When winter comes, many people will choose to fill water or drinks with thermos flasks and have a steaming sip at any time. But do you know if the liquid in this thermos flask can keep healthy after several hours?
Every time Ms. Jing, who lives in the south of Xi'an city, takes her children out for a walk, she always brings a thermos flask. However, Ms. Jing has her own worries about the thermos flask with hot water.
Ms. Citizen Jing of Xi'an: I think the water has been put in for a long time. It smells bad in this thermos flask.
Not only Ms. Jing, but most people who use thermos flasks say that if the liquid stays in the thermos flask for a long time, they will also be worried about problems.
Ms. Ning, Xian citizen: It seems that the thermos flask will smell if it is put in for a long time, that is, it will smell if the water is put in for a long time, let alone anything else. It may be water deterioration.
Reporter: So will the liquid in the thermos flask deteriorate after a long time? In order to test the results of the experiment, today we also came to the Xi'an Nutrition Society. Today, our teacher Li will join us to complete the experiment.
In order to make the experimental results more accurate, we chose two different thermos flasks to carry out the experiment, but before the experiment, we have to do a series of preparations.
Li Qizhang, Nutritionist of Xi'an Nutrition Society: We don't know what we have in this thermos flask before. We can't be sure about the cleaning degree of each thermos flask. In this way, there will be some microorganisms in the thermos flask. The number of microorganisms is also different. In order to prevent this factor (microorganisms). Our experiment had an impact, so we had to disinfect the thermos flask before the experiment.
After disinfection, we added the same amount of juice powder and water to the two thermos flasks respectively. At the same time, the temperature of the juice in the ordinary thermos flask was 79 degrees, while the temperature of the juice in the slightly better thermos flask was 72 degrees. Subsequently, we extracted one milliliter of liquid from two thermos flasks and dripped it evenly on the E.coli/coliform test sheet. In order to ensure that the experimental process is not infected by bacteria, we use sterile water droplets on the test piece for detection.
Reporter: It's 11:10 now, so we will put the sample we just sampled into the incubator next to me for 24 hours of microbial culture.
According to our usual drinking habits, the water in the thermos flask in the morning will be finished in the afternoon. Then, according to the calculation of six hours, after six hours, what changes will the liquid temperature in the two thermos flasks of different qualities change? Is the liquid in the thermos flask safe to drink?
After six hours, we measured the temperature of liquid in two different quality thermos flasks. The results showed that the temperature of liquid in ordinary insulating cups dropped from 79 degrees to 49 degrees and 30 degrees, while the temperature of liquid in better insulating cups dropped from 72 degrees to 52 degrees and 20 degrees. In order to further confirm whether the liquid in the incubator can be drunk after 6 hours, we also extracted the liquid in two different incubators after 6 hours, dripped it evenly on the E.coli/coliform group test sheet, and put it into the sterile incubator for microbial culture.
Reporter: Now that 24 hours have passed, what about our experimental results?
Li Qizhang, Nutritionist of Xi'an Nutrition Society: Our experiment is to take a milliliter from our liquid and drop it on the E.coli/coliform group test sheet. If the liquid contains Escherichia coli or coliform bacteria, it reacts with a colourless pigment in the test piece to show a different colour. Then we judge the color of the test film to see if there are bacteria in the test film.
By observing the test film, we found that there was no color change in the blank control test film used to prove the sterile operation during the experimental operation. The original test pieces of two different quality thermos flasks and the test pieces after 6 hours of storage did not change in color.
Li Qizhang, a dietitian of Xi'an Nutrition Society: During the six-hour experiment, although the temperature of two thermos flasks was slightly different, no E. coli and coliform bacteria were found in them. That is to say, during this period, two different materials of thermos flasks, it does not have this kind of bacteria breeding.
Although the beverage in the thermos flask does not grow bacteria after 6 hours, experts also remind us that the strange smell that people say will appear in the thermos flask after a few hours is probably related to the fact that the thermos cup has not been cleaned.
Li Qizhang, Nutritionist of Xi'an Nutrition Society: If we open the thermos flask and find that there are some weird odors in it, it may be that there are a lot of bacteria in it. The drinks in the cup can't be drunk at all. We need to deal with them in time. When you put water or drinks in thermos flasks, try to drink them as soon as possible. Don't put them for too long, especially overnight. Usually when you use thermos flasks, it's better to take them out for cooking or sterilization at high temperature every other time, so as to prevent the remaining bacteria and endanger our health.