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106 WINES&VINES November 2015 WINEMAKING ascertained that many of the dif- ferences initially observed tend to lessen as the wine ages. The ex- traction of tannins from the skin is regulated by the type of interac- tion established with the polysac- charides of the vacuolar membrane or wall. With the use of macera- tion enzymes, a general increase in tannins was observed, along with an increase in polymeric pigments. Pre-fermentation cold macera- tion (preservation at 10°-15° C [50°-59° F] for a few days) does not appear to produce striking results in the case of anthocya- nins, especially for varieties like Pinot Noir and Sangiovese. There is, however, improved extraction in the presence of high levels of SO 2 . The influence of this treatment on the extraction of proanthocy- anidins is linked to the grape va- riety. In the case of Cabernet Sauvignon there is a rise in the level of tannins but a decrease in their average degree of polymer- ization, which could be explained by an increase in the extraction from seeds; in Syrah, meanwhile, the treatment did not show sig- nificant effects. The use of dry ice with partial freezing of the must can produce important effects as it causes the collapse of the cell structures of the berry. Moreover, the carbon dioxide that sublimates creates an atmosphere that protects the must from oxygen. The anthocyanins undergo increases of around 50%, with considerable variability be- tween cultivars. A 2014 study conducted at the University of Turin Department of Agricultural, Fo r e s t r y a n d Fo o d S c i e n c e s showed similar results for the Bar- bera and Nebbiolo varieties, with an enrichment in anthocyanins and a rise in the fraction of malvin derivatives at the expense of less stable anthocyanins. The effect on tannins shows important increases also due to the breaking of the seed cells caused by freezing. Sensory properties The sensations of bitterness (taste) and astringency (tactile) that influence the quality of red wines are associated with poly- phenolic substances, especially flavanols. Astringency is a com- plex of oral sensations that follow the precipitation of salivary pro- teins, which cause a reduction in viscosity and an increased sensa- tion of friction. Both of these sen- sations have been correlated to the concentration and structure of flavanols: Proanthocyanidins are the polymer forms of flavan-3-ols; the number of structural units present defines the degree of po- lymerization (DP), whereas the degree of galloylation (DG) identi- fies the number of units present in the form of gallic acid esters. Bitterness generally diminishes with the increase in the degree of polymerization, therefore the monomers and proanthocyanidin dimers and trimers appear more bitter. Astringency increases with the degree of polymerization (higher for PC in skins than in seeds), with the presence of units with the lateral B-ring trihydroxyl- ate (prodelphinidic units typical of skin flavanols) and with the degree of galloylation (higher in the PC in seeds than in skins). Consequently, skin tannins are c o n s i d e r e d m o r e a s t r i n g e n t (higher average DP), but the DG also should be remembered, as a study conducted in France on Cab- ernet Franc grapes showed that the fractions of PC extracted from ARTICLE FROM IL CORRIERE VINICOLO Editor's note: This article is published as part of Wines & Vines' cooperative editorial effort with Il Corriere Vinicolo, the leading Italian wine industry publication (corrierevinicolo.com). Il Corri- ere Vinicolo is edited by Unione Italiana Vini, the largest Ital- ian wine trade association. On a regular basis, our two publica- tions will share key articles in order to give readers a broader view of important wine industry topics in Italy and North America. DAILY WINE INDUSTRY NEWS winesandvines.com