Food pathogenic microorganisms are the key monitoring items for food safety, and their rapid detection (test) has always been a hot topic. In recent years, rapid detection and automation of microorganisms have progressed rapidly, and traditional methods of culture, separation, and biochemical identification relying on culture media have been time-consuming and labor-intensive. Rapid detection and automation combine microbiology, chemistry, molecular biology, biophysics, immunology, and serological testing techniques to isolate, detect, identify, and count microorganisms. Compared with traditional methods, it is faster, more convenient and more sensitive.
First, the "dry film method"
The "dry film method" is to use a non-toxic polymer material as a carrier to attach a specific medium and a color developing substance to the above, and to determine microorganisms in the food by the growth characteristics and color reaction of the microorganism on the medium. This is a rapid, qualitative and quantitative test strip and film microbial detection method, integrated with modern chemistry, polymer materials, microbiology, has reached the level of conventional quantification. The "dry film method" has the advantages of high accuracy, no need to configure reagents, simple and quick operation, easy storage and transportation, low price, and reduced environmental pollution, and is suitable for work in laboratories, production sites and field environments.
Application: Total colony test piece, coliform test piece, Salmonella test piece, Staphylococcus aureus test piece, tableware E. coli group test paper, water quality coliform test paper, etc.
Second, the colloidal gold method
Colloidal gold immunoassay, using colloidal gold as a tracer marker for antigen-antibody immunolabeling technology, has the advantages of high specificity and high sensitivity. It has a good application prospect for on-site screening, and its disadvantage is due to antigen-antibody transferability. For each type of object to be tested, special detection reagents and methods should be established. The popularity of this method is difficult, the cost is relatively high, and the detection limit is also high. So far, there is not much application in the field of food safety rapid detection.
Application: Staphylococcus aureus rapid test card, Salmonella test card.
Third, enzyme-linked immunosorbent assay (ELISA)
Enzyme-linked immunosorbent assay (ELISA) is a solid-phase enzyme method that combines the specificity of antibody antigen reaction with the efficient catalytic action of enzymes to determine antigens, as well as antibodies, for qualitative and quantitative detection.
Application: Test kits such as Salmonella, Escherichia coli and Legionella.
Fourth, the nucleic acid method
(1) Polymerase chain reaction (PCR) technology
Since its inception in 1985, PCR technology has been applied at various speeds in various fields of biological science. According to the sequence of the two ends of the DN segment to be tested, two primers capable of complementary to the DNA double strand are synthesized, and then the excess primer and 4 are added. A kind of deoxyribonucleic acid (dNTP), DNA polymerase and the DN segment to be tested are mixed into a reaction system, and subjected to three cycles of high temperature denaturation, annealing and extension to amplify the DNA. Generally, after 30 to 50 amplification cycles, the target DN segment can be amplified to millions of times. PCR technology is widely used in the rapid detection of food microorganisms.
(2) Loop-mediated isothermal amplification
In 2000, a new constant-temperature nucleic acid amplification technology for gene diagnosis was published by Japanese scholar Nafu, LAMP method, which is "Loop-mediated isothermal amplification". The technology has the advantages of high specificity, high sensitivity, simple operation, low requirements on instruments and equipment, and simple detection of the results, and does not require gel electrophoresis like PCR.
(3) Nucleic acid probe method
The nucleic acid probe method is also called nucleic acid molecule hybridization technology. The principle is that if two nucleic acid strands with different sources have complementary base sequences, they can specifically bind to the component hybridization strand; accordingly, according to the known sequence of DNA or RN The segment is labeled with an identifiable label (isotopic label, biotin label, etc.) to detect whether the same sequence is present in the unknown sample. This technique is applied to detect some common pathogens in foods, such as Escherichia coli, Salmonella, etc.
(4) Gene chip method
Gene chip technology is to cure tens of thousands of DNA probes on the surface of the support by in situ synthesis or microfabrication to obtain a two-dimensional DNA probe sequence, hybridize with the labeled sample, and detect the hybridization signal to the organism. Samples enable fast, parallel, and efficient detection or medical diagnosis. The advantages are high parallelism, diversification, miniaturization and automation. The disadvantage is that it is expensive, and the price of high-throughput microbial assay system is more than 1 million. Currently, it is mostly imported high-throughput microbial assay system;
At present, Guangzhou Double Helix Gene Technology Co., Ltd. series of food-borne pathogenic microorganism detection products are mainly developed using nucleic acid methods, including PCR, constant temperature fluorescence and PCR probe methods, covering Salmonella, Shigella, and monocyte proliferation. Listeria et al.
The pictures are all from the network;
references:
1. Li Shaowenå–† “Food Microbial Rapid Detection Technologyâ€
2, Shi Song, Shi Lei "Application of Rapid Detection Technology in Food Safety Management"
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