Sampling of vegan alternatives reveals good microbial compliance

Testing of plant-based alternatives to meat and dairy products in England has found the majority of them are safe from a microbial point of view.

A study assessed the microbiological safety and quality of vegan alternatives to dairy and meat products available in England. Researchers said that despite a public perception of relatively low microbiological risk, outbreaks have been linked with these foods.

Vegan alternatives to milk of animal origin are commonly produced by soaking nuts, grains, or pulses in water. Meat alternatives are formulated with a similar protein, fat, and moisture content to meat, and neutral pH levels, which provide suitable growth conditions for pathogenic and spoilage organisms.

Samples of meat, fish, or dairy alternatives were collected between September 2022 and March 2023 from retail, production, and catering premises, and tested for a range of bacterial pathogens and hygiene indicators. Findings were published in the Journal of Applied Microbiology.

Listeria findings

A total of 937 samples were tested, of which 92 percent were of a satisfactory microbiological quality, 3 percent were borderline, and 5 percent were unsatisfactory. Those judged to be unsatisfactory were due to elevated counts of Enterobacteriaceae and E. coli, which are indicators of poor hygiene, rather than pathogenic microorganisms. The majority of samples were pre-packed in unopened packaging at the time of sampling.

Listeria monocytogenes was present in five samples of tofu, all from the same producer, at counts of below 100 colony forming units per gram (CFU/g). One organic natural tofu sample, collected from a retailer in January 2023, was positive for Listeria monocytogenes, which led to follow-up sampling directly from the producer on three occasions.

Five follow-up samples of organic natural tofu were taken from the producer in early February 2023, with Listeria monocytogenes detected in three; five samples of various tofu products (natural, smoked, marinated tofu, and tofu burgers) were taken in late February and all were negative; and five more samples of different product types were taken in March 2023, of which Listeria monocytogenes was detected in one marinated tofu sample.

A look at the UK Health Security Agency (UKHSA) database did not identify any isolates from human cases that were closely related to these food isolates. Tofu is generally subjected to further cooking prior to consumption, so would not normally be considered ready to eat, but there are recipes that use uncooked or lightly cooked tofu as ingredients. 

Two burger samples contained Listeria welshmeri and Listeria innocua, respectively, while two vegan chicken products both contained Listeria seeligeri.

Water activity and pH

Production of plant-based dairy alternatives often involves a heat-treatment step, which would be expected to reduce bacterial numbers 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 a low pH and/or water activity, low storage temperature, and potentially 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 garlic and herb soft cheese product.

For one of these products, neither the pH nor the water activity was sufficiently low to control Bacillus growth. Scientists said storage at an appropriate refrigeration temperature and maintenance of an appropriate length of 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 significantly contribute to preventing microbial growth. Only 37 percent of 772 samples had a pH below 5 and 18 percent of 500 samples had a water activity of under 0.94.

“While this study provides reassuring evidence that plant-based alternatives to meat and dairy products consumed in England are generally of low microbiological risk, it is important that producers and retailers maintain an awareness of relevant risks and reliable controls,” said scientists.

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Source: https://www.foodsafetynews.com/2024/10/sampling-of-vegan-alternatives-reveals-good-microbial-compliance/