Plastic food wraps and chopping boards embedded with antimicrobial technology are just some of the inventions in development that could make our food safer to eat, Jasmin Fox-Skelly reports
Every year 600m people – almost one in 10 people in the world – fall ill after eating contaminated food.1 Of these, 420,000 die, with the majority of deaths occurring in children under five years of age.
Most illnesses are caused by bacteria, viruses and parasites. Common culprits include Norovirus, Salmonella, Campylobacter and Escherichia coli. As well as microbes, food can become contaminated with mould, or through exposure to industrial chemicals, agricultural pesticides, or water containing toxic metals.
Due to the global nature of the food industry, local incidents can quickly evolve into international emergencies. Serious foodborne disease outbreaks have occurred on every continent in the past decade. In 2017, over 200 people in South Africa died after eating meat contaminated with Listeria. The contaminated products were exported to 15 other countries.
Finding the source of the problem can be difficult, as contamination can happen at any stage in the food production chain: from farms, to processing and packaging plants and transport vehicles. However, a range of innovative solutions could help make the food on our plates safer.
Smart packaging
One solution is to incorporate antimicrobial compounds into food packaging. This is exactly what researchers behind the EU-funded NanoPack project have done. The international team of scientists, led by a team from The Technion – Israel Institute of Technology, have created a flexible plastic food film with antimicrobial properties.
Their plastic film contains natural oils extracted from plants like oregano and thyme – known to prevent the growth of microbes, including bacteria, yeast and moulds. To ensure a slow delivery of the antimicrobial compounds, the oils are encapsulated within tiny tubes known as halloysite nanotubes (HNTs). Once incorporated into food packaging samples, the researchers report that the nanotubes slowly release the antimicrobial oils into the surrounding air – slowing oxidation and preventing microbial growth.
Tests show that the packaging, which is fully recyclable, prevents the growth of mould in bread by at least three weeks. It also extends the shelf life of fresh cherries and yellow cheese by 40% and 50%, respectively.2 The team hopes to launch the product commercially within the next two years.
Meanwhile, researchers at Oregon State University, US, have developed an edible plastic film containing antimicrobial compounds extracted from crustacean shells. Edible films for food packaging have been in development for decades, but progress is hampered because they dissolve when exposed to water – a big problem for packaged foods with a high water content.
To solve this challenge, Yanyun Zhao, Professor of food science, made the film from cellulose nanofibres derived from wood pulp. To make a packaging that could prevent bacterial contamination, she also incorporated chitosan into the film. Chitosan is a fibre with natural antimicrobial and antioxidant properties found in crab and shrimp shells. The resulting film is similar in texture and appearance to a plastic wrap and lab tests show it inhibits the growth of E. coli and Listeria on fresh beef patties and prevents surface moisture transfer between the layered patties.3
Antimicrobials don’t just reduce pathogens in packaged foods and improve food safety, they can also extend the shelf life of foods by reducing microbial spoilage.
Catherine Cutter Professor of food science, Pennsylvania State University
The film could replace non-biodegradable waxed papers or other synthetic polymers currently used in meat packaging. Alternatively, it could be used to extend the shelf life of other foods with wet surfaces, such as cheese, or cut fruit and vegetables.
Catherine Cutter, Professor of food science at Pennsylvania State University, US, has developed an alternative edible and antimicrobial food wrap, in this case containing a polysaccharide polymer known as pullulan. This polymer is subsequently infused with a natural antibacterial compound called lauric arginate. Both pullulan and lauric arginate (LAE) are already approved for use in foods.
‘When the antimicrobial pullulan layer comes in contact with moisture associated with the food, it releases the LAE directly onto the surface of the food,’ says Cutter. ‘If there are pathogenic or spoilage microbes present on the surface, they are inhibited by the antimicrobial.’
In a recent study, sheets of the plastic were used to vacuum-pack pieces of raw beef, chicken and ready-to-eat turkey breast. The food had been pre-inoculated with E. coli, Salmonella spp., Listeria monocytogenes and Staphylococcus aureus bacteria. After 28 days in contact with the plastic, the bacterial populations had shrunk by more than 99.9%.4
According to Cutter, antimicrobial packaging could benefit society in several ways. ‘Antimicrobials don’t just reduce pathogens in packaged foods and improve food safety, they can also extend the shelf life of foods by reducing microbial spoilage.’ This means that foods would last longer and would be less likely to be thrown away. The UN Environment Programme estimates 17% of the food produced globally each year is wasted, amounting to 931m t of food.
Pesticide residue reassurance
Data from the US FDA’s latest Pesticide Data Monitoring program should reassure US consumers – and pet owners – of the safety of levels of pesticides.
The news came following reports of an advert for an essential oil wash to cleanse vegetables of pesticides (acsh.org/news/2021/11/01/toxic-pesticides-food-new-fda-safety-data-should-calm-your-fears-15905). FDA found that 98.7% of domestic and 89.1% of import human foods were compliant with federal standards. No pesticide chemical residues were found in 42.4% of the domestic and 49.4% of the import samples.
Animal products – including pet foods – posed a similarly minimal risk, FDA found. Of 365 animal food samples analysed for pesticides, the Agency found that 98.4% of domestic and 95.4% of import animal food samples were compliant with federal standards.
No pesticide chemical residues were found in 40.9% of the domestic and 43.7% of imported animal food samples.
The US Environmental Protection Agency (EPA) sets safety standards for pesticide residues in food that allow a substantial margin of safety (typically 100-fold) of allowed residues to establish reasonable certainty of no harm to humans.
Food prep
Ensuring packaged food stays fresh is one challenge. However, most incidents of food poisoning occur after food is brought home, or into professional kitchens. Bad hygiene practices, and inadequate cooking and food storage practices are usually to blame. According to a 2020 review by the UK Food Standards Agency (FSA), for instance, eating out and takeaways account for an estimated 63% of all foodborne norovirus cases.5 Adopting good personal and food hygiene practices could reduce many of these cases, but compliance in busy restaurants can often be low.
But restaurant managers could now have another tool in their arsenal – a compound that effectively stops bacteria from growing on plastic surfaces, chopping boards and other kitchen equipment. Plastics additive Saniconcentrate is marketed by Parx Materials, a Dutch company specialising in antimicrobial compounds. Rather than a protective coating, Saniconcentrate is incorporated into plastics during manufacture, for example, during plastic injection, extrusion or blow moulding processes. In a recent study, Parx Materials incorporated Saniconcentrate into small polyethylene chopping boards used daily by staff for normal food preparation, including cutting bread, fruit, vegetables, meats, chicken and citrus fruits.
Tests showed that the chopping boards reduced levels of E. coli by 99.5% and Staphylococcus aureus by 99%, even after more than 1000 dishwasher cycles. This is important because antimicrobial products used in kitchens must withstand thousands of dishwasher cycles and washes during their lifespan.
‘These tests clearly confirm our technology is an intrinsic part of the material and is not migrating under the harsh conditions of a dishwasher,’ commented Michaël van der Jagt, CEO of Parx Materials. ‘Withstanding 1000 dishwasher cycles without losing effectiveness is a tremendous milestone, setting new standards.’
The market for antimicrobial compounds has exploded since the global coronavirus pandemic, with over 100 companies currently developing or marketing antimicrobial products. However, many of these contain biocides which would make them unsuitable for use in kitchens.
‘Roughly all of the other available solutions in the market contain toxic substances such as silver, which can migrate out of the material and end up in or on the food,’ says van der Jagt. ‘These types of solutions also cause resistance, contributing to the rise of the superbug.’
Although the formulation of the compound is proprietary, the patenting application submitted by Parx Materials reveals the formulation is based on an inert form of zinc housed within a polymer.6 Rather than killing bacteria directly, the technology works like human skin by forming a mechanical barrier and preventing microbes from adhering to surfaces. According to van der Jagt, it does this through employing van der Waals forces. As the chemical is inert and does not travel out of the plastic or kill the bacteria directly, it does not lead to resistance and is safe for use in food-grade items.
Nadia Tsao, Principal Analyst at UK-based business intelligence firm IDTechEx, believes that antimicrobial solutions like Saniconcentrate could play an increasing role in food safety in the future. ‘Antimicrobial technology embedded in worktops, chopping boards and knives can provide additional protection beyond regular cleaning and disinfection protocols, decreasing the number of contaminated food contact surfaces as a source of food poisoning-related illnesses,’ she says.
However, Tom Humphrey, retired Professor of bacteriology and food safety at Swansea University, UK, is sceptical about claims that the material could reduce food poisoning. ‘My own view is that of course one doesn’t want pathogenic organisms lingering around on work surfaces in kitchens, however, the greatest threat is from things that aren’t cooked properly.’
‘The real problem is bacteria inside foods, such as Salmonella in eggs, or Campylobacter in chickens. Whilst I don’t think what they are doing is useless, I don’t think it will make the impact they are hoping for, especially as bugs like E. coli don’t grow well on dry plastic kitchen surfaces anyway.’
From microbe-busting food wraps to virus killing chopping boards, technology could cut food poisoning cases. However sometimes the old techniques are the best. Washing hands and cooking and storing food properly is still the number one way to prevent food poisoning at home.
Combating food fraud
As our world becomes more connected, food chains now span the globe, incorporating a complex network of food producers and manufacturers. Contaminants can be introduced at any stage.
Sometimes this can happen accidentally, for instance, in 2017, millions of eggs across Europe were recalled after residues of the pesticide fipronil were detected. However deliberate contamination or adulteration of food is also common. In 2013, tens of millions of food products across Europe had to be withdrawn after beef burgers and other ready meals were found to contain up to 100% horsemeat. Although most cases of deliberate food fraud are not identified, it’s estimated that 10-30% of all commercially sold food is fraudulent – thought to cost the global food industry up to $40bn/year.
The most common type of food fraud is improper labelling of a product’s country of origin. Olive oil from Italy commands a much higher price than the same products from other countries, so there is a huge financial incentive to lie on food packaging labels. However, thanks to modern characterisation technologies, companies and food standards agencies can now take steps to identify food fraud.
One commonly used method to identify the origin of plant-based products is called stable isotope analysis. This involves measuring a specific isotope of oxygen (18O) found in organic matter and comparing it with 16O to give a ratio (δ18O). The δ18O in plants is highly sensitive to local precipitation and climate conditions. This means that each product has a highly specific isotopic fingerprint that depends on its location.
Until now, the process of investigating fraud involved not only collecting reference data from the claimed country of origin, but also comparative data from other regions to validate or disprove the product’s origin. This is highly time consuming and costly.
Now botanists at the University of Basel, Switzerland, have developed a model that can determine the origin of food far more efficiently.7 The model uses publicly available data on local temperature, precipitation and humidity, as well as the growing season of a plant to predict its location.
Basel botanist Florian Cueni tested and validated the model on a unique δ18O reference dataset for strawberries collected across Europe over 11 years. The results showed the model can simulate the origin of the strawberries with a high degree of accuracy, but it could also be used to determine the origin of any plant product.
References
1 World Health Organization Food Safety: who.int/news-room/fact-sheets/detail/food-safety
2 NanoPack’s Active Food Packaging: nanopack.eu/2019/11/14/nanopacks-active-food-packaging-shows-impressive-results-in-extending-food-shelf-life/
3 LWT – Food Science and Technology, 2017, doi.org/10.1016/j.lwt.2017.05.013
4 International Journal of Food Microbiology, 2020, doi.org/10.1016/j.ijfoodmicro.2020.108519
5 Norovirus Attribution Study (NoVAS) (2020): food.gov.uk/research/foodborne-diseases/norovirus-attribution-study
6 Parx Plastics Information Document (2018): static1.squarespace.com/static/5fd9f0bacbd7176e0e0fb001/t/5fea22d6c45737001d81edc8/1609179868683/Parx_DocInfo_EuronextAcces_Aurgalys_20180430_final.pdf
7 Sci. Rep., 2021, doi.org/10.1038/s41598-021-96722-9
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