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GB/T 37280-2019 English PDF (GBT37280-2019)

GB/T 37280-2019 English PDF (GBT37280-2019)

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GB/T 37280-2019: Determination of microorganisms in fluorescent brighteners product

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.
GB/T 37280-2019
NATIONAL STANDARD OF THE
PEOPLE 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 and 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):

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