Water is the source of life, and the healthiest is boiled water. However, recently, a network of rumors about boiled water circulating on the Internet: overnight water can not drink? Cold boiled for a long time comparable to chronic poison? Repeated boiled water can cause cancer?
Many of the arguments are not very familiar to people. Yes, go online and search. These statements are considered “old gossipsâ€. So are they really true or fake? A glass of plain water is not suitable for burning or drinking. Will it be as scary as the internet?
Although experts have different opinions on some details, there is a consensus on this Internet rumors: Rumors are too extreme and do not fly.
After boiled water, should I cook for another 3 minutes?
Expert: You can have more boiling for a while, remember to open the lid
Original: After boil water, boil it for another 3 minutes. This is the only way to remove chloride from tap water. Continue heating to allow these chlorides to float with the water vapor.
Experts answer: For the water to boil and then burn for a while, the expert's argument is very consistent, there is nothing wrong with more than burning, but the 3-minute limit lacks scientific basis.
Wu Zhigang, a professor at the School of Public Health of Tongji Medical College of Huazhong University of Science and Technology, believes that when the tap water boils, it should really continue to boil, but it doesn't need to wait for 3 minutes. "When tap water is processed, it will be sterilized by chlorination. Burning and burning it will help volatilize the residual chlorine. From a time perspective, 1 and 2 minutes are enough." Wu Zhigang specifically reminded that boiling continues after boiling. When you do, be sure to open the lid to facilitate the evaporation of residual chlorine.
From the perspective of water nutrition, Hu Wengang, a dietitian at the Xiaoshan District Health Association in Hangzhou, believes that it is not only necessary to burn more for a while, but also to put it out for a short while. “The tap water itself contains some organic substances. During the boiling process, calcium substances will form, but calcium itself will not go away with the water vapor. Instead, it will remain in the water. The longer it will be burned, the less water will evaporate, and the calcium content will increase. Increasing, that is to say, the concentration of calcium in the water will become higher. Therefore, after boiling for a while, it is beneficial to the precipitation of calcium in the water."
According to Hu Wengang, in doing so, the taste of water will be better, so why not try it now?
Thousands of boiling water, repeated burning will cause cancer?
Experts: It's not easy to thrive through thousands of water
The original network: Thousands of boiling water is the boiling of water on the stove for a night or a long time, as well as repeated boiling of water in an electric water heater. The white-collar workers in the office usually drink most of the water from boiling water rooms or boilers. This kind of water boils repeatedly and causes the increase of nitrite and other harmful substances. Toxic nitrite also causes oxygen deficiency in the body. Unconscious and even dying.
Expert answer: The repeated boiling of water can cause cancer. The office worker who drinks the boiler water every day is not very worried. Fortunately, experts do not agree with this sensational statement.
To put it this way, the so-called poisoning is all about "nitrite", which is a generic term for inorganic compounds, mainly sodium nitrite. Sodium nitrite is slightly salty and soluble in water. Its appearance and taste are similar to that of salt. It is widely used in industry and construction industry. It is also allowed to be used as a coloring agent in meat products. Food poisoning is caused by nitrite. The probability is higher that the country has strict control over the use of nitrite.
How can this kind of material be found in tap water? The reason is that people drink water from natural surface water or groundwater. Because nitrates and nitrites are easily soluble in water, nitrates and nitrites in surface waters may slowly penetrate into groundwater. In addition, nitrates in water sources may also be contaminated by microorganisms and converted into nitrous acid. salt.
Although nitrite is carcinogenic, it is not easy to cause cancer through nitrite in water. The general human body's one-time safe intake of nitrite is 0.2 milligrams per kilogram of body weight. In the drinking water hygiene standards, it is stipulated that the nitrite content should not exceed 10 mg/l. If you drink no more than 10 liters of water at a time, then It is safe.
As for the tumultuous water, the argument that the content of “nitrite†is increasing is also just a speculation. "The rumors that thousands of boiling water are harmful to human health have no scientific basis. It is very difficult to get through thousands of bubbling water." Wu Zhigang said.
This time there is data to support the experimental conclusion from a university: With the increase in the number of boiling, the nitrite content in water does not have a clear upward trend. The nitrite content of all water samples was lower than the nitrite content limit of 10 mg/L as stipulated in the “Standard for Drinking Water Hygiene†(GB5749-2006). Specific data can see this version of the picture, the nitrite content of thousands of boiling water is even lower than the mineral water.
A cup of water lasts up to 16 hours?
Expert: It's best to drink the same day
Network original: The shelf life of a glass of water is only 16 hours. The total number of bacteria in boiled water is higher than in tap water overnight.
According to the experimental data, after boiled boiled water was left in the air for 16 hours, the total number of E. coli strains would seriously exceed the standard. Therefore, when boiled water boiled for 3 minutes after the heat was turned off, there was a 16 Hours of shelf life.
Expert answers: Hu Wengang agrees that water has a shelf life, but he feels that there is no scientific basis for "16 hours."
He said that water has a shelf life, in fact, quite understand, drinking raw water is easy to diarrhea, because there will be a variety of microorganisms, bacteria in the water, and after high temperature cooking, these microorganisms, bacteria can not survive, have been killed.
However, in the process of boiling water, the temperature is very suitable for microbes and bacteria to reproduce. The longer the time is, the more the breeding will be, like a pot of water placed outside, and it will be deteriorated after a long time.
How long will it degenerate and will not be suitable for drinking? There is actually no fixed time because it is also affected by the objective environment. For example, temperature, in summer, the temperature exceeds 30 degrees Celsius, the air humidity is relatively high, the bacteria breeds quickly, and can easily be contaminated causing diarrhea.
Therefore, it is best not to drink in the overnight water in the summer, and it is better to install the overnight water in the winter in a covered cup. The next morning, the water will be replaced with warm water.
Wu Zhigang suggested: "Cool should not be allowed to open for a long time, the boiling water that day is best to drink the same day."
Hu Wengang believes that the quality of the boiled water stored in the air is only 16 hours in the air. It is only personal opinions of netizens. There is currently no evidence of relevant experiments and data, except that boiled water should not be placed for too long, even if there is no shelf life. After several days of boiling water, it is best not to drink any more.
Finally, let's send a little knowledge about water -
The water that comes out of the house starts to be white?
The water released at home began to be white, and it became clear after a few minutes.
In fact, this is normal. This kind of phenomenon is called water vapor mixing phenomenon in the water supply common sense. When the water pump impeller is used to lift water at high speed, a part of the air is decomposed into water and then released from the tap, the pressure becomes smaller, and the dissolved air is renewed. Decomposition in the water will produce fine bubbles, then it looks like the water will appear whitish, and when this bubble disappears gradually, the water will return to a transparent color. This situation will not affect the normal water quality.
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