Could a New Tool Prevent Oxidation in Winemaking?

(WineSpectator) - When it comes to keeping their wine safe from oxidation—the chemical reactions with air that can spoil a wine—the tools at a winemaker’s disposal are limited. After fermentation, vintners try to limit oxygen exposure, and they choose bottle closures with care. Many also add sulfur dioxide, which is effective in ensuring chemical stability, among other things, but which in excess can mask some of a wine’s aromas.

Researchers have begun to ask, however, whether there might be another measure to prevent oxidation. Taking a cue from food manufacturers, Prof. Andrew Waterhouse and his team at the University of California at Davis began to look at the chemical compounds found in wine—mostly transition metals iron and copper—that serve as oxidation catalysts. By binding these metals with ions known as chelators, Waterhouse reasoned, they could prevent this catalyzation. A paper recently published in the Journal of Agricultural and Food Chemistry confirms this hypothesis.

“We found that we could really control the extent of oxidation, at least in a model wine system, with these chelators,” Prof. Ryan Elias, of the Department of Food Sciences at Pennsylvania State University and a coauthor of the paper, told Wine Spectator.

For their study, the researchers created a model wine—a solution mimicking wine made of ethanol, tartaric acid and a phenolic. They observed the effects of four different chelators on this solution, focusing on the ions’ ability to bind to iron. Iron atoms cycle between two different states, gaining and losing electrons. This cycle, known as reduction-oxidation, or “redox,” is what catalyzes oxidation. It creates free radicals, which react with organic compounds in wine to undesirable ends. For example, radicals can help form acetaldehyde, the antecedent of vinegar’s main component, acetic acid; they can also lead to the loss of thiols that contribute to a wine’s sensory characteristics.