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Grape ripening: what factors can affect its quality?

The growth and development of the reproductive organs (inflorescences, flowers and berries) and their maturation: it is the so-called reproductive cycle. Therefore, the ripening of grapes is part of the breeding cycle of the vine.


The development of the reproductive organs begins with the initiation of the inflorescences in the dormant buds the previous year and the differentiation of the flowers in spring; then the flowering develops successively, curdling, growth and ripening of berries of a cluster.

After the growth of the bunches the grapes begin to take color and the period of greening that marks the beginning of the ripening of the bunches arrives; the climatic conditions and in particular, the rain, are decisive for the quality of that year. But there’s so much more.
During the ripening period, the winegrower is practically unarmed; apart from a last treatment against gray rot and defoliation at the level of clusters, what happens in the vineyard is not absolutely controllable.

But what are the factors that can affect the quality and maturation of the grape?

Factors that may affect the quality and ripening of grapes
According to various authors they can be divided into permanent, climatological, modifiable and accidental.

Let us see a brief summary of each of them.

Permanent factors

Its action is constant from year to year without being subject to variations

The different varieties of grapes have different modes of maturation, so in their must there are differences in their composition. From the oenological point of view, acidity and particularly malic acid is the most variable majority compound from one variety to another.

Rootstocks play an important role in maturation. This communicates its vigor to the vegetative system of the plant and it is known that the most vigorous plants are the later ones, those that produce less sugary and more acidic fruits. The choice of rootstocks is according to the wine growing area and the climate, so they are contraindicated vigorous rootstocks in cold climates because these will delay the maturity and will give rise to very acidic fruits.

Plant age
It affects the vigor of the plant, influencing the precocity, so that the oldest strains are the least productive and the earliest. These strains are better adapted to the soil as they have a root system developed to the maximum, being also more resistant to drought and sudden temperature variations. Its fruits ripen the first, giving more sugary and less acidic grapes, while more colored and aromatic. On the other hand, very young vines are often harvested first because their fruits are less rich in all elements and prone to rot, giving light and less bodied wines.

In cold climates, of greater latitude, early varieties are sought that ripen quickly before the cold of autumn and that need little heat from the entry into activity until maturity, providing little acidic fruits. In these climates it is more difficult to get grapes with a balanced acidity and a sufficient color, than a sugar content suitable to make a correct wine. Therefore they are cultivated, especially white varieties, since the inks need sunny climates for the synthesis of anthocyanins and tannins. In regions of warm climates late strains are grown, third or fourth epochs, with which high yields in sugars or in harvest weight can be obtained. In temperate climates varieties of first or second epoch are used.

Climatic factors
Heat, luminosity and humidity are the three main external factors of the ripening of the grapes and are related to the weather conditions of the year. These factors are extremely variable, so it is almost impossible for two climatological years, and therefore two vintages, to be alike.

To be able to determine the necessary conditions that lead to a correct ripening of the grapes in a given region, temperature, luminosity and humidity data are necessary during many campaigns. The processing of this data and its relation to the quality of the grape harvest has allowed the establishment in areas of wine tradition of the minimum conditions necessary for a good ripening of the grapes.

In short, the character of the vintage is particularly determined by the microclimate of a given region.

Modifiable factors

The factors that can be modified are those related to the maintenance of the vineyard and the subscriber.

Pruning regulates the shape and load of the strain. It should be done after the leaf falls. The way it is done influences the production of the plant in the next vegetative cycle.

By blunting the limbs of the growing branches are eliminated, allowing a greater contribution of substances to the ripening fruit. However, studies show that the biggest difference between a blunt and a blunt strain is in the highest content of malic acid in the grapes. Therefore, blunt strains will give more acidic musts.

With the defoliation it is intended that the grapes reach maturity more quickly and avoid attacks of fungi or rot. This practice damages the yield and quality if performed during maturation due to the reduction of the photosynthesis surface. It is only allowed to peel during maturity, a few days before the harvest, for the following cases:

Accidental factors

They are due to diseases typical of the vineyard or to weather accidents such as frost or hail. As for the diseases that affect maturation, the following stand out.

The subscriber plays an important role in the quantity and quality of harvests. The strain requires fertilizer elements to be returned to maintain an adequate level in the vineyard production. An excess or a defect in the diet of the plant give rise to alterations that can affect the clusters and therefore the wine. Intensive fertilisation leads to a decrease in the colour of red wines; the wines obtained from fertilised plots are also less tannic, with less body.
Accidental factors
They are due to diseases typical of the vineyard or to weather accidents such as frost or hail. As for the diseases that affect maturation, the following stand out.

Mildew can affect the cluster at different periods of its development. If it attacks the cluster between the flowering period and fruit set, its total loss occurs, if the infection occurs after the curdling is delayed maturation with a decrease in sugars and an increase in the acidity of the grape and if the pedicel is reached by the disease the grape may not even ripen.

The oidium usually attacks the grape skin turning it a brown color stopping its development and the thickening of the grain that deforms, bursts and cleaves, sometimes showing even the seeds, However, the ripening takes place and the grapes attacked by the oidium are less juicy, they may be more sugary, but often remain more acidic than normal.

The rot is caused by the growth of different fungi or molds on the grapes at the time of maturity or even earlier, being the most common case the Botrytis cinerea. The disease spreads rapidly through the clusters and even gives rise to new problems such as the appearance of acetic bacteria. The rottenness always causes loss of color of the grapes and the wines made with this problem always present clouding and browning of the color.



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