Introduction to cooking with a microwave

The Knowhow

Microwaves cook food using microwave energy that is similar to naturally occurring radio waves. Normally, these waves would fade as they disappeared into the atmosphere, but in a microwave they focus on the moisture in the food which causes lots of tiny vibrations. The vibrations get so great that the moisture and the food heat up.

Tips on cooking with a microwave:

1. Always check that the plate, plastic container or bowl you are using is microwave-safe. And remember, even though these are designed for the microwave they can still get as hot as the heated food, so take care when removing it from the microwave.
2. If possible, cut your food up into smaller portions as it will cook quicker and more evenly.
3. It's always best to cook one portion of food at a time but if you are cooking a number of individual foods at the same time (such as baked potatoes), arrange them evenly so everything gets cooked properly.
4. Remove any foil or anything metallic as this can cause sparks in your microwave; strips of aluminium can be used - but with caution. For more information, read our article on using aluminium foil in your microwave.
5. Remember that some crockery has a metal trim around the edge which can cause sparks and never use any cracked, scratched or damaged glass as it can explode.
6. Most heat-resistant non-metallic utensils are safe to use in your microwave. If made of plastic or glass the utensils will be marked as "microwave safe" or similar. If there is no marking and you are unsure, do not use it in the microwave.

Food tips:

You can cook various types of food in the microwave from fresh to frozen but always take care. Fresh foods that are overcooked can lose nutrients when heated in the microwave and frozen foods need to be defrosted thoroughly by leaving them in the fridge overnight or by using the defrost setting on the microwave.

When heating food up, it's essential that the food is piping hot before serving. If you're nervous about overcooking just cook it for a shorter time and continue cooking if needed. Read the back of the packaging for timings but use your own judgement as well; microwaves can cook at different powers (usually around 700 - 950W) so timings can vary.

It's always best practice to stir your food halfway through cooking to help it cook evenly; stirring from the outside, inwards. For foods that can't be stirred (i.e. Shepherds Pie and Lasagne) remove it from the microwave and cut the middle with a knife to see if it's heated all the way through. You can also use a food/meat thermometer to check that the middle of the food has reached a high enough temperature (over 80 °C).

When preparing food for babies you must take extra care. Always test the food or liquid temperature before feeding it to your baby and when using a baby bottle ensure the lid and teat are removed before heating. The bottle must be shaken when you're warming milk.

Meat and poultry should be cooked for longer and on a lower temperature. When cooked for 15 minutes or more, it will brown lightly in its own fat, but if being cooked for a shorter time you can brush the meat or poultry with a browning sauce to give it an appetising colour. Larger portions will need to be turned during cooking so that the top and bottom cook evenly, but it's also recommended to turn meat and poultry when they have not been deboned.

When you bake or poach eggs in the microwave, the yolk can sometimes pop as steam builds up inside it. You can stop the egg from popping by piercing the yolk with a toothpick before cooking. Note: Never cook eggs that are still in their shells.

• Plastic covers and wraps are ideal for keeping moisture in foods and also prevent splattering; when using make sure you pierce the lid
• Foods with skins e.g. jacket potatoes, sausages and vegetables should be pierced with a fork before microwaving as they can burst
• Heat liquids in a container that is wider at the top than the bottom and never microwave liquids in sealed containers and always stir them before and after cooking
• Check that the food you want to heat up is suitable for the microwave. Some foods or liquids that shouldn't be heated in the microwave are; Yorkshire puddings, boiled eggs, soufflés, oil or fat for deep frying and non-microwaveable popcorn
• Take care when heating up foods with a high sugar or fat content such as Christmas pudding or fruitcake as the sugar or fat can overheat and may catch fire.
• A microwave should never be used for drying clothes
• Always use the glass turntable plate

Microwave heating categories:

The heating characteristics and output power levels of microwaves are usually calculated using a relatively large portion of food (a 1000 gram load) but many packs of pre-cooked foods are sold in smaller packs, often around 350 grams. The UK government, in partnership with food companies and microwave manufacturers have set up a system of heating categories to help you choose the reheating time of pre-cooked food. The label on your microwave (similar picture shown below) gives the heating category and output power.

The category (a letter from A to E) is designed to help you reheat small quantities of food such as ready meals. You will usually find this letter on the packaging of ready meals weighing up to 500g.

As shown in the diagrams below the higher the output power and heating category, the less heating time required:

Note: Start cooking at the lowest recommended time and add more time if necessary. The moisture content of food can vary so ensure the food is cooked thoroughly all the way to the centre before serving.