Thermos cup 'hot water in, poisonous water out', is not only toxic but also carcinogenic? Experimental results reveal the truth

"Why are you still using a thermos cup to make tea? Be careful of poisoning if you drink too much."

"Why is it poisoned? Is it good to drink tea in a thermos cup?"

"It has been exposed on CCTV before, saying that the vacuum flask is very poisonous! I think you should use it less. It seems that it will precipitate heavy metals and cause cancer. "

"Really? It feels so exaggerated."

“……”

I believe many people have heard of the saying that "tea cups are toxic", but in real life, thermos cups are widely used to hold all kinds of hot water or hot food. Is it really toxic? Let's take an experiment to reveal the truth.

1. "Hot water in, poisonous water out"? Experiments tell you the answer

Since CCTV has exposed the "toxic thermos cup" incident, many people are worried that the widely used thermos will be harmful to health. Will the thermos really "hot water in and poisonous water out"?

First of all, let's take a look at the thermal insulation principle of the thermos cup.

The thermos cup is developed from a thermos bottle. In order to facilitate portability, the thermos cup has a double-layer structure. The inner tank and the two layers of stainless steel on the cup body are welded and combined, and the vacuum is drawn. The vacuum does not transmit heat, which can reduce heat conduction and achieve thermal insulation. effect .

There is a saying on the Internet that "making tea in a thermos cup is easy to precipitate heavy metals, which is not only toxic but may also cause cancer". Is it true or false? Let's look at an experiment.

In order to verify whether heavy metals will precipitate out of the vacuum flask, Ms. Wang from Yiwu City found the Product (Commodity) Quality Supervision and Inspection Institute of the Market Supervision Bureau and asked professional testing personnel to conduct testing.

During the experiment, the inspectors took 9 tea cups of different materials and 3 tea filters of different materials as samples. The materials of the tea cups , of which 7 were thermos cups, filter The teaware is made of stainless steel, ceramic and silicone.

Source: China Yiwu Net

The inspectors took 3g of tea leaves into each cup and tea filter, and added the same amount of water to soak. After more than an hour, the tea was poured into a test tube, and the content of lead, arsenic, cadmium and chromium was measured with a detector.

The standard requirements for inspection results refer to GB 4806.9-2016 "National Food Safety Standard for Food Contact Metal Materials and Products". The migration indicators of stainless steel products are: chromium≤2.0mg/kg, arsenic≤0.04mg/kg, cadmium≤0.02mg/ kg, lead≤0.05mg/kg.

It was found that, except for the No. 3 cup, which has been used for a long time and has slightly higher heavy metals , the detection amount of other materials is relatively low.

In this regard, the researcher said: " Under normal circumstances, heavy metals will not be precipitated when brewing tea in a thermos cup. Even if there is precipitation, it is very small and can be eaten with confidence. "

Source: China Yiwu Net

Is it good to use a thermos to make tea?

" CCTV Life Circle " has done a tea brewing experiment in a thermos cup and found that the quality characteristics of the tea will be destroyed under the long-term high temperature and stuffy brewing, including the discoloration of the tea soup, the thickening of the fragrance, and the significant increase in the bitterness , so it is not recommended. Drink tea in a thermos cup.

In addition, these kinds of foods are not suitable for putting in thermos cups:

Milk : The acidic substances contained in dairy products will react chemically with stainless steel, which will make milk spoil and deteriorate , causing abdominal pain and diarrhea.

Acidic drinks : If the inner liner of the thermos is made of high-manganese and low-nickel steel, it is not suitable for acidic drinks. This material is prone to precipitation of heavy metals when exposed to acid . Long-term drinking may damage health.

Chinese medicine : Chinese medicine has different acidity and alkalinity, and it is also easy to corrode the stainless steel inner wall of the thermos cup , resulting in a chemical reaction.

Second, can soaking wolfberry in a thermos cup be healthy?

"Soak wolfberry in a thermos cup" is a lyric, and it has also become a way of maintaining health for some people. Let’s not talk about whether it can be healthy to soak wolfberry in a thermos, but friends who like to drink this way should pay attention, there may be hidden risks.

In 2020, there was a girl in Fuzhou who forgot to drink the red dates and wolfberry in a thermos cup. When she opened it more than ten days later, the thermos cup suddenly "exploded" and the lid of the cup popped up, causing the girl's right eyeball to rupture .

Why does the wolfberry in the vacuum flask explode? This has to do with microorganisms.

It turns out that dried fruits such as red dates and wolfberry are rich in nutrients. After soaking in hot water, the sugars are dissolved and decomposed, and they are more easily utilized by microorganisms.

When the temperature is suitable and the nutrients are sufficient, these microorganisms will ferment and produce a large amount of carbon dioxide and other gases , and the longer the time is, the more gases are produced.

In addition to wolfberry, dried longan, white fungus, milk tea and other high-sugar and high-nutrition foods , long-term thermos cups are also prone to microbial fermentation.

In addition, when drugs such as effervescent tablets come into contact with water, a large amount of carbon dioxide will be released. If such drinks are stored in thermos cups, it is easy to increase the internal pressure and cause the cup to burst.

Here, we should also remind everyone that hot water and gas are dangerous, so before opening the lid of the vacuum flask, it is best to slowly unscrew it and wait for the gas to be released slowly to avoid injury.

3. How not to "step on thunder" when buying a thermos cup?

Insulation cups are widely used in daily life, so how to correctly select a qualified thermos cup to avoid "stepping on thunder"?

1. Recognize the imprint

There are three common stainless steel materials on the market, which can be identified by the marks on the bottle mouth or liner:

• 201 stainless steel - industrial grade stainless steel, with poor corrosion resistance, it is not recommended to buy.
• 304 stainless steel - food grade stainless steel, with good processing performance and corrosion resistance.
• 316 stainless steel - medical grade stainless steel, which has better corrosion resistance than 304 stainless steel, but the price is a bit higher.

2. Look at the appearance

After purchasing, you must carefully observe whether there is any abnormality at the bottom of the cup, the lid and the mouth of the bottle, whether the switch button of the cup lid is normal, and whether the screwing performance and sealing performance are guaranteed.

3. Smell

Qualified thermos cups are made of food-grade materials, with less odor and basically no smell . If you smell a pungent smell, it means that the materials used are of inferior quality and it is best not to use them.

4. Touch performance

The thermal insulation cup can judge its thermal insulation by touching it. Tighten the lid after filling the cup with boiling water. After about 2 to 3 minutes, touch the outer surface of the cup with your hands. If you find a sense of heat, it means that the vacuum layer is ineffective and the insulation effect of the liner is not good.

Thermos cups have become the standard for Chinese people to drink water when they travel. Although it has a constant temperature function, it is not a "refrigerator" after all. Therefore, some drinks that cannot be put into thermos cups should be drunk fresh, otherwise they will deteriorate, which is not beneficial to the body, and may even cause Risk of poisoning.

References:

[1] "Dispel rumors! Will heavy metals be precipitated when making tea in a vacuum cup? Authoritative experiments give answers". Zhejiang Daily. 2018-08-23

[2] "The thermos cup became a "deadly cup" just because it was soaked... Many people have done it! ". People's Daily Online Science. 2021-11-24

[3] "[Must see] Soak these things in a thermos cup, is it not healthy but poisonous? The truth is...".cctv life circle.2020-11-20

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