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Wine Making
Turning Grapes into Wine
The process of turning grapes into wine is a relatively straightforward process: producing a good end product is not so easy.
Ripe grapes contain sugar which, with the help of the yeast organisms, is turned into alcohol and carbon dioxide.
Red or White?
Winemakers have a number of decisions to make starting with, what sort of wine; grape colour and quality predetermines this to an extent. Red wine can only be made from dark skinned grapes, the flesh of grapes, red or white, is the same and produces a dull grey juice, so this means that red wines are made from both the flesh pulp and the skins; the colouring contributes to taste, flavour and the tannins which are important in promoting longevity. As most red wines tend to be dry the date of grape picking is less critical than for white wine but from the moment of picking the decisions begin.
Picking
The choice of how to pick — by hand or machine — is sometimes made for the producer.
If the vineyard is steep or awkwardly shaped or if whole bunch selection (as in choosing grapes to make some sparkling wines) is required picking by hand is the only option, but labour is getting scarce and expensive. Most vineyards use mechanical harvesters, they are cheaper and quicker; the downside is that the machines disturb the vines each year and they harvest good, bad and indifferent bunches of grapes. Only the very top flight estates (mainly in France ) say they will never use machines to harvest the grape.
When to pick is yet another element to be considered. Machine harvesters are useful in hot climates, collecting grapes at night when temperatures are lower avoiding the need for refrigeration. Once grapes are picked they are in danger of being crushed by their own weight which will cause them to lose their fresh and fruity flavours. Towards the end of the 20th century the use of shallow transport containers became more common as did the move to having crushing centres built beside vineyards.
Once the grape reaches the winery the following processes are undertaken to produce red wine in the traditional method:-
Crushed and de-stemmed; open topped fermentation vessel; pressed; into barrels (7-14 days); racking; maturation (6-24 months); fining: bottled.
Fermentation
Most grapes are crushed before fermentation to get the yeast into contact with the sugar in the grape. However the grapes for most Beaujolais wine are bathed in carbon dioxide, this forces a yeast free fermentation within the grape which mixes with the grapes at the bottom of the vat (fermenting in the normal way) producing a bright but soft wine. Traditional wine makers rely on yeasts in the air; amongst other problems this can mean waiting for the fermentation to begin. Winemakers in the new regions tend to use cultured yeasts which are more predictable. The size, material and shape of a fermentation vessel can all affect the taste of the wine. In general terms the larger the vat the more difficult it is to control the heat generated by the fermentation process which can boil off flavours. White, rose and some reds are made in vats with closed tops to avoid oxidation although there must be a valve to allow for the venting of the carbon dioxide created during fermentation. The most common material is stainless steel although some vats are of materials such as various types of plastic and stone or ceramic. Some, predominantly European, purists continue to use wooden vats (closed for white wines) and some dry white wines are fermented in oak barrels which impart the ‘oaked’ tone to the wine.
Much more could be written about fermentation; what additions can be made, warm or cool ferment and so on and if you are keen to understand more of this process there are a number of very good books available.
Air, clarity and so to the bottle.
Although oxygen can hurt white wines, full bodied reds can benefit because it encourages many of the beneficial reactions involved in barrel maturation; therefore, some producers rack from one barrel to another which can introduce the required air. Most people want wine that is crystal clear and to achieve this wines are often chilled and filtered before bottling to remove anything that may cause unpleasant smells or cloudiness. A more traditional way of clearing wine is the use of finings such as beaten egg white, this falls to the bottom of the container so that clear wine can be drawn off and bottled.