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November 2015 WINES&VINES 103 WINEMAKING T he sensory qualities of wine are the result of a complex balance between wine components. The polyphenolic component, in particu- lar, distinguishes and influences the quality of red wines. This group of substances determines color, sensory sensations of bitterness and astrin- gency, and forms the structure and body of the wine, with an impact on its longevity. The polyphenolic substances of wines are basically derived from the grapes, where they are contained in the solid parts of the bunch (skins, seeds and stems), as shown in the berry diagram on page 104. For many wine- makers it is common practice to only exploit the solid parts of the berries, removing the stems that could add unpleasant bitter and herbaceous flavors. The term polyphenols indicates various classes of compounds that differ for their chem- ical structure, properties and concentration. The main classes of polyphenolic compounds of red wines and the spectrophotometric indi- ces used to assess them are summarized in the table at the bottom of page 104. The passage of the components from the solid parts (particularly polyphenols) to the liquid phase is not as simple or immediate as that of the solutes in the grape's pulp, neces- sitating an extraction process between different phases as well as contact between the liquid phase and the solid parts. This process is generally referred to as "maceration." To complicate everything, there is also the varied location and the chemical and physical state of polyphenolic substances present in skins or seeds, with substantial differences for the same class of substances. The anthocyanins are located in the vacuoles of cells in the hy- podermis of skins (rarely in the pulp). The proanthocyanidic tannins in skins, contained in the same tissues, represent a highly complex situation, as can be seen in the black and white diagram at the top of page 104. The tannins in seeds are contained in the various layers of cells that make up the external coat. In the seeds, monomer flavanols and oligomer forms are predominant, whereas in the skins we mainly find the polymerized forms. The flava- nols in seeds have higher values of the FRV/ PC ratio than those in skins. The presence and quality of phenolic sub- stances in red wines inevitably requires suit- able work in the vineyard and monitoring in order for the raw material to reach optimal Extracting Phenolics in Red Wine An Italian research team examines sensory properties and how to preserve color By Enzo Cagnasso KEY POINTS Phenolic compounds are very important for red wine quality since they contribute strongly to the color, mouthfeel and longevity. The article explains where anthocyanins and tannins originate in grape bunches and how they are extracted during winemaking processes. The origins of color, astrin- gency and body as they relate to polyphenolic substances are described in technical detail. Periodic punchdowns improve color by increasing contact between juice and grape skins.