A steam-jacketed kettle is similar to a double boiler and cooks large quantities of food by using steam heat. It is designed with both an inner and outer steel wall that cooks the contents inside by releasing steam into the space between the walls. These devices are often used to cook foods like stock, gravy, sauce, or soup, and may be powered by electricity or gas. They come in various sizes, for installation on the floor, countertop, or wall. Steam-jacketed kettles are often used in restaurants and industrial kitchens, where very large amounts of food are prepared daily.
All the different styles and sizes of steam-jacketed kettle use steam to cook the contents inside. Most are made from stainless steel, and usually, the steam jacket is permanently filled with treated, distilled water. Since steam encapsulates most of the kettle, it may cook more evenly than a traditional stock pot because it offers a more uniform cooking surface. It also tends to warm contents more quickly than a traditional pan, heated primarily from the bottom.
Electricity, gas, or both may supply power to the kettle. A gas fired kettle requires a gas hook up source to operate and may also require electricity if it has automatic ignition. Gas kettles also require a kitchen ventilation system for safety.
A steam-jacketed kettle can be tilting or stationary. A kettle that is meant for floor use is usually stationary and may have legs that can be adjusted to different heights so that cooks can reach the pot. There are also smaller sized kettles, wall-mounted or for countertop use, that can be manually tilted to make it easier and safer to remove the contents. Most kettles also have a draw off valve.
Often, a steam-jacketed kettle is used for industrial cooking purposes. They are found in hotels, and schools and on military ships and bases. This kind of kettle can cook large amounts of stew, pasta, or chili and can also be used to braise meat, cook dessert, or reheat various foods. Steam-jacketed kettles tend to be popular for institutional use because they require less stirring, can simmer longer-cooking recipes, and are less apt to burn food.