Domestic microwave ovens have been widely used in thousands of households. Because of its fast, simple, clean and energy-saving, it is favored by users, especially the elderly and families with two employees. Nowadays, microwave ovens can be used not only for simple heating, but also for cooking many delicious dishes. But will the microwave leakage of the microwave oven affect the health of users, especially the elderly? Is the microwave food cooked in the microwave oven safe? How to operate microwave cooking reasonably? What kind of food container should be used for microwave ovens? These problems have always been confused and concerned by the majority of users. Let's talk about these problems from the perspective of health and safety.

Is there a microwave leak outside the home microwave oven? Is it harmful to human body?

Generally speaking, there will be different degrees of microwave leakage outside the microwave oven, but most qualified microwave ovens in the domestic and foreign markets are controlled within the allowable range. However, from the point of view of health and safety, even a completely "qualified" microwave oven should be operated at a certain distance from the oven door during heating to ensure safety, which is particularly important for susceptible people such as the elderly, children and pregnant women.

About the harm of microwave radiation to human body, after decades of research by scientists all over the world, it is generally believed that there are two kinds of harm: one is thermal effect and the other is non-thermal effect. The so-called thermogenic effect is that microwave energy heats local tissues of human body and causes damage. The human eye and male testis are the two organs most susceptible to the thermal effect of microwave. The so-called non-thermal effect refers to some clinical symptoms, such as neurasthenia, endocrine disorders, changes in blood indicators and so on. This is caused by the non-thermal effect of microwave radiation. However, in recent years, a large number of cases or symptoms have been reported at home and abroad, indicating that this influence does exist. As for how much microwave radiation is harmless to people, the values set by countries around the world vary greatly. For example, Russia, Poland and other countries have considered the above two influences and formulated stricter standards; Some western countries, such as the United States, mainly consider the problem from the thermal effect, and the standards formulated are very loose. China adopts a compromise and relatively safe standard, which is recognized by most domestic experts. It should be pointed out that although some western countries have looser standards than China, they are very strict and serious in management and law enforcement; We often don't obey the law or enforce it lax. In addition, their people have a strong sense of self-protection. These are very worthy of our reference.

However, it should be pointed out that the standards set by these countries for microwave leakage of microwave ovens are mandatory. In other words, products must be inspected and qualified before they are allowed to enter the market. However, the standards set by our country are not mandatory; The national quality inspection department has not released the detection results of microwave leakage of microwave ovens in China market. Only since 1997, some domestic scholars have published personal test results. Judging from these data, most brand-name new microwave ovens at home and abroad can still meet the national standard requirements. But these tests are not authoritative after all. Doing this test requires special instruments, which are difficult for ordinary families and individuals to do. Therefore, considering the safety of users, we should learn from foreign practices.

According to the current national standards, microwave radiation energy is inversely proportional to the square of the distance, so it is safe to use microwave ovens in home cooking that meet the national standards. Avoid staying near the working microwave oven for a long time, and avoid staring at the glass oven door with your eyes for a long time, because the human eye is one of the most vulnerable organs to microwave radiation. As for microwave ovens with loose, leaking and damaged doors, they should be repaired or abandoned in time.

Is the microwave food cooked in the microwave oven safe?

At the beginning of 2004, some media reported that a paper published abroad said: "Regular consumption of microwave food is more likely to cause gastrointestinal cancer, and long-term consumption of microwave food will lead to permanent brain damage ...". The reason is that harmful substances may be produced during heating. Some domestic scholars have refuted this, and some scholars believe that it should be analyzed in detail. From the perspective of microwave technology, although microwave heating and conventional cooking heating are based on thermal effect, they both use dielectric loss caused by microwave radiation to cause heating and temperature rise. Therefore, different from conventional cooking, microwave heating has two outstanding characteristics: one is heating selectivity, and substances with large microwave dielectric loss (such as water, oil, salt, acid, alkali and containers containing metal impurities) consume a lot of heat and heat up quickly; However, materials with low microwave dielectric loss (such as plastics, ceramics, dry ice, insulators, etc. ) Low heat consumption and slow temperature rise. Second, due to the penetration of microwave, food is heated both inside and outside, which leads to rapid heat dissipation outside and slow heat dissipation inside, and sometimes uneven heating such as internal heating and external cooling is easy to occur. From the above characteristics, improper control of microwave food heating operation does not rule out local overheating or even harmful substances. However, conventional cooking methods (such as frying, frying and roasting) can also produce carcinogens. Therefore, when microwave heating food, pay attention to control the time and temperature to avoid local overheating, and microwave food is still safe.

In addition, the microwave oven is also an effective disinfection heat source, especially for killing fungi, molds, intestinal bacteria and fungi that do not form spores. Because microwave can penetrate the cell membrane, heat its interior, dehydrate and desalt bacteria and die, it can play a sterilization role at a much lower temperature (below 100℃) than conventional heating and disinfection, so it can retain nutrients better than conventional cooking and heating.

From the perspective of safety, master reasonable microwave cooking methods.

Because microwave heating has the characteristic of "selective heating". Users are likely to encounter two opposite phenomena when cooking in domestic microwave ovens: First, external heat is internal cooling, such as thawing in microwave ovens. If heating is too fast (using high fire), external heat will quickly melt water, even if the exterior is cooked, but the interior is still ice, so microwave oven manufacturers suggest users to use "low fire" intermittent heating for thawed food; Second, it is hot inside and cold outside. For example, heating a cold steamed bread in a microwave oven is just hot outside and hard inside, so it can't be chewed. Especially if you heat a stuffed food, such as steamed stuffed bun, its skin is dry and difficult to absorb heat, but its stuffing is rich in water, oil and salt, so it is likely that the stuffing is overheated or even smoked, and the skin is not too hot. It should be emphasized here that special vigilance is needed in the case of burning oily food. Nutrition experts and doctors advise not to eat or eat less fried and grilled foods, because cooking oil and carbohydrates are prone to produce carcinogens such as acrylamide and benzopyrene at high temperatures. Foods such as meat buns, if heated in a microwave oven, will burn locally, which will also produce the above disadvantages. Therefore, there is an article that does not advocate cooking fatty starch foods in microwave ovens. In my opinion, at least it should be carefully cooked and closely monitored. If it burns out, at least throw it away.

There are many books on the market, such as Microwave Cooking Book, which introduce how to cook delicious dishes in the microwave oven, which is very attractive. However, I often hear housewives complain that they are prone to local burns if they are not careful. Therefore, it is very necessary for consumers to know some basic knowledge of microwave heating and master cooking methods reasonably. Generally speaking, microwave heating is not suitable for continuous use of high fire for a long time, and intermittent heating can be used to make food evenly dissipate. In addition, food can be stirred (or flipped) once or twice during heating. Of course, the most important thing is not to burn greasy starchy food.

Reasonable selection of microwave food containers from the perspective of safety.

At present, there are two kinds of food containers widely used for microwave heating: ceramics and plastics. Almost all the containers sold in the domestic market are marked with the words "Suitable for microwave oven use". In fact, the microwave performance and quality of these products are quite different. Taking ceramics as an example, the requirements of ceramic food containers for microwave heating should be higher than the national standards. Because the main raw material of ceramics is clay (kaolin), its chemical composition is aluminosilicate. High-quality kaolin is an ideal container for microwave ovens because of its stable performance, non-toxicity and low microwave dielectric loss after high temperature sintering. The inferior kaolin is mixed with various metal impurities. In order to reduce costs and facilitate processing, some enterprises ignore national laws and regulations and add compounds such as iron, lead and cadmium, which increase the microwave loss of containers and make them prone to heat. When heated in a microwave oven, a small amount of these metals will precipitate, which will endanger health or cause chronic poisoning. The colored glaze on porcelain contains oxides such as lead, mercury, cadmium and tin, and inferior colored glaze is a health killer. Choose microwave food containers carefully, try to buy regular brand-name products from large enterprises, and refuse road ceramics; Try to use a white porcelain bowl without colored glaze (at least the inside); When you must choose colored glazed ceramics, you should also choose "underglaze color" to avoid contact between colored glaze and acids and avoid high temperature; If it is found that the colored glaze is slightly sticky at high temperature, it should be scrapped.

For plastic containers, containers made of polyethylene (PE) thermoplastic have stable chemical properties in the range of -20 ℃~ 120℃, low microwave loss and no toxicity, so they are the ideal first choice for microwave containers. The microwave loss of containers (including films) made of polypropylene (PP) is slightly larger than that of polyethylene, and it is also a better container for microwave ovens. As for inferior containers made of PVC, polyester and polycarbonate, foam plastic boxes, inferior plastic wrap, disposable lunch boxes, all kinds of recycled plastics and even waste materials, they should be resolutely put an end to being used in microwave ovens. This paper recommends a simple method to check the microwave quality of food containers (whether porcelain or plastic) introduced in foreign literature: put 300 ml of water in an ordinary glass, put it in a microwave oven with the container to be tested, and heat it for one minute. If the water is hot but the container is not hot, the container is safe; Otherwise, there will be a problem.

Finally, it should be emphasized that people's understanding of the harm of microwave radiation and the harm of improperly cooked food to human health is far from over, and their harm to human health is often a gradual process, which makes the research work very difficult. Therefore, as mentioned above, it is natural that scholars from all over the world have no consensus on some issues, so the wisest thing to do is to learn to handle it carefully and protect yourself.