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article imageEnzyme rapidly reduces sulfites in wine

By Tim Sandle     Feb 8, 2015 in Science
Sulfites are added to wine as a preservative, to prevent adulteration by unwanted microbes. However, some are concerned about the health risks. This has prompted research about sulfite removal.
Sulfites are commonly used to increase the shelf-life of wine (ncluding sulfur dioxide and sodium metabisulfite.) To an extent, sulfites occur naturally in all wines. They are, in mass produced wines, also added to slow down fermentation (at the required time), and to increase the shelf-life of the wine (to prevent the fine grape juice from turning into vinegar). Through these different steps, white wines tend to contain more sulfites than red ones.
Some people, although there is not a great deal of medical evidence, think the sulfites are bad for health (or, at least in terms of a drinker's folklore, are responsible for the morning after headache). For a minority, there is a condition of sulfur allergy, and the risk of this is considerably higher for asthmatics. However, for the majority, there is no observable reaction.
Nevertheless, due to concerns about sulfites and health risks, a growing market in organic wines has developed. Although these are sometimes marketed as sulfite-free, they still contain natural trace levels. However, sulfites are either not added during the process or attempts are made to remove them. In the U.S., a wine only has to be labeled as containing sulphites if it has more than 10 parts per million (so many "organic" wines do, in fact, contain sulfites).
Finding efficient ways to remove sulfites is the basis of a new research study, performed by scientists from the Albert-Ludwigs-Universität Freiburg,
Scientists have now characterized a bacterial enzyme that reduces sulfite up to 100 times faster than any other known enzyme. The identified chemical is enzyme complex MccA, a type of iron-rich metalloprotein. This enzyme occurs in certain bacteria, which means that genetically modified microorganisms, designed to be capable of high-speed sulfite reduction, could be used for desulfurization of wine.
The bacterium with the best scope for production of the enzyme is Wolinella succinogenes. This bacterium is common to the stomach of cows. The organism, and it enzyme, are adept at reducing sulfite to sulfide, and furthermore, reducing sulfur dioxide to sulfide.
The new research has been published in the science journal Nature, in an article titled "The octahaem MccA is a haem c–copper sulfite reductase."
In related wine-meets-science news, one group have scientists have determined that there is no such thing as white wine. A new scientific survey has revealed that white grapes also contain the pigments that give red wine its color. Meanwhile, for those who have ever wondered how many bubbles there are in a glass of champagne, a different science team has the remarkable answer.
More about Wine, Sulfites, Wolinella succinogenes
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