Consumption of fresh fruit and vegetables is associated with good nutrition because they provide an important source of vitamins, minerals and biochemical co-factors. In recent years, however, there have been a number of high-profile foodborne illness outbreaks that have been traced back to fresh produce (Hutchison and Monaghan, 2013). A common issue with trying to trace the source of an outbreak is that the contaminated food may have been consumed or spoiled and disposed of before the outbreak is even identified. For the 2011 VTEC outbreak, the investigation concluded it was likely that contaminated soil on the surface of root vegetables was the source of the outbreak strain.
This project aims to provide evidence to underpin future risk assessment and food safety advice on the risks associated with soiled vegetables. Whilst there is evidence for the persistence of E. coli O157 in the growing environment, the extent to which this pathogen is capable of surviving on the surface of soil contaminated vegetables post-harvest and presents a risk to consumer health is currently unclear.
The purpose of this study is to determine the fate of zoonotic agents (with a particular focus on VTEC) contaminating root vegetables as they travel down a typical distribution chain. In order to provide the FSA with information on the most likely causes of contaminated root vegetables, this study plans to mimic six plausible different accidental scenarios that could result in inadvertent contamination or spread of contamination.
These scenarios are described below.
- the deposition of contaminated manure onto root crops close to harvest
- the application of contaminated irrigation water onto a root crop close to harvest. This scenario would also provide the FSA with information on crop contact with contaminated runoff during a heavy rainfall or flood event
- water application the night before harvest, which is common for some crops during periods of low rainfall (because crops such as baby carrots can be damaged by capped soil [a crust of dry surface soil])
- he use of contaminated wash water for root vegetable washing and polishing
- the impact of previously washing a contaminated batch of crops on an uncontaminated batch of crops without changing the wash water
- crop handling by a gloved or ungloved shedding harvest worker with poor hygienic practices after visiting lavatory
The work will be separated into a study of pre-harvest and post-harvest contamination. The pre-harvest studies will involve growing experimental spring-planted crops at Harper Adams University grown under relevant UK field environmental conditions with the application of an appropriate degree of contamination in either water or manure close to harvest. The post-harvest work will identify the persistence of zoonotic agents through product handling from harvest to consumer, delivered via representative multiple retail and independent retail supply chains. In addition, the decontamination efficacy of industry practices of crop washing and polishing (for carrots only) will be assessed. The fate of verocytotoxic E.coli applied in experimental treatments will be determined both following contamination and after exposure to simulated supply chain conditions.