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In the past, I would frequently cook (in the oven) 6+ lbs (3+ kg) of salmon fillets (usually took ~25 min) to an internal temp of 145-150 F (62.5-65 C), take them out, let them set on the counter for an hour or two, and then throw them in vacuum-sealed bags and into the freezer.

Then, when I wanted to eat one, I'd take it out and throw it in the microwave. Understandably not the tastiest thing, but it worked well enough. I've never tried it with meat, only fish. As far asI know this never made me sick.

Now, all of the sous vide literature emphasizes a rapid chill in an ice water bath if you want to freeze something. Is this really necessary? For a very thick steak (say 2 in (5 cm)) it could take 3+ hours to fully chill down to 41 F (5 C) in the middle, so if that's still safe to eat, why must you chill thinner cuts? I'd expect anything 1in or less to chill within 3 hours in the freezer. Obviously, you can extrapolate this out and say that, e.g., a 0.125 inch (0.3 cm) cut wouldn't need to be chilled in an ice bath, so the blanket suggestion is only necessary above a certain thickness.

If anyone has found graphs of time/temperature when freezing meat from a cooked temperature, that would be helpful. If that doesn't exist, what's a best guess for the thickness at which pre-freezer ice baths become important for safety?

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2 Answers

Yes, fast chilling is critical because it minimizes the production of new bacteria and potentially deadly toxins from the spores of anaerobic pathogens such as C. botulinum and C. perfringens. The spores are not killed by the low temperatures usual in sous vide, and the oxygen-free environment of the bag brings them back to activity. But they require time and temperature to become active and dangerous, so fast chilling -- either refrigeration or freezing -- and limiting the refrigeration time (to about 5 days at around 5°C/40°F, longer for lower temperatures) are absolutely critical to deter them.

The question starts with a situation that is different: cooking in an oven, which is not an anaerobic environment and thus does not trigger the same activation of the spores' lifecycles as cooking in a vacuum does.

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FDA regulations state, when cooling, max 2h between 21-57C (70-135F) and no more than 6h total between 5-57C (41-135F). You are allowed to cook at below 57C. –  Stefan Dec 3 '12 at 14:56
    
+1 for the answer about sous vide in the first paragraph. I would +1 again if I could for your second paragraph because I don't really get what he's asking. –  Carey Gregory Dec 24 '12 at 6:37
    
and if your super worried about the bacteria you can do a quick blanch of the fish before cooking. –  Brendan Feb 18 '13 at 14:03
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Also, safety aside, cooling in an ice/water bath can be done very rapidly and therefore the freezing in the freezer will create much smaller ice crystals and therefore create a better texture in your reheated product (but that may not be a concern of yours if your reheating salmon in the nuker).

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