The Principles of Microwave Cooking

Microwaving is not an exact science. The quality, thickness, size and shape of the foods – and of the container they are in – all make a difference to how long they require to cook. In this book I give approximate cooking times but in general it is always wisest to undercook rather than overcook. You can always test and cook for a little longer if necessary. As you become more experienced, you will learn to tell quickly how long foods will take and how to cook them to perfection. Microwave cooking is no more difficult than cooking in a conventional oven, but it is different.

General principles

Unlike a conventional oven, the amount of food you put in a microwave will affect the cooking time. So the more items you put into your microwave to be cooked, the more the cooking time must be increased. This is because the number of microwaves is always the same, so if they have to be distributed through more food there will be less energy per item. So, where one jacket potato will take about 4 minutes, two will take 7-8 minutes, depending on the output of your cooker.
Dense foods take longer to cook. For instance, a jacket potato will take around 4 minutes, but a baked apple will take less than half that time. Also a prepared dish that cannot be stirred will take longer than one which can be rearranged during cooking, as the heat cannot be redistributed during the cooking process.
Thicker parts of foods should be placed towards the outside of the dish. For example, arrange chicken drumsticks with the bony ends pointing towards the centre of the dish. When cooking vegetables such as broccoli, the florets should be arranged with the stalks outwards.
Foods at room temperature will cook more quickly than those straight from the fridge or freezer.
Foods with a high fat or sugar content will get very hot quickly. They can burn, so cook carefully and do not use plastic containers as they may melt. Always handle with oven gloves or you could burn your hands.
It is not usually necessary to grease dishes when cooking in the microwave unless you are using a browning dish. If greasing is recommended, as in the case of some puddings, brush very sparingly with oil or melted butter or margarine. Too much fat will impair the finished dish.
Most foods will not crisp and brown but meat or poultry with a high fat content will colour naturally after about 10 minutes. Bacon rashers (slices) and pork crackling will crisp on standing.
Pastry (paste) will burn if overcooked and so will foods with a high sugar content, like chocolate. Bread, on the other hand, goes wonderfully soft when reheated but will become rubbery or completely hard if overheated. Seconds can be crucial.

Stirring and turning

Many microwaves have a built-in turntable to turn the food while cooking to help distribute the microwaves more evenly. Alternatively, your oven may have paddles or stirrers concealed in either the base or the top of the oven to do a similar job.

It is important to stir and turn food during cooking too. If you don’t, you will have hot or cold spots in your food where the microwaves have been concentrated or have not reached. It is vital that food is piping hot and cooked thoroughly before it is served. All recipes tell you when to do this. Also, remember always to stir reheated drinks before sipping. The surface of the liquid will be scalding, even if it is cooler underneath. Once stirred, your drink will be evenly hot.

Timing

Timing is all-important when cooking with a microwave. As I have said, the length of time a food takes to cook depends on its size, shape and density, the amount of fat and sugar it contains and even the size and shape of the dish it is cooked in.

Cooking times also vary from one microwave to another, depending on the output of the oven. In this book, the times are given as a guide to the range of outputs from the lowest (600 watt) to the highest (900-1000 watt). When microwave ovens were first introduced, they were often as low as 500 watt. These are not common now, however, so I have not included them. If you do have a low-output cooker such as this, add on an extra 20 seconds per minute to the longest cooking times given in this book.

As a general guide, the higher the power output, the more quickly it will cook. I have categorised ovens as 600-650 watt, 700-750 watt, 800-850 watt and 900-1000 watt. Even within these categories there may be some variation, but don’t worry. The times in this book are minimum times, and you can always add on a little extra if necessary.

Always cook for the shortest time given, check and cook a little longer if necessary. The more you use your microwave, the more you will get used to how long particular tasks take in your model and can then cook more confidently for specific times. Do note that the recipes in some microwave cookery books may have been tested using only one level of output – older books may use 600 watts, and newer ones 750 or 850 watts. The very latest may use 900-1000 watts.

The high wattage cookers (800-1000 watts) are so fast that the cooking times differ by literally only a few seconds per minute, but those few seconds are vital. So if you have one of these, cook for the shorter time, check and add on a few seconds if necessary.

If your oven has a different wattage to those used in a microwave recipe book, you can alter the cooking times as follows:

If the recipe is written for 700 watts and your oven is 600 watts -increase cooking time by up to 20 seconds per minute.

If the recipe is written for 700 watts and your oven is 800 watts -decrease cooking time by up to 20 seconds per minute.

If the recipe is for 800 watts and your oven is 1000 watts -decrease cooking time by 10 seconds per minute, ‘rounding up’ to the nearest 5 seconds. Test and add on a little, if necessary.

The cooking times when using Medium-Low or Low settings vary very little whatever the power output.

If you have a 900-1000 watt cooker, you may find you get better results for some foods by cooking on Medium-High for slightly longer than on Full Power. Trial and error is the only way.

Adjusting quantities

If you want to cook a larger or smaller quantity of food than stated in a microwave recipe, follow these general rules.

Increasing the quantities

Use a larger dish.
If you increase the quantity of food by a half, increase the cooking time by about a third. If you double the quantity, increase the cooking time by a half. For example, if the recipe is for four people and takes 12 minutes, allow 16 minutes for six people. If you are making enough to serve eight, cook for about 18 minutes.
Calculate the increased standing time in the same way.
Cook for less time than you calculated, test, then add on extra time in short bursts, testing as you go.
Remember that you should not try to cook huge amounts of food in your microwave all at once. The microwaves need to penetrate as much of the food as possible, so there must be room to stir or rearrange it. Large single items do not cook successfully. A very thick joint, for instance, is likely to overcook on the outside before the centre is cooked, even if you turn it over during cooking, as the same part of the food is being continually blasted. You can overcome this to some extent by removing the joint for standing time, halfway through cooking.
Remember, the bigger the quantity, the longer it takes. So if, for instance, you wanted to bake 12 large potatoes and a large casserole for a party, it would make more sense to cook everything altogether in your conventional cooker, than try to cook it all in the microwave!

Reducing the quantities

Use a smaller dish.
If cooking half the quantity, reduce the cooking time by about a third. If cooking a quarter of the quantity, reduce the cooking time by about two-thirds. For example, if a recipe serves four people and takes 12 minutes to cook, the quantity for two people will take about 8 minutes, and the quantity for one will take about 4 minutes.
Calculate the reduction in standing time in the same way.
As always, cook for a little less time than you calculate, test, then add on more time in short bursts, continuing to test as you go. Once you know the timings of a particular recipe, note them down for future reference.
If cooking very small amounts of food – like a small amount of chocolate or one wedge of pizza – put a cup of water in the microwave beside the food. It will absorb some of the energy, preventing the food from overheating too quickly.

Covering foods

As a guide, foods which need to be covered when cooking conventionally need to be covered when microwaving. For best results, follow these general rules.

Cover foods that may splutter with a dome of greaseproof (waxed) paper or a piece of kitchen paper (paper towel).
Clingfilm (plastic wrap) is ideal for covering dishes where you want to keep moisture in. Pierce it in several places or roll back one corner to allow steam to escape otherwise it will billow up during cooking. Also make sure it does not touch the food during cooking. A dish with a lid is a good alternative.
Note: It is not recommended that you use ordinary clingfilm in the microwave. It has been found that the diezethylhexedipate (DEHA) used in the manufacture to make it stretchy can pass into food during cooking although it is not known to what degree this may be harmful. Make sure that any clingfilm you use is suitable for use in the microwave. It will be stated clearly on the packaging. If there are no instructions for use in the microwave, do not use it.
When cooking dishes containing liquids, use a microwave cover or a casserole dish (Dutch oven) with a lid. Alternatively, a plate that fits over the container is just as good.
Microwave plates with lids and microwave domes are good for reheating plated meals. Alternatively, put the food on an ordinary microwave-safe dinner plate and invert another plate, bowl or a casserole dish lid to cover the food to prevent drying around the edges during heating.
Don’t cover cakes or breads when cooking.
Roaster bags can be used in a microwave. They are good for poultry and joints. They help to brown the food as well as preventing spluttering and they keep the food moist. Don’t use any metal ties provided with them, however. Tie with plastic ties, string or elastic bands. If you are roasting a joint and you don’t want it to ‘stew’ in the bag, place the bag containing the joint in a casserole dish and pierce the bottom of the bag so the excess juices drain into the dish. Alternatively, put the joint in the pierced bag on a microwave rack or upturned plate over a large plate to catch the juices. If there’s room, you can put both the joint and the microwave rack or upturned plate inside the bag, but don’t pierce the bottom of the bag.
Non-stick baking parchment is suitable for freezing as well as microwaving so is good for lining dishes or covering food that is to be cooked, then frozen, or vice versa.

Shielding and arcing

Generally you should not use foil for microwave cooking as it is metallic. But you can use small smooth strips to shield wing tips, bone ends or thin parts of food that would otherwise overcook or dry out. This is called shielding. If you use too much or it is too crumpled, arcing will occur, which can damage the oven. You can use foil, shiny-side in, to cover cooked food when taken out of the microwave for its standing time before serving. It is ideal, for instance, to wrap individual, cooked, jacket potatoes. They will then finish cooking and keep hot for up to an hour. It is also useful for covering partly defrosted foods, such as a joint of meat, while it finishes defrosting at room temperature (see Defrosting, below).

Recipe conversion

Most conventional recipes can be cooked in the microwave. You will need to alter them a little, however, and it will be necessary to experiment to get the best from your machine. I’ve given tips throughout the book for specific dishes. For best results, follow these general rules for conversion.

When cooking soups and casseroles, use only two-thirds the amount of liquid stated in the conventional recipe.
Cut the conventional cooking time by three-quarters if cooking on Full Power.
Cut the conventional cooking time by half if cooking on Medium.
Cut the conventional cooking time by a quarter if cooking on Medium-Low.
Cover a dish in the microwave if you would cover it in the conventional oven.
Remember that food will continue cooking during standing time, so don’t overcook.

Defrosting

Many microwaves now have automatic defrost facility. Simply follow the manufacturer’s instructions on selecting the item to be defrosted. Tap in its weight, start the oven and it will pulse energy on and off until defrosting is complete and tell you when to turn the food.

Standing time is built in. It is impossible to be absolutely precise about exact defrosting times, however, as so many factors may affect it, so it is important to check occasionally to ensure that the item does not start to cook. Some items are best only partially defrosted in the microwave and then left to complete defrosting at room temperature.

For best results, follow these general principles.

Defrosting is usually carried out at Medium-Low (30 per cent power) but if you have a 900-1000 watt oven you may find it best to use Low (10 per cent power). Unlike cooking on Full Power, the timing varies very little whatever the output of your model.
The rules for arranging foods and their size and shape apply to defrosting as well as cooking.
If defrosting meat or other foods where you don’t want to use the liquid that drips out, place on a microwave rack with a container underneath so the liquid will drip away from the food.
Defrost in short bursts only, with standing time in between. If you microwave for too long, you’ll start to cook the outside.
Check food before the end of the given defrosting time and remember it will continue to defrost during standing.
When defrosting minced (ground) meat, scrape off the meat as it defrosts and remove from the oven. Freeflow mince can be cooked from frozen.
Break up casseroles, soups or other foods frozen in a block as soon as possible and move the frozen pieces to the edge.
Ease apart pieces of food such as chops, diced meat, sliced bread and bacon rashers (slices) as they defrost to allow more even distribution of the microwaves.
If defrosting food in a bag, flex the bag occasionally to distribute the microwaves evenly.
Small items of meat and poultry, such as chops, steaks and poultry pieces, can be defrosted completely in the microwave but you should not try to defrost large joints or whole poultry completely. Start the process, then leave at room temperature, wrapped in foil, shiny side in, to finish defrosting. Salmonella, a nasty form of food poisoning, can occur if the flesh starts to cook before it is completely defrosted.
Protect bone ends and thin ends of meat, poultry or fish with small strips of smooth foil as they defrost, to protect them from beginning to cook while the rest of the food completes defrosting. Don’t use large pieces or arcing will occur.
Put cakes, bread and desserts on a piece of kitchen paper (paper towel) to absorb moisture as they defrost.
Don’t try to defrost cream desserts, such as cheesecakes, completely. Start the process in the microwave, then let them completely defrost at room temperature.
Remove any metal containers, twist ties or lids before defrosting in the microwave.
Vegetables can be cooked straight from frozen. Bags of frozen peas, for instance, can be cooked in their bag.
You will find specific times for defrosting different foods in the second half of the book.

Reheating

Many foods can be reheated successfully in the microwave and this is one of the most commonly used functions of microwave ovens. It is important to turn or stir foods as appropriate to distribute the heat and to make sure that they are piping hot before serving, never just warm or even fairly hot. See the individual entries in the main chapters for specific instructions.

Browning

Browning does not happen naturally in the microwave, but there are various ways to achieve a similar result.

Browning dishes

These provide the best and simplest way to brown foods in the microwave, although they have become less popular and are not essential. Always follow the manufacturer’s instructions. Wear oven gloves when handling a browning dish after heating and don’t place it directly on your work surface as it gets extremely hot.

Preheat the dish for 4-8 minutes, according to your microwave output. Add a knob of butter or margarine or 15 ml/1 tbsp oil and swirl round to cover the whole surface. Add the food to be cooked, pressing it down on the plate, thinnest parts towards the centre. Cook on Full Power according to the table below.

Other ways of browning foods

Browning can also be achieved by adding ingredients before, during or after cooking. These can give both colour and extra texture.

Before cooking:

Brush meat and poultry with:

Melted butter or oil and dust with paprika

Mushroom or tomato ketchup (catsup), or Worcestershire, soy, brown or barbecue sauce, mixed with an equal quantity of water

Warm honey, mixed with a good dash of soy sauce and a good squeeze of lemon juice.

Quickly sear and brown the surfaces of meat or poultry in a frying pan (skillet).
Dip chops, steaks or poultry portions in beaten egg, then dried or toasted breadcrumbs, toasted nuts or sesame seeds, crushed crisps (potato chips), corn or branflakes or stuffing mix.
Marinate meat or poultry in a marinade containing soy sauce, tomato or red wine to impart a good rich colour to the flesh.

Halfway through cooking:

Brush with a sticky glaze such as:

Redcurrant jelly (clear conserve)

Shredless marmalade

A mixture of clear honey and wholegrain or Dijon mustard.

After cooking:

Place the cooked dish under a preheated grill (broiler) for a few minutes, to brown any toppings and crisp any skin.

Browning cakes and breads

Plain cakes and breads look particularly pallid and uninteresting when cooking in the microwave, but there are several ways of brightening them up. Choose from any of the following.

While making up the mixture:

Use wholemeal flour rather than white (you may need a little extra liquid) and/or brown sugar instead of white (chocolate and coffee cakes look fine anyway).
Substitute 15 g/½ oz/2 tbsp custard powder for white flour to improve the colour.

Before cooking:

Sprinkle the surface of cakes with ground cinnamon, chopped nuts, desiccated (shredded) coconut or chopped glace (candied) fruits.
Brush breads or rolls with egg yolk and sprinkle with bulghar (cracked wheat), toasted sesame seeds or poppy seeds.
Brush scones (biscuits) with melted butter or margarine and sprinkle with toasted sesame seeds or chopped nuts or demerara sugar (for sweet ones).

Halfway through cooking:

Sprinkle cakes and sweet scones with a mixture of demerara or light or dark brown sugar and chopped, toasted nuts.

After cooking:

Dust with sifted icing (confectioners’) sugar or coat in butter cream, icing (frosting) or melted chocolate.