Nature
The grape, the vine fruit
The grape seen closely
The grape is the fundamental part of the bunch, it is the fruit of the vine from which the wine is extracted. Externally it consists of the skin, not very heavy and voluminous but precious for all the substances contained. Inside there is the pulp, a succulent content that basically determines the volume and weight of the whole grape. Within the pulp itself there are the grape seeds, precious for the reproduction of the plant, but not very useful for the purpose of wine making.
In summary, from the outside to the inside, we find the skin, the pulp and the seeds. The pulp, in turn, can be divided into internal, intermediate and external.
Skin
The skin is a very important part of the grape, although it is thin and light. In fact, the substances contained in it characterize the wine in terms of color, body and organoleptic framework. On its surface is often present a thin white layer, called pruina, which has the ability to retain spontaneous yeasts (those present in the environment).
The main substances we encounter in the skin are polyphenols, mostly tannins. These are responsible for the sense of astringency, ie dryness and roughness in the front of the mouth, but also of the body and color of the wine.
Among the polyphenols we also find the pigments, that are the elements that give color to the wine. There are many of them and with funny names: anthocyanins (malvidine, peonidine, cyanidine, etc.) are responsible for purple and ruby red while flavones, leucoantocians and catechins are determinant in white wines.
The respective concentrations of polyphenols vary according to the variety, making it possible, at least theoretically, to recognize the type of grapes.
A second category of substances contained in the skin are odorous substances, which are also fundamental in defining the sensory picture of wine.
Pulp
The pulp is the most voluminous and heavy part of the grape. During the crushing phase is the one that provides the most contribution of material. The main components are water, sugars, acids, mineral salts and vitamins.
Sugars account for 15% - 30% of the weight. The main ones, glucose and fructose, are fundamental as they are the basis of alcohol formation during the fermentation phase. Other sugars, such as arabinose and xylose, are present in smaller quantities and are not determinant in alcoholic transformation.
The amount of sugars present in the grape is conditioned by the climate and the degree of ripening: warm temperatures, good sun exposure and good maturation help to form them, while cold temperatures, poor exposure or incomplete maturation will result in less sweet grapes and more unbalanced towards acidity.
The main acids are tartaric, malic, citric and acetic. Their presence provides freshness and vitality to wine but, beyond a certain limit, they may even be perceived as unpleasant.
Seeds
Grapeseeds are the seeds contained in the grape. They are essentially of woody nature and contain certain substances, called polyphenols, which may heavily affect the sensory profile of wine.
The main polyphenols contained in the grapes are tannins, responsible for a strong sense of astringency. For this reason, during the vinification process, it is attempted to perform a gentle mechanical pressing in order to avoid their breakage and to prevent their dissolution in the must.
Grape weight
The weight of the berry is given by:
- 75-85% pulp
- 10-15% skin
- 5-10% seeds
Do you know that....
The single grape berry (and before its flower) is supported by the pedicel. Each pedicel is supported by the peduncle and each peduncle by the stalk, the structure that makes up the grapes bunch.
Happy wine!
