Federico Casassa,* Isabelle LoMonaco, Marcel Velasco, and Dimos Papageorgas
*Wine and Viticulture Department, Cal Poly San Luis Obispo, 1 Grand Avenue,  San Luis Obispo, CA, 93407 (lcasassa@calpoly.edu)

Cabernet Sauvignon (clone 7) from the Paso Robles AVA was processed with a contrasting array of punch-down frequencies, ranging from zero to four punch-downs/day, over two vintages (2019 and 2020). In one vintage, fruit was harvested at two contrasting maturity levels. The only variable was the frequency of punch-down, with temperature and other variables kept constant within treatments. Wines were followed for up to three years of bottle aging for basic and phenolic chemistry, and the late-harvest wines of 2020 were subjected to sensory analysis. There were no effects of punch-down frequency on alcohol, pH, titratable acidity, or lactic acid. This is likely because all the wines, irrespective of punch-down frequency, were submitted to very similar temperature regimes. There was a rather unremarkable effect of punch-down frequency on the basic phenolic composition of the wines, including anthocyanins, tannins, and polymeric pigments. These results counter empirical winemaking observations, whereby more frequent physical mixing should lead to higher phenolic extraction. It is possible that more frequent mixing may lead to phenolic losses due to chemical and/or enzymatic oxidations. Such losses may be minimized under conditions of no mixing, akin to wines made with no cap management. In fermentors of relatively small volume (60 L) and at high fermentation temperature, convection movements may allow for sufficient phenolic extraction. This may extend to fermenters up to 1.5 tons; however, reduction aromas may concomitantly appear as well under such conditions. Sensory results indicated that all four wines, irrespective of punch-down frequency, were perceived as drying. While other subqualities of astringency changed little as a function of the treatments, the perception of bitterness increased concomitantly with the frequency of punch-downs, with 3 punch-down wines showing the greatest bitterness perception.

Funding Support: Agricultural Research Institute (ARI)