Why does fermenting sugar create alcohol, but fermenting cabbage doesn’t?
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Not enough sugar in the cabbage, only things with high sugar amounts or added sugar can ferment. I believe starch can also ferment as it is lots of sugar in a chain.
Bite a cabbage. Is it sweet? No, right? You need sugar to create alcohol. Cabbages are mostly cellulose (like wood!) and water. It doesn’t have much of what is needed to create alcohol when fermented.
A big kid explanation would involve the how cellulose is a polysaccharide, and how you need a simpler sugar to get ethanol.
To piggyback on another comment, it’s because while both are carbohydrates/polysaccharides (cellulose and sucrose) the main difference is the fermentation is being done by two different organisms. Alcohol is made by a particular yeast and sour fermentation is done by a bacteria.
https://www.nature.com/scitable/topicpage/yeast-fermentation-and-the-making-of-beer-14372813/
That should answer most of your questions. Basically, various microbiota typically feed on one specific thing or another and can survive in particular environments. The yeast we use to create alcohol, typically Saccharomyces, feeds on sugar and produces alcohol. You can see it in the name, basically ‘sugar fungus’.
We typically use bacteria to ferment cabbage such as lactobacillus. So it’s a different organism entirely with a different metabolic product.
Yeast eats simple sugars first and works it’s way up, the simplest is glucose, cabbage will have some sugar but it’ll be too hard for the yeast
to nibble on
Alcohol is fermented by yeast, while sauerkraut is fermented by bacteria. Yeast is present in sauerkraut of course, but the salitity and later acidity of the ferment keeps it from dominating the conversation, so to speak.
There are different types of microbes which can be used in fermentation and they produce various different things when fermenting food. When brewing beer or other alcoholic beverages we use a yeast which produce alcohol from the sugar. You have to be vary careful during the brewing process not to get the wort contaminated with other microbes after it have been boiled as this will spoil the beer.
When fermenting cabbage we use a type of bacteria which produce lactic acid during the fermentation process. These bacteria thrive well on vegetables like cabbage. But you still want to optimise the conditions for them so they can kill off any any other types of microbes. For example if you get the temperature a bit high then the same type of yeast you can find in beer and wine might thrive instead and you do get alcoholic cabbage.
In addition to brewers yeast and lactic acid bacteria there are tons of other types of microbes which produce various other results when fermenting. Fortunately most toxic ones produce something that looks, smells and taste bad to humans.
(less about sugar itself but might be more relevant to the post)
Cabbage will contain starches which are potential sugars but cabbage itself needs an enzyme, some other foods like barley grain that have been allowed to shoot contain such enzymes that break down the starch into simple sugars, yeast loves that and gives of alcohol and CO2 as a byproduct
“Fermentation” is a broad term. It basically means using microorganisms to transform something.
In the case of wine/beer/hooch, yeast is eating sugar and pooping out alcohol.
In the case of sauerkraut, bacteria is eating sugar and pooping out lactic acid.
Fermentation is the process of taking yeast pr other bacterial organisms, havi g them eat a certain compound, and through their own bodily functions, what is produced is the fermented product.
Fermented sugar is ethanol. Where as cabbage thay becomes fermented is spawned by lactic acid producing bacteria, unlike the ethanol producing yeast thay we find in alcohol products.
Another way of looking at this is that fermentation is on the spectrum of rot. This isn’t to say that fermented products are spoiled and unfit for human consumption, but that the same processes thay contribute to natural decay are found and controlled in fermentation.
I’ve heard it said that the difference between rot and fermentation is that rot has no use for people where as fermentation does.
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