Wine is product of yeast survival

Media release 28 July 2008

Wine is product of yeast survival

Wine is the result of a competition between microbes for nutrients, research suggests.

Scientists at The University of Auckland studying yeast used in winemaking have discovered the reactions that turn grape juice into wine are a mechanism to ensure the yeast secures many of the nutrients from the fruit.

The results are published in the latest issue of leading international journal Ecology, and one of West Auckland's wineries, Kumeu River, is pictured on the front cover.

The researchers studied the microbes present on grapes from the field to the cellar at Kumeu River Winery, and discovered very low levels of Saccharomyces cerevisiae, the yeast required to convert sugar to alcohol, naturally present. However, it created a warm, high alcohol - low oxygen environment which is toxic to all other yeasts and microbes during the fermentation process allowing its numbers to rapidly increase. This environmental-engineering is wasteful for the yeast, as it is more efficient to completely metabolise the fruit sugar to water and carbon dioxide, but the fermentation releases ethanol and heat and ensures S. cerevisiae is the sole survivor.

"Environmental engineering is a known concept, originally described by Darwin," says Dr Mat Goddard of the School of Biological Sciences. "However, while many organisms modify their environment – think of beavers building dams - the evolutionary effect of this has never been measured before. In the case of winemaking, it seems Natural Selection has caused yeast to adapt to change its environment to create a competitive advantage over other microbes in the niche. We first have to understand the fundamental process of winemaking if we are to ever reliably apply the results so the NZ wine industry can benefit."

The research was part funded by a six year Foundation for Research Science and Technology project, looking at the specific characteristics of New Zealand Sauvignon Blanc, and the rest was funded by the School of Biological Sciences. The FRST project, headed by The University of Auckland and in collaboration with New Zealand Winegrowers, HortResearch, Lincoln University and winemakers nation-wide, is looking at the effects of growing conditions, fermentation and aging in the bottle on wine aroma.

ENDS

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