Pre-Fermentation Treatments
Tannin Addition
Tannins play a large and important role in the sensory characteristics of wines - interacting in diverse and individual ways, expressing their capacity for protein, oxidative and color stabilization according to their own nature (Section 1.3). The winemaker's principal aim is to create a wine according to the quality and style required and commercial specification. While winemakers recognize there are tannins in grapes, often the level of extracted from the grapes is not sufficient for a particular wine style, so it is common practice to add exogenous tannins.
Commercial Tannins
Commercially available tannin products fall into three categories: anti-laccase tannins, fermentation tannins and cellaring and finishing tannins. The source material for the tannins and the extraction method and composition of the final blended product all contribute to the differentiation of the product, which, in turn, determines its intended application and impact.
Anti-Laccase Tannins
Tannins can play a role in improving wines made with rot-compromised grapes. In wine regions where wet weather during vintage is common, such as Bordeaux, exogenous tannin additions are used for the elimination of the oxidative enzyme laccase (from Botrytis infection) in addition to wine structural considerations.
Fermentation Tannins
Fermentation tannins are also used routinely by some wineries to enhance mouthfeel and stabilize color. Tannins do not add color to the must of low color grapes; however,4the early addition of tannins allows them to bind up available proteins.
Cellaring and Finishing Tannins
ACellaring and finishing tannins are helpful tools when finetuning a wine. Cellaring tannins are used to enhance midpalate structure and aging potential. They can also enhance aroma complexity.
Types of Tannins
Tannins are a structurally diverse group of molecules with quite significant differences, but from a simplified viewpoint we can separate enological tannins into two categories: hydrolyzable tannins (ellagic and gallic) and condensed tannins (catechinic).
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