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Comment by whyenot | Hacker News Reader

I would be at least a little worried about food poisoning. Cooking salmon at 115 deg F, or beef at 125 deg F or even chicken at 140 deg F is not a high enough temperature to kill off many harmful bacteria and parasites. In normal cooking, the external surfaces of the meat, where most contamination occurs, reach much higher temperatures.

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Killing most bacteria is a function of temperature and time. The higher the heat, the less time it has to be at that temperature. The lower the heat, the longer it has to be at that temperature. It's all a numbers game. Nothing is completely safe.

That's not entirely true. If you for instance "cook" meat at 100 degrees you'd end up with more bacteria than you started with. You do need to cook at a temperature that is hot enough to actually kill the bacteria. It's not a numbers game at all, it's understanding a little microbiology.

Nothing is completely safe, but food poisoning is also not fun.

I highly recommend that anyone read this information before attempting sous vide. It outlines the various bacteria involved and the time/temp calculations for various items:

http://amath.colorado.edu/~baldwind/sous-vide.html

128f and above, with the caveat that pasteurization takes a lot longer at 128f than it does at 150f.

Typically you would sear the fish/beef/chicken before/after for texture, flavor and color. Beef for instance will come out grey on the outside and look unpleasant unless seared (inside is still bright red/pink though).

The bigger risk is the time that the food is left in the danger zone of above 50 degrees and below 125 degrees (don't quote me on those numbers, going off memory). Basically any bacteria present in food in that temp range will start reproducing quickly. I have heard 4 hours as the time limit acceptable to have food in that temp range before being considered unsafe.

Beef is ideal to sear just before SVing, not only does it seal in the moisture, but the most dangerous bacteria on beef is on the surface, and just slapping the beef down in a very hot pan, flipping and removing is enough. This is why you can have a blue steak that is cold on the inside (not in many restaurants however) and cooked on the outside.

Searing your steak before cooking would likely aid in the hacked SV as a lack of vacuum sealing means some moisture may be lost, but searing prevents this. It also protects the average, less experienced, cook from giving themselves a wicked case of food poisoning.

Searing does not prevent any moisture loss. http://en.wikipedia.org/wiki/Searing

The whole point is that temperature of the medium is unrelated to the temperature of the food. A raw steak is a steak that reaches UPTO temerature X (about 55C I think) during the cookieng. So you can put it into a low temp cooking device for an hour on 55C or you can throw it onto a 200C owen and leave it there just enough time for it to heat upto 55C.

If you miss this 55C point and it heats upto 60C it wont be raw anymore. After all: "The entire range of steak doneness, from rare to well-done, is only a matter of 14°C (25°F)" (http://www.cookingissues.com/primers/sous-vide/part-i-introd...)

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