We are regularly asked about the use of foil containers in the microwave. Many shops supply frozen or chilled prepacked meals that can be reheated or cooked either in a conventional oven or in a microwave oven.
They can, but with great caution unless familiar.
Aluminium is a metal so cannot be penetrated by microwave energy. This means that any microwaves are only absorbed through the top (open) part of the container to a depth of only about 3 cms. The aluminium effectively shields the sides and base of the of the food from overheating. This can be very useful when making delicate sauces.
Because aluminium is an excellent conductor of heat ( that’s why a lot of conventional cookware is made of aluminium) any heat in potential hot spots will be transferred around the container so more even heating can be achieved.
By far the greater benefits are:
That food can be cooked in the container rather than it needing to be transferred to a non metallic container.
Food toppings can be finished under the grill or browned as part of a combination oven cooking cycle.
In order to achieve best results and at the same time avoid damaging the microwave, these simple guidelines should be followed carefully.
Use only shallow foil containers, no deeper than 3 cms.
Use singly in the centre of the microwave glass tray to avoid getting too close to the oven sides.
Do not use foil or foil lined lids (if the food is completely encased in aluminium it wont heat at all.)
If there are no special instructions for cooking in foil trays increase cook time by 10%.
Do not use bent or damaged foil trays. Clean and dispose (recycle) them.
Do use normal precautions and stir microwaved food and ensure that it is piping hot before serving.