Dave Fawthrop wrote:
On Sat, 6 May 2006 13:25:22 +0100, Tom Anderson
wrote:

|On Sat, 6 May 2006, David P wrote:
|
| On 06 May 2006, Dave
| wrote:
|
| On Sat, 06 May 2006 00:34:13 +0100, The Natural Philosopher
| wrote:
|
| |Raising the water to 60 C kills about 95% of the bugs in seconds.
|
| That temperature is actually *82* deg C to kill food poisoning bugs
| Some food poisoning bugs breed nicely below 64 deg C
|
| I think amino-acids/proteins get denatured (and becoma deformed beyond
| use) at about 62 degrees.
|
|Depends on the protein - there's quite a variation in denaturation
|temperature, and it depends on the chemical environment etc. 60-odd
|degrees is in the right area, though.
|
| I thought that was the basis for saying that food (eggs, meat, etc) must
| be cooked over approx 62 C.
|
|That's because that's the sort of temperature where collagen denatures,
|becoming gelatin, which is how cooking softens meat. I believe collagens
|from different kinds of animals have different conversion temperatures - i
|ISTR 58 C for fish and 65 C for mammal meat.

I am not disputing your protein denaturing figures, it is just that
bacteria are not just protein, but a lot tougher. Some will withstand
greater than 100 deg C and even breed at that temp.

http://textbookofbacteriology.net/nutgro.html
Table 10c. Hyperthermophilic Archaea.
Temperature for growth(degrees C)
Genus Minimum Optimum Maximum Optimum pH
Sulfolobus 55 75-85 87 2-3
Desulfurococcus 60 85 93 6
Methanothermus 60 83 88 6-7
Pyrodictium 82 105 113 6
Methanopyrus 85 100 110 7


Figure 8. Sulfolobus acidocaldarius is an extreme thermophile and an
acidophile found in geothermally-heated acid springs, mud pots and surface
soils with temperatures from 60 to 95 degrees C, and a pH of 1 to 5. Left:
Electron micrograph of a thin section (85,000X). Under the electron
microscope the organism appears as irregular spheres which are often lobed.
Right: Fluorescent photomicrograph of cells attached to a sulfur crystal.
Fimbrial-like appendages have been observed on the cells attached to solid
surfaces such as sulfur crystals.T.D. Brock. Life at High Temperatures.



Fortunately for us, species adapted for 100C do not do well inside a
stomach at 38C...

In short, most if not all bacteria that are happy to live inside us, are
not happy to live at the temperatures at which food is cooked (about
50-100C depending) Nor at temperatures around freezing or les. Like us,
they die at those sorts of temperatures, which is why we freeze food,
and we cook it.

Now of course the stupid little pedants will jump in and tell you that
this doesn't kill them ALL. but so what? the world is full of bacteria,
and thats why we have immune systems.

Nothing is safe, but water at 60C plus is a lot safer than eating a two
week old pork pie.