The Biblical Source for Rinsing Kosher Meat
People who keep the kosher laws follow all of the laws about making animals kosher that are written in the Tanach (Five Books of Moses). One of these laws forbids the eating of removable blood from an animal. In Leviticus 17:12-14, the Torah forbids the consumption of any blood from kosher or non-kosher animals or birds. There are several steps required to remove the blood adequately for kosher consumption.
Removing Parts of the Animal Containing Blood
At its most basic level, this prohibition requires removing all blood vessels and veins in the animal after ritual slaughtering. In addition, the liver must be cleaned particularly well, through a rinsing, salting, and boiling process to remove all of the blood. This is because these organs contain a lot of blood. However, other parts of the animal can be eaten with less preparation.
Rinsing and Soaking the Meat
In order to remove the blood from the meat, the meat must be rinsed entirely. All visible blood must be rinsed off the meat, and the place where the animal was slaughtered must be rinsed well. The meat must then be soaked for half an hour. It should not be submerged in the water for more than 24 hours. When the meat is removed from soaking, the water must be drained off so that it will not dissolve the salt during the salting process.
Salting the Meat
The next step of preparing kosher meat is salting it. Kosher salt, or other salt with medium-sized grains, should be sprinkled over the entire surface of the meat, including pockets and other partially covered areas. The salt is left on the meat for about an hour, and the meat is placed on a draining board on a raised surface. At the end of this time, the salt is shaken off and the meat is rinsed again, three times, in order to remove the excess salt.