GB/T 37280-2019 PDF in English
GB/T 37280-2019 (GB/T37280-2019, GBT 37280-2019, GBT37280-2019)
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Determination of microorganisms in fluorescent brighteners product
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Standards related to: GB/T 37280-2019
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GB/T 37280-2019: PDF in English (GBT 37280-2019) GB/T 37280-2019
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 71.100.01; 87.060.10
G 55
Determination of Microorganisms
in Fluorescent Brighteners Product
ISSUED ON: MARCH 25, 2019
IMPLEMENTED ON: FEBRUARY 01, 2020
Issued by: State Administration for Market Regulation;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative References ... 4
3 Basic Requirements in the Laboratory ... 4
4 Apparatus ... 5
5 Incubation Media and Reagents... 6
6 Operating Procedures ... 7
7 Test Report ... 9
Determination of Microorganisms
in Fluorescent Brighteners Product
1 Scope
This Standard specifies the determination of the total number of colonies and molds in
the fluorescent brightener products.
This Standard is applicable to the determination of the total number of colonies and
molds in the fluorescent brightener products.
2 Normative References
The following documents are essential to the application of this document. For the
dated documents, only the versions with the dates indicated are applicable to this
document; for the undated documents, only the latest version (including all the
amendments) are applicable to this document.
GB/T 6682-2008 Water for Analytical Laboratory Use - Specification and Test
Methods
GB/T 8170-2008 Rules of Rounding off for Numerical Values & Expression and
Judgement of Limiting Values
3 Basic Requirements in the Laboratory
3.1 Environment
3.1.1 The laboratory environment shall not affect the accuracy of the test results.
3.1.2 The working area and office area of the laboratory shall be clearly separated.
3.1.3 The working area and overall layout of the laboratory shall be able to meet the
requirements of the inspection work. The laboratory layout shall adopt a single-
direction work process. The cultivation sites of the mold and general bacteria shall be
separately to avoid the cross-contamination.
3.1.4 The temperature, humidity, illuminance, noise and cleanliness of the laboratory
indoor environment shall meet the requirements of the work.
5 Incubation Media and Reagents
5.1 Laboratory-used water
The laboratory-used water shall meet the requirements for Class-II water specified in
GB/T 6682-2008.
5.2 Incubation media for determining the total number of colonies
5.2.1 Ingredients
Tryptic Soy Agar Medium (TSA). The ingredients include:
Casein Tryptone 15g
Phytone 5g
Sodium chloride 5g
Agar 12g
Water 1000mL
5.2.2 Preparation
Add the above ingredients into the water; boil and dissolve; adjust pH=7.3±0.2.
Dispense in the test tubes or conical flask; autoclave at 121°C for 15min.
5.3 Incubation media for determination of the total number of molds
5.3.1 Ingredients
Potato Dextrose Agar Medium (PDA). The ingredients include:
Potato extract 10g
Glucose 20g
Agar 13g
Chloramphenicol 0.1g
Water 1000mL
5.3.2 Preparation
Take the ingredients and dissolve into 1000mL of water, respectively; boil till dissolve;
after dispensing; autoclave at 121°C for 15min.
sterile plate; make two plates per dilution. Meanwhile, separately take 1mL of blank
diluent into two sterile plates as the blank control.
According to the measurement requirements, timely pour the 15mL ~ 20mL of cooled
off to 46°C incubation media (5.2) for determination of the total number of colonies or
the incubation media (5.2) (it may be placed in constant temperature water bath at
46°C±1°C) for determination of the total number of molds into each plate; rotate the
plate and make it mix evenly. After the agar was solidified, invert the plate; the
determination of the total number of colonies requires incubation for 48h±2h at
37°C±1°C; while the determination of the molds requires the incubation for 120h±2h at
28°C±1°C.
6.4 Colony counting
6.4.1 It may be visually observed; if necessary, use a magnifying glass or microscope
to observe; record the dilution factor and the corresponding number of colonies. The
colony counting shall be expressed by the colony-forming units (CFU).
6.4.2 If the blank plate has colony growth; then such test result is invalid; and shall be
re-tested.
6.4.3 Select the plate with the number of colonies between 30CFU and 300CFU and
without spreading colony growth to count the total number of colonies. The plate with
less than 30CFU shall record the specific number of colonies; while the plate with more
than 300CFU shall record as uncountable due to excessiveness. The number of
colonies per dilution shall take the average of the two plates.
6.4.4 When one of the plates has larger flaky colonies, it shall not be used; take the
plate without flaky colonies growth as the number of colonies of such dilution. If the
flaky colonies cover less than half of the plate, and the colonies on the other half of
plate distribute evenly; count half of the plate and be multiplied by 2, which represents
the number of colonies on one plate.
6.4.5 When there is a chain-like growth between colonies without obvious boundaries,
each single chain may be counted as one colony.
6.5 Calculation method of colony number
6.5.1 If the number of colonies on the plate with only one dilution is within the
appropriate counting range, calculate the average of the number of colonies on both
plates; then multiple the average by the corresponding dilution factor as the result of
the total number of colonies per gram (mL) of the sample.
6.5.2 If the number of colonies on the plate with two continuous dilutions is within the
appropriate counting range, then calculate according to Formula (1):
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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