Tannins are phenolic compounds present in skins and seeds of grapes. They are responsible for tactile sensations and are perceived as a drying sensation on the mouth and insides of the cheeks. The winemaker works to create a balance of fruit and textural components while minimizing the tannic elements associated with bitterness. Tannin levels vary widely by varietal (Pinot Noir has relatively little tannin, while Cabernet Sauvignon has a lot) and are influenced by the climate in which the grapes are grown.

Grapes grown in cool climates typically feature more muscular tannins, while warm climate grapes tend to have softer tannins that favor earlier drinking. Near the end of the growing cycle, grape tannins can soften – this is highly desirable in cool/mountain climate fruit, but may make warm/valley climate fruit a little too soft. If tannins are too soft, a wine can benefit from a tannin adjustment. Tannins can be added from whole cluster inclusion or adding enological tannins that have been created from grape skins. Note that while oak barrels also add tannin, they tend to impart a “drying” tannin that will stick out unless balanced with enough grape tannin.