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Haven't been able to find a clear enough explanation for this. When it comes to fermented milk products like clabber and milk kefir, you don't seem to need to do anything other than in the first case, let it sit at room temperature in a clean jar, and in the second, do the same thing, but with kefir grains.

Yet with other foods, you need lots of salt or sugar, to keep pathogens out of the fermentation process. I know dairy and yogurt both have carbs, but I'm not getting confirmation if the amount of carbs present in them is the explanation for this.

FBHSIE
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  • Can you find an example of a liquid that requires salt or sugar to ferment ? From the examples given in the question, the former case are all solids and latter case is a liquid. – AJN Oct 09 '22 at 06:04
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    Properly handled milk has far fewer exposures to random competing bacteria than, say cabbage - though my personal milk fermenting (yogurt) also involves pasteurization before inoculation. And many fruit juices (certainly grape juice and apple cider) can generally be fermented without any additions, using the natural yeast on them (though I personally usually don't, preferring known yeast strains. Terribly boring of me.) – Ecnerwal Oct 09 '22 at 13:52
  • @AJN Lots of fermented liquids require sugar, although that sugar might already be present. Certainly yeast and lactobacilli need sugar to do their thing. – Caleb Oct 10 '22 at 23:35

1 Answers1

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With all fermentation the goal is to create an environment where tasty microbes will thrive and harmful microbes won't.

One way to do this is by changing the chemistry or temperature of the environment. Adding a lot of salt will create an environment where only salt tolerant bacteria can thrive. Luckily tasty lactobacilli can handle more salt than many nasty bacteria.

Another way to encourage tasty microbes is to make sure you start with so many more of them that they will out compete everything else by inoculating the food with the desired microbes.

The trick is to create a process with a very high chance of tasting good and not making people sick.

Milk is really nutritious stuff and microbes like it as much (if not more) than we do. Raw, unpasteurized milk comes teeming with microbes that would love to devour it. If the raw milk was very carefully handled the majority of those bacteria can be tasty and just letting the milk sit and be eaten by them might produce something good. Clabbered milk is risky. If the milk is contaminated or you are just unlucky the wrong bacteria can get the upper hand and produce something ranging from disgusting to dangerous.

Solid foods don't have the likely-to-be-beneficial microbes distributed through them like milk can. They have also existed outside for a long time so their surfaces are covered with a variety of bacteria and fungi. Just letting them decay on their own is very unlikely to taste good so their environment must be changed to encourage only the good microbes.

As Ecnerwal commented, fruit juice can sometimes be fermented on its own and hope tasty yeast will win.. but sometimes they won't. It's much less risky to force the win by killing all the microbes and just adding the kind you want.

As a side note, another fermentation method that works with grain is a sourdough starter. In this case tasty microbes will outperform bad microbes in general so to keep bad microbes from establishing colonies we regularly add fresh food. This constantly gives the tasty bacteria the upper hand.

I've never heard of heavily sugaring a food for fermentation. Sugar preserves food by making water unavailable to microbes. It works indiscriminately.

Joe M
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Sobachatina
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    Typo: you want "teeming" for the "filled with" sense of the word, not "teaming" (joining a group). Too small for a suggested edit so I could only comment. – Peter Cordes Oct 09 '22 at 19:49
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    I can think of kombucha and yeast-raising bread where *some* sugar is added (not "lots of ... sugar"). The sugar serves as food for yeast, which produces CO2 (and other species like alcohols and acids in smaller quantities), presumably thus outcompeting other microbes and creating less-ideal environments for them through these waste products. (Although with bread you don't care, as the bread is baked; and kombucha's SCOBY has its own bacteria in symbiosis with the yeast, judging by the acronym's meaning). Too much sugar will inhibit yeast through its hygroscopic action, as you rightly state. – frIT Oct 10 '22 at 11:26
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    I assume they confused fermentation with preserving and the comment about lots of sugar. As it was about meat, I assumed they were talking about treatments like lox or whatever that person who had 9lbs of wet sugar was making last week. – Joe Oct 10 '22 at 15:01