Ask A Scientist© Molecular Biology Archive

>
> > >  name       Lisa
> > >  status     student
> > >  age        15
>
> > >  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 :)
> >
>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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