Tannins And Aroma: The Science Behind Wine's Complex Bouquet

Tannins are naturally occurring chemical compounds found in many plants, including grape skins, stems, and seeds. They are classified as phenolic compounds or polyphenols and are derived from phenolic acids. While tannins do not have a distinct aroma, they contribute to the mouthfeel and structure of wine, binding with saliva proteins and creating a dry, puckering, or astringent sensation in the mouth. This characteristic of tannins is utilized in the wine-making process to add structure and body, particularly to red wines.

Tannins are a type of bitter and astringent chemical compound

Tannins are naturally occurring and found in many plants, including grape skins, stems, and seeds. They are also found in foods and beverages like coffee, tea, dark chocolate, walnuts, cinnamon, pomegranates, açaí berries, and wine. In plants, tannins act as a defence mechanism against animals and insects. For example, tannins in fruit prevent animals from eating them before they are ripe.

The word "tannin" comes from the old German word "tanna", meaning oak. This refers to the use of wood tannins derived from oak trees in the ancient process of converting animal hides into leather, known as tanning. The Chinese, Greeks, and Romans all historically used formulations of plant tannins in this way.

Tannins are also used in photography, as mordants in dyeing, and as astringents in medicine. In medicine, tannins are used as astringents to tighten pores and draw out liquids. For example, witch hazel, a source of tannin, is used in skincare products and to treat bee stings, skin abrasions, and poison oak and ivy.

Tannins in wine contribute to its texture, balance, and structure. They interact with proteins in the mouth to create a sense of viscosity or mouthfeel. The astringent taste of tannins is caused by their tendency to bind with saliva proteins, resulting in a dry, puckering sensation on the tongue. While some people enjoy the mouthfeel of tannic wines, others may find it excessively harsh.

Tannins can be described through the tactile sensations they produce, such as mouthfeel, rather than aroma or flavour. They can be soft, velvety, and silky, or coarse, grainy, and chalky. The nature of tannins is closely linked to the grapes' maturation at harvest and will mirror the wine's fruit profile.

Tannins are found in many plants, seeds, leaves, flowers, and woods

Tannins are phenolic compounds found in many plants, seeds, leaves, flowers, and woods. They are known for their astringent properties and are used in various applications, including leather tanning, dyeing, and winemaking.

In plants, tannins are commonly found in the bark, wood, leaves, buds, stems, fruits, seeds, roots, and plant galls. They play a protective role, defending the plants against bacteria, fungi, and herbivores. For example, tannins in the bark of trees prevent bacterial and fungal infections by precipitating the enzymes and proteins that these organisms produce.

Seeds from 63 out of 195 tropical plant species were found to contain tannins. These seeds had varying levels of protein precipitation capacity and oxidative activity due to different types of phenolic compounds.

Leaves with high tannin content include those from coniferous trees, such as decomposing conifer needles, which leach tannins into streams, giving them a brown colour resembling tea.

Flowers also contain tannins, which contribute to their enchanting colours. For example, the subtle yellow-browns, reddish-browns, and scarlet colours of autumn oak leaves are a result of tannins.

Woods with high tannin content include oak and chestnut, which have traditionally been used for tanning leather due to their high levels of tannic acid. Other sources of tannins for tanning include willows (Salix spp.), quebracho (Scinopsis balansae), sumac (Rhus spp.), maples (Acer spp.), wattle (Acacia spp.), eucalyptus (Eucalyptus spp.), and red mangrove (Rhizophora spp.).

They bind with proteins, cellulose, starches, and minerals

Tannins are large molecules that bind with proteins, cellulose, starches, and minerals. These substances are insoluble and resistant to decomposition.

Tannins are derived from phenolic acids and are classified as phenolic compounds. They are found in many plant species from all climates and parts of the globe. They occur in the bark, wood, leaves, buds, stems, fruits, seeds, roots, and galls of plants.

The word "tannin" comes from the old German word "tanna," meaning oak, as oak trees were historically used to convert animal hides into leather. The term also refers to the use of oak bark in tanning animal hides.

Tannins have a unique ability to bind with other molecules, especially proteins, causing them to precipitate. This property is the basis of leather production, where animal hides are treated with tree barks to change their structure.

In plants, tannins serve protective functions. For example, tannins in buds protect the inner leaves from being eaten, while tannins in bark protect trees from fungal or bacterial infections. Similarly, tannins in fruit make them unpalatable to animals before they are ripe.

Tannins are responsible for the astringent and bitter taste in various foods and beverages, including dark chocolate, walnuts, cinnamon, pomegranates, tea, coffee, and wine. In wine, tannins come from grape seeds, skins, stems, oak, and additives. They contribute to the wine's structure, body, and mouthfeel. The astringent taste is caused by tannins binding with saliva proteins, resulting in a dry, puckering sensation on the tongue.

Tannins are used in photography, dyeing, and medicine

Photography

Tannins are used in photography, although it is unclear exactly how.

Dyeing

Tannins are used as a mordant in the dyeing process. Mordants are substances that enhance the fixation of dye onto fibres. They can alter the colour, increase lightfastness, and improve the 'washfastness' of the dyed material. Tannins are excellent dyestuffs in their own right, but they are also important for preparing cellulose fibres in a way that helps them soak up colours better. They assist during the mordanting stage of cellulose fibres. For example, alum doesn't bond very well with cellulose fibres, but once treated with tannin, alum will combine with the tannin-fibre complex.

Tannins can be divided into three categories: gallic, ellagic, and catechic tannins. Gallic tannins are clear and don't add much colour to the fabric. Ellagic tannins tend to add a yellow colour to the fabric. Catechic tannins tend to add brown and/or reddish colour to the fabric.

Medicine

Tannins are astringents that tighten pores and draw out liquids. They are used in skincare products, mouthwashes, eyewashes, and treatments for some bowel conditions. Medical research has shown that tannin found in cranberries is highly effective in preventing urinary tract infections by preventing E. coli bacteria from adhering to the walls of the urinary tract. Similarly, this anti-adhesive property may reduce the ability of H. pylori to cause stomach ulcers. Recent medical research has also shown that these polyphenolic compounds can also reduce LDL cholesterol and improve cardiac health.

Tannins are responsible for the structure and body of red wines

Tannins are a type of bitter and astringent chemical compound that occurs naturally in many plants, including grape skin, seeds, and stems. They are derived from phenolic compounds or polyphenols, which are macromolecules composed of complex hydrogen and oxygen bonds.

Tannins play a crucial role in winemaking, particularly in red wines. They are responsible for the structure and body of red wines, providing a sense of viscosity or mouthfeel. This mouthfeel is a result of the interaction between tannins and proteins in the mouth, creating a dry and puckering sensation on the tongue. The astringent taste of tannins is more prominent in younger red wines and tends to soften as the wine ages.

The amount of tannins in red wine depends on various factors, including the grape variety, growing conditions, and winemaking practices. Grape farmers and winemakers must carefully consider these factors to influence the tannins in their wine.

In summary, tannins are essential in winemaking as they contribute to the overall structure, body, and mouthfeel of red wines. Their interaction with proteins in the mouth creates a unique sensory experience, making them an important aspect of wine appreciation.

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