Salt and meet preservation

  1. I was reading this post regarding meat preservation.
    http://answers.yahoo.com/question/index?qid=20061022184303AALaiDt

    Basically, salt draws out the water from meat which keeps insects away since insect are attracted to water.

    There's one point that is glossed over: how does salt, which is NaCl draw out or absorb water? What is the chemical reaction that breaks water down? How does salt on the surface extract water in the center of meat?
     
  2. jcsd
  3. Borek

    Staff: Mentor

    I haven't read the linked text, so I am not going to comment on that. But salt doesn't break water down. Read about osmosis.
     
  4. The salt preservation inhibits bacterial growth on the surface of the meat, whether that be from airborne bacteria landing on the surface or bacteria deposited by insects.

    To some extent you do the same when you buy strawberries and coat them with sugar - it is done not just to add a sweeter taste, but to allow the strawberries to last longer.
     
  5. There are actually a couple of variables with meat. If it is a whole muscle (i.e., not a ground sausage - salami) then salt is sufficient for curing as it will act on the exterior quickly both killing bacteria with its salinity and on the interior by drawing water from the meat by osmosis thus creating a condition where bacteria can't grow. The exception here is the fat, which while preserved can still go rancid if exposed to light for some time.

    With salami, ground sausages, salt is not sufficient. Think of e coli as an analogy - you don't need to worry about it grilling a steak since it can only exist on the exterior, so grilling a steak rare is no problem. But with ground beef, where the exterior has likely moved to the interior, it's a problem, so burgers need to be cooked to at least medium to be safe.

    Similarly, salami are plagued by botulism. Botulism comes from spores that create bacteria that in turn secrete the venom that causes botulism, which is a very bad disease. But for the spores to create the bacteria, they need 2 conditions - 1. temperature between 40d F and 140d F (I might be off on the latter), and 2. An anaerobic environment (no oxygen) - i.e., the inside of a sausage.

    Salt is not sufficient here (still used, but needs some help). To kill the spores requires sodium nitrite, which is delivered either directly as sodium nitrite or in combination as that plus sodium nitrate in longer curing sausages as the nitrate decomposes to the nitrite which is the actual working chemical. Actually, I think the nitrite is the key as saltpeter (Potassium Nitrite/Nitrate?) use to be used way back when. But saltpeter keeps a good man down. ;)

    Regardless, NaCl is the king of preservatives. If you have more curiosity on this, search on "charcuterie" - the art/science of preserving meats.


    Chris.
     
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