Milk and milk products — Quality control in microbiological laboratories — Part 2: Determination of the reliability of colony counts of parallel plates and subsequent dilution steps
牛奶和奶制品——微生物实验室的质量控制第2部分:平行平板菌落计数和后续稀释步骤的可靠性测定
发布日期:
2005-04-12
ISO 14461-2 | IDF 169-2:2005描述了使用菌落计数法对微生物计数结果进行评估的常规程序,该方法包括随后的10倍稀释步骤和每个稀释步骤中的一个平板或两个平行平板。
该常规程序定期应用于每个进行菌落计数的实验室。它提供了平行板和后续稀释步骤结果之间差异的可接受性标准,如下所示。
将从平行平板获得的结果(菌落计数)与给定菌落计数的列表极限进行比较。如果超过这些限值,则在进行平行测定时可能会出现技术问题。
两个平行平板的结果(菌落计数之和)以及随后的两个10-
将倍稀释步骤与给定菌落总数的列表极限进行比较。如果超过这些限值,可能表明稀释时存在技术问题。
如果超过上述限值的情况超过预期,则表明试验程序缺乏可靠性。
ISO 14461-2|IDF 169-2:2005 describes a routine procedure for the evaluation of results of the enumeration of microorganisms using colony-count methods with subsequent 10-fold dilution steps and one plate or two parallel plates within each dilution step.
This routine procedure is applied regularly in each laboratory performing colony counts. It provides criteria for the acceptability of differences between the results from parallel plates and subsequent dilution steps, as follows.
The results (colony counts) obtained from parallel plates are compared with tabulated limits for given colony counts. If these limits are exceeded, a technical problem when performing the parallel determinations may be indicated.
The results (sums of colony counts) of two parallel plates of two subsequent 10-fold dilution steps are compared with tabulated limits for given sums of colony counts. If these limits are exceeded, a technical problem when performing the dilutions may be indicated.
If the limits mentioned above are exceeded in more cases than expected, this indicates that the test procedure lacks reliability.