CRUSH

Better destemmers, roller sorters, and optical sorters have increased efficiency and selectivity at the crush pad for those who have the budget. More than ever before, winemakers have tools for selectivity of berry integrity (whole vs. crushed), MOG incorporation (stems, leaves, etc.), and berry quality (size, color density, etc.).

A modern and common practice for cultivars with high phenolic concentrations is to destem the berries without crushing them which has a unique advantage of delaying tannin extraction, but not without tradeoffs. Whereas anthocyanins usually extract within the first five to ten days of maceration, maintaining whole berries delays the extraction of all phenolic compounds. As a result, color extraction coincides with tannin extraction which can be cut short if pressed off early. Alternatively, winemakers concerned about too much tannin can utilize the polarity of anthocyanins to partially extract them via cold soak. Crushing berries allows for the efficient extraction of color from grape skins which is fundamental for the formation of bound anthocyanins. And while efficiency is not always the key to quality, we believe that extracting less color leaves quality on the table. After all, free anthocyanins are finite and unstable whereas tannins are abundant and persist for the life of the wine. Winemakers can also top the processed fruit with a layer of whole clusters to act as a filter for pumpover liquid and slowing tannin extraction. Ultimately, winemakers have a variety of tools fruit processing tools to help direct the resulting wine style. Evaluating these tools through a phenolic lens is a powerful way to assess their respective impacts based on the quality of your fruit.

In addition to berry integrity, balancing oxidation is also very important during crush. Polyphenol oxidase (PPO) and laccase are two major enzymes that dimmish polyphenols in wine (color in particular). Iron-reactive phenolics will also brown in response to oxidation via regenerative polymerization. Exploiting this mechanism is a common tool used in non-aromatic white winemaking to settle out these compounds before fermentation. What looks like Coca-Cola as juice results in a bright, crisp, and clear white wine. While this is a powerful stylistic tool, it is worth considering what is lost with the settled IRPs. Reductive potential, viscosity, acidity, and minerality are all worth considering relative to juice hyperoxidation. While we are still learning about IRP’s contribution to wine’s structure and flavor, we feel there is no better place to explore this than through white wines. IRPs are primarily phenolic acids deriving from grape pulp so flavonols extracted from grape skins and seeds are insignificant. Completely anaerobic conditions and lees contact will prevent IRPs from polymerizing whereas hyperoxidation will settle them out completely. Tracking IRP concentrations as well as browning through the CIELAB color space are two use cases for phenolic profiling in white winemaking.

Finally, it is common practice to make additions at the crusher to improve homogeneity throughout the tank. Sulfur addition is almost ubiquitous whereas other products such as yeasts, nutrients, organic acids, enzymes, sacrificial tannins, and chitosan are increasing in popularity. While these powerful tools are a common luxury for the modern winemaker, it is truly worth reconsidering every addition made into a wine. This is not a case against obstructing wine purity, rather, we focus on the unintended consequences and side effects of adding these products without careful consideration. Winemaking additions can dramatically improve wine quality when applied appropriately. Several examples are reviewed in pre-fermentation.