Risk factors for melon contamination by Salmonella revealed

Epidemiological data from the EU identified one salmonellosis outbreak associated with consumption of both pre-cut and whole melon between 2007 and 2012.

The European Commission asked EFSA’s Panel on Biological Hazards (BIOHAZ Panel) to prepare a Scientific Opinion on the public health risk posed by pathogens that may contaminate food of non-animal origin (FoNAO).

It is the third opinion out of five and addresses the risk from Salmonella in melons​.

The opinion covers the main risk factors for melons, including agricultural production systems, origin and further processing, recommend possible specific mitigation options and assess their effectiveness and efficiency to reduce the risk and recommend microbiological criteria.

Current legal framework does not include microbiological criteria for the primary production stage.

Melon risk factors​

The BIOHAZ Panel concluded that the risk factors for contamination of melons and watermelons with Salmonellaare poorly documented but are likely to include several things based on what is known for other pathogens or other fresh produce.

Environmental factors, such as proximity to animal rearing operations and climatic conditions that increase the transfer to pathogens from their reservoirs to the melon and watermelon plants and contact with animal reservoirs, gaining access to melon and watermelon growing areas are factors.

Use of untreated or insufficiently treated organic amendments; and/or contaminated water for

irrigation or for application of agricultural chemicals and contamination or cross-contamination by harvesters, food handlers and equipment at harvest or post-harvest were other areas.

Fruit damage during harvest as well as cracking before or during harvest are additional risk factors for Salmonella contamination since melon and watermelon flesh has an internal pH of 5.1-6.7 and represents a good substrate for the growth of this bacterium.

Risk factors associated with Salmonellain outbreaks in the US and Canada associated with melon and watermelon consumption were wash water temperature, contaminated hydro-cooler water, damaged rind, rind fungus rot, workers‟ hands and contaminated conveyor belts and equipment.

Edible portions of the melon and watermelon flesh may be contaminated in the cutting or rind removal process because the knife blade may spread microbial contamination on the outside rind of the melon and watermelon to the inner edible portions.

Mitigation options​

For the recommendation of mitigation options and assessment of their effectiveness and efficiency to reduce risk, the panel said that appropriate implementation of food safety management systems including Good Agricultural Practices (GAP), Good Hygiene Practices (GHP) and Good Manufacturing Practices (GMP), should be primary objectives of producers.

Risk factors for contamination during agricultural production include production practices, growth conditions and contact during growth of the outside fruit surface with the environment, with intrinsic, extrinsic, harvesting and processing factors will affect the microbial status of melons and watermelons at the time of eating in a similar way to leafy greens.

Variability in the production systems and associated environments for melon and watermelon can lead to a range of unintentional or intentional inputs that are potential sources of safety hazards.

The sources of contamination will vary considerably from one type of crop production to another as well as between one particular setting/context to another, even for the same crop.

Melon surface​

Factors linked to the adherence and survival of pathogens with melons includes the fact that they have smooth or netted rind surfaces, said the panel.  

Morphological characteristics of certain types will be prone to attachments by microbial pathogens.

Salmonella adhere to the surface of cantaloupe melons, although there is variation between different serovars.

Although cooling melons and watermelons with water during post-harvest handling may reduce

microbial loads on the outside surface, this may also be a source of microbial cross-contamination.

Delays in melon and watermelon cooling from ambient temperatures (20-35 °C) to recommended temperatures between 10 and 14 °C, when rinds are wet from cooling operations or from dew, may permit multiplication of foodborne pathogens on the rind surface.