Getting Alcohol Content Right: The Compositional and Sensory Basis for the Alcohol Sweetspot
| dc.contributor.advisor | Wilkinson, Kerry | |
| dc.contributor.advisor | Jeffery, David | |
| dc.contributor.advisor | Stockdale, Vanessa | |
| dc.contributor.author | Pham, Duc-Truc | |
| dc.contributor.school | School of Agriculture, Food and Wine | en |
| dc.date.issued | 2020 | |
| dc.description.abstract | The alcohol content of wine has been steadily increasing due to both climate change and improvements to viticultural management practices and winemaking techniques. Wines containing high alcohol levels tend to exhibit increased hotness, a characteristic considered to negatively impact wine quality. Winemakers are therefore managing their wine alcohol levels, using various methods. The objectives of this research included: (i) determination of the compositional and sensory changes resulting from partial dealcoholisation of wine using reverse osmosis–evaporative perstraction (RO-EP); and (ii) optimisation of the ethanol content for reduced alcohol wine (RAW), i.e. a study into the alcohol ‘sweetspot’ phenomenon. The thesis comprises an introduction, 3 manuscripts describing experimental work completed, and a conclusion, including limitations and future work. Chapter 1 comprises a literature review outlining: the different approaches available for ethanol reduction of wine, together with their relative advantages and disadvantages; the chemical and sensory consequences of removing ethanol from wine; and previous investigations into the wine alcohol ‘sweetspot’ phenomenon. Chapter 2, published in Molecules, is titled: Compositional consequences of partial dealcoholization of red wine by reverse osmosis–evaporative perstraction. This study investigated compositional changes in red wines resulting from ethanol removal by reverse osmosis-evaporative perstraction (RO-EP), and provides insight into the physical and chemical changes to RAW. Trial 1 involved RO-EP treatment of three wines analysed pre-treatment, post-treatment, and post-treatment with alcohol adjustment (i.e. addition of ethanol to the original alcohol content). Trial 2 involved partial dealcoholisation of two wines and analysis of samples collected before, during and after RO-EP treatment. RAWs were slightly more concentrated than pre-treatment wines, which resulted in greater colour intensity, and increased phenolics and organic acids. However, partial dealcoholisation resulted in lower concentrations of some fermentation volatiles, particularly ethyl esters, which may reflect ester hydrolysis following ethanol removal. Chapter 3, submitted to Foods, is titled: Investigating alcohol sweetspot phenomena in reduced alcohol red wines. In this study, different methods of presenting wine samples (ordered vs. randomised, and linear vs. circular) were employed to determine to what extent presentation order influences the outcome of alcohol sweetspotting trials. Two different statistical analyses, i.e. chi-square goodness of fit vs. one proportion tests, were also evaluated. Statistical analyses confirmed alcohol sweetspots were apparent in some evaluations, but outcomes were not reproducible (by panel or by individual panellist). One proportion tests improved the likelihood of identifying statistically significant differences between RAWs, but variation in individuals’ sensitivity prevented validation of the alcohol sweetspot phenomenon. Chapter 4, prepared for submission to Foods, is titled: Influence of partial dealcoholization on the composition and sensory properties of Cabernet Sauvignon wines. This study investigated changes in the chemical and sensory profiles of five Cabernet Sauvignon wines following partial dealcoholisation by RO-EP. Descriptive analysis of wine indicated dealcoholisation did not strongly affect aroma and flavour, consistent with the small changes observed in wine composition. However, significant difference were observed for several palate attributes, with dealcoholised wines found to exhibit lower acidity, sweetness, bitterness, saltiness and/or body. A novel approach to alcohol sweetspotting trials was also investigated, but evidence is still needed to validate any alcohol sweetspot phenomenon. | en |
| dc.description.dissertation | Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2020 | en |
| dc.identifier.uri | http://hdl.handle.net/2440/127011 | |
| dc.language.iso | en | en |
| dc.provenance | This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exceptions. If you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at: http://www.adelaide.edu.au/legals | en |
| dc.subject | Alcohol | en |
| dc.subject | evaporative perstraction | en |
| dc.subject | dealcoholization | en |
| dc.subject | reduced alcohol wine | en |
| dc.subject | reverse osmosis | en |
| dc.subject | sensory | en |
| dc.title | Getting Alcohol Content Right: The Compositional and Sensory Basis for the Alcohol Sweetspot | en |
| dc.type | Thesis | en |
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