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GB 4789.28-2024: National Food Safety Standards--Food Microbiology Testing--Quality Requirements for Medium and Reagents
GB 4789.28-2024
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
National food safety standards - Food microbiology testing -
Quality requirements for medium and reagents
ISSUED ON: FEBRUARY 08, 2024
IMPLEMENTED ON: AUGUST 08, 2024
Issued by: National Health Commission of PRC;
State Administration for market Regulation.
Table of Contents
Foreword ... 4
1 Scope ... 5
2 Terms and definitions ... 5
2.1 Quality control ... 5
2.2 Lots of media and reagents ... 5
2.3 Performance of media and reagents ... 5
2.4 Culture medium ... 5
2.5 Liquid culture medium ... 5
2.6 Solid media ... 6
2.7 Semi-solid medium ... 6
2.8 Transport media ... 6
2.9 Preservation medium ... 6
2.10 Suspension medium ... 6
2.11 Recovery medium ... 7
2.12 Enrichment medium ... 7
2.13 Selective enrichment medium ... 7
2.14 Non-selective enrichment medium ... 7
2.15 Isolation medium ... 7
2.16 Selective isolation medium ... 7
2.17 Non-selective isolation medium ... 7
2.18 Identification medium (specific medium) ... 7
2.19 Qualification media ... 8
2.20 Enumeration medium ... 8
2.21 Reference medium ... 8
2.22 Commercial ready-to-use media ... 8
2.23 Commercial dehydrated synthetic medium ... 9
2.24 Homemade culture medium ... 9
2.25 Reagents ... 9
2.26 Test strains ... 9
2.27 Standard strains ... 9
2.28 Standard reserve strains ... 9
2.29 Reserve strains ... 10
2.30 Working strains ... 10
3 Quality assurance of culture media and reagents ... 10
3.1 Supporting documents ... 10
3.2 Storage ... 11
3.3 Laboratory preparation of culture media ... 12
3.4 Use of culture medium ... 13
3.5 Disposal of culture medium ... 14
4 Preservation and use of test strains ... 15
4.1 General requirements ... 15
4.2 Commercially sourced test strains ... 15
4.3 Standard stock strains prepared in the laboratory ... 15
4.4 Reserve strains ... 15
4.5 Working strains ... 16
5 Quality requirements for culture media and reagents ... 16
5.1 Basic requirements ... 16
5.2 Microbiological requirements ... 17
6 Test methods of media and reagent performance ... 18
6.1 Quantitative test method for non-selective isolation and enumeration of target bacterial
growth rate in solid culture media ... 18
6.2 Test methods for selective isolation and enumeration of solid media ... 19
6.3 Semi-quantitative test method for non-selective enrichment media ... 21
6.4 Semi-quantitative testing method for selective enrichment media ... 22
6.5 Semi-quantitative test method for selective liquid enumeration media ... 23
6.6 Quantitative test methods for suspension media and transport media ... 24
6.7 Qualification media test methods ... 25
6.8 Test methods for experimental reagent ... 27
Appendix A Flow chart for media performance testing method ... 28
Appendix B Analysis of quality problems and reasons caused by incorrect preparation
of culture medium ... 32
Appendix C Preparation of standard reserve strains and working strains ... 34
Appendix D Medium components specified in food safety microbiological inspection
standards ... 36
Appendix E Quality control criteria for reference media in food safety microbiological
inspection standards ... 38
Appendix F Quality control criteria for culture media and reagents used in food
microbiology laboratories ... 44
Appendix G Test strain ... 96
Appendix H Spiral plate method ... 99
National food safety standards - Food microbiology testing -
Quality requirements for medium and reagents
1 Scope
This standard specifies the quality requirements for culture media and reagents used in
food microbiology testing.
This standard applies to the quality control of culture media and reagents for food
microbiology testing.
2 Terms and definitions
2.1 Quality control
Technical operations and activities undertaken to meet quality requirements.
2.2 Lots of media and reagents
The complete traceability unit of culture media and reagents, which refers to a
certain number of products produced in a specific production cycle and meeting
production quality requirements. These products have the same batch number.
2.3 Performance of media and reagents
The reaction of culture media and reagents to the test strain under certain conditions.
2.4 Culture medium
Substances in liquid, semi-solid or solid form, containing natural or synthetic
ingredients, used to ensure the reproduction, identification or maintenance of vitality
of microorganisms.
2.5 Liquid culture medium
A culture medium consisting of an aqueous solution containing one or more
Note: The identification medium that can be used for isolation and culture is called isolation
(identification) medium (such as: XLD agar).
2.19 Qualification media
A culture medium capable of producing one or more specific identification reactions
that usually does not require further confirmatory testing (e.g. lactose fermentation
tubes).
Note: The qualification medium used for isolation is called isolation (qualification) medium.
2.20 Enumeration medium
Selective (e.g., MYP agar) or non-selective media (e.g., plate enumeration agar)
capable of quantitatively enumeration microorganisms.
Note: Enumeration media may contain the characteristics of recovery and/or enrichment
media.
2.21 Reference medium
The high-quality culture medium which is specially prepared according to the
culture medium formula and used for quality control of the culture medium, to
ensure the quality of the culture medium for food microbiological testing.
For the reference culture medium, a nationally certified and accredited testing
agency with corresponding testing capabilities shall issue a testing report.
2.22 Commercial ready-to-use media
Liquid, solid or semi-solid culture media supplied in containers (e.g. dishes, test
tubes or other containers) or carriers in ready-to-use or molten form:
- Completely ready-to-use media (e.g. test strips, etc.);
- Culture media that need to be remelted (e.g. for plate pouring techniques);
- Culture media (such as preparation culture media) that need to be re-melted and
aliquoted (such as poured into plates) before use;
- Media that need to be re-melted, added, aliquoted before use (such as TSC media
and Baird Parker agar).
Note: Please refer to Appendix F for the test methods and evaluation criteria of the test
pieces. If it cannot refer to the parts of Appendix F (such as colony morphology), it can refer
to the operating instructions provided by the manufacturer.
2.23 Commercial dehydrated synthetic medium
Dry culture medium that needs to be added with water and processed before use
(such as powder, small particles, freeze-dried, etc.):
- Complete culture medium, which has no need to add other ingredients when using;
- Incomplete culture medium, which needs to add additives when using.
2.24 Homemade culture medium
According to the specific ingredients of the complete formula of the culture medium,
the culture medium as prepared by the laboratory.
2.25 Reagents
Reagents for food microbiological testing and supporting reagents for culture media
preparation.
2.26 Test strains
Microorganisms commonly used for media performance testing.
Note: Test strains can be further defined depending on their origin (see 2.27 ~ 2.30).
2.27 Standard strains
Strains which obtained directly from professional culture preservation agency and
defined at least to th...