( Researchers at the University of Barcel...)After the yeast is gone bacteria continue to develop flavor of sparkling wine

"Bacteria found in Cava samples could have a distinctive impact upon sparkling wine quality in terms of aroma, flavor, bubble size and bubble persistence, especially for premium quality wines," says Núria Rius, a researcher on the study.

The traditional Champenoise method of sparkling wine production requires addition of sucrose and yeast strains to the base wine for a second fermentation in the bottle in which the wine is sold. The secondary fermentation produces carbon dioxide which dissolves in the wine and is perceived as bubbles when the bottle is opened, hence the term "sparkling". After the fermentation is completed the Cava wine is aged in the bottles with the yeast for at least nine months, or longer for premium quality wines. During aging, substantial chemical changes take place due to cell lysis which contributes to the sensory characteristics of Cava.

The researchers isolated 617 microbial strains from two Cavas, after 9 to 17 months of bottling. No yeasts were isolated after 10 months of bottling. Gram-negative and Gram-positive bacteria were isolated from both wines. Different phases of the aging process are dominated by different bacteria. Gram-negative bacteria were quickly replaced by Gram-positive bacteria, and after 17 months only Gram-positive bacteria were detected in both sparkling wines.

"The products released by the yeast cells affect wine flavor and serve as nutrients for the growth of bacteria. Although yeasts have the dominating influence on the chemical composition of wine, some changes which influence the sensory quality and consumer acceptability of the wine could be due to growth and lysis of bacteria," says Rius.<
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Source:American Society for Microbiology