Broiling is a traditional dry-heat cooking method which primarily uses radiant energy as the heat source. Air convection and conduction from the rack or pan supporting the meat contribute minor amounts of heat. Heat is conducted from the meat surface to the interior with the rate of heat transfer being proportional to the temperature difference between the outer surface and inner portion. A number of studies have reported the influence of broiling on meat quality (Cross et al., 1979; Carpenter et al., 1972; Batcher and Deary, 1975). Broiling temperture is related to the distance of the meat from the broiling unit, and thus affects the time required to cook the meat. In general, thin cuts are broiled so the heat can penetrate to the center of the cut before the surface is overcooked. Thicker cuts of meat (1 to 2 inches) are placed farther from the heat source to allow uniform cooking.

In contrast to broiling, meat cooked by microwave involves heat generated from within the meat through a series of molecular vibrations (Cross and Fung, 1982). Microwaves are high frequency radiations with the ability to ionize other compounds. Goldblith (1966) described the heating principle as an attempt by asymmetric dielectric molecules to align themselves with the rapidly changing alternating electric field. As microwaves penetrate the food they cause oscillation of polar molecules around their axes in response to reversal of the electric field that occurs 915 or 2450 million times/second. This oscillation creates intermolecular friction that cooks the food (Copson, 1975). Microwaves heat the entire volume of food simultaneously by conduction and direct molecular agitation. Consequently, heating rates can be greatly increases (Curnutte, 1980).

The amount of heat created with microwaves is complicated by a gradual decrease of intensity as the energy is absorbed by successive layers of material and by differing dielectric properties of the various materials. Even heating in the meat is further complicated by reflection and refraction of microwaves at interfaces between different food components and the influence of spatial arrangements of regions with high and low dielectric constants. Since meat is naturally nonhomogenous, hot spots may develop (Rosen, 1972).

The extent of heating with microwaves is affected by some of the same factors which influence doneness in conventional cooking such as initial temperature of meat, holding time, the specific and latent heats, and loss of moisture by evaporation. There are also factors specific for the microwave method of cooking. These include the dielectric properties of the meat, depth of penetraiton of the microwaves, dipolar molecular action, electromagnetic frequency of the oven used, the size and distribution of the load in the oven, shape of the food, and vapor pressure in the oven (Van Zange, 1973).

Excerpt from Riffero, Linda Marie. 1983. Influence of microwave and broiling cooking methods on quality characteristics of pre-rigor pressurized versus conventionally processed beef. M.S., Oregon State University, Corvallis, OR.