Today, most red wines are produced using a process similar to this one...
First, a vintner decides when the grapes are ripe. This is done by taste, concurrent with today's technology of taking accurate sugar readings. The grapes are then harvested and placed into a machine that removes their stems. The machine also crushes them (without pressing them) so that A) the grapes become exposed to yeast and B) the skins will color the wine. The yeast then transforms the grape's sugar into CO2, heat, and alcohol; this is fermentation. The crushed grapes and liquid then sit (macerate) until it is decided that the taste is ideal. During this process, the grape skins often float above the liquid. Since these skins must remain submerged, for best results, they are repeatedly pushed back into the liquid, or the liquid is mechanically pumped over them to continually submerge them. If the grapes sit for too long in this state, the wine will taste bitter. If they do not sit long enough, the wine will taste too weak. The vintner determines when enough time has elapsed. Once the decision has been made, the liquid is removed and the solids are sent to the press.
A mechanical press squeezes out the remaining juices in the solids. This, too, is a delicate process; pressing too firmly or too frequently produces a poor quality wine. After this, the wine needs to settle; transferring the wine from barrel to barrel after settling helps to separate/filter out solid matter and other particles that may cloud the wine. Following this, a malolactic fermentation stage is often the next step in red winemaking. Here, a wine’s malic acid is converted into CO2 and lactic acid. Basically, the process reduces a wine’s acidity by organic rather than chemical means. (Certain wines like Gewurztraminers, Reislings, Ehrenfelsers, and others that depend upon malic acid to enhance their flavors do not go through this step.)
After an aging process, the length of which is determined by the type of wine, fining and filtering processes remove sediments from the wine. The wine is then bottled carefully to avoid contact with the air. (And, as we know, many of the best bottled wines are stored for several years before they are released to us!) For more fascinating information about winemaking and wine technology, check out Vintage Cellar’s Wine Storage Education Center. There, you’ll find more tantalizing trivia and wine storage tips to think about. Cheers!