Red wines are made from the juice and skins of red grapes with the colour coming from the pigments in the skins. The main red grape varietals that are grown in Australia are:
This can be divided into three segments:
1) Regional Climate
This relates to the climatic conditions that apply to a particular region such as, for example, the Coonawarra or Hunter Valley.
The main factors being:
2) Mesoclimate
This refers to the climatic conditions that apply to a particular vineyard site within a region. This is a local variant of macroclimate that refers to the soil, vegetation or viticultural practises such as irrigation and spraying regimes.
Microclimate
This involves the climatic conditions around and within the canopy, in immediate vicinity of the vine leaves and grape bunches. It also refers to the way the vine is managed through trellising; this serves the purpose of allowing the viticulturist to arrange the vine in such a way that the leaves and fruit receive optimum sunlight.
The main climatic dangers are:
3) Soil
This is of major importance as the soil provides moisture and nutrients to the vine. The grape vine often thrives where other plants fail, but whatever the soil, good drainage is essential. In general:
Grapes - The Ripening Process
As fruit ripens, the following major events take place:
The sugar in grape is comprised mainly of glucose and fructose. The measurement of the sugar is usually done using a hydrometer and expressed in a term called "Baume." This is a useful measure as 1º Baume ultimately results in the conversion to 1% ethanol or alcohol.
The acid in grapes is mainly comprised of tartaric and malic acid, this gives the wine its fresh, crisp taste sensation. PH is an expression of the strength of the acids in the juice.
The relative ratio of each is dependent on factors such as variety, climate and soil. Cooler climates tend to give a higher malic acid content than warmer climates. Malic acid is strongly identified as green apples characteristics on the palate.
All of the above are considered when the winemaker is determining when to pick the grapes. If grapes are picked early the result will be a low alcohol, more elegant style wine with a lower intensity of colour and possibly a "green" flavour profile.
Carbonic Maceration
This is a fermentation process widely used in the Beaujolais region of Rhone Valley in France to produce light, early drinking reds. It involves whole bunches of grapes being placed in an airtight container and is used in Australia generally in conjunction with Pinot Noir. An intracellular fermentation takes place within the berry and a small amount of alcohol is produced as well as a number of highly flavoured compounds.
Wood Maturation
The major factors affecting maturation in oak are:
The most common types of oak used in wine aging is either American or French, that tends to impart certain characters on the wine. Some descriptions of oak characters include vanilla, toasty, cedar, dusty, smoky and charred. The grain of the oak will also play an important role, as a tighter grain will tend to be subtler. The completion of fermentation in oak will give better integration. Charring or toasting of the oak, either in manufacture or before sealing, will also have a role in the flavour imparted.
The larger the oak barrel, the greater the liquid to wood ratio and therefore the less oak character to be imparted. Also, new oak will give much greater oak characters than oak, which has been previously used. The main sizes of the oak barrels are:
The use of oak barrels is an expensive winemaking procedure; therefore wines matured this way tend to be more costly to buy. To overcome this cost, oak chips or pieces of oak wood can be added to the wine during either fermentation or storage. This imparts an oak aroma and flavour to the wine, but does not give it the same complexity.
Malo-Lactic Fermentation
This is a bacterial conversion of malic acid to lactic acid, which in most red wines occurs naturally. As lactic acid is a weaker acid (the acid associated with milk) the wine will appear softer. There are also flavour compounds produced during this process (eg. diacetyl which gives a buttery, smooth and creamy character to the wine).
Clarification
Clarification is the process of filtering and cold stabilising the wine. This ensures that the wine is bright and will minimise on deposits in the wine. Cold stabilisation involves chilling the wine and holding it at about minus 3ºC to separate out all or most of the tartrate crystals before bottling.
Most red wines are not filtered or cold stabilised to the same extent as white wines, therefore some red wines may produce deposits (or crust) mainly comprised of tannins, colour and tartrate crystals. These deposits are natural products and are not harmful in any way, in fact tartrate crystals are the same as cream of tartare that is used in cooking. They can easily be removed by decanting the wine prior to serving.
During the period of time from the end of fermentation to bottling, the winemaker may refine the taste of the wine by adding fining agents such as gelatine and egg white. These fining agents react with and remove phenolic compounds in the wine that would otherwise give overly bitter or course tastes. They also assist in ensuring the wine will be clear, stable and sound.
Bottling
When the winemaker decides to bottle the wine, it will be checked for clarity and stability before being filtered into the bottle. It is also important that any oak and fruit is in balance.
Red wines are usually filtered, but not to the same extent as white wines. This is because red wines contain low amounts of sugar, have normally undergone malo-lactic fermentation and have been stored for longer periods of time. What this means is that the chance of any yeast or bacterial activity occurring after bottling is very low.
