Establishment of Critical Operating Standards for Chlorine Dioxide in Disinfection of Dump Tank and Flume Water for Fresh Tomatoes

From an industry and public heath regulatory perspective, postharvest water quality management represents one of the few unit operations that approach a true critical control point for fresh produce. <P>
For fresh tomatoes, much attention has been focused on the importance of dump and flume tank water sanitation for several years due to the recognized potential for introduction and widespread cross-contamination of human pathogens from incoming fruit and environmental sources that may occur. However, while rich in model systems data, little publically accessible data from commercial practices to adequately predict or set functional performance standards in commercial pack and re-pack operations is available to standardize effective control point parameters. <P>The lack of verified and accepted compliance criteria remains a significant barrier and concern for the establishment of audit standards and limits for the fresh tomato industry. Renewed interest and promising recent model system work with chlorine dioxide (ClO2) exist for fresh tomatoes, however very little is known about the management of this sanitizer in dump tank and flume water. <P> On-site surveys conducted in packing facilities located in California and Florida, with matched ClO2 generation systems, will measure bacterial loads of incoming fruit, fruit pulp temperature, water temperature, pH, ClO2 levels, turbidity, conductivity, total suspended solids, redox potential (ORP), and bacterial loads of treated water over a full packing shift on twelve selected seasonal dates. <P>Laboratory studies, using simulated dump water, will further determine and refine dose efficacy for log-reduction of Salmonella in this water and the relationship between ClO2 dose (ppm), ORP (mV), and turbidity (FAU/NTU) as influenced by water temperature. <P>In summary, this proposal will develop scientifically-based critical operating standards for chlorine dioxide use in dump tank and flume tank waters directly applicable for the fresh tomato industry.