Degradation of Malic acid results in a decrease of berry titratable acidity. Grapes also possess a small amount of citric acid, but Tartaric acid is another dominant acid. Tartrate accumulates early in phase I of berry growth, while Malic acid accumulates at the end of phase berry growth.
Accumulation of hexose sugars (sucrose, fructose) is associated with the development of xylem cell discontinuities. The deposition of sugar into the berry depends on the level of leaf photosynthesis, the number of competing sinks on the vine and sugar importation. Herbaceous aromas are degraded. It is unknown whether the degradation of herbaceous aromas allows fruit aromas to be detected, or if fruity aromas develop later in berry ripening.
The berry also changes in color. Presumably chlorophyll is broken down. In White cultivars carotenoids are formed, while in red cultivars anthocyanins and xanthophylls are formed. The trigger of veraison is unknown, but veraison signifies the seed reaching maturity. However, seed maturity is unlikely to cause as seedless berries also proceed through veraison.
Genome-wide transcriptional analysis of grapevine berry ripening reveals a set of genes similarly modulated during three seasons and the occurrence of an oxidative burst at veraison.(Research article)
Nov 22, 2007; Authors: Stefania Pilati ; Michele Perazzolli [1,4]; Andrea Malossini ; Alessandro Cestaro ; Lorenzo Demattè [1,3];...