Issue link: http://read.dmtmag.com/i/197178
using MS, and combinations of MS with other methods such as chromatography. + Interaction: Progress is being made in understanding the forces that lead to intermolecular association of tannins with protein. Analytical advances have improved the ability to understand how structure relates to function, and recent developments suggest an assessment of intermolecular association between tannins and macromolecules is possible. The challenge, Kennedy said, is that "No one test provides the analyses needed for all of these," so they require multiple analyses. IN THE VINEYARD Mark Downey, a research viticulturist with the Department of Environment and Primary Industries in Australia, discussed recent research regarding grape tannin levels in vineyards. Major factors influencing tannin content in grapes are genetics (variety differences), vineyard site, season and management. Downey presented information comparing skin tannin content for 36 grape cultivars. Somewhat surprisingly, it showed that some table grape varieties, such as red emperor, had higher skin tannin levels than wine grape varieties, including those traditionally considered to be high in tannins, such as nebbiolo and tannat. The tannin level in nebbiolo skin was actually among the lowest of the group, and tannat levels were similar to those of cabernet sauvignon and shiraz. Downey said site and seasonal differences can significantly affect different varieties and their tannin levels and composition. "There is a big difference from season to sea- son, and seasonal variation seems to be the biggest driver," he said. Seed tannin doesn't vary as much, he added, compared with changes and variations in skin tannins, so he suggested focusing on managing skin tannins. In addition, significant variation in skin tannin content can occur within the same vineyard, commonly associated with vine vigor. Research data from shiraz vineyards in Australia and pinot noir vineyards in the United States showed that grapes from high-vigor vines tended to have lower tannin levels, while grapes from low-vigor vines had higher tannin levels. Vineyard practices that may affect tannins include: irrigation, canopy management, trellis, nutrient status, pruning, harvest date, cover crop, mulching and rootstock. Some tannin compounds arise as defense mechanisms to protect the grape as a result of stress, so their Liquid Nitrogen Dosing Systems: Key Benefits: Flushes oxygen out of bottle head space Keeps the fruit in every pour Best "locks in" FSO2 levels 800.371.3303 www.chartdosers.com Dosing The World One Drop At A Time 68 V I NChartDosers WIN E RY MANAGEM ENT 1 E YA R D & HalfPg Wine_2013_VWM.indd Nov - Dec 2013 | 5/15/13v wm m e d i a . c o m w w w. 1:33 PM