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I've been wondering about a taxonomy of food preservation techniques. * Sealing (this technique seems to be a type of sealing) * Fermentation * Cooling * De

• 8fGTBjZxBcHq 6y ago
  Yeah the general theme is depriving microorganisms of something they need to thrive in the food environment. Like dehydration lowers water activity, refrigeration keeps it outside their ideal temperature range etc. Fermentation doesn't really fit with the rest under that model though. In that case you're creating a good environment for some (halotolerant lactobacillus usually) because _their_ byproducts will make it too acidic for other things to thrive. So that's fundamentally different from just trying to make it universally hostile to microorganisms. Even within a simple technique like "sealing" here it really depends on the food itself and probably local factors like seasonal humidity and temp swings. A lot of fresh foods if sealed in an airtight container can make botulism. I'm pretty informed on this subject but I don't know why that doesn't happen with the grapes here. Must just not be present on them in large amounts, or the natural yeast competes with it, or something who knows. We think of these technologies as simple because they are beyond ancient and the actions you take to use them are basic. But there is a lot going on biologically and it seems at least somewhat understudied so far.
  • hnick 6y ago
    Fermentation usually goes along with sealing too, to give the good guys a head start and avoid contamination. I've been making kefir lately and it sure feels weird putting a jar of milk in the cupboard at room temperature for a day or two.
• samatman 6y ago
  A few techniques which involve adding something to the food: * Salt * Vinegar * Alcohol
  • hinkley 6y ago
    I believe salt counts as dehydrating, although there are other forms of curing that don’t achieve the same water removal as salted meat. Vinegar and alcohol technically are fermentation, although it’s true that in some cases primary fermentation happens separately and the food is stored in the result. Pickling is sort of a grey area.
    • phonypc 6y ago
      Salting is often combined with some amount of dehyrdrating of the entire food, but e.g. wet brining meat will actually add water. Salt directly dehydrates the microbes themselves through osmotic pressure.
    • adrianmonk 6y ago
      Apparently you can also add alcohol as a preservative: https://preserveandpickle.com/preserving-fruit-alcohol/ https://preserveandpickle.com/preserving-fruit-alcohol/
    • samatman 6y ago
      I see a difference between drying something out and salting it (or sugaring it) even though both remove moisture, and a difference between fermenting something into vinegar and/or alcohol, and using those substances to preserve something directly, even though, yes, you won't have alcohol nor vinegar without fermentation. Similarities as well! This taxonomy wouldn't be a well-formed tree.
    • tharkun__ 6y ago
      Actually salt also counts as fermentation. Most people I gather know that Sauerkraut is fermented but maybe not how that works. It's basically just cabbage, cut up and stored in salt brine. The salt in the brine makes the initial environment favourable to the bacteria that create the lactic acid and all of this together crowds out all the bad bacteria and fungi. You can actually have mold swimming on top of the Sauerkraut sometimes (though some that looks like it isn't actually mold) but the mold spores can't penetrate down into the Sauerkraut, so you can actually just get rid of it and best a bit of the top of the Sauerkraut that was very close to the surface, just in case. But the rest of the Kraut will be completely fine.
• hnick 6y ago
  There are also some methods that are a little more chemistry based. Unless I'm mistaken nitrite qualifies in that it kills bacteria (mainly targeting botulinum) in a more chemically active way by inhibiting certain processes specifically.