On 02/09/2013 17:47, Nick Maclaren wrote:
In article ,
Janet wrote:
In article ,
says...
Baz wrote:

I am going to do some beetroot, onions, tomatoes and some cucumbers
(gerkins?).

I may have missed mention of botulism; surely everybody knows that non-acid
foods need the temperature of a pressure canner to be sure?

Nope, nobody in the UK knows that. Here, Kilner jars of fruit/veg are
just filled, closed and cooked in a boiling water pan without pressure.

That is wrong. If you look at most older books, you will see that
the recommendation is exactly as Gary said. Also, some people living
in the UK have previously lived at moderate altitudes, which makes
the requirement more important.

What's more, when we've filled jars with home made jam and put the
lid on, that's it done; we don't boil them at all.

You make entirely non-acid jam? Please post the recipe for our
amusement (if not delectation) :-)

I know that transpondians regard these as dicing-with-death pagan
practices, but we've always done it this way and not died of botulism.

The recommendation always was slightly overstated, because the main
danger comes from high-protein foods. I would very, VERY strongly
advise people not to store such things in that way without the
extra pressure or without checking the seal when using them.

Also, it really only matters for foods that are only lightly cooked
after being removed from the jar. Extended cooking will destroy
the botulinism toxin.


Regards,
Nick Maclaren.

This is the abstract from "Thermal Inactivation of Type E Botulinum
Toxin": See:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC546888/ where there are
several other refs.

"The theoretical required cooking times for inactivation of type E
Clostridium botulinum toxin (5,000 ld50 mouse units per 0.5 ml) in
haddock fillets of various sizes were calculated by graphical
integration of the toxin inactivation rate and heat penetration data.
The results indicated that normal cooking procedures should suffice to
inactivate this amount of toxin. This conclusion was substantiated by
the following additional experimental observations which revealed that
the original experiments had been conducted under conservative
conditions. First, maximal heat stability of the toxin was found to
occur at about pH 5.5, with decreasing resistance upon increasing pH.
The theoretical cooking times were based on destruction of the toxin at
pH 6.7. The pH of radio-pasteurized inoculated haddock, when toxin
production had occurred, was on the alkaline side, at which condition
the toxin is heat-labile. Second, when spoilage was discernible in
radio-pasteurized inoculated haddock, the toxin titer was low, about 50
ld50 mouse units per 0.5 ml. Third, the toxin was adequately inactivated
in toxic fillets after deep-fat frying for 3 min at 375 F (190.6 C) or
after pan frying for 5 min per side at 400 F (204.4 C)."

(Full paper at
http://www.ncbi.nlm.nih.gov/pmc/arti...00232-0039.pdf)

--

Jeff