What Is Kosher?
Meat & Milk
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Central to maintaining the laws of keeping kosher is the separation of meat from milk. The prohibitions against mixing them are very strict, in some respects more so than other Kashrut regulations.
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This is why it is necessary to have different sets of cutlery, crockery, cooking utensils and washing-up-bowls for meat and dairy meals. A dishwasher should be used solely for meat or milk dishes but not both.
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Food that is neither meat nor dairy is called 'parev' (neutral). Parev utensils, like salad bowls or drinking glasses, can accompany both milk and meat meals. Ordinary non-absorbent glass may be designated parev. But Pyrex and other oven proof dishes glass must be designated either meat or milk.
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We not only avoid mixing meat and milk at the table. We also abstain from eating dairy foods after meat until some time has elapsed. The Shulchan Aruch, the Code of Jewish law, actually records two traditions, one of waiting for one hour (which the Dutch still adhere to) and one for six. The prevailing Anglo-Jewish custom is to wait three hours. In the case of eating meat after milk, the same interval applies only after eating hard cheese.
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In order to prevent confusion, bread should always be made parev, and therefore must be made without butter or milk.
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Fish & Meat
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Another rule is not to eat fish and meat together - but for a different reason to that of meat and milk. It is simply that the Rabbis, advocates of a healthy lifestyle, believed it physically harmful. Therefore one shouldn't use Worcestershire Sauce, which is made from anchovies, in the preparation of a meat dish.
It's permissible to eat meat immediately after fish and vice versa, for example a salmon canapé after a cocktail sausage. But it is the custom to cleanse the palate first by having some bread or a drink.
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Eggs
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Because of the prohibitions against eating blood, it is customary to check eggs once opened and before cooking, so as to reject any with blood spots. There's no requirement, however, to check them before hard-boiling. White eggs on sale commonly have fewer blood spots than brown ones but not for any biological reasons: it is because in the factory ‘candling’ process, white eggs with bloodspots are easier to detect and thus are rejected before they reach the shops.
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Fish
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While there are a few available varieties of kosher meat or poultry; this is not true of fish. To comply with kosher requirements, a fish must have fins and easily detached scales. The scales of a sturgeon are extremely hard to remove, hence it is non-kosher, as is its precious roe, caviar. All shellfish, eels, shark, monkfish, huss and catfish fail the kosher test. Fresh or frozen fish should be bought with the skin on so you can check the scales.
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Milk
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Since it is not possible to distinguish kosher milk (milk from a kosher animal) from non-kosher milk, Rabbinical law requires that milk be supervised from the point of milking until it is bottled in order to guarantee that it comes from a kosher animal. In countries where the source of milk offered for sale is guaranteed by civil law (such as the UK), some authorities rule that all milk is guaranteed as kosher and need not be supervised. Supervised kosher milk (Chalav Yisrael) is widely available nowadays in the major centres of Jewish life.
Cheese
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When it comes to cheese though, the rules are tighter. All cheese must be Rabinically certified. This is because the curdling agent, the rennet, is often derived from an animal source - usually a calf's stomach. The Rabbis in the Talmud ruled that all cheese must come from a supervised source, even where the rennet was made from herbs. As a result, vegetarian cheeses cannot be used unless they have a Rabbinic seal.
Wine
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Wine and grape juice must come only from a Rabbinically approved source. The Sages put a ban on non-Jewish wine primarily as a safeguard against intermarriage, believing that by drinking-out one might end up dating-out. Hence products like brandy and wine vinegar must also carry a Rabbinic seal.
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As it happens, non-kosher ingredients used in in the manufacture of non-Jewish wines, such as bull's blood for colouring or more commonly, isinglass, a ‘fining’ agent which comes from a sturgeon, another reason for avoiding them.
Bread
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Bread which is not kosher certified is not permitted because it may be made with fats, emulsifiers or improvers of animal origin. Release agents used to grease production equipment may be non-kosher and the equipment itself may be used for non-kosher products. See list of KLBD Supervised Bakeries.
One should always buy Pas Yisrael bread - Jewish baked kosher bread - whenever possible. Pas Palter - bread produced in a non-Jewish commercial bakery with kosher ingredients - may be purchased when no similar Pas Yisrael product is readily available, provided it is kosher certified.
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Processed Foods
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In the 21st century, Kashrut has had to contend with a whole new challenge; processed foods. Thanks to the efforts of kosher food technologists, thousands of products on the shelves have been cleared for use by Jewish consumers. Increasingly, more products carry a kosher label - like the KLBD, Kosher London Beth Din, logo introduced a few years ago. Many others listed have been approved after rigorous inspection of the ingredients and the procedures used in manufacturing them.
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Each ingredient and food additive has to be individually checked to ensure it does not derive from a non-kosher source. Many seemingly innocent products such as yoghurt may contain gelatine. Spices may contain stearic acid salts and even breakfast cereal may contain glycerine (eg Raisin Splitz), all of animal origin. Even where the ingredients are kosher, the product may still be non-kosher because of other unlisted agents used in its manufacture - such as release agents used to grease the production line.
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Even when a product is suitable for vegetarians, it may still be non-kosher if the factory has prepared it on equipment which has been previously used for a meat meal. Thus, with the ever increasing sophistication of food technology, The Really Jewish Food Guide has become an essential handbook for every Jewish Home.
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Biscuits
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These are usually made with non-kosher margarine. Those made with butter may still not be kosher, as tins may be greased with non-kosher fat and no indication of this will appear on the label. Cakes present the same problems. In common with all other cooked products, cakes and biscuits whose own ingredients are perfectly acceptable, may be cooked in tins or pans used for non-kosher products or in ovens together with non-kosher products. For these reasons, each item must be considered individually.
Margarines
They contain fats and emulsifiers which may be of animal origin; even the manufacturers of ‘vegetarian’ margarine cannot always guarantee that the source of their emulsifier is vegetable. Only margarine under Rabbinical supervision can be used.
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