- Joined May 15, 2010
So its anarobic, but how can the food locked up in a little pouch being cooked at 140'f for 3 days stay in the 'danger zone' for so long without the bacteria thriving?
No, that is just another use of Sous Vide. As a first step, you might want to read the reference cited: http://amath.colorado.edu/~baldwind/sous-vide.html and it will answer a majority of your questions.I will look into these things you've posted. BTW does this imply that sous vide is generally a process used for processed foods and not generally for restaurant items? -based on the fact that you immediately freeze the sealed foods instead of holding toem for service.
As pretty well explained in Baldwin's Sous Vide, the "key" is the difference in thermal conductivity of air and water AND that pasteurization is a time-temperature function, not just temperature.ok, my concern comes from stories like the holiday classic; Grandma cooks a stuffed bird in the oven at 170 degrees for 20 hours, whole family gets botulism and falls down like birds. How does Sous Vide avoid the exponential multiplication of such pathogens while taking it's sweet time getting up to temperature? (still working on Baldwins Sous Vide page, thick stuff )
Never heard of botulism in the stuffing. Usually canning something, infused oil. On the net I found a case of baked potato's as the cause, wrapped in foil, baked the day before and left at room temp until serving the next night. Isnt sous vide process usually just an hour or so? Even so I would cool it in an ice bath to get temp below 40' as quick as possible.ok, my concern comes from stories like the holiday classic; Grandma cooks a stuffed bird in the oven at 170 degrees for 20 hours, whole family gets botulism and falls down like birds. How does Sous Vide avoid the exponential multiplication of such pathogens while taking it's sweet time getting up to temperature? (still working on Baldwins Sous Vide page, thick stuff )
Hmm, I think you may be misinterpreting the Food Code requirements, the "four hour" rule, does NOT say it must be cooked within four hours, only that it must be above 135°F (140°F in some jurisdictions) within four hours and it cannot be removed from the heat until pasteurized, which involves the "doneness" temperatures that everyone has on their mind, i.e. 155°F for ground beef, 165° for poultry, etc. FWIW, those are the zero time pasteurization temperatures.Pete McCracken: Ah, I assumed that since items are cooked at lower-than-poaching temperatures (assumption) wouldn't act so fast. I guess I was thrown off by the remarks of overnight sous vide cooking (which doenst follow the time-temp. safety guidelines unless it is cooked within 4 hours and continues to cook to achieve a fiberless protein).
Many bacteria are quite prolific in anaerobic conditions. C. botulinum is one of them. The difference is byproduct of metabolism. For example Human muscle cells work most efficiently aerobically, and the byproduct is carbon dioxide. However when oxygen demand exceeds supply muscle metabolize anaerobically and the byproduct is lactic acid. When C. botulinum engages in anaerobic metabolism (like in a bag or can free of O2) then the byproduct is botulism toxin. These toxins can be destroyed but it requires extreme temperature. toxins are not alive, bacteria are. You don't kill a toxin you denature it. You can kill C. botulinum with pasteurization temperatures, but not its spores, or it's toxin.That makes sense because bacteria cannot multiply in anaerobic conditions. The botulism probably feeds off something in the food -- would it be because the food wasn't properly packaged or sterilized?. Salmonilla multiplies to dangerous amounts if it's in suitable conditions for a long enough window of time (temperature, moisture, protein, oxygen, acid...).
Despite the bacterium's fearsome reputation, _C. botulinum_ is still a microbe, and can be killed using a little basic microbiology. Preserving recipes utilize at least one of these 5 microbiological facts, good recipes often use several.
1. _C. botulinum_ bacterium dies at 212 F/ 100 C.
2. _C. botulinum_ spores die at 240 F/ 116 C.
3. Botulism toxin denatures at 185 F/ 85 C.
**(All temperatures must be maintained for least 15 minutes, and the heat must be consistent throughout the food, fluid, and jar.)**
4. _C. botulinum_ spores cannot hatch in strong acid solutions of pH 4.6 or below. (Some sources claim pH 4.7.)
5. _C. botulinum_ cannot grow, develop, or multiply in food with a water content of less than 35%. (Food dehydrators have another set of toxic pests to worry about, see IV.6 about aflatoxin.)
Common sense is a first step in the prevention of botulism.
Read more: http://wiki.answers.com/Q/How_do_you_denature_botulism_toxin#ixzz18Ofu0eep
The toxin can be denatured. Temps above 160 will do that. And no, I'm not confusing it with salmonella temps. The temp KYH quoted is higher than that but we must be using different source material.