Bioprotection against listeria: Lactic acid can inhibit Listeria growth in packed salmon

11 Jul 2019 --- Lactobacillus sakei CTC494 has proven efficacious in inhibiting the growth of Listeria monocytogenes in vacuum packed salmon. The biopreservation technique was discovered by researchers at the Spanish Institute of Agrifood Research and Technology (IRTA) and builds on the use of lactic acid bacteria to control potential harmful pathogens in foods. The study findings have been published in the journal Food Microbiology.

“Food packaging is a key element for assuring and improving food safety. Besides the physical protection of the food against contamination, the packaging strategy strongly determines the behavior of the microorganisms present in the packaged food. Besides the control of the gas composition, e.g. with modified atmosphere or vacuum, active packaging strategies enable to provide specific antimicrobial effects, thus enhancing the safety and extending the shelf life of perishable products,” the team tells PackagingInsights.

A number of listeria cases have plagued the food industry – particularly impacting smoked salmon products. The European Food Safety Authority (EFSA) recently warned of a listeriosis outbreak caused by Listeria monocytogenes in trout and cold smoked salmon that affected five European countries and caused the death of five people. The first cluster of cases linked to the consumption of ready-to-eat smoked salmon produced in Poland was reported in Denmark last August.

Ready-to-eat smoked salmon and smoked trout are considered to be especially at risk.

Ready-to-eat smoked salmon and smoked trout are considered to be especially at risk. 

Lactic acid bacteria are present in the microbiota of many foods, including salmon and, in some cases, produce substances with important antimicrobial activity. They can be used as biopreservation agents for the control of pathogens such as Listeria monocytogenes and pose no harm to consumers.

The team of researchers at IRTA has now demonstrated the efficacy of the Lactobacillus sakei CTC494 strain to completely inhibit the growth of Listeria monocytogenes in vacuum-packed salmon samples kept in cooling conditions for 21 days, independently of the physicochemical characteristics of the product.

The team says that “one main challenge was to find the lactic acid bacteria strain with a high antilisteria activity, while not modifying the sensory properties of the product being biopreserved. Lactic acid bacteria constitute a microbial group with great potential and interesting properties for food production (as starter cultures for fermented food) and food preservation as bioprotective cultures to fight foodborne pathogens.” 

The public has viewed active packaging solutions with caution in the past, despite the fact that they are often touted as offering increased food safety, extended shelf-life, improved freshness and reduced food waste. However, a recent report carried out by the EU-funded NanoPack Project has revealed that consumers are increasingly willing to use antimicrobial solutions in food packaging.

The NanoPack Project has reported significant advancements in the shelf-life and quality extension of a range of foods when packaged in nano-active materials. Funded by the EU Horizon 2020 scheme, the project aims to mainstream nanotechnologies in commercial flexible packaging.

Preventing foodborne disease
The industry has been innovating on a number of fronts in an attempt to halt the spread of bacteria in food that can be lethal to consumers. Earlier this year, Penn State University researchers found that employing advanced genetic-tracing techniques and sharing the data produced in real time could limit the spread of bacteria – Bacillus cereus – which causes foodborne illness. As part of the study, the researchers implemented whole-genome sequencing of a pathogen-outbreak investigation, following an outbreak of foodborne illnesses in New York in 2016.

Edited by Laxmi Haigh