Evaluation of Current Operating Standards for Chlorine Dioxide in Disinfection of Dump Tank and Flume for Fresh Tomatoes

Abstract

<jats:p>Standard postharvest unit operations that rely on copious water contact, such as fruit unloading and washing, approach the criteria for a true critical control point in fresh tomato production. Performance data for approved sanitizers that reflect commercial systems are needed to set standards for audit compliance. This study was conducted to evaluate the efficacy of chlorine dioxide (ClO2) for water disinfection as an objective assessment of recent industry-adopted standards for dump tank and flume management in fresh tomato packing operations. On-site assessments were conducted during eight temporally distinct shifts in two Florida packinghouses and one California packinghouse. Microbiological analyses of incoming and washed fruit and dump and flume system water were evaluated. Water temperature, pH, turbidity, conductivity, and oxidation-reduction potential (ORP) were monitored. Reduction in populations of mesophilic and coliform bacteria on fruit was not significant, and populations were significantly higher (P &amp;lt; 0.05) after washing. Escherichia coli was near the limit of detection in dump tanks but consistently below the detection limit in flumes. Turbidity and conductivity increased with loads of incoming tomatoes. Water temperature varied during daily operations, but pH and ORP mostly remained constant. The industry standard positive temperature differential of 5.5°C between water and fruit pulp was not maintained in tanks during the full daily operation. ORP values were significantly higher in the flume than in the dump tank. A positive correlation was found between ORP and temperature, and negative correlations were found between ORP and turbidity, total mesophilic bacteria, and coliforms. This study provides in-plant data indicating that ClO2 can be an effective sanitizer in flume and spray-wash systems, but current operational limitations restrict its performance in dump tanks. Under current conditions, ClO2 alone is unlikely to allow the fresh tomato industry to meet its microbiological quality goals under typical commercial conditions.</jats:p>

Selection Criteria for Water Disinfection Techniques in Agricultural Practices

“…There are some major disadvantages associated with chlorine, i.e., formation of disinfection by-products (DBPs) in the water, the persistence of chlorine residuals with detrimental effects on aquatic life, the weakness of chlorination against protozoan parasites and some viruses, and the use of high chlorine concentrations can lead to chlorine gas formation which may affect worker comfort and health (Trussell, 1998;Lazarova et al, 1999;Suslow, 2004b;Saad et al, 2005;Hua and Reckhow, 2007;Shields et al, 2008;Tomas-Callejas et al, 2012c). This illustrates that chlorination is not the ultimate solution for all water disinfection practices and dependent on the objective, certain disinfection techniques will prove more suitable than others.…”

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“…88 However, the amount of total aerobic mesophilic and coliform bacteria was not reduced, but increased after a wash with this antimicrobial. 89 This indicates that chlorine dioxide alone is incapable of ensuring microbiological quality of fresh produce.…”

Chlorine dioxide dose, water quality and temperature affect the oxidative status of tomato processing water and its ability to inactivate Salmonella

“…Synthetic tomato processing water was designed to reproduce a consensus processed water composition based on previous water assessment at tomato packinghouses (Tomás-Callejas et al, 2011). To simulate the background oxidative demand of processing water, tomato plants with adhering soil were collected from University of California (Davis, CA) research farm.…”

“…Turbidity can vary from 0 to 300 NTU, or greater, and from 0 to 50 NTU for dump tank and flume systems, respectively, during a regular processing day. Moreover, processing water temperature in dump tank and flume can reach 40 C, or higher, to avoid water infiltration into tomatoes (Tomás-Callejas et al, 2011).…”