National food safety standard - Food microbiological examination - Quality requirements for culture medium and reagents
1 Scope
This standard specifies the quality requirements of culture medium and reagents for food microbiological examination.
This standard is applicable to the quality control of culture medium and reagents for food microbiological examination.
2 Terms and definitions
2.1
quality control
technical operations and activities taken to meet quality requirements
2.2
lots of culture medium and reagents
complete traceable unit of culture medium 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 lot number
2.3
performance of culture medium and reagents
reaction of the culture medium 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
medium consisting of an aqueous solution containing one or more ingredients (e.g., buffered peptone water)
2.6
solid culture medium
culture medium formed by adding a certain amount of solidified material (such as agar) to a liquid culture medium, boiled or sterilized by moist heat, cooled to room temperature, and solidified into a solid state
A solid culture medium poured into a plate is generally referred to as a "plate"; while solid culture medium poured into a test tube and placed obliquely is generally referred to as "agarslant" when the culture medium solidifies.
2.7
semi-solid culture medium
culture medium formed by adding a small amount of solidified material (such as agar) to a liquid culture medium, boiled or sterilized by moist heat, cooled to room temperature, and solidified into a semi-solid
2.8
transport medium
medium that protects and maintains microbial activity and does not allow significant microbial proliferation or reduction after sampling and prior to laboratory processing
The transport medium generally does not contain substances that enable microbial proliferation, but the culture medium shall be capable of protecting the strain (e.g., buffered glycerol-sodium chloride solution transport medium).
2.9
preservation medium
culture medium (such as nutrient agar agarslant) used to protect and maintain the vitality of microorganisms within a certain period of time, prevent the adverse effects of long-term storage on them, or make them easy to recover after long-term storage
2.10
suspension medium
culture medium (such as phosphate buffer solution) that disperses the microorganisms of the test sample into the liquid phase without causing proliferation or inhibition throughout the entire contact process
2.11
resuscitation medium
culture medium that can repair damaged or stressed microorganisms and restore the normal growth ability of microorganisms, but does not necessarily promote microbial reproduction (such as tryptone soybean broth)
2.12
enrichment medium
generally a liquid culture medium that can provide a specific growth environment for microbial reproduction
2.13
selective medium for enrichment
culture medium (e.g., TTB medium) capable of allowing specific microorganisms to propagate therein, while partially or completely inhibiting the growth of other microorganisms
2.14
non-selective medium for enrichment
culture medium (such as nutrient broth) capable of ensuring the growth of a variety of microorganisms
2.15
isolation medium
solid or semi-solid culture medium that supports the growth of microorganisms
2.16
selective medium for isolation
solid culture medium (e.g., XLD agar) that supports the growth of specific microorganisms and inhibits the growth of others
2.17
non-selective medium for isolation
solid culture medium (e.g., nutrient agar) that does not selectively inhibit microorganisms
2.18
differential medium (specific medium)
culture medium capable of identifying one or more physiological and/or biochemical properties of a microorganism (e.g., eosin-methylene blue agar)
Note: The differential medium that can be used for isolation culture is referred to as an isolation (differential) medium (e.g., XLD agar).
2.19
identification medium
culture medium (e.g., a lactose fermentation tube) capable of producing one or more specific identification reactions without typically requiring further confirmation tests
Note: The identification medium used for isolation is referred to as an isolation (identification) medium.
2.20
enumeration medium
selective (e.g., MYP agar) or non-selective medium (e.g., plate enumerating agar) capable of quantitative enumerating of microorganisms
Note: The enumeration medium may contain the characteristics of the resuscitation and/or enrichment medium.
2.21
reference medium
culture medium specially prepared according to the formula of the culture medium, with excellent quality, which is used for the quality control of the culture medium to ensure the quality of the culture medium for food microbiological examination
The reference medium is required to be tested by a testing institution that has the corresponding testing capabilities and has obtained national certification and accreditation qualifications to issue a testing report.
2.22
commercial ready-to-use medium
liquid, solid or semi-solid culture medium supplied in a container (e.g., a plate, test tube or other container) or carrier in a ready-to-use form or in a ready-to-use form after melting:
——fully ready-to-use culture medium (e.g., test pieces, etc.);
——culture medium to be re-melted (e.g. for plate pouring techniques);
——culture medium (e.g. preparation medium) that needs to be re-melted and dispensed (e.g. poured into a plate) before use;
——culture medium (e.g., TSC medium and Baird Parker agar) that needs to be re-melted, substance added and dispensed before use.
Note: See Annex F for the test method and evaluation standard of the test piece. The parts that cannot be referred to in Annex F (such as colony morphology) may be executed according to the operating instructions provided by the manufacturer.
2.23
culture medium prepared from commercially dehydrated formulations
dry culture medium (such as powder, small particles, freeze-dried, etc.) that needs to be added with water and treated before use:
——complete culture medium, with no other ingredients need to be added when used;
——incomplete culture medium, with additives need to be added when used.
2.24
self-prepared culture medium
culture medium prepared by the laboratory according to the specific ingredients of the complete formula of the culture medium
2.25
reagents
reagents for food microbiological examination and supporting reagents for culture medium preparation
2.26
test strain
microorganisms commonly used in culture medium performance testing
Note: The test strains can be further defined according to their origin (see 2.27 to 2.30).
2.27
reference strain
strains obtained directly from specialized strain depositories and defined at least to the genus or species level. They are classified and described according to strain properties, and are preferably those derived from food, water or the environment in which they are produced
2.28
reference stocks
a set of identical independent strains obtained by transplanting the reference strains in the laboratory for one generation
2.29
stock strain
independent strains obtained from the reference stock transplant generation
2.30
working culture
strain obtained from a reference material/reference sample or a reference stock, a stock strain transplant generation directly used for testing use
Note: Reference material/reference sample refers to a material that contains a certain number of viable bacteria, meets the intended use and is sufficiently homogeneous and stable.
3 Quality assurance of medium and reagent
3.1 Certification documents
3.1.1 Documents provided by the manufacturer
The manufacturer shall provide the following information (electronic text can be provided):
——Various ingredients of the culture medium or reagent, names and product numbers of added ingredients;
Foreword
1 Scope
2 Terms and definitions
2.1 Quality control
2.2 Batch of culture mediums and reagents
2.3 Properties of culture mediums and reagents
2.4 Culture medium
2.5 Liquid culture medium
2.6 Solid culture medium
2.7 Semi-solid culture medium
2.8 Transport medium
2.9 Preservation medium
2.10 Suspension medium
2.11 Resuscitation medium
2.12 Enrichment medium
2.13 Selective enrichment medium
2.14 Non-selective enrichment medium
2.15 Isolation medium
2.16 Selective isolation medium
2.17 Non-selective isolation medium
2.18 Differential medium
2.19 Identification medium
2.20 Counting medium
2.21 Reference medium
2.22 Commercial ready-to-use medium
2.23 Commercial dehydrated synthetic medium
2.24 Self-made medium
2.25 Reagent
2.26 Testing culture
2.27 Type culture strain
2.28 Reference stock
2.29 Stock culture
2.30 Working culture
3 Quality assurance of mediums and reagents
3.1 Supporting documents
3.2 Storage
3.3 Laboratory preparation of medium
3.4 Use of medium
3.5 Disposal of medium
4 Preservation and use of testing culture
4.1 General requirements
4.2 Commercial testing culture
4.3 Type culture strains prepared in laboratory
4.4 Stock culture
4.5 Working culture
5 Quality requirements of mediums and reagents
5.1 Basic requirements
5.2 Microbiological requirements
6 Methods of property test of mediums and reagents
6.1 Quantitative test methods of non-selective isolation and solid counting mediums target bacteria growth rate
6.2 Test methods of selective isolation and solid counting mediums
6.3 Semi-quantitative test method of non-selective enrichment medium
6.4 Semi-quantitative test method of selective enrichment medium
6.5 Semi-quantitative test method of selective liquid counting medium
6.6 Quantitative test methods of suspension medium and transport medium
6.7 Test method of identification medium
6.8 Test methods for experimental reagents
Annex A Flow chart for test method of property test of mediums
Annex B Quality problems and cause analysis of incorrect preparation of medium
Annex C Preparation of reference stock and working culture
Annex D Medium components specified in the microbiological examination standards for food safety
Annex E Quality control standards of reference medium in the microbiological inspection standards for food safety
Annex F Quality control standards of mediums and reagents used in food microbiology laboratories
Annex G Testing culture
Annex H Spiral plate method
