Researchers have determined the yeast gene that produces a rose and honey-like flavor compound, only the latest discovery in this field.

Mike Pomranz
November 09, 2017

Yeast is the most underappreciated component in the flavor of beer or wine. Don’t believe it? Try drinking unfermented grape juice or, even worse, unfermented beer mash. Yeah, you know who can turn that crud into an awesome drink… yeast! And besides tearing through sugars and replacing them with carbon dioxide and alcohol, different yeasts also contribute different flavor compounds to the mix as fermentation progresses. To better understand just how this process works, scientists have been using genetic mapping to determine which yeast genes are responsible for which flavors—with the hope that in the future, yeasts could be created that are able to further accentuate specific aromas and tastes.

In a study published this week in the journal mBio, researchers in Belgium report that they have uncovered another one of these yeast genes, this time targeting the part of a yeast’s DNA that creates the flavor compound called phenylethyl acetate – known for its pleasant rose and honey notes. “In some wines, you can smell the rose flavor above all the others,” microbiologist Johan Thevelein, one of the study’s lead authors, said in a statement. “But why certain yeast strains make more of this compound than other strains, there was no knowledge at all.”

Admittedly, the actual science behind the discovery is a bit tough to wrap your head around for those of us more focused on learning about wine than genetics. The gist is that the team behind the study isolated two genes they believed were behind production of the compound. Then, using a bit of genetic engineering, they were able to create a new yeast strain that increased the production of phenylethyl acetate “significantly.”

As Thevelein points out, creating new yeast strains to have a specific desired effect is nothing new, but in the past the process was arduous and a bit of a crap shoot. He explained that his research could make this process much easier. “You have to do two things,” he stated. “One is to improve the yeast trait that you want to improve. Second is to change nothing else in the yeast. In practice, the latter turns out to be much more difficult than the former.” Meanwhile, using a yeast strain that doesn’t have the desired effect can have another terrible consequence.  “If the fermentation is bad, you have to throw away all the beer,” he lamented.

According to the American Society for Microbiology, similar gene editing methods have been used in recent years to identify the specific genes behind “an array of flavors, including nerolidol (a woody scent), ethyl acetate (a sweet smell, as in nail polish), and sulfur flavors.” At the same time, Thevelein and his team have also identified the genes “responsible for banana- and butter-like flavors.” For one of their next steps, they’ve already teamed up with a Belgian brewery to test their findings – because that is obviously the best part of this work.

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