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CONTENTSIntroduction .............................................................................................................................................................................. 1How microwave ovens work .................................................................................................................................................. 1The basic structure of a microwave oven ...................................................................................................... 1The oven ............................................................................................................................................................. 6Food containers for microwave ovens ........................................................................................................... 7Cooking foods in microwave ovens ............................................................................................................... 9Comparison with conventional ovens ........................................................................................................... 11Safety and nutrition ................................................................................................................................................................ 13Microbiology ...................................................................................................................................................... 13Cacinogens and mutagens ............................................................................................................................... 14Nutrients ............................................................................................................................................................. 16Packaging migration ......................................................................................................................................... 18Conclusion ................................................................................................................................................................................ 19Glossary ................................................................................................................................................................................... 20Additional reading .................................................................................................................................................................. 21
Microwave Ovens 1INTRODUCTIONToday microwave ovens are an established feature inmillions of kitchens throughout the world. Yet thedevelopment of the microwave oven is relatively recent.During World War II the pioneers of micro w a v ecommunication systems discovered that microwaveshave many uses. Scientists at early warning stationsfound that when birds collided with radar masts theydropped to the ground, sizzling and well cooked. Fromthis emerged the idea that food could be heated bymicrowaves.The possibilities raised by this accidental discoverywere examined further and before long microwaveovens could be found in both hospital and army messkitchens. Since then, microwave ovens have becomeincreasingly sophisticated, as have the products andpackaging materials developed for microwave use.This concise monograph summarises the current statusof scientific knowledge about microwave ovens andtheir uses. The first part of this concise monographdescribes how a microwave oven works and explainshow products and packaging have developed tooptimise the benefits of this particular method ofheating foods. The second part examines safety andnutrition, the two issues which have been the focus ofthe main concerns raised about the application of thistechnology in food preparation.HOW MICROWAVE OVENSWORKThe basic structure of a microwaveovenFigure 1 illustrates a typical microwave oven. It consistsof a cavity surrounded by metal walls with a door at thefront. The microwaves, generated by a magnetron, enterthe cavity via a metallic tube called a wave guide. Thestirrer helps to distribute the microwaves while theturntable improves energy distribution in the food.The heating processMicrowaves form part of the electromagnetic spectrumas do television and radio waves, infrared radiation,ultraviolet radiation and visible light. Theseelectromagnetic waves are a means of transmittingenergy through space just as electricity is electricalenergy transmitted through a wire. Two frequencieshave been set aside for use in microwave heatingapplications. These are 915 MHz (896 MHz in the UK)and 2450 MHz. Domestic appliances operate on2450 MHz, whilst industrial applications make use ofboth frequencies (Figure 2).The magnetron in the oven converts electrical energy atlow frequencies into an electromagnetic field thatoscillates at a much higher frequency.Food is able to absorb microwave energy, later releasingthe stored energy as heat. The main mechanism ofheating occurs as a result of rotation of water moleculesbrought about by the microwaves. Water is a moleculewhich is unevenly charged along its structure, beingmore negatively charged in some parts of the molecule
Page 1 and 2: I L S I E U R O P E C O N C I S E M
Page 3 and 4: MICROWAVE OVENSText developed by Al
Page 5: FOREWORDThe use of microwave energy
Page 9 and 10: Microwave Ovens 3FIGURE 2Electromag
Page 11 and 12: Microwave Ovens 5responsible for th
Page 13 and 14: Microwave Ovens 7modes which typica
Page 15 and 16: Microwave Ovens 9BOX 1Guidelines fo
Page 17 and 18: Microwave Ovens 11piece of steak ma
Page 19 and 20: Microwave Ovens 13Flavour/textureTh
Page 21 and 22: Microwave Ovens 15BOX 2Microwaves a
Page 23 and 24: Microwave Ovens 17conclusion is tha
Page 25 and 26: Microwave Ovens 19Many other studie
Page 27 and 28: Microwave Ovens 21Standing time: Th

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