I may have jumped the Wine Basics gun a bit with the discussion of red, white and rose. After all it doesn’t get more basic then “what is wine”. Wine is fermented fruit juice. Pretty generally if it is just called “wine” it is fermented grape juice. Fermentation is a biological process. Here is how it happens in wine.
Grape juice has sugar in it. Yeast, a single cell organism, “eats” the sugar and also uses oxygen to live. Sugar is made from carbon, hydrogen, and oxygen all bound together. The yeast breaks the bonds in the sugar, using the energy released in the process to live. Breaking the bonds creates new chemicals, mostly alcohol and carbon dioxide. Alcohol is also made from carbon, hydrogen, and oxygen but in smaller simpler groups. Carbon dioxide is just carbon and oxygen.
So when yeast is put together with grape juice (actually it’s hard to keep the apart) the yeast will break down the sugar into alcohol and carbon dioxide gaining energy to live and reproduce. This will keep going with more and more yeast forming and more and more alcohol and carbon dioxide being made until: 1) the sugar is all used up; 2) the carbon dioxide displaces the oxygen the yeast needs; or 3) the alcohol kills or stunts the yeast. About the most any yeast can handle is 18% alcohol. That is why you don’t find natural wines (i.e., no alcohol added) above around 18% alcohol.
When any of these conditions is met the yeast dies or goes dormant and begins to settle to the bottom of whatever the wine is in. Fermentation is done unless something happens to change the balance of sugar, alcohol and carbon dioxide. If everything went right, you have wine.
I know that was a bit on the technical side but hopefully will lay the foundation for the next “Wine Basics” which will go through how wine makers use and control the fermentation process to make wine.