Understanding Tannins and Their Role in Food and Drink

What are Tannins?

Tannins are a class of chemical compounds that can be found in many plants, including most tree bark and woody plants. The word 'tannin' comes from tanning, which refers to the tanning of animal hides into leather. When tanning animal hides, tannins help stabilize and convert the animal protein collagen into leather by cross-linking the collagen fibers. Tannins also act as a natural defense mechanism in plants against predators such as insects. In food and drinks, tannins play an important role in adding bitterness, along with imparting color and assisting in antioxidant activity.



Types of Tannins

There are two main types of Tannin- hydrolysable tannins and condensed tannins. Hydrolysable tannins can be broken down into sugar and gallic acid residues when treated with strong acids or bases. Common examples of hydrolysable tannins are gallotannins and ellagitannins, which are found in oak, persimmon, and strawberry. Condensed tannins are polymers of flavan-3-ols or flavan-3,4-diols that are linked together, forming bigger molecules. They are also called proanthocyanidins and are found in grape seeds, red wine, cherries, blackberries, and blueberries.



Role of Tannins in Wine

Tannins play a major role in red wine for developing flavor as well as forming the color intensity. The main sources of tannins in red wine come from the skin, seeds, and stems of red grapes. During winemaking, extended maceration or skin contact between grape skins and juice allows more tannins to be extracted into the wine. Condensed tannins from grape seeds and stems contribute tannins as well. Tannins prevent oxidation of wine and help bind pigments together, creating depth and longevity of color. As red wines age, tannins soften or precipitate out, smoothing the wine's character.



Tannins and Cocoa Beans

Cocoa beans, the raw material for making chocolate, contain large amounts of condensed tannins in their shells or husks. During fermentation and drying of cocoa beans, tannins leach out of the husks into the nib or inner part of the bean. This process is important in developing flavor precursors in the beans. However, excess tannins can make chocolate very astringent and bitter. Cocoa processors find ways to reduce tannin levels through sorting, fermenting, and roasting techniques. Remaining tannins contribute to the complex, long-lasting flavors in chocolate.



Role in Tea

Tea contains three major groups of active compounds - flavonoids, amino acids, and tannins. Next to water, tannins are often the largest constituent in tea. They assist in astringency and bitterness in brewed tea. During fermentation of the tea leaves, made from the plant Camellia sinensis, enzymes convert non-tannin compounds into tannins, influencing the taste of the finished tea. Black teas contain more tannins than green or white teas due to their greater degree of fermentation. Tannins help provide body as well as protect against free radical formation when drinking tea.



Impact on Food

Tannins can affect foods as well as beverages. While their astringent nature provides benefits like antibacterial and antiviral properties, high levels of tannins can negatively impact some foods. For example, tannins from unpeeled or damaged apples can cause browning in applesauce or pie filling if not stabilized. Canned beans retain more flavor when soaked to remove tannins before canning. Grapes and other fruits used for jams may require pretreatments to remove tannins if a jelly-like set is desired. However, small amounts of tannins can increase nutrition by binding to and precipitating proteins in the lower GI tract of the body.



Contribution to Health

Beyond flavor effects, tannins may confer health benefits when consumed from food or beverages like wine, tea, and chocolate in moderation. Research suggests tannins exhibit antioxidant and anticancer activities by inhibiting enzymatic and non-enzymatic lipid peroxidation. Studies show higher consumption of proanthocyanidins from berries, grapes, and wine may help reduce the risk of heart disease. Condensed tannins from cocoa contain epicatechin, which has cardioprotective properties. Moderate tannin intake may also benefit gut, skin, and bone health. However, very high levels can potentially inhibit absorption of iron and other minerals when consumed in large amounts.



Assessing Tannin Levels

Since bitterness from tannins is caused by their astringency, knowing tannin levels helps explain characteristics in wine, tea, and chocolate. Simple tests can quantify them. For wine, protein assays determine tannin concentration and provide predictions on long-term structure and ageability. Wine tannin tests help evaluate extraction aspects during fermentation as well. Other methods include protein precipitation tests to gauge astringency levels. Understanding tannins through analysis aids quality control for various foods and drinks while suggesting dietary contributors to potential health advantages when part of a balanced diet.

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About Author:

Ravina Pandya, Content Writer, has a strong foothold in the market research industry. She specializes in writing well-researched articles from different industries, including food and beverages, information and technology, healthcare, chemical and materials, etc. (https://www.linkedin.com/in/ravina-pandya-1a3984191)