Understanding Your Microwave Oven

What is microwaving?

In a conventional cooker, heat is radiated round the food, cooking it from the outside inwards. This gives it the traditional brown, cooked appearance on the surface. In a microwave cooker, the food is cooked by microwaves, which are similar to radio waves. They are converted from ordinary electricity using a magnetron, situated in the top of the microwave oven. The microwaves penetrate the food to a depth of about 5 cm/2 in and cause the water molecules in the food to vibrate. This in turn produces friction, creating heat, which cooks the food. Because there is no external heat source, the food does not brown or crisp on the surface. This can be achieved, however, by various methods that I shall suggest later.

The power output of different models of microwave varies, and this will make a considerable difference to how long foods take to cook. A low-wattage oven (600 watts) will take longer than a 700 watt oven, which, in turn, will take longer than an 800 watt oven. The ovens with an output of 900-1000 watts are, of course, faster still, but I find that for the best results it is sometimes better to cook foods on 70 per cent power (Medium-High) instead of Full Power in these very high wattage ovens. I shall explain more about this in the section on Power Output Settings.

Foods react to microwaves instantly, so they cook very quickly. They also continue to cook after you turn off the cooker, because the molecules continue to vibrate, only gradually slowing down until they stop. The vibration ‚Äì and cooking ‚Äì goes on even if you take the food out of the oven. This is why it is important to take the ‚Äòstanding time‚Äô into account as food will carry on cooking during that time. It also means that you should never completely cook food when microwaving, but remove it when it is still slightly underdone. It will be cooked to perfection after the designated standing time. If you do miscalculate and it is still slightly undercooked, you can pop it back in for a few more seconds.

Different types of microwave oven

Most of you will already have a microwave in the kitchen, but if you are buying for the first time, or replacing your old machine, there are a few things for you to consider when making your choice.

Microwaves come in several different types. There are the inexpensive, basic models that simply provide defrosting and cooking facilities; some may have variable heat settings. These are perfectly adequate if you only want to defrost and reheat ready meals and rarely want to cook items from scratch. Their main drawback is that the capacity of the oven tends to be small, which will limit the quantity you can cook.

Next are the models with variable heat settings, auto-defrost and auto-cook facilities. These tend to be larger than the basic models and are best for straightforward microwave cooking.

The third option is a microwave with auto-defrost and auto-cook settings plus a built-in grill (broiler) or browning element. These give you the added option of being able to brown your food after cooking, or to use the grill on its own for such foods as thin pieces of meat or fish, burgers, toasted sandwiches, cheese on toast, etc. The grill operates with the door shut and the turntable, if there is one, rotates to give even browning. The grill is usually preheated before use. This is my preferred type of microwave oven.

The final option is a combination cooker. These machines use a combination of hot air (to brown and crisp the surface) and microwaves, thus reducing normal cooking times by about half. Some cookers use the radiant heat of a grill element to heat the air, while others have an element that heats up behind the back wall of the cooker. The air is circulated by a fan and the results are extremely good, particularly for cakes, gratin dishes, crumbles and roasted vegetables and meats. Bread and scones (biscuits), too, rise beautifully. The only disadvantage is that you don‚Äôt get as much of the delicious smell of baking you do with a conventional cooker (this, of course, is turned into a bonus when you are cooking strong-smelling fish or veggie dishes!). These machines can replace a conventional cooker, but as the oven capacity is very limited, you have to cook one dish at a time instead of putting everything in together as you would in a conventional oven. This wipes out any fuel-saving and may prove to be more labour-intensive. But it is a good choice if you are cooking for one or two people at the most.

Power output settings

Different microwave ovens also have different power output settings. There is no standard power indicator on them, so it‚Äôs important to know the percentage output of each setting. For instance, when using 100 per cent output, some microwaves call this Full Power (as I have in this book), others call it High and others have the actual maximum wattage output (e.g. 1000 watts) on the dial or programmer. To make it even more complicated, I have recently come across one cooker that uses High for 70 per cent power and Full Power for 100 per cent! This chart shows the right settings, based on a 1000 watt cooker, but remember, it is the percentage of power used that is important.

Percentage	Description	No. on dial	Wattage
10%	Low/Warm	1	100w
30%	Medium-Low/Defrost	2	300w
50%	Medium/Simmer	3	500w
70%	Medium-High/Roast	4	700w
100%	High/Full Power	5	1000w

Using the settings

There are five different power levels on most ovens. Many foods are best when cooked on 100 per cent (which I refer to as Full Power). But if you have a high wattage oven, you may get better results cooking on 70 per cent (Medium-High) because the microwaves are so fierce. Check your manufacturer‚Äôs instructions, and try both ways to see which results are best. In all cookers, some foods benefit from more gentle cooking. The table below gives you a guide:

Labelling

* Reproduced courtesy of the Department for Environment, Food and Rural Affairs.

Most new domestic microwave ovens now display a label that ties in with the labels on food packs, referring to microwave cooking. Simply match the information on the food pack with that on the oven to give the heating time needed. The oven label, an example of which is given below, shows three important pieces of information.

The microwave symbol

The microwave symbol shows that the oven has been labelled in compliance with the new scheme.

The power output

The figure in this box shows the power output of the oven, in watts, based on an internationally agreed standard (IEC 705).

If your oven is rated 700 watt, it will heat food faster than a 600 watt oven, but not as fast as a 800/850 watt or 900/1000 watt oven.

The heating category

In this box, there will be a letter. This is the heating category based on your oven‚Äôs ability to heat small food packs.

Instructions on food packs weighing up to 500 g (18oz) are likely to be given in terms of these letters.

If your oven is category C, it will heat up small portions of food faster than category A or B but not as fast as a category D or E oven.

The food pack label

Most packaged food suitable for microwaving will be marked with the microwave symbol and appropriate instructions for heating. Below is an illustration of the type of label used.

After heating, always check food is piping hot throughout. If not, heat for a little longer.

Foodline

If you need further help to understand the instructions on food packs, a free helpline is available through the Food Safety Advisory Centre to offer practical advice. Call freephone 020 7808 7256.

Containers and equipment

It is important that you use suitable containers and equipment when cooking in the microwave, in order to ensure not only best results but also your safety and the long life of your oven. There is a huge range of containers and equipment now available for use with microwaves. Not all of it is necessary, however. In many cases, you can use your ordinary kitchenware.

You will find that you use fewer dishes when microwave cooking, because many of the dishes you would normally use just for serving food can also be used for the cooking. You must make sure that whatever dishes you use are microwave-safe, however.

You can use: Ovenproof glass dishes, glazed earthenware, dishwasher-safe porcelain, pottery and boilable plastic; also basketware and wood for very short times only, like warming bread rolls.

You can‚Äôt use: Metal bakeware, ironstone, thin plastics or any crockery with metal trim.

The dish test: To test if a container is suitable for microwave cooking, stand half a cup of water in the dish to be tested. Microwave on Full Power for 1 minute. If the dish feels cool but the water is hot, it is fine to use. If the dish feels hot and the water is cool, the dish absorbs microwaves and should not be used.

Shape and size

The size and shape of a container is very important when cooking in the microwave. Round, oval or rectangular dishes with rounded corners give the best results, because the microwaves are distributed more evenly. If the dish is too small, the food could bubble over and it will take longer to cook as it is so densely packed. If the dish is too big, the food may become dry and overcook. Shallow dishes of food will cook more quickly than deep ones. For best results, remember the following general rules.

Choose straight-sided containers and, if a lid is going to be needed, a casserole dish (Dutch oven) is ideal.
For vegetables etc., choose a dish large enough to hold them in a single layer.
For a recipe cooked in liquid, such as a casserole, make sure there is about 5 cm/2 in of space above all the ingredients to allow enough room for it to boil.
For cakes and bread, use a dish with enough height to allow for rising.

Utensils

Metal utensils, such as spoons or whisks, can be used to stir food but should never be left in the microwave during cooking. A spoon rest at the side of the cooker is a good idea to avoid mess on your worktop.

Wooden spoons can be left in foods that need repeated stirring during microwaving, but only for short periods of time. However, make sure the spoon does not touch the top or sides of the oven during microwaving.

Microwave racks

These are specially coated racks with feet. They are placed in the oven to lift foods off the floor, thus allowing air and microwaves to circulate more freely. They can also be used when you want juices or other liquids to drain away from the food being cooked.

Microwave domes or lids

These are very useful for covering plated meals or any foods that require reheating. You can, of course, use an inverted dinner plate or a cereal bowl instead, or the lid of a casserole dish (Dutch oven).

Microwave stacking rings

If you want to microwave several plated meals at one time, the easiest way is by using stacking rings. These allow you to stack up to four plates on top of each other with air circulating between them. You must rearrange the plates during heating, however, so that they all receive the same amount of energy.

Microwave meat thermometers and probes

Microwave thermometers are specially designed to be inserted in the meat or poultry and can be used while the microwave is on. (A conventional meat thermometer can only inserted once the meat is removed from the microwave.) Some microwaves have a probe, which is attached to the inside of the oven. It is inserted into the meat and the cooker will switch off automatically when the meat reaches the correct temperature. This may be lower than you expect, but remember that the temperature of the meat will continue to rise on standing as it completes cooking.

The meat should always feel tender when tested with a skewer and the juices should run clear when poultry is pierced in the thickest part of the thigh with a skewer, but the temperature is a more accurate indicator when checking the joint or bird is cooked.

Browning dishes

A browning dish is a specially designed microwave dish that absorbs microwave energy and so browns the surface of foods cooked on it. It can be used to sear and cook meat, poultry, sausages, eggs, and even pizzas and toasted sandwiches.