Many people wonder about what exactly tannins are as they are one of the most intriguing components of wine and their meaning is often misunderstood. For most wine lovers, a great wine is more than aromas and flavors and equal importance is given to its texture and structure. Tannins occupy an important place in this experience and their role and sources are such fascinating topics that they deserve to be explored. This article will provide the details of this particular component of wine and will make you have a clearer and more concise idea about this very important ingredient present in food and beverages.
What are tannins?
Tannins are a class of astringent polyphenolic biomolecules, also known as tannic acid, found in the bark of plants, their leaves and fruits, as well as in grains, whose purpose is to protect, preserve and defend the plant. Some foods and beverages such as chocolate, tea, coffee and wine have a high tannin content. Tannins are much more perceptible when consumed from the base element (tea leaves, cocoa, grape varieties) and from different forms of production. For example, a wine aged in oak barrels will not have the same tannin content as one aged in metal barrels.
The environment and light also influence tannin levels. Sunlight is a major determinant of tannin maturity. In the case of grapes, tannins start to be present as soon as the flower becomes a fruit, and then become more mature as the grape changes color, anthocyanins (vacuolar pigments) are also more developed at this stage. As the grape ripens, sugar content increases, while acidity decreases and tannins reach maturity.
Tannins in foods
As mentioned before, some foods and beverages such as chocolate, tea, coffee and wine have a high content of tannins among their components, which may or may not appeal to some more than others.
Tannins in chocolate
While cocoa beans are naturally high in polyphenols, some of these are lost during the chocolate manufacturing process. Also, with the addition of sugar and milk, astringency is reduced in the case of milk chocolates. However, dark chocolate does have a high level of tannins because it contains around 70% pure cocoa.
Tannins in tea
Tea contains tannins, especially black tea, as these are present in the leaves. The level of tannins will depend on the type of tea, black tea is more tannic than all other teas such as green tea. The infusion time and water temperature also influence the level of tannins. The longer the tea is brewed or left to brew and the hotter the water, the more tannic the beverage will become.
Tannins in coffee
Tannins cause the bitter taste, astringency and drying texture of coffee, even more when it does not contain sugar. Like tea, there are different varieties of coffee and each variety has its own level of tannins. If the beans are very fine and the coffee machine is used for a long time, the level of tannins will increase.
Tannins in wine
Tannins in wine come from different sources such as grape skins, seeds and stems. Other sources will depend on the winemaker’s decision on the tannin extraction process or the type of ageing.
White wines contain few tannins because the grapes are not fermented with the skins, but when aged in oak some tannins are extracted from this wooden barrel.
In the case of red wines, tannins are obtained due to the maceration with the skins, which also contributes to the colour. The exchange between grape juice and skin increases the tannin content of red wines. If the maceration is fast, less tannins and colour are released during fermentation and when the maceration takes a longer time, more tannins and a darker colour are released.
In the case of rosé wines, the maceration period is shorter than for red wines, but longer than for white wines, resulting in a wine with a medium colour and astringency.
Tannins from a sensory point of view
Tannins have a taste that causes a different sensation to each person. Bitterness is the natural taste of tannins, but a good bitterness like the one we appreciate in a good espresso coffee or in a dark chocolate with a high percentage of cocoa. The sensation of tannins is astringent and dry, and they are felt in the cheeks, tongue and gums. When the tannins in grapes reach the right maturity, the dryness is less noticeable. On the other hand, if the tannins are too young, wines can be bitter and dry.
Astringency, bitterness, alcohol level and acidity form part of the structure of the wine. They also help balance sweetness and fruitiness, which define its entire structure. Tannins also play an important role in protecting wine from premature oxidation.
Why do tannins dry out the mouth?
Saliva proteins strongly attract tannin molecules. When this happens, saliva cannot properly lubricate the palate resulting in the tissues rubbing against each other, making the palate dry.
Tannins and wine tasting
Texture is used to describe the quality of tannins. When wines contain low or high tannins, they are described as light, medium or full-bodied. Below is a list of vocabulary commonly used in wine tasting to describe tannins.
Tannins have a smooth texture that glides across the palate without residue.
Tannins adhere to the walls of the mouth, it has a dry mouthfeel.
Tannins have a rough and sandy texture and a high level of astringency.
The wine contains a pleasant amount of tannins, perceptible but fine-grained.
It’s a powerful, fleshy and opulent wine.
It is rough and dry with strong color, excessively astringent.
Very firm and tight, young and very tannic vs. soft, mellower tannins after aging.
Tannins and senses
Here are good tips on how you can evaluate the tannin level of a wine by following these steps.
The bright purple and ruby red color of the wine indicates young wines that have not been aged in oak. When wines have a light color, they reveal grape varieties with low tannin content, such as Pinot noir, Gamay and Grenache. Deep garnet red wines, with a strong color, mean that the wines are powerful, rich in tannins and generally aged in barrels. These colors are found in Bordeaux wines, Cabernet Sauvignon from California or Syrah from Australia.
In white wines, tannins may be present if there is contact with wood or grape skins and their color would be an intense golden yellow.
The aromas show the different grape varieties and whether the wine has been aged in wood barrels. If it has not been aged in wood, varieties such as Pinot Noir will have fruity aromas such as cherry, raspberry and strawberry. If, on the other hand, it has been aged in wood, aromas of mushrooms and cloves will be noticeable. Varieties such as Syrah have spicy and black fruit aromas such as plum, blackberry and, when aged in oak, it has a mixture of aromas of tobacco leaves, chocolate, coffee and leather.
Likewise, white wines aged in wood will have aromas of vanilla, toasted nuts and caramel.
Wines with low to high tannin levels are generally described as light, medium and full-bodied. According to the grape variety, astringency and dryness, tannins can have sensations that can be described as silky, grainy or rustic.
The extraction of tannins is done in a simple and natural way. It happens when a part of the plant (usually leaves, stems or fruit skins) is left to macerate in hot water, which diffuses an intense aroma into the air, and this is gradually released into the water in a totally spontaneous way.
In the case of grapes for winemaking, tannins are obtained by fermenting the grape juice together with the seeds, skins and stems during the maceration and fermentation process.For the production of different wines: white, rosé and red, different times are used to obtain the necessary tannins and color.
For white winemaking, winemakers use a crusher and a sieve to remove the stems. After this step, the white grapes are fermented without the skins. However, some winemakers may choose to ferment with the skins to give the wine more complexity. Finally, if the wine is aged in oak barrels, this will add more tannic components.
In the case of red winemaking, in the destemming phase, winemakers may choose to keep them with the stems, which is called whole bunch fermentation. In general, there are some grape varieties such as Gamay or Pinot Noir that are poor in tannins and are sometimes fermented with the stems. However, contact with the skins and maceration are mandatory in all red wines to obtain the characteristic red color. If winemakers want to obtain even more tannins after maceration, then it is best to age the wine in oak barrels. The methods used to extract color and tannins during maceration are explained below.
Tannin extraction methods
When wine is fermented, a reaction is created in which carbon dioxide is released, causing the grape grains and skins to be pushed to the top of the maceration vat, creating a mass that covers the wine juice called must, known as wine cap or pomace. The pomace must always be in contact with the liquid, otherwise it can interrupt maceration and fermentation. To ensure good contact with the pomace cap, different methods are applied: pigeage, remontage and délestage. The choice of extraction methods depends on the tannic profile that the winemaker wishes to achieve.
This is one of the oldest tannin extraction methods. During this process the pomace cap is broken and added back to the fermenting wine. Nowadays, this method is done mechanically, but it used to be done with the feet, a practice that some vineyards still use to produce Oporto wine. Pigeage is a very gentle extraction used in Burgundy, and whose tannins are fine and flexible.
This method consists of removing the liquid wine from the bottom of the vat with a hose and pouring it back to re-wet the pomace cap. This action is carried out several times so that the extraction of tannins is more consistent than with pigeage, as the pomace cap is pushed into the vat. Pumping-over is a good way to introduce oxygen into the must and the style of wine produced is astringent and bitter, intended for aging wines.
In this method, all the fermenting wine is transferred to another tank and the pomace cap and must are kept separately for 2-3 hours. The weight of the pomace cap remains at the bottom of the tank, facilitating the extraction of colors and polyphenols. With this method, the wines are fruity and have silky tannins.
Tannins in oak barrels
There are different materials from which barrels are made for wine aging, among them oak, pine, acacia, etc. Of these, oak is preferred due to its great potential for fermentation and aging of red wines, as it provides aromas of coffee, cocoa and smoky notes, as well as sweet notes of caramel and almonds. These barrels influence the texture and/or aromas of the wine, depending on the size and time of use.
Because the extraction of tannins and aromas from the wood is reduced after each use, new barrels influence the aromas and tannins more than used barrels.
French barrel vs. American barrel
The degree of tannins in French oak is tighter than in American oak. French oak produces more subtle wines with polished tannins. Finally, American barrels tend to be more powerful in flavor.
The barrel size where the wine is deposited and the length of time it has been in the barrel are important for the tannins. If the barrel is new and small, the influence on the texture of the wine will be greater than a not so new and larger one. A 225-liter barrel will have more impact than a 500-liter barrel, since a higher percentage of the wine will be in contact with the wood. When it is a barrel that has been used several times before, the effect will be softer, but this will also depend on the aging time of the wine.
Barrel and grape varieties
Depending on the grape varieties and the style of wine to be obtained, the right type of barrel needed for these objectives will be used. Some grape varieties should age or age better in new or used barrels depending on the case. The following are the best barrel options to use for each grape variety.
California Chardonnay – new barrel: allows for maximum extraction of tannins and nutty, vanilla flavors.
Chablis – used barrel: allows the fruit to express itself with soft tannins.
Red Bordeaux – new barrel: allows tannic wines, Bordeaux is destined to be aged in bottles for years. The tannins contribute to the longevity and structure of the wine.
Pinot Noir – used barrels: allows wines to be less tannic as this delicate grape requires integrated tannins with pure aromas.
Red Rioja – new and used barrels: depending on the Crianza or Gran Reserva appellation, a minimum ageing time is required. The Gran Reserva must be aged for at least 2 years if the winemaker chooses to use new barrels. This is generally the time necessary to reach the correct tannin level.
Effects of tannins on health
Tannins could be considered undesirable from a nutritional point of view because they lower proteins, inhibit digestive enzymes and affect the use of vitamins and minerals. However, tannins have a high antioxidant capacity. Studies have shown that tannins have many beneficial effects such as blood pressure regulation, cancer prevention, treatment of cardiovascular diseases and control of cholesterol levels that can make wine consumption healthy to some extent as long as it is not abused due to alcohol content.
Possible side effects
Studies have shown that tannins interfere with iron absorption. Tannins bind to iron in plant foods, making it unavailable for digestion. This can be a problem for people with iron deficiency.
Which wines have more tannins?
The level of tannins may be the reason why you like or dislike a particular grape or wine. Tannins condition the wine in terms of flavor, aroma and sensations on the palate as they give it a taste that highlights its acidity, bitterness or dryness.
Likewise, winemaking techniques also have a great impact on tannins, but the tannins naturally present in the grapes will play a more important role in the final amount of tannins in the wine. Below is a table of tannic grapes from least to most.
The Gamay grape is the least tannic of all the red grape varieties known in the world. This fruity red grape variety is the most harvested and emblematic grape of the Beaujolais region of France. The wines produced from this grape are naturally acidic, light in both color and tannins, excellent to be enjoyed while young and flattering to be served relatively fresh.
There are traditional techniques used in the vinification of Beaujolais Crus such as at Moulin à Vent, Morgon, Juliénas, where whole bunches are fermented in open barrels and then aged in small oak casks, which will have an impact on the wine’s quality, with deeper color, more tannins and a longer aging.
Pinot Noir is described as the most difficult grape to grow and make due to its sensitivity to climate change and oxidation risks that make it a risky grape for winemakers. But these oenological challenges make Pinot Noir the most fascinating and expensive wines in the world. Its low level of tannins makes it a smooth wine highly appreciated by wine lovers.
This grape variety is dominant in central Italy, especially in the Chianti region. Wines made from Sangiovese are described as dry, light, medium-bodied reds with mouthwatering acidity and firm tannins.
Malbec is the flagship wine of the great Argentine red wines. It has a low acid flavor and is slightly less tannic than Cabernet Sauvignon. Malbec produces a silky mouthfeel, similar to a melted chocolate cake.
Syrah, Merlot and Cabernet Sauvignon grapes are varieties known for producing full-bodied, tannic wines. Wines made from Syrah are versatile. A tannic but elegant Syrah wine is produced in the Northern Rhône region of France, while Syrahs from California and Australia are bold, tannic wines.
Merlot and Cabernet Sauvignon
Merlot and Cabernet Sauvignon wines are very similar in taste and texture. Merlot has aromas of black currant, blackberry and dark chocolate while Cabernet Sauvignon also has extra aromas of green tobacco and dried mint. Roundness and less tannin levels differentiate Merlot from Cabernet Sauvignon. Cabernet Sauvignon is one of the most tannic of the major grape varieties, and has been the subject of tannin and ripening studies. The rich and structured tannin content of Merlot and Cabernet Sauvignon gives rise to Bordeaux wines with great aging capacity, such as the prestigious Chateau Margaux from the Médoc and Chateau Pétrus from Pomerol.
Pairing High Tannin Wine
It should not be forgotten that the perception of tannins can be modified by food. Intense and high-tannin wines, due to their astringency, combine very well with fatty foods, just as low-tannin wines go well with soups, desserts, salads, etc.
Always remember, however, that food and wine pairing is essentially a matter of taste. In the end, everything will depend on your own experience and tastes combining flavors, textures and aromas.
In conclusion, we can say that tannins are important components of wine both in sensory terms and color stability. You can enjoy wines with a high level of tannins, such as Cabernet Sauvignon, depending on your personal preferences, or you may prefer a wine with light tannins such as Gamay. In both cases, the level of tannins will be judged according to the grape variety, which is the main source of tannins, and then according to the winemaking techniques (the place and time of aging).