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Microwave oven is a kitchen appliance which cooks food using microwave energy. Microwave oven is quick and efficient equipment because it transfers heat energy directly to the molecules inside foods. Microwave is a form of electromagnetic radiation which is very close to radio waves and sunlight. Microwave oven has shortened the time to prepare food.
The history of microwave oven began in the era of World War II. It has experienced a lot of changes before the present model of the microwave oven is formed. Similar to other great inventions, the invention of microwave oven happened accidently. In 1945, an American electrical engineer, Dr. Percy Spencer (1894-1970), was carrying out experiment with radar equipment, which detects objects by bouncing waves and analyzing the signals it produced. For example, radio waves are used to help ships and airplanes find their way around in darkness or poor weather. Dr. Percy Spencer had a bar of chocolate in his pocket when he was conducting experiment using a special kind of vacuum tube called a magnetron. Surprisingly, the chocolate bar in his pocket had melted due to the heat of the magnetron generated. He was curious about the heat generated by the magnetron. Hence, he leaved some popcorn kernels close to magnetron tube and observed it. He watched the popcorn started to sputter, crack and pop everywhere. Next day, Dr. Percy Spencer and his partner place an egg near the magnetron tube. They observed that the egg started to shake and quake due to the high rise in temperature create high pressure in the egg. Eventually, the egg exploded and splashed the egg yolk all over his partner's face.
After conducting few experiments, Dr. Percy Spencer came out a scientific conclusion which is microwave energy can be used to heat items. In 1953, he patented his idea and the first microwave oven was launched. In order to create a high density electromagnetic field, he used a metal box which there is a supply of microwave power in it. The food was put into the metal box and then the food was heated up rapidly. The early equipment was large, inefficient and expensive. In 1967, the first household microwave oven was formed and then microwave oven is now become widely used around the world.
The Features of Microwave Oven
Some of the features of the microwave oven are shown as below:
Automatic Cooking Programmes
Cool Touch Door
Below are some of the explanations of the features which assist the microwave oven in cooking food:
Automatic Cooking Programmes
Users are allowed to enter the weight and type of food into the programmes. Then, the oven will automatically selects the temperature and cooking time. Below are some of the pre-set programmes :
Easy clock & oven programming
The time of day is displayed by the electronic clock. Besides, the electronic clock also acts as a countdown timer to show the end of the timer function. The microwave oven will do the rest after users set the end time, the duration of cooking together with the functions and temperature of cooking.
Cooking time and power levels are set by using this numeric keypad. It is more convenient to use compared to a dial.
1-minute or 30-second key
The preset cooking time is extended, maintaining any power level which was chosen. Quick adjustments are also allowed to the previous settings by pressing the specific buttons.
The power supply allows users to control the amount of energy wasted. The variable power control enables users to simmer the food at 50% power whereas defrost the food at 30% power. Thus, full power is not used for all purposes to avoid energy loss.
Cool Touch Doors
The heat can be stored in the reflective inner whereas the cool touch door is placed on the outside of microwave oven. Protective metal gauze is located at the back of the door to avoid microwaves escape to surrounding. The protective metal gauze is also designed for safety purpose.
Cool air is circulated around the oven to ensure the appliance and nearby furniture are kept cool all the time. Besides, hot air vented from the microwave oven is also cooled. This results in less steam as cooler air is vented into kitchen. It virtually eradicates grease discolouration.
The microwaves are generated by magnetron which is the heart of the microwave oven. This strong metal box prevents harmful microwaves from escaping to the surrounding.
There has a chance for burning if the door of the microwave oven, which is still running, is opened. Therefore, the microwave oven should stop immediately when the door is opened. The Interlock is designed to ovoid the running of microwave oven if the door is opened.
Equal amount of heat could not be dissipated all over the food in microwave oven resulting some part of food might receive more heat whereas some part of food receive less heat. Turntable is a revolving glass which is installed into microwave oven to ensure even cooking. The turntable rotates the food so that the food is cooked evenly. It is crucial that having a turntable inside the microwave oven to ensure even cooking. Without this feature, users have to stop the microwave oven several times and turn the food by themselves.
Child lock is the most reliable child safety feature for microwave oven. Dishes in microwave oven might be very hot. Children might be in the risk if they open the door and touch the dishes. Child lock can be controlled using the key pad on the microwave oven.
Waveguide is a hollow metal tube which transports the microwave energy into the cooking cavity. Rectangular shaped waveguides are used for vast majority of microwave oven. The microwaves energy travel by reflecting form side to side in a zigzag pattern.
The Functions of Microwave Oven
How do microwaves cook food?Simple artwork showing how a microwave oven works
There are several main parts of a microwave oven. A microwave generator, which is called a magnetron is placed inside the strong metal box. When you start to cook, the power outlet transmits the electricity to the magnetron. Then, a high-powered, 12 cm high-frequency electromagnetic wave is converted by the magnetron. After that, wave guide blasts these waves into food partition. The food is then placed on a turntable which will spin slowly to enable the food to be cooked evenly.
The microwaves do not simply rebound when microwaves reach the food. This concept is same as the radio waves which can penetrate straight through the walls of buildings. When the microwaves travel through the food, they cause the water molecules inside the food vibrate more quickly. The microwave energy which is produced by the magnetron is converted into heat energy of the water molecules. Dry food such as rice and pasta will not cook in the microwave oven without the presence of water. Hence, the heat energy causes the molecules to vibrate more quickly. Besides, the vibrating molecules contain heat too, the quicker the molecules vibrate, the hotter the food. Thus, the microwaves transfer energy onto molecules in the food and rapidly heating up.
Shortcomings of Microwave Oven
A coin has two sides and so does any device. A microwave oven too has its own strength and weakness. Like other kitchen appliance, microwaves also have some demerits. Some of the shortcomings of microwave oven are shown as below:
There are chances of the food getting over cooked or unevenly cooked. Unevenly cooked may result in the hot food being on top and uncooked food at the bottom. The surface of food which exposed to the most microwaves has a tendency to heat up faster than the insides. Normally, the microwaves have to neglect molecules on the outside in order to excite the molecules inside the food. The thicker the food, the more difficult the microwaves penetrate the food.
Specific Utensils are Required
Microwave oven need specific utensils to cook food as not all metals and alloy vessels can be used. Some of the materials, such as metal and foil, are tended to reflect microwave energy. Usage of metal utensils in microwave oven is avoided except for some recommended procedures which use metal and foil as outlined in the use and care manual. The following are the reasons why metal and foil should be avoided in microwave oven:
The efficiency of cooking is largely decreased due to the metal utensils only allow partial penetration of the food by the microwaves.
An arc between the metal utensils and the cavity interior can damage the oven if the food is too small to absorb the microwave energy.
It is dangerous to heat liquids as they can be superheated which may lead to explosions. The actual problem happened when this superheated liquid is perturbed. Superheated liquid in conjunction with the agitation are enough to prompt troubles. The superheated liquid is able to burst off with the additional force on any disturbance.
Risk of Steam Blasts
The tight covering of containers can cause a high risk of steam blasts in the microwaves. As the temperature rise up, the molecules in the container receive more kinetic energy. Thus, the molecules collide each other create higher pressure in the container than outside. When the pressure inside the container exceeds its limitation, it will produce an "explosion" within the microwave oven.
Based on the above shortcomings listed, the recommendations for above shortcomings are given as below:
Food thermometer can be used to test food in several places to make sure that the food has reached the recommended temperature in order to kill bacteria and other harmful microorganisms which could cause food borne diseases. Moreover, food is arranged evenly in a covered dish and some liquid is added to promote uniform cooking. If it is possible, large pieces of meat is deboned because bone can affect performance of meat during cooking.
Special Utensils are Required
Microwave-safe containers and vessels should be used for cooking. The cookware, which specifically manufactured for use in the microwave oven, should be selected during cooking. Utensils which are safe to use typically will be labeled for microwave oven use. Examples of the utensils which are safe to use are heatproof glass, glass-ceramic, oven cooking bags and etc.
Avoid heating liquids for more than two minutes. Liquid do not bubble as they reach the boiling point in the microwave oven. Thus, it might get superheated. The superheated liquid only will bubble when it is moved and something disturbs it. When heating liquids, it is advisable to put a wooden stick in the container in order to prevent super heating of the liquid. After heating, the liquid is placed in the microwave oven for thirty second before taking it out.
Risk of Steam Blasts
The containers of the microwave oven are never covered tightly. The heated containers should not be taken out immediately after cooking from the microwave. This can ensure that the food is cooked properly and the steam is allowed to escape.
As all of us know, microwave ovens are often be used daily in kitchens, cafeterias, restaurants, snack bars and homes. Today, it is perhaps the most successful electric appliance introduction in the 20th century.
In a world where time means money and life is on the fast lane, we do not really have time to wait around much anymore. Everyone wants things to be fast. With the existence of microwave oven, we can do quick cooking just with the press of a button. The food can be prepared from the refrigerator to the microwave oven and onto the dining table in a short time.
If compared to the gas or electric oven, we do not need to worry about the burner whether it is still being heated after the food is prepared by using microwave oven. Thus, the chance for someone to get burned can be reduced.
Microwave oven users are often concerned about the issues of potential health hazards from the exposure to microwave radiation leakage. However, with the latest technology advances in door seal design, the leakage of microwave oven has been greatly minimized. Also, as long as the microwave oven is kept clean and dry in a safe location, it should be perfectly safe to use.
We should know that successful microwave cooking depends on understanding the limitations as well as the benefits of this type of cooking. If it is used in a proper way, it can be considered that the microwave oven offers a great, convenient and safe method of food preparation without any harmful effects on consumer safety or nutrition.
In conclusion, the microwave oven has come a long way, decreased in height, weight, and price. It has made everyone life easier.