How is Wine Made?
There are many variations on the basic wine making technique although essentially the production of wine can be broken down into a few main stages. (For information on how Champagne is made see other related articles).
Terroir and Harvesting
Terroir is the French word for "soil," but when applied to wine in an Australian context it has a broader definition – it refers to the range of conditions that apply to the growth and ripening of grapes in a specific region - soil, elevation, slope, aspect, climate and seasonal weather patterns, etc.
Without doubt, the potential for consistently good wines is established in the vineyard; the harder and smarter the work here, the better placed the winemaker is to optimize the potential of his or her winemaking goals.
Choosing the right time to harvest a grape is the next important decision. The vineyard and winemaking team agree on a host of factors, including the flavor profile, colour, acid and tannin levels they are aiming for in their ‘end result’.
Crushing and de-stemming
Generally using machinery, grapes are removed from their stems (except in ‘bunch-fermented styles), and the skins gently crushed to release grape juices (called ‘must’).
Pressing and fermentation of white grapes
White wine grapes are then generally pumped gently through a heat-exchanger (to around 15 degrees centigrade) before being pressed – again, mostly mechanically in an air-bag or basket press, and within 24 hours of crushing
Fermentation (the conversion of sugar to alcohol) generally takes place in a tank (stainless steel or plastic); a natural process that is generally aided by the addition of yeasts carefully selected to suit best the required wine outcome. ‘Wild yeasts’ are sometimes used, these being yeasts existing in the winery atmousphere.
Fermentation and pressing of red grapes
For red grape wine making, fermentation generally precedes pressing, as the amount of contact a wine has with grape skins will affect its flavor, colour, aroma, acidity and tannin levels. In reds, this can occur in concrete, plastic or steel tanks. Maceration of red must (the process of ‘soaking’ to extract these desirable attributes) is generally more than ten days, sometimes much longer.
In wine-speak, “malo” is a fermentation option used almost universally in reds and sometimes in whites – generally shortly after the primary fermentation to add complexity and mouthfeel softness to a wine (by ‘de-souring’ or de-acidifying it)
Clarification, stabilization, maturation and fining
With fermentation complete, the yeast will die, leaving a wine still containing the yeast and other residue.
Racking is the term used where the wine is passed from one vessel to another – sometimes twice a month for many months – with the residue left at the bottom being discarded.
One of winemaking’s biggest decisions concerns the selection of a maturing vessel (particularly in reds), as between oak (and what type and how old, how big etc!), stainless steel, special plastics, a combination of some or all, etc, etc
Before bottling, the wine undergoes fining- a process of removing finer particles that may interfere with the look of the final product- generally using egg white in reds and milk powder in whites filtered.
Further mechanical filtering takes place prior to final bottling.
The decision of when to bottle (which includes an assessment of whether the chosen ‘end’ style is more suited by maturing as described above, or in bottle), what closures to use (natural or composite cork, screw cap, glass etc, etc) and when to release the wine is the final major winemaker/owner point of discussion.
In most cases, these decisions are circumscribed by winery space and equipment availability, economics, the timing of vacations (!) and so on.
The glass of fine wine in your hand is the end result of a long process involving disciplines ranging from biology, chemistry, physics and economics to logistics. Method and discipline are essential, but then so too is a temperament of experimentation and a willingness to take calculated risks. Truly a blend of science, art and economics!