Many animals permitted in kashrut are also halal, such as bovines.
To be kosher, aquatic animals must have scales and fins. Most Muslim schools of thought adhere to the interpretation that all creatures from the ocean or the sea or lake are considered halal.Shi'ites also follow this, but make an exception with some crustaceans; shrimps and prawns are halal. According to Jewish oral law all fish that have scales have fins, thus making all fish with scales kosher and rendering the law essentially the same as the more restrictive interpretations of halal.
Gelatin is only permissible if it comes from a permissible animal (usually kosher gelatin comes from the bones of kosher fish, or is a vegan substitute, such as Agar).
Almost all insects are not kosher. The few kosher insects are specific types of locusts and grasshoppers (see Kosher locust) which are not eaten today in most communities, since it is unknown which species is permitted (the exception being the Yemenite Jews, who claim to have preserved this knowledge).
For a substance to be halal, it must not contain alcohol of any kind. However, there is a difference drawn between the addition of alcohol to foods, which is absolutely forbidden, and the small quantities that naturally become present – such as orange juice. Except for grape wine and grape juice (which must be manufactured under Jewish supervision), kashrut allows the consumption of any sort of alcohol, as long as it has kosher ingredients (excluding any unsupervised grape extracts).
The list of animals forbidden by kashrut is more restrictive, as kashrut requires that, to be kosher, mammals must chew cud and must have cloven hooves. Halal only requires that an animal survive on grass and leaves. Thus some animals such as the camel are permissible under halal, but not according to kashrut.
Kashrut requires strict separation of dairy and meat products, even when they are kosher separately.
Shechita is the ritual slaughter of mammals and birds according to Jewish law. Dhabiha is the method used to slaughter an animal in Islamic tradition. Shechita requires that an animal be conscious and this is taken to mean the modern practice of electrical, gas, or percussive stunning before slaughter is forbidden. Most Muslim authorities[who?] also forbid the use of electrical, gas, or percussive stunning. However, other authorities state that stunning is permissible so long as it is not the direct cause of the animal's death.
Both shechita and dhabiha involve cutting across the neck of the animal with a non-serrated blade in one clean attempt in order to sever the main blood vessels.
Both require draining the blood of the animal.
Any sane adult Jew who knows the proper technique may perform shechita. Similarly, dhabiha can be performed by any "sane adult Muslim… by following the rules prescribed by Shariah". All Islamic authorities, though, state that dhabiha can also be performed by Peoples of the Book-(Jews and Nazarenes).
Dhabiha requires that God's name be pronounced before each slaughter. (see Islamic Concept of God). Dhabiha meat by definition is meat that is slaughtered in the shariah manner and the name of Allah is said before the slaughter. In Shechita, a blessing to God is recited before beginning an uninterrupted period of slaughtering; as long as the shochet does not have a lengthy pause, interrupt, or otherwise lose concentration, this blessing covers all the animals slaughtered in that period. This blessing follows the standard form for a blessing before most Jewish rituals ("Blessèd are you God ... who commanded us regarding [such-and-such]", in this case, Shechita). The general rule in Judaism is that for rituals which have an associated blessing, if one omitted the blessing, the ritual is still valid [see Maimonides Laws of Blessings 11:5]; as such, even if the shochet failed to recite the blessing before Shechita, the slaughter is still valid and the meat is kosher.
There are no restrictions on what organs or parts of the carcass may be eaten from a Halal-slaughtered and -dressed animal; as long as it was slaughtered and prepared according to the rules of Halal, the entire animal, with the exception of blood (Qur'an 2:173), is fit for consumption by Muslims. However, Kashrut prohibits eating the chelev (certain types of fat) and gid hanosheh (the sciatic nerve), and thus the hindquarters of a kosher animal must undergo a process called nikkur (or, in Yiddish, porging) in order to be fit for consumption by Jews. As nikkur is an expensive, time-consuming process, it is rarely practiced outside of Israel, and the hindquarters of kosher-slaughtered animals in the rest of the world are generally sold on the non-kosher market.
After slaughter, both require that the animal be examined to ensure that it is fit for consumption. Dhabiha guidelines generally say that the carcass should be inspected, while kashrut says that the animal's internal organs must be examined "to make certain the animal was not diseased".
Both sets of religious rules are subject to arguments among different authorities with regional and other related differences in permissible foodstuffs.
Strictly observant followers of either religion will not eat in restaurants not certified to follow its rules.
Meat slaughtered and sold as kosher must still be salted to draw out excess blood and impurities. A similar practice is followed in some Muslim households, but using vinegar. This is done to remove all surface blood from the meat, in accordance with Islam's prohibition of the consumption of blood.
During the Jewish holiday Passover, an additional set of restrictions requires that no chametz (sour-dough starter or fermented products from the five species of grains) be eaten. This requirement is specific to the holiday, and nothing to do with the laws of Kashrut.
In general, Kashrut prohibits the mixing of meat and dairy products; consumption of such products or profiting from their sale are also forbidden. These proscriptions are not observed in Karaite Judaism. Halal has no such rules.
In Judaism, the permissibility of food is influenced by many secondary factors. For instance, vessels and implements used to cook food must also be kept separate for dairy products and meat products. If a vessel or implement used to cook dairy products is then used to cook meat, the food becomes non-kosher and the vessel or implement itself can no longer be used for the preparation or consumption of a kosher meal. Depending on the material properties of the item (for example, if it is made of metal or of clay, or if it is made in one piece or has joints) it may be rendered permissible ("kashered") by certain procedures or it may be considered irretrievably contaminated. In general, the same policy extends to any apparatus used in the preparation of foods, such as ovens or stovetops. Laws are somewhat more lenient for modern kitchen items such as microwaves or dishwashers, although this depends greatly on tradition (minhag) or individuals' own stringent practices (chumrot). As a result of these factors, many Conservative and Orthodox Jews refuse to eat dishes prepared at any restaurant that is not specifically kosher, even if the actual dish ordered uses only kosher ingredients.
Likewise in Islamic food preparation, the permissibility of food is also influenced by many secondary factors. Apart from the prescribed foods that can be consumed, all food must be Halal and by this, all utensils and kitchens used to prepare food must also be deemed as Halal. Halal utensils and kitchens require that these utensils or food preparation surfaces do not get in contact with non Halal items. For instance, cakes prepared using alcohol as an ingredient are considered non Halal. In fact, food cooked in any type of alcohol (even if the alcohol burns out during the cooking process) is also deemed non Halal. Kitchens which have been used to prepare non Halal food must be sanitized (samak) according to Islamic principles before they can be used to prepare Halal meals. Kitchens and utensils previously used to prepare non Halal meals are required to be fully sanitized in an Islamic fashion before they can then be used for Halal food preparation.