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w w w. v w m m e d i a . c o m S e p t - O c t 2 015 | V I N E YA R D & W I N E RY M A N A G E M E N T 6 5 red wines, but they aren't stable, and in a finished wine most will be either joined to tannins to form pig- mented polymers, or joined to other phenolics or aldehydes to form a n t h o c y a n i n - d e r i v e d p i g m e n t s . Most of the pigmented polymer for- mation occurs during fermentation, but according to some reports, by the end of fermentation about 25% of the anthocyanins are thought to be complexed with tannins. Traditional assays for looking at phenolics in wine are complicated and require some fairly serious lab work. But researchers at UC Davis made a breakthrough in 1999 when they developed a quicker, less expensive measurement of pheno- lics called the Harbertson-Adams assay. It was designed so that well- equipped winery laboratories could carry out an assay that would give an objective measure of a wine's color and astringency, telling wine- makers something about exactly which phenolic compounds the wine has. It's a fairly robust assay that m e a s u r e s a n t h o c y a n i n s , s m a l l and large polymeric pigments (the boundary here is five molecules in length), total tannins and non- tannin phenols. The problem with this assay is that although it is rela- tively rapid compared with older techniques, it isn't all that fast and isn't practical for many wineries. In the middle of harvest, something faster is needed, and this is where WineXRay comes in. T h e c o n c e p t b e h i n d t h e WineXRay is to use a rapid, easy measurement – in this case made by an ultraviolet-visible spectrum spectrophotometer (UV-vis) – and then correlate the spectral data taken from wine samples with data fine-tune the correlation between the chemical data and the spectral information. The result of this work is called VESUVVIO, the company's proprietary analytical system. Using this product, any winery with a spectrophotometer can get results on the phenolic composition of its juice, fermenting must or wine in a matter of minutes. "We developed and validated our own models – i.e., calibra- tions – based on various multivari- ate technologies, both linear and nonlinear, that I have used for the last 20 to 25 years in other areas of the process industries, includ- ing plastics manufacturing, oil and gas, pharmaceuticals and biotech- nology, and even food and bev- erage processes," explained Dr. Gianni Colantuoni, who co-found- ed WineXRay in Napa, Calif., with winemaker Scott McLeod. "The key factor in the develop- ment, validation and deployment of the calibrations is their precision," Colantuoni said. "We have insisted on single-digit precision (RMSE- based) and have accomplished this obtained using laboratory measure- ments. This was initially developed by two UC Davis researchers, Roger Boulton and Kirsten Skoger- son, whose model is available online: http://boulton.ucdavis.edu/ uv-vis/Model.htm. All you need to do is to take a wine sample, dilute it, and generate a UV-vis spectrum in the range 230–900 nm using a spectrophotometer. Then you plug the data into the free Excel spreadsheet they provide, and get information on the same phenolic parameters as measured in the Har- bertson-Adams assay. However, the Skogerson-Boul- ton model has not been fully vali- dated, and is intended solely to demonstrate the potential of UV- visible spectra to predict phenolic parameters in wine. ROBUST PREDICTIVE MODEL What WineXRay has done is to develop a similar predictive model, and then make it robust by run- ning 7,500 chemical analyses on wine, using this information to Grapevine Disease Testing and Diagnosis AL&L Crop Solutions, Inc Plant Disease Diagnostic Laboratory We are always here to help you! www. allcropsolu,ons.com (530) 387 3270 and (707) 693 3050 info@allcropsolu,ons.com 7769 N. Meridian Rd., Vacaville, CA 95688 Grapevine viruses including Red Blotch, Fungal diseases, Pierce's Disease, Agrobacterium