Bacteria contribute to bubble size and persistence in sparkling wine

The traditional Champagne method of sparkling wine production requires the addition of sucrose and yeast strains to the base wine, for a second fermentation in the bottle.

Speaking this week in the US at the meeting​ of the American society for Microbiology, Spanish scientists from the University of Barcelona suggest the powerful role bacteria can play in the second slice of fermentation.

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

The secondary fermentation produces carbon dioxide which dissolves in the wine, and is perceived as bubbles when the bottle is opened, resulting in the term 'sparkling'.

After fermentation is completed, Cava wine is aged in the bottles with the yeast for at least nine months, or longer for premium quality wines.

During ageing, substantial chemical changes take place due to cell lysis, which contributes to the sensory characteristics of Cava, say the scientists.

"The products released by the yeast cells affect wine flavour 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.

The Spanish team isolated 617 microbial strains from two Cavas, after nine to 17 months of bottling. No yeasts were isolated after ten months of bottling and Gram-negative and Gram-positive bacteria were isolated from both wines.

According to the researchers, different phases of the ageing 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.