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What is microwave energy?
  Electrical energy is normally transmitted through wire but as electro-magnetic energy it can travel through space or along tubes. From electricity we obtain light, heat and power. From electro-magnetic energy, microwaves, we receive radio and television, long distance calls and radar. Microwaves are naturally present in the atmosphere from the sun, stars and during thunderstorms.

What is power output?
  This is the amount of microwave energy which is available to heat and cook food. It is usually described in Watts e.g. 900 Watt power output. The input is the total amount of watts used by the appliance to generate the microwave energy. The input is always more than the output.

How are microwaves generated?
  A magnetron inside the appliance converts the electricity into microwave energy. The magnetron produces high frequency electromagnetic waves (microwaves) of 2,450Mhz. The microwaves pass along a metal tube (waveguide) into the metal lined cooking cavity. In some models the food is rotated on a turntable to achieve a similar effect.

What is meant by the Dielectric Properties?
 

The make up of food or a substance determines how much microwave energy is absorbed, transmitted, reflected and concentrated by it and is called, the dielectric properties. Described as the 'loss factor'and 'dielectric constant' this can be calculated for each food substance.
A high loss substance such as water and most liquid foods, means that it is a very good absorber of microwave energy. A low loss substance such as foods containing ice and many container materials are poor absorbers of microwave energy. The biggest influence on the even heating of food in a microwave cooker is the food, container shape and material. For this reason, it is important to:

  • Use the right shaped container
  • Use the correct container material
  • Arrange the food correctly
  • Ensure the food is manipulated wherever possible

Which containers should be used?
  Containers should be of a non-porous material, must not warp or melt and allow the microwave energy to be transmitted to the food. Round or regular shaped containers are generally more suitable as food in those with acute corners tend to overheat and dry out in the corners and edges before it is evenly cooked. Coverings such as cling film are used where there is a need to retain moisture.

What happens to other materials?
  Microwave energy is reflected by metal and other metallic material and as a result it cannot pass through them. However, the energy can pass through other materials such as glass, china, paper and most plastics.

Why should food be manipulated?
 

Like conventional cooking, food should be manipulated to contribute to even cooking and heating. Depending upon the food it should be stirred, turned or re-arranged during the process. With some foods, a standing time is required to complete the cooking process by conduction.

When should foods be pricked?
 

Foods which have a skin or membrane should be pricked to allow the build up of steam to escape. If this is not done then the food could burst or 'explode' either in the appliance or when removed. Examples of such foods include egg yolks and whites, potatoes and their skins, tomatoes, apples, kidney and liver.

Is microwaved food healthier than conventionally cooked food?
 
  • It depends on the conventional method used but as little or no water or fat is used in the microwave and food cooks very quickly, microwave food is able to retain more vitamins and fat content can be reduced or eliminated.

How do microwaves heat food?
 
  • Microwave energy is absorbed by many materials. Food contains moisture and the energy causes the moisture molecules to agitate at over two thousand million times per second. This creates heat and food is cooked, thawed or reheated. The greatest penetration of microwaves into the food is the first 35 - 5Omm. This decreases through subsequent food layers.

What is the difference between a Commercial and Domestic model?
  • A commercial model is needed for fast food service, for dealing with large numbers of people and supporting commercial practices thus, it is often a higher wattage and is constructed with the appropriate components to meet these requirements. A domestic model will not withstand such repetitive and arduous use and may not provide sufficient heating performance as the components heat up. Also, if used in a commercial environment the guarantee may not be valid.

Which foods are best to cook for a first time user?
  • Always follow the cooker manufacturers instructions but you may wish to try:

    • Jacket Potatoes
      Prick well, place on a piece of paper kitchen towel (not recycled), cook for the given time, turn over half way through cooking. Remove, wrap in foil and leave to stand for three to four minutes.

    • Scrambled Eggs
      Beat together the eggs, butter, milk, salt and pepper. Cook for the given time. Every now and then remove the mixture and whisk with a fork to ensure an even scramble.

    • Frozen Vegetables
      Place in a bowl (or use in the food pack), cover and prick film if used. Cook for the given time. Season with salt after cooking. Salt can cause localised ionic heating that reduces the microwave penetration depth and this can dehydrate and toughen some foods.

Is the Microwave more energy efficient than a Conventional cooker?
  • As all the microwave energy is used for the cooking operation and is not wasted on heating up containers or oven shelves, the microwave cooker is often more energy efficient. If very large quantities of food are to be cooked or a conventional oven is filled to capacity, then this method is likely to be more energy efficient.


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