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Study of new yeast strains as novel starter cultures for Riesling icewine production

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dc.contributor.author Yang, Fei
dc.date.accessioned 2011-10-14T15:22:18Z
dc.date.available 2011-10-14T15:22:18Z
dc.date.issued 2011-10-14
dc.identifier.uri http://hdl.handle.net/10464/3423
dc.description.abstract Icewine is a sweet dessert wine fermented from the juice of grapes naturally frozen on the vine. The production of Icewine faces many challenges such as sluggish fermentation, which often yields wines with low ethanol, and an accumulation of high concentration of volatile acidity, mainly in the form of acetic acid. This project investigated three new yeast strains as novel starter cultures for Icewine fermentation with particular emphasis on reducing acetic acid production: a naturally occurring strain of S. bayanus/S. pastorianus isolated from Icewine grapes, and two hybrids between S. cerevisiae and S. bayanus, AWRI 1571 and AWRI 1572. These strains were evaluated for sugar consumption patterns and metabolic production of ethanol, glycerol and acetic acid, and were compared to the performance of a standard commercial wine yeast KI-VI116. The ITS rONA region of the two A WRI crosses was also analyzed during fermentations to assess their genomic stability. Icewine fermentations were performed in sterile filtered juice, in the absence of indigenous microflora, and also in unfiltered juice in order to mirror commercial wine making practices. The hybrid A WRI 1572 was found to be a promising candidate as a novel starter culture for Icewine production. I t produced 10.3 % v/v of ethanol in sterile Riesling Icewine fermentations and 11.2 % v/v in the unfiltered ones within a reasonable fermentation time (39 days). Its acetic acid production per gram sugar consumed was approximately 30% lower in comparison with commercial wine yeast K I -V 1116 under both sterile filtered and unfiltered fermentations. The natural isolate S. bayanus/S. pastorianus and AWRI 1571 did not appear to be suitable for commercial Icewine production. They reached the target ethanol concentration of approximately 10 % v/v in 39 day fermentations and also produced less acetic acid as a function of both time and sugar consumed in sterile fermentations compared to KI-V1116. However, in unfiltered fermentations, both of them failed to produce the target concentration of ethanol and accumulated high concentration of acetic acid. Both A WRI crosses displayed higher loss of or reduced copies in ITS rDNA region from the S. bayanus parent compared to the S. cerevisiae parent; however, these genomic losses could not be related to the metabolic profile. en_US
dc.language.iso eng en_US
dc.publisher Brock University en_US
dc.subject Wine and wine making en_US
dc.subject Fermentation en_US
dc.subject Riesling (Wine) en_US
dc.title Study of new yeast strains as novel starter cultures for Riesling icewine production en_US
dc.type Electronic Thesis or Dissertation en_US
dc.degree.name M.Sc. Biotechnology en_US
dc.degree.level Masters en_US
dc.contributor.department Centre for Biotechnology en_US
dc.degree.discipline Faculty of Mathematics and Science en_US


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