Microwave ovens work by passing microwaves through the food container and into the food. The microwaves get completely absorbed by the food. Heat gets generated by causing friction between the microwaves and the food molecules. This conversion of microwaves into heat energy helps cook the food. Microwave ovens are widely used everywhere because of two important benefits. The cooking time is short and the food cooked in microwave retains its nutrients. It is also very much useful in reheating foods.
The type of microwave utensils used must have two important properties – must allow microwaves to pass through, must not degrade at high temperatures.
As metals block microwaves, metal containers cannot be used to make microwave utensils. Crockery and utensils made of melamine resins should not be used as well. This is because up to a temperature of 70°C, there is no problem. But when temperature rises above 70°C, melamine starts to disintegrate especially during the contact with acid containing foods. The surface of the container slowly starts to lose its luster and the disintegration process gets aggravated on damage of the container surface. The chemicals that get released into the food during this disintegration are melamine and formaldehyde.
One can safely use glass, ceramic, chinaware, porcelain, certain thermoplastic wares and aluminium foils but without any metal paint. Plastics are many types. Some Type 1 Polyethylene terephthalate (PET) can be used for microwaving while some cannot be. Not all types of heat resistant plastic wares can be used and normally it is better to buy containers marked ‘microwave safe’. If a utensil gets heated up inside the oven (when it is put inside for no more than a minute), it should not be used for microwaving.