Scientists in Australia have sequenced the genome of brettanomyces, a yeast organism responsible for producing off flavors in wine. They hope the breakthrough can be used to eliminate the winemaking problem.
Brettanomyces can lurk in certain vineyards, or it can contaminate a winery and find its way into barrels or other storage containers. When brettanomyces enters the wine at sufficiently high levels, it can produce compounds that taste funky, ranging from leathery and gamy to metallic and medicinal flavors.
An Australian Wine Research Institute (AWRI) team led by senior research scientist Chris Curtin last week announced the genetic sequencing of Dekkera bruxellensis, the yeast responsible for the character many wine tasters abbreviate to “brett.” The research was published in the November/December issue of Wine and Viticulture Journal.
Although brett is not dangerous to human health, opinions differ on whether detectable levels of it destroy a wine or if small amounts can enhance a wine’s complexity. Most vintners say they try to avoid it.
"Like body odor, it didn’t used to be a problem until someone invented deodorant,” said Curtin. “Once we realized wine did not have to have brett, it became obvious we'd better find a way to control it.”
The Australian research organization, funded by dues paid by Australian wineries and vineyards matched by the Australian government, has carried on a crusade against brett since the early 1990s. That’s when AWRI researchers noticed widespread unacceptably high levels of brett in laboratory tests of commercial wines that the organization conducted as part of its work. It launched an educational campaign to show winemakers how to use sulfur dioxide, winery hygiene and pH management to keep the yeast from taking over.
Today, Australia has reduced the number of wines infected with the organism at higher than threshold levels by 90 percent, AWRI reports. In a disturbing discovery, however, tests involving wines made from 1998 to 2005 identified a sulfite-resistant strain in 85 percent of samples.
“And it was growing,” Curtin added. “So we did the genome, and we found that brett has a third strand of DNA. We think we have found the gene that is making that strain more sulfite-tolerant. If we can find its Achilles' heel, we can future-proof the industry against brett.”
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