Location: Commodity Protection and Quality Research
Project Number: 2034-43000-043-073-I
Project Type: Interagency Reimbursable Agreement
Start Date: Jun 1, 2024
End Date: Sep 30, 2024
Objective:
The overall goal of this project is to develop postharvest treatments with ethyl formate so that pest-free and high-quality California walnuts are exported to key markets using practices that are consistent with consumer and regulatory demands for no hazardous residues. Data is required to support phytosanitary and residue tolerances.
The goal of this research is to develop ethyl formate as a short-duration methyl bromide alternative for the California walnut industry that is consistent with consumer and regulatory demands for favorable residue chemistry, while still guaranteeing food security and safety. We hypothesize that ethyl formate can be used as a replacement for propylene oxide, 1) as a “standalone” Pasteurization agent applied in vacuo as well as 2) in a blend with sulfuryl fluoride in vacuo as well as at normal atmospheric pressures (NAP) (i.e., ambient pressure). Parameters for the Pasteurization approach are guided based on “5 log kill-level” of key pathogens, conditions that also control insects. The parameters for the two insect approaches, both in vacuo and NAP, are guided by “Probit 9-level” insect control, with the subsequent quantification of resulting/ peripheral “log kill-level” toward pathogens.
Approach:
Research will be conducted in phases as described below.
Phase I (Year 1)
In phase I of the project (year 1 – 2023), ARS investigators will use already established insect colonies to establish exposure-mortality relationship between ethyl formate and insect pests for both vacuum and normal atmospheric pressure fumigations, with and without sulfuryl fluoride, at the laboratory /pilot scale. The ARS will also develop and validate analytical methods for ethyl formate and its degradates (ethanol and formic acid) on walnuts (tree nut group) using mass labeled ethyl formate at levels relevant to vacuum and normal atmospheric pressure (NAP) fumigations. Cooperators will develop and validate methodology for inoculation and enumeration of all relevant microbial organisms (human pathogen, yeast, mold, and surrogates).
Phase II (Year 2)
In phase II (year 2 – 2024) cooperators will establish exposure-mortality relationship between ethyl formate and target microbiological organisms: mold, human pathogen as well as potential surrogates (up to 3) for both vacuum and normal atmospheric pressure fumigations. These results will be used by ARS to conduct commercial scale fumigations, using both schedules already determined to be effective against insect pests and “Pasteurization” fumigation schedules determined to be effective against pathogens of concern: Salmonella, Listeria, generic E. coli. The commercial fumigations will take place at both vacuum and normal atmospheric pressure. Cooperators will determine microbial efficacy, and the ARS will determine insect efficacy and all associated residues. Quantified residues associated with the commercial trials will be prepared for data submission to USEPA, California, and CODEX.
Phase III (Year 3)
In phase III, ARS will conduct research related to the off gassing of ethyl formate as related to applicator, worker, and by stander exposures, including research to scrub ethyl formate following postharvest fumigations in both scenarios, vacuum and NAP, to target insects and pathogens. ARS will also present findings in written research reports and industry guidelines and/or as requested and provide to industry, USDA-APHIS, USDA-TASC, and foreign counterparts and transfer research results to industry for consideration.
