How to extract tannin?
If you have read the page “Tannin in Nature“, you know that tannin is contained in all plant species and that carries out a protective action against the attack of fungi and bacteria.
But in order to be part of your life, tannin needs to undergo a transformation, to leave its vegetable “home” and become a pure vegetable extract.
Now you may think about tannin extraction process as something very complex.
Perhaps you imagine big laboratories closed in glass buildings, latest generation computers, scientists in white coats mixing chemicals in big tanks.
Reality is very far from this image.
As a matter of fact, the basic process for extracting tannin from the vegetable raw materials is still the same since centuries ago. And it is incredibly simple.
Tannin Extraction Process: a True Infusion
Imagine the preparation of an infusion, as it could be tea. The leaves of Camellia sinensis are left to be infused, in hot water, and the tea is released slowly.
The same thing happens for tannin. For example, in the production of Chestnut or Quebracho tannin, the wood is shredded and left to macerate in hot water, releasing an intense aroma. The tannin gets transferred to this surrounding water in a completely spontaneous way.
There is no need to force this process, since it happens naturally and it does not need any chemical additives.
When all the tannin is released in the water, we are already in the presence of a natural extract ready to be used in liquid form.
Tannin Industrial Extraction
Tannin industrial extraction has been perfected over the years, adding steps to optimize the extraction yield, for better energy efficiency and resources optimization.
Tannin factories are usually found outside the cities, close to the forests, with which they live in close symbiosis, and near water sources, such as rivers or lakes (to learn more about the eco-sustainability of tannin extraction processes, visit the page Tannin: Ecology and Sustainability).
Let’s discover together how to extract tannin taking for example a “classic” procedure: the extraction of tannin from wood. It could be, for instance, Chestnut or Quebracho Wood.
The extraction of tannin from wood, step by step
1-Resting the lumber
The trunks, which derive from sustainable forest management and in compliance with local forestry legislation, are piled up and left to rest in the open air. This period will allow the wood to be processed more easily.
2-From the Trunk to the "Chips"
The wooden trunks are debarked and shredded in small pieces called "chips". The aim is to expose the largest possible surface to water, to facilitate the release of tannin.
3-The extraction
The wood chips are loaded in big autoclaves with hot water over 100°C. The parameters can change depending on the type of wood used. The tannin extraction process requires only hot water, without the addition of any chemical additive.
4-The wood cycle
After the extraction, the exhausted wood, free from tannin, can find two different applications; it can go to biomass thermal power stations to produce energy, or it can undergo an extrusion process to be transformed into 100% natural pellet for stoves.
5-Purification of Crude Extract
The aqueous solution of tannin is then cooled down to room temperature to precipitate the non-completely soluble substances and impurities contained in the raw material. The tannin is then purified and processed according to the final destination of use.
6-From Liquid to Powder
Liquid, concentrated tannin is ready to be used and could be commercialised as it is. However, to facilitate its transportion, storage and usability, it can be turned into powder through a spray-drying process.
7-The water cycle
The water vapour deriving from the drying process is not be lost, but it is recovered by condensation and re-entered in the production cycle.
8-Packing and Shipping
The tannin is ready to be packed and shipped. Its destinations can be various: tanneries, food and beverage companies, pharmaceutical and cosmetic industries, producers of feedstuffs but also producers of corrugated cardboard, paints and inks, as well as players of the mining industry.
Tannin in Wine
There is a production process in which tannin plays a fundamental role, although no extraction is needed. It is about the production of wines, in particular of red wine. Tannin is already naturally present in the grape. During the ageing period, the wood of the barrels also releases its tannin in the wine, contributing decisively to determine its aroma and taste. That is why sometimes we talk about “wine tannins” or “tannic wine”. On the other hand, from a chemical point of view, the ageing of wine in a barrel is nothing more than an extraction with water and alcohol (wine) of the tannin present in the oak wood of the barrels.