A kosher certification agency is an organization of Rabbis, food technologies, and field supervisors with the expertise and resources to execute the Laws of Kashrus. It is responsible for assuring Kosher consumers that food products and ingredients meet all kosher requirements. Once these requirements have been met, a letter of certification is issued to the manufacturer who is then authorized to advertise its kosher status, and display the kosher symbol and promote the product as kosher. All kosher certification agencies are not identical. It is essential that the kosher certification agency has widespread acceptability so that a product bearing its symbol can be marketed to as wide an audience as possible. The manufacturer can then take advantage of the rapidly growing demand for kosher food.
While raw food may not be cooked on the Sabbath, food that was already cooked beforehand may be kept warm until mealtime. On some holidays, food may be cooked fresh, but turning the heat on is prohibited. In the past, the problem could be solved simply by lighting a stove or oven before the day began, and using its heat over the course of the day. In recent decades, however, appliance manufacturers have instituted a safety feature that automatically shuts off the heat after a number of hours. This renders the appliance useless for those who observe these religious laws. When an oven is in Shabbat mode, the standard six- or twelve-hour automatic shutoff is overridden, and all lights and displays (for example, a light that might go on when the door is opened) are disabled.
With some Sabbath mode ovens that are controlled using a keypad to set the temperature, there is a random delay triggered after a button is pressed before the temperature change takes place.