The Inside Scoop on Compartment Steamers

It's hard to imagine a restaurant without some form of steam cooking, and there's probably nothing that will get you angry faster than a steamer that goes belly up on a busy Friday night. One of the advantages of a commercial steam cooker -- or compartment steamer -- is its ability to rapidly cook or heat large quantities of food.

Steam carries roughly six times the energy of boiling water, and transfers this energy to the food as the steam condenses on the food. And while this basic premise lies at the heart of the matter, there's much more to the world of steamers that you might not at first imagine. By learning a little more about these time- and labor-saving devices, we can make better choices that will keep the food flowing without breaking the bank.

Steamer Basics

Steamers come in a surprising variety of sizes, styles and capacities, from self-contained countertop steamers to large multicompartment wall- or pedestal-mounted steamers that can quickly fire up enough food to feed a small army. Steamers used in commercial kitchens fall in two basic categories: pressureless or "atmospheric" steamers, and pressure steamers. Pressureless steamers cook the food at near atmospheric pressure -- less than three psig (pounds per square inch gauge) [0-20 kPa] -- allowing the door to be opened to check on cooking progress. The trays are held in a compartment where the steam can freely circulate around them.

Pressure steamers allow the pressure to build within the cooking compartment to decrease cooking times. Low-pressure steamers are generally high-capacity and operate at 3-9 psig (20-62 kPa), whereas the high-pressure (10-15 psig [70-105 kPa]) steamers are typically lower capacity, but cook the food much faster. Since the cooking compartment is pressurized, it cannot be opened to check progress, and careful timing is essential to avoid overcooking the food. "Pressure steamers really are the dinosaur of the industry," says Victor Kong, a steamer expert with the Food Services Technology Center (FSTC) in San Francisco, "and you really only find them in institutional settings. They're more expensive, more complicated, and require more maintenance. They're also less forgiving of mistakes. Get distracted and leave the food in a bit too long, and the quality really suffers."

Conventional atmospheric and pressure steamers typically use a "boiler" to generate the steam, which is then fed to the cooking compartment. In the case of a pressure steamer, the steam is fed through a system of valves to maintain the proper cooking conditions. The boilers that generate the steam can be either gas-fired or electric. Alternatively, some units can use "house steam" either directly from a food-grade steam source, or via a heat exchanger to provide clean steam from a nonfood grade source.

The newer "connectionless" steamers are fast becoming the most popular designs in use. Unlike conventional steamers, the connectionless steamer has no "boiler" to generate the steam, but rather heats water within the cooking compartment to produce the steam. Rather than a direct connection to a water supply and condensate drain, the connectionless steamer requires only a standard electrical power outlet. Water is added as needed to the steamer, and replenished when a low level is indicated.

Another variation on the modern compartment steamer is the "convection steamer." Just as a convection oven can cook more rapidly by circulating hot air around the food, convection steamers can shorten the cooking time by circulating the steam through the steamer compartment. In addition, the circulating steam helps maintain a more even cooking environment under heavy loads.