Chefs and operators have turned to steam cooking as a way of creating hot healthful meals. The health-conscious public knows steaming is the way to retain nutrients and provide a healthy meal. Cooks look to steam to meet the demand and because of its versatility in preparing many different items.

Steam is an efficient heating source for most equipment applications since steam can store a large amount of energy and release it all to a food product upon contact. It is also an effective cooking method because steamed foods heat rapidly without burning or damaging the final product. The temperature of steam when not under pressure is 212°F, the same temperature as boiling water.

Steam, however, has six times the heat potential when it condenses on a cool food product. This increased heat transfer potential is why steam is such an effective cooking medium. Consider the difference in cooking power between an oven and steamer in this example. You can put your hand in a 400°F oven and not burn yourself but put your hand over a boiling tea kettle and the 212°F steam will scald immediately. This report will focus on several popular types of steam equipment

Steamers
Twenty years ago convection steamers were available but much less popular than pressure units. Today however, sales now favor the pressureless or convection steamers because of the advantages they offer. Safety is a prime concern and a pressureless steamer is perceived to be less of a hazard than a pressure model. With a pressureless model, cooks can open the cooking compartment at any time to check the product with no wait for depressurization. Better food appearance is another plus. Most chefs agree that the appearance and texture of green vegetables cooked in a convection steamer is better than product prepared in a pressure model. Convection steamers are also better suited to cooking product directly from a frozen state than pressure models, which cook better with thawed product.

There are plenty of steamers on the market to choose from made by at least 10 different manufacturers. Each has its own selling points and specialized features but most do an adequate job of steaming. There are a wide variety of sizes of units on the market. They range from the small one-, two- or three-pan units to the large 16-pan multi-compartment models. The smaller size units—three to five pan models—are usually set on a countertop. The larger models are floor mounted with stands. Typical sizes are rated by capacity in steamtable pans (12" x 20"). It is important to note, however, that ratings are typically for shallow 21¼2" deep pans.

Most steamers are available in electric, gas or direct steam fired configurations (smaller steamers may only be available in electric heat). Direct steam is the most economical if clean steam is available in the operation. Steam is clean if there are no chemicals added to prevent use with food. Electric or gas fired steam boilers work well and produce similar results.

Manufacturers continue to improve their convection steamers making them efficient with user-friendly features.

For efficiency, manufacturers are improving units to use less water and less energy while delivering the energy needed for fast steam cooking. User-friendly features include easy-to-use controls and warning lights to tell you when to delime. Deliming is the periodic maintenance needed almost everywhere to remove mineral deposits from the water. Typically neglected, deliming is the most frequent source of a service call according to service agencies. If deliming is not done when needed, the steamers will not operate at full efficiency and will, at some point, shut down altogether. The built-in warning light offered by a few manufacturers should save some operations from hefty service bills.

Steam Kettles
Steam jacketed kettles are pressure vessels that take advantage of the high rate of heat transfer steam cooking offers. A steam kettle is a double boiler with both vessels welded together so that no steam escapes when heated and pressurized. It is important to observe, however, that it is conduction with the heated surface of the kettle that actually heats and cooks product not direct contact with steam. As mentioned before, steam at atmospheric pressure is 212°F but when pressurized in the kettle jackets at 15 pounds of pressure, the temperature rises to about 250°F, hot enough properly cook food.

Even though a kettle cooks at a relatively low temperature, at least two-thirds, or in many cases the entire kettle surface, is being heated at a constant temperature. Unlike cooking with a pot on a range where only the bottom surface is in contact with a heat source, much more of the product’s surface area is in contact with heat. The temperature is also completely uniform throughout the entire jacketed surface of the kettle, meaning no hot spots to scorch the pan or product.

Kettles range in size from small countertop or table-mounted models and as small as one-quart to 100-gallon or larger capacity models for larger institutional facilities. The sizes used most in operations are countertop five and 10 quart models and floor mounted 10 to 40 gallon units.

When choosing the kettle size for your operation, remember that the working capacity is approximately 75% of the actual kettle’s rated capacity.

For example, if exactly 10 gallons of soup need to be prepared, a 10 gallon kettle will not do it. Kettles are not inexpensive but moving up in size is not costly, so it’s more economical to buy a single, larger kettle than to buy two smaller units. Electric and gas self-contained units are available as well as direct steam models. Self-contained units use a sealed water jacket for making steam heated by internal gas or electric burners.

In addition to the heating source, there are also several other kettle options to consider. Two of the most popular are the tilting mechanism and the draw-off valve. Tilting kettles are the standard with the smaller models, under 20 gallons, but larger units are available with tilting or stationary kettles. Tilting models generally make unloading product and cleaning easier. Draw-off valves at the bottom of larger kettles also make unloading product easier. Covers, pasta baskets and other accessories can be purchased if needed.

Steamer Ovens
The steam ovens are really two pieces of equipment in one: An oven and a steamer. The units look like convection ovens and come in a variety of sizes holding steamtable pans or baking sheet pans. Some are stackable like convection ovens. In the steaming mode, the units make their own steam in a self-contained boiler and cook like a convection steamer. According to many operators, they bake and steam food quite well.

Steamtables
Steamtables or hot food wells are used to hold hot food but unlike a steamer, no steam actually comes in contact with the food. It is important to note that contrary to popular belief, a steamtable is a dry heat source as far as the
product being warmed is concerned. Food held in a steamtable drys out easily and should be held covered if not used rapidly. Food wells are filled with water and heated to produce atmospheric steam that conducts heat efficiently to the bottom of the food pans in the well. Although many hot food wells on the market can be operated “wet or dry” they operate more effectively wet because of the heat transfer discussed previously.

Hot food wells, sometimes called bain maries, can operate with direct steam, gas or electric heating sources. Almost all commercially available hot food wells are designed only to hold hot food hot. They are not designed to warm food and do not have the heating power to do so.