Exogenous pollution

作者：admin  点击次数：21  发布时间：2025-03-27

Exogenous pollution refers to the contamination of food by microorganisms in the external environment during the production, processing, transportation, storage, and sales of food, also known as secondary pollution. Exogenous pollution has important hygienic significance in terms of microbial contamination of food.
1. Exogenous biological pollution
Failure to comply with operating procedures during the processing, transportation, storage, sales, and cooking of food, which causes it to be contaminated by microorganisms, is called exogenous biological pollution, which is one of the main ways for food to be contaminated by microorganisms. The sources and causes of its pollution are as follows:
(1) Through water pollution The production and processing of food requires a large amount of water. At the same time, water is also an ingredient in many food processing. If water containing a large number of microorganisms, especially pathogenic microorganisms, is used, it will inevitably cause microbial contamination of food. Therefore, regardless of the type of food processing enterprise or business department, its production water must comply with the national "Sanitary Standards for Drinking Water" and the wastewater after use must be harmlessly treated. (2) Through air pollution The distribution of microorganisms in the air is uneven due to the influence of climate and the surrounding environment. Microorganisms in the air are attached to food with the blowing of sand, dust, or sedimentation. In addition, when people talk, cough or sneeze, sputum, mucus and saliva droplets containing microorganisms can directly or indirectly contaminate food through the air. It is almost inevitable that food is exposed to the air and contaminated by microorganisms. In order to reduce microbial contamination and obtain high-quality food, it is very necessary to pay attention to hygiene and purify the air in the processing site.
(3) Through soil pollution In nature, soil is the place with the most microorganisms. The surface soil can contain 10'~10°cfu/g of microorganisms, which is often the main source of food contamination. In addition to normal autotrophic microorganisms in the soil, the excrement of patients and sick animals, animal carcasses, slaughter and processing waste, sewage, etc. can also cause it to be infected with various pathogenic microorganisms. In addition, there are pathogenic microorganisms that can survive for a long time in the soil itself, such as meat bacteria. (4) Pollution in the production and processing process The production and processing process pollutes food in many ways. Almost every production and processing link can cause microbial contamination of food. For example, there are a large number of microorganisms on the fur of animals. During the slaughtering process, if the fur or skinning tools come into contact with the meat when skinning, the meat can be contaminated by microorganisms; if the intestines are cut when removing the intestines, the microorganisms can contaminate the meat; cutting tools and other equipment can become the medium for meat contamination by microorganisms. (5) Contamination during transportation. Food is often contaminated by microorganisms during transportation due to violations of operating requirements. For example, if the transportation vehicle is not clean, or even has been used to transport rotten or unclean items, and is used continuously without being thoroughly cleaned and disinfected before use, it can seriously contaminate fresh food. Or during transportation, the packaging is damaged, exposing the food or the milk bucket is not tightly covered, so that it is contaminated by microorganisms in the dust during transportation.
(6) Contamination during storage. During the storage process, food is often contaminated by microorganisms due to the environment. For example, if meat is stored in a cold, humid warehouse where mold grows, the meat will be contaminated by mold; or if it is stored in an open square, it will be contaminated by microorganisms in the wind and dust.
(7) Contamination by disease-causing pests As we all know, flies, rats, cockroaches, etc. carry a large number of microorganisms, especially pathogenic microorganisms. A fly can carry millions of bacteria on its body surface, and tens of millions of bacteria in its intestines. Pathogenic microorganisms such as Salmonella and Leptospira are often found in the feces and urine of rodents. Therefore, if food is bitten by disease-causing pests such as flies, rats, cockroaches, etc. during processing, transportation, storage, sales, and cooking, it will cause microbial contamination of food.
2. Exogenous chemical contamination
The contamination of food with toxic and harmful chemicals during processing, transportation, storage, sales, and cooking is called exogenous chemical contamination of food. This is another important aspect of food contamination by toxic chemicals. There are many reasons for this type of pollution, and the types of toxic chemicals involved are even more numerous. (1) Food pollution caused by toxic chemicals in the air In human production and life, waste gas emitted by fuel combustion and toxic chemicals in factory production are discharged into the air along with industrial waste gas. These harmful gases, under the action of airflow, gradually spread to the surroundings, naturally settle or fall on animal and plant food with raindrops, causing pollution. (2) Food pollution caused by toxic chemicals in water Water is essential for food production and processing. The main sources of chemical pollution in water are untreated industrial wastewater, slaughterhouse wastewater and domestic sewage, tanker oil, agricultural and veterinary drugs, and some heavy metal poisons deposited in the bottom of the water source. Chemical pollution in water is extremely complex. Commonly found are: inorganic substances, such as mercury, lead, arsenic, barium, chromium, vanadium and other heavy metals and their oxides, fluorides, etc.; organic substances, such as organic pesticides, organophosphorus pesticides, polychlorinated biphenyls, synthetic detergents, polycyclic aromatic hydrocarbons, phenols, etc. In addition, some reducing substances, such as sulfites, sulfides, ferrous salts and ammonia, are oxidized in water, consuming a large amount of dissolved substances in water, deteriorating water quality, and even causing the water to smell bad.
(3) Food pollution by toxic chemicals in soil Soil is a natural shelter for various wastes. The toxic chemicals in the soil mainly come from industrial "three wastes", pesticides, fertilizers, garbage, sewage, etc. When food comes into contact with such contaminated soil during processing, transportation, and storage, or when sand and dust settle on the surface of food, it will cause chemical pollution.
The toxic chemicals in the soil are mainly heavy metal elements such as mercury, lead, cadmium, chromium, copper, zinc, manganese, nickel, arsenic, and organic chlorine, organic phosphorus, etc.
The pollution of soil, air, and water is not isolated, but interrelated. The transformation and migration of pollutants between the three often form a cycle of environmental pollution, thereby causing direct or indirect pollution of food by toxic chemicals.
(4) The transportation process causes toxic chemicals to pollute food. There is a shortage of special vehicles for food transportation, and many transportation vehicles are used for both food and food. Poor management and lax systems in the loading, transportation, unloading, and storage process can cause food contamination. Mixing food with chemicals, pesticides, and veterinary drugs in the same vehicle is more likely to cause food contamination. Tricycles and flatbed trucks are often used for short-distance transportation without protective equipment, which are easily contaminated by chemicals in dust, sand, and rainwater.