The consequences of pre-fermentation and post-fermentation extended maceration (EM) on colour, mouthfeel and phenolic composition were investigated in Pinot noir (2004), Grenache (2006) and Shiraz (2007) (Vitis vinifera L.) wines. Experimental wines were made using cold soak, post-fermentation EM, and standard fermentation treatments (C). Cold soak treatments included a 3-day cold soak at 10°C (CS), with an additional comparison of plunging effects for the 2004 wines (CSP). Post-fermentation extended maceration treatments were 1- or 3-weeks on skins in 2004 (PS1 and PS3 respectively), and 3-weeks in 2006 and 2007 (PS3). A variety of chemical and sensory test methods were used to determine changes in phenolic components and organoleptic properties between treatments of all 3 varietals as they aged in the bottle. Among other results, it was determined if wines made with a period of cold soak had increased colour intensity, and increased concentrations of monomeric anthocyanins and pigmented polymers compared to control wines. It was also determined if wines made with a period of post-fermentation EM had increased concentrations of the flavan-3-ols (+)-catechin and (−)-epicatechin, and tannin, decreased colour intensity and modified mouthfeel compared to the other wine treatments. A greater understanding of Australian red winemakers’ opinions on EM regimes and their use in Australian wineries was obtained by survey. Survey results confirmed that EM is used extensively in Australian wineries but that winemakers have poor understanding of the consequences of EM regimes for red wine properties. The survey confirmed that winemakers are concerned about the economic cost and logistic pressures associated with the use of EM regimes during vintage. Wines made using EM need to spend longer in fermentation vessels, which are in high demand during this time. Findings from this study provide winemakers with more information to consider before making decisions about their use of EM regimes. Survey findings showed more winemakers would use EM regimes if logistic and economic pressures did not apply. However, results suggest that even if winemakers did adopt EM practices, some may not achieve what they believe to be the outcome of these regimes, such as improved colour or mouthfeel properties. For instance, results showed that cold soaking did not make a difference to wine colour compared to conventional fermentation maceration. Even without cold soaking red must, winemakers may be able to achieve the same or very similar wine organoleptic characteristics at a reduced cost. Similarly, no significant effects of plunging during cold soak were observed. Post-fermentation EM visibly reduced wine colour intensity and imparted a browner hue to the wine compared to red wine that was pressed off skins upon reaching dryness. This EM regime is therefore unlikely to benefit winemakers who are seeking to produce highly coloured wines. However, prolonged maceration post-fermentation did increase the intensity of perceived bitterness and increased the concentration of wine flavan-3-ols and tannins. Winemakers may therefore influence the desired balance between the extraction of these wine phenolics (and the associated outcome for taste and mouthfeel properties) and economic considerations by varying the duration of maceration post-fermentation. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1362928 / Thesis (Ph.D.) - University of Adelaide, School of Agriculture, Food and Wine, 2009.
| Identifer | oai:union.ndltd.org:ADTP/269184 |
| Date | January 2009 |
| Creators | Joscelyne, Venetia Louise |
| Source Sets | Australiasian Digital Theses Program |
| Detected Language | English |
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