GB 4789.38-2025 PDF English
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| Standard ID | Contents [version] | USD | STEP2 | [PDF] delivery | Name of Chinese Standard | Status |
| GB 4789.38-2025 | English | 170 |
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National food safety standard - Food microbiological examination - Counting of Escherichia Coli
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| GB 4789.38-2012 | English | 70 |
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National Food Safety Standard -- Microbiological Examination of Food Hygiene -- Enumeration of Escherichia Coli
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| GB/T 4789.38-2008 | English | 599 |
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Microbiological examination of food hygiene -- Enumeration of escherichia coli
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GB 4789.38-2025: National food safety standard - Food microbiological examination - Counting of Escherichia Coli
---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/GB4789.38-2025
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
National Food Safety Standard - Food Microbiological
Examination - Counting of Escherichia Coli
Issued on. MARCH 16, 2025
Implemented on. SEPTEMBER 16, 2025
Issued by. National Health Commission of the People’s Republic of China;
State Administration for Market Regulation.
Table of Contents
Foreword... 3
1 Scope... 4
2 Inspection Principle... 4
3 Equipment and Materials... 4
4 Culture Medium and Reagents... 5
5 Inspection Procedures... 5
6 Operation Steps... 6
7 Results and Report... 8
8 Inspection Procedures... 8
9 Operation Steps... 9
10 Results and Report... 10
Appendix A Culture Medium and Reagents... 11
Appendix B Retrieval Table for the Most Probable Number (MPN) of Escherichia Coli
in Foods... 14
Appendix C Retrieval Table for the Most Probable Number (MPN) of Escherichia Coli
in Shellfish and Products... 15
Foreword
This Standard replaced GB 4789.38-2012 National Food Safety Standard - Food
Microbiological Examination - Counting of Escherichia Coli.
Compared with GB 4789.38-2012, the major changes of this Standard are as follows.
--- Modify the scope;
--- Delete terms and definitions;
--- Add inspection principle;
--- Modify equipment and materials, culture media and reagents;
--- Modify inspection procedures, operation steps, results and reports, and appendixes.
National Food Safety Standard - Food Microbiological
Examination - Counting of Escherichia Coli
1 Scope
This Standard specifies the method for counting Escherichia coli in foods.
The Method I of this Standard is applicable to the counting of Escherichia coli in foods with
low Escherichia coli content; the Method II is applicable to the counting of Escherichia coli in
foods with high Escherichia coli content, and is not applicable to the counting of Escherichia
coli in shellfish and products.
2 Inspection Principle
Escherichia coli ferments lactose at 44.5℃ to produce acid and gas; has β-glucuronidase
activity, can decompose 5-bromo-4-chloro-3-indole-β-D-glucuronide; and forms blue-green
colonies on Tryptone Bile X-glucuronide (TBX) agar. Based on the above characteristics of
Escherichia coli, MPN count and plate count are performed on it.
3 Equipment and Materials
In addition to routine sterilization and culture equipment in microbiological laboratories, other
equipment and materials are as follows.
3.1 Constant temperature incubator. 36℃ ± 1℃.
3.2 Refrigerator. 2℃ ~ 8℃.
3.3 Constant temperature water bath. 44.5℃ ± 0.2℃.
3.4 Constant temperature device. 48℃ ± 2℃.
3.5 Balance. With sensitivity of 0.1 g.
3.6 Homogenizer and sterile homogenizing bag, homogenizing cup, oscillator.
3.7 Test tube. 15 mm × 150 mm, 18 mm × 180 mm or other suitable specifications, as well as
small inverted tube (Durham’s tube) or other suitable gas collection device.
4 Culture Medium and Reagents
4.1 Phosphate buffer. See A.1 in Appendix A.
4.2 Physiological saline. See A.2.
4.3 Lauryl sulfate tryptone (LST) broth. see A.3.
4.4 EC broth. see A.4.
4.7 1 mol/L HCl. see A.7.
Method I MPN Counting Method of Escherichia Coli
5 Inspection Procedures
The inspection procedures for the MPN counting method of Escherichia coli are shown in
Figure 1.
6 Operation Steps
6.1 Dilution of specimen
6.1.1 Solid and semi-solid samples. Aseptically weigh 25 g of sample; put it into a sterile
homogenizing cup containing 225 mL of phosphate buffer or physiological saline; and
homogenize it at 8,000 r/min~10,000 r/min for 1 min ~ 2 min. Or put it into a sterile
homogenizing bag containing 225 mL of phosphate buffer or physiological saline; and beat it
with a slapping homogenizer for 1 min ~ 2 min to make a 1.10 sample homogenate.
6.1.2 Liquid samples. Use a sterile pipette to draw 25 mL of sample and place it in a sterile
conical flask containing 225 mL of phosphate buffer or physiological saline (an appropriate
number of sterile glass beads can be pre-placed in the flask) and mix thoroughly.
6.1.3 If necessary, use 1 mol/L NaOH or 1 mol/L HCl to adjust the pH of the sample
homogenate or liquid sample stock solution to 6.5~7.5.
6.1.4 Use a sterile pipette or micro pipettor to draw 1 mL of 1.10 sample homogenate; and
slowly inject it into a sterile test tube containing 9 mL of phosphate buffer or physiological
saline along the tube wall (be careful not to let the tip of the pipette or sucker touch the diluent
surface); and oscillate the test tube on an oscillator to mix well and make a 1.100 sample
homogenate.
6.2 Primary fermentation test
For each sample, select 3 appropriate sample homogenates with continuous dilutions (the stock
solution can be selected for liquid samples); inoculate 3 tubes of LST broth for each dilution (5
tubes of LST broth for each dilution of shellfish and products); and inoculate 1 mL of sample
homogenate into each tube of LST broth (if the inoculation volume exceeds 1 mL, add it to an
equal volume of double-material LST broth).
6.3 Re-fermentation test
Gently shake each gas-producing LST broth tube; take 1 loop of culture with an inoculation
loop, respectively; transfer it to the EC broth tube; and place it in a covered water bath.
6.4 Confirmation test
Gently shake each EC broth tube that produces gas; take the culture with an inoculation loop
and streak it on the TBX agar plate; culture at 36℃ ± 1℃ for 18 h ~ 24 h; observe the colonies
on the TBX agar plate; and the colonies of Escherichia coli on the TBX agar plate are blue-
green.
7 Results and Report
Based on the number of positive tubes for Escherichia coli in 3 appropriate serial dilutions,
report the MPN value of Escherichia coli per gram (ml) of sample according to the MPN index
table in Appendix B or C, expressed as MPN/g (mL).
8 Inspection Procedures
The inspection procedures for plate count method of Escherichia coli are shown in Figure 2.
9 Operation Steps
9.1 Dilution of sample
Perform according to 6.1.
9.2 Inoculation and culture
9.3 Selection of plate colony counts
If the typical colonies of Escherichia coli on TBX agar plates are blue-green, plates with typical
colony counts between 15 CFU ~ 150 CFU shall be selected; and count the typical colonies.
9.4 Calculation of Escherichia coli colony counts
9.4.1 If the typical colony count on only one dilution plate is within the counting range, the
result shall be calculated by the average of the typical colony counts of that dilution multiplied
by the corresponding dilution multiple.
9.4.2 If the typical colony counts on two continuous dilution plates are within the counting
range, the result shall be calculated according to Formula (1).
9.4.4 If the typical colony count on the plates of all dilutions is less than 15 CFU, the plate with
the lowest dilution shall be counted; and the result shall be calculated by multiplying the
average typical colony count of the lowest dilution by the corresponding dilution multiple.
9.4.5 If no typical colony grows on the plates of all dilutions (including the stock solution of
liquid sample), the result shall be calculated as less than 1 multiplied by the lowest dilution
multiple.
10 Results and Report
10.1 When the Escherichia coli colony count is less than 100 CFU, it shall be rounded off
according to the principle of "rounding off" and reported as an integer.
10.2 When the Escherichia coli colony count is greater than or equal to 100 CFU, the third digit
shall be rounded off according to the principle of "rounding off", and the first two digits shall
be taken, and the digits behind shall be replaced by 0;
10.3 If colonies grow on the blank control, the test result is invalid.
Appendix A
Culture Medium and Reagents
A.1 Phosphate buffer
A.1.1 Compositions
Potassium dihydrogen phosphate. 34.0 g
Distilled water. 500 mL
A.1.2 Preparation method
Stock solution. Weigh 34.0 g of potassium dihydrogen phosphate and dissolve it in 500 mL of
distilled water (or other experimental water that meets the requirements, the same below);
adjust the pH to 7.2 ± 0.2 with about 175 mL of 1 mol/L sodium hydroxide solution; dilute to
1,000 mL with distilled water; and store in a sealed refrigerator. Dilution solution. Take 1.25
mL of stock solution; dilute to 1,000 mL with distilled water; divide into appropriate containers;
autoclave at 121℃ for 15 min; and use for sample dilution.
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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