Tannins are phenol compounds found in a variety of plants. Their survival strategies in nature produce benefits in wine, food, health and beauty. In human culture they're used in industry like dyeing, tanning and ink making.
In previous centuries, tannins are recognized for biological functions. In history they're used in leather tanning, natural ink, mordant for dye, traditional medicine, incense and resins.
Tannin compounds have strong astringent properties. These affect the taste, color and texture of food and beverages such as wine and tea. In human and other bodies, astringents shrink or tighten tissues.
Naturally occurring polyphenols, or phenol compounds, they can bind to and precipitate proteins, amino acids, and other macromolecules. This property is responsible for their piquant taste.
Tannins are classified into two main categories: hydrolysable tannins and condensed tannins. Hydrolysable tannins can be broken down into smaller molecular units.
Condensed tannins are more complex structures. They're formed by the polymerization of flavonoids.
Tannins are characterized by high molecular weight and ability to chelate metal ions, giving them antioxidant properties. They can form complexes with proteins and other macromolecules.
When tannins bind to proteins they create flavor and texture effects. They can leave a dry or puckering sensation in the mouth, often associated with red wine.
Tannins in Nature
Tannins are synthesized by plants as secondary metabolites, not directly involved in growth or reproduction but with various ecological purposes. The process begins with phenolic compounds.
Phenols are created in the shikimic acid pathways and the phenylpropanoid pathways of plants. When exposed to environmental stresses such as disease or UV radiation, plants intensify tannin production.
Tannins help deter herbivores and protect against pathogens. Oak leaves are bitter to repel insects and acacia trees produce foul-tasting compounds when overgrazed, especially by giraffes.
Acacias also communicate the presence of these threats to other trees of their kind in the vicinity. Based on this information, nearby acacias are producing similar tannins before the giraffes get to them.
In maturation of fruits tannins can regulate the ripening process. This extends the plant's potential for reproduction and generates increased sweetness as the ripe fruit produces more sugars.
This creates another step in the natural process as the sugars catalyze wild yeasts, especially notable in vineyards. These can be used by wine makers to impart subtle flavor layers as a stage in fermentation.
Tannins have antimicrobial, anti-inflammatory, and antiviral benefits. Some tannins are known to have antioxidant effects, helping protect plant cells from oxidative stress.
Tannins are important to ecological interactions. Besides defense, tannins contribute to nutrient cycling. When tannin-rich leaves decompose, like most organic bodies they release nutrients into soil for other consumers.
Plants & Plant Products High in Tannins
Many plants are recognized for their high tannin content. They include:
Tea (Camellia sinensis): Both black and green teas contain significant levels of tannins, contributing to their characteristic flavors.
Red wines: Grapes, particularly tannic varieties like Cabernet Sauvignon and Syrah, are rich in tannins, which enhance the wine's structure and aging potential. Skins, seeds, and stems of grapes are good sources of condensed tannins.
Chestnut (Castanea spp.): The wood and bark of chestnut trees contain high levels of tannins, historically used in tanning leather.
Sumac (Rhus spp.): Many species of sumac are rich in tannins, which have been used in traditional culinary applications. The berries and leaves are used in culinary applications, where their tannin content provides a tart flavor.
Oak Trees (Quercus spp.): The bark, leaves, and acorns are rich in tannins and have historically been used in traditional medicine.
Witch Hazel (Hamamelis virginiana): Botanical astringent. Witch hazel is used to relieve itching, burning and irritation caused by hemorrhoids or bowel movements.
Balsam Fir, Silver Fir: called Tannenbaum or tannin tree in German, it's the most popular Christmas tree, dispersing a fresh woodsy fragrance throughout the house.
Use of Tannins in History and Today
Tannins have been used for centuries by humans. The most well-known application is in leather tanning. Trees such as oak and hemlock are favored for their high tannin content.
In tanning, tannins extracted from tree barks process animal hides, turning them into workable material for clothing, armor and tools. Tannins are also used traditional dyeing practices as mordants and often dyes.
Historically, tannins are used for making ink by mixing them with iron salts, such as iron(II) sulfate. This creates complex, water-soluble blue-black compounds.
Tannins are used in food and beverage production, such as winemaking and brewing. They contribute to complexity of flavors in wines and beers and can influence texture and aging potential.
Beyond culinary uses, tannins have potential health benefits. In herbal medicine, tannin-rich plants have been used for tonic properties and to treat conditions like diarrhea or bleeding.
Tannin compounds from oak galls are a major source of ink in ancient and medieval times. They're also desirable in dyeing. Acorns are bitter to humans, due to tannins. The taste is leached out by prolonged soaking in water.
Tannins are important to the beauty industry. They're included in skincare products for their touted astringent and anti-inflammatory effects.
Facts about Tannins
Tannin Levels Vary: The concentration of tannins in a plant can vary dramatically depending on the growing conditions, maturity, and part of the plant being consumed.
Wine Aging: Tannins in red wine contribute to its aging potential. Wines with higher tannin content are often believed to develop more complex flavors as they mature.
Traditional Medicine: In folk medicine, tannins are given to treat ailments due to their antimicrobial properties. For example, they have been used in remedies for sore throats and gastrointestinal issues.
Non-Fiction Books:
Fiction Books:
READ: Lora Ley Adventures - Germanic Mythology Fiction Series
READ: Reiker For Hire - Victorian Detective Murder Mysteries