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GB 4789.15-2016 (GB4789.15-2016)

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GB 4789.15-2016: PDF in English

GB 4789.15-2016
National Food Safety Standard –
Food Microbiological Examination.
Enumeration of Moulds and Yeasts
Issued by. National Health and Family Planning Commission of the PRC
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Table of Contents
Foreword ... 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 ... 10
This 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 the second method.
National Food Safety Standard –
Food Microbiological Examination.
Enumeration of Moulds and Yeasts
1 Scope
This Standard specifies the enumeration method of moulds and yeasts in the food.
The first method in this Standard is applicable to the enumeration of moulds and yeasts
in various foods; while the second method is applicable to the enumeration of moulds
in the canned tomato sauce and tomato juice.
2 Equipment and materials
In 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.
bottle) containing sterile diluent (distilled water or normal saline or phosphate buffering
solution) or into the sterile homogeneous bag; sufficiently shake, or use beat-type
homogenizer to beat for 1min ~ 2min; and 1.10 sample homogenous solution is
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. Meanwhile, take 1mL of sterile diluent and add into 2 sterile flat plates to
make the blank control.
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. Place on
the horizontal platform till the culture medium is completely solidified.
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).
Select the flat plate with number of colonies 10CFU ~ 150CFU, count the moulds and
yeasts, respectively according to the colony morphology. When the moulds spreading
and growing over the whole flat plate, it can be recorded as the colony spread.
6 Results and Report
6.1 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.
Appendix A
Culture 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
Potato (peeled and cut into blocks) 300g
Dextrose 20.0g
Agar 20.0g
Chloromycetin 0.1g
Distilled water 1000mL
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
A.3 Rose Bengal agar
Peptone 5.0g
Dextrose 10.0g
Potassium dihydrogen phosphate 1.0g
Magnesium sulfate (anhydrous) 0.5g
(Above excerpt was released on 2017-08-11, modified on 2021-06-07, translated/reviewed by: Wayne Zheng et al.)
Source: https://www.chinesestandard.net/PDF.aspx/GB4789.15-2016