Wine bottle labels often show beautiful images of bountiful vineyards or of feet stomping grapes, but exactly how is wine made? This question is not as simple to answer as it might seem, as modern wine making is both an art and a science. Grapes have to undergo a lengthy process from the vine to the glass in order to be transformed into a balanced, flavorful wine. Making wine involves not only work and expertise but also time for the grape juice to convert into wine. In this article we’ll look at an overview of how wine is made and what happens at each stage of the winemaking process.
During the Harvest Season
Exactly when the grapes are harvested is very important, as it determines how the wine will taste. Grapes have to be harvested at their peak of ripeness. While it can be easy to see the signs of ripeness in the appearance of the grape, ripeness for wine grapes is measured by their acid, sugar and tannin levels. The sugar content of wine grapes is measured by the degree of Brix in the grape (Brix is the percentage of sucrose in the grape). Different varietals will have an optimal Brix, with sour grapes containing a measure of 8 Brix and sweeter grapes having a Brix of 24 or higher. As grapes are converted to wine through fermentation of the sugar, a higher Brix will make a wine with more flavor and a higher alcohol content.
The Crushing and Pressing Stage
The crushing and pressing stage is exactly what is sounds like, the grapes are crushed or pressed to make juice. Depending on the type of wine to be made, the juice will either be separated immediately (free run juice) or left with the skins and seeds (must). White wine made from red grapes are separated quickly from the skins so that no color is added, rosé wines are allowed to spend some time with the skins to get some color while red wines can be left with the must.
Primary Fermentation: Once the grapes are crushed and pressed, the free run juice or the must is allowed to start primary fermentation. The wine style being made dictates how the primary fermentation goes. Yeast can be added to start the primary fermentation, or fermentation can be started naturally from yeast in the air or on the grape skins. Different types of yeast will produce different reactions (creating different flavors) in the wine. Fermentation takes 1 to 2 weeks and the sugars in the pressed grape juice are converted into alcohol (ethanol) and carbon dioxide, however, the carbon dioxide is released from the fermentation through venting.
Filtering & Malo-lactic Fermentation
After the primary fermentation, the wine is filtered, removing any sediment, skins, seeds etc…The filtered wine still has to undergo malolactic conversion.
Malolactic Conversion or Fermentation
Malo-lactic conversion or fermentation occurs after the grape sugar has been converted to alcohol. During malolactic fermentation, the malic acid in the wine is converted to lactic acid, this can be done through continued natural fermentation or by adding bacteria cultures to the wine. Malolactic fermentation gives the wine to a softer mouthfeel, less overall acidity and helps the wine develop more flavor. Malo-lactic fermentation is not typically used when making sweet wines like Muscat or Gewurztraminer, but it is standard in dry red wine and dry white wine making.
The Aging Process
After primary fermentation, filtering and malolactic fermentation, the wine may be filtered again before it is allowed to age. Aging allows the flavors in the wine to develop and can be influenced by the introduction of wood chips or oak barrels. While the wine ages, any remaining sugars are converted into carbon dioxide and alcohol, and the flavors of the wine continue to develop. Aging can last weeks, months or years.
Filtering and Blending Wine
Bottling: The Final Wine Stage
After the final filtering and blending, the wine is ready to be bottled or packaged. Some wines, like Champagne, undergo further fermentation in the bottle or they can be bottle aged or are ready for drinking.
The time it takes to go from vine to glass does not conform to any schedule. While there are general guidelines for how long it takes to go through each step, winemakers have to pay attention to what is happening to the wine and keep in mind the type of wine they want to make. Even though modern vintners can introduce yeasts and cultures to the wine and control temperature and humidity, the complex reactions between the sugars, yeasts and enzymes in the wine need to work their magic to turn grapes into wine.