Graduate Thesis Or Dissertation

 

Mesurol (methiocarb) residues in grapes and wine and their possible effects on fermentation and wine quality Public Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/5m60qv099

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  • Wines were made from Pinot Noir and White Riesling grapes which had received field application rates of 2 and 4 lb./acre of the experimental bird repellent Mesurol (methiocarb or 3, 5 dimethyl- 4(methylthio)phenylmethylcarbamate). In addition, Pinot Noir must and press juice and White Riesling press juice were fortified with 15 ppm Mesurol (active ingredient) and vinified. Mesurol and its sulfoxide and sulfone metabolites were determined by gas chromstographic analysis as mesylate derivatives following fractionation on Florisil. Residues were also oxidized to and expressed as total sulfone. Mesurol residues, methiocarb and total sulfone, in field treated grapes sprayed with 4 lb./acre Mesurol exceeded the 15 ppm temporary tolerance established by the Environmental Protection Agency. Methiocarb residues in pomace, calculated on a dry weight basis, obtained from grapes harvested one day after the final application of Mesurol were in excess of the 75 ppm EPA temporary tolerance. Approximately 40 to 51% of the methiocarb residues measured in field, treated grapes remained associated with the pomace after pressing. Finished Pinot Noir and White Riesling wine, prior to bottling, contained in the order of 3-8 ppm representing 34 to 49% and. 13%, respectively, of the methiocarb residues originally present in grapes. The fate of Mesurol sulfide, sulfoxide and sulfone residues during the processing of Mesurol fortified White Reisling press juice was investigated. Settling of press juice was found to reduce methiocarb residues. Oxidation during vinification was minimal. Mesurol sulfide, sulfoxide, and sulfone residues in finished wine remained unchanged after 12 months of storage at cellar temperatures. Trace amounts of Mesurol sulfide phenol were detected with Mass Spectrometry. Volclay bentonite (KWK) fining at 4 and 8 lb./1000 gal. and membrane filtration (0.45 μ) were not effective in reducing Mesurol residues in wine. Reference-difference tests were used to evaluate the effect of Mesurol on finished wine sensory qualities. The sensory properties of wines made from grapes harvested seven days after the last application of Mesurol and Mesurol Fortified must and juices were not affected. Also, the chemical composition of these wines was not altered. Lag time and fermentation rate of Mesurol Fortified. Pinot Noir must and juice processed into wine were not affected. The course of fermentation in the presence of Mesurol was also monitored by recording mass loss in model studies. A slight inhibition in fermentation rate was observed, at levels below 25 ppm while a stimulation was evident at concentrations of up to 500 ppm.
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