Changes in Tannin Composition of Syrah Grape Skins and Seeds during Fruit Ripening under Contrasting Water Conditions

Abstract

Tannin accumulation and composition were determined in skins and seeds isolated from Vitis vinifera cv. Syrah grapes submitted to contrasting water regimes under semiarid climatic conditions. Three irrigation treatments were conducted, starting at berry set through harvest of two growing seasons, 2011 and 2012: irrigation at 100% of crop evapotranspiration ETc (FI), irrigation at 50% of ETc (DI) and non-irrigated (NI). Seed total tannins did not vary with maturity but those of skins underwent a progressive decline (especially in 2011), expressed both on a fresh weight and on a per berry basis. Skin total tannin concentration and content per berry were increased under NI and DI conditions, mainly in 2012. In contrast, seed total tannins (in 2012) and flavan-3-ol monomers and tannin oligomers (both years) were higher in the fully irrigated vines (FI). Skin polymer size increased during ripening, NI and DI skins showing higher mean degree of polymerization (mDP) compared to FI at harvest. NI was also associated with a lower percentage of galloylation (%G) in skin oligomeric fraction (in 2012) and a lower percentage of prodelphinidins in the skin polymeric fraction (both years) at harvest. The mDP and %G of seed extracts did not vary during ripening and were higher in NI but only in 2012. According to the results, management of vine water status was shown to influence tannin amount and composition of Syrah grapes grown under semiarid conditions.

Chemical characteristics of grapes cv. Syrah (Vitis vinifera L.) grown in the tropical semiarid region of Brazil (Pernambuco state): influence of rootstock and harvest season

“…Bordiga et al , studying tannins during the maturation of Cabernet Sauvignon skins, found 1.2% galloylation at harvest. Kyraleou et al , evaluating the skins of the Syrah variety during maturation, found that the percentage of galloylation ranged from 4.23% to 9.51% in the oligomeric fraction and from 0.13% to 0.42% in the polymeric fraction.…”

“…The high concentrations of these compounds in the skin of Syrah grapes (IAC 313) may be related to the greater vigor of this rootstock compared to that of 1103P in the tropical climate condition of the study, which provides greater coverage of the canopy and protection of the grape clusters from the solar radiation and high temperatures. According to some studies, shading reduces the relative content of procyanidins in grapes grown under traditional conditions …”

“…Tables and show that the values of flavanols in seeds were higher than those in skins in all samples and harvesting periods. Proanthocyanidins are more sensitive to environmental factors in skins than in seeds; sunlight has been shown to affect the relative content of proanthocyanidins . High temperatures in the region may have influenced the degradation of these compounds in grape skins (Fig.…”

“…According to some studies, shading reduces the relative content of procyanidins in grapes grown under traditional conditions. 37,38 Tables 4 and 5 show that the values of flavanols in seeds were higher than those in skins in all samples and harvesting periods. Proanthocyanidins are more sensitive to environmental factors in skins than in seeds; sunlight has been shown to affect the relative content of proanthocyanidins.…”

“…Bordiga et al, 37 studying tannins during the maturation of Cabernet Sauvignon skins, found 1.2% galloylation at harvest. Kyraleou et al, 38 evaluating the skins of the Syrah variety during maturation, found that the percentage of galloylation ranged from 4.23% to 9.51% in the oligomeric fraction and from 0.13% to 0.42% in the polymeric fraction. Table 4 shows the results of the statistical analysis of the concentrations of small flavanols in seeds of Syrah grapes under tropical wileyonlinelibrary.com/jsfa For the dimers, the seeds of grapes harvested in the second period contained higher levels than those harvested in the first period.…”