Influence of berry ripeness on concentration, qualitative composition and extractability of grape seed tannins

Abstract

Background and Aims:The evolution of seed tannins in three grape varieties grown in the same vineyard was followed from preveraison to harvest, to determine their pattern of accumulation. Also, to elucidate whether the use of 70% acetone as extracting solvent overestimate what will occur during fermentation, seed tannins were extracted throughout the ripening period with a method that involved a 3 days extraction with aqueous 12.5% ethanol and the results compared with the acetone extraction method. Methods and Results: For both methods, the extracted tannins were analysed following acid-catalysis in the presence of excess of phloroglucinol. Seed tannins reached a maximum around veraison and decreased towards maturity, the mean degree of polymerization (mDP) varying only slightly during the studied period. When tannins were extracted with 12.5% ethanol, their concentration was much higher during the first part of the maturation than using acetone but was significantly lower at harvest. Conclusions: The decrease in extractable seed tannins during ripening was observed with both solvents. The differences observed in the concentration of tannins with both solvents could be due to the histochemical changes occurring in seeds during maturation. Significance of the Study: The differences observed in tannin concentration with the two different methods may indicate that when pulp maturity is reached before seeds are ripe, the fermenting solution will extract more tannins than the acetone method. These results point to the importance of extraction methodology when monitoring seed maturity for the prediction of seed tannins in wine.

Application of exogenous 24-epibrassinolide enhances proanthocyanidin biosynthesis in Vitis vinifera ‘Cabernet Sauvignon’ berry skin

“…The PAs compositions and TTC were determined by HPLC and a spectrophotometric method, respectively. In the skin and seeds, TTC was significantly decreased at grape berry maturity, which was consistent with previous studies (Gagne et al 2006;Bucchettia et al 2011;Lorrain et al 2011;Bautista-Ortín et al 2012). EBR treatment enhanced accumulation of PAs both in the skin and seeds (Supplementary Table 3), which was fully consistent with previous results for TTC in 'Cabernet Sauvignon' and 'Yan 73' grapes (Xi et al 2013b).…”

Impact of elevated temperature and water deficit on the chemical and sensory profiles of Barossa Shiraz grapes and wines

“…Aqueous acetone (70% v/v), a common and high-yielding solvent for extraction of phenolic substances (Cheng et al 2012), was compared with a wine-like extraction medium containing 12.5% (v/v) ethanol (Bautista-Ortín et al 2012). Aqueous acetone (70% v/v), a common and high-yielding solvent for extraction of phenolic substances (Cheng et al 2012), was compared with a wine-like extraction medium containing 12.5% (v/v) ethanol (Bautista-Ortín et al 2012).…”

“…Skins and seeds from 10 frozen berries were separately extracted in 15-mL glass vials containing 10 mL of 70% v/v acetone in water (Kallithraka et al 1995) or 10 mL of hydroalcoholic solution containing 12.5% (v/v) ethanol and 2 g/L potassium hydrogen tartrate (pH 3.6) (Bautista-Ortín et al 2012). Vials were sparged with nitrogen before being sealed and incubated at 23°C in the dark on an orbital shaker (200 rpm) for 24 or 72 h for the 12.5% ethanol or 70% acetone solutions, respectively.…”

Effect of early leaf removal on Vitis Vinifera L. cv. Tempranillo seeds during ripening based on chemical and image analysis

“…The qualitative and quantitative phenolic composition of grapes depends on multiple factors, including climate, variety, soil, water availability, and degree of ripeness (Bautista-Ortín et al, 2012). Several studies have shown that phenols in seeds accumulate before the onset of ripening or veraison, reaching a maximum around veraison and decreasing towards harvest (Ferrer-Gallego et al, 2010;Kennedy et al, 2000b).…”