ANALYSIS OF TOTAL ANTIOXIDANT CAPACITY AND TOTAL PHENOLIC CONTENT (TP) DURING RIPENING OF TWO SICILIAN RED GRAPES VARIETIES

ANALYSIS OF TOTAL ANTIOXIDANT CAPACITY AND TOTAL PHENOLIC CONTENT (TP) DURING RIPENING OF TWO SICILIAN RED GRAPES VARIETIES During the last decade the interest for polyphenols has increased considerably because numerous epidemiological studies, supported by several short term controlled randomised clinical trials, have suggested associations between consumption of polyphenol-rich food or beverages and the prevention of certain chronic diseases associated with the oxidative stress condition (1). In a our previous study on several samples of Sicilian red wine we found that the total polyphenol parameter can not to characterize the nutraceutical properties of a wine by only because the correlation between antioxidant capacity and the total phenolic contents is weak (2). Grapes composition influences the quality of wine and the polyphenolic compounds are an index to establish the exact time of grapes harvest. During the ripening grapes the polyphenolic content changes and this aspect modify the chemical, technological and nutritional characteristics of a wine. The aim of work was to determine the Total Antioxidant Capacity (TAC) by crocin bleaching assay (2-4) and Total Phenolic Content (TP) by Folin Ciocalteau method of two Sicilian red grapes varieties, Nero d’Avola and Petit Verdot, during ripening for three consecutive vintages. In order to valorize the healthy qualities of grapes and to establish whether exist a period during ripening in which the best technologic, nutraceutical and salutistic parameters coexist. In all vintages, statistically significant differences in TP values were found between the three varieties (p<0.01), In all three years Nero d’Avola grape musts have shown the higher TP values than Petit Verdot. Moreover, during 2008 and 2009 ripening, TP values increased, respectively, of 23.1% and 7.3% for Nero d’Avola, and 30.9% and 55.7% for Petit Verdot. All TP variations proved to be associated with climatic conditions. The antioxidant characteristics of different cultivars are unequally influenced by the vintages. In 2009, Petit Verdot has shown the best antioxidant properties while Nero d’Avola during the 2010 vintage. Significant positive correlations between TP and TAC were detected during the 2009 vintage only: indeed, Nero d’Avola grapes reached their TP and TAC peak values after 13 days from the beginning of ripening, while Petit Verdot grapes after 26 days. Determination of TP during grape ripening is critical to assess the best period of grape harvest. However, higher TP values do not always overlap with higher TAC values, which are indeed strictly related to nutraceutical properties. Reference 1Rodrigo R, Miranda A,Vergara L, Clinica Chimica Acta 2011, 412, 410-24 2Di Majo D,La Guardia M,Giammanco S,La Neve L,Giammanco M. Food Chemistry 2008,111,45-9 3Tubaro F, Micossi E,Ursini F. Journal American Oil Chemical Society 1996, 73, 173–9 4Ordoudi, S. A., & Tsimidou, M. Z. 2006, Journal of Agricultural Food Chemistry, 54, 1663–71.