GB Translated English of Chinese Standard: GB NATIONAL STANDARD

Transcription

1 Translated English of Chinese Standard: GB GB NATIONAL STANDARD OF THE PEOPLE S REPUBLIC OF CHINA GB Food safety national standard Microbiological examination of food hygiene-detection of aerobic bacterial count 食品安全国家标准食品微生物学检验菌落总数测定 Issued on: December 23, 2016 Implemented on: June 23, 2017 Issued by: National Health and Family Planning Commission of People s Republic of China; State Food and Drug Administration. Page 1 of 12

2 Table of contents Foreword Scope Terms and definitions Equipment and materials Culture medium and reagents Test procedures Operating procedures Results and reports... 8 Appendix A Culture medium and reagents Page 2 of 12

3 Foreword This standard replaces GB Food safety national standard - Microbiological examination of food hygiene-detection of aerobic bacterial count. Page 3 of 12

4 Food safety national standard Microbiological examination of food hygiene-detection of aerobic bacterial count 1 Scope This standard specifies the method of determination of the aerobic plate count in food. This standard applies to the determination of the aerobic plate count in food. 2 Terms and definitions Aerobic plate count It refers to the total number of microbial colonies formed per gram (ml) of the sample after treatment and cultivation under certain conditions (such as culture medium, culture temperature and incubation time). 3 Equipment and materials In addition to conventional microbiological laboratory sterilization and culture equipment, other equipment and materials are as follows: 3.1 Constant temperature incubator: 36 C ± 1 C, 3 0 C ± 1 C. 3.2 Refrigerator: 2 C ~ 5 C. 3.3 Constant temperature water bath: 4 6 C ± 1 C. 3.4 Balance: the sensitivity is 0.1 g. 3.5 Homogenizer. 3.6 Oscillator. 3.7 Sterile pipettes: 1mL (with 0.1 ml scale), 10 ml (with 0.1 ml scale) OR micro pipettes and tips. Page 4 of 12

5 6.3.1 It may conduct observation through naked eyes; if necessary, USE a magnifying glass or colony counter; RECORD the dilution and the corresponding colony count. The colony count is expressed by the colonyforming units (CFU) SELECT the aerobic plate count for which the colony count is 30 CFU ~ 300 CFU without the growth of dispersed colonies. RECORD the actual colony count of the plate lower than 30 CFU; and RECORD those more than 300 CFU as too much to be counted. The colony count of each dilution shall adopt the average value of the two plates If one plate has larger platelet growth of colonies, it shall not be used; BUT it shall use the plate without platelet growth of colonies as the colony count of this dilution; if the platelet colony does not reach to half of the plate area AND the colony distribution in another half is uniform, it may calculate the value of the half plate AND multiple by 2 to represent the colony count of a whole plate When there is streaky growth between colonies with no apparent boundaries on the plate, MAKE each single strand as a colony for counting. 7 Results and reports 7.1 Calculation methods of aerobic plate count If there is only one plate on which the colony number is within the appropriate counting range, CALCULATE the average value of the two aerobic plate count, then MULTIPLE the average value by the corresponding dilution factor, to obtain the aerobic plate count per gram (ml) of sample If there are two plate colony number of serial dilution fall into the appropriate count range, it shall use the equation (1) to conduct calculation: Where: N - Number of colony in the sample; ΣC - Sum of plate colony number (including the plate with appropriate range of colony number); n1 - First dilution (low dilution factor) plate number; Page 8 of 12

6 Sodium chloride: 8.5 g Distilled water: 1000 ml A.3.2 Preparation methods WEIGH 8.5 g of sodium chloride and DISSOLVE it in 1000 ml of distilled water; MAKE it subjected to 121 C autoclaving for 15 min. END Page 12 of 12