788. When it’s Too Cold to be Kosher
After an animal or fowl is ritually slaughtered, its meat has to be kashered within seventy-two hours; first it must be soaked in water for half an hour, then salted and left to drain for an hour, after which it is rinsed to remove all blood. Halacha dictates that the water used for soaking should not be hot, but poskim further caution that it shouldn't be too cold either, as water which is too cold is metarshi lei (hardens it [the meat]), instead of softening it in preparation for salting.
Poskim define “too cold” by referring to the chill factor of a certain day, place or season–all which are extreme. Some posit that “too cold” refers to water that is so cold that it is too uncomfortable to be used for hand-washing. Contemporary poskim argue regarding the exact temperature that is considered too cold for soaking un-kashered meat; it is generally accepted that the water should certainly not be below 3 degrees Celsius (a little more than 37 degrees Fahrenheit).
There is difference of opinion among poskim whether the meat is considered kosher b'dieved (after the fact) if freezing (or near-freezing) water was used. Certainly, b'hefsed merubah (in a case of great loss) many poskim deem it permissible for eating. Alternatively, the damage of freezing water can be mitigated if the meat is re-soaked in lukewarm water before salting. There are poskim who argue that even those authorities who permit consuming the meat that was soaked in freezing water would maintain that if the meat was hot at the time of soaking the damage is irrevocable, and the meat is assur (prohibited) even b'dieved.
(It should be pointed out that there are poskim who do not raise the issue of cold water at all. The Shulchan Aruch, in fact, does not mention cold water in this context.)
There are also many locales where government regulations necessitate the use of cold water only for raw meat handling, so lukewarm water may not be used for kashering. In such cases, the water temperature should be measured carefully, so it is not too cold for soaking according to halachah. Many contemporary slaughterhouses take into account that the natural warmth of fresh meat works to counteract the chill of the water to bring the soaking temperature to a halachically acceptable degree.
However, if the water was very cold initially we should be stringent and soak the meat a bit longer than the requisite half-hour soaking time, so it will be immersed for a full half hour in water that is no longer extremely cold.