NaCl effects on bacterial growth

Graham Shepherd graham at microhero.freeserve.co.uk
Sun Jun 27 06:17:44 EST 1999


Kostas Polyzonis wrote in message <7l2rhq$3pc$1 at evia.ccf.auth.gr>...
>
>Frogkarma <frogkarma at aol.com> wrote in message
>19990624204225.06507.00003683 at ng-fo1.aol.com...
>>This is very interesting.  Two questions:
>>1) Do you think other salts (Sodium Sulfate for instance) would affect the
>>growth factors due to the specific salt or is it just a matter of water
>>activity?
>>
>>2) What do you mean when you say that the Pathogens have minimal water
>>activity?
>>
>>Thanks,
>>
>>Kevin
>
>1) If NaCl affects growth by lowering water activity (and this is what I've
>been taught) then any electrolyte should do the trick.
>2) Water activity is a good way to express water availability. Salts
>dissociate in water and the charged ions attract water molecules. Those
>water molecules place themselves in layers round the ions and make
>themselves unavailable to bacteria and
>fungi. Thus a low water activity indicates less water available for growth
>and this is why salted food is conserved.
>Kostas
>
>
>

It doesn't have to be ionic - just soluble. That's why we use sugar to
preserve foods as well - in jams and jellies. Moulds hich can survive at
lower water activities can still cause food spoilage in these foods.

GS





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