Wen/Chen Junshi, researcher of National Food Safety Risk Assessment Center, academician of Chinese Academy of Engineering.

      First round Kexin Food and Nutrition Information Exchange Center 。

        To ensure food safety is like fighting a war, we must first recognize the main enemy. If we use great experience to deal with secondary enemies, it will be bad. What is the main enemy of food safety? At present, food borne diseases are the main enemies of food safety in the world and China (according to the data provided by American scholar Snyder in 1998, biological hazards account for more than 95% of the hazards in food supply).

What is foodborne disease?

What is foodborne disease illness）？ Generally speaking, it means food poisoning, which is typical of "upset stomach". In a year, a considerable number of people sometimes have "stomach trouble". Most of them are caused by eating food contaminated by pathogenic microorganisms. The definition given by the World Health Organization is a disease caused by various pathogenic factors that enter the human body through food intake, usually with infectious or toxic properties. Everyone is at risk of foodborne diseases.

　　 How serious are foodborne diseases?

Foodborne diseases, which cover a wide range of diseases, are an increasingly serious public health problem worldwide. The ingestion of food contaminated with microorganisms or chemicals can cause this disease. From food production to consumption (from farmland to dining table), food pollution may occur at any stage, which may also be the result of environmental pollution, including water, soil or air pollution.

The most common clinical manifestation of foodborne diseases is gastrointestinal symptoms; At the same time, this disease may also have other symptoms such as neurology, gynecology and immunity. The ingestion of contaminated food may also cause multiple organ failure in the whole body, or even cancer, thus causing great disability and death.

An active surveillance of foodborne diseases in China in the first half of 2012 showed that on average, more than 200 million people suffer from foodborne diseases every year, and one of 6.5 people suffers from foodborne diseases on average. The World Health Organization released the world's first comprehensive estimation report on the burden of foodborne diseases at its headquarters in Geneva on December 3, saying that almost one in 10 people gets sick every year because of eating contaminated food, which leads to 420000 deaths; Among them, children under the age of five are at extremely high risk, and more than 120000 children die of foodborne diseases every year.

　 Foodborne diseases are the number one enemy of food safety

Maybe everyone will think that diarrhea is nothing. Take some medicine at most. In fact, compared with chemical pollution such as pesticide residues, food contamination by pathogenic microorganisms is the first problem that really affects health.

In the 1980s, there was an epidemic of hepatitis A in Shanghai due to eating raw clams (contaminated by pathogenic microorganisms - liver viruses), and 300000 people were infected. Although hepatitis A generally does not cause death, it is impossible to see a doctor or be hospitalized. So far, this is still a record in the history of foodborne diseases in the world and has not been broken. Is this not enough to show that foodborne diseases are the number one problem?

In 2011, the food contaminated by pathogenic Escherichia coli in Germany attracted worldwide attention. China has also experienced food safety incidents caused by pathogenic Escherichia coli (different from the model in Germany this time). In 2000, 20000 people were poisoned and 177 died in Jiangsu and Anhui. Is this not enough to show that foodborne diseases are our number one enemy?

It is believed that people will inevitably get sick if they eat cereals. It is not surprising that "disease comes from the mouth". Therefore, we did not pay attention to dysentery, typhoid or even cholera (mostly caused by diet), nor did we pay attention to the food poisoning of 50 people in a primary school, or the "upset stomach" of a group of people caused by the food in a restaurant, which seemed not to belong to food safety. The media will not focus on reporting (they will use articles of the size of "tofu blocks" to report food poisoning incidents of 50 people in a primary school, and such "tofu blocks" are not uncommon), nor will they hype online, nor will the public be nervous.

It is no surprise that foodborne diseases are the same as traffic accidents, strokes or heart attacks that happen every day. It is normal to be hospitalized or even die. Everyone was in a calm mood and could not stimulate nervous tension. For the government, the pressure is not great, much less than the "Sudan Red".

　 Common scientific principles can be used to prevent eating sickness

Whether you pay attention or not, eating food contaminated by biological hazards (such as bacteria, viruses, molds, parasites, etc.) has a risk of health damage. Because most pathogens (bacteria, etc.) are infectious, if they survive and do not proliferate after entering the human body (they must withstand the stomach acid environment), they will either invade cells and proliferate in cells to cause damage, and some will continue to cause systemic infection. The body damage will cause a series of defense and repair reactions, and people will get sick.

But it's not bacteria or viruses Or biological toxins (such as aflatoxin), it is inevitable to get sick. Because when biological hazards enter the human body, they sometimes fail to survive and proliferate, but disappear; Or the amount of food eaten is too small to cause damage. In addition, the person is very strong and healthy. If he is not old, weak, sick, young or pregnant, he will not get sick. Therefore, the level of risk is also closely related to the quantity.

When making risk assessment, scientists must consider both qualitative and quantitative issues. The study found that the relationship between the pathogenic risk of biological hazards and the intake "amount" (dose response) is very complex, and the characteristics of pathogens, hosts (animals or people), food, etc., as well as their interactions will have an impact. Emerging food microbiology and predictive microbiology are disciplines specialized in studying such problems. They not only have qualitative assessment (to clarify the nature of microorganisms), but also consider the growth, survival or inactivation of microorganisms, and use mathematical models to make quantitative descriptions.

Microbes are changing, and human life situations are changing, so science must keep pace with the times. As long as new microbial pathogens continue to evolve and be identified, the field of food safety needs to continuously study the relationship between microbial dose and response to make a more scientific and accurate assessment.

As mentioned earlier, the pathogenic mechanism of biological hazards can be divided into two categories, that is, pathogens directly damage the body or toxins produced by pathogens damage the body, and food can become the carrier or transmission medium of these two types of hazards. If the food is not processed or improperly processed, there may be biological hazards (such as pathogenic bacteria). For example, some pathogenic bacteria=microorganisms (such as bacteria and mold) can reproduce in food, and the longer they grow, the more they grow (at the beginning, they grow very fast in the middle stage, and later, because food is consumed, the nutrition they can provide decreases, and the quantity begins to decrease); Some pathogens do not proliferate in food (such as viruses and parasites), but they can exist in large quantities and are infectious (transmitted to food contacts and consumers through appropriate ways). For example, viruses involve 60% - 70% of foodborne infectious diseases.

Microbial growth needs some conditions, such as water, energy, nitrogen sources, vitamins (especially vitamin B) and related cofactors, minerals. If food cannot provide conditions for the growth of microorganisms (such as drying or dehydration), microorganisms cannot grow. For example, controlling the water content in grains such as rice below 14% can effectively prevent mold from growing in them. Of course, the relative humidity must be controlled to ensure that food does not absorb water from the external environment.

Organisms can protect themselves against microbial reproduction in the body. For example, the PH value of most fruits is low, which makes invading microorganisms unbearable (most microorganisms are suitable for growth and survival in the PH value range of 6.5-7.0, while the PH value range of microbial growth in food is wide, 4.0-9.5). Although the PH value of animals is conducive to the growth and survival of microorganisms, such as stomach acid, environment, etc. Other organisms naturally have substances that kill or inhibit microorganisms, such as eugenol in cloves, allicin in garlic, allyl isothiocyanate in mustard, etc.

External factors also affect the growth and survival of microorganisms. For example, heating treatment can eliminate or reduce the potential harm of pathogenic microorganisms in food. The most common methods are pasteurization, sterilization and cooking. In addition, the temperature range of microbial growth is relatively wide. There are microorganisms in air, soil, water, human body, animals and plants, which can become the source of vitamins for contaminated food. In addition, some processed foods are not completely sterile, but only in small quantities.

Therefore, food should be stored at a suitable temperature to control the growth of microorganisms (temperature requirements vary according to the type of microorganisms, for example, the United States requires that eggs be transported and stored below 5 ℃ all the time).

　　 How to control food contamination by pathogenic microorganisms?

There are three aspects to control food contamination by pathogenic microorganisms. First, manage environmental sanitation, such as feces, garbage, sewage, etc; Second, manage the sanitary conditions and processing technology of the enterprise. Food production, storage, transportation, sales and catering preparation must comply with the operating procedures of food hygiene; Third, various tests are also a regulatory means and deterrent tool.

From the operational level, food production should be strictly in accordance with the requirements of Good Practice (GMP), Hazard Analysis and Critical Control Point (HACCP); In family life, scientific and hygienic operation specifications should also be observed.

Finally, we should know that microorganisms have strong adaptability. Many bacteria can survive and reproduce under extreme conditions (such as low temperature or high temperature, high salt, low PH value, etc.), and can survive against the killing effect (such as the killing of gastric acid environment, immune system, etc.) caused by biological self-protection. The improvement of food processing technology, agricultural technology and the use of antibiotics will also change the microbial flora. Take Escherichia coli as an example. Human beings have struggled with it for two centuries. They are also constantly changing in the struggle, and their drug resistance is getting higher and higher. In 2011, the pathogenic strains of German Escherichia coli can resist seven or eight kinds of antibiotics. Human beings still have a long way to go if they want to keep away from pathogenic bacteria based on science and ensure food safety.