Federico Casassa,* Emily Stoffel, Taylor Robertson, Chrissilda Brown, Paul Gannet, Marina Tacconi, and Sean Kuster
*Wine & Viticulture Department, California Polytechnic State University, San Luis Obispo, 1 Grand Avenue, San Luis Obispo, CA, 93407 (lcasassa@calpoly.edu)

Grenache wines were made in triplicate fermentations following a factorial combination of fermentation temperatures, ranging from Hot (spike of 34°C), to Cold (10 to 12°C throughout) and an alternation of them (Cold/Hot) with contrasting punch-down regimes (no punch-downs, NO PD; two punch-down/day 12 hrs apart, PD). Cold wines had higher pH and lower titratable acidity. Phenolic and chromatic parameters were largely unaffected by the punch-down regime, but did show differences as a function of fermentation temperature. At pressing, there were 58 and 52% more anthocyanins and 158 and 150% more tannins in Cold/Hot and Hot than in Cold wines, respectively. Small polymeric pigments increased significantly more in Cold/Hot and Hot wines after nine months bottle aging, resulting in higher wine color in these treatments. Additionally, an accelerated aging experiment (seven weeks incubation at 38°C) found these wines were equally impacted by aging: anthocyanins decreased by 90% and polymeric pigments increased almost two-fold (181%). Protein-precipitable tannins also increased during accelerated aging, which led to formation of large polymeric pigments (LPP). From a sensory perspective, fermentation temperature mostly impacted perceived color saturation and hue, while the absence of cap management led to wines with significantly greater reduction and mushroom-like aromas. Wines produced with the Hot fermentation regime had more alcohols such as isobutanol, hexanol, and phenyl-ethanol, while wines produced with the Cold fermentation regime had more ethyl-hexanoate and ethyl-octanoate.

Funding Support: SURP Undergraduate Research Program