Kosher foods

The classic rabbinical writers imply that milk from an animal whose meat is kosher is also kosher. As animals are considered non-kosher if they are discovered to have been diseased after being slaughtered, this could make their milk retroactively non-kosher. However, by adhering to the principle that the majority case overrules the exception, Jewish tradition continues to regard such milk as kosher, since statistically it is true that most animals producing such milk are kosher; the same principle is not applied to the possibility of consuming meat from an animal that has not been checked for disease.[13] Rabbi Hershel Schachter argued that with modern dairy farm equipment, milk from the minority of nonkosher cows is invariably mixed with that of the majority of kosher cows, thus invalidating the permissibility of consuming milk from a large dairy operation.[13] Many leading rabbis, however, rule milk permissible,[14] as do major kashrut authorities.[13]

Breast milk from a human female is permitted.[15] However, authorities assert breast milk may be consumed directly from the breasts only by children younger than four (five if the child is ill), and children older than two were only permitted to continue to suckle if they had not stopped doing so for more than three consecutive days.[15]

The situation of cheese is complicated as hard cheese usually involves rennet, an enzyme that splits milk into curds and whey. Most forms of rennet were formerly derived from the stomach linings of animals, but currently rennet is most often made recombinantly in microbes (though most European cheese still uses animal rennet). Because the rennet could be derived from animals, it could potentially be nonkosher. Only rennet made recombinantly, or from the stomachs of kosher animals, if they have been slaughtered according to the laws of kashrut, is kosher.[16]

According to the Shulchan Aruch, a rabbinic decree (called gevinat akum) prohibits all cheese made by non-Jews without Jewish supervision, even if its ingredients are all kosher, because very frequently the rennet in cheese is not kosher.[17] Rabbeinu Tam[18] and some of the geonim[19] suggested that this decree does not apply in a location where cheese is commonly made with only kosher ingredients, a position that was practiced in communities in Narbonne[20] and Italy.[21] Contemporary Orthodox authorities do not follow this ruling, and hold that cheese requires formal kashrut certification to be kosher; some even argue this is necessary for cheese made with nonanimal rennet. In practice, Orthodox Jews, and some Conservative Jews who observe the kashrut laws, eat cheese only if they are certain the rennet itself was kosher. However, Isaac Klein's tshuva authorized the use of cheese made from non-kosher rennet, and this is widely practised by observant Conservative Jews and Conservative institutions.[22]

Jerusalem kugel made with egg noodle, caramelized sugar and black pepper

The eggs of kosher birds are kosher. Eggs are considered pareve despite being an animal product.[23]

Occasionally blood spots are found within an egg, which can affect the kosher status of the egg. The halacha varies depending on whether or not there is a possibility of the egg being fertilized.

If the egg may have been fertilized, the Rishonim and Shulchan Aruch suggest a complex set of rules for determining whether the egg may be eaten;[24] among these rules, if blood appears on the yolk, the entire egg is forbidden.[25] To avoid the complexity of these rules, R' Moshe Isserles records a custom not to eat any such eggs with blood spots.[24]

If the egg was definitely unfertilized (laid by a hen kept isolated from roosters), many authorities (including Rabbis Moshe Feinstein and Ovadiah Yosef rule that one may remove the blood spot and then eat the remainder of the egg.[24] This is the case nowadays, when battery eggs form the majority of available produce.[26]

Regarding the question of whether one must check an egg for blood spots, the Shulchan Aruch rules that one may eat hard-boiled eggs where checking is impossible.[27] R' Moshe Isserles adds that checking is not required, but that a custom exists to check eggs if they are cracked during the daytime (when blood could be seen).[27] A contemporary Ashkenazi authority writes that while "halacha does not require" checking supermarket-bought eggs, "there is a minhag" to do so.[24] Nevertheless, eggs are not checked in commercial settings where doing so would be expensive.[24]

Kosher gummy bears

Gelatin is hydrolysed collagen,[28] the main protein in animal connective tissue, and therefore could potentially come from a nonkosher source, such as pig skin. Gelatin has historically been a prominent source of glue, finding uses from musical instruments to embroidery, one of the main historic emulsions used in cosmetics and in photographic film, the main coating given to medical capsule pills, and a form of food including jelly, trifle, and marshmallows; the status of gelatin in kashrut is consequently fairly controversial.

Due to the ambiguity over the source of individual items derived from gelatin, many Orthodox rabbis regard it as generally being nonkosher. However, Conservative rabbis[29] and several prominent Orthodox rabbis, including Chaim Ozer Grodzinski and Ovadia Yosef – the former Sephardic Chief Rabbi of Israel – argue that gelatin has undergone such total chemical change and processing that it should not count as meat, and therefore would be kosher.[30] Technically, gelatin is produced by separating the three strands in each collagen fiber's triple helix by boiling collagen in water. Rabbi Dr. David Sheinkopf, author of Gelatin in Jewish Law (Bloch 1982) and Issues in Jewish Dietary Laws (Ktav 1998), has published in-depth studies of the kosher uses of gelatin, as well as carmine and kitniyot.

One of the main methods of avoiding nonkosher gelatin is to substitute gelatin-like materials in its place; substances with a similar chemical behaviour include food starch from tapioca, chemically modified pectins, and carrageenan combined with certain vegetable gums – guar gum, locust bean gum, xanthan gum, gum acacia, agar, and others. Although gelatin is used for several purposes by a wide variety of manufacturers, it has started to be replaced with these substitutes in a number of products, due to the use of gelatin also being a significant concern to vegans and vegetarians.

Today manufacturers are producing gelatin from the skins of kosher fish, circumventing many of these problems.[31]

As forbidden fats, tendons, blood vessels and the gid hanasheh (sciatic nerve) must be removed, and this is more difficult in the rearquarters, often only cuts of meat from the forequarters are commonly available.

Leviticus prohibits the eating of certain types of fat (chelev) from sacrificial land animals (cattle, sheep, and goats), since the fat is the portion of the meat exclusively allocated to God (by burning it on the altar).[43]

The gift of the foreleg, cheeks and maw of a kosher-slaughtered animal to a Kohen is a positive commandment in the Hebrew Bible. Some rabbinic opinions maintain that consumption of the animal is forbidden before these gifts are given, though the accepted halacha is to permit this. Furthermore, the actual foreleg, cheeks and maw of all kosher-slaughtered beef are forbidden to a non-kohen unless the kohen permits.[44]

One of the main biblical food laws forbids consuming blood on account of "the life [being] in the blood". This ban and reason are listed in the Noahide Laws[45] and twice in Book of Leviticus[46] as well as in Deuteronomy.[47]

The classical rabbis argued that, in a number of cases, only if it is impossible to remove every drop of blood, the prohibition against consuming blood was impractical, and there should be rare exceptions: they claimed that consuming 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) should be permitted and that the blood of fish and locusts could also be consumed.[48]

To comply with this prohibition, a number of preparation techniques became practiced within traditional Judaism. The main technique, known as meliḥah, involves the meat being soaked in water for about half an hour, which opens pores.[49] After this, the meat is placed on a slanted board or in a wicker basket, and is thickly covered with salt on each side, then left for between 20 minutes and one hour.[49] The salt covering draws blood from the meat by osmosis, and the salt must be subsequently removed from the meat (usually by trying to shake most of it off and then washing the meat twice[49]) to complete the extraction of the blood. The type of salt used in the process is known as kosher salt.

Meliḥah is not sufficient to extract blood from the liver, lungs, heart, and certain other internal organs, since they naturally contain a high density of blood, and therefore these organs are usually removed before the rest of the meat is salted. Roasting, on the other hand, discharges blood while cooking, and is the usual treatment given to these organs. It is also an acceptable method for removing blood from all meat.[49]

The laws of kashrut can be broken for pikuach nefesh (preservation of human life). For example, a patient is allowed to eat non-kosher food if it is essential for recovery,[57] or where the person would otherwise starve.[58][59]

The Talmud adds to the biblical regulations a prohibition against consuming poisoned animals.[60] Similarly, Yoreh De'ah prohibits the drinking of water, if the water had been left uncovered overnight in an area where there might be snakes, on the basis that a snake might have left its venom in the water.[42] In a place where there aren't usually snakes, this prohibition does not apply.[61]

The Talmud and Yoreh De'ah suggest that eating meat and fish together may cause tzaraath.[62] Strictly Orthodox Jews thus avoid combining the two,[63][64] while Conservative Jews may or may not.[64]