Basic Fermentation

• The microbes involved in fermentation multiply and grow in a vat of grapes or grape juice that contains very little oxygen. Because of the low oxygen environment, the microbes must reproduce anaerobically. During anaerobic reproduction, yeast and bacteria consume the natural sugar in the grapes, along with other nutrients such as nitrogen and produce ethanol, the chemical name for the alcohol in liquor and wine.

Proper Conditions

• Microbes produce the alcohol from grapes by consuming the sugars. Because the ethanol that the microbes produce kills the microbes over time, they may all die before consuming all the sugar in the grapes. When this happens, it leaves a sugary, juicy mess instead of premium wine or spirits. Wine and spirit-makers keep the microbes alive to consume all the sugar by keeping the grapes at the proper temperature during fermentation, not too hot and not too cold. Grape growers must also fortify the soil with the nutrients that the microbes need to keep consuming the sugar. Sometimes the grapes still don't contain the nutrients needed for the microbes to grow, and wine or spirit makers must fortify the barrel of grapes and juice with those nutrients.

Good and Bad Microbes

• Not all microbes ferment wine in a beneficial way. Too much or the wrong kind of bacteria or yeast turn the grapes to vinegar. Other contaminants cause a foul taste or can cause illness or allergies in the drinker. For this reason, some winemakers and liquor distillers find and add their own types of artificially cultivated yeasts and microbes to ferment their grapes to control the process. Others let the process happen naturally and then disinfect or otherwise clean the finished wine.

Pulling Alcohol From Wine

• After completing the fermentation process, the resulting liquid becomes wine after it's filtered. If wine isn't the end goal, the liquid can become a liquor like brandy or cognac through a process known as distillation. In distillation, the wine is heated until the alcohol evaporates off. A machine collects the alcohol that evaporated from the liquid wine. That evaporated alcohol gathers in tubes in its gas form during distillation and kept separate from the liquid wine. Once separated, it cools and becomes a liquid again. After cooling, that liquid becomes pure ethanol for use in fortified liqueurs and spirit, and the leftover wine without alcohol is either sold as de-alcoholized wine or discarded.