He who made the world gave to humanity the Law of life. He knows better than anyone what is good and useful for well-being of humans. Just as if a doctor prescribes medicines or diet, the patient will follow the doctor's orders even without understanding their meaning. The patient understands that the doctor knows best what treatment is necessary and takes prescribed medicines even if he has no idea how they work.
Torah prohibits using of any blood for food. How to keep this rule?
Torah says: "Don't eat blood". Oral Torah explains that only arterial and venous blood is prohibited. Capillary blood is allowed if it is stagnant. Practically it means that even if there are no other blood vessels but capillaries in a piece of meat the problem still exists: during cooking heated capillary blood will drift and become prohibited together with the whole piece of meat. That is why all blood should be removed before boiling or frying. Salting-out is a good way for its removing. First you should put meat in the water for half an hour, than salt it well and put on the grating. In one hour it should be rinsed for three times.
We gave the shortest description of the process that is why those who used to buy birds or fresh meat in the market place should ask competent rabbi about all details. Those who buy frozen meat should make sure it was salted-out beforehand. Usually the inscription in Hebrew indicates this.
The most topical question is related with liver because it contains so much blood. Torah allows eating of liver but without blood only. Though, the matter is that it is very difficult to remove all blood from liver by salting-out as distinct from other kinds of meat. Even after very strong salting some blood will remain inside and ooze out during cooking.
That is why the only allowed way of cooking liver is grilling. In this case the oozed blood trickles down and is not absorbed back as while boiling or frying in pan. The blood that doesn't ooze out while cooking and remains in meat is allowed.
How to cook liver?
1) The whole liver should be cut along and across to dissect veins.
2) Rinse the liver and salt it out a little.
3) Lay out liver on grill over the fire right away.
4) The grilled liver should be rinsed one more time. Now it can be served or you can go on cooking (boil or stew it).
And the last remark: don't keep liver within 24 hours in place without drain for blood (water, dry pot or plastic bag).
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