Wine is fermented grape juice. All wine begins in the vineyard, with the grapes. The grapes are picked at the point where they are ripe enough to have the right amount of sugar, balanced with the right degree of acidity (pH) and flavors.

At the core of wine making, be it professionally or at home, is the process of alcoholic fermentation, in which the sugars are converted into alcohol. However, much more happens than this simple chemical process. The grape skins contain color and flavors which come into contact with the juice once the skins are broken.

Most white wines and rosés (made from black grapes) are crushed before fermentation begins, so contact with the skins is limited. In making red wines the skins ferment along with the grapes. Often they are allowed to soak in the juice after fermentation to give the wine as much flavor and color as possible. Only then is the entire mass pressed and the skins removed.

Red wine is often aged in wooden barrels after fermentation; white wines are usually aged in steel tanks. Both types sometimes undergo a second fermentation, during which the harsher (malic) acids are converted to softer (lactic) acids. This is almost always done with red wines, and in white wines sometimes only partially or not at all.

Sparkling wines such as champagne (in which both black and white grapes are used) begin like normal white wines. The wine is fed a ‘dosage’ of extra sugar and yeast and undergoes a second fermentation. This results in more alcohol and also carbon dioxide gas, which is trapped in the bottle and gives Champagne its characteristic effervescence.

You would read in good Wine 101 guides that in fortified wines such as port, the alcoholic fermentation is interrupted by adding brandy, which kills the yeast. Since many of the sugars have not yet fermented, the result is a sweet wine.