Lactobacillus and bifidobacterium, present in yogurt and other dairy products, are well-known medical foods used as probiotics, or "friendly bacteria", to maintain a healthy digestive tract. Flow cytometry, a cell-counting method for assessing the quality of cultures by determining the proportion of active cells, has met with a degree of skepticism. Now, a new ISO standard rubber-stamps the validity of this method, speeding up quality control and facilitating trade.
A recently published International Standard, ISO 19344 (IDF 232), provides a method for the quantification of lactic acid bacteria by flow cytometry in fermented products, starter cultures and probiotics used in dairy products. This publication is the result of the joint work of ISO and the International Dairy Federation (IDF).
Quantification of lactic acid bacteria (LAB) is important in assessing the quality of starter cultures, probiotics and fermented milk products. Examination of LAB in these products can be carried out following different methods, with plate count techniques being the most traditional and widely used. Newer techniques include flow cytometry, which is able to determine the proportion of active cells and/or total units.