Fresh produce contamination

The forthcoming FEMS congress of Microbiologists will meet in Slovenia at the end of this month to discuss, amongst other topics, ways of reducing contamination in fresh produce.

Although vegetables are good examples of minimally processed foods there is a high risk of contamination, therefore good hygienic measures have to be taken during the production from farm to table. The nature and extent of the health hazards involved in the production and preparation of foods will be considered in depth at the Congress to be held in Ljubljana from 29 June to 3 July.

The world has seen significant changes in eating habits and consumption of fresh produce is increasingly becoming important in the diet of many people, especially reflected in the increased demand for organically produced foods. In the production and processing of fresh produce quality and hygiene are the most important criteria for the consumers. Such food products are often eaten raw or with minimal processing and, if contaminated with pathogenic bacteria, may represent a health hazard to consumers.

In recent years several surveys of food-borne pathogens and indicator bacteria have been carried out which have shown that pathogens can be found, often in small amounts, in these products. Some work has also been carried out on survival and transfer of most emerging pathogens.

Contamination of vegetables may take place at all stages during production and processing with possible sources being soil, faeces, water and ice, animals, handling of the products, harvesting and processing equipment, and transport. Soil fertilised with farm manure or sewage waste may represent a risk of spreading of different pathogens e.g., E.coli O157, Salmonella, Listeria monocytogenes. Faecally contaminated water that is used for irrigation and washing of products prior to processing may also be a source of these food-borne pathogens.

Scientific evidence suggests that survival of the E.coli O157 bacteria in ovine manure can last up to 21 months, which means that soil fertilised with such manure can also be a source of contamination to vegetables. Salmonella has been detected in vegetables from farms, a wholesale market, supermarkets and small shops.

The prevalence of Salmonella spp. in vegetables is very low in some countries such as Norway, a situation that can be linked to an absence of salmonellae in Norwegian livestock. However, in some countries high concentrations of salmonellae have occurred.

L. monocytogenes is the pathogenic bacterium that can be more frequently isolated from vegetables and has been involved in one of the bigger Listeria outbreaks originating from raw cabbage used in coleslaw. However, L. monocytogens is not often found in types of vegetable such as broccoli, carrots, cauliflower and tomatoes, which has led to speculation that less contact with soil by these vegetables during the growth phase maybe the reason.

All the above findings will be discussed in greater deal at the conference, which will entail a number of presentations and discussion groups. For further details on the conference go to the FEMS website​.