Scientists at the university, with help from colleagues at the University of California Davis Campus, have been working on developing this new tool for authentication. The scientists can genetically identify grapes but so far there has been no way to scientifically identify the grape varieties in a finished wine.
Dr. Eric Anslyn and his team of undergraduate research students have created receptors that respond to tannins in different types of grapes. The process involves placing a combination of chemicals on display plates with 96 separate wells. The team then adds samples of wine to these receptors. “The receptors change colour when we apply mixtures of tannins,” says Anslyn according to the report in Wine Spectator. Using a computer program to analyze the results, the team tested different types of red wines and found that the tannins produce different recognizable patterns. “It really relates to the DNA coding of the wine,” he says.
The group chose to study red wines since they have the most tannins. They tested varietals, including Zinfandel, Cabernet Sauvignon, Pinot Noir, Shiraz and Gamay, from various producers. White wines were not included in the test, but Anslyn believes that the procedure can distinguish between white grapes since they contain tannins as well.
For years, scientists and producers have had to rely on other methods to identify grapes. “With fresh [grapes] you can do genetic analysis,” said Dr. Andrew Waterhouse, viticulture and enology chair at U.C. Davis. But there have been no tests that can identify varietals once they go through the winemaking process. “When you look at wine, the DNA is broken down so much that, so far, no one has been able to capture the DNA [of the grapes] from finished wine.”
According to Anslyn, the study’s goal was not to produce a tool for the wine industry. They wanted to create diagnostic solutions for diseases by analyzing tannins. “The real basis of this work is to prove that technology can distinguish mixtures of chemicals and where they come from,” Anslyn said. He says he decided to study wine because of its complexity and because people are interested in it.
There are limits to the technique, however. “With the limited set of wines we studied we could mostly tell one varietal from another” said Anslyn. So far the error rate for the test is still unknown. Anslyn also said that the process has not addressed wine blends or aged wines though he is certain that there will be a point in the future when they will be able to authenticate both.
The method could prove useful—when wine companies like Gallo purchase bulk or bottled wines from other producers or in other countries without ways of verifying the wine’s grape varieties.