Microwave Technologies Association

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

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.

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.

• 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.

• 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.

• 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.

• 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.
    

• 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.