For more than 20 years most laboratories have been analyzing the Total Bacterial Count (TBC) in Individual Bacteria Count (IBC) and then converting this result into Colony Forming Units (CFU). Everybody within the raw milk business know that this conversion at best is a rough estimate, and everybody know that it is done differently in different countries, – and sometimes also between regions within the same country. Everybody knows that the routine methods used today in all ways gives a better result than the plate count method does! But we still convert results into CFU’s!

At the same time it gets more and more necessary that milk quality can be analyzed across borders and give comparable results. Dairies become multinational and have owners in many countries, raw milk is traded across borders, and focus on high quality of the raw milk increases.

Therefore I believe it is time to consider how bacteria in raw milk can be enumerated uniformly, – wherever the analyses takes place, – and that results can be compared, no matter where they have been analyzed! Normally this is what a reference method is needed for! But when there is no reference method able to give comparable results between labs, and when it is almost impossible to carry out collaborative studies or ring trials between labs on the reference method with a reasonable result we may have to look for other ways This was done years ago for somatic cell counting! The reference method has hardly been used for decades; instead control samples and ring trials are used to verify correct performance within labs, between labs and between countries. At present a group within IDF/ISO is working hard to improve and standardize these procedures, – but without trying to reintroduce the reference method, – microscopic cell counting, accepting that it will not improve performance.

Conversion, example

Fig 1. Example of conversion in log units

The present situation for bacteria counting, I believe, is even worse than it has ever been for cell counting! In some regions, where there has been a public or legal need for uniform conversion it has been possible to construct a uniform conversion table for a larger area i.e. Germany or the US. In other regions it has been decided to have different conversion tables for each lab, or for each region. The microbiologic arguments can be found for both solutions, – but how do we argue for one conversion table for all US or for all Germany AND for one conversion table for each of the countries Denmark, the Netherlands, Belgium, Luxemburg and each of the departments in France?

In countries like Canada, the UK and Norway years back they have chosen to stop converting.They are using the unit counted by the instrument they have in the lab, – as they do when counting the somatic cells, and they have found alternatives procedures for ensuring uniform performance!

Could the same happen in more countries? At the same time saving resources and allowing the farmers to get a more precise and useful result for management of milk quality?

Read more about what is up and down on bacteria counting in the first of some highly relevant articles just uploaded on the Raw Milk Connect Portal by clicking HERE. And please let us have your comments and proposals for better solutions here on this blog!

Blog post written by:


Tove Asmussen

Master of Sci. Milk Production
Dipl. Business Innovation
Consultant & Business Owner, Raw Milk Connect