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What defines the outcome of the fermentation? You put the veggie, fruit in an anaerobic environment and you either get "Alcohol fermentation" (ethanol) or "Lacto fermentation" (lactic acid). What is the different input to make the different output?

I know the key difference is the saccharomyces and lactobacillus. But what decides which of them start the party?

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  • Welcome! One question per post, please - while the two are about the same substance, they are independent and should be discussed independently. Please take the tour, browse through the help center, especially How to Ask, then decide how to best edit your post. You may post two questions (but the system might insist on a short wait period). – Stephie Jul 11 at 11:10
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The factors that decide what starts the party as you say are the starter and the environment.

The yeast and bacteria are already present. If one of them is in the majority, then they'll get a head start without any intervention. It's just survival of the fittest.

But for the most part, fermenters intervene. We add starter cultures for one, and we control the sugar, salinity, and oxygen for another.

Yeast are everywhere. They love sugar and oxygen, but don't need oxygen. Yeast ferments typically start with sugar and oxygen. Lactobacilli are strictly anaerobic, and can thrive at higher salinity and acidity than yeast, so a ferment that calls for salt is often lactobacillic. Acetobacter feed on the alcohol produced by yeast but require oxygen.

So if you want alcohol, add yeast starter, sugar, and let air in at first. Then cut the air off before acetobacter start taking off.

If you want vinegar, leave your alcohol ferment open to the air.

If you want a lacto-ferment, add a starter (or not. These are easy.), salt, and no air.

That's basically it.

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  • That's an awesome thorough answer. Thank you so much! – Roo Tenshi Jul 12 at 15:51
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Alcohols exhibit rapid broad-spectrum antimicrobial activity against vegetative bacteria, fermentation is the chemical breakdown of a substance by bacteria, yeasts, or other microorganisms, typically involving effervescence and the giving off of heat.

You are not fermenting with vinegar or alcohol, you are pickling and preserving though, but you need to allow microbial activity to happen for fermentation to happen. That is in essence what fermentation is, it is allowing microbial activity to happen for some purpose.

The issue is confused because they are both done to food to preserve and prepare food.

This is an important distinction to make

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  • Oh right!!!! That's answers why I always got confused. Thanks for making that distinction. It helps a lot. – Roo Tenshi Jul 21 at 12:03

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