"Healthy Food" series special planning | It turns out that vacuum-packed cooked food also needs to be refrigerated

In our impression, vacuum-packed food is safe and hygienic, and can effectively extend the shelf life. Therefore, some people will buy more vacuum-packed cooked food and store it at home, so that they can eat delicious food from afar at any time. But what you may not know is that even if vacuum-packed food is used, the correct storage method is still required to ensure the safety of the food.

The principle of vacuum packaging

The main function of vacuum packaging is to remove oxygen. Experiments have shown that when the oxygen concentration in the packaging bag is ≤1%, the growth and reproduction rate of microorganisms will drop sharply; when the oxygen concentration is ≤0.5%, most microorganisms will be inhibited and stop reproducing. In daily life, food mold and spoilage are mainly caused by microorganisms, and most microorganisms need oxygen to survive. Removing oxygen can make microorganisms lose their living environment, thereby maintaining the color, aroma and taste of food and extending the shelf life.

Vacuum packaging is good but has hidden dangers

When we remove all the air from the packaging bag, we can inhibit the growth and reproduction of aerobic microorganisms and slow down the mold and spoilage of food. However, at this time, anaerobic bacteria will thrive. Although they will not cause the food to spoil, they will produce toxins such as botulism.

Botulinum toxin is widely present in nature, but it is not very harmful and not very tenacious. It can usually be killed by cooking. However, the spores produced by botulinum toxin will produce botulinum toxin in a normal temperature, oxygen-free, and preservative-free environment. Botulinum toxin is one of the most toxic natural substances and one of the most toxic proteins. 1 mg of purified crystallized botulinum toxin can kill 200 million mice. If it is accidentally ingested by a person, it will cause dizziness and weakness at the least, and life-threatening at the worst!

Since vacuum-packed cooked food may produce such terrible spores, do you still dare to buy vacuum-packed food? Don't worry, changing the storage environment can solve this problem.

Vacuum-packed food, there are "tricks" to preserve it

Low temperature can inhibit the growth of anaerobic bacteria, so vacuum-packed cooked food should be refrigerated. If it is placed at room temperature or in direct sunlight, the vacuum packaging will have the opposite effect. Of course, even if it is refrigerated, it should not be kept for too long. If vacuum-packed cooked food is stored for a long time, it is inevitable that the packaging will leak. It is recommended to buy and eat it immediately.

Finally, I would like to remind everyone that the general logistics and transportation environment is just right to meet the needs of spore growth in vacuum packaging (normal temperature, no oxygen, no preservatives). When eating, it will be like "opening a blind box" and there is no way to ensure safety. Therefore, you must understand the transportation conditions before online shopping. It is best to use cold chain transportation, eat it as soon as it arrives, and avoid hoarding, so as to minimize the risk of consumption.

Author: Yang Haotian and Liu Hao from Luoyang Normal University

Review expert: Wang Yao, associate professor of the School of Food and Bioengineering, Henan University of Science and Technology