Winemaking
Winemaking or Vinification is the process of wine production. This process follows the selecting of the grapes through to the bottling of the finished wine.
Quality of the grapes is not only determined by the variety but also by the weather during the growing season, the soil, the time of harvest and the pruning style.
Grapes in Australia are usually harvested from February to April, this being quite different from one region to the next. Harvesting is picking the grapes, and the first step in wine production. Grapes are either harvested by hand or mechanically. When to harvest the grapes is usually decided by the winemaker when the grapes have the correct level of sugar, acid and pH level. Mechanical pickers are large machines that are quicker and require less labor, but run the risk of picking rotten or diseased grapes, non-grape matter and bird nests or grapes that aren’t ripe yet. The chances of a contaminated wine tank are much higher when using Mechanical pickers. Picking by hand is generally expensive because of the labor it requires, but the advantage is that knowledgeable labourers will only pick grape clusters that are ripe, distinguishing between unripe clusters and diseased grapes.
Wine production can be generally classified into two categories: still wine (without carbonation) and sparkling wine (with carbonation).
After the harvest, the grapes are crushed and allowed to ferment. Red wine is made from the must (pulp) of red or black grapes that go through fermentation together with the grape skins, while white wine is usually made by fermenting juice pressed from white grapes, but can also be made from must extracted from red grapes with minimal contact with the grapes’ skins. Rose wines are made from red grapes where the juice is permitted to stay in contact with the dark skins long enough to pick up a pinkish colour, but little of the tannins contained in the skins.
During this primary fermentation, which generally takes between one and two weeks, yeast converts most of the sugars in the grape juice into ethanol (alcohol). After the primary fermentation, the liquid is relocated to vessels for the secondary fermentation. Here, the left over sugars are slowly converted into alcohol and the wine becomes clear. Some wine is then permitted to age in oak barrels before bottling, which add additional aromas to the wine, while others are bottled directly.
With Sparkling wines such as Champagne, an additional fermentation takes place inside the bottle, entrapping carbon dioxide and generating the characteristic bubbles.
Sweet wines are made by ensuring that some left over sugar remains after fermentation is completed. This can be done by harvesting late (late harvest wine), freezing the grapes to concentrate the sugar (ice wine), or adding a substance to destroy the remaining yeast before fermentation is completed, for example, high proof brandy is added when making port wine. The wine maker may also decide to hold back some of the sweet grape juice and add it to the wine after the fermentation is done.
Whether the wine is ageing in barrels or tanks, tests are run regularly in a laboratory to check the status of the wine. In response to the results, the winemaker can decide if the wine needs adjustments before bottling.
The winemaker is also in charge of Blending, fining and preserving the wine. Today these duties require an increasing amount of scientific knowledge as laboratory tests are replacing traditional methods. So many winemakers now have or are studying for a Bachelor of Science degree, majoring in Oenology – the science of wine.
