Date: April 2006
Why is vinegar used instead of HCL to preserve food?
Vinegar is acetic acid and is used because it is a weak acid that our bodies
can tolerate. HCl is what stomach acid is mostly composed of and is a very
strong acid. If HCl was used, then it would start to decompose the food
instead of preserve it!
There are a number of reasons:
1. Dilute vinegar (3-6% w/w acetic acid)
has a more pleasant taste than HCl (assuming it is diluted so as not to be
2. Some vinegars used in cooking come from the fermentation of
wine. This adds many subtle tastes to the food being preserved that would be
absent if HCL were used as a preservative.
3. HCl tastes too "salty".
chloride ion ([Cl](-1)] catalyzes the reaction between HCl and iron, so any
iron used in the food preservation (such as a cast iron skillet) at high
temperature is subject to faster corrosion, and traces of dissolved iron,
which tastes "funny" and discolors some foods, especially those containing
sulfur, where iron sulfide is formed (black).
5. Acetic acid is a better
buffer than HCl so it tends to have a more stable pH during storage.
Strictly as a microbicide, HCl should work well, it just has a lot of
these other issues that limit its use as a preservative. There may be some
recipes that call for HCl, but I don't know of any.
Probrably the simplest method is to tell them how the air must be
pushed aside, similar to pushing something through water. The
analogy works well enough, with the explination that water is far
heavier than air, and it is harder to move heavy things out of the way.
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Update: June 2012