Works in Progress - Summer 2012

Grape Expectations

By Vanessa Schipani | June 1, 2012

Although fruit quality, harvest time, and storage of the juice are important in winemaking, the difference between a generic red and a truly excellent wine lies in the spontaneous fermentation by naturally occurring yeasts. But managing yeast microorganisms is fraught with unknowns because some wild ones can harm fermentation.

In an effort to help winemakers hone their craft, researchers in Germany have developed a biosensor that can discriminate between the wild yeasts that lead to spoilage and those that release chemicals that create the array of flavors and aromas characteristic of an excellent wine. The prototype device, about the size of a cell phone, contains 10 Plexiglas tubes, each lined with a protein that recognizes a specific yeast strain. The winemaker fills each small tube with juice, and a biochemical reaction causes a color change if a particular yeast strain is present. The team, led by Mark Bücking of the Fraunhofer Institute in Germany, has already identified 10 strains of wild yeast that are predominant during spontaneous fermentation of wine and is investigating the effect each has on flavor and aroma.

“There are a lot of techniques available to evaluate yeast in the laboratory, but the time you need to send the samples to the lab and to make the analysis can be critical when the fermentation is having problems,” says Fraunhofer microbiologist Cecilia Díaz. With this one-use device, which is expected to cost no more than $65, winemakers can test within minutes which wild yeasts are present before fermentation has even begun. By monitoring the process more closely, winemakers can reduce the risks of making their top wines in larger batches.

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