Scientific understanding of food preservatives

In the past, a bottle of soy sauce took a little longer, and a layer of white hair (white glutine)
would grow on the surface.
No way, people can only beat soy sauce every once in a while, which was a common thing in the past
.
Nowadays, even if a bottle of soy sauce is eaten for a month, there will be no white hair, and "beating soy sauce" has become a memory
of a generation.
What exactly makes a bottle of soy sauce change so much?

Some foods are inseparable from preservatives

If you want soy sauce not to grow white hair, you must find a way to protect it from the invasion of pervasive microorganisms
.
Table salt, which has strong bacteriostatic ability, was once the object
of people's hope.
But people soon found that in order to inhibit the negative effects of microorganisms in soy sauce, there must be enough salt, and with more salt, soy sauce will be particularly salty, neither tasty nor healthy
.

In this way, under the healthy diet standard of low salt, scientists have found that sodium benzoate, potassium sorbate and other substances can be used to preservative soy sauce "freezing age", and only need to add no more than 0.
5 grams per kilogram of soy sauce to achieve a good antiseptic effect, at the same time, this amount is not enough to bring harm
to human health.

Similar to sodium benzoate, potassium sorbate compounds that can effectively prevent or delay food spoilage and extend the storage period of food, are preservatives
in food additives.
Microorganisms are everywhere in daily life, and the "strength" of food preservatives is to inhibit the proliferation of microorganisms or kill microorganisms
.

Fan Zhihong, a professor at China Agricultural University, said that the food itself is rich in carbohydrates, proteins, fats and other nutrients, which provides convenient conditions
for microbial reproduction.
Especially those foods with high water content are more conducive to the growth of
microorganisms.
At the same time, industrially produced food, transportation distance and storage time are relatively long, but also provide opportunities
for microbial growth and reproduction.

Once harmful microorganisms infect food, they themselves or the "toxins" secreted in their growth and metabolism will directly endanger human health
.
Therefore, all industrially produced food products for commodity circulation are subject to preservation processing
.

It was once thought that some foods could be eaten
by removing the moldy surface.
With the increase in consumer awareness of food safety, fewer and fewer people are willing to take risks with their health
.
In fact, many foods begin the process
of spoilage before visible mold colonies grow.

The more delicious and nutritious the food itself, the higher the moisture content, the milder the storage temperature, and the more
opportunities it has to be favored by "gluttonous" microorganisms.
Therefore, these foods often need to be added with preservatives or stored refrigerated after opening
.
In addition to traditional preservative ingredients such as salt, sugar, and alcohol, measures for the rational use of food preservatives can also be
sought.

However, a very real problem is that if microorganisms are completely killed through high-intensity sterilization, it will cause the loss
of heat-sensitive nutrients such as some vitamins and some bioactive ingredients in food and food flavor.
At the same time, some foods cannot be eaten at once after opening, and need to be stored at room temperature for a period of time, such as various condiments
.
In this case, food manufacturers generally use sterilization combined with the addition of food preservatives to retain heat-sensitive nutrients and food flavor as much as possible, while extending the shelf life
.

Many people seem to have a "natural" resistance to "chemically synthesized" preservatives
.
"I will never buy something with preservatives to eat" and "food with preservatives is not good for the human body, can not eat without eating" and other statements, this is actually a doubt
about the safety of preservatives.

Fan Zhihong introduced that food preservatives recognized by China's national standards generally have the following characteristics: first, the properties are stable and effective within a certain period of time; Secondly, it is non-toxic during use or after decomposition, does not hinder the normal effect of gastrointestinal enzymes, and does not affect the activity of normal intestinal flora; Moreover, it has bacteriostatic or bactericidal effects at lower concentrations; Finally, it has no irritating taste and odor by itself, and is easy
to use.

Whether a chemical substance with the above advantages can eventually become an "imported" food preservative is subject to rigorous scientific experiments and risk assessments
.
In the process of experimentation, the consequences of long-term, large consumption of
a certain preservative have actually been considered.

According to reports, China has approved a total of 32 kinds of preservatives for different foods
.
All preservatives allowed to be used by national standards have undergone safety evaluation, as long as they are used in accordance with the normal dosage and scope of application specified in the standard, they will not cause any acute, subacute or chronic harm
to the human body.

Nitrite, a preservative commonly used in ham sausage, has the effect
of inhibiting botulinum toxin.
At the same time, because nitrite can react with the myoglobin in the meat to produce rose-colored nitrosomyoglobin, the meat treated with nitrite is often bright and attractive
.

However, nitrite reacts with proteins under the action of stomach acid to produce carcinogenic amines
.
Therefore, China's food additive use standards stipulate that the maximum residue limits of nitrite in cured bacon, smoked ham and other products are 30 mg/kg and 70 mg/kg
, respectively.
As long as it does not exceed this amount, it is safe
.
If people only worry about its safety risks and ignore the toxicity and danger of Botox, it is obviously more likely to cause problems
.

In fact, people's concerns and doubts about the safety of preservatives are often not in the preservatives themselves, but in the abuse, misuse, and excessive use of preservatives in the process of use
.
For example, some unscrupulous traders are "obsessed" with the color protection function of nitrite and over-add to cover up some quality defects of the meat product itself, which is easy to go wrong
.

The length of shelf life does not depend on the amount of preservative

Many people believe that the longer the shelf life of food, the more preservatives, the worse the safety
.
Fan Zhihong explained that in order to achieve long-term preservation of food, it is necessary to fight
against various microorganisms.
Traditional treatments such as drying, salting, sugar, and wine bubbles are all methods to
achieve long-term preservation of food.
However, in order to improve the taste and nutritional quality of food, modern people cannot make everything very dry, salty, sweet and so on, at this time the rational use of preservatives, the development of low sugar, low salt products, and softer taste products, can improve food quality while ensuring safety
.

Therefore, the length of food shelf life does not depend entirely on the type and amount of preservatives, but also on the characteristics of the food itself and storage conditions
.

Preservatives themselves also have strict limits on shelf life and prescribed dosage, and it is indeed "thinking too much"
to arbitrarily extend the shelf life of food by adding preservatives excessively.

Milk with a long shelf life is often thought to have a lot of preservatives
added.
But in fact, milk uses ultra-high temperature sterilization, pasteurization, aseptic cold filling technology, etc.
, and it has been kept sealed after leaving the factory, and there are no "spoilage" conditions and opportunities
at all.

Quick-frozen food is also suspected of "eating" a lot of preservatives
.
In fact, the biggest feature of quick-frozen food is that it can quickly reduce the food temperature to a freezing point well below water (usually below -18 °C).

Because the cooling speed is fast, the activity of food cells is basically stopped, and the activity of microorganisms in food is greatly restricted, and quick-frozen food can be stored for a long time
.

Fan Zhihong analyzed that if the processing technology or its own nature can ensure that a food will not deteriorate due to microbial reproduction during storage, then there is no need to use preservatives to help it maintain quality
.
If preservatives need to be used in the production process to inhibit or kill microorganisms to ensure safe consumption because of the needs of the production process or the characteristics of the food itself, then it is natural for preservatives to appear in the ingredient list
.

Fan Zhihong suggested that when consumers buy food, they should look at food labels rationally and identify them scientifically, neither believing in the statement that "the longer the shelf life, the more preservatives", nor should they be superstitious about the words "no preservatives" or "no preservatives" claimed on some labels
.

(Li Jian)

China Food News (2023.
01.
05.
06).

(Responsible editor: Zhu Meiqiao)