Kashrut is the body of Jewish law dealing with what foods can and cannot be eaten and how those foods must be prepared. The word "Kashrut" comes from the Hebrew meaning fit, proper or correct.

The word "kosher," which describes food that meets the standards of kashrut, is also often used to describe ritual objects that are made in accordance with Jewish law and are fit for ritual use. Food that is not kosher is referred to as treif (literally torn).

Kosher is not a style of cooking and therefore there is no such thing as "kosher-style" food. Any kind of food - Chinese, Mexican, Indian, etc. - can be kosher if it is prepared in accordance with Jewish law. At the same time, traditionalJewish foods like knishes, bagels, blintzes and matzah ball soup can all be treif if not prepared in accordance with Jewish law.

Who Do Jews Observe the Laws of Kashrut?
Is Keeping Kosher Difficult?
Kashrut Fundamental Rules
The Smaller Details
Kashrut Certification

Why Do Jews Observe the Laws of Kashrut?

Many modern Jews think that the laws of kashrut are simply primitive health regulations that have become obsolete with modern methods of food preparation. There is no question that some of the dietary laws have beneficial health effects. For example, the laws regarding kosher slaughter are so sanitary that kosher butchers and slaughterhouses are often exempted from USDA regulations.

However, health is not the main reason for Jewish dietary laws and in fact many of the laws of kashrut have no known connection with health. To the best of our modern scientific knowledge, there is no reason why camel or rabbit meat (both treif) is any less healthy than cow or goat meat. In addition, some of the health benefits derived from kashrut were not made obsolete by the refrigerator. For example, there is some evidence that eating meat and dairy together interferes with digestion, and no modern food preparation technique reproduces the health benefit of the kosher law of eating them separately.

The short answer to why Jews observe these laws is because the Torah says so. The Torah does not specify a reason for these laws but for an observant Jew there is no need for a reason - Jews show their belief and obedience to God by following the laws even though they do not know the specific reason.

In the book To Be a Jew, Rabbi Hayim Halevy Donin suggests that kashrut laws are designed as a call to holiness. The ability to distinguish between right and wrong, good and evil, pure and defiled, the sacred and the profane, is very important in Judaism. Imposing rules on what you can and cannot eat ingrains that kind of self control. In addition, it elevates the simple act of eating into a religious ritual. The Jewish dinner table is often compared to the Temple altar in rabbinic literature.

Is Keeping Kosher Difficult?

Keeping kosher is not particularly difficult in and of itself; what makes keeping kosher difficult is the fact that the rest of the world does not do so.

The basic underlying rules are fairly simple. If you buy your meat at a kosher butcher and buy only kosher certified products at the market, the only thing you need to think about is the separation of meat and dairy.

Keeping kosher only becomes difficult when you try to eat in a non-kosher restaurant or at the home of a person who does not keep kosher. In those situations, your lack of knowledge about your host's ingredients and the food preparation techniques make it very difficult to keep kosher. Some commentators have pointed out, however, that this may well have been part of what G-d had in mind: to make it more difficult for us to socialize with those who do not share our religion.

The Fundamental Rules of Kashrut

Although the details of kashrut are extensive, the laws all derive from a few fairly simple, straightforward rules:

Certain animals may not be eaten at all. This restriction includes the flesh, organs, eggs and milk of the forbidden animals.
Of the animals that may be eaten, the birds and mammals must be killed in accordance with Jewish law.
All blood must be drained from the meat or broiled out of it before it is eaten.
Certain parts of permitted animals may not be eaten.
Meat (the flesh of birds and mammals) cannot be eaten with dairy. Fish, eggs, fruits, vegetables and grains can be eaten with either meat or dairy. (According to some views, fish may not be eaten with meat).
Utensils that have come into contact with meat may not be used with dairy, and vice versa. Utensils that have come into contact with non-kosher food may not be used with kosher food. This applies only where the contact occurred while the food was hot.
Grape products made by non-Jews may not be eaten.

The Details

Animals That Cannot be Eaten

Of the "beasts of the earth" (which basically refers to land mammals with the exception of swarming rodents), you may eat any animal that has cloven hooves and chews its cud. Lev. 11:3; Deut. 14:6. Any land mammal that does not have both of these qualities is forbidden. The Torah specifies that the camel, the rock badger, the hare and the pig are not kosher because each lacks one of these two qualifications. Sheep, cattle, goats and deer are kosher.

Of the things that are in the waters, you may eat anything that has fins and scales. Lev. 11:9; Deut. 14:9. Thus, shellfish such as lobsters, oysters, shrimp, clams and crabs are all forbidden. Fish like tuna, carp, salmon and herring are all permitted.

For birds, the criteria is less clear. The Torah lists forbidden birds (Lev. 11:13-19; Deut. 14:11-18), but does not specify why these particular birds are forbidden. All of the birds on the list are birds of prey or scavengers, thus the rabbis inferred that this was the basis for the distinction. Other birds are permitted, such as chicken, geese, ducks and turkeys.

Of the "winged swarming things" (winged insects), a few are specifically permitted (Lev. 11:22), but the Sages are no longer certain which ones they are, so all have been forbidden.

Rodents, reptiles, amphibians, and insects (except as mentioned above) are all forbidden. Lev. 11:29-30, 42-43.

As mentioned above, any product derived from these forbidden animals, such as their milk, eggs, fat, or organs, also cannot be eaten. Rennet, an enzyme used to harden cheese, is often obtained from non-kosher animals, thus kosher hard cheese can be difficult to find.

Kosher Slaughter (Shechitah)

The mammals and birds that may be eaten must be slaughtered in accordance with Jewish law. (Deut. 12:21). We may not eat animals that died of natural causes (Deut. 14:21) or that were killed by other animals. In addition, the animal must have no disease or flaws in the organs at the time of slaughter. These restrictions do not apply to fish; only to the flocks and herds (Num. 11:22).

Ritual slaughter is known as shechitah, and the person who performs the slaughter is called a shochet, both from the Hebrew root Shin-Chet-Tav, meaning to destroy or kill. The method of slaughter is a quick, deep stroke across the throat with a perfectly sharp blade with no nicks or unevenness. This method is painless, causes unconsciousness within two seconds, and is widely recognized as the most humane method of slaughter possible.

Another advantage of shechitah is that ensures rapid, complete draining of the blood, which is also necessary to render the meat kosher.

The shochet is not simply a butcher; he must be a pious man, well-trained in Jewish law, particularly as it relates to kashrut. In smaller, more remote communities, the rabbi and the shochet were often the same person.

Draining of Blood

The Torah prohibits consumption of blood. Lev. 7:26-27; Lev. 17:10-14. This is the only dietary law that has a reason specified in Torah: we do not eat blood because the life of the animal is contained in the blood. This applies only to the blood of birds and mammals, not to fish blood. Thus, it is necessary to remove all blood from the flesh of kosher animals.

The first step in this process occurs at the time of slaughter. As discussed above, shechitah allows for rapid draining of most of the blood.

The remaining blood must be removed, either by broiling or soaking and salting. Liver may only be kashered by the broiling method, because it has so much blood in it and such complex blood vessels. This final process must be completed within 72 hours after slaughter, and before the meat is frozen or ground. Most butchers and all frozen food vendors take care of the soaking and salting for you, but you should always check this when you are buying someplace you are unfamiliar with.

An egg that contains a blood spot may not be eaten. This isn't very common, but I find them once in a while. It is a good idea to break an egg into a container and check it before you put it into a heated pan, because if you put a blood-stained egg into a heated pan, the pan becomes non-kosher.

Forbidden Fats & Nerves

The sciatic nerve and its adjoining blood vessels may not be eaten. The process of removing this nerve is time consuming and not cost-effective, so most American slaughterers simply sell the hind quarters to non-kosher butchers.

A certain kind of fat, known as chelev, which surrounds the vital organs and the liver, may not be eaten. Kosher butchers remove this. Modern scientists have found biochemical differences between this type of fat and the permissible fat around the muscles and under the skin.

Separation of Meat & Dairy

On three separate occasions, the Torah tells us not to "boil a kid in its mother's milk." (Ex. 23:19; Ex. 34:26; Deut. 14:21). The Oral Torah explains that this passage prohibits eating meat and dairy together. The rabbis extended this prohibition to include not eating milk and poultry together. It is, however, permissible to eat fish and dairy together, and it is quite common. It is also permissible to eat dairy and eggs together. According to some views, it is not permissible to eat meat and fish together, but I am not certain of the reason for that restriction.

This separation includes not only the foods themselves, but the utensils, pots and pans with which they are cooked, the plates and flatware from which they are eaten, the dishwashers or dishpans in which they are cleaned, and the towels on which they are dried. A kosher household will have at least two sets of pots, pans and dishes: one for meat and one for dairy. See Utensils below for more details.

One must wait a significant amount of time between eating meat and dairy. Opinions differ, and vary from three to six hours. This is because fatty residues and meat particles tend to cling to the mouth. From dairy to meat, however, one need only rinse one's mouth and eat a neutral solid like bread, unless the dairy product in question is also of a type that tends to stick in the mouth.

The Yiddish words fleishig (meat), milchig (dairy) and pareve (neutral) are commonly used to describe food or utensils that fall into one of those categories.

Note that even the smallest quantity of dairy (or meat) in something renders it entirely dairy (or meat) for purposes of kashrut. For example, most margarines are dairy for kosher purposes, because they contain a small quantity of whey or other dairy products to give it a dairy-like taste. Animal fat is considered meat for purposes of kashrut. You should read the ingredients very carefully, even if the product is kosher-certified.

Utensils

Utensils (pots, pans, plates, flatware, etc., etc.) must also be kosher. A utensil picks up the kosher "status" (meat, dairy, pareve, or treif) of the food that is cooked in it or eaten off of it, and transmits that status back to the next food that is cooked in it or eaten off of it. Thus, if you cook chicken soup in a saucepan, the pan becomes meat. If you thereafter use the same saucepan to heat up some warm milk, the fleishig status of the pan is transmitted to the milk, and the milchig status of the milk is transmitted to the pan, making both the pan and the milk a forbidden mixture.

Kosher status can be transmitted from the food to the utensil or from the utensil to the food only in the presence of heat, thus if you are eating cold food in a non-kosher establishment, the condition of the plates is not an issue. Likewise, you could use the same knife to slice cold cuts and cheese, as long as you clean it in between, but this is not really a recommended procedure, because it increases the likelihood of mistakes.

Stovetops and sinks routinely become non-kosher utensils, because they routinely come in contact with both meat and dairy in the presence of heat. It is necessary, therefore, to use dishpans when cleaning dishes (don't soak them directly in the sink) and to use separate spoonrests and trivets when putting things down on the stovetop.

Dishwashers are a kashrut problem. If you are going to use a dishwasher in a kosher home, you either need to have separate dish racks or you need to run the dishwasher in between meat and dairy loads.

You should use separate towels and pot holders for meat and dairy. Routine laundering kashers such items, so you can simply launder them between using them for meat and dairy.

Certain kinds of utensils can be "kashered" if you make a mistake and use it with both meat and dairy. Consult a rabbi for guidance if this situation occurs.

Grape Products

The restrictions on grape products derive from the laws against using products of idolatry. Wine was commonly used in the rituals of all ancient religions, and wine was routinely sanctified for pagan purposes while it was being processed. For this reason, use of wines and other grape products made by non-Jews was prohibited. (Whole grapes are not a problem, nor are whole grapes in fruit cocktail).

For the most part, this rule only affects wine and grape juice. This becomes a concern with many fruit drinks or fruit-flavored drinks, which are often sweetened with grape juice. You may also notice that it is virtually impossible to find kosher baking powder, because baking powder is made with cream of tartar, a by-product of wine making.

Kashrut Certification

The task of keeping kosher is greatly simplified by widespread kashrut certification. Approximately three-quarters of all prepackaged foods in the United States and Canada, at least, have some kind of kosher certification, and most major brands have reliable Orthodox certification.

The symbols of kashrut certification are all widely-accepted and commonly found on products throughout the United States. It is very easy to spot these marks on food labels, usually near the product name, occasionally near the list of ingredients.

The most controversial certification is the K, a plain letter K found on products asserted to be kosher. All other kosher certification marks are trademarked and cannot be used without the permission of the certifying organization. The certifying organization stands behind the kashrut of the product. But you cannot trademark a letter of the alphabet, so any manufacturer can put a K on a product. For example, Jell-O brand gelatin puts a K on its product, even though every reliable Orthodox authority agrees that Jell-O is not kosher.

It is becoming increasingly common for kosher certifying organizations to indicate whether the product is fleishig, milchig or pareve. If the product is dairy, it will frequently have a D or the word Dairy next to the kashrut symbol. If it is meat, the word Meat or an M may appear near the symbol. If it is pareve, the word Pareve (or Parev) may appear near the symbol (Not a P! That means kosher for Passover!). If no such clarification appears, you should read the ingredient list carefully to determine whether the product is meat, dairy or pareve.

Sources: Judaism 101

Jewish Dietary Laws (Kashrut): Overview of Laws & Regulations