FACTORS THAT INFLUENCE THE QUALITY OF WINE_
1. CLIMATE, MICRO-CLIMATE & BIO-CLIMATE
The grapes will provide juice of
the quality necessary for conversion into a drinkable wine where two climatic
conditions prevail:
* Enough
sun to ripen the grape and
* The
winter is moderate, yet cool enough to give the vine a chance to rest and
restore its strength for the growing and fruiting season
This shows that the grapes and hence the vine needs a good
balance of heat, cold and moisture. Temperature should average 14 - 16°C.
The lowest annual average temperature necessary for the vine to flourish is 10°C. It
is estimated that the vine needs about 27 inches of rain per year mainly in
winter and spring and at least 1400 hours of sunshine.
Micro-climate: A particular beneficial weather
pattern prevailing in a single vineyard or a group of vineyards or within a
small region is called a micro-climate. It could be hills or mountains
protecting the vines from heavy winds, or even a break in the mountain range
allowing the air to freshen and fan the vines in very hot weather. It could be the
angle of the sun, especially the clear brilliant morning sun that strikes one vineyard more favourably than another. The rise and
fall of the terrain also has an effect, as also the location besides water body
for ground moisture and reflected heat. These subtle differences in atmospheric
conditions, combined with the quality of the soil and the grape variety used, are
the reasons why some vineyards have such outstanding reputations.
Bio-climate: The
relationship of soil and climate in a specific vineyard is called its
bio-climate. Knowledge about bio-climate is
used to obtain stable yields of high-quality grapes.
2. ASPECT
Vineyards
are ideally planted on south-facing slopes (particularly in the northern
hemisphere) where they point the sun and benefit
from maximum sunshine and good drainage. Setting is of prime importance to capture
the sunlight for photosynthesis and good ripening. Some vineyards are sited at
a height of 243 m or more on mountain sides,
while many of the great vineyards are located in river valleys and along
lake sides benefiting from humidity and reflected heat.
3. Nature of SOIL
Vineyards
thrive where other crops struggle. Poor soils rich in minerals are best for the
vine as they provide nutrients such as phosphate, iron, potassium, magnesium
and calcium. These minerals and nutrients contribute to the final taste of the
wine. Favored soils are chalk, limestone, slate, sand, gravel, pebbles, clay,
alluvial and volcanic. These soils have a good drainage and moisture retention
capability to keep the vine roots healthy. Soil is analyzed annually and any
chemical deficiency is compensated for. Drainage is very important, as the vine
does not like having wet feet.
4. VINE FAMILY, COMPOSITION OF VINE AND GRAPE SPECIES
Vine:
The plant, which bears the grape, is called a Vine. The vine
belongs to the Ampelidaceae family. This family has around 10 genera but
only genus Vitis is important for making wines. This genus has a
subgenus known as Euvites and this subgenus has around 60 species. Some
of these species are Vinifera, Labbrusca, Riparia, Rupestris, Berlandieri
etc. Thus, there are five family of species: Vitis Vinifera, Vitis
Lambrusca, Vitis Riparia, Vitis Rupestris, Vitis Berlandieri whose noble
grapes can be used for producing classic wines. The plant Vitis Viniffera
produces grapes, which are used for the production of best quality wines
throughout the world, with few exceptions. These are in the east coast of America and Canada where other species are
cultivated because they are more suited to the terrain and climatic conditions.
Thus, Vine family is one of the important factors that influence the quality of
wine.
Composition
of vine: The vine consists of:
Roots:
These are for anchorage and for absorbing nutrients and moisture
from the earth. The root system is large and can reach to a depth of about 12
metres.
Leaves:
When sunlight falls on leaves that have chlorophyll, carbon
dioxide is absorbed from the atmosphere and combines with water, absorbed
through roots, to make sugar. The sap stores this sugar within the grape.
Leaves also shade the grapes in very hot climate. Flowers: Vine flowers
are very small and self-pollinate between May to June in the northern
hemisphere and from November to December in the southern hemisphere. Flowering
lasts for about ten days. If frost arrives during the flowering, unprotected vines
will not bear grapes.
Grapes:
After pollination, grapes are formed which are small, hard and
green initially but swell out and change colour as they ripen in August and
September. They are usually fully ripe 100 days after flowering. A ton of
grapes produces 675 litres, equivalent to 960 bottles of wine.
Grape:
The grape must be in harmony with the soil, the location of the vineyard and
local climatic conditions. It should be
disease resistant, give a good yield and produce the best quality wine possible.
Wine is produced from either varietal grapes, which is a classic single grape like Riesling or from hybrids,
which are a cross such as Riesling X Silvaner = Miiller -Thurgau. Grapes behave
differently in different soils. Hence,
Pinot Noir is a classic in Burgundy and a
disaster in Bordeaux.
5. GRAPE
The grape is made up of stalk, skin, pips and pulp and its
respective roles are as follows:
Stalk: The stalk imparts tannic acid
to wine. It is mostly used in the making
of big, flavoursome heavy bodied red wine and is not used when making white and
light bodied wines. Tannin acts as a
preservative and antioxidant. If over-used,
it makes the wine astringent and nasty. It is recognized on the palate by its tongue-furring properties.
Skin: The outer skin or cuticle has a
whitish cloudy coat called bloom. This waxy substance contains wild yeasts and wine yeasts, which contribute to the fermentation
process. It also contains other microorganisms such as bacteria acetobacter that is a
potential danger to wine. If uncontrolled, it turns wine into vinegar. The
inside of the skin imparts colour that is extracted during fermentation.
Pips: Crushed pips impart tannic acid, oils
and water. They do not contribute to vinification, if left uncrushed.
Pulp: The flesh of the grape provides the
juice called must, which is essential for fermentation. The must
contains 78-80% water; 10-25% sugar and 5-6% acids. Water makes up the bulk.
Sugar is formed in the
grape by sunlight and is of two kinds: grape sugar (dextrose and glucose) and fruit juice (levulose and fructose). They are found in about equal quantities. Tartaric, malic, tannic and
citric acids in the must help to preserve and keep the wine fresh and
brilliant. It gives it a proper balance. Esters are formed when the acids come
in contact with alcohol and it gives the wine its aroma or bouquet. The must (unfermented grape
juice) also has trace elements of nitrogeneous compounds such as albumen,
peptones, amides, ammonium salts and nitrates, as well as potassium, phosphoric
acid and calcium, all of which have an influence on the eventual taste of the wine
6. VITICULTURE
Viticulture denotes the
method of cultivation of vine. An overworked vineyard without compensatory
treatment or a neglected vineyard will only produce second-rate wine, so the farming of the vineyard is of great
importance. It involves:
- Vine selection;
- keeping the vineyard healthy;
- ploughing to aerate the soil;
- weeding;
- fertilising;
- pruning to regulate quality;
- training the vines;
- spraying to combat diseases;
- harvesting.
7. VINIFICATION
Vinification encompasses the methods
of making wine.
This includes:
- the pressing of the grapes
- the treatment and fermentation of the must
- ageing & maturing the wine and occasionally topping it up to keep the air out
- racking, fining and filtration to make the wine star bright:
Racking is running the clear wine off its lees or sediment
from one cask to another. Fining is further clarification of wine usually before bottling. A fining
agent such as isinglass, bentonite clay etc is added and this attracts the
sediment suspended in the wine, causing it to coagulate and fall to the bottom of the container. Filtration is the
final clarification before bottling. It removes any remaining suspended matter and leaves the wine
healthy and star bright in appearance.
- blending - compensatory
- bottling for further maturing or for sale.