When is a good time to store hot rice in the refrigerator?

It has always been said that food should be cooled before it can be put into the refrigerator, otherwise it will easily damage the refrigerator. However, Tadpole Jun saw an article the other day saying that it was wrong to do so for the following two reasons:

1. Bacteria in meals reproduce very fast at room temperature, and the specific speed is as follows &; Dahl;

After the food is fried, the temperature will gradually decrease from 100℃:

. When the food temperature drops to 60℃, bacteria begin to grow;

. When the temperature drops to 40 ~ 30℃, bacteria will be happy and flourish;

. When the temperature drops to 7℃, most bacteria stop growing and enter a dormant state.

Second, even hot rice, as long as it is properly sealed to reduce the overflow of water vapor, will not cause too much burden to the refrigerator.

Therefore, it is not necessary to cool the food before putting it in the refrigerator. It is best to seal it in the refrigerator while it is hot to minimize bacteria in food.

What is the truth?

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First of all, it is indisputable that the spoilage of food is caused by the reproduction of microorganisms (bacteria and fungi). These microorganisms may be carried by the food itself or may come from external pollution. The reproduction of microorganisms is influenced by their surroundings.

Specific to meals, full heating can kill most microorganisms. Therefore, the corruption of overnight meals is mainly due to foreign bacteria entering the meals and reproducing under suitable conditions.

So, what are the appropriate conditions?

Ideally, bacteria can divide once every 20 minutes; If a bacterium is deliberately cultured for 10 hour, 10 billion bacteria can be obtained. The problem is that many times, the situation is not so ideal.

The growth and reproduction of bacteria are mainly affected by five factors: temperature, gas, osmotic pressure, nutrients and hydrogen ion concentration. [1] Destroying any one of these conditions can effectively stop the growth of bacteria.

For example, refrigerators rely on low temperature, high osmotic pressure for preserves and salting, and rice drying, wheat drying, and grape processing into raisins. , extend the shelf life by reducing moisture.

In addition to the above five factors, the most important thing is to avoid the entry of external bacteria and solve the problem from the source. If you accidentally cook too much, you can fill it in advance and seal it with plastic wrap or box to isolate bacteria.

As long as the external environment is isolated from food, even if it is cooled at room temperature, it is nothing. This is actually a repetition of Pasteur's gooseneck experiment.

▲? The cooked broth is still in the goose neck bottle and won't rot for a long time, because bacteria can hardly get in.

If it is leftover food, in fact, the time of a meal has cooled to about room temperature, so there is no need to continue to "cool down", just be careful not to pollute other foods in the refrigerator twice.

▲? Such a refrigerator is clean and hygienic.

Secondly, if you put hot food in the refrigerator, will it affect the refrigerator?

Yes! However, the focus of our discussion is not the refrigerator load, but the refrigerator environment.

As we said before, there are five factors that affect bacterial reproduction. Bacteria can be divided into many types according to different growth-dependent conditions. One of the bacteria that can survive in extremely cold conditions is called psychrophilic bacteria.

Psychrophilic bacteria are one of the most common and dangerous pollution sources in modern household refrigerators. Such as Listeria monocytogenes (hereinafter referred to as Lm).

▲? Listeria

On the one hand, surveys at home and abroad show that Lm is widely used in household refrigerators. [2] On the other hand, the optimum growth temperature is 2℃ to 8℃, while the refrigeration temperature of domestic refrigerator is generally 4℃.

This temperature itself is not enough to inhibit the growth of Lm. If hot food is put into the refrigerator, the overall temperature of the cold room will rise, which may give it the opportunity to breed and pollute the food, and then cause gastroenteritis, meningitis, septicemia, febrile gastroenteritis and other malignant diseases.

In addition to psychrophilic bacteria, ordinary bacteria and molds in the refrigerator may also benefit from the increase in temperature. Therefore, it is not necessarily a good plan to put hot rice in the refrigerator.

Refrigeration is a big question. Different foods should adopt different methods. For example, meat itself contains a large number of bacteria, not only to prevent bacteria from further reproduction, but also to prevent it from polluting other foods; The taste of fruit is closely related to ethanol, and the ethanol content is determined by the oxygen content in the environment. Delicious or durable? [3]

For food, you need to pay attention to the two aspects mentioned above:

First, try to reduce the bacterial content of food itself. It is best to clean the food before putting it in the refrigerator. When cooking, food must be fully heated.

The second is to do a good job in sterilization of refrigerators. Don't pile up too much food in the refrigerator, and don't store food for a long time. It is a good plan to use sterilization agent regularly or buy a refrigerator with sterilization function directly.

truth

The bacterial reproduction of leftovers is influenced by many factors and can be controlled by other means than temperature, so it is not necessary to put hot dishes in the refrigerator. Doing so may lead to the proliferation of psychrophilic bacteria in the refrigerator, which is not worth the candle.

?

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refer to

Fan Li, Liu Jingxing, Xu Zhikai, et al. Medical Microbiology [J]. Beijing: People's Medical Publishing House, 2008,67.

2 Zhu Meijuan, Shao, Mars, et al. Detection and analysis of psychrophilic bacteria in household refrigerators in Shunyi District of Beijing [J]. Practical Preventive Medicine, 2016,23 (2):173 & ndash; 174.

Li Jiazheng and Bi Dapeng. Effects of different plastic wrap packaging on the cold storage effect and shelf quality of honey pomelo [J]. Journal of Agricultural Engineering, 20 10/0,26 (1): 315&; ndash3 15.

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Author: Zhao Yanchang