Antimicrobial activity of gaseous chlorine dioxide against Aspergillus flavus on green coffee beans

The aim of this study was to use chlorine dioxide (ClO₂) gas to inactivate Aspergillus flavus on green coffee beans. Green coffee beans inoculated with A. flavus were exposed to ClO₂ gas generated from 0.75, 1, 1.25, or 1.5 mL of ClO₂ solution in a sealed container at 25 or 50 °C (100% relative humidity [RH]) for up to 10 h. Numbers of A. flavus on beans treated at 25 °C decreased by 1.1-2.2 log cfu/bean within 1 h of exposure to ClO₂ and decreased to below the detection limit (≤1.0 log cfu/bean) at all ClO₂ concentrations after 10 h. At 50 °C, the microbial population reached the detection limit within 0.5 h regardless of the ClO₂ solution concentration. Beans exposed to gas for 10 h at 25 °C were stored for 14 days under conditions of 43, 75, or 100% RH and 4, 12, or 25 °C. At 4 °C, visible mold growth was not established regardless of RH. After 12 days, mold was observed only at 25 °C. At 100% RH, beans stored under the same conditions without ClO₂ gas treatment showed mold formation at 13 and 4 days at 12 and 25 °C, respectively.