Have you ever eaten a grape that was almost rotten on the inside but tasted like a good wine? Or smelled a bag of old grapes and it had that same aroma?
What exactly happens during winemaking to create ‘alcohol’ rather than rotten fruit?
In: Biology
The simplified explanation is that there are competing micro organisms. There are molds, yeasts and bacteria etc. and each of these are, in turn, broken down into different types/species. Making wine, beer, cheese, bread, yogurt etc requires making conditions that the “right” kind of microorganism does most of the work that results in “fermentation” rather than what we would term rotting or spoiling.
In bread, wine, beer – yeast is the thing you want mostly. (Sourdough is a mix of yeast and bacterial action). Done correctly, the high yeast concentration inhibits the growth of the non-wanted bacteria and molds while producing the alcohol and/or carbon dioxide. Mess it up and the product spoils rather than ferments.
Yeast normally consumes oxygen, sugar and starch and produces CO2 and water. However when there is insufficient oxygen, yeast uses a different reaction and produces alcohol and CO2 instead. The key is to restrict the oxygen which is why the wine is kept in mostly sealed vessels.
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