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A common way of preserving food and organisms is immersion in alcohol. But what causes alcohol to preserve these items well?

Curt F.
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Marijn
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    As simple as it gets: bacterial life can't stand it, but we can. – Ivan Neretin Jun 27 '16 at 14:37
  • But can't bateria not just leave the alochol or do they have to interact with it? – Marijn Jun 27 '16 at 14:39
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    @IvanNeretin I'd wager that we're actually much less resistant to alcohol. And it's a matter of scale. – Mithoron Jun 27 '16 at 14:41
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    Of course it's a matter of scale; I never said it isn't. Throw a man in a tank with alcohol, and we'll see who's more resistant. – Ivan Neretin Jun 27 '16 at 14:49
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    Almost anything soluble in water will stop any kind of life if it is more than a few percent. Formaldehyde, acetone, acetaldehyde, NaCl ... – Karl Jun 27 '16 at 19:18

2 Answers2

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Alcohol kills bacteria and fungus, put simply. It does this as its metabolism products cause damage directly to the DNA, and directly to the cell respiration process. It also happens to tend to dry it out.

We can drink alcohol safely because of our alcohol dehydrogenase enzyme, which breaks the toxic alcohol into useful byproducts, that we can use for energy.

Also, it's a matter of scale. Consider submerging yourself in alcohol for a period of time. Don't you think you'd probably die, too?

It's very important to note that alcohol strength matters in this case. It also depends strongly on type. For example, ethyl alcohol: we drink this kind. It's not as toxic as say, methyl alcohol, or isopropyl alcohol. Those last ones are used as preserving and disinfecting agents, respectively.

orlando marinella
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All life on earth is adapted to work in water, and only in water. The most basic level of life is enzymes producing proteins, and energy, to produce more enzymes. Cells, DNA, etc. are the directing structure for that.

In the wrong medium, e.g. 5% ethanol, the reactivity of the enzymes is totally off, not speaking of actual toxic effects of ethanol, acetaldehyde etc. One after the other of the thousands of chemical reactions, the equillibrium of which is life, take wrong turns and go into stalemate. And that is the end of it. The enzymes are no longer regenerated, what remains are all the membranes in the cells, which you can look at in your microscope.

Karl
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    This answers the wrong question. It explains why things die in alcohol, but not why alcohol preserves anything, or why organic material is not dissolved to mush. – Agriculturist Jun 28 '16 at 22:42
  • All life stops working in 20% ethanol. Bacteria, fungus, everything is back to very slow, non-biological, chemical decay. I call that preservation. ymmv – Karl Jun 28 '16 at 23:03
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    Sheeze dude. High alcohol tolerant yeast can withstand 25% ethanol. I know plenty of people who drink beverages well over 20% alcohol. Plus several forms of chemical decay result in complete obliteration which is anything but preservation. – Agriculturist Jun 29 '16 at 03:12
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    Gotta love peer review... Its makes great answers even better. – Agriculturist Jun 29 '16 at 03:40
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    Please enlighten me: What kind of fast chemical decay could happen to organic matter around room temperature? Lets say without adding larger amounts of strong oxidants, bases, acids, OK? And I said IN, not IN SHORT CONTACT WITH with 20% alcohol. 25%, if you wish. – Karl Jun 29 '16 at 11:26
  • Pickled food 'in' alcohol can be eaten and digested. Usually people take food out of the alcohol to eat it. Your counter-argument is circular. – Agriculturist Jun 29 '16 at 14:35