultura-bucuresti.ro Abstract The biosynthesis of phenolic compounds and their accumulation during the grape berry ripening is influenced by various factors such as the genotype, climatic conditions and agricultural practices. The phenolic maturity desired at harvest time refers not only to the total phenolic compound concentration, but also to their quality, which is related to their structure and extractability during the winemaking process. The goal of this work was to improve the total concentration of phenolic compounds of the black cultivars Feteasca neagra and Cabernet Sauvignon by applying various viticultural practices such as organic and conventional growing, no cluster thinning and 30% cluster thinning during summer, before veraison. The work was performed during the period of 2013-2014 and the phenolic compounds were evaluated by the standard Glories method, which provided results for total anthocyanins (ApH 1), extractable anthocyanins (ApH 3,2), the percentage of the extractable anthocyanins (%AE), maturity of the seeds (MS) and total phenols (PT). The statistical analysis of the results showed that the main factor that influences the phenolic composition of the grapes and their extractability is the grape variety, but for the same cultivar the cluster thinning and the agrotechnical practices also induced certain significant differences. Key words: phenolic composition, organic, cluster thinning. INTRODUCTION Phenolic compounds are the most important group of chemical substances in grapes, after sugars and acids. They have an important contribution in defining visual, olfactory and gustative sensory characteristics of grapes and wines (Antoce, 2007; Gil-Munoz et al., 2009). Phenolic compounds (anthocyanins, tannins, etc.) accumulates in the solid parts of the grape skin, seeds, rachis; their content is variable, depending on the variety, the maturation degree of grapes, the climatic conditions of the area, farming practices and last but not least the applied winemaking technology (Jackson et al., 1993; Downey et al., 2006). Agricultural practices that influence the expression of phenolic composition during ripening process of grapes, reported in various journals are: the system of trunk formation (Zoeckelein et al., 2008), row spacing, pruning, thinning grapes, removing buds and leaves, irrigation management and fertilization (Gonzales- Neves et al., 2002; Delgado et al., 2004; Poni et al., 2007; Antoce, 2007) and so on. Phenolic compounds in grapes are secondary metabolites, which constitute a category of natural bioactive compounds which show remarkable health benefits for the body (Del Rio et al., 2013), due to their antioxidant or rather due to redox signalling actions. Of these the most important are anthocyanins, the colored pigments of grapes, and tannins from skin and seeds, that are responsible for the red wine astringency and bitterness (Cheynier et al., 2006). The assessment of the 117 Scientific Papers. Series B, Horticulture. Vol. LIX, 2015 Print ISSN 2285-5653, CD-ROM ISSN 2285-5661, Online ISSN 2286-1580, ISSN-L 2285-5653