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 first step in winemaking is to press the grapes, then remove what winemakers call the **pomace** – anything which isn’t grape juice. Pomace is up to a quarter of the grape’s weight, and contains a heck of a lot of chemicals (including many vitamins), fibers, fats, and proteins. The presence of these things causes a change in decomposition.
Once the winemaker has just wine juice, they add yeast. Grapes you find in the grocery store (and those you’ve done a good job of washing at home) have only trace amounts of wild yeast on them. Yeast *dramatically* changes the decomposition process, turning it into one of true fermentation, where the yeast eats the sugar in the juice and poops out alcohol. Since wild yeast is on almost every surface, there’s gonna be some on your grapes, so a little fermentation will happen, but not to the degree in winemaking.
All that alcohol that’s now floating around in the juice also has the effect of heavily suppressing bacteria growth (the same way it can be used as a wound disinfectant or mouthwash). Rotting grapes are a big ol bacteria party with lots of highly-flavorful organic chemicals floating around; wine is too alcoholic for bacteria to thrive in and is more selective about what organic chemicals are in it.
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