What is a Microwave Oven?
The microwave oven is a household appliance that has revolutionized modern home kitchens. It is designed to cook food quickly by using special electromagnetic radiation that heats objects from within. It is designed and primarily used to quickly heat foods, and is most convenient for otherwise time-consuming tasks such as melting butter or heating water. Unlike traditional ovens, microwaves cook food from the inside rather than from the outside. While it was originally used in commercial kitchens, it is now most popular in homes and the workplace.
How a Microwave Oven Works
A microwave works by sending electromagnetic waves at a frequency of 2.24 gigahertz and a wavelength of 12.2 centimeters through food. This in turn causes the water molecules in the food to vibrate, and the resulting friction with other water molecules causes it to heat up. This is how food cooks from the inside in a microwave. It is also why frozen food and dry food (such as rice) doesn’t cook as efficiently: frozen moisture and objects lacking in moisture do not respond quickly or uniformly to microwave radiation. To ensure that food cooks more evenly, many microwave ovens feature a rotating plate to turn the food around during cooking.
History of the Microwave Oven
The microwave oven is the result of an accidental discovery made by Dr. Percy LeBaron Spencer, a self-taught electronics engineer working for the Raytheon Corporation. In 1946, while working on magnetron vacuum tubes in pursuit of improved radar technology, he walked by a vacuum tube and discovered that his candy bar had melted in his pocket. He realized that the microwaves from the vacuum tubes could cook food, and experimented by putting popcorn kernels in the same location. This resulted in the world’s first batch of microwaved popcorn. In 1947 Raytheon produced the first Radarange microwave oven, which at over 750 pounds and 5 feet in height, cost over $2000 and was only used in commercial kitchens. Raytheon authorized the Tappan Stove Company to use microwave oven technology in 1952, but the first consumer-grade Tappan oven, released in 1955, cost over $1000, which priced it out of the market. Raytheon then bought Amana Corporation in 1965, who then released a counter-top Radarange microwave oven in 1967 for $600, which still made it quite expensive for households. Initially, microwave ovens were more popular in Japan than America, but by 1975 Americans had become comfortable with microwave ovens to the point that they were outselling gas ranges. By 1976 microwave ovens, which were present in 52 million American households, were more popular than dish washing machines.
Microwave Parts and Accessories
All microwave ovens are built using several basic parts. These include a fuse which is connected to the power cord; this can shut the microwave down in case of overheating or a short-circuit. Then there is a high-voltage transformer which passes electricity to the next device, which is a magnetron; these two parts serve to regulate the microwave radiation levels that are needed to cook the food. The microwave radiation created in the magnetron moves through a wave guide device which is located above the oven's cavity where the food is placed. The microwave radiation then passes through a revolving stirrer blade and bathes the food, causing it to heat up. The walls of the oven cavity are made of metal to reflect the radiation inward toward the food. A safety switch exists in all modern microwave ovens; this shuts off all microwave energy whenever the oven door is opened. Microwaves have timers which automatically stop microwaving after a defined period of time. Most modern ovens have clocks, digital timers and rotating turntable plates to turn food while it's cooking; modern ovens can be programmed by keypads. Microwaves can also have removable racks and sensors that are designed to prevent over-cooking.
Different Types of Microwave Ovens
The counter-top microwave oven was the first to reach the market. Since then, over-the-range (OTR) microwaves and cabinet-mounted microwave ovens have also entered the market. Counter-top microwaves are the cheapest and most mobile; while they take up precious counter space, the advantage is that they can be taken from one house to another, if necessary. OTR and cabinet-mounted microwave ovens save counter space, but they are more costly, immobile, and may need to be installed by a professional. Convection microwave ovens have heating elements and fans which cook the food in external heat, which cooks the food from the outside as well as the inside.
Energy usage rates by microwave ovens typically range between 750 and 1100 watts. This is higher than a refrigerator, but lower than a clothes iron. The kilowatt-hour per unit usage ranks at about 200 kWh, which is more than a color TV but less than an electric oven. To bring a cup of water to a boil, a microwave oven uses 25 % more energy than an electric stove; however, this difference amounts to less than a dollar of energy usage per year. Re-heating food in the microwave, on the other hand, uses 80 % less energy than re-heating in a conventional oven. This confirms the perception that one of the microwave's primary benefits is re-heating food or cooking smaller portions.
Benefits of Using a Microwave Oven
Microwave ovens are faster than conventional ovens for cooking and re-heating. Some vitamins are retained when food is cooked in the microwave than when it is cooked in a regular oven, because longer cooking times destroy beneficial nutrients in food. Microwave ovens only use electricity, not gas, charcoal or oil, which reduces their carbon footprint and eliminates pollution beyond that which is created in the production of electricity. Microwaves do not brown foods, especially proteins. Dangerous organisms have less time to thrive on food that is cooked in the microwave because the food is brought to a high temperature quickly and can be served right away.
In accordance with US Food & Drug Administration regulations, all modern microwave ovens are designed with redundant shut-off switches that stop the microwaving process as soon as the door is opened. Some come with sensors that detect steam or temperature levels and stop cooking at a certain point to prevent food from being dried out. Microwaves are also required to meet a Federal standard which says they cannot emit more than 5 milliwatts of radiation per square centimeter beyond 2 inches from the unit; this prevents any potential damage that could be done to pacemakers.
Effects on Food and Nutrients
Microwave ovens can reduce the amount of vitamins B, B1, C and E in foods. Microwave ovens can also damage the protein and amino acid contents in meats and reduce the food’s nutritional value. However it is often better than boiling the same foods, which will remove even more of these nutrients because nutrients are lost through prolonged exposure to heat. It is recommended not to use microwave ovens to warm up bottled breast milk, because it can reduce its nutritional value; it is advised to heat up breast milk under hot water instead.
Microwaves are as well known for their hazards as they are known for their uses. The Food and Drug Administration has found that microwaving certain foods may result in the creation or accumulation of acrylamide, which is considered to be a cancer-causing chemical. In addition, other studies suggest that microwaving generates more acrylamide contamination than frying and higher-powered microwave ovens generate more than lower-powered ones. Water can be superheated in a microwave oven to the point where it will erupt violently and cause burns; this can happen when water is microwaved in a very smooth container with no cracks or scratches. Another known hazard with microwaves is the danger of metallic objects sparking inside the oven cavity, which can lead to damage to the oven. This is caused by microwave energy reflecting chaotically off of metal surfaces, particularly sharp ones like forks and uneven surfaces like crumpled aluminum foil. Properly shaped metal objects such as browning pans that microwave pizzas come packaged in, also reflect this energy up into the food, which results in a browning effect that is not normally achieved in a microwave oven. Direct exposure to microwave radiation can cause severe burns, which is why safety mechanisms exist to stop the oven from cooking when the door is open. Certain plastic containers can melt and be ruined by microwave ovens.
However, there are also perceived hazards that either are untrue or are extremely unlikely to ever occur. For instance the threat to pacemakers has been all but eliminated due to regulations that restrict microwave radiation output, and modern pacemakers have also been designed to be shielded from such emissions. Radiation injuries are almost impossible due to the safety features of modern microwave ovens, and contrary to some rumors there is no nuclear radiation produced by these devices.
Safety Tips for Microwave Ovens