The use of exogenous tannins in winemaking

Karien O’Kennedy - 05 Apr 2016

A wide variety of tannins are available from different suppliers. Even bigger than the variety of trade names are the differences in quality of all the products. These differences in quality are as a result of the origin and the manufacturing process of the tannins. Tannins extracted from grape seeds and grape skins are usually the most expensive, followed by tannins from oak wood. It usually also is the more expensive tannins that are the most effective. It is extremely important that wine cellars make very sure that the tannins they are using have the desired effect.

Benefits of using tannins during fermentation:

The sacrificial effect – after crushing, grape juice is full of proteins. These proteins can bind to grape tannins in the course of fermentation; large complexes are formed that settle after fermentation. In this way the wine therefore loses some of its natural structure. By adding fermentation tannins at crushing, or a few hours after crushing to first allow enzyme functioning to be completed, these commercial tannins bind with grape proteins. As a result, the quantity of proteins that can bind with the natural grape tannins, which usually are only extracted later during fermentation, is reduced. The natural structure therefore is retained. There also is much more grape own tannin available for potential complex formation with anthocyanin.

The anti-oxidative effect – the use of fermentation tannins lowers the concentration of dissolved oxygen in the must. This is a particularly good property if the grapes have been infected with Botrytis and if laccase enzyme is present. Oxidation therefore can be limited to a certain extent.

The co-pigmentation effect – some commercial tannins can form complexes with anthocyanins (polymerise) in the same way that grape tannins can. Anthocyanins that are polymerised are more stable with ageing and also more intensely red.

Benefits of using tannins after fermentation:

  • Promotes mouthfeel and/or wood flavour
  • Softens green flavours
  • Wine finishing before bottling
  • Manipulation of wine style

References:

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