[Overview]
Benzopyrene, also known as 3,4-benzopyrene, abbreviated as BaP, is a polycyclic aromatic hydrocarbon compound formed by the fusion of a benzene ring and a pyrene molecule. There are about ten types of benzopyrene. The more familiar ones to us are 1,2-benzopyrene, 3,4-benzopyrene and 4,5-benzopyrene. When the fuel is not completely burned, it will produce a deep yellow color. 1,2-benzopyrene has a strong carcinogenic effect, while 4,5-benzopyrene is an isomer of 1,2-benzopyrene but has no carcinogenic effect. Benzopyrene has no production or use value in industry and is generally only discharged with waste gas as a by-product formed during the production process. Benzopyrene was identified as the first chemical environmental carcinogen.
[Physical and Chemical Properties]
Physical and chemical properties: Benzopyrene is a relatively common indirect carcinogen and mutagen with high activity. It is a polycyclic aromatic hydrocarbon. The pure product itself is a colorless or light yellow needle-shaped crystal with five benzene rings linked together. The melting point and boiling point are relatively high. The melting point is 179°C, the boiling point is 475°C, the relative density is 1.35, the vapor pressure is very small, insoluble in water, easily soluble in benzene aromatic solvents, and slightly soluble in other organic solvents. Benzopyrene is usually adsorbed on particles of certain substances in the form of tiny molecules. Gas molecules exist in atmospheric smoke or in a colloid state, most of which are adsorbed on particulate matter. 3,4-benzopyrene emitted into the atmosphere, combined with aerosols in the atmosphere, has a higher probability of being inhaled into the lungs among inhalable dust particles with a diameter of less than 8 μm. These dust particles are inhaled into the lungs through the respiratory tract. Directly reaches the alveoli and blood, causing lung cancer and cardiovascular disease.
Chemical properties: Benzopyrene is prone to chemical changes under acidic conditions and is stable under alkaline conditions. Benzopyrene can undergo photooxidation reaction under the action of sunlight and fluorescence. Most polycyclic aromatic hydrocarbons have large conjugate systems, so they have fluorescent solutions. In general, as the molecular weight of polycyclic aromatic hydrocarbons increases, the melting and boiling points increase and the vapor pressure decreases. The conjugate system of PAHs and the arrangement of the benzene rings of the molecule affect the color, fluorescence and solubility of PAHs. Benzopyrene emits purple fluorescence under ultraviolet irradiation and blue fluorescence in organic solutions. It is orange-red in concentrated sulfuric acid solution with green fluorescence, so the fluorescence characteristics of benzopyrene are usually used for qualitative and quantitative detection.
Figure 1 shows benzopyrene
[Source]
1. Smoking and grilling food Incomplete combustion products such as charcoal, coal, and liquefied petroleum gas used when smoking and grilling food contain benzopyrene. In various barbecue foods such as smoked chicken and bacon, benzopyrene is produced in large amounts. This is because in smoked and grilled foods, the lamps used to smoke the meat contain a large amount of pollutants. The fat contained in the meat is in an undercooked state during the cooking process, which will produce a large amount of benzopyrene. Especially during the burning process of food, once the starch wrapped in the food is roasted into a charred state, a large amount of benzopyrene will also be produced in the starch, which will pose a strong risk of cancer if people eat it.
2. Food crops In the air that people depend on for survival, a large amount of BaP will also float in the air. The deposition of dust and particles through the atmosphere will contaminate food crops during the growth of plants, turning the crops into potential BaP vectors and contaminating the food crops themselves.
3. Stir-fried and baked foods BaP is also present in fried and baked foods. For example, in the process of frying tea leaves, the BaP contained in the tea is difficult to dissolve in the water under the action of high temperature, so it is difficult to dissolve in the tea leaves and soups. There is a large amount of benzopyrene in the slag. During the frying process, the benzopyrene content in food will be greatly enhanced at too high temperatures. In addition, the decomposition of protein and fat in baked foods at high temperatures, such as beef and mutton grilled under scorching fire, will also form benzopyrene during the decomposition of fat. These toxic and harmful substances are not easily decomposed, therefore, they will greatly increase the risk of human disease and cancer.
4. Edible vegetable oil Environmental pollution, exposure to pollutants during processing and transportation, or direct contact with pyrolysis gas during oil drying can cause BaP to be deposited in rapeseed. In addition, in the processing of oils such as melon seed oil and peanut oil, the finished oil that has been pressed and fried also has such risks. If the frying temperature is too high, the local temperature will be too high during the processing, so a large amount of BaP will be produced during pyrolysis. Studies by Wang Xuede and others have shown that when the roasting temperature of sesame exceeds 200°C, BaP exists in the pressed oil. In addition, factors such as smoke and temperature during the processing of food oil also have a greater impact on sesame oil. In the process of deodorizing sesame edible oil, if the deodorization process is improperly selected, endogenous BaP will be formed during processing.
[Toxicological effects]
1. High carcinogenicity In the development of benzopyrene, it belongs to polycyclic aromatic hydrocarbons. It is one of more than 400 major carcinogens that have been identified by the medical community. Its toxicity ranks first among various types of polycyclic aromatic hydrocarbons. Benzopyrene entering the body will produce a large number of molecular intermediates after being metabolized by the human body. Therefore, it will change the structure of target cells and cause DNA damage. BaP�Asphalt-paved roads have caused food crops to be contaminated by benzopyrene.
5. Environmental pollution If the environment around us, such as the atmosphere and soil, is contaminated by benzopyrene, the crops in the environment will also be contaminated by benzopyrene, among which the pollution of fruits, vegetables and food crops is more obvious. In addition, the fog produced when smoking and the smoke produced during cooking can adhere to the surface of food, causing food to be contaminated by benzopyrene. More than 40 of the more than 600 toxic substances produced during smoking can directly cause cancer, and benzopyrene is one of the representatives.
[Main reference materials]
[1]Li Wenjuan. Research on the process and mechanism of activated carbon treatment of benzopyrene in corn oil[D]. Qilu University of Technology, 2016.
[2] Huang Yanfen, Tian Li. Research progress on benzopyrene in food[J]. Food Safety Guide, 2016(24):8-9.
[3]Shi Qiaoqiao, Xi Jun, Lu Qiyu. Research progress on benzopyrene in food[J]. Food Industry Science and Technology, 2014, 35(05):379-381+386.
[4]Shi Qiaoqiao. Research on rapid immunological detection technology of benzopyrene[D]. Henan University of Technology, 2014.
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