With the upcoming "two sessions" in 2013, food safety has gradually become the focus of the media and the masses. In recent years, although the country has maintained a high-pressure crackdown on food safety violations and crimes, food safety incidents are still emerging.
Microbiological testing is a must-do experiment in food safety testing. In the face of more and more frequent colony counts and classification statistics, the automatic colony counter / analyzer independently developed by Xunshu Technology Co. The excellent performance greatly saves the labor of experiment time, not only improves the accuracy but also realizes the digital management of the result report.
According to food microbiological testing standards, the test items have indicator bacteria: total colonies, coliforms, E. coli, and mold yeast. Pathogenic bacteria: Staphylococcus aureus, Salmonella, Listeria monocytogenes, E. coli 0157.
1. Total number of colonies
Counting points: Select a plate with a colony number between 30CFU and 300CFU and no colony growth to count the total number of colonies.
In terms of total colony count, Xunshuo automatic colony counter can handle pouring plate, coated plate, membrane filter plate, 3M paper sheet, etc., while saving high-resolution microbial colony pictures. For the filter membrane and 3M paper, the instrument's powerful software function can identify the characteristic grid lines and colony morphological features, and achieve one-click colony counting. The instrument's high-resolution CCD digital imaging technology and Xunshuo's patented Colonfast colony image intelligent recognition technology can perform colony counting with high efficiency of more than 500 per second. The minimum resolution can reach 0.01mm.
2. Coliform
The traditional most probable number of coliforms (MPN) method must go through: initial fermentation test, double fermentation confirmation test. The procedure is cumbersome, and a positive sample requires a minimum of 4 days to obtain a result.
In 2008, the country promulgated the new standard GB / T4789.3-2008 "Food Hygiene Microbiology Examination-Coliform Count". The second method in the standard, the coliform plate counting method, requires at least 42 hours to obtain the number of coliform bacteria.
Counting points: Select a plate with a number of colonies between 15 CFU and 150 CFU, and count the typical and suspected coliform colonies appearing on the plate, respectively. The typical colony is purple-red, with a red bile salt precipitation ring around the colony, and the colony diameter is 0.5 mm or larger.
Xunshuo automatic colony counter is based on the growth characteristics of coliform bacteria on VRBA medium. The high-definition camera and high-pixel CCD of the instrument and the color recognition of the colony intelligent identification software can quickly identify "purplish red with a red precipitation ring. "Characteristic colonies, complete the count of coliform bacteria.
3. Mold yeast
Key points for colony counting: According to GB 4789.15-2010, select a plate with a colony number of 10CFU ~ 150CFU, and count mold and yeast respectively according to the colony morphology. The spread of mold growth covering the entire plate can be recorded as uncountable. The number of colonies should be the average of the two plates.
For mold yeast counting, Colonfast colony image intelligent recognition technology has a special algorithm that supports automatic colony counting and concentration calculation of various pouring method plates, coating method plates, filter method plates, and spiral inoculation plates containing mold and yeast samples .
4. Staphylococcus aureus
Count the Baird-Parker plates according to the second method of GB 4789.10. Typical colonies: round, raised colonies
, Wet, with a diameter of 2mm ~ 3mm, the color is gray to black, the edge is light, the periphery is a turbid zone, and there is a transparent circle on the outer layer.
Xunshuo automatic colony counter uses color high-pixel CCD imaging and Colonfast image intelligent recognition software to quickly identify the typical Staphylococcus aureus colonies on Baird-Parker agar plates according to the characteristics of colony morphology, color, etc. in just 1 second. Calculate the number of typical colonies of Staphylococcus aureus.
5. Other strains
5.1 Lactic acid bacteria
Lactic acid bacteria refer to a group of non-spore-forming and Gram-positive bacteria whose main product of fermented sugar is lactic acid.
Detection method: take a 25mL sample and make a 10-fold gradient dilution, select 2 to 3 or more suitable dilutions, draw 1mL of the diluent into a sterilized plate, and make two plates for each dilution. The cooled culture medium is poured into a petri dish and mixed, and cultured at a constant temperature.
Xunshuo automatic colony counter uses color high-pixel CCD imaging and Colonfast image intelligent identification software to quickly identify typical lactic acid bacterial colonies (including Lactobacillus, Bifidobacterium, Streptococcus thermophilus) ), It takes only 1 second to calculate the number of typical colonies of lactic acid bacteria. Applicable to GBT 4789.35-2008 Food Hygiene Microbiology Examination for lactic acid bacteria in food.
5.2 Bacterial count (spiral plate method)
The colony count of spiral inoculation is based on the principle of Archimedes spiral, so that the sample is inoculated on the plate in the form of a logarithmic spiral. After the sample is inoculated, the colonies are distributed on the spiral trajectory, which becomes more and more thinner as the radius increases. A special counting grid is used to count the colonies on the plate from the outer periphery to the center of the plate to obtain the microorganisms in the sample.
Quantity. The spiral inoculation colony counting method has accurate sample addition, uniform colony distribution, and can greatly reduce or eliminate the sample dilution process, so it is widely used in colony counting experiments of foreign food and medicine.
Xunshu G6 automatic colony analyzer includes "Spiral inoculation plate analysis module (Shineso spiral plate counter)", in line with the AQSIQ SN standard and the US FDA spiral count standard, and is compatible with the analysis of well-known brand spiral inoculation instrument The compatibility of spiral plates inoculated in the United States (SBI) has been verified by well-known microbiological research and testing institutions in China.
5.3 Detection of antibiotic residues
The microbial inhibition method is the most widely used simple and low-cost method for antibiotic residue testing. The measurement principle is based on the growth inhibition of specific microorganisms to which antibiotics are sensitive, and the quantitative test or qualitative judgment of the antimicrobial drug residues in the sample is carried out through the size of the inhibition zone The diameter of the control inhibition zone is negative, otherwise it is positive). Xunshu_ZS automatic bacteriostatic circle measurement and analysis system is a powerful tool to replace the manual measurement and standardization of bacteriostatic circle.
Measurement type
One-dose potency test (1): suitable for US Pharmacopoeia
One-dose potency test (2): suitable for US Pharmacopoeia
Two-dose potency test: suitable for Chinese Pharmacopoeia 2010 edition
Three-dose method potency test: suitable for Chinese Pharmacopoeia 2010 edition
Combined calculation test: suitable for Chinese Pharmacopoeia 2010 edition
Detection accuracy
Repeatability self-test: relative error ≤0.01%, repeated measurement accuracy ≤0.002mm
Uniformity self-check: relative error≤0.05%
Potency measurement accuracy≤0.3%
Repetitive measurement accuracy of potency≤0.3%
Measurement difference between stations ≤0.2%
5.4 Detection of β-lactamase in milk and milk products
β-lactamase is a kind of bacteria-specific enzyme that breaks down antibiotics. It is possible that β-lactamase is detected in milk by the cow itself, or it may be produced by milk infected with some bacteria during processing . Another possibility is that β-lactamase is added artificially during the processing because it can decompose the β-lactam antibiotics left in the milk and cover the antibiotics.
Principle: This method uses a standard strain that is absolutely sensitive to penicillin drugs, uses sulbactam to specifically inhibit the activity of β-lactamase, and adds penicillin as a control. By comparison, β-lactamase inhibitor is added and not added The size of the inhibition circle generated by the sample of the inhibitor is used to indirectly determine whether the sample contains β-lactamase drugs.
Xunshu sulbactam sensitive β-lactamase tester is a new product launched by Xunshu in 12 years. This instrument is a new type of instrument developed for the detection of β-lactamase in milk. It can accurately determine whether the verification of pure water is true. It can be easily combined with the accurate measurement of multiple bacteriostatic circles on the plate. It can be combined with the new standard of the Ministry of Health that reports "positive or negative test results of β-lactamase drugs". Realize the automated analysis of the presence of sulbactam sensitive β-lactamases.
Hangzhou Xunshu Technology Co., Ltd. is a high-tech company specialized in microbial analysis and testing technology research and equipment production. At present, it mainly produces automatic colony counters, spiral inoculation microbial colony analyzers, bacteriostatic circle measuring instruments, β-lactam analyzers, antibiotic potency analyzers, algae counters, algae auxiliary identification systems, zooplankton counters, biological Micro analysis system and other products. Products are widely used in scientific research, inspection and quarantine, quality supervision, environmental monitoring, disease control center, drug and biological product verification, food and pharmaceutical daily chemical production, and iron and petrochemical chemical power.
The company's headquarters is located in Hangzhou Xizi Lake High-tech Industrial Development Zone, with R & D department, manufacturing department, quality inspection center, microbiology laboratory, marketing department and so on. The company has a group of high-level experts and scholars at home and abroad, doctors returning from overseas, and professionals who are proficient in modern manufacturing and management. It has advanced international experimental conditions, modern manufacturing equipment, and a strict scientific management system. Many of the company's core technologies have won national invention patents, national software copyrights, and provincial and ministerial-level scientific and technological progress awards; some products have received "Medical Device Registration Certificate" and "Quality and Technology Supervision and Inspection Certificate", etc., and have been rated as China Instruments for two consecutive years. Top ten new products of instrument. Xunshu Technology Co., Ltd. is willing to provide sincere services to all sectors of society with consistent high-quality products and excellent services. Welcome to contact us.
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