During the “translucent” the grape is loaded with water, increases the sugar, the phenolic load and reduces the acids. The pulp increases in size and the skin becomes thinner.
Summer has begun and in the vineyard the vines begin to flower when the temperature reaches and exceeds 15ºC. If the weather helps being hot and calm, the pleasant or herbaceous period begins. A period where the future grape berries develop and lasts between 45 and 65 days, depending on the climate and type of grape. Once this process is finished, the grape begins the “veraison” or physiological maturation of the grape, which is the process in which the grapes change color one by one and mature. This period lasts about 15 days.
However, after veraison the grapes are still not suitable for consumption, it is necessary to complete another stage prior to the harvest called the “ripening period” or “translucent period”.
That is to say, this phase describes the period of development of the vine that goes from the ‘veraison’ to the ‘harvest’, or in other words from the ‘physiological maturity’ to the ‘industrial maturity’ of the grape.
It is probably the most important of the processes that occur in the vineyard during the year in terms of wine quality, since it determines the physical-chemical composition of the fruit and therefore the initial qualities of the resulting wines. It is influenced by a large number of factors, among which are: environmental (temperature, orientation, climate, diseases and pests, insolation, etc.), those related to the care of the vineyard (such as the management systems of the glass or those of conduction and pruning), the specific variety cultivated, or the style of wine that is intended to be produced.
It has a variable duration of 35 to 55 days depending on the varieties and environmental conditions, during which the grape berries continue to increase in size, mainly thanks to the dilation of their cells (aurexis), where the substances produced by the vine accumulate and which are not intended for the formation of seeds.
The skin grows to a lesser extent than the pulp, which is why there is a progressive increase in skin tension to the point of becoming translucent (hence its other name, “translucent period”), and in some cases cracks may occur. or major breaks, due to excessive growth of the pulp and sometimes induced or aggravated by diseases of the skin.
Cellular dilation is due to an accumulation of substances in the vacuoles they contain, mainly increasing water and sugars, but also mineral salts, amino acids and phenolic compounds (such as tannins and anthocyanins). On the other hand, during this stage, the concentrations of amines and acids (such as malic and tartaric) fall, increasing the pH.
However, in its final phase there is a loss of water through transpiration, which causes the concentration of sugars reaching “industrial maturity” or the moment in which the grape must be used for the industrial purposes for which it is intended. (such as the production of wines, musts or consumption).
Physiologically speaking, industrial maturity is achieved when the maximum harvest weight is obtained with the highest concentration of sugars or also when the sugar/acidity ratio is maximum.
Despite the importance of this period, winemakers frequently use other criteria, and thus maturity can be achieved when a certain balance is reached between sugars and acidity, or in the formation of varietal aromas (“aromatic maturation”), and also in certain circumstances of accumulation of polyphenols (“phenolic ripening”), a widely used guideline. In general, hot and dry climates accelerate industrial maturity compared to phenolic. The opposite usually occurs in colder and more humid climates, with fewer hours of sunshine.
They are called “ripening indices” (which we have seen in detail in Vinetur in this article) as the different methods used to determine industrial maturity, namely: general external ripening indices, sensory evaluation methods, physical ripening indices , chemical maturation indices, physiological maturation indices or mathematical models of maturation.
The set of quality parameters that can be determined in the industrial maturation of the grape before the harvest, can serve as a basis, not only to know the quality of the grape, but also to establish its price, in the case of establishing a relationship contractual between a seller and a buyer, being able to develop more or less complex mathematical formulas, with which to determine the price of the grape.
