Microwaves selectively heat with little direct heating of most solids. Rapid, uniform heating of the inactivation temperature can control and terminate enzymatic reactions. Almost any heat transfer problem can benefit from the use of microwaves because of their ability to heat in depth without high temperature. Microwaves heat a product rapidly and uniformly to pasteurizing temperature without the overheating associated with external, high temperature heating methods. Ultra-rapid internal heating by microwaves causes puffing or foaming when the rate of heat transfer is made greater than the rate of vapor transfer out of the product interior.
Microwaves are ideal for producing puffed snack foods.
Many solvents other than water are efficiently vaporized by microwaves, permitting solvent removal at relatively lower temperatures. Because the microwaves heating effect is roughly proportional to moisture content, microwaves are ideal for equalizing the moisture in a product which leaves a process in a non-uniform condition. Controlled, rapid thawing of bulk items is possible due to the deep penetration of microwaves into frozen materials.