Veraison – the Onset of Ripening

At Creation the hard work and vineyard preparation for the 2015 harvest is starting to pay off, with about 50% of the Pinot Noir block having started veraison – the growth stage of the vine which sees the transition from berry growth to the onset of ripening.

Veraison is most noticeable in red grape varieties as they start to change colour from green to red. There is a less noticeable change from green to yellow in white cultivars.

This stage signals the start of sugar production and is an important indicator of the expected harvest date. Different cultivars require different numbers of heat units to reach optimal ripeness and although there is not much work to be done at this stage, the grapes are constantly monitored. Closer to harvest any underdeveloped bunches will be removed which will influence the final yield for the 2015 harvest.

This removal of underdeveloped bunches is known as ‘green harvesting’ and is key to even ripening in the remaining bunches. It influences the penetration of sunlight and the circulation of air through the bunches – all critical to the development of healthy fruit. Up until now the growth and development of the berries have been the result of cell division, powered by chlorophyll (hence the green colour of the berries). The onset of veraison indicates that chlorophyll in the berry skin is being replaced by anthocyanins in red wine grapes and carotenoids in white wine grapes. Anthocyanins contribute little to the flavour of wine; however they belong to a parent class of pigments called ‘flavonoids’ that are crucial for colour stability as well as their ability to preserve tannin in wine and thus influence the age-worthiness of the final product.

The berries start to soften as they build up sugars in a process known as ‘engustment’ and within a week of the onset of veraison, the berries begin to grow as they accumulate glucose and fructose through the water supply to the berry.

This diluting effect means that acids begin to fall. The slow, measured decline in acidity that happens in the cooler climate of the Hemel-en-Aarde means that excellent natural acidity is retained. (In very hot climates the acids evaporate rapidly during plant respiration.)

Veraison does not occur uniformly and it is typically berries and clusters that are most exposed to warmth on the outer extents of the canopy that undergo veraison first, while the more shaded berries closer to the trunk of the plant start later. There are a few tools which the viticulturist can use to control the onset of veraison: limited water stress and canopy management can increase the fruit-to-leaf ratio.

More resources are channelled to the berries (which house the seedling offspring) and thus take priority, and the implication is that the leafier the canopy and the greater the access to water, the longer veraison will be delayed. During this period the cane of the vine starts to ripen as well, changing from green and flexible to brown and hard. This needs to be taken into consideration when doing whole bunch fermentation.

Phenolic ripeness in grapes is important to quality wine production as unripe tannins in the stem, pips and skin of a grape can lead to harsh ‘green’ tannins in the finished product. The cool climate of the Hemel-en-Aarde Ridge and the wide diurnal range (the difference between the day and night- time temperatures) ensure that this process is gentle and that tannins ripen along with the rising sugar levels. Thus optimal ripeness is achieved and the acidity, sugar and tannins are all in perfect balance when Creation viticulturist and winemaker Jean-Claude Martin determines that harvest time has arrived.