Question

How does fermentation occur?

Answer 1

Enzymes introduced by bacteria or microorganisms could have fermented the sugars in the juice....

Explanation:

And this is probably how wines and beers were discovered. Stored fruits, grains, or grapes underwent fermentation when exposed to microorganisms in the environment....

`C_6H_12O_6(aq) stackrel"adventitious yeast"rarr2CO_2(g)+2C_2H_5OH(aq)`

There is much technology involved in today's brewing industry, but the industry relies on the given reaction, which is performed at a cellular level by specialty yeasts. The first wines, ciders, beers, and cysers drunk by humanity were probably truly awful brews (and consumed because all the stores had fermented and gone bad, and these were the alternatives to starving...and of course after a few drafts of this rotgut, the punters began to liven up a bit).

Brewing technologies improved over the ages, and today it is a very sophisticated business. Of course, when beers and wines are REDISTILLED, we get whiskies, and brandies, i.e. liquors that were more concentrated with respect to alcohol than the parent brew. And at one time such liquor (when it was available, and clearly these were and are high-value commodities) might be the only medicine you had. It would not cure your cold or toothache, but it would make you feel better.

Brewers and vintners nevertheless still rely on anaerobic fermentation of sugars by yeasts to give carbon dioxide and alcohol. The brewing of beer is something that can be attempted in an A2 experiment, and you get very good results.....