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In viticulture, veraison (véraison, veʁɛzɔ̃) is the onset of the ripening of the grapes. The official definition of veraison is "change of color of the grape berries". Veraison represents the transition from berry growth to berry ripening, and many changes in berry development occur at veraison. Grape berries follow a double sigmoid growth curve. The initial phase of berry growth is a result of cell division and cell expansion. As berry growth of phase I slows this is termed the lag phase. The lag phase is not a physiological growth stage, but an artificial designation between the two growth periods of grape berry development. Post-veraison, fruit acidity decreases due to degradation of malic acid. The degradation of malic acid during ripening makes tartaric acid the predominant acid; grape berries also possess a small amount of citric acid. Tartaric acid accumulates early in phase I of berry growth, while malic acid accumulates at the end of phase I berry growth. At the same time as acidity decreases, hexose sugars are accumulated. The accumulation of hexose sugars (glucose, fructose) is associated with the development of xylem cell discontinuities which reduce the volume of water entering the berry relative to the volume of sugar, resulting in an increase in sugar concentration. Physiologically, the sugar concentration can increase to around 25 percent via sugar development. Further increases in sugar concentration are due to dehydration of the fruit. The deposition of sugar into the berry depends on the level of leaf photosynthesis, the number of competing sinks on the vine and sugar accumulation. As ripening continues, the fruit becomes attractive to animals due to changes in aroma from acidic to sweet with fruitiness. As ripening occurs, herbaceous aromas (e.g. methoxypyrazines) 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 because chlorophyll is broken down.

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Related concepts (6)

Ripeness in viticulture

In viticulture, ripeness is the completion of the ripening process of wine grapes on the vine which signals the beginning of harvest. What exactly constitutes ripeness will vary depending on what style of wine is being produced (sparkling, still, fortified, rosé, dessert wine, etc.) and what the winemaker and viticulturist personally believe constitutes ripeness. Once the grapes are harvested, the physical and chemical components of the grape which will influence a wine's quality are essentially set so determining the optimal moment of ripeness for harvest may be considered the most crucial decision in winemaking.

Veraison

Canopy (grape)

In viticulture, the canopy of a grapevine includes the parts of the vine visible aboveground - the trunk, cordon, stems, leaves, flowers, and fruit. The canopy plays a key role in light energy capture via photosynthesis, water use as regulated by transpiration, and microclimate of ripening grapes. Canopy management is an important aspect of viticulture due to its effect on grape yields, quality, vigor, and the prevention of grape diseases. Various viticulture problems, such as uneven grape ripening, sunburn, and frost damage, can be addressed by skillful canopy management.