Also known as "commercial tannins", these are chemical substances obtained by extraction from woods and fruits. A distinction is made between two groups. The grape-derived (flavanoid) tannins obtained from grape seeds or pomace (press residue) are very similar to the natural tannin in red wine. The second group is obtained from fruits such as gall apples or woods such as oak, chestnut or quebracho (trees and shrubs from South America). These are known as wood-borne (hydrolysable) tannins, or ellagic tannins, because they decompose through oxidation and acid hydrolysis to form degradation products such as ellagic acid.
They promote the polymerisation of anthocyanins (colouring agents) into more intensely coloured, sulphur dioxide-stable pigments. Most of the tannins available on the market fall into the group of wood-based tannins. However, the industrial production of such preparations is difficult without impurities. In addition to tannin, other plant-based ingredients such as lignin and cellulose are also extracted from the base products during production. Under certain circumstances, however, these substances can cause undesirable changes in the flavour of the wine.
Application
Oenological tannins are used almost exclusively in the production of red wine for the purpose of colour stability and improving the texture(taste). In some cases, they can also contribute to improving the ageing potential. Tannins can be added at various points in the winemaking process, namely during mash fermentation, after malolactic fermentation (malolactic fermentation ), before barrel ageing or even before bottling.
The effect can vary greatly depending on the point in the production process. The mash treatment tannins (from unseasoned wood) have a more colour-stabilising effect, but only a slight colour-enhancing effect, while the wine treatment tannins (from seasoned, toasted wood) have a harmonising, flavour-enhancing effect. During application, particular care must be taken to ensure a harmonious balance between tannins and anthocyanins. Colour-intensive, low-tannin red wines can also tolerate more tannins. However, light-coloured red wines with a low anthocyanin content will have an inharmonious note.
Wine law requirements
Its use is authorised within the EU without any quantity restrictions. However, this only applies to products in solid or powder form. In liquid form, however, they are prohibited because, in the opinion of the EU Commission, it is relatively difficult to check this and any wine adulteration could be encouraged. Oenological tannins have become the most widely used but not uncontroversial additives. Another form of tannin addition is toasted wood chips (oak chips, staves). These are used as an alternative to barrique ageing. Such methods are used particularly overseas in the vinification of so-called Coca-Cola wines and fruit bombs. Oenological enzymes are another means of influencing wine flavour and quality.
Further information
For the production of alcoholic beverages, see Champagne (sparkling wines), distillation (distillates), spirits (types), winemaking (wines and wine types) and wine law (wine law issues).
Picture left: By Simon A. Eugster - Own work, CC BY 3.0, Link
