Can't eat overnight water, overnight tea, overnight meals, and overnight watermelon? 4 experiments reveal the truth
How can there be less watermelon in the hot summer? But Mr. Zhang from Hunan was hospitalized for a piece of watermelon that was left overnight.
After walking home, Mr. Zhang was hot and thirsty, so he took out the watermelon that had been put in the refrigerator the day before yesterday. As a result, two hours later, Mr. Zhang had a stomachache. was taken to the hospital by the family.
The doctor initially thought it was an acute intestinal obstruction after examination , but the condition did not improve after treatment . Immediately, Mr. Zhang was sent to the municipal hospital, where it was found that the 70cm small intestine had been congested, edematous and necrotic . He was diagnosed with acute hemorrhagic necrotizing enteritis . Fortunately, he was resected immediately and recovered well after the operation.
In Mr. Zhang's case, the culprit was bacterial infection . The watermelon was placed in the refrigerator without packaging, causing a large number of bacteria to grow and multiply on the watermelon, so an accident occurred.
For a long time, the health risks of overnight food have been the focus of discussion. Who can’t eat overnight water, overnight tea, overnight meals, and overnight watermelon?
1. What can you eat overnight? Which can't be eaten?
Do overnight dishes refer to dishes that have been left overnight? To be precise, overnight dishes refer to foods that have been placed for more than 5-8 hours . In addition, the conditions for becoming an overnight dish also include temperature, airtightness and storage methods. So, can the following four overnight foods be eaten?
The first: overnight water
In 2020, the food inspection staff of Weihai Market Supervision Bureau, Shandong Province, heated tap water with a stainless steel electric kettle, boiled it for 1, 5 and 10 times, poured it into the cup and cooled it naturally, and placed it for 0, 24 and 48 hours. Nitrate content .
It was found that the nitrite content in the water increased slightly with the increase of the number of tap water heating and boiling, and the nitrite content in the water also increased with the extension of the overnight time. The nitrite content increased by 2-4 times after 24h, and the nitrite content after 48h The salt content was 0.014 mg/L.
Because the reference limit of nitrite in the national standard drinking water is 1mg/L, the nitrite in the overnight water does not exceed the standard. So in theory, it can be drunk, but it is recommended that the drinking water be kept for no more than 24 hours, and the lid should be covered.
The second: overnight tea
In 2014, the CCTV Finance and Economics program "Is it true" hired a senior tea taster to verify "Is it still possible to drink overnight tea".
The experiment selected three cups of Pu'er, Longjing and chrysanthemum tea, and after placing them overnight for a period of time, it was found that: ① the overnight tea did not deteriorate and had no rancid taste; ② the nitrite in the overnight tea did not exceed the standard, which is far below the sanitary standard for drinking water.
The conclusion is that overnight tea is safe and drinkable as long as it has not gone bad. However, from a nutritional point of view, the nutrients such as polyphenols and vitamin C in the tea have decreased after overnight.
Type 3: Overnight Meals
In 2019, Ningbo Institute of Food Testing and Inspection carried out a research experiment on overnight dishes , with 30 dishes and 450 test data .
The researchers collected freshly cooked dishes, including vegetarian dishes, meat, half-meat and half-vegetarian dishes and cold dishes , and placed them in an environment of 4°C and 25°C , respectively, and finally detected the bacteria and nitrite content respectively.
The researchers made the following findings: ① Put the lunch at noon in the refrigerator and take it out at night;
②For dishes at 25℃, after 6 hours at room temperature, although the content of nitrite does not change significantly, considering the proliferation of microorganisms, the meals at noon are stored at room temperature, and it is best not to eat them at night;
③ If you want to eat meals at noon or at night, you must store them in the refrigerator.
The conclusion is that most of the overnight dishes can be eaten, but it is recommended to eat less. If there are overnight dishes, they must be stored in the refrigerator in time, and they should be thoroughly heated before eating.
The fourth: overnight watermelon
Zhejiang Ningbo Market Supervision and Administration Bureau conducted research on whether overnight watermelon can be eaten. In the experiment, the cut watermelon was placed in an environment of 4°C and 30°C, and the total number of bacteria was measured after 4, 8, 16, 24, and 28 hours , respectively .
Regardless of whether it is placed in the refrigerator and covered with plastic wrap, the total number of bacteria within 4 and 8 hours is less than 20 CFU/g. The bacteria begin to multiply from 16 hours, and the bacteria multiply after 24 hours.
The conclusion is: within 4 hours, it can be safely eaten in the refrigerator or at room temperature. After cutting, it is recommended not to eat at room temperature for more than 24 hours. If it takes more than 16 hours to eat after cutting, it is recommended to cover it with plastic wrap and store it in the refrigerator.
2. 3 kinds of vegetables, or try not to stay overnight
Cooking at home will inevitably produce leftovers, which are usually reluctant to discard. This virtue of frugality is worthy of praise, but there are three kinds of dishes, try not to stay overnight!
The first is bulk lo -mei. It is best to eat it on the same day rather than overnight. From the point of view of food safety, overnight lo-mei is unsanitary. Even putting the lo-mei in the refrigerator is not safe, and a large number of bacteria will grow in the refrigerator.
In addition, seafood , shrimp, crab and other seafood are actually difficult to completely eliminate their own bacteria with ordinary cooking methods. If seafood is left overnight, it is likely to cause bacteria to multiply, produce a large amount of bacterial toxins, and damage the liver and kidney health after eating. .
The last is white fungus mushrooms . Dried white fungus and mushrooms have low nitrite content, but if they are soaked for too long or left for too long after cooking , not only the nitrosamine content will increase, but also a large number of bacteria will grow. Improper storage at this time Flavotoxin may also be produced and cause discomfort such as abdominal pain and diarrhea.
3. How to properly treat leftovers and leftovers?
We know that not everything can be eaten overnight, the key is to store it properly.
First of all, the World Health Organization's "Maintaining a Safe Temperature of Food" recommends that cooked food should not be stored at room temperature for more than 2 hours, and should be refrigerated in time (below 5°C).
Secondly, vegetables produce more nitrite during storage than meat, so it is recommended to leave only meat and not vegetables .
Finally, in order to ensure the hygiene and safety of the leftovers, "unnecessary operations" should be reduced . It is best to " heat through " before eating, and it is not recommended to reheat them many times.
Diligence and thrift are traditional Chinese virtues. For overnight dishes, many people are caught in a dilemma: throwing it away is a waste, but if you don't throw it away, it will be unhealthy. In fact, overnight dishes are completely edible. The premise is that they must be treated scientifically and reliably. In order to avoid the production of overnight dishes, it is best to "eat as much as you eat" when cooking.
References:
[1] "What can be eaten overnight? Which can't be eaten? ". Health Times. 2021-09-04
[2] Can "overnight watermelon" be eaten? Speak with experimental data". Life Times. 2020-07-04
[3] "Over 8 hours is an overnight meal? Whether it can be eaten depends mainly on a "standard"". Life Times. 2021-11-17
[4] "These 4 kinds of overnight dishes are too dangerous, I would rather waste them than eat them! Injury to liver and kidney, damage to intestines...". Popular Science China. 2022-06-17
[5] "What? Can eating leftovers cause cancer? It's time to tell you the truth...". Popular Science China. 2021-02-18
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