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GB 4789.15-2016: National food safety standard - Food Microbiological Examination: Enumeration of Moulds and Yeasts Delivery: 9 seconds. True-PDF full-copy in English & invoice will be downloaded + auto-delivered via email. See step-by-step procedure Status: Valid GB 4789.15: Historical versions
Similar standardsGB 4789.15-2016: National food safety standard - Food Microbiological Examination: Enumeration of Moulds and Yeasts---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GB4789.15-2016 GB NATIONAL STANDARD OF THE PEOPLE’S REPUBLIC OF CHINA National Food Safety Standard – Food Microbiological Examination. Enumeration of Moulds and Yeasts Issued on. OCTOBER 19, 2016 Implemented on. APRIL 19, 2017 Issued by. National Health and Family Planning Commission of the PRC Table of ContentsForeword... 3 1 Scope... 4 2 Equipment and materials... 4 3 Culture Medium and Reagents... 5 4 Examination procedures... 5 5 Operation Steps... 6 6 Results and Report... 7 7 Operation Procedures... 8 Appendix A Culture Medium and Reagents... 10ForewordThis Standard replaced GB 4789.15-2010 National Food Safety Standard – Food Microbiological Examination. Enumeration of Moulds and Yeasts; and SN/T 2552.3- 2010 Microbiological Examination Method for Milk and Milk Products Hygiene – Part 3.Colony-Count Method of Yeast and Moulds. Compared with GB 4789.15-2010, this Standard has the major changes as follows. --- Modify the equipment and materials; --- Modify the culture medium and reagents; --- Modify the examination procedures and operation steps; --- Modify the results and report; --- Modify the Appendix A; --- Modify the Appendix B into Method 2. National Food Safety Standard – Food Microbiological Examination. Enumeration of Moulds and Yeasts1 ScopeThis Standard specifies the enumeration method of moulds and yeasts in the food. The Method 1 in this Standard is applicable to the enumeration of moulds and yeasts in various foods; while the Method 2 is applicable to the enumeration of moulds in the canned tomato sauce and tomato juice.2 Equipment and materialsIn addition to the biological laboratory routine sterilization and cultivating equipment, other equipment and materials are as follows. 2.1 Incubator. 28°C±1°C. 2.2 Beat-type homogenizer and homogeneous bag. 2.3 Electronic balance. sensitivity of 0.1g. 2.4 Sterile conical flask. capacity of 500mL. 2.5 Sterile pipette. 1mL (with 0.01mL scale), 10mL (with 0.1mL scale). 2.6 Sterile test tube. 18mm × 180mm. 2.7 Vortex mixer. 2.8 Sterile flat plate. diameter of 90mm. 2.9 Constant temperature water batch. 46°C±1°C. 2.10 Microscope. 10× ~ 100×. 2.11 Micro-pipettor and tip. 1.0mL. 2.12 Refractometer. 2.13 Hearst measuring slide. special side with standard measurement room. 2.14 Cover glass. 2.15 Micrometer. slide with standard scale.3 Culture Medium and Reagents3.1 Normal saline. see A.1. 3.2 Potato dextrose agar. see A.2. 3.3 Rose Bengal agar. see A.3. 3.4 Phosphate buffer. see A.4.4 Examination proceduresThe examination procedures of mould and yeast plate counting method can refer to Figure 1.5 Operation Steps5.1 Sample dilution 5.1.1 Solid and semi-solid samples. weigh 25g of sample; add 225mL of sterile diluent (distilled water or normal saline or phosphate buffering solution), sufficiently shake; or use beat-type homogenizer to beat for 1min ~ 2min; then 1.10 sample homogenous solution is prepared. 5.1.2 Liquid sample. use the sterile pipette to absorb 25mL of sample into 225mL appropriate container (can pre-set appropriate amount of sterile glass beads in the Sample Examination 5.1.3 Take 1mL of 1.10 sample homogenous solution to inject into the test tube containing 9mL of sterile diluent; change another 1mL sterile pipette to blow and absorb repeatedly; or mix evenly on the vortex mixer; such solution is 1.100 sample homogenous solution. 5.1.4 Operate as per 5.1.3, prepare the 10 times incremental serial sample homogenous solution. Once incrementally dilute, replace 1 piece of 1mL sterile pipette. 5.1.5 According to the evaluation of the sample pollution, select the sample homogenous solution (liquid sample can include the stock solution) with 2 ~ 3 appropriate dilution; when performing the 10 times incremental dilution, absorb 1mL of sample homogenous solution for each dilution, and place into 2 sterile flat plates, respectively. 5.1.6 Timely cool off the 20mL ~ 25mL of potato dextrose agar or rose Bengal agar (can place into a 46°C±1°C constant temperature water bath for thermal insulation) to 46°C, then pour into the flat plate; rotate the flat plate to make it mix evenly. 5.2 Cultivation After agar solidification, upright the flat plat, and place into 28°C±1°C incubator for cultivation; observe and record the cultivation results to the first 5d. 5.3 Colony counting Perform visual examination; if necessary, use magnifier or low power lens to record dilution factor, and corresponding number of moulds and yeast colonies. It is expressed by the Colony-Forming Unit (CFU).6 Results and Report6.1 Results 6.1.1 Calculate the average value of two flat plate colonies at the same dilution, then multiply the average value by the corresponding dilution factor. 6.1.2 If the number of colonies on two dilution flat plate is in 10CFU ~ 150CFU, calculate the corresponding values as per the provisions of GB 4789.2. 6.1.3 If the number of colonies on all flat plates are greater than 150CFU, count the flat plate with the maximum dilution; other plates are recorded as unacceptable; the result shall be calculated through the average number of colonies multiply by the maximum dilution factor. 6.1.6 If the number of colonies on the flat plate with all dilution aren’t in 10CFU ~ 150CFU, thereof, one part is less than 10CFU or greater than 150CFU, then it shall be calculated through the average number of colonies closest to 10CFU or 150CFU multiply by the dilution factor. 6.2 Report 6.2.1 The number of colonies shall be rounded off as per the “tetrahedral hybridization” principle. If the number of colonies are within 10, take one effective digit to report; if the number of colonies are in 10 ~ 100, take two effective digits to report. 6.2.2 When the number of colonies are greater than or equal to 100, after the first three digits are rounded off as per the “tetrahedral hybridization” principle, the result shall be expressed by the first two digits plus “0” replacing the following digit capacities; or expressed by the index number of 10; 6.2.3 If the colony appears on the blank control flat plate, then such test results are invalid. 6.2.4 The weight sampling shall be reported in unit of CFU/g; while the volume sampling shall be reported in unit of CFU/mL; report, or respectively report the number of moulds and/or yeasts.7 Operation Procedures7.1 Preparation of the sample for examination. take appropriate amount of sample for examination; add distilled water to dilute to the refractive index to be 1.3447 ~ 1.3460 (i.e. concentration is 7.9% ~ 8.8%); then backup. 7.2 Microscope calibration of standard field of view. magnify the microscope for 90× ~ 125×, adjust the standard field of view; so that its diameter is 1.382mm. 7.3 Smear. 7.4 Observation. place the prepared slide under the standard field of view of microscope to observe. Generally, one sample for examination shall be observed for 50 fields of view each person. The same sample for examination shall be observed by two persons. 7.5 Results and calculation. under the standard field of view, if finding the mould hypha length exceed 1/6 of standard field of view (1.382mm) or the total length of three hyphae exceed 1/6 of standard field of view (i.e. 1 block of micrometer), then it shall be recorded as positive (+), otherwise, it shall be recorded as negative (-). 7.6 Report. the whole number of positive field of views in every 100 field of views are reported as the visual field percentage of moulds (visual field %).Appendix ACulture Medium and Reagents A.1 Normal saline A.1.1 Components Sodium chloride 8.5g Distilled water 1000mL A.1.2 Preparation Add sodium chloride into 1000mL of distilled water, mix till it is fully dissolved; after packaging separately, sterilize for 15min at 121°C, then backup. A.2 Potato dextrose agar A.2.1 Components A.2.2 Preparation Peel the potato and cut it into blocks; add 1000mL of distilled water, and boil for 10min ~ 20min. Use gauze to filter, add distilled water to 1000mL. Add dextrose and agar, heating for dissolution; after packaging separately, sterilize for 15min at 121°C, then backup. A.3 Rose Bengal agar A.3.2 Preparation Add the above components into the distilled water, heating for dissolution; make up sufficient distilled water to 1000mL; after packaging separately, sterilize for 15min at 121°C; store in the dark for backup. A.4 Phosphate buffering solution A.4.1 Components Potassium dihydrogen phosphate 34.0g Distilled water 500mL A.4.2 Preparation Stock solution. take 34.0g of potassium dihydrogen phosphate and dissolve into 500mL of distilled water; adjust with 175mL of 1mol/L sodium hydroxide to pH value to be 7.2±0.1; use distilled water to dilute to 1000mL then store in the refrigerator. Diluent. take 1.25mL of stock solution; use distilled water to dilute to 1000mL; ......Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al. Tips & Frequently Asked Questions:Question 1: How long will the true-PDF of English version of GB 4789.15-2016 be delivered?Answer: The full copy PDF of English version of GB 4789.15-2016 can be downloaded in 9 seconds, and it will also be emailed to you in 9 seconds (double mechanisms to ensure the delivery reliably), with PDF-invoice.Question 2: Can I share the purchased PDF of GB 4789.15-2016_English with my colleagues?Answer: Yes. The purchased PDF of GB 4789.15-2016_English will be deemed to be sold to your employer/organization who actually paid for it, including your colleagues and your employer's intranet.Question 3: Does the price include tax/VAT?Answer: Yes. 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