The concept and classification of food contamination

作者：admin  点击次数：23  发布时间：2025-03-26

Food contamination refers to the process in which toxic and harmful substances enter food under various conditions, causing changes in food safety, nutrition or sensory properties.
With the continuous production and application of various chemical substances, the types and sources of harmful substances have become more complicated. In every link of the entire process of food from planting, breeding to production, processing, storage, transportation, sales, cooking to the table, certain harmful factors may appear, causing food to be contaminated, thereby reducing the hygienic quality of food, and in severe cases causing varying degrees of harm to the human body.
Food contaminants can be divided into the following three categories according to their nature.
(I) Biological contamination
Biological contamination of food includes contamination by microorganisms, parasites, insects and viruses. Microbial contamination mainly includes bacteria and bacterial toxins, molds and mycotoxins. In addition to pathogenic bacteria that can cause food poisoning, zoonotic infectious diseases, etc., bacteria that appear in food also include non-pathogenic bacteria that can cause food spoilage and can be used as a sign of food contamination. Parasites and worm eggs mainly contaminate food indirectly through water or soil through the feces of patients and sick animals, or directly contaminate food. Insect pollution mainly includes beetles, beetles, moths in grains, flies, maggots in animal foods and fermented foods. Virus pollution mainly includes hepatitis virus, polio virus and foot-and-mouth disease virus. Other viruses are not easy to reproduce in food.
(II) Chemical pollution
Chemical pollution of food covers a wide range and is more complicated. It mainly includes:
(1) Pollutants from production, life and environment, such as pesticides, veterinary drugs, toxic metals, polycyclic aromatic hydrocarbons, N-nitroso compounds, heterocyclic amines, dioxins, trichloropropane, etc.
Harmful substances dissolved in food when food containers, packaging materials, transportation vehicles, etc. come into contact with food.
(2) Abuse of food additives.
(3) Substances produced during food processing and storage, such as harmful alcohols and aldehydes in wine (4)(5) Substances added during adulteration and counterfeiting.
(III) Physical pollutants Rational pollution mainly comes from complex and diverse non-chemical impurities, mainly from the following aspects: (1) Pollutants in food production, storage, transportation and sales, such as grass mixed in during grain harvesting, impurities in liquid food containers, dust and flies in the process of food transportation and sales, etc. (2) Food adulteration, such as sand and stone mixed in grain, water added to meat, and large amounts of sugar added to milk powder, etc. (3) Radioactive contamination of food, mainly due to the mining, smelting, production, application and accidents of radioactive materials.
The hazards caused by food contamination can be summarized as follows:
(1) Affecting the sensory properties of food;
(2) Causing food poisoning;
(3) Causing chronic harm to the body:
(4) Having teratogenic, mutagenic and carcinogenic effects on humans.
Food comes from animals, plants and microorganisms, and has many opportunities to be contaminated in various ways. The ways, sources and pathways of contamination are also multifaceted. Generally speaking, it can be divided into two aspects, namely endogenous pollution and exogenous pollution. (i) Endogenous pollution
Endogenous pollution is the pollution of food caused by biological, chemical and radioactive pollutants carried by food raw materials during the planting or breeding process, also known as primary pollution. There are roughly three types of endogenous pollution: 1. Endogenous biological pollution
Any organism that causes food pollution due to microorganisms or parasites carried by itself during its growth and life is called endogenous biological pollution. The causes of endogenous biological pollution in food are as follows: (1) Non-pathogenic and conditionally pathogenic microorganisms. These microorganisms often exist in animals and plants in certain groups and numbers. For example, the microorganisms present in the digestive tract of animals include Escherichia coli, Proteus, Enterococcus, Bacillus subtilis, Clostridium, etc. When the body is affected by adverse factors, the resistance of the animal and plant body decreases, and these microorganisms can invade the internal tissues to cause body pollution, becoming an important cause of raw material spoilage and food poisoning. (2) Pathogenic microorganisms When animals are infected by pathogenic microorganisms such as anthrax bacteria, brucella, mycobacterium tuberculosis, salmonella, foot-and-mouth disease virus, etc., the sick animals themselves are infected with pathogenic bacteria (or viruses), causing endogenous food contamination. These foods contaminated by pathogenic microorganisms can often make people sick. (3) Parasites During the planting and breeding process, animal and plant food raw materials can be infected with parasites such as Trichinella spiralis, Toxoplasma gondii, Echinococcus, etc. through various channels, which may cause people to become sick after eating infected food.
2. Endogenous chemical pollution
Chemical substances are widely used in various aspects such as industry, agriculture, medical care, and daily life. They often exist in the surrounding environment in the form of liquid (droplets), gas (aerosol) or solid (particles), and then enter the human body through the food chain. The organisms in each link of the food chain have the function of accumulating and concentrating environmental chemical toxins, so these foods will produce toxic effects after being ingested by the human body. For example, in order to reduce the cost of raising pigs, breeders drive pigs to garbage dumps for free-range feeding, and only provide drinking water every day. This kind of garbage pig contains harmful components, especially heavy metals that seriously exceed the standard. Some people have tested the heavy metal content in the blood, liver, lard, fat and lean meat of "garbage pigs" and found that the content of platinum in the fat of "garbage pigs" is 13 times higher than that of control pigs, and the content of lead is 8 times higher. Lead, mercury and chromium were not detected in the liver of control pigs, but they were all detected in the liver of "garbage pigs".
3. Endogenous radioactive contamination Radioactive substances in the environment can enter aquatic organisms and livestock and poultry through various pathways, causing food to be contaminated by radioactivity. The pollution of animals by "Sr" and "C" with longer half-lives and "Sr", "Ba" with shorter half-lives are of great significance in the food chain. These radionuclides not only accumulate in animal tissues and organs, but can also be excreted with milk. Radioactive substances I, Cs and Sr can enter egg products. Dairy products and egg products are important foods for humans. Once they are contaminated by radioactivity, they pose a great threat to human health.