Investigation into the Aroma Stability of New Zealand Sauvignon blanc

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dc.contributor.advisor Kilmartin, P en
dc.contributor.advisor Nicolau, L en
dc.contributor.author Herbst-Johnstone, M en
dc.date.accessioned 2010-11-25T00:17:40Z en
dc.date.issued 2010 en
dc.identifier.uri http://hdl.handle.net/2292/6077 en
dc.description.abstract The unique passion fruit-type aroma of New Zealand Sauvignon blanc wines, which has been attributed to the varietal thiols 3-mercaptohexan-1-ol (3-MH) and 3-mercaptohexan-1-ol acetate (3-MHA), is known to diminish rapidly over a period of just a year in the bottle. Therefore, it is important to improve the shelf-life of these wines in order to maintain New Zealand’s position as a market leader for Sauvignon blanc. The loss of varietal thiols has been linked to polyphenol oxidation, catalysed by metals, a process which can be inhibited by antioxidants, such as sulfur dioxide (SO2), ascorbic acid, and glutathione. The evolution of 3-MH and 3-MHA has been monitored in New Zealand Sauvignon blanc wines with regards to polyphenol content and antioxidants over time under various storage conditions, such as closure type, temperature, and headspace composition. Accelerated stability testing in a model white wine matrix as well as in a Sauvignon blanc matrix was employed to study the influence of ‘pro-oxidants’ (metals and polyphenols), ‘anti-oxidants’ (SO2, ascorbic acid, and glutathione) as well as temperature and pH on the reaction kinetics of 3-MH and 3-MHA, thereby uncovering the mechanism(s) responsible for the loss of the varietal New Zealand Sauvignon blanc aroma. 3-MHA is the least stable of the varietal thiols, declining steadily with time and largely unaffected by the presence of antioxidants, whereas 3-MH decreased more slowly following an initial increase due to hydrolysis of 3-MHA to 3-MH. Antioxidants are capable of attenuating the polyphenol-mediated oxidative degradation of 3-MH to a greater extent than 3-MHA, by scavenging oxygen and/or via interacting with polyphenol autoxidation products, namely ortho-quinones and hydrogen peroxide, which are both detrimental to varietal thiol stability. Evidence was provided for the role of copper as a mediator of oxidative processes. This research project has been fundamental in identifying the importance of temperature, rather than antioxidants, in maintaining high concentrations of 3-MHA over time. 3-MHA also has a lower perception threshold than 3-MH (4 versus 60 ng/L), and can be found at particularly high concentrations in New Zealand Sauvignon blanc wines. These results suggest that the acid-catalysed hydrolysis of 3-MHA to 3-MH is the key mechanism responsible for the disappearance of the distinctive passion fruit-type aroma from New Zealand Sauvignon blanc wines. en
dc.publisher ResearchSpace@Auckland en
dc.relation.ispartof PhD Thesis - University of Auckland en
dc.relation.isreferencedby UoA99206943014002091 en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. en
dc.rights.uri https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm en
dc.rights.uri http://creativecommons.org/licenses/by-nc-sa/3.0/nz/ en
dc.title Investigation into the Aroma Stability of New Zealand Sauvignon blanc en
dc.type Thesis en
thesis.degree.discipline Chemistry en
thesis.degree.grantor The University of Auckland en
thesis.degree.level Doctoral en
thesis.degree.name PhD en
dc.rights.holder Copyright: The author en
pubs.elements-id 183294 en
pubs.record-created-at-source-date 2010-11-25 en


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