GB 4789.15-2016 PDF English
US$70.00 · In stock · Download in 9 secondsGB 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 procedureStatus: Valid GB 4789.15: Evolution and historical versions
| Standard ID | Contents [version] | USD | STEP2 | [PDF] delivery | Name of Chinese Standard | Status |
| GB 4789.15-2016 | English | 70 |
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National food safety standard - Food Microbiological Examination: Enumeration of Moulds and Yeasts
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| GB 4789.15-2010 | English | 70 |
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National food safety standard -- Food microbiological examination: Enumeration of moulds and yeasts
| Obsolete |
| GB/T 4789.15-2003 | English | 239 |
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Microbiological examination of food hygiene -- Enumeration of molds and yeasts
| Obsolete |
| GB 4789.15-1994 | English | RFQ |
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Microbiological examination of food hygiene. Enumeration of molds and yeasts
| Obsolete |
| GB 4789.15-1984 | English | RFQ |
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Microbiological examination of food hygiene--Examination of molds and yeasts
| Obsolete |
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GB 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 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
Foreword
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 Method 2.
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 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 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.
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 Reagents
3.1 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 procedures
The examination procedures of mould and yeast plate counting method can refer to
Figure 1.
5 Operation Steps
5.1 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 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.
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 Procedures
7.1 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 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
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.
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