Development of seed polyphenols in berries from Vitis vinifera L. cv. Shiraz

Abstract

Polyphenols extracted from the seeds of Vitis vinifera L. cv. Shiraz berries were monitored during berry development. Initially seeds were green, plump and had pliable seed coats, but beginning at veraison the seeds browned in colour, became desiccated and the seed coats hardened. Isolated polyphenols consisted of flavan-3-ol monomers ((+)-catechin, (-)-epicatechin and (-)-epicatechin-3-O-gallate) and procyanidins. The procyanidins were maximal in the 3 weeks prior to veraison, increasing little during this period. The amounts of flavan-3-ol monomers increased 5-fold during this same period of time, indicating that the procyanidins and the flavan-3-ol monomers accumulate at different stages. Beginning at veraison, amounts of all polyphenols declined and changed in composition. The decrease in amount followed second-order kinetics. Polyphenol changes after veraison could be explained by oxidation and therefore, electron paramagnetic resonance (EPR) spectroscopy was used to follow the potential development of radical species in the developing seeds. Spectra consistent with a phenoxyl radical were observed in the developing seeds. The concentration of radicals remained low until veraison but then increased, reaching a maximum three weeks later, declining slowly thereafter. Changes in radical intensity together with other documented changes in the seed are consistent with an oxidative event occurring during fruit ripening. Abbreviations Kennedy et al. Development of seed polyphenols 245Development of seed polyphenols

Effect of Shading on Proanthocyanidin Biosynthesis in the Grape Berry

“…This result that extractable PAs decreased after veraison agreed with reports from other groups (Kennedy et al, 2000a,b;Mateus et al, 2001). Although the mechanism whereby PAs become unextractable, as well as the mechanism of PA polymerization, has not yet been revealed, it is expected that PA oxidization and interaction with cell wall polysaccharides and other phenolics make PAs unextractable (Kennedy et al, 2000b;Pourcel et al, 2005). Downey et al (2004) investigated the effect of shading on flavonoid accumulation in 'Shiraz' berries and reported that there were significant differences in the condensed tannin content of the skins at around the veraison stage, but, in the course of commercial harvest, similar levels were observed between the shaded and exposed berries.…”

Raleio de cachos em vinhedos de altitude e qualidade do vinho da cultivar Syrah

“…Em razão da grande importância econômica atribuída aos componentes fenólicos, os quais fazem parte do vinho tinto, é importante compreender suas interações e variações, resultantes das técnicas de manejo aplicadas ao vinhedo, da maturação dos frutos e das características inerentes à cultivar (Kennedy et al, 2000). O tipo e o teor dos compostos fenólicos nas bagas podem variar em função do microclima no interior do dossel, que, por sua vez, é resultante do sistema e intensidade de podas e raleios aplicados (Beer et al, 2002).…”

“…Iniciando na virada de cor, as antocianinas acumulam-se nas bagas da uva ao mesmo tempo que há a acumulação dos açúcares. Seu declínio ocorre ao fi nal do desenvolvimento das bagas, aparentemente coincidindo com o murchamento, próximo à sobrematuração (Kennedy et al, 2000).…”

“…Práticas de manejo como o raleio de cachos podem contribuir significativamente para a sua concentração no vinho (Kennedy et al, 2000). Taninos extraíveis da película continuam constantes após a "véraison", incrementando-se até a baga alcançar o tamanho máximo.…”

“…Taninos extraíveis da película continuam constantes após a "véraison", incrementando-se até a baga alcançar o tamanho máximo. Há evidências de que os taninos modifi cam-se de acordo com a coloração vermelha e seus polissacarídeos durante o desenvolvimento da baga (Kennedy et al, 2000).…”