This standard specifies the test method for the count of molds and yeasts in various types of grains, foods and beverages. This standard is applicable to the count of molds and yeasts in various types of foods and beverages. GB/T 4789.15-2003 Microbiological examination of food hygiene, count of molds and yeasts GB/T4789.15-2003 Standard download decompression password: www.bzxz.net

ICS07.100.30
National Standard of the People's Republic of China
GB/T4789.15—2003
Replaces GB/T4789.15--1994
Microbiological examination of food hygiene-Enumeration of molds and yeasts
Microbiological examination of food hygiene-Enumeration of molds and yeastsIssued on August 11, 2003
Ministry of Health of the People's Republic of China
Administrative Committee of Standardization of the People's Republic of China
Implementation on January 1, 2004
GB/T4789.15--2003
This standard revise GB/T4789.15-1994 "Microbiological examination of food hygiene-Enumeration of molds and yeasts".
Compared with GB/T4789.15-1994, the main modifications of this standard are as follows: The format and text of the standard text are modified in accordance with GB/T1.1-2000. Modify and standardize the "equipment and materials" in the original standard. -Delete "4.3 High-salt Czapek medium" in culture medium and reagents. From the date of implementation of this standard, GB/T4789.15-1994 will be abolished at the same time. Appendix A of this standard is an informative appendix.
This standard is proposed and managed by the Ministry of Health of the People's Republic of China. The drafting unit of this standard: Nutrition and Food Safety Institute of Chinese Center for Disease Control and Prevention. The main drafters of this standard: Luo Xueyun, Li Fengqin, Li Yuwei. This standard was first issued in 1984, revised for the first time in 1994, and this is the second revision. 102
1 Scope
Microbiological Examination of Food Hygiene
Count of Mold and Yeast
This standard specifies the test methods for counting mold and yeast in various types of grains, foods and beverages. This standard applies to the counting of molds and yeasts in various types of foods and beverages. 2 Normative References
GB/T4789.15—2003
The clauses in the following documents become the clauses of this standard through reference in this standard. For any dated referenced document, all subsequent amendments (excluding errata) or revisions are not applicable to this standard. However, the parties to an agreement based on this standard are encouraged to study whether the latest versions of these documents can be used. For any undated referenced document, the latest version shall apply to this standard. GB/T4789.2 Food hygiene microbiological examination Determination of total colony count GB/T4789.28-2003 Food hygiene microbiological examination Staining method, culture medium and reagents 3 Equipment and materials
3.1 Refrigerator: 0℃~4℃.
3.2 Constant temperature incubator: 25℃~28℃.
3.3 Constant temperature oscillator.
Microscope: 10X~100×.
Stand-plate drug balance: 0g~500g, accurate to 0.5g. Sterilized glass stopper conical flask: 300mL.
Sterilized wide-mouth bottle: 500mL.
Sterilized pipette: 1mL (with 0.01mL scale), 10mL (with 0.1mL scale). Sterilized plate: 90mm in diameter.
3.10 Sterilized test tube: 16mm×160mm.
Glass slide, cover slip.
Sterilized kraft paper bag, plastic bag.
Sterilized metal spoon, knife, etc. bzxZ.net
4 Culture medium and reagents
4.1 Potato-glucose agar culture medium, additional antibiotics: in accordance with 4.78 of GB/T4789.28-2003. 4.2 Red Bengal culture medium: in accordance with 4.80 of GB/T4789.28-2003. 4.3 Sterilized distilled water.
Test procedure
See Figure 1 for the test procedure.
GB/T4789.15—2003
6 Operating steps
Block food
25g+225mL sterile water
Powdered food
Make into several appropriate dilution solutions
Blanketed food
Tumbled food
25mL+225mL sterile water
Choose three appropriate dilutions, take 1mL of each and add into sterile plate. Add appropriate culture medium to each plate (potato-grape agar with antibiotics, high salt Czapek medium or red Bengal medium can be used) at 25℃~28℃54
Count the drops
6.1 Aseptically weigh 25g (mL) of the test sample and put it into a glass-stoppered conical bottle containing 225mL sterile water. Shake for 30min to make a 1:10 dilution.
6.2 Use a sterile pipette to draw 10mL of the 110 dilution solution and inject it into a sterile test tube. Use another 1mL sterile pipette to blow and suck 50 times to fully disperse the mold spores.
6.3 Take 1mL of the 1:10 dilution solution and inject it into a test tube containing 9mL of sterile water. Use another 1mL sterile pipette to blow and suck five times. This solution is the 1:100 dilution solution.
6.4 Make 10-fold incremental dilutions according to the above operation sequence. After each dilution, use a 1mL sterile pipette. According to the estimation of sample contamination, select three appropriate dilutions. While making 10-fold dilutions, draw 1mL of dilution into sterile plate III. Make two plate bloods for each dilution. Then inject the culture medium that has been dried to about 45℃ into the plate bloods, and rotate the plate bloods to mix with the sample liquid. After the agar solidifies, invert it in a 25℃～28℃ incubator. Start observation after 3 days, and observe for 5 days. 6.5 Calculation method: Usually, plate bloods with colony counts between 10 and 150 are selected for counting. The average number of colonies of two plates with the same dilution multiplied by the dilution multiple is the number of molds and alcohols contained in each gram (or milliliter) of the test sample. For dilution selection and colony report method, please refer to GB/T4789.2.
6.6 Report: The number of fungi and yeasts contained in each gram (or milliliter) of food is expressed as cfu/g (mlL). 7
Direct microscopic counting method for mold
For the direct microscopic counting method for mold, see Appendix A.
Appendix A
(Informative Appendix)
Direct microscopic counting method for mold
The commonly used method is the Hodgkin's fungus counting method, which is applicable to canned tomato sauce. A.1 Equipment and materials
A.1.1 Refractometer.
A.1.2 Microscope.
A, 1.3 Hodgkin's counting slide: a special slide with a standard counting chamber. A.1.4 Cover glass.
A, 1.5 Micrometer: a slide with a standard scale. A.2 Operation steps
GB/T4789.15—2003
A.2.1 Preparation of test sample: Take a quantitative test sample, dilute it with distilled water to a refractive index of 1.3447~1.3460 (i.e. a concentration of 7.9%~8.8%), and set it aside.
A,2.2 Calibration of standard field of view of microscope: Adjust the standard field of view of the microscope to 90 times~125 times of magnification, so that its diameter is 1.382mm.
A.2.3 Smear: Wash the Hao's measuring glass slide, and evenly spread the prepared standard solution in the measuring room with a glass rod for observation. A.2.4 Observation: Place the prepared slide under the standard field of view of the microscope for mold observation. Generally, 50 fields of view are observed for each test sample, and the same test sample should be observed by two people.
A.2.5 Results and calculation: Under the standard visual field, if the length of the hyphae of the fungus exceeds one sixth of the standard visual field (1.382mm) or the total length of three hyphae exceeds one sixth of the standard visual field (i.e. one grid of the micrometer), it is positive (10), otherwise it is negative (1). The number of visual fields in which the fungal hyphae is found out of 100 visual fields is the percentage of the visual field with fungi.
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