Kosher foods are those that conform to the regulations of the Jewish Halakhic law framework, kosher meaning fit or allowed to be eaten. A list of some kosher foods are found in the book of Leviticus 11:1-47. There are also certain kosher rules found there.
Reasons for food not being kosher include the presence of ingredients derived from non-kosher animals or from kosher animals that were not slaughtered in the ritually proper manner , a mixture of meat and milk, wine or grape juice (or their derivatives) produced without supervision, the use of produce from Israel that has not been tithed, or the use of non-kosher cooking utensils and machinery.
You need not be Jewish to design a kosher kitchen. Nevertheless, a Rabbi is an expert on Jewish Law and would be perfect to design a kosher kitchen.
Although you may not be a Rabbi, the best place to begin is to learn a little bit about kosher foods, which break down into three basic categories: meat, dairy, pareve - a Hebrew word, meaning "neutral, neither meat or dairy."
Meat and meat products are anything that is animal. Dairy refers to milk and milk products, like ice cream, yogurt, cheese and butter. You might think that eggs belong in the meat category because they come from chickens, but, they are considered pareve.
Other pareve products include margarine, pasta, rice and other grains, fruit and vegetables. Fish is also considered pareve. Many foods in the supermarkets sold in boxes or cans may have the word pareve written on them. The same cans or boxes could also have a "K" with a circle or a "U" with a circle. These symbols indicate that the food has been prepared in accordance with kosher laws. The reason for categorizing food is that meat and dairy are not supposed to be mixed in the same meal. For example, if a meat dinner is prepared and bread is served, the bread must not have been made with milk or butter. No part of the meal can have any food made with dairy products. If coffee is served at the same meal, you may not use milk or cream. A milk substitute is allowed if it has been certified as a kosher non-dairy product.
The laws also govern the use of dishes, utensils, pots and pans. You may not use the same items for meat and dairy. If you prepare a cheese omelet in a frying pan, that pan can only be used for dairy preparation. You could not use it for minute steaks. The same fork or knife used for eating meat products cannot be used for eating cheese souffles or spreading butter.
This means that a kosher kitchen will have two sets of flatware, two sets of dishes, two sets of pots and pans, two sets of prep utensils, two sets of knives and so on and so on.
Now you get the idea of the storage that will be needed. Of course, if you have a tight space to design, the challenge becomes even greater.
The ultimate kosher kitchen is really two kitchens, so if space and budget permit yo to do so, try to create a double kitchen design for your kosher clients. The next best thing is to have two kitchens in one, with special attention paid to appliances, sinks and countertops.
One refrigerator/freezer is generally acceptable to kosher clients, although some may desire to keep there meat in a separate freezer. Obviously, the available space in the customer's kitchen will dictate how many refrigerators you plan to have. Sometimes, the refrigerator can be placed so that it serves as a divider between the meat and dairy kitchen. Cooking equipment like ovens, cooktops and ranges prove to be less problematic in kosher kitchens. Once again, if you have the space for two cooking systems, that's the best option. You may use any standard combination of cooking appliances, including a microwave oven. Make sure you have made provisions for the proper clearances and distances for functional purposes as you would any other kitchen.
The clean-up center is a little more difficult to plan in kosher kitchens. The best possible situation is to have two sinks and two dishwashers. Two dishwasher would take priority over two sinks. If the conditions are limited to only one sink, then two dishwashers, one for meat and one for dairy, will be helpful. The type of sink that is used is critical. Kosher laws state that only stainless steel products can be made kosher by using a process with boiling water. This does not mean that you can't use other products like solid surfacing or enameled cast iron. If you have two sinks, one for meat and one for dairy, you may use any type of sink material.
If you are using only one sink, and it is not stainless steel, you must use a liner of some sort, like a plastic dish pan. You would use the regular sink for meat and the plastic dish pan for dairy. The key issue in choosing the sink is how porous the material is. Countertop material is a very important issue in kosher kitchens. Of course, you really can use any material, as long as the food does not come in direct contact with the surface.
If kosher customer butcher their own meat and then place it directly on the countertop, that section of the countertop can only be used for meat products.
The same is true for dairy products, such as rolling dough, which are made with butter on a section of the countertop. Separate boards should be used for cutting meat or rolling dough. The use of stainless steel countertops could help yo avoid some of these problems.
Wooden countertops, however, would never pass the porosity test.