Wine Making / Home Wine Making
At its most basic, wine making is simply the combination of ripe grapes or grape juice with yeast. What ensues after these two ingredients are combined is a process known as fermentation. In fermentation, the yeast consumes the sugar in the grapes and produces carbon dioxide and alcohol.
While that all seems simple enough, as with anything, the devil is in the details. So let's take a step back and review the whole process of making wine from vineyard to bottle.
- Picking the grapes - Leaving out the entire process of nurturing and caring for the grapevines and grapes during the growing season, the first step in the process of making wine is the grape harvest. This is done when the grapes are at their optimal level of ripeness (which is basically the right level of sugar and acidity).
For home wine makers this step is not necessary, unless the home wine maker is lucky enough to have their own vineyard. Most home wine makers start with purchased grapes or grape juice or concentrate.
- Crushing the Grapes - The next step in the wine making process it to crush the grapes. Crushing is a process of gently squeezing the grapes to break their skins.
- Destemming - At this point the process diverges depending on whether red or white wine is being made. Red grapes are typically destemmed after crushing. In large scale commercial wineries, the process of crushing and destemming red grapes is typically done by one machine. For the home wine maker, some or most of the stems are typically removed from the crushed grapes by hand.
Grapes for making white wine are typically crushed and go directly to the pressing stage stems and all.
- Pressing the Grapes - Again, this step is different for white wine versus red wine. White wine grapes typically goes straight from the crusher to the press. There they places into the press with their stems and pressed. The stems actually help the juice to flow around the flattened grape skins. The juice from this stage moves directly into the next stage, primary fermentation.
Red Grapes are typically not pressed after crushing. Rather, the must (crushed grapes, pips, and juice) goes directly to primary fermentation. It is at the end of primary fermentation that red wine grapes are typically pressed.
- Primary Fermentation - It is in primary fermentation that yeast converts the bulk of the sugar in the grapes into alcohol. Yeast occurs naturally on grapes and it is possible to ferment wine using that yeast. Most wine makers, however, use specific strains of yeast to obtain more predictable fermentation results. This yeast is typically added to the grapes as a yeast starter. To create a yeast starter, the wine maker removes a small amount of juice and adds yeast. Once fermentation has started in the small sample, it is added back to the rest of the grape juice. A small amount of sulfur dioxide may be added prior to fermentation to kill any unwanted bacteria.
- Racking the Wine - At the end of the primary fermentation, the wine is "racked". The is a process of piping the wine from its primary fermentation containers into secondary fermentation containers. In this process, most of the lies (dead yeast) are left behind. Wine may go through several rackings prior to bottling, the wine becoming a little more clear after each one. A small amount of sulfur dioxide may be added during racking to help keep the wine free of unwanted bacteria.
- Fining and Filtering - Fining is the process of adding something to the wine to help remove any suspended solids helping to clarify the wine. Filtering accomplishes the same this using various forms of filtration to trap solids. Most home wine makers rely upon finning and racking to clarify their wine.
- Bottling the Wine - The final step is to pipe the wine into bottles. At this stage bottles are filled, corked, foil capsules are installed over the cork and the top of the bottle. and labeled. Home wine makers may dispense with the labeling and foil capsules, but they do give the final product a much more professional appearance.
The above is an overview description of the wine making process. Left out is some of the chemistry that goes along with wine making, such as measuring the level of sugar in the grapes/juice and measuring the level of sugar and alcohol to determine when primary fermentation is complete. There are many excellent books about wine making that go into this in great detail. Also left out of this description is the specific equipment that a home wine maker will need to make wine. See "Wine Making Supplies" for a list of supplies that the typical home wine maker may need.