Scott Frost, Hildegarde Heymann,* John Blackman, Helene Hopfer, Thomas Collins, Jerry Zweigenbaum, Roger Boulton, Susan Ebeler, and Hildegarde Heymann
*Department of Viticulture and Enology, University of California, Davis, CA 95616 (hheymann@ucdavis.edu)

Cap management and maceration are techniques that manipulate contact between juice and grape solids during winemaking. These practices alter the extraction of phenolic compounds and thus also alter taste and mouthfeel. The effect of four cap management techniques with five postfermentation maceration times was evaluated for phenolic profile and sensory properties. All experiments were conducted in triplicate using Merlot grapes with nine different treatments. Fruit was crushed into 27 200-L fermenters. A three times daily pump-over regime of one juice volume was applied to 18 of the 27 fermenters. At dryness, three of these 18 fermenters were pressed and the remaining 15 fermenters were pressed in groups of three at intervals of one, two, four, six, and eight weeks. Six of the remaining nine fermenters were fitted with a purpose-built wire mesh to submerge the cap into the fermentation. At dryness, three were pressed and three underwent an eight-week maceration and were then pressed. The final three fermenters were punched down three times daily, then pressed when dry. The changes induced by the different winemaking treatments were characterized using instrumental and sensory methods. The sensory profiles of the wines were determined using descriptive analysis (DA) and temporal dominance of sensation (TDS). Hydrophilic interaction chromatography (HILIC) coupled with quadrupole time-of-flight mass detection (qTOF) was used to evaluate the chemical distribution of tannin species. Baseline resolution of proanthocyanidin isomers was achieved, allowing relationships between polymerization and winemaking technique to be observed. Multivariate analysis of the qTOF polyphenol measurements discriminated the nine treatments. Longer maceration times produced proportional increases in specific polyphenol compounds. Extraction patterns and sensory implications will be reported for specific compounds and compound classes.

Funding Support: American Vineyard Foundation, Stephen Sinclair Scott Endowment