Testing of plant-based alternatives to meat and dairy products in England has shown that the majority of them are safe from a microbial perspective.
A study assessed the microbiological safety and quality of vegan alternatives to dairy and meat products available in England. Researchers said that despite public perception of relatively low microbiological risk, outbreaks have been linked to these foods.
Vegan alternatives to animal milk are usually produced by soaking nuts, grains or legumes in water. Meat alternatives are formulated with similar protein, fat and moisture contents to meat and neutral pH levels, which provide suitable growing conditions for pathogenic and spoilage organisms.
Between September 2022 and March 2023, samples of meat, fish or dairy alternatives were collected from stores, manufacturing and catering establishments, and tested for a range of bacterial pathogens and hygiene indicators. The findings were published in the Journal of Applied Microbiology.
Listeria findings
A total of 937 samples were tested, of which 92 percent were of satisfactory microbiological quality, 3 percent were borderline and 5 percent were unsatisfactory. The cases assessed as unsatisfactory were due to increased numbers of Enterobacteriaceae and E. coli, which are indicators of poor hygiene, rather than pathogenic microorganisms. The majority of samples were prepacked in an unopened package at the time of sampling.
Listeria monocytogenes was present in five samples of tofu, all from the same producer, at levels less than 100 colony-forming units per gram (CFU/g). One sample of organic natural tofu collected from a retailer in January 2023 was positive for Listeria monocytogenes, prompting three follow-up samples directly from the producer.
In early February 2023, five follow-up samples of organic natural tofu were taken from the producer, in which Listeria monocytogenes was detected in three cases; At the end of February, five samples of different tofu products (natural, smoked, marinated tofu and tofu burgers) were taken and all were negative; and in March 2023, five further samples of different product types were taken, of which Listeria monocytogenes was found in one sample of marinated tofu.
A look at the UK Health Security Agency (UKHSA) database identified no isolates from human cases that were closely related to these food isolates. Tofu is generally subjected to further cooking before consumption, so it is not normally considered ready-made, but there are recipes that use uncooked or lightly cooked tofu as ingredients.
Two hamburger samples contained Listeria welshmeri and Listeria innocua, respectively, while two vegan chicken products both contained Listeria seeligeri.
Water activity and pH
The production of plant-based dairy alternatives often involves a heat treatment step, which is expected to reduce the number of bacteria in the final product. However, spore-forming bacteria such as Bacillus and Clostridium species are more likely to survive the heat process. Control of Bacillus growth in such products may include maintaining low pH and/or water activity, low storage temperature and possibly modified atmosphere.
Salmonella was not detected in any tests, while Bacillus cereus was found at borderline levels in two samples. These were a Camembert style cheese and a soft cheese product with garlic and herbs.
For one of these products, neither the pH nor the water activity was sufficiently low to control Bacillus growth. Scientists said that storage at an appropriate refrigeration temperature and maintenance of an appropriate shelf life would be important to ensure the continued microbiological safety of this product.
The majority of samples did not have pH and water activity values that would contribute significantly to preventing microbial growth. Only 37 percent of the 772 samples had a pH lower than 5 and 18 percent of the 500 samples had a water activity of less than 0.94.
“While this study provides reassuring evidence that plant-based alternatives to meat and dairy products consumed in England generally pose a low microbiological risk, it is important that producers and retailers remain aware of the relevant risks and maintain reliable controls,” according to scientists.
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