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Title: PATTERNS OF SULFITE RESIDUE PERSISTENCE IN SEEDLESS GRAPES DURING THREE MONTHS OF REPEATED SULFUR DIOXIDE FUMIGATION

Author
item Austin, Rodney
item CLAY, WILLENA - CALIF STATE UNIV, FRESNO
item PHIMPHIVONG, SAMRANE - CALIF STATE UNIV, FRESNO
item Smilanick, Joseph
item HENSON, DELMER - USDA, ARS, HCRL

Submitted to: American Journal Of Enology And Viticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/25/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: California table grapes are fumigated with sulfur dioxide weekly for several months to retard the growth of gray mold Botrytis fungus. The U.S. Environmental Protection Agency (EPA) has established a permissible level of 10 ppm sulfite residue for fresh grapes. Treatment of Thompson Seedless grapes with sulfur dioxide in storage for up to 14 weeks left sulfite residues well below the legal level. These studies helped producers to maintain grape quality and consumers to use the produce safely.

Technical Abstract: In 1989, the United States Environmental Protection Agency instituted a sulfite tolerance of 10 ug SO2 per gram in grapes (Vitis vinifera L.). Therefore, it is essential to ascertain that the residues resulting from repeated weekly SO2 fumigations of table grapes in storage do not exceed the legal limit. Thompson Seedless grapes were fumigated once a week with 2000 or 5000 uL SO2 per liter of storage volume and aerated 30 min while stored at 0C for at least 14 consecutive weeks. Weekly sampling of grapes for sulfite residue showed 1.8 (2000 uL/L) and 2.5 (5000 uL/L) ug/g. Post-fumigation storage temperature of 0, 10, 20 or 30C for 24 hr did not significantly affect residue levels. The data provided assurance that SO2 fumigation at recommended dosage gave sulfite residues in grapes well below the official legal limit.