Next comes the vintage, a critical and difficult period because each variety should be harvested at its optimum maturity, based upon the sugar and acid ration. Upon nearing maturity, the grapes must be tested repeatedly until they reach the desired ratios. The deficiency of one or the other greatly affects the final wines.
Once harvested, the grapes are delivered to the winery either in grape picking boxes or in bulk, such as in steel gondola trailers, which hold anywhere from 1 to 5 tons of grapes. Upon delivery, a gondola is raised from one side by means of a mechanical hoist, thus causing the grapes to slide and role out onto a conveyor, which, in turn, carries the grapes to the crusher.
The grapes are then crushed by means of two rollers set close together or by the more poular crusher unit, which consists of revolving paddles which "slap" the berries free of the stems, cracking them open. Regardless of type, both crush the berries and remove the stems, which are automatically expelled at the far end of the crusher. The must (crushed grapes) are pumped from the bottom of the crusher into the fermenter.
Both red grapes and white grapes are treated alike at the crusher. However, once the must leaves the crusher and is in its respective tank, they receive quite different treatment.
The clear juice from crushed whites is drained within several hours after crushing, to prevent extraction of bitter tannin and other undesirables from the skins. The rather clear juice is centrifuged to remove the small amount of grape pulp or such semi-solids that may have been retained to this point. The clear juice leaves the centrifuge and is transferred to closed fermenting tanks. Here the juice is inoculated with a definite amount of specially cultured wine yeast. This is to insure an immediate and clean fermentation, which will produce a wine of fine quality and true grape flavor. Perhaps equally important is the fact that uncontrolled fermentation would allow harmful bacteria and undesirable yeast cells (normal wild yeast on the grape skins) to develop. Such undesirables, if permitted growth, would injure the quality of the final wine.
From the time the wine juice starts to show signs of fermentation it is cooled by refrigeration. This is essential because fermentation creates heat during the conversion of the sugar in the grape to alcohol and carbon dioxide. Normally, wine yeasts will continue to ferment between 45 and 90 degrees but are destroyed above the latter temperature. The coolness is quite important as it helps to retain the fresh fruity characteristic of the grape and prevents darkening of the juice (oxidation).
Red grapes are handled quite differently from whites. They, of necessity, are fermented on the skins, the source of color, tannin and complex flavors characteristic of red wines. As in the case of whites, the reds are inoculated with a pure yeast culture, thus creating a clear fermentation without delay. Temperature control, however, is quite different. A favorable temperature for reds is 70 to 80 degrees during the fermenting period; while suited to reds, this temperature would be harmful in white or rose fermentations.
Rose or pink wine (neither white nor red) requires still another procedure. These wines are produced from selected red grapes by controlling the length of time the juice is left in contact with the skins. The pulp of red wine grapes is white. The color resides in the skins; hence, the juice of red grapes is essentially white immediately upon crushing. As the hours pass and fermentation takes over, the color is continuously absorbed by the white juice. In the case of rose, it is only a matter of hours before originally white juice has extracted enough color to become pink.
Once the desired tint is obtained, the juice is immediately drained free of the skins, centrifuged and fermented in closed tanks at the relatively cool temperature of 45 to 5 degrees F. This coolness yields a fruity fragrant rose wine.
With all wines, when the must has fermented to the desired degree, the clear juice (now called wine) is transferred to closed storage tanks, when the final stage of fermentation is completed in a matter of days. Thereafter, the wines are centrifuged to remove any yeast and other solids and stored in full containers. Later, each wine is clarified with a gentle clarifying agent, which is allowed to remain for a week or two. Thus it performs something like a screening action, pulling down most particles in suspension. Following this settling period the wines are filtered to complete the clearing up process.