Cookbook:Microwaving

Microwaving is cooking food in a microwave oven. It is often quicker and more convenient than equivalent methods such as boiling or baking. Many vegetables, for example, can be microwaved instead of boiled or steamed.

As with other cooking instruments some care must be taken and food should be checked regularly if it is microwaved for a long period. Aluminium foil and other metal items should never be put in a microwave. Always use a container labelled "microwave safe" to avoid toxins in foods. Similarly, metal decorations on the dishes can damage the dishes and denature the food.

Items are often extremely hot after being microwaved, so take care when removing them.

General

Microwave cooking includes a number of methods which at first sight are similar to those used in a conventional oven. The methods all make use of a microwave oven, and that might be either a simple microwave heating device, or one that includes the additional techniques of steaming, crisping, or grilling.

Although microwave cooking is in general use, it is usually acknowledged as having more limited scope than conventional ovens. That said, for those tasks for which it is particularly useful, it is both efficient in energy terms and in the time it takes to complete its tasks.

The basic microwave oven heats by the movement of water in the foods. This movement generates the heat that is used for cooking. This technique cannot in itself cause browning, so the above-mentioned combination ovens have been designed with additional heating elements (grilling). Like conventional ovens, some foods are dried out at their surface during cooking, so both the addition of water and steaming are commonly used. Additional crisping plates are used to make foods like pizza and roast potatoes crisp on their surface.

Containers for Microwaving

Metal Containers must never be used conjunction with microwaves. Microwaves are reflected by any kind of metal, and it can be quite a violent event if the power levels are high. Clearly, food in a metal container would not receive any energy and so apart from the dangers mentioned, the food would just not heat well. This comment also applies to materials that contain traces of metal, such as some glasses and porcelains, and in particular items that have an obvious metallic trim or decoration.
In general, containers made for microwave use are marked as Microwave Safe. Other items without marking can of course be used but a test is needed to check whether or not they are safe. The test is to fill a cup with water and place the container and it in the microwave to heat on high for a couple of minutes; if by the time the water is hot, the empty container remains cool, then it is probably transparent to microwaves and might well be safe to use; the other thing to consider is whether or not the container can sustain the conducted heat from hot food, and whether or not the additional grilling functions of a combi microwave will cause it damage. That said, most table plates and Pyrex, stoneware, and earthenware containers without elaborate decoration will be found suitable.
Cling Film improvised lids. Steam vents must be made in any lid or covering used in the microwave, to avoid the build up of pressure. Choose a food wrap material that is sold as being suitable for the microwave. Some materials are made only for cold wrapping, and in general these days, non-pvc materials are preferred for microwave lids. Disposable microwave cooking bags with a seal are to be had. These effectively substitute for containers and can help to keep the microwave clean.
Accessory packs for the microwave are often supplied with a new item. These are made of a microwave-safe material and commonly contain a two-part steamer and lid, a crisper plate, and a plate cover with a vent already in it.
Exceptions. Sometimes small pieces of aluminum foil can be used to protect parts of the food from overcooking.

Heat Circulation

Because microwaves cannot effectively penetrate food beyond about one or two inches, food in excess of these dimensions depends on conduction of heat from the absorption regions to cook them. For this reason microwave cooking has adopted a number of necessary conventions.

Stop and Stir often during the cooking - Stirring is essential to make sure both that relatively cool parts of the food reach the energy and that the existing heat is evenly distributed. It is usual to stir foods at least once, and preferably more, during their cooking.
Thin layers of food heat best. When there is a choice food is arranged for cooking in thin layers rather than thick ones. Additionally, since the food at the center of a plate is found to receive less heat than that at the edges, the thickest food items are best placed on the outside.
Water helps heat transit. To assist in the circulation of heat some recipes add a tablespoon or two of water, for example, in the softening of vegetables.
Thick items are cooked slowly. Thin food penetration is consistent but conduction through thick sections of food takes time, so thick sections of food and food that cannot be easily stirred tend to be given longer times at correspondingly lower power levels, where the best results are obtained when the outside of the food is prevented from drying out at the same time; for example, by enclosing in a microwave bag.

Adjusting Cooking Times for Power Level

If the microwave oven used for the recipe did not have a 750W or 350W setting, but had a 600W and a 300W setting instead, then all of the cooking times could be adjusted for the new power levels. The new cooking times would just become (750/600) times 6, and 350/300 times 10. For example:

The old cooking times were 6 minutes at 750W and 10 minutes at 350W.
The ratio is always:  "Recipe quoted power divided by machine power being used" 
These times are therefore just:  
(750/600)*6   =  7.5 minutes at 600W and
(350/300)*10   = 11.91 or about 12 minutes at 300W 
So the old cooking times are increased slightly in proportion to the change in power.

The change could be calculated for a more powerful oven too, using the same proportionate method. That is to say, power changes can always be calculated on the assumption of proportionality. In fact it is likely that cooking times will be adjusted for both changed power settings and for changed weights of ingredients. In this event the table in the next section may prove useful.

Adjusting Cooking Times for Changed Weights

If the weights of the food to be cooked much differ from those of the recipe then the cooking times will be wrong. It is possible to adjust the cooking times to take account of these changes, but the changed cooking times do not work in proportion to the change in the way of power level changes. Specifically, if you double a recipe quantity, you should not necessarily double the time; it is more likely to be closer to a multiple of 1.5 times the original recipe time; not twice.

Approximate Adjustments for Recipe Weight Changes
Recipe Weight x 0.5	Recipe Weight x 0.75	Weight as per Recipe	Recipe Weight x 1.5	Recipe Weight x 2
Decrease to 0.66 of Cooking Time	Decrease to 0.89 of Cooking Time	No Change-Weight Same	Increase To 1.33 of Cooking Time	Increase To 1.5 of Cooking Time

The figures given in the table are approximations for small changes, and should not be used beyond a single doubling or halving of the recipe time; that is, they cannot be used four times to increase by eight, since large errors will occur. Make gradual changes minute by minute when near the approximate time, and check the cooking each time to get it right.

Microwave Recipes for Basic Foods

External Links

Cooking Basmati Rice : A rice producer's internet page with fairly clear instructions on different methods for the cooking of rice, and a table of cooking times for different rice types.