1 Scope
This standard specifies the basic principles and requirements for food microbiological examination.
It is applicable to the food microbiological examination.
2 Basic Requirements for Laboratory
2.1 Examiners
2.1.1 The examiners shall have received education and training on microbiology and obtained corresponding qualification, and shall be able to correctly understand and conduct the examination.
2.1.2 The examiners shall have a good mastery of knowledge on laboratory biosafety operation and disinfection.
2.1.3 The examiners shall maintain personal hygiene and tidiness during examination, to prevent human contamination to samples.
2.1.4 The examiners shall abide by the requirements of safety measures concerned during examination to ensure personal safety.
2.1.5 The personnel with color vision disorder shall not undertake the tests involved with color distinguishing.
2.2 Environment and facility
2.2.1 The laboratory environment shall not affect the accuracy of examination results.
2.2.2 The experiment area shall be clearly separated from the office area.
2.2.3 The working area and general layout of the laboratory shall satisfy the demands of examination work. To avoid cross contamination, the laboratory layout should adopt single-direction workflow.
2.2.4 The temperature, humidity, cleanliness, as well as illuminance, noise, etc. in the laboratory shall meet the work demands.
2.2.5 Food sample examination shall be conducted in clean area which shall have obvious mark.
2.2.6 The pathogenic microbe separation identification shall be carried out in Class II or above biosafety laboratory.
2.3 Experimental apparatus
2.3.1 The experimental apparatus shall satisfy the demands of examination work. See A.1 for the common apparatus.
2.3.2 Experimental apparatus shall be arranged under proper environment condition, be convenient for maintenance, cleaning, sterilization and calibration, as well as keep tidy and in good working condition.
2.3.3 Regular inspection and/or calibration (marking) and maintenance shall be conducted for experimental apparatus so as to ensure their working performance and operation safety.
2.3.4 Routine monitoring record and service record shall be kept for experimental apparatus.
2.4 Examination appliances
2.4.1 The examination appliances shall meet the demand of microbiological inspection; see A.2 for the examination appliances in common use.
2.4.2 The examination appliances shall keep clean and/or aseptic before use.
2.4.3 Examination appliances that required for sterilization shall be placed in special vessel or enveloped with suitable material (like special wrapping paper, aluminium foil, etc.) or sealed, so as to ensure the sterilization effect.
2.4.4 The storage environment for examination appliances shall be dry and clean; the sterilized and unsterilized appliances shall be placed separately and clearly marked.
2.4.5 The sterilized examination appliances shall have its sterilization temperature and duration as well as valid period recorded.
2.5 Medium and reagent
The preparation and quality control of medium and reagent shall comply with GB/T 4789.28.
2.6 Quality-control strains
2.6.1 The laboratory shall preserve standard strains that meet the experiment demands.
2.6.2 The examination shall adopt traceable standard strains preserved in the professional microbial strain preservation agency or authority.
2.6.3 The preservation and subculture of standard strain shall comply with GB 4789.28.
2.6.4 The isolated strain (wild strain) passing the identification may be used for internal quality control of laboratory.
3 Sampling
3.1 Sampling principle
3.1.1 The sample collection shall follow the principle of randomness and representativeness.
3.1.2 The sampling shall follow the sterile operation procedure, to prevent any possible external contamination.
3.2 Sampling scheme
3.2.1 The sampling scheme shall be determined according to examination objective, foodstuff characteristics, batch, examination method, microbiological hazard, etc.
3.2.2 There are Grade II and Grade III sampling schemes. n, c and m values are set for Grade II sampling scheme, while n, c, m and M values for Grade III sampling scheme.
n: number of the samples collected from one batch;
c: maximum permissible number of samples exceeding m;
m: the limit of acceptable microbiological index (Grade III sampling scheme) or the maximum safety amount (Grade II sampling scheme);
M: maximum safety amount of microbiological index.
Note 1: according to the index set in Grade II sampling scheme, it is allowable that the test value of corresponding microbiological index of at most c ones among n samples is larger than m.
Note 2: according to the index set in Grade III sampling scheme, among n samples, it is allowable that the test value of corresponding microbiological index is less than or equal to m for all samples and within m~M for at most c samples, but it is not allowable to exceed M.
For example: n=5, c=2, m=100CFU/g, M=1000CFU/g, indicating that for 5 samples collected from one batch, it is allowable if all samples have the examination results ≤m (≤100CFU/g) or if ≤2 samples have the result (X) within m~M (100CFU/gM (>1000CFU/g).
3.2.3 The sampling scheme of food shall comply with the food safety standard concerned.
3.2.4 Food sampling in food safety accident:
a) In case of food safety accident caused by contamination of batch products, the food sampling and judgment principle shall comply with 3.2.2 and 3.2.3. The food samples from the same batch shall be mainly collected.
b) In case of food safety accident caused by foods cooked or processed in restaurant or at home, the residual food sample on site shall be mainly collected, so as to satisfy the demands for causative agent judgment and pathogeny corroboration.
3.3 Sampling methods for various food
3.3.1 Prepackaged food
3.3.1.1 A proper amount of independently-packed food samples shall be collected from the same batch, and the sampling quantity of each sample shall meet the demand for microbiological index examination.
3.3.1.2 For independently-packed solid food less than or equal to 1,000g, or liquid food less than or equal to 1000mL, their samples from the same batch shall be adopted.
3.3.1.3 In case of independently-packed liquid food larger than 1000mL, shake the liquid or stir it with aseptic rod to reach homogeneity and then take a proper amount of sample into a aseptic sampling container as one food sample; in case of solid food greater than 1,000g, use aseptic sampler to take a proper amount of sample from different parts of one package and then put it into a aseptic sampling container as one food sample.3.3.2 Bulk food or field prepared food
Use aseptic sampling tool to collect samples from n different parts on site and put them into n aseptic sampling containers as n food samples. The sampling quantity of each sample shall meet the requirements of microbiological index examination institution.
3.4 Marking for samples
The samples shall be recorded and marked timely and accurately, including sampling person, sampling position, sampling time, sample name, sample source, batch number, amount, preservation condition, etc.
3.5 Storage and transportation of samples
3.5.1 The samples shall be delivered to the laboratory for examination as soon as possible.
3.5.2 The samples shall be kept intact during transportation.
3.5.3 The samples shall be stored under a condition similar to the original storage temperature or necessary measures shall be taken to prevent change of microbe quantity in the samples.
Contents
Foreword i
1 Scope
2 Basic Requirements for Laboratory
3 Sampling
4 Examination
5 Biosafety and Quality Control
6 Record and Report
7 Post-examination Disposal of Samples
Appendix A Routine Examination Appliances and Apparatus in Microbiological Laboratory
