Wine has been produced for centuries in many parts of the world. Today, the grape vine is cultivated for wine production in more locations and conditions than at any other time in history. The variables involved in winemaking are numerous. They have now been researched and refined to a very high level. Despite many innovations from science, there are some universal principles of winemaking that are the same today as they were centuries ago.

Checklist

• Following harvest, grapes are taken to the winery where they are de-stemmed, crushed and pressed.
• Grape juice for red wine is generally fermented with the skins and then pressed to separate the skins from the wine.
• Grape juice for white wine is usually separated from the skins before fermentation.
• Fermentation is the conversion of sugar, released from the grape juice in the form of glucose and fructose, to alcohol.
• Yeast (either indigenous or selected) convert the sugar in grapes; producing aroma and flavour compounds, alcohol, gas (carbon dioxide) and heat – selection of yeasts will influence the style and finished character of a wine.
• Yeast lees (sediment), are separated from the wine after fermentation in a process known as racking.
• Wine made in a traditional manner is often bottled without fining or filtration. Commercial wines utilize fining and filtration methods.
• Once bottled each wine continues to change and evolve, a process referred to as bottle-ageing.
• Each and every wine exported from Australia is examined by an expert panel to ensure quality standards are always maintained.
  

Breaking it Down

Following harvest, grapes are taken to the winery where they are de-stemmed, crushed and pressed.  Depending on wine style, different techniques are employed to manage the amount of contact between grape skins, flesh and juice.  Skin contact is essential for colour in red winemaking The grape juice is fermented with the skins and then pressed to separate the skins from the wine. Very few white wines benefit from a period of skin contact before fermentation.

Fermentation:
Every wine relies on fermentation, which involves the conversion of sugar, released from the grape juice in the form of glucose and fructose, to alcohol.  Yeast act as the agents of fermentation by processing the natural grape sugars, thereby producing aroma and flavour compounds, alcohol, gas (carbon dioxide) and heat. Two types (or strains) of yeast are vital for fermentation. These strains are resistant to alcohol, allowing all sugar to be processed, producing dry finished wine. These two strains are saccharomyces cerevisiaeand saccharomyces bayanus.

Some winemakers select pre-prepared dried yeasts - others prefer to rely on naturally occurring yeasts found on grape skins and in the winery for fermentation. Selected dried yeasts in packet form allow winemakers to match certain yeasts with certain grape varieties in order to pursue a desired wine style. Yeasts found on grape skins and in wineries are variously referred to as ambient yeast, natural yeast or indigenous yeast. Although the simple act of fermentation is the same, the choice of yeast can have a significant impact on the character of the finished wine.

The control of heat produced during fermentation through temperature-controlled tanks is one of the most significant advances of modern winemaking. This has enabled the winemaker to have a more regulated environment within which to direct the duration and intensity of fermentation. The size and type of fermentation vessel is also important. This will determine the volume to surface area ratio of the fermenting wine and therefore the influence the holding vessel (tank or barrel) may have on the finished wine. This ratio will influence factors such as tannin development, imparting oak influence, rate of colour extraction etc.  Sizes of holding vessels range from small buckets to large tanks holding millions of litres. These fermentation vessels can be variously made of oak, concrete (lined or not), stone such as slate, glass, clay (amphorae), synthetics (plastics) or stainless steel.

Cleaning Up:
Following the fermentation process, when all the sugar has been converted to alcohol, the yeast cells die. These dead yeast cells, or lees, are removed from the liquid in a process known as racking. As mentioned earlier, red wines need to be separated from the skins following fermentation by pressing.

Locking it Down:
Once fermentation is finished and the wines have been separated from the lees, the wines can be prepared for bottling. Some wines are bottled very soon after fermentation and others are matured for a period of time, usually in oak barrels.  With commercial supply pressures, wines made in industrial quantities often use fining agents and filtration to ensure the finished wine is clear before bottling. Alternatively, with the benefit of time, care and attention the wine can naturally settle clear, and is often bottled without fining or filtration.

Once the wine is clear, winemakers need to make sure the wine is in a stable condition prior to bottling. Various processes are available to stabilise a wine ensuring that yeast activity will not continue in the bottle and ensuring that undesirable changes do not occur. Sulphur dioxide is added to the vast majority of wines post-fermentation to ensure that the wine is stable and will not undergo further fermentation (known as secondary fermentation).

Sealing the Deal
Bottling is an important part of the winemaking process and precision is the key. A lot of hard work and careful winemaking can all be compromised at the point of bottling. Immediately before bottling many wines are subjected to a laboratory analysis to ensure the wine is ready for bottling.  Once in bottle the winemaking process has finished but each wine continues to change and evolve. This process is known as bottle-aging.

Stonier, Mornington Peninsula, Victoria:

“We try to manage our different sites, not to get a sameness of fruit, but to get the best balanced fruit coming into the winery. Then, every attempt is made with the winemaking to preserve the balance and difference of each vineyard. The best demonstration we have of this is the two single vineyard Pinot Noir wines we make - the KBS vineyard and Windmill vineyard.

“Both are planted with the same Pinot clone on the same soil, with yields restricted to similar levels, but the KBS vineyard has a cool easterly aspect and the Windmill vineyard, which is slightly higher in elevation, has a warm northerly aspect.

“In 2003 we did our first trial of whole bunch fermentation in the Windmill Pinot. The depth of fruit and abundant ripe tannin seemed a perfect match for the more traditional Burgundian techniques - our hope was to get a wine that combined complexity, delicacy and structure for ageing. Using the tannins from the vineyard - stems as well as seeds and skins - seemed a far better way of achieving this than relying on oak tannins or cold soaking for example.

“The KBS vineyard, with its fragrance, freshness and silkiness, is made to accentuate its own vineyard characters. Totally destemmed, it is fermented in small open tanks, plunged twice a day by hand, and usually spends around 12 days on skins to allow the integration of the tannins. So with both wines, we have observed vineyard characters that we've tried to maintain or highlight with winemaking techniques.”