A bulletin for the Australian Food Industry May 2000
Contents: Packaged minimally-processed fresh-cut vegetables | Decontamination of fresh fruit and vegetables | Improving the safety of fresh produce | Use of sanitisers at low temperature
Decontamination of fresh fruit and vegetables
The Food and Agriculture Organisation and the World Health Organisation have recently published in their Food Safety Issues series a review titled Surface decontamination of fruits and vegetables eaten raw (download PDF). The principal author is Dr Larry Beuchat, Center for Food Safety & Quality Enhancement, University of Georgia, USA. Dr Beuchat has published extensively in this field and the review cites more than 250 references covering pathogens associated with fruits and vegetables and studies to investigate the efficacy of a range of methods for surface decontamination.
The author stresses that the document should not be seen as a recommendation for the use of chemical disinfectant agents for surface decontamination of fruits and vegetables. Further research is needed to understand better the mechanisms through which pathogens can contaminate raw fruits and vegetables and procedures for killing or removing pathogens once they are present.
- none of the chemical or physical treatments currently used to disinfect raw fruits and vegetables can be relied upon to eliminate all types of pathogens from the surface or internal tissues;
- Listeria monocytogenes is generally more resistant to disinfectants than Salmonella, E. coli 0157:H7 and Shigella;
- little is known about the efficacy of disinfectants in killing parasites and viruses on fruits and vegetables;
- washing fruits and vegetables in potable water removes a portion of microbial cells. In some instances, vigorous washing can be as effective as treatment with water containing 200mg/L chlorine, which generally reduces populations by 10-100-fold. Dr Beuchat emphasises the importance of pH control when using chlorine as the sanitiser;
- the temperature of wash water should be higher than that of the fruits and vegetables to minimise uptake of microorganisms by tissues;
- although disinfectants have variable effects on pathogen control on fresh fruits and vegetables, they are certainly useful for sanitising wash water to prevent contamination of produce that would result from using waters that are not safe;
- prevention of contamination of fruits and vegetables with pathogens at all points from the field to the plate through application of good agricultural practices, good manufacturing practices and HACCP programs is preferred to application of chemical disinfectants after contamination has occurred.
Dr Beuchat also notes that globalisation of the food supply may contribute to the increase in diseases associated with the consumption of raw fruits and vegetables in industrialised countries. He cites outbreaks of shigellosis in Norway, Sweden and the United Kingdom due to contaminated lettuce imported from Southern Europe and cyclosporiasis in the United States linked to consumption of raspberries imported from Guatemala as examples.
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