Jura wines

Flor microbiota was first studied by Pasteur in 1875 (Charpentier et al. 2000), who called it Mycoderma vini, in Jura wines. Microbiological analyses of flor Aims in Jerez and Montilla-Moriles wines have revealed a high variability in microbial... 

Wines aged under a flor film typically contain various compounds especially important among which are lactones. Thus, solerone (4-acetyl-y-butyrolactone) abounds mfino and Jura wines and has for years been deem one of the greatest contributors to their aroma profiles (Augustyn et al. 1971 Muller et al. 1973). However, subsequent studies have suggested that this lactone has no impact on wine aroma (Martin and Etievant 1991). 

It has been suggested that the presence of aldehydes and methyl-ketones contribute to the rancio odor of barrel aged Port wine (2) and also in white wines (1). Other volatiles, were also studied in ports (5, 4, 5, 6, 7, 8). More recently, 3-hydroxy-4,5-dimethyl-2(5H)-furanone (Sotolon) has been suggested to be a key odorant in the aroma of aged port (9). This highly odor active molecule has been shown to contribute to the aroma of Jura wines vin jaunes 10, 13, 14, 15), vins doux naturels (14) Tokay wines 11), Botrytised wines (id) and Sherry wines (72). 

Some wines such us Sherry (Spain), Vemaccia (Italy), and Jura yellow (France) are developed under oxidative conditions, utilizing yeasts known as Flor-yeast. These yeasts belong to the S. cerevisiae var. prosto-serdovii which aid in the development of certain specific sensory characteristics (Fatichenti et al., 1983a,b). Studies were conducted with flor-yeast... 

Recently Webb (16) explained the aromas of film sherries as by-products of an incomplete metabolic sequence where ethanol is being metabolized by film yeasts to carbon dioxide and water. Webb also refers to Pasteur s Etudes sur le Vin, published in 1866, as the basis of the specialization of zymology, which recognizes different types of film formers that yield the wines of the Jerez district of Spain, Vinsjaunes of the Jura region of France, and the flor wines of Australia, South Africa, the Soviet Union, and California. 

Jura yellow wines have also been found to contain the races beticus (67%), montuliensis (26%) and cheresiensis (7%) (Charpentier et al. 2000). 

In view of the very small quantities of free ethanal present in still wine, their acetal content is practically zero. Only wines with a high ethanal content have a significant concentration of acetal. Sherry, with an ethanol concentration on the order of 280 mg/1, contains 45-60 mg/1, while the concentration in Vin Jaune from the Jura may be as high as 150 mg/1. 

Sotolon (Volume 1, Section 10.6.4) also results from a condensation reaction, not catalyzed by enzymes, between a-keto butyric acid and ethanal. It is also present in Vin Jaune from the Jura, where it is responsible for the walnut aroma so typical of this wine (Martin et al, 1992). 

The concept of oxidative defects is quite subjective, as there are many wines where an oxidative character (rando) is considered desirable. Wines aged under a yeast bloom are a classic example, e.g. Vm Jaune from the Jura (Volume 1, Section 14.5). The yeast acts as an oxidation-reduction bnffer and prevents excessive oxidation. Vin Jaune is well known for its highly oxidized character and contains large concentrations of free and combined ethanal (Fignre 8.1) (Etievant, 1979). The same is trne of Sherry. 

Pasteur was the first to include flor with bacterial problems, because, like acetic spoilage, it involves a mycodermic microorganism. However, flor is caused by a yeast (which Pasteur called My coderma vini) and not a bacterium (Mycoderma aceti). Flor should not be confused with the bloom formed by Saccharomyces cerevisiae under certain, specific, conditions, responsible for producing high-quality wines such as Sherry and Vin Jaune from the Jura (Volume 1, Section 14.5). 

S. cerevisiae can metabolize ethanol by the respiratory pathway in the presence of small quantities of glucose. After alcoholic fermentation, oxidative yeasts develop in a similar manner on the surface of wine as part of the process of making certain specialty wines (Sherry, Yellow Wine of Jura). 

Sherry in english and german—Jerez in Spanish—Xeres in french is the best-known flor wine. In o/oro5o-type sherry, the aging process is essentially physicochemical and biological development is limited. The oloroso method will, however, be described in this section. Jura yellow wines are another well-known example of flor wines. 

The yellow wines from Jura are characterized by their high ethanal concentration (600-700 mg/1), their deep color and their particular organoleptic characteristics. 

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