SC - Re: SALT (fwd)

[Laura C Minnick]

	#2 of 3

'Lainie
- -
Laura C. Minnick
- -
'A Vaillans Coeurs Riens Impossible'
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"Libraries have been the death of many great men, particularly the
Bodleian."
	Humfrey Wanley, c. 1731

- ---------- Forwarded message ----------
Date: Sun, 25 Jul 1999 01:55:02 EDT
From: Michelle Ziegler <MichelleZi at AOL.COM>
Reply-To: ANSAXNET Discussion Forum <ANSAX-L at WVNVM.WVNET.EDU>
To: ANSAX-L at WVNVM.WVNET.EDU
Subject: Re: SALT

In a message dated 7/24/99 6:08:46 PM, 73071.327 at COMPUSERVE.COM writes:

>You've provided scientifically specific detail that at this hour I
>was not capable of expressing appropriately.  I spent two hours today giving
a talk >to 30 people with this aim in mind.  One asked me 'why does salt
preserve' -- no one >has asked me that before.  But as you say, dehydration
(removal of moisture from >the food) is the answer, otherwise bacteria
thrive.  Presumably dehrydrtion >increases salinity, and the salinity kills
the bacteria ?
>
>     Bea

Not quite, let me clarify.  The salt will dehydrate the food being preserved
but that is not the main reason bacteria stop growing. The high solute
concentration (the salt on the food) causes water to actually leave the
bacteria's cell and go into the environment. The bacteria itself dehydrates!
It is essentially like a human bleeding to death.

A bacteria landing on a salt preserved piece of meat is like a body going
through the Egyptian process of mummification. In Egyptian mummification the
body is buried in a desiccant which draws all the water out of the bodies
tissues and you are left with a dried husk. The salt on the meat pulls the
water out of the bacteria just like the desiccant pulls the water out of the
mummy. You are left with a dried husk of the bacteria.

Other foods like olives and pickles are similarly preserved in brine. The
high salt concentration in the fluid prevents bacterial growth even though
the food is fully hydrated. Again though, the bacteria dehydrates even though
it is floating in water. The high salt concentration on the outside of the
bacteria prevents water from entering the bacterial cell and the bacteria's
own water also leaves it.

So in cases like salted pork, pickles, or honey its the effect on the
bacteria that matters rather than the effect on the food product.  Also as I
mentioned before, some bacteria produce spores (like seeds) when they are
under osmotic stress and the spore can survive until the stressor is removed.

Here is a nifty and good tasting experiment to try.  Take some cut up
strawberries and place them in two bowls.  Add sugar to one bowl (at least a
couple of tablespoons worth) and nothing to the other bowl, then put both
bowls in the frig over night.  The next morning, look and see which bowl has
more juice in it. The answer is the bowl that you added the sugar to.... the
high sugar concentration on the outside of the pieces of strawberry drew
water out of the fruit and produced the juice. You'll also notice that the
sugared strawberries are very soft while the unsugared strawberries are
(probably) still quite firm. Btw, strawberries sugared like this taste sooo
good. <g> This experiment should work with any fruit and you can also do it
with a slice of potato and salt water (place one piece of potato in regular
water and the other in salt water -- then test to see which one gets soft
after 30-60 minutes).

I hope this helps!

Michelle

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