Some people are allergic to certain wines -- that nice Loire Valley red gives them a rash or headache, or that California Chardonnay makes them sneeze. The University of British Columbia's Wine Research Center might have found a way to solve this problem.
The team at UBC has modified two genes of a strain of yeast called Saccharomyces cerevisiae, which has been used in winemaking for decades (if not centuries). The yeast was modified to eliminate the need for a species of bacteria needed for the winemaking process. That bacteria produces chemicals that cause allergic reactions. About 30 percent of the population has some allergy to wine.
Ordinarily winemakers use yeast to convert the sugar in the grape juice to alcohol. But wine isn't just made from juice; it also involves something called must, which is the skin and other stuff from the grapes that get crushed. After the yeast converts the first batch of sugars to alcohol, there's a secondary fermentation that happens, as bacteria in the mixture convert malic acid –- which has a harsh taste –- into lactic acid, which is smoother. In modern commercial winemaking the bacteria is added deliberately.
Hennie van Vuuren, the Director of the Wine Research Centre at UBC, who led the research, told Discovery News that the bacteria can present a problem: sometimes they convert chemicals called histidines in the wine to histamines. Histamines are what give some people allergic reactions, if they are particularly sensitive to them. (It is not always the histamines that cause the problem; sulfites can as well, and there are people who are allergic to the alcohol itself).
Van Vuuren said his team took the gene from the malolactic bacteria that allow the malic acid -- which yeast usually ignores -- to cross the yeast cell membrane. They also added a bacterial gene that allows the yeast to digest the malic acid.
The result is yeast that eliminates the need for malolactic bacteria and avoids producing chemicals that can cause reactions to the wine. Since the yeast is digesting the same chemicals that the introduced bacteria would, it doesn't affect the taste.
Van Vuuren noted that for the wine industry it would be a big boost to sales, since it would mean all those people who can't drink wine would be able to do so. He himself has a wine allergy but tended to limit his drinking to wines that have aged. "I really like wine, I couldn't have a meal without it," he said. In older wines the histamines are less of an issue, as they break down over time. But that limited his selection to rather expensive wine, or to ports and Madeiras. So Van Vuuren wanted to solve the problem of making wine allergen-free. It took several years to find the right genes, and find a way to insert them into the right yeast.
As to which wines will use this new yeast, he couldn't say, though he noted that it has been approved for use in Canada and the U.S. Van Vuuren is awaiting approval from the European Union, and at that point, he said the South African winemakers will adopt it as well.
This story was provided by Discovery News.
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