Veraison: grapes in full colour

Malta’s vineyards are spattered with brightly-coloured dots in new shades of yellow and red hues peeping through leafy vine canopies ready to have their ripe crop picked.

The vivid transformation from small green berries to fully-coloured grapes known as veraison (and pronounced ‘VEH-ray-zoh’) has come to an end. Adopted into English use, veraison is originally a French viticultural term meaning ‘the onset of grape ripening’ and heralds harvest time.

Although stunningly dramatic, veraison is only a short, intermediate stage when the skins of young, immature grapes, rapidly start to take on their final colour.

Characterised by an extraordinary kaleidoscopic palette of tints in the vineyard, it refers to those few weeks when vines show bunches part green and part yellow or red, depending on the variety. At first, the colour of all grapes is bright green due to the presence of green chlorophyll in their skin but it changes rapidly as chlorophyll is replaced by other organic pigments such as carotenoids in white varieties or anthocyanins in red grapes.

As the skin becomes more transparent, the colour of white wine grapes will turn from green to a yellowish green or even golden yellow. In red grapes, the transition is visually more noticeable since the berry skins go from a similar green colour to a bright ruby, deepening to a dark black cherry hue.

The final depth and exact shade will depend on the variety itself. For example, grape varieties such as Cabernet Sauvignon, Syrah and Merlot will be almost black whereas grapes such as Ġellewża, Grenache
and Sangiovese will be lighter and redder or purple in comparison.

Veraison does not happen uniformly among all berries, nor indeed within the same bunch. Typically, the berries and clusters that are most exposed to the most warmth, on the outer extents of the
leaf canopy, undergo veraison first, whereas the berries and clusters closer to the trunk and under the canopy shade itself will experience it last.

But the change in the colour of the grapes is only part of the story. Other important changes in grape development occur also.

After about six days, the cell walls become more elastic and swell. The berries grow to about twice their size and start to soften. The summer months offer the vines an abundance of long days and bright sunshine which creates energy, resulting in amounts of grape sugars. Glucose and fructose begin to be deposited inside the berries while sour acids get broken down as the grapes mature. Berries change
from being very tart, herbaceous and acidic to tasting more fruity and complex.

At this time, the vegetation is lush and the green leaves are at the peak of their life strength; they can synthesise all the necessary nutrients for optimal ripening of the grapes. The most relevant agricultural operations in this period are leaf removal, thinning and selection of the finest grape bunches for this year’s vintage.

This article by Georges Meekers appeared first in the Times of Malta, 5th August 2016

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