Yeast interaction in New Zealand Sauvignon Blanc

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dc.contributor.advisor Goddard, M en
dc.contributor.advisor Gardner, R en
dc.contributor.advisor Villas-Bôas, S en
dc.contributor.advisor Nicolau, L en Prakash, Sushma en 2013-08-25T22:07:41Z en 2013 en
dc.identifier.uri en
dc.description.abstract Interaction between fermenting yeast has a major impact on the aroma of wine. This thesis investigates the interaction of different fermenting yeast in New Zealand Sauvignon Blanc and their impact on the key aromas in the resulting wine. Volatile thiols 3‐mercaptohexanol (3MH) and 3‐ mercaptohexyl acetate (3MHA), reminiscent of tropical aromas like passionfruit and grapefruit have been identified as key aroma compounds in New Zealand Sauvignon Blanc. Yeast interactions were monitored via change in population dynamics, fermentation kinetics, aroma concentration and change in protein and metabolite profiles of un-inoculated or controlled ferments. In-depth analyses of population dynamics of the yeast involved in the 2008 Kumeu River Sauvignon Blanc led to the identification of 11 non-commercial species, of which S. bayanus was found to be the dominant fermenting yeast. A high level of thiol 4-mercapto-4-methylpentan-2-one (4MMP) was identified in this wine, this is a characteristic of Sauvignon Blanc made using S. bayanus isolates. A temperature limited growth model was able to predict the early dominance of the cryotolerant S. bayanus isolates. In order to identify potential yeast interactions which produced unique aroma characters in New Zealand Sauvignon Blanc, a full factorial experiment was designed. This experiment consisted of a range of temperature and nitrogen conditions at which New Zealand Sauvignon Blanc fermentation was carried out by S. bayanus (SBJ1d) isolate and its co-ferments with T. delbrueckii, P. anomala and P. kluyveri (PKKR1) or S. cerevisiae (VL3) and its co-ferment with P. kluyveri (PKKR1). The selected Kumeu River S. bayanus isolate SBJ1d had a high fermentation rate compared to S. cerevisiae (VL3) and was not perturbed by the presence of non-Saccharomyces yeasts. Aroma analyses from ferments showed that S. bayanus (SBJ1d) was capable of producing significantly more varietal thiols 3MH and 4MMP along with 2-phenyl ethyl ethanol (PEE) and beta-phenyl ethyl acetate (BPEA) compared to S. cerevisiae (VL3) potentially influencing floral aroma in New Zealand Sauvignon Blanc. On comparison of S. bayanus (SBJ1d) ferments with co-ferments, it was shown that presence of non-Saccharomyces yeast further enhanced the varietal aroma of the resulting New Zealand Sauvignon Blanc. Concentrations of isobutanol, isoamyl alcohol, isoamyl acetate and 4MMP were found to be greater (two-fold higher) in co-ferments of SBJ1d compared to S. bayanus (SBJ1d)-only ferments at low temperature. Thus, potential interactions between S. bayanus (SBJ1d) and selected isolates of P. kluyveri (PKKR1), T. delbrueckii and P. anomala have been identified which are capable of influencing aroma in New Zealand Sauvignon Blanc. Systems biology approach was used in understanding the biochemical pathways involved in the interaction between S. cerevisiae (VL3) and P. kluyveri (PKKR1) in co-ferment of Sauvignon Blanc. Mono and co-ferments of New Zealand Sauvignon Blanc by these yeasts were analysed using 8-plex iTRAQ proteomic and extracellular metabolomic techniques. Analyses of extracellular metabolomics yielded in the identification of Leucine, Isoleucine and Glutamic acid as potential biomarkers and 34 different metabolic pathways as being important in distinguishing between S. cerevisiae (VL3)–only ferment and co-ferment. However, proteomic analyses using iTRAQ methodology was unable to identify key proteins or protein pathways important in the interaction between these two yeasts. Both the ‘omics approaches had their limitations when analysing a large-scale data-set. However, controlled co-fermentation coupled with targeted metabolomic analyses is a viable option to delineate yeast species interaction during fermentation. en
dc.publisher ResearchSpace@Auckland en
dc.relation.ispartof PhD Thesis - University of Auckland en
dc.relation.isreferencedby UoA99245361814002091 en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. Previously published items are made available in accordance with the copyright policy of the publisher. en
dc.rights.uri en
dc.title Yeast interaction in New Zealand Sauvignon Blanc en
dc.type Thesis en Biological Sciences en The University of Auckland en Doctoral en PhD en
dc.rights.holder Copyright: The Author en
pubs.elements-id 405881 en
pubs.record-created-at-source-date 2013-08-26 en

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