Identification of Nonpathogenic Surrogate Bacteria Applicable for Industrial-Scale Gaseous Chlorine Dioxide Treatment on Baby Carrots

Authors: GUAN, JIEWEN - Washington State University; TANG, JUMING - Washington State University; Lacombe, Alison; Bridges, David; RANE, BHARGAVI - Washington State University; SABLANI, SHYAM - Washington State University; Wu, Vivian

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/19/2019
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Vegetables are highly associated with outbreaks since they are often consumed raw or minimal processed. Gaseous chlorine dioxide (ClO2) is an effective method to control foodborne pathogens in fresh produce. Industrial-scale gaseous ClO2 treatment may help fresh produce industry to decontaminate the produce and enhance the safety. The purpose of this study was to investigate inactivation kinetics of Escherichia coli and their potential nonpathogenic surrogate bacteria in order to support future development and validation of commercial gaseous ClO2 decontamination in carrots manufacturing plants. Two separate cocktails of five pathogenic and nonpathogenic E. coli strains were inoculated onto 200 grams of baby carrots. Gaseous ClO2 was generated inside of the treatment chamber using a dry mix sachet method, by mixing equal amounts of sodium chlorite and activating acids in a sachet. Both sample groups were treated simultaneously in the same closed chamber at different exposure times. The initial treatment doses were 0.01, 0.03 and 0.06 mg ClO2/g carrots and the total exposure times were 0.5, 1, 2 and 3 hours. Temperature (25±5°C) and relative humidity (90±8%) were measured inside of the chamber. After 1-hour treatment, both pathogenic and nonpathogenic E. coli had similar reduction of 4 log, 4.5 log and 5 log CFU/g at ClO2 initial doses of 0.01, 0.03 and 0.06 mg ClO2/g carrots, respectively. Linear trends were observed between initial doses and log reductions. No significant difference was observed with the inactivation between pathogenic and nonpathogenic strains for all treatments. There were no further reductions after extending total exposure times to 2 hours and 3 hours. This is the first study that analyzes kinetics of gaseous ClO2 inactivation against both surrogate and pathogens on baby carrots. This study identifies a nonpathogenic surrogate cocktail with equivalent resistance to gaseous ClO2, suitable for representing pathogenic E. coli in future industrial experiments.