ISO 19344:2015规定了通过流式细胞术定量乳制品中使用的发酵剂培养物中的活性和/或总乳酸菌和益生菌菌株的标准化方法。该方法还适用于乳制品中使用的益生菌和发酵乳制品，例如主要含有乳酸菌的酸奶。 本国际标准不适用于细菌的分类区分。由于其非特异性，当样品中存在时，该方法可以定量本国际标准范围内的其他细菌。这可能导致对计数的高估。 在应用该标准化方法之前，样品中的最小细菌细胞浓度取决于各个方案中使用的稀释率。通常，106个细胞/克或毫升被认为在最小范围内。

ISO 19344:2015 specifies a standardized method for the quantification of active and/or total lactic acid bacteria and probiotic strains in starter cultures used in dairy products by means of flow cytometry. The method is also applicable to probiotics used in dairy products and to fermented milk products such as yogurts containing primarily lactic acid bacteria. This International Standard does not apply to taxonomical differentiation of bacteria. Due to its non-specificity, the method may quantify other bacteria than those within the scope of this International Standard, when present in the sample. This may lead to overestimation of the counts. The minimum bacterial cell concentration in the sample before applying this standardized method depends on the dilution rates used in the individual protocols. Typically 10⁶ cells per gram or ml are considered within the minimum range.