The first evidence of wine comes from around eight thousand years ago in modern-day Georgia. It’s likely that the first wine drinkers didn’t mean to make it, but rather their attempts to store grape juice resulted in one of humanity’s happiest accidents. In the millennia since, we’ve domesticated grapes, refined our techniques, planted vineyards across the globe and turned wine into a beverage that is equal parts art and science.
In this guide, we’ll take a closer look at the basics of fermentation, the core ingredients needed to produce wine, and the complete wine-making process from vineyard to glass.
Despite the complex spectrum of flavours and aromas, wine needs just two ingredients: grapes and yeast.
Yeasts are a diverse range of microscopic organisms present in nature, and they are the essential partner of grapes in winemaking. There are over 1500 species of yeast, but one in particular (called saccharomyces cerevisiae) is the standard for winemaking and other alcohol production.
Grapes are the berries of the flowering plant of the same name, also known as vitis vinifera. Wine grapes differ from table grapes (the sort you eat), generally having a thicker skin and higher sugar content. More than 10,000 varieties of wine grapes exist across the world.
When yeast is added to sugar-rich grape juice under the right conditions, fermentation occurs. During fermentation, yeasts convert those sugars into ethanol and carbon dioxide, producing the alcoholic drink we know as wine.
The Australian government has set a fairly clear-cut definition of wine, describing it as “the product of the complete or partial fermentation of fresh grapes, or a mixture of that product and products derived solely from grapes.” This means that if you see a product in Australia that is labelled as wine, it must, by law, be made from grapes.
However, there are plenty of wines on the market that are made from fruits besides grapes, though these must all be clearly labelled. Blueberry wine, blackberry wine and cherry wine are common examples.
Although wine can be made with little more than grape juice and yeast, the process of producing modern wine is often much more complex. The wines of our trailblazing ancestors would likely have been low in alcohol, quick to spoil and lacking in refinement. Modern wine, on the other hand, is carefully considered at every step of the process, from where and when grapes are planted to the type of bottle the wine ends up in. Qualities like specific flavours and aromas, alcohol content and longevity can all be controlled by skilled winemakers.
There are two key roles in the production of wine: that of the winemaker, and that of the viticulturist. Viticulturists are experts in the vineyard, understanding how factors like climate, soil types and elevation can affect the end result.
Wine grapes are heavily seasonal, with a full growing cycle occurring across the year (known as the ‘vintage’). As the grapes grow across the year, viticulturists work hard to maintain the health of the vineyard through irrigation, vine maintenance and monitoring for disease.
By the end of summer and into early autumn, grapes will be reaching their peak ripeness. Each winemaker will be shooting for something in particular to produce the style of wine they want. Grapes left to ripen more fully can end up as wines that are very fruity and high in alcohol, while those that are less ripe can be more acidic. Even the time of day or the weather during harvest can affect the final wine.
These days, qualities such as ripeness can be measured scientifically. Winemakers and viticulturists will use a tool called a refractometer to measure sugar content, while they’ll also pay attention to pH to determine a grape’s acidity. Once they’re happy, grapes are harvested either by hand or using specialised machinery.
Before fermentation can begin, winemakers need to extract the grape juice. It’s an important consideration, because the method used and the pressure exerted on the grapes can have a big impact on the flavour of the final wine.
A soft crush will result in a lower yield while producing a fruitier flavour with less tannin. A harder crush will result in a high yield but a much higher level of tannin. The softest crush comes from nothing more than the weight of the grapes themselves (known as ‘free run’), while industrial machinery is able to produce significant pressure.
Once the juice is extracted, it is transferred to a vessel to start the fermentation process. While fermentation can begin spontaneously due to naturally-present yeast, modern winemaking tends to be more controlled, with yeast added intentionally. When fermenting, the yeast converts the sugars in the grape juice into ethanol and carbon dioxide. Fermentation needs to take place at specific temperatures (around 20-30 degrees C for red wine, less than 15 C for white) in order to achieve desired flavours.
If the wine has been fermenting with its skins - as is generally the case for red wine - it is then removed to a wine press to separate the solids and liquids before the next stage.
Some wines - often white, but occasionally red - are ready to be bottled after fermentation. Many wines, though, continue to improve with maturation before bottling. Time spent in oak barrels can add further flavours and complexity to wine, imparting the creamy character of the oak while allowing some oxygen to access the wine. Stainless steel is neutral and airtight, generally prized for its ability to preserve the wine’s freshness during maturation.
The final stage of wine (before it makes it to your glass) is bottling.
Wine is a living thing, and once it goes into the bottle, it will continue to develop. Tradition often dictates the shape of a wine bottle, too, so you’ll often see pinot noir in one style, while riesling will have another.
Ultimately, the best way to understand the practical differences in winemaking styles and techniques is to explore for yourself. At De Bortoli, we produce a wide selection of highly awarded wines from premium vineyards across Australia. Shop our range today.
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