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36 p r a c t i c a l w i n e r y & v i n e ya r d J a n U a r y 2 0 1 5 W I N E M A K I N G Foundation (AVF) and the California State University Agricultural Research Institute (CSU-ARI) has been secured and will involve Dr. Hildegarde Heymann at the University of California, Davis. We are currently building a large data set of wines in order to target wines with spe- cific stickiness attributes that can then undergo sensory studies. Wineries that are interested in participating in this study and would like to submit sam- ples for analysis, are encouraged to contact Dr. James Kennedy in the Department of Viticulture & Enology at Fresno State (jaken- nedy@csufresno.edu). Summary This method shows promise with regards to processing decisions that influence tannin composition including grape maturation, pressing, racking, micro- oxygenation, élevage, fining and filtering. The fining trial and exogenous tannin addition experiments in this study show- cased the applicability of this method to practical winemaking scenarios, and current projects including extended mac- eration and additional fining trials. The novel information that this approach captures has the potential to demystify some of the more frustrating issues of tan- Sensory relevance of tannin stickiness Tasting wines with similar tannin con- centrations and different stickiness val- ues – and conversely tasting wines with different tannin concentrations but simi- lar stickiness values has been the focal point of preliminary uncontrolled sen- sory sessions, with promising results. The researchers have worked in col- laboration with winemaking teams in California and found good correlations between analytical values and sensory descriptors, albeit with a limited data set. Conceptualizing the perceptual differ- ence between tannin concentration and stickiness under wine tasting conditions is hypothesized as follows (Figure 5). The concentration of tannin in wine is related to the astringency maximum while stick- iness is related more to its duration. This variation in astringency time-intensity is hypothesized to be related to variations in astringency sub-qualities. Preliminary sensory experiments have shown that tannin stickiness correlates with distinct tactile qualities in wine; however, further more controlled sen- sory studies are required. Linking sen- sory data to these analytical results is the next phase of this research. Funding from the American Vineyard In order to explore the potential appli- cations of this method in a winemaking application, a gelatin fining trial was con- ducted. The results were consistent with prior observations that the gelatin prefer- entially removed higher molecular mass tannins, or stickier tannins. In other words, not only did the concentration of tannin decline, but also the stickiness of the remaining tannin. This finding is in contrast to a dilution experiment where concentration is effected while stickiness is not. A set of wines was analyzed in order to gain insight into the variation of sticki- ness in a set of commercial Bordeaux varietal wines. California wines were sourced directly from the winery and Bordeaux wines were purchased from a wine shop. This data set varied by age and region, and the analytical results are shown in Figure 4. The set of wines showed that tannin concentration and stickiness varied con- siderably and that there was a broad range of stickiness values possible at any given concentration. There was also a poor cor- relation (r = 0.24) when stickiness values were plotted against concentration values, which reinforces the finding that tannin concentration and tannin stickiness are independent and unique variables. C M Y CM MY CY CMY K AACW&VAdDelivery4C48I201401press.pdf 1 12/5/14 1:52 PM