Standard No.:	GB 4789.38-2025
English Name:	National food safety standard - Food microbiological examination - Counting of Escherichia Coli
Chinese Name:	食品安全国家标准 食品微生物学检验?大肠埃希氏菌计数
Chinese Classification:	X09    Hygiene, safety and labor protection
Professional Classification:	GB    National Standard
Source Content Issued by:	National Health Commission of the People's Republic of China, State Administration for Market Regulation
Issued on:	2025-03-16
Implemented on:	2025-9-16
Status:	valid
Superseding:	GB 4789.38-2012 National Food Safety Standard - Food Microbiological Examination - Counting of Escherichia Coli
Target Language:	English
File Format:	PDF
Word Count:	5500 words
Translation Price(USD):	165.0
Delivery:	via email in 1 business day

GB 4789.38-2025 National food safety standard - Food microbiological examination - Enumeration of Escherichia coli 1 Scope This standard specifies the method for the enumeration of Escherichia coli in food. Method I in this standard is applicable to the enumeration of Escherichia coli in foods with low Escherichia coli content, while Method II is applicable to the enumeration of Escherichia coli in foods with high Escherichia coli content, but is not applicable to the enumeration of Escherichia coli in shellfish and their products. 2 Examination principle Escherichia coli ferments lactose to produce acid and gas at 44.5℃. It possesses β-glucuronidase activity, which can decompose 5-bromo-4-chloro-3-indolyl-β-D-glucuronide, forming blue-green colonies on Tryptone Bile X-glucuronide (TBX) agar. Based on these characteristics of Escherichia coli, the most probable number (MPN) technique and plate count method are used for its enumeration. Note: The majority of Escherichia coli strains possess β-glucuronidase activity, but strains such as Escherichia coli O157 do not. Additionally, some strains of Shigella, Salmonella, and other genera within the Enterobacteriaceae family also possess β-glucuronidase activity. 3 Equipment and materials In addition to conventional sterilization and incubation equipment used in microbiological laboratories, other equipment and materials required are as follows. 3.1 Constant temperature incubator: 36℃±1℃. 3.2 Refrigerator: 2℃~8℃. 3.3 Constant temperature water bath: 44.5℃±0.2℃. 3.4 Thermostat: 48℃±2℃. 3.5 Balance: With a sensitivity of 0.1g. 3.6 Homogenizer, aseptic homogenizing bag, homogenizing cup, and oscillator. 3.7 Test tubes: With sizes of 15mm×150mm, 18mm×180mm, or other appropriate sizes; and inverted tubes (Durham tubes) or other suitable gas collection devices. 3.8 Aseptic pipettes: 1mL (graduated to 0.01mL), 2mL (graduated to 0.02mL), 5mL (graduated to 0.05mL), 10mL (graduated to 0.1mL), or micropipettors with aseptic tips. 3.9 Aseptic conical flask: With a capacity of 500mL. 3.10 Aseptic culture dish: With a diameter of 90mm. 3.11 pH meter or precision pH test paper. 3.12 Aseptic inoculation loop: 10μL (with a diameter of about 3mm). 4 Culture media and reagents 4.1 Phosphate buffer solution: See Annex A, A.1. 4.2 Normal saline: See A.2. 4.3 Lauryl sulfate tryptose (LST) broth: See A.3. 4.4 EC broth: See A.4. 4.5 Tryptone Bile X-glucuronide (TBX) agar: see A.5. 4.6 1mol/L NaOH: See A.6. 4.7 1mol/L HCl: See A.7. Method I Enumeration of Escherichia coli by MPN technique 5 Examination procedures The examination procedures for the enumeration of Escherichia coli by the MPN technique is shown in Figure 1.

Foreword I 1 Scope 2 Examination principle 3 Equipment and materials 4 Culture media and reagents 5 Examination procedures 6 Operation steps 7 Results and report 8 Examination procedures 9 Operation steps 10 Results and report Annex A Culture media and reagents Annex B Retrieval table for the most probable number (MPN) of Escherichia coli in food Annex C Retrieval table for the most probable number (MPN) of Escherichia coli in shellfish and shellfish products