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Meat Bacteria
Name:Lisa
Status: Student
Age: 15
Location: N/A
Country: N/A
Date: N/A
Question:
Hi,
I'm planning on doing an experiment to test what
sort of substances can
prevent meat from rotting (eg. salt, sugar,
vinegar, vegetable oil), and
trying to find some background info before I start.
Could you tell me:
what types of bacteria are in meat - what are they
called and what are
they like? which meats have them? (what is a good
meat to use?) which ones
and how do they make the meat 'rot'? how is this
prevented chemically?
(a bit of a dumb question now) how can I tell that
the meat has rotted? -
what do I look for? how long does it usually take?
Sorry for asking so many questions. I'm just having
a bit of a hard time
finding the answers.
Thanks :)
Replies:
What type of bacteria are IN meat? none, or the animal
that produced the meat (muscles, mostly) must have
been VERY ill. But on the surface of the meat you'll
find lot's of bacteria that found their way there
during slaughter, preparation, storage of the meat.
These can be all kinds, but due to the slaughtering
process, fecal bacteria will be overrepresented.
Most meat is treated to prevent bacterial growth
during processing, especially by drying and heating.
The best meat to use in your case is chicken, because
that can not be dried as beef or pork: it would change
color and would not look nice (hence would not sell).
Chances are you get pathogenic (ill-making) bacteria
on chicken meat, especially Campylobacter and
Salmonella, so wear gloves whenever you handle the
meat, and carefully clean and desinfect all utensils
afterwards.
Which bacteria make meat 'rot'? Lactobacilli would
turn the meat sour, any food-poisening bacteria would
make the meat unfit for consumption (and dangerous to
handle). The bad smell that warns you meat is 'off'
are biochemical compounds produced by the bacteria
when they grow, but also degradation compounds
produced by enzymes released by the meat itself, as
part of the natural decaying process.
You can speed up the process by increasing the
temperature. 37 C is the optimum, and at this
temperature meat will begin to smell very soon,
rotting takes place within 24 hrs. Don't do this
experiment in the vicinity of food stuff, and don't
eat or drink anything during practical handling.
Carefully wash hands afterwards.
How to tell the meat is rotten? check texture (punch
it), smell, color. Measure the weight (does it remain
constant?). If you can grow bacteria, Take a swab of a
standardized square of the surface with a sterile swab
and put this in a standardized amount of broth.
Culture this on an agar plate and see how many, and
what different, colonies grow.
For more bacteriological background on the dangers of
bacteria growing on meat and other foodstuff, check
the subject 'food safety' in the Virtual Museum of
Bacteria, at www.bacteriamuseum.org (or go there
directly:
www.bacteriamuseum.org/niches/foodsafety/foodsafety.shtml
Trudy Wassenaar
Curator of the VMB
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Update: June 2012
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