Chemical and Sensory Effects of Whole-Cluster and Dried-Stem Additions in Syrah and Tannat Wines from California
Isabelle LoMonaco, Georgia Downes, and L.
Federico Casassa*
*Wine and Viticulture Department – Cal Poly San Luis Obispo, 1
Grand Avenue, San Luis Obispo, CA 93407, San Luis Obispo, CA,
93407 (lcasassa@calpoly.edu)
Syrah (23.5 Brix, pH 3.39, titrable acidity 6.5 g/L and stems comprising 5% of fruit fresh weight) and Tannat grapes (23.3 Brix, pH 3.46, titratable acidity 4.2 g/L and stems comprising 9% of fruit fresh weight) were made into wine by applying three winemaking treatments, in addition to a Control wine, in triplicate fermentations (n = 3): whole-cluster (WC, consisting of 100% whole-cluster fermentation, foot-stomped); green-stem additions (GS, consisting of adding 100% of stems back to the fermentors); and dried-stem additions (DS, consisting of adding 100% of the stems back to the fermentors after treating the stems with heat via a convection oven). Wines were analyzed at the end of alcoholic fermentation and submitted to sensory descriptive analysis after three (Tannat) or six (Syrah) months of bottle aging. A two-way analysis of variance combining both cvs. showed that all treatments increased in pH from 3.71 (Control wines) up to 3.84 (WC wines). In Syrah, WC and GS reduced wine color significantly, while in Tannat, only GS caused significant color reduction. Whereas none of the techniques affected anthocyanins and polymeric pigment formation at pressing, we observed tannin increments relative to Control wines of 67% in DS Tannat wines and of 216% in DS Syrah wines. In Syrah, WC wines enhanced the typicity of this cv. by increasing the perception of smoky, black olives and black pepper aromas, while DS wines were characterized by greater perceived astringency, with a suede-like textural subquality. In Tannat, GS wines showed enhanced vegetal and mint/eucalyptus aromas, while WC wines had an intense chocolate aroma. DS wines were again greater in perceived astringency, with complementary notes of cooked blue fruit aromas and bitterness.
Funding Support: The E&J Gallo winery is thanked for donation of the fruit for this project, as well as logistic support during the harvest and transport of the grapes
