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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Produce Safety and Microbiology Research » Research » Research Project #439610

Research Project: Implementation of gaseous chlorine dioxide fumigation to improve post-harvest stockpile management of almonds

Location: Produce Safety and Microbiology Research

Project Number: 2030-42000-055-004-T
Project Type: Trust Fund Cooperative Agreement

Start Date: Feb 1, 2021
End Date: Jan 31, 2026

The objectives of this project are to: 1) Understand phenotypic responses of spoilage microorganisms and mycotoxin-producing Aspergillus flavus on almond to gaseous ClO2 implemented during stockpiling; and 2) Characterize transcriptional changes in foodborne pathogens to better understand potential methods of inactivation and to elucidate microbial stress response mechanisms that facilitate adaptation, survival, and tolerance. Add the following objectives as Phase 2 of the study: Objective 2: Pilot-scale (industrial size stockpile) gaseous ClO2 fumigation treatment against moisture enhanced native microbial flora on in-hull almonds Objective 4: Evaluate engineering controls for optimal ClO2 stockpile fumigation

Aflatoxins are a result of the colonization of almonds by A. flavus molds introduced by insect pests. The almond industry currently uses fumigation methods like sulfuryl fluoride and phosphine on stockpiles to control problems. However, current practices do not address the moisture pockets, may not significantly reduce molds, nor are they safe to be used at high concentrations. Gaseous chlorine dioxide (ClO2) represents a potential solution because it is a non-thermal and waterless antimicrobial that leaves little to no residue behind. It is also intrinsically attracted to moisture pockets, rendering it useful in fumigation processes in which seasonal moisture fluctuations are a concern. We plan to work with Almond Board of California to improve stockpiling practices for practicality and broad industry adoption to minimize negative impact of stockpiling on quality and food safety.