Leafy salads – modelling ways to prevent attachment of pathogens
Project blog – 18 November 2016
A new study highlights the importance of careful handling of leafy salads during production, harvesting, packing and distribution to help minimise food safety risks from microbes such as Salmonella.
Like other foods produced in the open, leafy salad can from time-to-time pick up microbes that cause food poisoning. Producers take stringent measures to minimise the risk of this, and Salmonella outbreaks associated with them are low – averaging around 1 per year across the EU from 2004-12. However, as with all food-borne pathogens, continued vigilance is important.
A PhD research project (Modelling ways to prevent attachment of enteric pathogens to fresh salad produce) led by the University of Leicester, in which we are an industrial partner, is investigating the factors that contribute to the risk from pathogens on leafy salads.
The aim is to use the new knowledge to further improve production, harvesting and handling practices. Data* from this project indicates that juice from damaged leaves can help Salmonella cells, if present, to attach to surfaces (e.g. the leaf or bag) at room temperature, and can enhance their growth in cultures containing leaf extract. This would suggest the need to minimise leaf damage during harvest and handling, reduce the amount of any residual juice on product, maintain good hygiene throughout production, and maintain temperature control during distribution and storage.
Helping to understand risk
The project does not indicate any increased risk to eating leafy salads. It does provide a better understanding of the factors contributing to food poisoning risks and highlights the need for continued good practice in their production and preparation.
The aim is to use this understanding to explore new ways of further reducing the existing low risk - for example, reducing damage to leaves during their harvest, washing and handling though all stages of production and preparation by producers, suppliers and consumers. Future research will also explore technologies that might be effective in reducing the observed effects of the juice.
Practical implications
Producers and packers should continue using good agricultural practice and good hygienic practice in the production, preparation and packing of leafy salads. This includes the current, widely adopted good agricultural practices, irrigation with clean water, produce washing, hygienic handling during harvest and bagging, chilling during storage and distribution, clear on-pack instructions on preparation, and ´use–by´ date marking. Detailed practical guidance is available through organisations and schemes such as The Little Red Tractor Fresh Produce Standard and the Global G.A.P measures for good agricultural practice.
With regards to eating leafy salads, which are a nutritious part of the diet, they should be stored, prepared and used according to the guidance on the pack – including refrigeration and use-by instructions.
*To be published in the journal Applied and Environmental Microbiology (from the American Society of Applied Microbiology) at 6.00pm GMT on Friday 18 November on the AEM website
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