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Question about low temp cooking (sous vide, slow roast, etc.) and safety
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Thread: Question about low temp cooking (sous vide, slow roast, etc.) and safety

  1. #1

    Question about low temp cooking (sous vide, slow roast, etc.) and safety

    Can someone link me to a site that explains safety issues with low temp cooking? The main thing I'm confused about is why so many people seem scared of very slow roasting if sous vide has been established as safe. What would make cooking in a 165-200 oven different from cooking sous vide? Is it an issue with the efficiency of air vs water when it comes to transferring heat into the food? Even if that's a concern, isn't what makes sous vide safe the length of time the food is kept at that lower temperature (as opposed to 20 minutes at 500 degrees farenheit, for example)? I remember reading something Heston wrote about this I think a couple years ago where he linked to a scientific paper that actually studied this very issue. Can't find it now...

  2. #2
    Senior Member
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    as I mentioned in a previous thread. The following is the current definitive word:

    http://www.fsis.usda.gov/OPPDE/rdad/...try_Tables.pdf

    Since then I have also found this (very technical) report on fish , also from the USDA, alas this oen doens't have a simple table to read information off of, although Table 7 is helpful

    http://www.fsis.usda.gov/wps/wcm/con...df?MOD=AJPERES

  3. #3
    So it seems that most of the info in the links is about only one or two specific bacterial concerns. The concern a lot of people cite is that bacteria will grow in the food in such a low-temp cooking procedure, because it takes so long to raise the internal temp. Would the findings about time/temperature for the bacteria mentioned in these studies be generalizable for other concerns as well? I guess they must be if sous vide is considered safe and restaurants can use it, but I wanted to see a source on it and also a source on cooking the same way in the oven if there is one.

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    Senior Member wellminded1's Avatar
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    This is a good resource I found a few years back, hope it helps you somewhat,
    http://www.cookingissues.com/primers/sous-vide/

  5. #5
    Quote Originally Posted by wellminded1 View Post
    This is a good resource I found a few years back, hope it helps you somewhat,
    http://www.cookingissues.com/primers/sous-vide/
    Thanks for the link. It was definitely interesting. The thing with them, though, is that they claim that low-temp cooking requires a medium more efficient than dry air. That returns me to my initial question, then, which is if it's possible to cook at let's say 165-200F in an oven as long as the interior of the product has been at a certain temperature for a certain length of time. Basically, is there a good case against that kind of super low and slow roasting or not?

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    Senior Member wellminded1's Avatar
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    Personally I do not see anything wrong wit roasting at this temp as long as you finish with a high heat and your core temperature reaches the desired goal. Another thing you have to remember is that sous vide, you usually vac pac, which draws out most of the air, which we know is a contributing factor to bacteria growth.

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    mckemaus's Avatar
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    Sous vide, by definition, is done with ingredient sealed in a bag, i. e. in an anaerobic environment. Many of anaerobic bacteria are nastier than the aerobic one, like Clostridum Botulinum, the bacteria that cause botulism, being one.

    One of advantage using water bath is it is easy to know and to maintain the precise temperature of the bath, compared to ambient temperature and amount energy transferred in a low temp oven.

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    Senior Member Mucho Bocho's Avatar
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    Len, People have been doing low temp cooking since we discovered fire. Think about Crock Pots (Pots of Crock is what I call them). Anyhoo, The main difference between 140 degree air and 140 degree water. Its all about Heat capacity and specific heat. Here is a link with a pretty good diagram. Basically think about how much energy is needed to heat water, we'll water is holding onto the heat and transferrs very efficently to our foods.

    Think about putting your hand in a 200 degree oven. now think (don't try) what would happen to your hand if you put it into 200 degree water.


    http://www.usc.edu/org/cosee-west/Ja...fic%20Heat.pdf
    One thing you can give and still keep...is your word.

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    While reading the USDA one it started to make no sense at all to me. Regarding table 7 they have temperatures listed but they seem to be calculated ones because in their experiments they never achieve those temps. It reads more like they're looking for the best medium to grow Listeria on. Blended crab meat shot up with Listeria then set to 99 degrees for two days...... I have a feeling it would be very hard to get past the smell and texture to even have the slightest thought on trying to eat it.

  10. #10
    Quote Originally Posted by Mucho Bocho View Post
    Len, People have been doing low temp cooking since we discovered fire. Think about Crock Pots (Pots of Crock is what I call them). Anyhoo, The main difference between 140 degree air and 140 degree water. Its all about Heat capacity and specific heat. Here is a link with a pretty good diagram. Basically think about how much energy is needed to heat water, we'll water is holding onto the heat and transferrs very efficently to our foods.

    Think about putting your hand in a 200 degree oven. now think (don't try) what would happen to your hand if you put it into 200 degree water.


    http://www.usc.edu/org/cosee-west/Ja...fic%20Heat.pdf
    So that's what I initially thought, but there are all of these recipes by Heston Blumenthal where he roasts in a super low oven. His roast chicken as well as his prime rib recipes both do that. Any word on safety there?

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