Researchers in Slovenia have developed a new tool for sparkling-wine production that they claim could eliminate the centuries-old practice of riddling: magnetized yeast. By charging yeast with magnetic nanoparticles, the scientists say that they can use a magnet to draw yeast to the bottle neck—reducing a 60-day process to a 15-minute operation. But the research is preliminary and leaves sparkling winemakers with many unanswered questions.
“It’s extremely interesting, that's for darn sure," Tom Tiburzi, sparkling winemaker for bubbly producer Domaine Chandon California, told Wine Spectator. "It could be exciting to think it could work, but it's hard to visualize some of it."
If you want to make sparkling wine in the méthode traditionelle developed in Champagne, you must riddle. After undergoing secondary fermentation, bottles of nascent sparkling wine sit aging on their yeast (in Champagne, they must age that way for at least a year). But how to remove that yeast from the bottle? Riddling is the process whereby winemakers position the bottles on racks at 45 degree angles, then twist, turn and shake them for about 60 days so that the yeast sediment moves to the neck of the bottle. Once the solid matter is concentrated there, it can be removed.
For their study, researchers at Slovenia's University of Ljubljana first made yeast cells responsive to magnets by affixing superparamagnetic nanoparticles onto their surfaces. The yeast performed fermentation on the test wine (Tocai Fruilano from Slovenia) in 24 days. Then the scientists held a magnet to the bottle neck. In 15 minutes, all of the yeast in the bottle was concentrated in the neck. (Conventional disgorgement followed.)
Tiburzi was skeptical of many of the study's methods, including the fact that the unfermented grape juice appeared to have unusual microbial growth. He pointed out that the researchers completely bypassed the year of sur lie aging. "How is this going to work if it's aged in the bottle for a year?" he asked. "Are those little magnetic particles still going to be attached to the cells?"
Moreover, the final wine in the study, post-yeast-removal, showed 8 milligrams per liter of iron, while a control wine had only 0.35 milligrams per liter. This suggests that the magnetic nanoparticles may have been responsible for the high iron count.
"If iron is leeching into the wine from the nanoparticles," Tiburzi said, "I would guess that there would be more after a year." Excessive concentrations of iron in wine can lead to cloudiness and oxidation. In the European Union, white wine's iron may not legally exceed 10 milligrams per liter.
Nicolas Chiquet, of grower Champagne producer Gaston Chiquet, said that although increasing efficiency is always a good goal, the riddling process as it stands is not so bad. With the gyropalette—the riddling machine developed in northern Spain for cava producers in the 1970s—Chiquet needs only three to seven days to consolidate the yeast in his bottles, he said. "There is [little] to win, and a lot of unknown, concerning Champagne with magnetized yeast," he said. Chiquet produces about 17,000 cases a year, 90 percent riddled by gyropalettes and 10 percent by hand.
"Of course, if we see after several years of tasting that magnetized yeast do not have any effect on the quality," Chiquet added, "I will be very interested in this method. Time, space, manipulation and cost would [be] decreased. We are open to every innovation, but our first priority is the quality.”
Tiburzi said that he would consider using magnetized yeast in the future if he were convinced that it does not negatively affect the wine—but only if doing so would still allow him to print “méthode traditionelle” on his labels. The traditional method "is a big part of who we are at Domaine Chandon, a big part of our DNA," said Tiburzi.