The invention of the cavity magnetron made possible the production of electromagnetic waves of a small enough wavelength (microwaves). The magnetron was originally a crucial component in the development of short wavelength radar during World War II.[6] In 1937–1940, a multi-cavity magnetron was built by the British physicist Sir John Turton Randall, FRSE, together with a team of British coworkers, for the British and American military radar installations in World War II.[7] A more high-powered microwave generator that worked at shorter wavelengths was needed, and in 1940, at the University of Birmingham in England, Randall and Harry Boot produced a working prototype.[8] They invented a valve that could produce pulses of microwave radio energy on a wavelength of 10 cm, an unprecedented discovery.[7]
Microwaves generated in microwave ovens cease to exist once the electrical power is turned off. They do not remain in the food when the power is turned off, any more than light from an electric lamp remains in the walls and furnishings of a room when the lamp is turned off. They do not make the food or the oven radioactive. Compared to conventional cooking, the nutritional content of some foods may be altered differently, but generally in a positive way by preserving more micronutrients - see above. There is no indication of detrimental health issues associated with microwaved food.[66]
Any form of cooking will destroy some nutrients in food, but the key variables are how much water is used in the cooking, how long the food is cooked, and at what temperature.[44] Nutrients are primarily lost by leaching into cooking water, which tends to make microwave cooking healthier, given the shorter cooking times it requires.[45] Like other heating methods, microwaving converts vitamin B12 from an active to inactive form; the amount of conversion depends on the temperature reached, as well as the cooking time. Boiled food reaches a maximum of 100 °C (212 °F) (the boiling point of water), whereas microwaved food can get locally hotter than this, leading to faster breakdown of vitamin B12. The higher rate of loss is partially offset by the shorter cooking times required.[46]
We looked for small microwaves around 0.5 cubic foot and midrange models between 0.9 and 1.6 cubic foot. Unless you really need a turntable big enough to spin a 13-by-9-inch casserole dish or two small plates, we found that models over 1.6 cubic foot had too big a footprint for most spaces. Most people use microwaves for reheating leftovers, so there’s no reason to have an oven cavity that’s large enough to fit a 20-pound turkey. That said, you’ll want to measure the diameter of your dinner plates before getting a microwave to be sure they’ll fit.
The Toshiba EM925A5A-BS cooked the most evenly in our tests and was one of the few models we found with an option to mute the sound. The Toshiba has a control panel that’s very easy to use and includes express cooking options and preset cooking functions for specific tasks like making popcorn or cooking a potato. Also, the Toshiba is one of the few models we tested with a handle for opening the door (versus a push-button release), which some people may prefer.
When shopping for a new countertop microwave, make sure to look for a microwave with adjustable heat settings: while most microwave tasks are performed on “high,” lower power levels are usually built-in to defrost frozen foods or tackle delicate tasks like softening butter or melting chocolate (one of our favorite uses: it’s quicker and less likely to scorch if you look away for a second).
Another misconception is that microwave ovens cook food "from the inside out", meaning from the center of the entire mass of food outwards. This idea arises from heating behavior seen if an absorbent layer of water lies beneath a less absorbent drier layer at the surface of a food; in this case, the deposition of heat energy inside a food can exceed that on its surface. This can also occur if the inner layer has a lower heat capacity than the outer layer causing it to reach a higher temperature, or even if the inner layer is more thermally conductive than the outer layer making it feel hotter despite having a lower temperature. In most cases, however, with uniformly structured or reasonably homogenous food item, microwaves are absorbed in the outer layers of the item at a similar level to that of the inner layers. Depending on water content, the depth of initial heat deposition may be several centimetres or more with microwave ovens, in contrast to broiling/grilling (infrared) or convection heating—methods which deposit heat thinly at the food surface. Penetration depth of microwaves is dependent on food composition and the frequency, with lower microwave frequencies (longer wavelengths) penetrating further.[citation needed]
The plasticizers which received the most attention are bisphenol A (BPA) and phthalates,[69] although it is unclear whether other plastic components present a toxicity risk. Other issues include melting and flammability. An alleged issue of release of dioxins into food has been dismissed[69] as an intentional red herring distraction from actual safety issues.
The Panasonic NN-T945SF offers 2.2 cubic feet of interior space and 1,250 watts of power to heat food in less time than much of the competition. “It offers power levels from 1-10 with 10 being the highest,” explained one of our testers, “and I found that even using level 5, the microwave is able to heat the food very quickly and evenly.” Other pluses include the sleek stainless steel appearance and 14 auto cook options. If you frequently use your microwave to cook, steam, or defrost, you’ll appreciate the built-in inverter, which delivers consistent heating power that won’t leave food rubbery or unevenly heated. People find the display and controls to be easy enough to use, but a few online reviewers said they experienced button failure for the door after several years. The microwave is also quite large, so it's not a good choice for small homes.
If you’re worried about standing too close to your microwave and absorbing radiation, don’t be. The level of radiation in microwave ovens is very low, and must comply with strict regulations put in place by the FDA. You can read a detailed explanation in this article from The New York Times (parent company of Wirecutter). And no, for the most part, the radiation in microwaves won’t destroy the nutrients in your food.
Microwave ovens are frequently used for reheating leftover food, and bacterial contamination may not be repressed if the safe temperature is not reached, resulting in foodborne illness, as with all inadequate reheating methods. While microwaves can destroy bacteria as well as conventional ovens, they do not cook as evenly, leading to an increased risk that parts of the food will not reach recommended temperatures.[72]
If your primary concern is cooking speed, you need a microwave with higher wattage. The unit has to be large enough for your family's needs but not too large to fit in your kitchen. It is desirable to have quick keys, multi-stage cooking, and true variable power. Easy cleaning is a must because, at some point, you will need to wipe up after a cooking job.
Though some reviewers found the dial control on this Panasonic microwave “odd” at first, many others think it’s more convenient and easier to use than a keypad. “If you haven’t used a microwave with a simple dial to control the time, try one, you’ll never go back,” raves one reviewer. “The controls are super simple (because of the dial!).” And dozens of reviewers agree that this microwave does its job exceptionally. “This is the best microwave I have owned,” a satisfied customer says. “It feels like this microwave is more responsive to my food and not just zapping it. The lighting on the inside makes it a little harder to see the contents inside, but really, except to assure that something is spilling over the side of the container, it isn’t necessary to see through the door. It has many, many presets for both frozen, reheat, milk, coffee, almost everything that put into a microwave.”
Though some reviewers found the dial control on this Panasonic microwave “odd” at first, many others think it’s more convenient and easier to use than a keypad. “If you haven’t used a microwave with a simple dial to control the time, try one, you’ll never go back,” raves one reviewer. “The controls are super simple (because of the dial!).” And dozens of reviewers agree that this microwave does its job exceptionally. “This is the best microwave I have owned,” a satisfied customer says. “It feels like this microwave is more responsive to my food and not just zapping it. The lighting on the inside makes it a little harder to see the contents inside, but really, except to assure that something is spilling over the side of the container, it isn’t necessary to see through the door. It has many, many presets for both frozen, reheat, milk, coffee, almost everything that put into a microwave.”
This 0.7-cubic-foot Hamilton Beach model performs well enough to earn plenty of rave reviews, despite its budget-friendly price. Reviewers love how well it works and the full set of features it offers, in addition to its small footprint. The microwave features six preset settings to quickly cook popcorn, pizza, frozen veggies, and more. Its 700 watts of power is enough to cook frozen dinners and heat beverages but can take longer compared to more robust microwaves. The microwave can fit a 10.5-inch dinner plate, but some customers felt that the small interior was limiting. A few also complained that the light in the microwave stopped working after a few months.
Volume control is one of the best extra features a microwave can have, but it’s pretty rare. Some models allow you to mute the beeping, but few microwaves let you adjust the actual volume. We also prefer models that stop beeping when the oven door is opened. It’s a small perk but one that many of our testers appreciated, particularly those who find the beeping annoying.
If you’re worried about standing too close to your microwave and absorbing radiation, don’t be. The level of radiation in microwave ovens is very low, and must comply with strict regulations put in place by the FDA. You can read a detailed explanation in this article from The New York Times (parent company of Wirecutter). And no, for the most part, the radiation in microwaves won’t destroy the nutrients in your food.
In 1947, Raytheon built the "Radarange", the first commercially available microwave oven.[13] It was almost 1.8 metres (5 ft 11 in) tall, weighed 340 kilograms (750 lb) and cost about US$5,000 ($56,000 in 2018 dollars) each. It consumed 3 kilowatts, about three times as much as today's microwave ovens, and was water-cooled. The name was the winning entry in an employee contest.[14] An early Radarange was installed (and remains) in the galley of the nuclear-powered passenger/cargo ship NS Savannah. An early commercial model introduced in 1954 consumed 1.6 kilowatts and sold for US$2,000 to US$3,000 ($19,000 to $28,000 in 2018 dollars). Raytheon licensed its technology to the Tappan Stove company of Mansfield, Ohio in 1952.[15] They tried to market a large 220 volt wall unit as a home microwave oven in 1955 for a price of US$1,295 ($12,000 in 2018 dollars), but it did not sell well.
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