Gaseous Chlorine Dioxide for Postharvest Treatment of Produce

Chlorine dioxide (ClO2) and sodium hypochlorite (NaClO) are two chlorinated oxidizing agents that are implemented in water treatment and postharvest processing of fresh produce. While the antibacterial mechanisms of NaClO have been investigated, there are comparatively few studies that have looked at how ClO2 kills bacteria. Therefore, the objective of this study was to compare the inactivation pathways of ClO2 and NaClO against Escherichia coli O157:H7. Treatments consisted of 2.5, 5, and 10 ppm ClO2 or 50, 100, and 200 ppm NaClO for 5, 10, and 15 min. Maximum log reductions of E. coli O157:H7 were 5.5 and 5.1 after treatment with ClO2 or NaClO, respectively. Bacterial inactivation was measured using log reductions, intracellular reactive oxygen species (ROS) using with 2′,7′–dichlorofluorescin diacetate (DCFDA) or aminophenyl fluorescein (APF) probes, relative values of NAD+, NADH, NADP+, and NADPH cofactors. Additionally, the expression of three key genes involved in ROS stress was measured via RT-PCR. Levels of intracellular ROS measured by DCFDA after ClO2 treatment were significantly higher than those found after treatment in NaClO. Additionally, NaClO treatment resulted in upregulation of ROS-defense genes, while expression of the same genes was typically at base levels or downregulated after ClO2 treatment. As the concentrations of both treatments increased, the NADP+:NADPH ratio shifted to the cofactor being predominantly present as NADP+. These data indicate that ClO2 and NaClO damage E. coli O157:H7 via measurably different mechanisms and that ClO2 does not appear to cause substantial oxidative stress to E. coli O157:H7 directly.

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Reduction of Listeria monocytogenes and Salmonella Typhimurium on Blueberries through Brief Exposure to Antimicrobial Solutions Coupled with Freezing

Bridges

Tadepalli

Anderson

et al. 2019

Journal of Food Protection

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This study evaluated the efficacy of different brief-exposure antibacterial washes (≤3 min) coupled with frozen storage against Listeria monocytogenes and Salmonella Typhimurium on blueberries. Inoculated berries where treated with sodium hypochlorite (NaOCl, 200 ppm), chlorine dioxide (15 ppm), ozone (3 and 5 ppm), or lactic acid (2%) for short exposure times (10 s, 1 min, or 3 min), and antibacterial effectiveness was determined with or without an additional freezing hurdle (−12°C, 1 week). Wash treatments alone resulted maximum log reductions from 1.0 to 2.8, while the additional freezing step increased this to a range from 3.7 to 6.6. The greatest reduction of L. monocytogenes (6.6 log) and Salmonella Typhimurium (5.3 log) was observed after freezing combined with 3 min of exposure to 2% lactic acid or 200 ppm of NaOCl, respectfully. After treatment, no residue was measured by the methodologies used. However, lactic acid treatment resulted in changes of color and aroma. In conclusion, wash treatments of blueberries using short exposure times had antimicrobial effectiveness (1.0 to 2.8 log reductions) and can be enhanced by coupling with freezing. HIGHLIGHTS

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Gaseous Chlorine Dioxide for Postharvest Treatment of Produce

Cited by 3 publications

References 47 publications

Decontamination of Fruits

Decontamination of Fruits

Fundamental Differences in Inactivation Mechanisms of Escherichia coli O157:H7 Between Chlorine Dioxide and Sodium Hypochlorite

Reduction of Listeria monocytogenes and Salmonella Typhimurium on Blueberries through Brief Exposure to Antimicrobial Solutions Coupled with Freezing

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