title: Evaluation of current operating standards for chlorine dioxide in disinfection of dump tank and flume for fresh tomatoes.
abstract: 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 (ClO(2)) 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 < 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 ClO(2) can be an effective sanitizer in flume and spray-wash systems, but current operational limitations restrict its performance in dump tanks. Under current conditions, ClO(2) alone is unlikely to allow the fresh  tomato industry to meet its microbiological quality goals under typical commercial conditions.
authors.affiliation: Department of Plant Sciences, University of California, Davis, CA 95616, USA.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Tomás-Callejas
authors.forename: Gabriela
authors.initials: G
authors.lastname: López-Velasco
authors.forename: Angela M
authors.initials: AM
authors.lastname: Valadez
authors.forename: Adrian
authors.initials: A
authors.lastname: Sbodio
authors.forename: Francisco
authors.initials: F
authors.lastname: Artés-Hernández
authors.forename: Michelle D
authors.initials: MD
authors.lastname: Danyluk
authors.forename: Trevor V
authors.initials: TV
authors.lastname: Suslow
mesh_terms: D001419:Bacteria / Q000187:drug effects* / Q000302:isolation & purification; D017606:Chlorine Compounds / Q000494:pharmacology*; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D004202:Disinfectants / Q000494:pharmacology*; D004203:Disinfection / Q000379:methods*; D004305:Dose-Response Relationship, Drug; D005511:Food Handling / Q000379:methods; D006801:Humans; D006863:Hydrogen-Ion Concentration; D018551:Solanum lycopersicum / Q000382:microbiology*; D010084:Oxidation-Reduction; D010087:Oxides / Q000494:pharmacology*; D013696:Temperature; D014871:Water Microbiology
chemical_list: D017606:Chlorine Compounds; D004202:Disinfectants; D010087:Oxides; C025109:chlorine dioxide