Characteristics and quality of wine are directly depended on the state of grapes maturity, which will determine the day of harvest. A large number of factors influence the quality of grapes: grapes variety; technics of harvest and transportation. Grapes maturity can consist of 6 main parameters:
- Increasing of berry volume;
- Accumulation of sugar
- Drop of acidity
- Accumulation of phenolic compounds
- Synthesis of odorous molecules
- Modification of different substances: polysaccharides etc.
Factors influence the quality of grapes:
- Permanent viticulture factors: variety, rootstock, soil, age of a vineyard.
- Changeable viticulture factors: climatic factors.
- Alterable viticulture factors: density of the plantation, training system, vegetation layout, viticulture methods.
- Accidental viticulture factors: parasites, illnesses.
- Manual harvest: whole grapes, sorting of grapes, small trituration.
- Mechanic harvest: more crushed berries, less of sorting.
- Transportation of harvest
To control maturity we measure potential alcohol level and total acidity at the laboratory. Firstly we pick the berries from different parts of the parcel and cluster. Then we crush them, add sodium to the juice till it gets blue. The amount of used sodium multiplies on 0.49, so we get total acidity. The potential alcohol is measured with a refractometer. Thus we have got the next results:
- Nitrogen level
- Total acidity
- Malic acid level.
The other method to control maturity is grapes tasting. Grapes are chosen by accident. The observations are made in the next directions:
1. Tactile examination of the whole berry:
- – Crush worthiness
- – Ginning ability
2. Visual examination of skin: the colour of the berry
3. Gustatory examination of pulp:
- – Adherence between pulp and skin
- – Sweetness of pulp
- – Acidity of pulp
- – Aromas of pulp
- – The intensity of dominant aromas of the pulp
4. Gustatory examination of skin:
- – The tannic intensity of the skin
- – Acidity of skin
- – The astringency of the skin
- – Dryness of tannins
- – Aromas of the skin
- – The intensity of the dominant aromas of the skin
5. Visual examination of seed: colour
6. Gustatory examination of seed:
- – Crashworthiness
- – Aromas
- – Tannic intensity
- – Astringency.