How is Red Wine Made?
Vineyard: Like most products, wine begins with the raw material. Sourcing fruit that is planted with the appropriate variety, in the right location, using the proper trellis system, and using the proper growing practices is paramount to fruit quality. Growing conditions can change due to weather, water source, and pest pressure, which can drastically change fruit quality and need to be accounted for. Lastly, the decision of when to pick is still regarded as the most important winemaking decision. When harvesting, the fruit needs to be sorted to be free of disease and rot. This can be accomplished more affectively through hand selecting in the vineyard. All of these parameters are extremely important and will influence quality.
Crush: The fruit is picked at cool temperatures and processed rapidly to ensure freshness. Whole cluster fruit is dumped into a destemmer-crusher to separate the fruit from the stems and the fruit is crushed. It is then pumped into tanks with a moderate sulfite addition. The sulfites help to inhibit bacteria that may be present on the fruit coming from the vineyard.
Fermentation: Yeast is the living organism that transforms grape juice into wine by consuming sugar and converting it to ethanol and carbon dioxide. Wild yeast is present in the air and on most surfaces. Simplistically, all that is really needed to make wine is an open container of grape juice, and time. However, wild yeasts result in fermentation starting slowly. This opens a window of opportunity for bacteria to grow and create flaws in the juice. Many, winemakers “inhibit” wild yeast and bacteria with sulfites and then inoculate with selected yeast that will ferment the juice to completion and direct the fermentation in the way they want.
Yeast strain, temperature, and juice composition all impart flavors and aroma to finished wine. Once all of the fermentable sugars have been consumed, the yeast die and settle to the bottom of the tank. The wine is drained into another tank, in a process called “racking”. The remaining skins are placed in a press where pressure is applied to extract the wine which is pumped into tanks. The solids (lees) settle to the bottom of the tank and the wine is “racked” off the lees and into barrels.
Barrel Aging: The type of barrel used is another stylistic factor in the composition of the wine. The type of oak, the region where the oak is grown, and the level of toast in the barrel are all major factors that influence the ageing and taste of the wine. These elements impart difference nuances to the wine.
Once in barrel, the wine will undergo a second fermentation (malo-lactic fermentation). This fermentation occurs with the conversion of malic acid into lactic acid by the bacteria Oenococcus oeni. This softens the wine, decreases the acidity, and provides mouth feel. The wine will rest in barrel between 6 months and two years depending upon the wine. Once wines are stable and aged, they are then blended, fined, filtered, and bottled.
Most grape juice is colorless to golden in color (even from black grapes). Wine develops its color from the skins by soaking and infusing their contents into the juice during fermentation. You can actually make white wine from black grapes by separating the juice immediately from the skins. Sparkling wine’s use of Pinot Noir grapes for Blanc de Noir is one of the more famous examples. If the skins are left in the juice for only a short period of time, the result is a rosé or blush wine such as White Zinfandel.
Although wine is comprised of just a few ingredients, it is one of the most complex liquids on the planet. Grapes primarily influence wine flavors and variety, growing conditions, and harvest date are dominant factors. Their juice is an incredibly complex matrix of hundreds of complex compounds. Winemaking practices add complexity through selection of yeast and bacteria, types of barrels, fining, and filtration which all contribute compounds that influence flavor, aroma, and mouth feel.
Tannin is a type of polyphenol in wine that is associated with a firm, mouth-drying feeling. It is extracted from the skins, seeds, and stems of the grapes and oak from barrels. Because red wines are created by leaving the juice in contact with the skins for a longer period, red wines contain more tannin than whites. However, white wines get a degree of tannin when oak barrels are used for fermentation or aging.