Tannin under the microscope

Tannin is a vegetable extract belonging to the family of polyphenols, which are antioxidant substances capable of scavenging the free radicals responsible for cellular aging.

There are currently about 5 thousand molecules classified as polyphenols and they are naturally found in the fruits and vegetables we eat every day.

Tannins can be classified into different groups based on their plant origin and chemical properties, allowing them to be used in various applications, each time with excellent results.

However, they possess certain properties that distinguish them from other polyphenols.

known polyphenols

Tannins, a Unique Group of Polyphenols

Tannins exhibit two unique properties:


  • The ability to bind with animal proteins and stabilize them. This makes fermentation impossible and consequently prevents the decomposition of the hide, which is a by-product of the meat industry. The mechanism with which tannins bind to the collagen proteins in the animal hide during tanning is due to the formation of hydrogen bonds between the phenolic groups of the tannin and the peptide groups of the collagen. It is because of this property that tannins are widely used as tanning agents in the vegetable tanning process.

Tannins: Part of a Large Family

Learning about the chemical structure of tannin is like looking at a family tree, with its different branches and genealogical relationships. There are two types of tannins, classified according to their chemical structure:

Hydrolyzable tannins

“Hydrolyzable” means that, when added to water with weak acids and bases, they break down into sugar (glucose) and free phenolic acids (ellagic or gallic acid). Hydrolyzable tannins are classified into:


  • Gallotannins: are tannins which, upon hydrolysis, release glucose and gallic acid. As the name suggests, these types of tannins are mainly found in plant galls or in the bark of some trees (particularly the Quercus infectoria and the Rhus semialata) and in Tara (Caesalpinia spinosa) pods. To the eye, they are yellowish or white-cream in color, and when tasted, they produce a strong sensation of astringency and a bitter aftertaste.
  • Ellagitannins: are derived from ellagic acid. They are principally found in Oak (Quercus sp.) and Chestnut (Castanea sativa) wood. They are dark brown in color and have a slightly less astringent taste compared to gallotannics. They have an enveloping and intense woody aroma. They can also be present, in smaller quantities, in berries, like blackberries, raspberries, cranberries and strawberries.
Condensed tannins

Also called “flavanols” and, unlike hydrolyzable tannins, they do not break down into smaller molecules when added to water. Although they have a reduced astringent effect when compared to hydrolyzable tannins, they are powerful antioxidants. Condensed tannins are divided into two groups:


  • Proanthocyanidins: formed from an individual unit of anthocyanins, or pigments, which are bound together and may appear blue or red, depending on their plant origin. Anthocyanins impart to the cornflower its blue hue and contribute to the color of autumn leaves. These tannins occur naturally in grapes (Vitis vinifera) and grape seeds; as a result, they are the best “ wine tannins”.
  • Profisetinidins: are composed of various fisetinidin units contained in the wood of different tropical species, particularly the wood of the Quebracho tree (Schinopsis lorentzii).

Each type of tannin is perfectly suited for use in a specific sector, or sometimes in more than one. The principal sectors are:

Vegetable Tanning

Animal Nutrition




Other Applications

Tannins, the “Messengers” of Plants

Tannins are semiochemicals, that is, substances capable of carrying “biological information” useful for the interaction between living organisms in order to evoke physiological and behavioral responses.

This category also includes pheromones, substances secreted by the exocrine glands of animals (including humans) to transmit olfactory “messages” to their own kind (including fear, and therefore the possible presence of danger, and sexual signals).

However, pheromones only trigger responses between members of the same species: tannins, on the other hand, mediate interactions between different species and different Kingdoms (plant and animal), which is why they are also referred to as allelochemicals (from the Greek word allélon, meaning “reciprocally”).

This makes them not only protectors, but also “messengers” of the plant world.

Tannin: a Natural Substance, Safe for Humans and the Environment

Owing to its chemical structure and to its 100% plant-based composition, tannin is a substance that is completely harmless and safe for humans and the environment.

Therefore, in many cases, its is a viable alternative to many synthetic chemical solutions (which although effective, can prove to be invasive or contaminative).

The production of tannin follows rigorous environmental sustainability standards that demand a responsible sourcing of forests, based on strict regulations, the recycling of water used in industrial processes and the optimization of energy resources.

To learn more, go to the dedicated page to discover how the extraction of tannin can help to preserve the delicate balance of Nature and to develop greater social equity by stimulating local economic incentives.

The Beneficial Effects of Tannins

On plants

  • Tannins protect plants from fungal decay, thanks to their capacity to weaken the cellular membrane and inhibit the action of enzymes that attack the cells.
  • They protect them from the effects of oxidation by scavenging free radicals.
  • At high level they act as anti-nutritional deterrents against different species of insects and aphids because of their bitter and astringent taste.

On animals

  • Tannins are used to supplement the diets of farm animals in order to strengthen their immune system and boost their metabolism.
  • This prevents the excessive use of antibiotics and leads to a better quality of life, both in terms of the health and well-being of the animals.
  • A change that has a positive impact on the entire food supply chain and consequently, on humans as well.

On humans

  • The antioxidant activity of tannins helps to protect the body against cellular ageing.
  • According to research carried out by two prestigious universities, it is effective in the fight against bacteria and acts as a balancer of the skin flora of the foot.

The Virtues of Tannin

The chemical properties of tannin make it a unique substance in its class, with benefits not only for humans and animals, but also for the environment. In fact, tannin production helps to protect our forest heritage from abandonment and to promote economic development in mountain and rural areas.