Don't buy things with a long shelf life because they contain a lot of preservatives? Is this true?

Rumor: "Things with a long shelf life have a lot of preservatives added to them"

The shelf life of food has always been something that people pay close attention to when considering food safety. Sometimes you will hear family members say: Don’t buy things with a long shelf life, because they contain a lot of preservatives.

Rumor analysis: Actually, this is not the case.

In fact, food preservation is not entirely achieved by preservatives. The long shelf life of food is mainly affected by many factors, such as the state of the food itself and external factors such as packaging.

The shelf life of food has always been something that people pay close attention to when considering food safety. Sometimes you will hear family members say: Don’t buy things with a long shelf life because they contain a lot of preservatives. Is this true?

In fact, food preservation is not entirely achieved by preservatives. The long shelf life of food is mainly affected by two factors: internal and external factors.

The shelf life of food is related to the state of the food itself

The first is the internal factor, that is, the state of the food itself. Generally speaking, foods with low moisture content have a longer shelf life than foods with high moisture content. For example, tomatoes with high moisture content will be covered with mold after two or three days at room temperature, while dried noodles will not change at all even if they are placed in a drawer for a year. Dried foods such as nuts and grains are not easy to breed microorganisms because of their low moisture content. As long as the environment is kept dry during storage, they can be guaranteed not to deteriorate, so preservatives are rarely added.

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This is because when the water content in food is low, microorganisms can hardly obtain the water they need to survive and reproduce, so food is less likely to spoil. Foods like tomatoes, which are full of water and contain nutrients such as sugar, can easily become a petri dish for microorganisms and will spoil quickly as long as the temperature conditions are suitable.

But food containing sugar does not necessarily spoil faster. In fact, foods with high sugar content will have a longer shelf life. This is because the high sugar content and low water content environment also inhibits the growth of microorganisms. For example, honey can be stored for a long time after being sealed.

In addition, high salt content can also inhibit the reproduction of microorganisms. For example, pickles, salted fish, and bacon all use this method to extend their shelf life. Similarly, foods such as soy sauce, vinegar, and wine are not conducive to the growth of microorganisms, so their shelf life is relatively long and there is no need to add preservatives.

Some external factors also affect the shelf life of food

In addition to the state of the food itself, proper external packaging can also extend the shelf life of food. Vacuum, sealing, filling with inert gas and other methods can effectively inhibit the growth and reproduction of microorganisms. For example, potato chips, cakes, etc., will be filled with nitrogen, carbon dioxide and other gases in the packaging bag. Some foods use special high-barrier packaging bags, which can block factors such as oxygen, water vapor, and ultraviolet rays that may affect the shelf life of food. Some packaging bags will also add small packages of deoxidizers and dehumidifiers to ensure that the external environment of the food can delay the deterioration of the food. In addition, high-temperature steaming and sterilization of food, ultraviolet sterilization and other methods can also extend the shelf life of food. For example, canned eight-treasure porridge and canned vegetables will first be canned, then steamed at high temperature, and finally sealed. This can effectively kill the microorganisms on the food, and the closed environment blocks the entry of new microorganisms, so the shelf life of the food can be extended. Most canned foods use this disinfection and sterilization method. As long as they are kept sealed and stored in a cool place, the shelf life can reach several years. High temperature sterilization is commonly used for milk. Fresh milk with a shorter shelf life is usually pasteurized at a lower temperature, so the shelf life is usually 3 to 5 days; while some milk with a longer shelf life often uses ultra-high temperature instantaneous sterilization technology, coupled with aseptic operation during the canning process and aseptic packaging, which can greatly extend the shelf life of food. The same is usually true for some fruit juices and beverages.

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Therefore, the long shelf life of food is actually affected by many factors and is not necessarily due to the addition of too many preservatives.

In short, the shelf life of food is not determined solely by the amount of preservatives, but by the combined effects of internal and external factors. When choosing food with a longer shelf life, you don't have to worry too much about the amount of preservatives added. You can look at the shelf life of food more rationally and make healthier choices by understanding the characteristics of the food, the production process, and the packaging method.

Looking in the mirror of rumors

The characteristic of such rumors is that they do not provide solid scientific evidence to support their views, but are based on a vague and general assumption that a long shelf life means more preservatives. Therefore, when facing rumors related to food safety, we should remain calm and rational, not easily believe unverified information, but seek verification and verification through multiple channels.

Author: Xinshi Science Studio

Review丨Zhang Yu, researcher at the Chinese Center for Disease Control and Prevention, national health science expert