One of the main biblical food laws is the restriction of consuming blood on account of the life [being] in the blood; this ban and reason are listed in the Noahide Laws, and twice in leviticus, as well as by Deuteronomy The Priestly Code also prohibits the consumption of fat, if it came from sacrificial land animals (cattle, sheep, and goats), since the fat is the portion of the meat exclusively allocated to Yahweh (by burning it on the altar).
The classical rabbis argued that, in a number of cases, the prohibition against consuming blood was impractical, and there should be exceptions; they claimed that eating the blood that remained on the inside of meat (as opposed to the blood on the surface of it, dripping from it, or housed within the veins), would be permitted, and that the blood of fish and locusts may also be eaten.
A number of preparation techniques became practiced within traditional Judaism to comply with this prohibition. The main technique, known as melihah, involves the meat being soaked in water for about half an hour, that opens pores; after this, the meat is placed on a slanted board or in a wicker basket, and is thickly covered with salt on each side, and left for between twenty minutes and one hour. The salt covering draws blood from the meat by osmosis, and so the salt has to be subsequently removed from the meat (usually by trying to shake most of it off, and then washing the meat twice ) in order to complete the extraction of the blood.
Melihah is not enough to remove blood from the liver, lungs, heart, and certain other internal organs, as they naturally contain a high density of blood, and hence these organs are generally removed before the rest of the meat is salted; roasting on the other hand will normally lead to blood to be discharged, and it is therefore the usual treatment given to these organs (if they are to be eaten at all), and it is also an alternative cooking method for the rest of the flesh.
