Types: The three major models of steamers are pressure, pressureless (convection) and connectionless. The first utilizes from 5 to 15 lbs. of pressure per square inch (PSI) and cooks at 228°F. to 250°F. Generally speaking, low-pressure steaming units offer lower operating cost and higher productivity than pressureless units when preparing single items. Pressureless steamers cook at 0 PSI and 212°F. Heat is transferred via the convection of steam. Unlike pressure cookers, pressureless steamers put steam in direct contact with food products. Another difference is that pressureless steamer doors can be opened for checking or seasoning food at any time. These units are generally smaller, and cook more slowly than pressure steamers. Connectionless units are most often used by small- and medium-sized operations that lack water utilities or drains. Cook times are longer, but utility costs are lower.
Combi ovens use convection, steam and a combination of the two. This versatility allows users to control the moisture level of foods being cooked, while also substituting for multiple pieces of equipment.
Steamers and combis are now available in boilerless and steam generator versions. While steam generator ovens utilize a tank to boil large quantities of water for steam production, newer boilerless units have a single burner and inject smaller amounts of water directly on heating elements to create steam.
Capacities/Footprints: Combi ovens can actually save kitchen space by combining the functions of two or more pieces of equipment into one. Operators can also double-stack these units, providing more production capacity in a smaller footprint. Countertop and small floor-model steamers work well in lower-volume foodservice facilities. Large floor-model units are designed for high-volume operations. Smaller steamer models will typically accommodate three to five 12" X 20" X 2½" steam pans. Most larger units will accept both sizes, generally holding 14 12" X 20" X 2½" steam pans and seven 18" X 26" sheet pans.
Energy Source(s): Combi ovens that run on electricity require 3.9 kw and 208V for smaller, countertop units and as much as 75 kw and between 208V and 220V for larger models. Gas units range in Btu requirements from 45,500 to more than 170,000.
Energy Star-rated steamers must meet a minimum cooking efficiency of 50 percent for electric units and 38 percent for gas, while also meeting maximum idle energy rates for 3-, 4-, 5- and 6-pan sizes. Electric Energy Star-rated steamers can save 6,270 kwh annually, while gas units save 45 MBtu each year.
Standard Features: Some combi models offer a variety of programming options to control both cooking temperatures and humidity levels for specific products. The majority of combi oven models, however, come equipped with a trio of standard settings. One is fanforced pressureless steam, where water is injected into the oven. The second basic setting is combination mode. This blends steam with forced-air convection, providing moist heat. The third setting is straight convection, or hot air mode, which dry-cooks pizza.
New Features/Technology/ Options: One manufacturer introduced a new gas model featuring an open burner flame located directly inside the oven chamber, offering direct energy transfer, instant temperature results and a 50-percent increase in energy efficiency. A smoking feature on one model works with both hot and cold food items. Another manufacturer introduced a barcode scanner and software kit that foodservice operators can load with individual cooking recipes for simpler oven operation.
Prime Functions: A combi oven combines three cooking modes: steam, hot air and combi cooking, which melds hot air with superheated steam. The moisture maintains flavor and nutrients in food products, while the hot air speeds cooking. Combi ovens can also replace holding units, proofers or slow cookers when used at low-heat settings.
Key Kitchen Applications: Combi ovens steam, poach, roast, broil, bake and rethermalize. These units offer faster cooking with reduced shrinkage for menu items.
Purchasing Guidelines: Use the following rule of thumb to determine the appropriate number of compartments: 0 to 200 meals per hour require a single 1-compartment steamer. For 200 to 400 meals per hour, a single 2-compartment unit is appropriate. Operations producing from 400 to 600 meals per hour will need one 3-compartment unit. And, to prepare 600 to 800 meals per hour, operators need either one 4-compartment or two 2-compartment units.
Maintenance Requirements: Operators should follow a regular cleaning schedule for equipment that uses water and/or steam.