Why does fermenting sugar create alcohol, but fermenting cabbage doesn’t?
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The byproduct of fermentation varies based on the organism. Some ferment sugars into alcohol while others ferment them into an acid product.
As an example, there are bacteria that love in your mouth. If you eat sugar you don’t get drunk, you get cavities. These are lactic acid producers, not alcohol producers.
A lot of answers saying cabbage doesn’t produce alcohol, but the truth is that cabbage has a small amount of sugar, and yeast will just naturally be present, so your sauerkraut will very likely have an extremely low amount of alcohol, but technically there is alcohol produced by fermenting cabbage.
Of course, could probably pasteurize cabbage, then re-inoculate with a pure lactobacillus culture, which would mean no yeast is there.
So this is coming from someone in the wine industry
So I want you to take a deep breath , in and out.
What you just did is respiration , it requires oxygen to be done and it’s a fairly straightforward thing to us , but take away the oxygen and you can’t do aerobic respiration anymore.
Now think of what the energy is our body uses , yes I know it’s ATP but what’s the main thing we use to generate more energy to make that ATP , well it’s glucose mostly or sugar. Our bodies are great at turning things into glucose when needed or storage as fat when not needed.
Aerobic respiration is a process that pretty much takes oxygen + sugar to make energy + CO2 and some other waste
Now let’s shrink this scale down to single cell scale. Cellular life also does aerobic respiration so they will consume oxygen and sugar to produce energy and those other products.
But what if they don’t have oxygen? Or more so… not enough oxygen. Well rather then just dying like we would , most single cell life can also do anaerobic respiration which doesn’t require oxygen but still takes sugar and makes energy. Now this process is more about desperation then efficiency
The problem is that unlike aerobic respiration it doesn’t go as completely or produce as much energy and it also produces different waste products. One of these waste products is ethanol which is the alcohol we drink (yes alcohol is essentially yeast cell waste)
Now here’s the thing about waste products , 9/10 they are toxic which is why they are waste products so the yeast cells in fermentation spit that stuff out into the environment. So it’s mostly purely just out of desperation to stay alive that they even do anaerobic respiration.
So now onto the second part , why can’t we ferment cabbage for alcohol? Well technically when you do make sauerkraut there is some alcohol from the process listed above but there is so little sugar in cabbage that it’s negligible , but we already determined that alcohol fermentation is like a desperation to stay alive , what if they can’t even do that effectively?
Well good thing is single cellular life is pretty adaptive and already plans for that can start breaking down even more compounds for energy but they produce even less desirable waste products like straight up producing acids.
By changing the initial conditions you can selectively choose what bacteria or yeast is alive to steer it towards doing different things , lactic acid bacteria for instance are really efficient at breaking down acids into other acids + energy (malo lactic fermentation is a specific form of this) so if you make a acidic salty environment you can selectively make the environment hostile for most other bacteria and just leave the ones happy to do the fermentation you want (although some of the other fermentation process will still always happen)
So now let’s summarize , things would rather do aerobic respiration if possible for energy , if they can’t they will do anaerobic respiration which produces alcohol as a waste product. If they can’t do that because sugar isn’t present they will then try to break down other stuff for energy.
Since cabbage has so little sugar , ethanol production just won’t happen but single cell life won’t just give up and die and still finds a way which produces the other kinds of fermentation
Just baaed on my own experience. Yeast feeds off of sugar better than most other organic compounds. To increase the percentage of alcohol you need a better food for the yeast to break down. Cabbage just doesn’t break down enough. We can get kimchi from cabbage but it’s not strong enough to produce a “good” alchohalic substance.
Think of it this way, the alcohol produced via fermentation is the byproduct of yeast metabolism, so think of the alcohol as the yeast’s poo. The byproduct of humans eating food is poop, the byproduct of yeast eating sugar is alcohol. The bacteria used to ferment cabbage is a different species and doesn’t “poop” alcohol it poops something else.
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