Abstract: [Objective] To enhance the laboratory testing capability and level,optimize the experimental data processing procedure,strengthen the laboratory quality control system,and improve the credibility of experimental results,this study systematically verified the detection capability of lactic acid bacteria count.[Method] According to the“ACAS-PT1911（2024）Proficiency Testing Guide for Lactic Acid Bacteria in Milk Powder”and“GB 4789.35-2023 National Food Safety Standard - Microbiological testing of food - Lactic Acid Bacteria Testing”,the proficiency testing samples with numbers 24-S614 and 24-F143 were tested, and the uncertainty was evaluated.[Result] The detection result of sample 24-S614 was 7.0×10⁶,with a Z value of -1.0. The detection result of sample 24-F143 was 1.1×10⁷,with a Z value of 1.2. The │Z│of both test proficiency testing samples was≤2.0,which was a satisfactory result..Critical control point analysis and uncertainty assessment indicated that dilution error,weighing error,temperature fluctuation,and repeated detection were the main contributing sources. The expanded uncertainty of the lactic acid bacteria count results was 2.2×10^-4（P=95%,k=2）.[Conclusion] The results of the proficiency testing indicate that the laboratory's ability to detect lactic acid bacteria has been effectively enhanced,increasing the reliability of the laboratory's detection results. This confirmed that such matrix proficiency testing samples had good stability and reliability,providing a reference for the standardization of lactic acid bacteria detection methods in milk powder.

Key words: lactic acid bacteria, detection proficiency verification, quality control