Thesis (M.Sc.)(Chemistry))--University of Pretoria, 2009. / Summary in English. Includes bibliographical references (leaves 132-159)

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Thesis (MSc)--Stellenbosch University, 1982. / ENGLISH ABSTRACT: No abstract available / AFRIKAANSE OPSOMMING: Geen opsommong beskikbaar

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. / Graduation date: 1981

This study was conducted to evaluate the influence of maturity, mold contamination and variety on the color quality of strawberry wines. Indices for acceptability were determined using instrumental measurements and sensory analysis. Compositional analyses were done on the fully ripe and overripe Benton and Totem strawberries. Included were anthocyanin content, flavanols, leucoanthocyanins, total phenolics, non-flavonoid phenolics, ascorbic acid, soluble solids, titratable acidity and pH. The Totem variety contained more anthocyanins, flavanols, ascorbic acid, leucoanthocyanins, and was slightly higher in pH than the Benton variety. Likewise, the overripe fruit contained more anthocyanins, flavanols, leucoanthocyanins, total phenolics and was higher in pH than the fully ripe fruit. Polyphenoloxidase and β-Glucosidase activities were assayed. Polyphenoloxidase activity was higher in the Benton and in the fully ripe berries. β-Glucosidase activity was extremely low for all the samples. Six batches of wine were made from the Benton fully ripe, Benton overripe, Benton fully ripe spiked with moldy Bentons, Totem fully ripe, Totem overripe and Totem fully ripe spiked with moldy Totems. Howard Mold Counts were determined on the crushed strawberries and on the strawberry juice. Color parameters were measured on the juice and on the finished wines which includes color density, polymeric color, % polymeric color, browning index and anthocyanin content. Hunter "L," "a" and "b" values and % haze were also measured. Changes in these color parameters of the wines were monitored weekly for a period of 6 weeks. Samples were stored in the dark at 25°C. A sensory analysis, mainly evaluating the color quality of the wines after storage based on color intensity, hue, browning, clarity and over-all color and appearance, was conducted. One-way ANOVA analyses showed significant differences between the two varieties, the two levels of maturity and the mold-contaminated wines. Multiple correlation data showed that anthocyanin content of the wine and Hunter "L" are highly correlated with all of the sensory indices for color, hence, are good predictors of color acceptability. Total phenolics, non-flavonoid phenolics and soluble solids are highly correlated to color density, polymeric color, browning index and Hunter "a" values of the wines. Likewise, anthocyanin content, flavanols, leucoanthocyanins, titratable acidity and pH are highly correlated to overall color and appearance, color intensity and hue. Polyphenoloxidase also showed high correlation with overall color and appearance, color intensity and browning. / Graduation date: 1983

The development of whey beverages including whey wine has been an area of whey utilization research. One study to produce a commercially salable wine from sweet whey, particularly cheddar whey, was undertaken. It included developing a process to clarify the naturally cloudy wine, monitoring the physical and chemical changes which occurred during the wine making process, comparing the sensory differences in the unclarified and clarified wine, and incorporating the wine sediment in a food product. The criteria for the clarification process were simplicity, legality, reasonable cost, minimal usage of energy and equipment, and maintenance of the wine character and quality. Existing procedures for clarifying grape wine such as filtration, centrifugation, and the addition of fining agents, casein, Cold Mix Sparkolloid, gelatin, tannin, and bentonite were investigated. Also investigated were techniques used to separate the proteins from whey; specifically pH adjustment (with potassium carbonate) and precipitation (with sodium hexametaphosphate). It was found that the most feasible clarification procedure was the addition of 0.20-0.50 percent bentonite on a dry weight basis followed by a polishing filtration. Determinations for lactose, protein, fat, ash, and total solids and tests for Brix, pH, titratable acidity, and alcohol content were performed to monitor the effects of fermentation, aging, and clarification. The changes noted during fermentation and aging were primarily due to alcoholic and lactic acid fermentations. Bentonite fining had a dilution effect but did increase the ash content of the wine. Triangular difference tests with blindfolded tasters indicated that there was no significant taste difference between cloudy wine and bentonite-fined and filtered wine. A cursory gas-liquid chromatographic analysis revealed only a slight difference in the gross volatile components of unclarified and clarified wines. The wine sediment was dried to a paste and substituted at the five and ten percent levels for nonfat dry milk in a commercial sugar cookie recipe. A preference test showed that the sediment decreased the acceptability because of its "acid" taste. It is likely that the sediment could successfully be utilized in a fermented or cultured dairy product. / Graduation date: 1976

The possible effect of oxidation [processing with or without sulfur dioxide (±S0₂)] and of pre-ultrafiltration treatment of juices with enzymes and fining agents on flux, and on juice color, composition and stability was investigated. White Riesling juice was ultrafiltered with a Romicon system operated with a nominal molecular weight cut-off (MWCO) of 10,000 daltons. In addition, UF White Riesling juices processed ±S0₂, were stored for 2 months (1985 vintage) and 12 months (1984 vintage) at 2°C and 20°C, and evaluated by a trained panel using descriptive analysis. Pre-UF treatment with enzymes and fining increased flux. Sediment formation and instability to heat testing of UF permeates processed -S0₂ was prevented with pre-fining. Up to 99% of protein, 90% of pectin, 84% of color and low variable phenolics were retained by the membrane of 10,000 dalton MWCO. During UF there is a significant increase in the soluble protein and water soluble pectin passing through the membrane with increasing volume concentration ratio (VCR, process time). It is concluded that it is not only the amount but the nature/state of compounds such as proteins, phenolics, pectins, and their interaction that results in instability. UF juices processed with minimum oxidation and stored for 12 months had lower intensity aroma (apple/apple cider, sweet, and honey/caramel) and overall intensity flavor by mouth descriptors than those processed with oxidation. Moreover, juices processed with minimum oxidation and stored for two months (1985 vintage) had significantly lower intensity of apple/apple cider, sweet, honey/caramel aroma descriptors when compared to those processed with oxidation. There was no effect of temperature of storage on any of the aroma and flavor-by-mouth descriptors for the 1985 juice after two months of storage. Only one aroma descriptor (vegetative) was significantly increased for the 1984 White Riesling juice after 12 months at 2°C. This indicates the possibility that UF juices may be stored at higher temperature (20°C) for less cost with minimal changes in aroma and flavor. White Riesling (WR) and Gewurztraminer (GEW) wines were ultrafiltered with Romicon and Millipore pilot-scale systems, respectively. The effect of ultrafiltration (UF), membrane MWCO from 10,000-50,000 daltons, and of VCR on composition and wine stability was investigated. The effect of 1) pilot-scale UF processing and Bentonite fining on WR and GEW wines, and 2) commercial-scale UF processing on GEW wine was sensorially evaluated by a trained panel using descriptive analysis. UF processing significantly reduced color (A [subscript 420nm]), total phenol, protein and heat/cold test (HOT) haze of both WR and GEW wines. Stability to HOT haze formation was obtainable with MWCO of 10,000 daltons, but trace instability can remain. With increasing VCR (process time) there was a significant decrease in membrane retention of color (A [subscript 420nm]), protein, and HCT haze formation in the WR wine and the color (A [subscript 420nm]) of the GEW wine. UF processing of the WR wine significantly decreased the perception of overall aroma intensity, fruity, fresh fruity citrus, floral, sweet and honey/caramel character but it also increased the intensity of the vegetative aroma descriptor when compared to the control unfiltered WR wine. In addition, significant differences were detected for these descriptors between the bentonite-fined WR wine and the ultrafiltered WR wine except for fresh fruity citrus and honey/caramel which were less intense in the ultrafiltered WR ultrafiltered WR wine. UF processing of GEW wine significantly decreased the intensity of fruity, fresh fruity aroma descriptors; and increased the chemical aroma descriptor compared to the control unfiltered GEW wine. However, no significant differences were detected for these descriptors between the bentonite fined GEW wine and the ultrafiltered GEW wine except for fresh fruity which was less intense in the ultrafiltered GEW wine. Commercial processing of GEW wine by UF did not have any significant effect on the aroma and flavor by mouth descriptors evaluated as compared to standard processing procedures. / Graduation date: 1988

Bibliography: p. 145-162. / xi, 162 p. : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Science, 1995

Bibliography: p. 166-189. / xii, 189 p. : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis describes the development and use of stable isotope dilution analysis techniques for measuring wine components associated with oak-barrel maturation and with taint derived from cork closures during bottle maturation. (introduction) / Thesis (Ph.D.)--Adelaide University, Dept. of Horticulture, Viticulture and Oenology, 2001

Bibliography: p. 145-162.