Course of Oenology

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Composition of the bunch
The bunch is the fruit of the vine and it can be of different shapes and dimensions,according to the variety.
The bunch is composed of:

• The rachis or grape-stalk (the skeleton of the bunch)
• The grape

The grape is divided into:

• Skin
• Pulp
• Grape-pip

The rachis or grape stalk: is the central brunched axis,more or less woody,at the end of which the grapes grow.It contains:water,tannins,resins,etc.
The grape-stalk is almost always eliminated before the pressing of the grapes,through the rasping process,in order to avoid negative consequences to the must.

The grape: can be of several shapes and dimensions. Externally,we find the skin,which can be of various thickness and density.

The skin: its weight is on average the 10% of the total weight of the grape,and it contains fundamental elements for the production of wine;the most important are:

• Aromatic substances (terpene)
• Polyphenols (coloring substances)

The coloring substances in the white wines are the catechins,the leuco-anthocyanins and the flavonols, while in the red wines are the anthocyanins.
The skin is covered by a wax-like substance called “bloom ”. Whitish in colour,it contains micro-organisms (yeasts),which sometimes are responsible for the beginning of the alcoholic fermentation.
Having said that,we can assert that the color of the wine can be in relation with the time that the skins remain in contact with the must,during the phase called “maceration ”.

The pulp, which can be of different densities and more or less juicy,represents approximately 75-85% of the total weight of the grape.It contains water, sugars (150-300 g/l) acids,tannins,etc.
These substances are not distributed inside the grape homogenously.For this reason it is important to perform an adequate pressing in order to achieve the final results we are aiming to.

To be continued…