In Nov. 3’s Drink column, we went back to the basics in a rudimentary discussion of how grapes become wine. We touched lightly on the topics of grape harvest, the grape “crush,” fermentation, pressing and bottling. This week, in the second of a two-part introduction to winemaking, we will dig a little deeper and go into a bit more detail about the journey grapes make to our wine glasses. If you’re already a wine geek, you probably know this stuff. Hopefully, this will be helpful to those who might be starting a love affair with wine and want to know a little more about how it gets made.
During the grape harvest, grape clusters can be picked from vines by hand (which is optimal) or by machine. Obviously, being able to select and hand pick grapes insures quality and gentle handling, but is expensive. Machine picking often treats the grapes harshly, but is economical.
Regardless of how the grapes get picked, they are put into vats and crushed into a soupy mush of skins, juice, pulp, seeds and stems for red wine. For white wine, the skins are separated from the juice before fermentation takes place. It’s the skins that color red wine and also Rosé wines. White-wine grapes require careful handling at this stage, since bruising the grapes accidentally—even on the way from the vineyard to the winery—can result in tannins leaking from the white-grape skins into the juice. This can make the wine taste coarse or bitter, and can also cause the grapes to lose essential aromas and flavors. During the crush, white-wine grapes are gently squeezed so as not to break the stems or seeds.
Wine fermentation can happen naturally, the result of ambient yeasts and natural sugars from the grapes. But naturally occurring yeasts can be tricky, so some winemakers prefer to introduce outside yeast cultures, making it easier to control the fermentation process and speed. Fermentation is really just a chemical process in which yeast converts grape sugar into alcohol. Carbon dioxide and heat are thrown off from the wine “soup,” resulting in temperatures that range from 60 to 85 degrees. The optimal range for white-wine fermentation is around 50 to 65 degrees, which means the fermentation tanks usually need to be cooled to preserve the wine’s fruitiness and delicacy. For red wines, a temperature of 75 to 85 degrees is the goal.
Once the wine has fermented, the juice is usually drained and pumped into either stainless-steel or wood barrels to continue aging, for a few months to a few years. During this time, a secondary fermentation can take place, called malolactic fermentation, which happens much more with red wines than whites. During that process, tart malic acids are converted into softer lactic acids, giving the wine a creamy texture that is associated, for example, with many Chardonnays.
Another process winemakers may employ in the late stages of aging is called fining. Fining helps to eliminate excess tannins and clarifies the wine of tiny solids suspended in the juice. Egg whites or bentonite are frequently employed to fine the wine.
Prior to bottling, a wine may also be filtered—a very controversial practice. Filtering helps to stabilize and clarify wine. However, filtering can also remove particles that are desirable and impart aromas and flavor; it’s a delicate balance. Filtering is the one topic than can bring otherwise friendly winemakers to fisticuffs.
After wines have aged in oak barrels (which impart texture, complexity, flavor and depth) or in stainless steel (which is neutral), they are bottled (by hand in tiny wineries like our local Kiler Grove; by machine in big ones), then shipped off to be purchased and sipped by wine lovers worldwide.