Steamers are becoming standard equipment for all types of kitchens. Once found only in institutions, steamers, with their wide range of sizes and types, have moved into delis, coffee shops, family restaurants, white tablecloth operations, hotels, schools, colleges, and hospitals.
There are many options for the operator who wishes to use steam to cook or heat food: high-pressure steamers, low-pressure steamers, pressureless steamers, and combination units of various types. Sizes range from small countertop units suitable for a deli or small restaurant to large models that hold several full-sized steam table pans at one time. Operators like to use steam because it’s quick; preserves flavor, texture, and color better than most other methods; and reduces shrinkage from cooking. In addition, it preserves nutrients better than most forms of cooking. And it’s energy efficient.
Since steam cooking is moist cooking, it doesn’t strip away moisture from food. That keeps yield high. The American Gas Association says the yield is five to six percent more than other cooking methods, across a broad range of foods. Because moisture stays in the food, so do vitamins and minerals. These characteristics contrast with boiling, where a large portion of those nutrients are discarded with the cooking water.
How Steam Cooks
Steam is quicker and more energy efficient than most cooking methods because of the way it works. Steam contains more heat than water of the same temperature. As a result, there’s more heat released when steam turns back into water.
It’s when the steam hits the food that you actually get the efficiency of all that heat being generated. The heat is released when the steam contacts a surface cool enough to make the vapor condense back to water. The greater the difference in temperature between the food cooking and the resultant steam, the faster the heat is released. Air is a problem in steaming. When air is mixed with the steam, it forms an insulating layer around the food that interferes with the transfer of heat from the steam.
There are two methods for eliminating this air layer, both employed in foodservice steamers: using steam under pressure and stripping the air layer away with convection currents. When steam is pressurized, it gets hotter, so pressurized steam cooks faster than unpressurized steam without any extra cost in energy.
Types of Steamers
There are five basic types of steamers: high pressure, low pressure, pressureless, combination pressure/pressureless, and combination oven/steamers.
- High-pressure steamers are extremely fast and are found where quick cooking is needed. They are smaller units, generally used for smaller batches of foods, especially vegetables, and for reheating frozen prepared foods.
These steamers gain their speed from three factors. One is the greater heat generated by placing steam under pressure. There is little air in the steam, so a cool layer does not form around the food. And the steam does not condense out into a cool water layer on the surface of food and insulate it from the heat in the chamber.
- Low-pressure steamers are found primarily in institutions, although a number of hotel kitchens and caterers use them. Low-pressure units are generally larger pieces of equipment, holding as much as four full-sized steam table type trays.
Although low-pressure steamers are not as fast as the high-pressure type, since they hold more they are able to turn out greater volumes of food. Although food that would take eight minutes in a high-pressure steamer might take 15 or 16 minutes to cook in a low-pressure unit, the larger volumes of the latter can quickly make up the difference in high production.
- Pressureless steamers have been gaining popularity. They can be opened and food removed at any point during the cooking cycle, unlike pressurized steamers, which must have the pressure relieved before the doors can be opened.
Pressureless steamers are fast because they are convection to strip away cool layers of air and moisture from the food. They obtain that convection in one of two ways. Some manufacturers use a fan to force the steam around the cooking compartment, just as in a convection steamer. Others use the placement of steam jets so they create a similar effect.
- A pressureless steamer must have a vent to permit steam to flow out of the unit. In some types, the steam passes through a condenser which turns most of it back to water. In others, the steam is exhausted directly into the air around the unit, and it should be placed under a ventilation hood to reduce steam and heat in the kitchen.
The ability to open the steamer door at any time in the cooking cycle makes the pressureless steamer the most versatile. Several foods with different cooking times may be placed in the steamer. Because steam is continually exhausting from the steamer, there is no intermingling of odors or flavors. Food may be added at any point in the cycle.
However, the pressureless steamer is not as energy efficient as units using pressure since more steam must be generated. Pressure steamers generate steam only to maintain the heat and pressure in the cooking chamber. Pressureless steamers must generate heat continuously to replace that lost by venting to the outside.
- The newest steamer is the combination pressureless steamer and convection oven. Although this European concept took off slowly in this country, more operations are adding such a unit to their kitchens. It permits straight convection steaming, straight roasting or baking, or baking or roasting in moist heat.