Botrytized wines fermentation

The use of selected yeast starters for botrytized wine fermentation is strongly encouraged in Germany (Dittrich, 1977 Hoersch and Schlotter, 1990), in Sauternes (Dubourdieu, 1999 Ribereau-Gayon et ah, 2000), and is typical in the newer botrytized wines produced in Australia, and South... 

Banszky, L., Ujhelyi, G., Pomazi, A., and Maraz, A. (2003). Population dynamics of Candida stellata during botrytized wine fermentation. Book of Abstracts of the 23rd International Specialised Symposium on Yeasts, Budapest, Hungary, Diamond-Congress Ltd, Budapest, p. 89, Book of Abstracts. 

Sipiczki, M. (2003). Candida zemplinina sp. nov., an osmotolerant and psychrotolerant yeast that ferments sweet botrytized wines. Int. J. Syst. Evol. Microbiol. 53, 2079-2083. 

The aim of this review is to give an insight into the diversity of botrytized wines, the biochemical—physicochemical processes of noble rot, and the vinification process, with special regard to the alcoholic fermentation. The health concerns of botrytized wine consumption are also presented and discussed. 

These results suggest that non-Saccharomyces species may contribute significantly to the fermentation of botrytized wines. C. zemplinina seems not to produce excess volatile compounds nor any specific aroma compounds (Toth-Markus et al., 2002). Its main contribution to the chemical composition might be an increase in glycerol content and in the G F ratio. C. zemplinina and C. stellata have proven to be very fructo-philic yeasts (Mills et al., 2002 Magyar and Toth, 2011 Magyar et al., 2008). 

With a few exceptions (Nisiotou et al., 2007), Saccharomyces strains dominate fermentation sooner or later, as in nonbotrytized wine. A special feature of botrytized fermentations is that, beside various S. cerevisiae races, S. uvarum (formerly known as S. bayanus var. uvarum) is typically isolated from these wines (Antunovics et al., 2003 Magyar et al., 2008 Minarik and Laho, 1962 Naumov et al., 2000, 2002 Sipiczki et al., 2001 Tosi et al., 2009). This species seems to be well adapted to sweet wine fermentations, particularly, but not exclusively, in cooler climates. 

The unique chemical composition of botrytized must greatly impacts the products and by-products of alcoholic fermentation, as well as subsequent reactions. The changes have been extensively studied by German and French authors and have been reviewed by Dittrich (1977, 1989), Jackson (2008), Ribereau-Gayon et al. (2000), and Dittrich and Grossmann (2011). The chemical composition of some traditional (German and Hungarian) botrytized wine styles are illustrated in Table 6.5. 

The amounts of thiols formed during alcoholic fermentation are strongly affected by the previous development of B. cinerea (Table 6.7). Since these compounds have extremely low sensory thresholds, and seem remarkably stable in wine, 3SH particularly plays a significant role in the fruity aroma of botrytized wines (Dubourdieu and Tominaga, 2009). 

A special aspect of botrytized wine making is the cessation of fermentation at a desired residual sugar content. Traditionally, fermentation... 

Cessation of fermentation is one of the technical problems in botrytized wine production that needs further research and development. Dimethyldicarbonate (DMDC) is now considered a reliable inhibitor which could replace some of the S02. Although DMDC has proven suited for treating wines especially just before bottling, its use in Sautemes production has been investigated (Divol et al., 2005). The results showed that DMDC at a rate of 100-200 mg/1 stopped fermentation but did not replace the antioxidant functions of SO2. Sulfite addition was necessary to limit wine oxidation and yeast reactivation. 

Malolactic fermentation is often viewed as the main source of polyamines in wine production (Marcobal et al., 2006). Thus, their presence is more significant in red wines than in white ones. Of white wines, sparkling wines, biologically aged wines, and botrytized wines might be the most susceptible to biogenic amine formation. 

Eder et al. (2002a,b) surveyed 117 Austrian wines including 55 potentially botrytized Pradikat wines (Auslese, BA, Ausbruch, TBA) for OTA. None of the samples contained the toxin at a detectable levels. In 121 different wines studied by Valero et al. (2008), the wines with the highest OTA contents were those produced from must fortified before fermentation (4.48 gg/1) and those made from sun-dried grapes (2.77 gg/1). Wines affected by noble rot contained no detectable OTA. Icewines and late-harvest wines were also not contaminated. Nonetheless, an elevated OTA concentration has been reported in some South African botrytized wines (Stander and Steyn, 2002). 

Botrytis Effect on Fermentation. Peynaud et al. (28) suggest that Botrytis cinerea ( noble rot ) produces a substance that inhibits yeast activity. While this substance has not been isolated in the United States, it has been the author s observation that botrytis-infected grapes ferment at a slower rate and have more difficulty completing fermentation. This fermentation inhibition also may be attributable to the higher initial °Brix and, later, to the ethanol and higher residual sugar content of the botrytized wines. 

Experts from the OIV estimate that the concentrations recommended by the EC can be decreased by 10 mg/1, at least for the most conventional wines. In this perfectly justified quest for lowering SO2 concentrations, specialty wines such as botrytized wines must be taken into account. Due to their particular chemical composition, they possess a significant combining power with sulfur dioxide. Consequently, their stabilization supposes extensive snlfiting. The EU legislation authorizing 400 mg/1 is perfectly reasonable, but this concentration is not always sufficient. In particular, it does not gnarantee the stability of some batches of botrytized wines and will not prevent them from secondary fermentation. 

On the basis of these findings, DMDC was initially authorized in the United States, then in other countries. Like ethyl pyrocarbonate, DMDC is most effective at the time of bottling, although it has also been suggested for use in stopping the fermentation of sweet (botrytized) wines (Bertrand and Guillou, 1999), thus reducing the amount of SO2 required. In any case, a certain quantity of free SO2 is always necessary to protect the wine from oxidation. 

FIGURE 6.4 Course of alcoholic fermentation and evolution of the yeast populations during spontaneous fermentation of Tokaji Aszu. Botrytized berries were macerated with fermenting must (A) or dry wine (B) (Magyar, 2010). 

Fedrizzi, B., Zapparoli, G., Finato, F., Tosi, E., Turri, A., Azzolini, M., and Versini, G. (2011). Model aging and oxidation effects on varietal, fermentative, and sulfur compounds in a dry botrytized red wine. J. Agric. Food Chem. 59,1804—1813. 

The yeast strain used for fermentation had no impact on the enantiomer distribution of these volatile thiols. 3SHA is generally considered to be formed by esterification of 3SH by yeast during alcoholic fermentation. The esterase or lipase involved probably acetylates 3SH with a certain enantioselectivity. In contrast, the enantiomer distribution of 3SH in wine made from botrytized grapes (Botrytis cinerea) is 25 75 in favor of the S form, which has also been found in botrytized must (Thibon et al. 2007,2008a). 

The addition of thiamine is legal in several countries (EU, at a dose of 50 mg/hl) but it is rarely used to accelerate fermentation in winemaking. It effectively decreases significant ketonic acid concentrations by decarboxylation (pyruvic and a-ketoglutaric acid). Large quantities of these acids bind to sulfur dioxide in botrytized sweet wines (Section 8.4.2). 

Considering these phenomena, the addition of SO2 to a fermenting must should be avoided. It would immediately be combined without being effective. When the grapes are botrytized, the variation in the ethanal content of different wines when 50 mg/1 of SO2 is added to the must accounts for a combining power approximately 40 mg/1 higher than that of non-sulfited control wines. When stopping the fermentation of a sweet wine, a sufficient concentration should be added which... 

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