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ARS Home » Pacific West Area » Parlier, California » San Joaquin Valley Agricultural Sciences Center » Commodity Protection and Quality Research » Research » Research Project #432665

Research Project: Sorption and Depuration of Sulfur Dioxide Following Fumigation of California Table Grapes

Location: Commodity Protection and Quality Research

Project Number: 2034-43000-040-43-T
Project Type: Trust Fund Cooperative Agreement

Start Date: May 1, 2017
End Date: May 1, 2019

Objective:
The goal of this project is to obtain data on the sorption and depuration of sulfur dioxide from table grapes and packaging materials based on operational/logistical considerations specific to marketing practices in California as well as the current label parameters.

Approach:
The first year of the project is planned in three phases, each with a sub objective. Results of this research will be used by industry to support the USEPA reregistration of sulfur dioxide (SO2) use on table grapes. Phase 1 involves establishing kinetic constants associated with sulfur dioxide sorption to grapes, as well as depuration from grapes, per the “Initial Fumigation” label scenario 1) 10,000 parts per million volume (ppmv) (1% volume to volume ratio (v/v)) sulfur dioxide for 30 minutes (min) at 60, 45, and 32 Fahrenheit (F) with post-fumigation aeration for 30 min. Phase 2 involves establishing kinetic constants associated with sulfur dioxide sorption to grapes, as well as depuration from grapes, per “High Frequency – Low Dosage” “Maintenance Fumigation” label scenario 2) 400 ppmv (0.04% v/v) sulfur dioxide at 32F. Phase 3 involves establishing kinetic constants associated with sulfur dioxide sorption to grapes, as well as depuration from grapes, per the proposed “Total Utilization” “Maintenance Fumigation” label scenario 3) 5,000 ppmv (0.5% v/v) SO2 at 32F. Fumigation will continue until the SO2 level in room headspace is = 2.0 ppmv. ARS will work with industry to then transfer results to U.S. Environmental Protection Agency (USEPA).