From gene-edited phages that “hijack” E. Coli pathogens to plasma-activated water that kills harmful bacteria on meat, we look at some promising next-generation food safety techniques.
At Food Ingredients Europe (Fi Europe) 2022, three award-winning food manufacturing researchers presented their findings. We explore their research results, how they are set to impact today’s manufacturers and what they mean for the future of food.
Koentadi Hadinoto, a current PhD student at the University of New South Wales in Sydney, Australia, has undertaken research exploring plasma for meat safety, examining how meat is handled from the farm to the supermarket shelf.
In Australia, one person consumes approximately 110 kilograms (kgs) of meat each year, and the meat industry contributes about $17.6 billion to the economy, Hadinito told the Fi Europe 2022 audience. Making meat safe is critical to the sector’s success. “Meat safety not only ensures the meat you consume is free from harmful bacteria but also guarantees the integrity of the product is maintained from the farm to the market,” said Hadinoto.
In Australia, harmful bacteria are removed by water washing, but this traditional treatment consumes at least 1.5 million litres daily. In the US, manufacturers introduce lactic acid during the washing stage, which can cause the meat to brown.
Finding a better solution to achieving meat safety that was effective and environmentally conscious was the inspiration behind Hadinoto’s research. Enter plasma, which accounts for more than 99% of the universe’s matter, he said.
Meat manufacturers can use plasma to disinfect beef from harmful bacteria. Plasma can be generated by using electricity, which then converts water and air into reactive molecules. It creates an end-product known as plasma-activated water, which is sustainable because it does not add dangerous chemicals, he said.
The plasma is also energy efficient, requiring the same amount of electricity as a single lightbulb. Following Hadinoto’s research, the PhD student has developed a plasma technology that can kill more than 99% of harmful bacteria, such as E. Coli and Salmonella, in seconds without burning the meat.
Sharing the study ’s results, Hadinoto said that washing the beef with plasma-activated water can kill more Salmonella than washing with water alone. The findings indicate that the meat industry can reduce water use by at least 40% while maintaining the meat’s quality attributes. “I believe this research is fundamental to replace the use of chemical disinfectants for meat safety,” Hadinoto said.
Grace Dewi, a PhD candidate from the University of Minnesota, presented her research on probiotics and plant-derived antimicrobials against Salmonella in poultry production. The problematic pathogen is challenging for the food industry as it can survive in many environments and so many food products are susceptible to contamination. Consumption of chicken and turkey is responsible for almost a quarter of these illnesses, Dewi said.
Salmonella is particularly challenging in food-producing animals. Birds can serve as a natural reservoir host for Salmonella, which typically colonises them without presenting symptoms. Furthermore, the birds can contract the pathogen from many farm sources. As a result, it takes a lot of work to prevent transmission during the pre-harvest production phase.
The research study explored potential pre-harvest interventions to limit Salmonella persistence on farms and alleviate the burden on subsequent stages of production. In the study, Dewi also examined post-harvest interventions to reduce Salmonella further and prevent cross-contamination during processing.
Specifically, Dewi’s research examines the use of autochthonous lactobacillus strains, which researchers isolated from commercial turkeys, and three generally recognised as safe (GRAS status) plant-derived antimicrobials (PDAs): lemongrass essential oil, citral and transmaldehyde.
Dewi conducted a series of experiments and found the PDAs and lactobacillus exert direct antimicrobial effects against Salmonella in vitro, even in the presence of contaminants. Lactobacillus and transmaldehyde can reduce Salmonella in vivo and thus may serve as an effective pre-harvest intervention.
The PDAs could be administered during processing to prevent transmission or directly to the final product, and the researchers aim to develop an outreach programme to help poultry producers.
Food microbiology PhD candidate at Cornell University, Meghan McGillin, sees the field of microbiology with biocontrol encapsulating the shifting paradigm currently taking place within the food industry.
It challenges the idea that “germs equal pathogens” by acknowledging the complexity, diversity, and potential microbial collaborations that can provide benefits. “The link between antibiotic use in primary food production and resistance throughout our farm-to-fork continuum is overwhelming,” said McGillin.
Exploring the necessity of new-wave solutions that balance the molecular issue of antimicrobial resistance with the macro ramifications of climate change, the researchers investigated bacteriophages, or phages.
Phages infect their bacterial hosts for the sole purpose of replicating because they lack the biomolecular machinery to do so independently. They are diverse, abundant, and do not infect cells.
Focusing on phages in the context of biocontrol for food safety, McGillin explained that when a phage infects a cell, it hijacks its gene replication and protein expression machinery to create replicates of itself, and it repeats this process until the cell has completely exhausted itself. It then releases these newly replicated phages into the environment while simultaneously killing the host. It continues the cycle until no more cells are left to infect, thus amplifying the antibacterial effect.
Phages can also be highly specific and implemented at any point in the farm-to-fork continuum. They can target particular pathogens on a strain without impacting the overall microbial diversity and function, which is an important distinction compared to antibiotics or broad-spectrum antibiotics.
However, a major biological concern of phages is resistance, which is not fully understood in its emergence nor in the efficacy of counter-resistant methods. McGillin’s research focuses on these two areas, which uses a novel phage system and hopes to deepen understanding of phage resistance.
The research team inserted an E. Coli-specific bacteriocin colicin into the genome of a phage, resulting in a synthetically engineered phage that can coexpress a colicin. When this phage infects its bacterial host, it produces the phage and this colicin. E. Coli would be able to survive this treatment if it had resistance to not just the phage but also the colicin.
The researchers tested this out in a population of E. Coli with a resistant subpopulation. Depending on the colicin and ratio of resistance to sensitive cells, the study found this treatment either had a delayed outgrowth of the resistant population or was wholly suppressed.
“Moving forward, we want to see how bacteria evolved to gain resistance to this treatment. We are doing that by characterising the rate at which resistance emerges from an entirely sensitive E-Coli population,” says McGillin.
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