Tannin, as we well know, is a natural substance found in all plants. Some of these, such as chestnut and quebracho trees, contain it in particularly high quantities, making them suitable for tannin extraction. Let’s explore them in detail.
Main raw materials for tannin production
The chestnut tree, a deciduous species, has been cultivated for centuries in Europe, from the Iberian Peninsula to the Caucasus regions. Since ancient Roman times, chestnut trees were valued for three main reasons:
- Their edible fruits, chestnuts, which are nutritious and easily preserved, so much so they were called “the bread of the poor”
- Their durable and versatile wood
- Their extraordinary regenerative ability (shoots), allowing the forest to renew quickly after being cut.
Quebracho, on the other hand, grows in South America, between Argentina, Paraguay, and Brazil. These evergreen trees are famous for their hard and valuable wood. The name “quebracho” comes from the Spanish expression “quiebra-el hacha”, meaning “axe-breaker”. The dark red heart of the trunk is due to the high amount of tannin it contains (up to 20% of the total weight). This makes it perfect for industrial-scale extraction. quebracho trees grow naturally within multi-species forests and the cutting follows a selective thinning management practice.
Tannin production chain
The supply of trunks for industrial tannin extraction is carried out with full respect for local laws for the conservation of forest heritage, preserving it for future generations. Once cut, the trunks are left to season for several months in the open air. They are then reduced to “chips” and subjected to an extraction process similar to the infusion of tea. In the end, liquid tannin is obtained, which can be turned into powder to facilitate global transportation.
Tara is another South American plant particularly rich in tannin. This shrub, belonging to the leguminosae family, produces pods resembling beans. By grinding the pod’s skin you can obtain tannin in powder form, ready to be used in various industrial applications. The seeds of the same fruit are suitable to make tara gum, a popular ingredient in the food industry for making ice cream and meat-based products.
False fruits rich in tannin
Tannin is not only extracted from tree trunks and bark. An important vegetable source is the gallnuts. Categorized as “false fruits” for their misleading appearances, gallnuts contain a remarkable amount of tannin. They are, in fact, outgrowths that form on some plants due to insect stings or egg deposition. Tannin, we remember, has antibacterial and antifungal functions; therefore, these gallnuts represent a plant’s defense reaction to an external attack, with the aim of isolating and protecting the damaged area. These outgrowths mainly form on oaks and are harvested industrially mainly in Turkey and China (hence the references to Turkish gallnuts and Chinese gallnuts).
Other plant sources rich in tannin
Although chestnut, quebracho, tara, and galls are among the primary sources used in the industrial production of tannin, there are other plants with a high concentration of this valuable substance:
- Horse chestnut, often confused with chestnut, originates in the Balkans and western Asia. Known for its ornamental and therapeutic properties, its leaves, fruits, and bark are all rich in tannin.
- Oak was already known to the Celts for its high tannin content. However, oak is rarely used today in tannin production because of its slow regeneration cycle.
- Mimosa, or ccacia, is native to Australia but is also found in South Africa and Latin America. Its bark is rich in tannin.
- Sumac was historically used in traditional medicine as a remedy for gastrointestinal disorders. Its leaves are particularly rich in tannin.
In conclusion, nature provides us with multiple sources of tannin. However, in modern production, those that ensure greater yield while minimizing the environmental impact are preferred, aiming for sustainable production.