"If we look at market forecasts, we know that in Europe, vegans, vegetarians and those reducing meat consumption — so-called flexitarians — already make up 13 to 42 percent of the population, depending on the country," said Estonian University of Life Sciences food safety professor Mati Roasto. Consequently, there has been rapid growth in the share of plant-based foods, including alternative products, in Estonia as well. While global sales of these products were about $30 billion in 2020, by 2030 they could rise to $162 billion for a 5.5-fold increase.

More specifically, forecasts suggest that the market value of plant-based meat alternatives could grow from $12.5 billion last year to $21 billion by 2027 — nearly doubling. Sales of plant-based dairy alternatives are expected to grow even more strongly. If global sales reached $27 billion in 2022, they could also nearly double within five years, reaching $45 billion.

"These market projections raise the question of whether, as production increases so significantly, we have sufficient information about the quality and safety of these products. The answer is that, in fact, we do not yet have enough," Roasto said. Together with colleagues at the Estonian University of Life Sciences, he is currently involved in a TemTA research project aimed at assessing the safety and quality of high-risk plant-based foods and plant-based alternatives to animal products.

As part of the project, researchers are collecting hundreds of samples of alternative products from Estonian retail outlets and conducting thousands of microbiological and chemical analyses. Both domestic and imported products are being examined. Most of the samples analyzed so far consist of meat alternatives, but plant-based dairy and fish alternatives are also under study. "We have now largely completed the microbiological analyses. In total, thousands of tests have been carried out and the results are generally good," he noted.

Unexpected microbes

According to Mati Roasto, the study is unique not only in Estonia but globally in terms of the volume and diversity of its analyses. The European Food Safety Authority has also recommended conducting such studies across different member states.

In their research, Roasto and his colleagues, in cooperation with the Center of Food and Fermentation Technologies (LABRIS), used a method known as MALDI-TOF MS. As a key concern, they identified spore-forming bacteria such as representatives of the Bacillus and Clostridium genera, which include pathogenic species. Roasto added that some imported products have also contained Listeria bacteria and salmonella.

The researchers also detected a surprisingly large number of bacterial species in alternative product samples that have not previously been regarded as food safety hazards. However, these are conditionally pathogenic species, meaning they may cause illness in humans under certain circumstances. "These are very interesting findings, the interpretation of which is not straightforward, but they may change our current understanding of the food safety of alternative products," the professor said.

The research team also identified a significant presence of nosocomial bacteria — species typically associated with hospital or healthcare settings. "One example is Enterococcus faecium, which is concerning due to its resistance to vancomycin," Roasto noted. Resistance to vancomycin is a serious issue, as this drug is often the last effective antibiotic for treating severe bacterial infections in humans.

Another example, according to the professor, is Ochrobactrum intermedium, which is often resistant to multiple antibiotics. It can infect individuals with weakened immune systems, causing bacteremia. In addition, the researchers identified dozens of different potentially pathogenic bacterial species in alternative products.

"The species we were able to identify at the genus or species level are somewhat alarming, as they have not previously been considered hazards in food microbiology. Yet we are now detecting them relatively frequently in alternative products," Roasto said. Going forward, he and his colleagues will need to assess whether these may constitute real food safety risks.

"In any case, it is important that, as a result of thousands of analyses, we are developing a reliable dataset that can be used to compile guidelines for companies," the professor added. For example, this will make it possible to provide companies with recommendations on which microbiological and chemical indicators should be tested in plant-based foods, including alternative products, in order to assess their safety and quality. "This is also very important for conducting shelf-life studies, meaning determining the durability of products," Roasto said.

Shelf life too long

Alongside microbiological testing, the research team is also assessing the chemical safety of plant-based alternative products sold in Estonia. At the Estonian University of Life Sciences' food hygiene and safety unit, studies on toxic oxidation products have long been conducted under the leadership of Professor Tõnu Püssa.

The new study has found that a relatively common concern in alternative products is excessively high levels of malondialdehyde (MDA). These products contain large amounts of polyunsaturated fatty acids, which oxidize — or turn rancid — relatively quickly. "To some extent, this happens in all products and foods and one common result is MDA. We know it is a potential carcinogen," Mati Roasto explained, referring to data from Professor Püssa.

According to recommendations from the European Food Safety Authority, MDA content in products should remain below 0.5 milligrams per kilogram. In 58 percent of the samples analyzed so far by the research group, this value was higher and in some products it was up to eight times greater. "This is a cause for concern. Even if these products do not spoil significantly from a microbiological standpoint, their shelf life is clearly too long when considering chemical hazards," Roasto said. The research team concludes that the shelf life of alternative products should be reduced based specifically on MDA levels.

Roasto added that analyses of mycotoxins have also begun and while they have been detected in some products, the levels have fortunately been relatively low. "We do not want to alarm consumers, but we do need to consider what other chemical hazards may be present in different alternative products," he said.

Nitrate content in plant-based foods also warrants evaluation. Nitrate levels in plant materials, such as beetroot, lettuce, spinach and celery, can be relatively high, ranging from 500 to 4,000 milligrams per kilogram. The acceptable daily intake of nitrates is 3.7 milligrams per kilogram of body weight. According to Roasto, the average nitrate content in the analyzed alternative products was 700 milligrams per kilogram. "This means consumers should pay attention to the composition of alternative products and avoid overconsuming those containing nitrate-rich ingredients," he said, adding that moderation and dietary diversity are always important.

"Official criteria for nitrate levels have only been established for infant foods and for meat and cheese products where the limit is set at 150 milligrams per kilogram," he noted. However, no such limits have been set in legislation for alternative products. Nitrates can be problematic because microbes in the digestive tract can convert them into nitrites, which can then be transformed into nitrosamines — compounds known to be carcinogenic, Roasto explained.

Many alternative products also require heating before consumption. "We must take into account that, as in many starch-rich foods, many alternative products likely contain precursor compounds for the formation of acrylamide," the professor warned.

Acrylamide is a potentially carcinogenic substance and excessively high levels are indicated when food becomes overly browned or burnt during heating. For example, it is found in higher amounts in darker-roasted coffee, overly browned toast or fried potatoes. "It is generally recommended that dietary exposure to acrylamide be kept as low as reasonably possible," Roasto said.

Consumers should also be aware that many plant-based alternatives are ultra-processed foods. They often contain added food additives and are produced under high temperatures and pressures. "For this reason, the general recommendation from nutrition scientists applies here as well: maintain a varied diet and avoid consuming excessively large quantities of any single type of food at once. If you prefer alternative products and plant-based foods, you should consume a variety of foods in moderation to avoid excessive intake of potentially harmful compounds," Roasto advised.

Consume sooner rather than later and do not overheat

In light of the study, Mati Roasto recommends that consumers eat food as fresh as possible. It is always worth checking the expiration date on packaged foods. "Do not leave it sitting in the refrigerator, even if you see that there are still several months until the expiration date because the quality of food will certainly decline over long storage periods. In some cases, it may even become dangerous," the professor said.

Temperature also deserves attention both during preparation and storage. Products should not be heated more than recommended by the manufacturer on the packaging, Roasto added. For proper storage, he advises setting the refrigerator temperature to between +2 and +4 degrees Celsius. "If you lower the temperature from six degrees to four, you are doing yourself and your health a big favor," he explained.

For food producers, the study provides, for the first time, a strong scientific basis for determining which microbiological and chemical indicators should be considered when assessing the safety and quality of alternative products.

"Until now, companies have likely relied on data from literature or their own prior experience, but what is needed is a science-based approach. Our analyses are also aimed at those who use plant-based materials in their products to reduce the proportion of meat, meaning that many food producers will ultimately benefit from this study. This is especially the case as we can present the results in our numerous continuing education courses," Roasto said. In addition to alternative products, the research team is also analyzing high-risk plant-based foods to assess food safety risks associated with their consumption.

According to Roasto, the study is highly practical in nature. Based on its findings, there are plans to update existing guidelines, such as those for determining food shelf life, the second part of which concerns microbiological guideline values for foods. "We want to supplement this based on the results of our analyses and introduce a separate category for alternative products. We will also present the results of the TemTA52 project in training courses for companies," the professor outlined.

Mati Roasto delivered a presentation titled "Food Safety of Plant-Based Alternatives to Animal Products: An Overview of the TemTA52 Project" at the conference "Healthy Animal and Healthy Food," held on March 25 at the Estonian University of Life Sciences.

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