November 22, 2013
Chelation Compounds May Help Curb Oxidation In Wine
April Flowers for redOrbit.com - Your Universe Online
Food scientists report that they have found an additive which may help curb a chemical reaction that causes wine to look, smell and taste "funky."
Gal Kreitman, a doctoral candidate in food science at Penn State, led the research team that added chelation compounds that bind with metals to inhibit oxidation - oxygen's ability to react with some of the trace metals that are found in wine. The results of their study were published in a recent issue of the Journal of Agricultural and Food Chemistry.
"Oxidation has several bad effects on wine, such as discoloration and a loss of aroma," said Kreitman. "It can cause browning, as well as the loss of fruity characteristics, something that is much more noticeable in white wines."
Typically, oxygen enters wine through the cork. Once inside the bottle, the oxygen mixes with metals, particularly iron, and sets off a chain reaction that changes compounds. These changes add particular and often disagreeable tastes and smells to the wine.
There are two types of oxidation states in wine - iron 2 and iron 3. The research team looked at chelators for both states, including bipyridine, ferrozine, ethylenediaminetetraacetic acid (EDTA) and phytic acid.
Kreitman collaborated with Ryan J. Elias, assistant professor of food science, Penn State; Annegret Cantu, director of research and development at VinPerfect; and Andrew Waterhouse, professor of enology, the University of California Davis on this study. The team found that both types of chelators significantly inhibited the oxidation in the wine.
"The ligands of bipyridine, ferrozine, EDTA and phytic acid bind to the metals, which can inhibit their reaction," said Kreitman. A ligand is a type of molecule that is able to bind to the central atom of a metal.
The team analyzed the concentrations of iron and copper in white wine. They also measured the amount of oxidation that occurred after the chelators were added to the wine samples. The white wine used in the experiment was made from pinot gris grapes, a variety that is often used in white wines.
Previous attempts to control oxidation by winemakers have included stripping out the metals, which are acquired through the soil and from the grape. These processes are impractical and expensive, according to Kreitman.
"Unfortunately, the process to remove the metals can strip color and flavor compounds from the wine and processes like ion exchange can end up making the wine taste more salty," Kreitman said.
Further research is required to find food safe chelators, according to Kreitman. There are chelators that are already safe for consumption, but the majority have not been approved for food-making or winemaking processes. The team suggests that phytic acid is a chelator that might be effective in neutralizing oxidation while being safe for consumption.