Decontamination of Strawberries Using Batch and Continuous Chlorine Dioxide Gas Treatments

Abstract

Efficacy of chlorine dioxide (ClO2) gas in reducing Escherichia coli O157:H7 and Listeria monocytogenes on strawberries was determined using batch and continuous flow ClO2 gas treatment systems. Effects of continuous ClO2 gas treatment on total aerobic plate count, color, and residual ClO2 and chlorite on strawberries were also evaluated. Strawberries were spot inoculated with 7 to 8 log CFU per strawberry of each pathogen (E. coli O157:H7 and L. monocytogenes), stored for 1 day at 4 degrees C, and treated at 22 degrees C and 90 to 95% relative humidity with 0.2 to 4.0 mg/liter ClO2 gas for 15 or 30 min using a batch treatment system or with 0.6, 1.8, and 3.0 mg/liter for 10 min using a continuous treatment system. Surviving microbial populations were determined using a membrane-transfer plating recovery method. Increased ClO2 gas concentrations resulted in increased log reductions of each pathogen for both the batch and continuous systems. A batch treatment of strawberries with 4 mg/liter ClO2 for 30 min and continuous treatment with 3 mg/liter ClO2 for 10 min achieved greater than a 5-log reduction for both E. coli O157:H7 and L. monocytogenes. After continuous exposure to 3.0 mg/liter ClO2 gas for 10 min followed by 1 week of storage at 4 degrees C, no aerobic microorganisms were detected and the color of the strawberry surface did not change significantly (P > 0.05). Residues of ClO2 and chlorite on strawberries after the treatment were 0.19 +/- 0.33 mg ClO2 per kg and 1.17 +/- 2.02 mg Cl2 per kg, respectively, whereas after 1 week of storage no ClO2 residues were detected and residual chlorite levels were down to 0.07 +/- 0.12 mg Cl2 per kg. These results suggest that ClO2 gas treatment is an effective decontamination technique for improving the safety of strawberries while extending shelf life.

Chlorine Dioxide Gas Retain Postharvest Quality and Shelf Life of Tomato during Modified Atmosphere Packaging Storage

“…Visual quality and freshness retain in tomato fruits by reducing respiration and ethylene production. Shelf life increased in ClO 2 gas treated strawberry fruits by reducing microorganism contamination (Han, Selby, Schultze, Nelson, & Linton, 2004) and, in tomato fruits, the risk of microbial activity was reduced (Trinetta, Morgan, & Linton, 2010). The shelf life of the control, 150 ppm NaOCl, 1 ppm ClO 2 gas 6 hours, 1 ppm ClO 2 gas 12 hours, 1 ppm ClO 2 gas 24 hours, 5 ppm ClO 2 gas 6 hours, and 5 ppm ClO 2 gas 12 hours -treated tomatoes amounted to 14,15,16,17,18,19, and 20 days at 5 ˚C, respectively (Fig.…”

Comparison of multiple chemical sanitizers for reducing Salmonella and Escherichia coli O157:H7 on spinach (Spinacia oleracea) leaves

“…There are several advantages of using ClO 2 rather than hypochlorous acid (HOCl) such as ClO 2 's reduced reactivity with organic material, it has a greater activity at neutral pH, however; its stability may be problematic (Benarde, Snow, Olivieri, & Davidson, 1967). Han, Selby, Schultze, Nelson, and Linton (2004) investigated the use of ClO 2 gas treatments for the decontamination of strawberries and reported a 5 log reduction in microbial counts however, it is important to note that they also stated that the effectiveness of ClO 2 gas treatments for reducing pathogens varies for different types of produce. Lee, Costello, and Kang (2004) reported that E. coli O157:H7 inoculated on lettuce leaves were reduced by 3.4, 4.4, and 6.9 CFU/g after treatment of ClO 2 gas for 30 min, 1 h and 3 h, respectively.…”

Evaluation of chlorine dioxide as an antimicrobial against Botrytis cinerea in California strawberries

“…This information seems to suggest i) that contrary to what has been documented for pathogenic microorganisms, it has been challenging to reduce populations of Botrytis cinerea using treatments with low concentrations of ClO 2 and ii) that despite Spotts et al and Roberts et al agreement on the concentration of the effective treatment (5 mg/L), the difference in exposure times (1 versus 10 min) implies that the biological subject where Botrytis cinerea is present has an effect on the efficacy of ClO 2 treatments. Strawberries are a unique fruit with irregular shape, seed-studded surfaces, and high organic acid content (Han, Selby, Schultze, Nelson, & Linton, 2004;Kallio, Hakala, Pelkkikangas, & Lapveteläinen, 2000). Moreover, their shelf life is short due to susceptibility to rotcausing pathogens and fast ripening due to high respiration rates (Kim, Kim, Lim, Jang, & Song, 2010).…”