In article >, says...
> wrote:
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> > > Ever wonder how food sealed in metal cans is
> > > sterilized without exploding? They do it in large
> > > pressure cookers (called "retorts").
> > >
> > And it's before they're sealed, by the way.
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> You don't know what you're talking about.
> The cans are sealed first, then heat-sterilized
> in a retort.
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> http://www.simplot.com.au/Hosting/co...d+facts.canni=
ng
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> Once cans are sealed they must be processed as soon
> as possible. The usual heat transfer fluids a
> saturated steam
> water
> steam - air mixture
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> http://www.mcc.org/getinv/canning/recipe.html
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> Scoop out as much juice as possible and save in the
> broth vat (to be canned later). Scoop meat into
> 28 oz cans; press meat tightly into the can. Seal the
> cans with a sealing unit. Cook for 2 hours in a retort
> steam cooker at 242 degrees. Cool cans in water
> bath for 30 minutes. Remove from water bath, wash
> grease from can and apply label with glue.
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> http://www.austehc.unimelb.edu.au/tia/084.html
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> At first the sanitary cans were processed in boiling
> water baths, i.e., at 100oC (212=B0F) or in brine baths
> at higher temperatures, as had been done since
> Stefan Goldner introduced them in 1841. At these
> higher temperatures, however, the lighter tinplate
> tended to explode but the steam pressure in a retort
> prevented this and it was not long before retorting
> became general.
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Thanks for the info, Mark. =20

When I was a kid, my mother used to literally "can" things, and I could=20
swear that she handled the metal cans and lids the same way she handled=20
the Mason jars and lids; that is, pressure cooking them in a big canning=20
cooker on top of the stove before sealing. =20

For the cans there was a big crank-operated device clamped to the=20
kitchen table that (I believe) crimped the can and lid together. The=20
glass jars just had lids set on them with a threaded metal ring lightly=20
screwed down to keep the lid in contact with the lip of the jar until=20
the vacuum formed, then the rings came off.

As I recall, there were more than a few failures with the cans (bulging=20
and leaking for whatever reason), and in the latter years of her home=20
preserving career, she used glass jars only. If my memories about the=20
process are accurate, then perhaps the difference is home canning vs.=20
commercial canning in the retorts you described. Or maybe the memory is=20
acting up again...

Anyway, interesting articles. =20

Bob