Wineries make red wine today much the same way they did 6,000 years ago in Georgia, Greece and Persia. Dark-colored grapes are harvested, crushed, fermented, stirred and separated from the skins by a press. Voila! Red wine.
Better containers, presses and cellars have increased quality and efficiency of red wine production many times over, but
it’s still essentially a simple process. Red wine production requires no cooking or ingredients besides grapes, yeast and, usually, sulfur dioxide as a preservative.
Red wine is made like white wine, but with one major difference. Generally, it ferments with the grape skins and juice combined in a tank or vat. White wines are pressed before fermentation, separating the juice from the skins.
The skin contact in red wine production allows color, flavor and textural compounds to be integrated into the juice, while the yeast converts sugar to alcohol. The skins contain most of the good stuff that gives red wine its color, while the pulp mostly provides the juice.
Red wine grapes are ready to harvest in late summer to early fall, several weeks after the initial green color of the grapes has turned to dark red or blue-black, a period called veraison.
Vineyard crews cut the grape bunches or clusters from the vines. That’s either done by hand or a self-propelled machine that shakes or slaps the grapes off their stems and collects the individual berries and juice.
Delivered to the winery, winemakers can also sort out mildewed grapes, unwanted raisins, leaves and debris. Clusters then go through a destemmer/crusher that removes the whole grape berries from the stems and may squeeze them slightly to get the juice flowing. Any juice created at these stages prior to pressing is known as free run. Machine-harvested grapes are already ready to ferment.
The combined juice, skins and seeds is known as must. Some winemakers cool the must for a day or two, a process called cold soaking, to extract color and flavor compounds from the skins before any alcohol is created.
After this, some winemakers add commercial yeast to begin fermentation while others let the native yeast that clings to the grapes or exists in the cellar’s atmosphere start the fermentation. Either way, yeast cells come to life in the sweet solution and begin to convert the sugar into alcohol, heat and carbon dioxide.
A cap of skins forms atop the must. This cap needs to be blended back into the juice at least once per day but often more during the fermentation process to keep it moist.
This process releases carbon dioxide, allows oxygen uptake, speeds extraction from the skins and manages the heat, which can exceed 100ºF if not monitored.
Winemakers stir the must or wet the cap by different methods. The juice can be pumped over the cap, the cap can be punched down, or the juice can be drawn off the solids and used to re-soak them (rack-and-return).
Winemakers transfer the must into wine presses, which separate the skins and seeds from the wine and squeezes the skins to coax out what is known as pressed wine.
How hard to press the must is a key winemaking decision. Too hard, and it brings out harsh tannins. Too soft, it might leave the wine lighter in color and texture.
