Continuous Low-level Chlorine Dioxide Gas Exposure and Curing Treatment on Sweet Potato Spoilage during Storage: A Pilot Study under Practical Warehouse Conditions

Abstract

Background: Postharvest losses of sweet potatoes remain substantial due to microbial spoilage and suboptimal storage conditions, with curing commonly used to enhance wound healing and reduce decay. Aims: This pilot study compared spoilage incidence of sweet potatoes (Ipomoea batatas cv. 'Beniharuka') stored under continuous low-level chlorine dioxide (ClO2) gas exposure with and without curing treatment. Study Design: A two-by-two treatment arrangement in a single non-replicated pilot trial. ClO2-exposed and non-exposed sweet potatoes were stored in separate warehouse compartments, with cured and non-cured lots placed within each compartment. Place and Duration of Study: Two agricultural warehouses in Ibaraki Prefecture, Japan, from 12 December 2024 to 24 January 2025. Methodology: A total of 507 tubers (80 kg) were allocated to four groups according to the presence or absence of ClO2 exposure (mean concentration 0.039 ppm for the first 14 days; reduced thereafter due to equipment malfunction) and curing (40 °C, 100% RH, 90 h). Temperature, relative humidity, and ClO2 concentration were monitored continuously. Spoilage was assessed weekly by visual inspection and palpation, and risk ratios (RR) with 95% confidence intervals were calculated using Fisher's exact test. Results: During weeks 3–6, spoilage incidence was lower in the ClO2 exposure group than in the non-exposure group (12/236 vs 58/235; RR = 0.206, 95% CI 0.114–0.373, P < .001), whereas curing was associated with higher spoilage incidence (48/253 vs 22/218; RR = 1.88, 95% CI 1.17–3.01, P = .009). However, the ClO2 compartment was operated at lower temperature (−1.9 °C) and relative humidity (−18.5 percentage points) than the control; therefore, the observed reduction cannot be attributed to ClO2 exposure alone. Conclusion: In this single pilot warehouse trial, continuous low-level ClO2 exposure at concentrations below the OSHA occupational exposure limit (TWA 0.10 ppm) was associated with reduced sweet potato spoilage. Because environmental conditions differed between compartments, further trials under controlled conditions are needed to isolate the effect of ClO2 from that of temperature and humidity.