The SOMM Journal

December 2014/January 2015

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66 { THE SOMM JOURNAL } DECEMBER/JANUARY 2014/2015 P HO T O S C O U RT E SY O F DR . D A R K O M A KO V E C , PU BLI S H E D IN B I O C H E M I C AL E N G I NE E R I NG THERE'S NO MISTAKING A GYROPALETTE AT WORK, BUT you'll need a scanning electron microscope to see the iron nanoparticles that have the potential to make it obsolete. A team of biochemists, working in conjunction with a nanotech- nology researcher, have introduced a riddling technique that uses nanoparticles and a magnet to riddle a bottle of sparkling wine in approximately 15 minutes. "The method itself is 4,000 times faster than classical hand remuage," says biochemical engineer Professor Dr. Marin Berovic. Berovic and his team at the University of Ljubljana, Solvenia worked with nanotechnol- ogy researcher Professor Dr. Darko Makovec, who heads the Jožef Stefan Institute's Department for Materials Synthesis, to develop an elegant and inexpensive method of bonding silica-coated nanoparticles of iron oxide to yeast cells (a mass ratio of 1:10) and then using a strong permanent magnet to sediment the spent magnetized yeast cells. The speed and efficiency of the process, which has already been widely studied and applied in bio- technology and water purification, relies on the absorption of super paramagnetic amino-functionalized iron oxide maghemite nanoparticles onto both Saccaromyces cerevisiase and Saccharamyces bayanus yeast cells. In a three-part process, iron oxide nanoparticles are coated with silica, which is grown around them in a thin layer. When the positively-charged nanoparticles are introduced to a yeast cell culture, the nanoparticles bond to the negatively-charged yeast cells and are dispersed as they divide and then cluster together after fermentation. Once spent, the yeast cells are separated from the wine using a strong magnet at the neck of the bottle. Although iron oxide nanoparticles are considered non-toxic and have been approved for use in living medical applications, standard winemaking chemistry identifies unstable levels of iron at above 6 mg/L in white wine which can result in white iron phosphate deposits or iron casse. The Solvenian team's study points out that the level of iron present in the finished wine fell below the 10.00 mg/L range allowed by the European Union in white wine at 8.30 +/-1.6 mg/L Fe 3+ . Arthur O'Connor, who directs winemaking for the CordoníuRaventos Group, parent company of Cava category leader Cordoníu, and is President of Artesa Winery in Sonoma, CA, says, "We've spent years and years figuring out which yeasts give us the best results." O'Connor is currently using a proprietary form of agglomerated yeast in conjunction with a special gyropalette that has reduced riddling time to about one hour. While yeast trials have been costly and time consuming for CordoníuRaventos, the company continues to be an early adopter. "We follow current research and treat new ideas very seriously," O'Connor says. "In addition to riddling, there also seems to be considerable potential for using magnetized metal and electromagnetic fields in developing new methods for ster- ile filtration and color extraction in still wines." The sensory evaluation of magnetic-yeast fermented wines could well be an arbiter of success. Berovic's research shows that magnetized-yeast fermentation slightly increased the intensity of aromatic compounds and mouthfeel in finished wines, with apple, citrus fruits, pear and melon flavors being more apparent to tasters. Color intensity, body structure and CO 2 bubble texture were deemed identical to the high-quality sparkling control wines. The technology, which was published in its entirety in the March 2014 edition of the Biochemical Engineering Journal, is patented in Slovenia and is now making its way through the E.U. patent process. Adoption by the sparkling wine industry would enable many producers to leapfrog several generations of yeast technology and forgo use of the gyropalette forever. Scanning electron microscope (SEM) image of a yeast cell before the "magnetization." SEM image of a yeast cell exposed to magnetic nanoparticles before fermentation. SEM image of yeast cells exposed to magnetic nanoparticles after fermentation. Riddle Me This NANOTECHNOLOGY MAY BE THE FUTURE OF REMUAGE by Deborah Parker Wong Dr. Darko Makovec, who heads the Jožef Stefan Institute's Department for Materials Synthesis, helped develop the new technology.

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