Blue mozzarella bacteria not harmful to humans, said Germany

The German Federal Institute for Risk Assessment (BfR) said the risk from the family of Pseudomonad bacteria that spoiled up to 70,000 mozzarella cheese balls was low - although it did render the food unfit for consumption.

The assessment followed a series of complaints from consumers in Italy in June that mozzarella cheese imported from Germany developed a blue tint after opening. Italian authorities said the discolouration was caused by the bacteria Pseudomonas (P.) tolaasii and P. libanensis, of which high microbial counts were detected in the cheese. The country’s Ministry of Health believed that the presence of the bacteria resulted from contaminated water which was used as brine for the cheese.

Ubiquitous​

Pseudomonads are bacteria that have a ubiquitous presence and can multiply even at low temperatures. The Committee for Biological Agents (ABAS) has classified the bacteria in the lowest risk category, said the BfR.The body added it was “neither aware of information concerning food-borne diseases caused by these bacteria nor are studies available concerning the transmission of microorganisms to humans.”​

According to studies carried out by Italian scientists into the presence of pseudomonads in mozzarella and tests by German researchers into the microbial nature of mozzarella carried out in 2006, only few samples exhibited an unsafe amount of spoilage bacteria, said th agency.

The BfR recommended that mozzarella cheese be stored in the refrigerator at less than +7° C. Great care should be taken by manufacturers over determining the best before date and in ensuring hygienic processing conditions are maintained - including milking, production, storage and transport in order to reduce the entry of these bacteria as much as possible.

Following the blue mozzarella alert, the European Commission ordered Milchwerk Jäger, the German company at the centre of the problem, to stop production at its plant until it received assurance from the competent authorities that its food safety measures were complaint with regulations. The firm was given the all-clear to start manufacturing cheeses again in mid July.