How to measure probiotic counts in chocolate

By Annie Harrison-Dunn contact

- Last updated on GMT

37% of viable probiotic cells are lost when added to chocolate at 40°C, according to a more precise laser detection method
37% of viable probiotic cells are lost when added to chocolate at 40°C, according to a more precise laser detection method

Related tags: Probiotic, Bacteria

Flow cytometry – a laser-based cell sensor system – is almost twice as accurate at measuring probiotic levels in chocolate when compared to traditional methods, according to research.

The study, published in the journal Food Microbiology​found that flow cytometry (FC) was more precise than direct microscopic counts (DCM) or colony forming units (CFU) – used by regulatory organizations – in evaluating the populations of probiotic bacteria Lactobacillus rhamnosus​ in chocolate.

Researchers from the Food Research and Development Centre in Canada found that compared to the other two methodologies, FC – which has also been used for counts of pathogenic bacteria in foods – was able to determine low levels of dead cells in fresh cultures.

These tests revealed that adding probiotics to 40°C chocolate resulted in a 37% loss of “viable cells”​.

Vetting functional confectionery


The research used two dried forms of Lactobacillus rhamnosus​ manufactured by Lallemand Health Solutions. The first was a standard free-cell powder while the second was a micro-encapsulated product using spray-coating technology.

They said the research, which also looked at cereal bars, demonstrated FC could be used to assess probiotic levels in a variety of food products.

The results built on previous literature that suggested simultaneous analysis of ‘total’ and ‘viable’ cell populations by FC could improve the interpretation of counts of probiotic cultures in foods.

Countlines and spreads

However, the tests were not without challenges. The researchers found that blending probiotic powder into chocolate was not uniform, meaning the precision of viable counts could be compromised.

“Data from this study show that blending powders of probiotic bacteria in chocolate is not easy and results in variable inoculation rates,”​ they wrote. 

Healthy ingredient = healthy product?​ 

The researchers conceded that some nutritionists may question the “ethics”​ of using a high-calorie, high-fat matrix such as chocolate as a delivery medium for health-promoting ingredients like probiotics.

“In some instances, such as in areas in the world where famine and infant diarrhea are significant health problems, probiotic-carrying high-calorie foods are very desirable.... But this would not be the case in North-America and Europe,”​ they said.  

They said it was for this reason they sought to develop a chocolate product with a bacterial density well above one billion per gram, meaning one gram would be enough to deliver the one billion cell per portion dose they said was favored by the food industry.


Source: Food Microbiology

Published online ahead of print, doi: 10.1016/

The use of flow cytometry to accurately ascertain total and viable counts of Lactobacillusrhamnosus​ in chocolate”

Authors: Y. Raymond and C. P. Champagne 

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