Skip to main content
ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Produce Safety and Microbiology Research » Research » Publications at this Location » Publication #401395

Research Project: Elucidating the Factors that Determine the Ecology of Human Pathogens in Foods

Location: Produce Safety and Microbiology Research

Title: Reduction of Aspergillus flavus and aflatoxin AFB1 on almond kernels using gaseous chlorine dioxide fumigation

item Wu, Vivian
item Lacombe, Alison
item RANE, BHARGAV - Washington State University

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/1/2023
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Introduction: Stockpiling almonds, like any food, requires proper storage and handling to ensure food safety. We utilized ClO2 fumigation technology to develop an effective intervention for mycotoxin molds in almond stockpiles. However, little is known about how gaseous ClO2 reduces the risk of mold contamination. This project investigates the reduction of Aspergillus flavus molds, aflatoxin, and genes that regulate toxin production. Methods: Batch fumigation trials were performed using 500g of almonds in an airtight chamber. ClO2 was generated using equal parts of dry media precursors, and dosing was determined based on a dry weight generation curve. The mixed precursors released gaseous ClO2 at a continuous rate, and gas was circulated using a battery-operated fan. An A. flavus spore suspension (40 ml) was used to dip-inoculate almond kernels prior to fumigation. After treatment, the almonds were sampled for enumerating A. flavus population using potato dextrose agar, and RNA was extracted to determine the relative abundance of gene associated with aflatoxin production . Aflatoxin concentration was analyzed using gas spectrophotometry. Results: A headspace concentration of 0.2 ppm ClO2 demonstrated 87.1% reduction of A. flavus on in-hull almonds. When the headspace concertation was increased to 2.9 ppm, a 99.7% reduction of A. flavus and 80% degradation of aflatoxins was achieved. The gene expression of aflatoxin-producing genes aflR and aflS was downregulated on almond kernels when analyzed after seven days. Cellular aflatoxin production was reduced following gaseous ClO2 exposure, possibly due to the lower relative abundance of the critical toxin-producing genes laeA and lipA. Significance: Currently, gaseous ClO2 can be used as an antimicrobial agent for fumigating raw agricultural commodities in the process of preparing, packaging, or holding food for commercial purposes consistent with the Food Drug and Cosmetic Act section 201(q)(1)(B)(i). The findings of this study can be used as a foundation to conduct more extensive pilot-scale studies allowing gaseous ClO2 to be commercially validated.