Factors Affecting the Attachment of Bacteria to, and Their Detachment from, Prepared Fruit and Vegetable Tissues

Food producers have an urgent need for improved microbiological decontamination of ready-to-eat prepared vegetable tissues. Such tissues often become contaminated in the field. Despite post harvest trimming and decontamination processes, however, this contamination persists during commercial preparation. Scanning electron microscopy of prepared leaf tissues has shown that bacteria can be found on the abaxial and adaxial surfaces. However, the bacteria preferentially occupy the cut surfaces where they multiply throughout storage of the products to form an extensive layer, sometimes many cells thick. Most studies of colonised vegetable tissue surfaces emphasize growth within the entire product, and little work has concerned the initial colonisation process. However, commercial decontamination processes are typically applied to prepared vegetable tissues within a few minutes of chopping, shredding, or dicing. These processes usually involve washing in potable water, with added biocidal compounds such as chlorine. Such washing occurs considerably before establishment of the protective extracellular polysaccharide and yet the washing process still fails to remove all of the bacteria. <P>

This project, therefore, has the following objectives: <OL> <LI> To understand the differing occupancies on prepared, ready to eat plant leaf tissues of target pathogenic bacteria under different environments. <LI> To measure the attachment coefficients (Ka) of Enterobacteriaceae and different serotypes of Listeria monocytogenes and Salmonella enterica under different environments.<LI> To use physical chemistry approaches to identify plant cell wall components acting as attachment sites for bacteria on cut plant tissues. <LI> To use physical chemistry approaches to develop compounds with Ka greater than those of bacteria that will attach to plant cell wall components.