The typical commercial kitchen used to be fitted with one or more deck ovens. They were just one level high and were sized to take two or more of the standard 18 X 26-inch rectangular sheet pans. The difference between a baking oven and a roasting oven was simply the height of the drop-down door. Roasts take up more vertical space than baked goods. Two or more were stacked to save space, but they still took up a lot of room. Operations that did a lot of their own baking could opt for a ferris wheel type oven that produced more per square foot than the cumbersome decks.
The oven usually supplied under the range top was used for miscellaneous menu items and seldom for more than one roast at a time. Temperatures inside a range oven, just as in your oven at home, are not precisely consistent even though they are thermostatically controlled. The thermostat probe senses only a small parcel of the air in the oven and warm air rises. The re-arrangement of the shelf position, depending on the food product, was a constant chore.
Then came the invention of the forced convection oven. An electric fan circulates the heated air throughout the cavity. Unlike the one-layer deck oven, the convection oven allows several rack positions and all the food is cooked in virtually the same time. The idea was to provide more oven capacity in less floor space, and the concept worked. However, two other extraordinary side benefits accrued. Foods can be cooked at temperatures about 50[deg.] F lower and in about half the time.
It was determined that as food is cooked in a static hot air oven, the water molecules at its surface are constantly evaporating, producing a film of moist cool air. This boundary layer is an insulating barrier that slows down heat transfer. The high speed wind in a convection oven continuously sweeps this blanket away for faster, lower temperature cooking.
This method does wonders for meats such as roast beef because of two factors.
- First, the lower heat dramatically reduces shrinkage. (The higher the heat, the greater the shrinkage). Meat is mostly water and as the connective tissue shrink, they literally wring the natural juices from the product.
- Second, the meat is subjected to heat for a shorter period of time which means less loss of volatile flavors and nutrients due to evaporation.
By the way, the versatile convection oven is also used for baking. There are many brands and sizes from cabinets that take a roll-in rack to small countertop units.
But, if an operator is really serious about roast beef, there is an even better procedure. It’s called slow roasting. Instead of heating up an oven to 400[deg.] F, the slow roast cabinets cook at only about 200[deg.], then automatically turn themselves down to a safe holding temperature of 140[deg.]. The roasts can be left in the oven until ready for serving or can be transferred to other holding cabinets or refrigerated for later use. A common procedure is to start the roasts before the kitchen closes at night. They’ll be ready for serving in the morning.
Since the heat is so low, there is very little shrinkage and the product retains most of its natural juices and flavor. But something more magical also happens.
Meat is mostly water held together by a network of connective tissues. There are two types of these fibers. One is called “collagen” with fibers of varying lengths which appear white in quantity. The other is “elastin” and is yellow in color with its fibers in branches.
Older animals contain more of these tissues and are tougher. Animals that have been allowed exercise also have more of these fibers and are graded lower. However, there is a natural process that actually turns the tougher collagen fibers into gelatin. This tenderizing action takes place at low cooking temperatures that allow the natural enzymes in the meat to soften the fibers. The elastin fibers stay in place so that a firm yet tender product results.
There is no cooking procedure that attacks the elastin fibers. Not even boiling or steaming. However, commercial tenderizers do digest both types of connective tissues and will produce a mushy product if left on too long. They should be used on flat cuts, such as steaks, just before cooking.
Components And Characteristics Of The Oven
- Convection ovens can be ordered with a special set of optional controls which include a second timer and thermostat. One set is for the cooking time and temperature and the other for holding.
- The slow cook and hold cabinets, designed specifically for that purpose, are available with probes that measure the internal temperature of the meat. Some have electronic digital readouts that constantly display the internal temperature of the roast as well as the temperature of the air in the cabinet.
- Some cabinet ovens are fitted with casters for mobility. This allows freedom in kitchen planning so that they can be wheeled into position when needed or stored out of the way while other tasks take their space. These electrically operated ovens do not have to be placed under ventilation hoods.
- Smaller models are available with a cutting board top and heat lamps above. The complete carving station will display one roast under the showmanship and safety of the infrared lamps, while down below a second roast can be cooking or just lying in wait. Heated pans can be provided for hot au jus and an electric slicer and portion scale may also be needed.
- Instead of one tall cabinet, two half-size units with separate controls can be stacked for further versatility. Roasts can be holding in one while pies are being baked in the other.
Using The Oven
The most common cause of what we loosely term “food poisoning” is the mis-handling of rare roast beef. The use of a meat thermometer is a must to be sure that the internal temperature is at least 145[deg.]. The controls supplied with the commercial convection or slow cook and hold oven are extremely reliable, with more and more use of sophisticated electronic sensors and digital readouts.
For institutional use, central commissaries and larger operations, there is another, relatively new, way to cook roast beef and have it come out on the rare side of doneness that many customers prefer.
This system, approved by the USDA, vacuum packages the roasts. They are lowered into a tank of heated water at a very specific temperature for a pre-determined time and the packages are not allowed to touch each other.
The controls and monitoring equipment mark the time within one minute and the water temperature in the tank does not vary more than one degree. After a 195-minute soak, the internal temperature will be only 128[deg.] F, providing a red and rare roast beef. The process does assure the thermal destruction of common Salmonella, making it safe for human consumption.
After the required cooking time, the hot water is promptly drained from the tank and chilled water is circulated to stop further cooking. The beef has a long storage life. It can be kept for up to three months at about 30[deg.] or, if frozen, it can be held longer.