1 U.S. Horticultural Research Laboratory, USDA, ARS, 2001 S. Rock Road, Fort Pierce, FL 34945; and Indian River Research and Education Center, University of Florida, 2199 S. Rock Rd Ft. Pierce, FL 34845
2 U.S. Horticultural Research Laboratory, USDA, ARS, 2001 S. Rock Road, Fort Pierce, FL 34945
3 34945Indian River Research and Education Center, University of Florida, 2199 S. Rock Road, Ft. Pierce, FL 34845
4 Worrell Water Technologies, LLC, 4004 Hunterstand Court, Charlottesville, VA 22911
5 U.S. Horticultural Research Laboratory, USDA, ARS, 2001 S. Rock Road, Fort Pierce, FL 34945
The effect of controlled-release chlorine dioxide (ClO2) gas on the safety and quality of grapefruit was studied. The experiments were run under controlled chamber systems with inoculated fruit, and in boxed fruit under commercial conditions. For the inoculation test, fruit artificially inoculated with either Escherichia coli or Penicillium digitatum, or naturally inoculated Xanthomonas citri ssp. citri (Xcc) (fruits with citrus canker lesions), were incubated in a chamber containing a dose equivalent to 0–60 mg·L−1 of pure ClO2 as an antimicrobial agent. After 24 hours, the microbial population on treated grapefruit was significantly reduced compared with that of control fruit: a dosage of 5 mg·L−1 completely inhibit the growth of E. coli and P. digitatum, but a dosage of 60 mg·L−1 was needed to completely kill Xcc. For the simulated commercial experiment, fruit were harvested in late Oct. 2015 passed through a commercial packing line, and packed in 29 L citrus boxes. ClO2 packets were attached to the top lids with the following five treatments: fast-release, slow-release, slow/fast-release combination (each containing 14.5 mg·L−1 of pure ClO2), double dose fast-release (containing 29 mg·L−1 of ClO2), and control. After 6 weeks of storage at 10 °C (to simulate storage and transportation) + 1 week of storage at 20 °C (to simulate retail marketing), the fruit quality was evaluated. The slow-release treatment at standard dose exhibited the best antimicrobial activity, reducing total aerobic bacterial count and yeast/mold count by 0.95 and 0.94 log colony-forming units (cfu)/g of fruit, respectively, and maintained the best visual, sensory, and overall quality. However, the higher dosage treatments resulted in phytotoxicity as evidenced by peel browning.
This paper is based on a presentation given during the 2016 Annual Meeting of the Florida State Horticultural Society, which was held June 12–14, 2016, in Stuart, FL.
We would like to thank the financial support provided by Worrell Water Technologies. Mention of a trademark or proprietary product is for identification only and does not imply a guarantee or warranty of the product by the U.S. Department of Agriculture. The U.S. Department of Agriculture prohibits discrimination in all its programs and activities on the basis of race, color, national origin, gender, religion, age, disability, political beliefs, sexual orientation, and marital or family status.
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