In conventional tempering, cartons of frozen food in solid blocks weighing up to 100 pounds are raised in temperature to just below freezing. Most plants dunk the blocks into warm water. Others use hot air. Many use floor tempering alone, without any heat aid, which may take 48 to 72 hours. Microwave tempering is applied on a moving belt to food still in cartons, and generally takes less than five minutes.
Microwave energy is a form of electro-magnetic energy.
The electrical power is converted to heat. Since the penetration of the electrical energy is uniform, the heating is even throughout the block. Costs from 0.33 to 0.20 cents per pound, or less than blast freezing. The improved yield more than makes up for this. No drip loss.