What is wine?
Essentially, it is fermented grape juice, but with a few extra twists. God saved a few pieces of Eden when he gave us the boot, and one of the best is the fact that any fruit containing sugar will turn to booze if you leave it to ferment. In the process of fermentation, yeast converts the sugar into alcohol. Yeast is found all over the place, and in the wild it lands on the skins of grapes; hence, when grape juice is left to sit about in the wild, that yeast will mix with it and ferment it naturally. Vintners nowadays don`t take any such chances: they labor over what precise strain of yeast to use in their recipe because different choices will obviously lead to different results.
Most people believe that green grapes make white wine and red grapes make red wine. That is largely true, but if you care to impress anyone with arcane eno-trivia, you should know that white wine can also be made from red grapes. The inside of red grapes is essentially "white" - it is only their skin that is red. And most wines are made with just the inside of a grape. The red color in red wine is created by allowing the fleshy interior to mix with the pulpy skins when it is being crushed. This process infuses red wines with "tannin," an ingredient that gives red wine its distinctive flavor. So you can make white wine with red grapes - like White Zinfandel, a fine white wine made from a grape with a decidedly red exterior - but not red wine with green grapes. Oh, and most champagnes are made from red grapes. Weird, but true.
The grapes are crushed with or without the skins and then left to ferment. The nasty bits are removed from the juice and a disinfectant is used to neutralize any contaminants, such as mold and bacteria, that may have been on the grapes - remember, they`ve just been sitting outside for ages, surrounded by bugs and dirt, and yeast ain`t the only thing lurking on the skin. The fluid, or "must," is then left to complete the fermentation process in either big steel vats or small wooden barrels - barrels call for a longer process and are harder to keep at the right temperature, but supposedly lead to a better finished product, for which you of course will end up paying more. Once the wine is properly fermented, the vintner will need to pluck out all the little nibblets and then mature the clarified vino. The better vineyards will age the wine for years in oak barrels, which infuses the wine with positive woody hints. The lamer vineyards will shove the stuff in a steel vat just long enough for it to be squirted into cardboard boxes with plastic spigots.