SN/T 4546-2017 in English

This standard replaces SN/T 1895-2007. Major technical changes include: revision of the standard title, addition of calculation formulas and Appendix B, and deletion of Method 2. Testing is performed using the Petrifilm™ Staphylococcus aureus Test Plate and is applicable to the microbiological safety control of food raw materials and finished products.

Validation in 15 types of food matrices shows:

• Linear equation slope 0.9767-1.1332, R²≥0.9696
• T test values compared with GB 4789.10 reference method are both <2.131 (P＞0.05)
• Inter-batch variation RSD≤3.12%, showing good repeatability

1. Sample processing: Homogenization time should be controlled within 1-2 minutes, and pH should be adjusted to 6.5-7.5
2. Inoculation technique: Use a pressure plate to ensure even coverage of the sample solution, and let it stand for 1 minute to allow the gel to solidify
3. Quality control: Each batch should include a blank control and a positive control (ATCC 25923)
4. Data recording: Pay attention to the distinction between direct counting and confirmation counting results

Compared with the 2007 version of the standard, this version has the following major improvements:

• Introduction of Confirmation reaction plate to improve specificity (detection of DNase activity)
• Addition of calculation formula to standardize the processing of multiple dilution results
• Delete the Petrifilm™ MPN method and focus on the plate count method