Researchers in Germany have provided an initial evaluation into the microbial quality of plant-based “meat.”

The microbiological status of 10 raw plant-based ground meat products was assessed. Items produced by different companies made from soy, pea, oats, or wheat were obtained in 2021 from Kiel, northern Germany stores.

Total bacterial counts at the end of the best-before dates varied. No Listeria monocytogenes colonies were obtained, but other Listeria species were detected and found in the Journal of Consumer Protection and Food Safety study.

The increased consumption of plant-based products is an ongoing consumer trend. Plant-based meat analogs generally have lower microbial loads than their meat equivalents, but they are not sterile products, so refrigerated storage is essential to limit microbial growth.

Meat analogs are produced from plant-based protein raw materials, amongst which products made from soy, wheat, or pea currently dominate. Plant-based meat analogs are high in protein and water activity with weakly acidic pH, so they are at risk of microbial spoilage by various microorganisms, depending on storage conditions.

Production of meat alternatives includes raw materials, food additives, and/or processing aids, as well as processes such as extrusion, which involves a heating step.

The study detected low levels of enterobacteria, enterococci, presumptive Bacillus cereus, Listeria spp., and Staphylococcus aureus.

Survival and recontamination issues

Spore-forming bacteria, such as Bacillus cereus or Clostridium perfringens, from the raw materials may survive heating during the extrusion process and germinate in the extruded product.

Most of the bacteria that comprised the total aerobic plate count in the frozen product were presumably Bacillus cereus.

“Assuming that the product was immediately frozen after production and a heating step was employed during production, this may imply that spores of these bacteria possibly survived the heating step,” said scientists.

Scientists said the detected Listeria and presumptive Staphylococcus aureus probably stemmed from recontamination and highlighted the need for adequate processing hygiene.

Vegan ground meat analogs are not intended to be eaten raw. However, it is not easy for consumers to judge whether they have been sufficiently heated, as unlike meat, the color of products does not change.

Results showed contamination of vegan ground meat products by pathogenic bacteria can be a potential safety concern.

“The detection of presumptive Bacillus cereus and the isolation of various Clostridium species from these products indicates that spore-formers may have survived the food processing and, therefore, could pose a safety concern, which should be assessed in further studies,” according to the report.