How do tannins affect the flavour of wine?

Some types of red wine make your mouth feel ‘dry’ when you drink them. New research into why this happens finds out why tannins affect the flavour of different wine types.

The character and quantity of red wine tannins are often affected by different factors. These include how thick the grape skin is, the climate of the growing season and how the wine is cellar stored.


Different wine types affected by tannins

Researchers have published their findings in the latest issue of the Journal of Agricultural and Food Chemistry regarding the effect of tannins. They show that the tannins in Cabernet Sauvignon, for example, are more numerous, contain more pigment and are physically larger than the tannins in Pinot Noir.

They experimented by extracting tannins from a Pinot Noir and a Cabernet Sauvignon and discovered that tannins from Cabernet form more protein in saliva. This backs up previous research that shows wine can cause a dry mouth sensation when proteins in tannins and saliva interact.


What are wine tannins?

Tannin is a polyphenol that appears naturally in plants, wood, leaves, seeds, bark and, of course, fruit skins. In wine, tannins add astringency, bitterness and complexity of flavours.

Wine tannins are usually present in red wines however it is possible for tannins to be present in white wines if they are oak aged. Tannin is dry and tasted in the front part of the mouth as well as the middle of the tongue. An easy example to try of pure tannin is in unsweetened black tea.

Tannins in wine come from either the grapes or the wood of the barrels it’s aged or stored in. Grape tannins are in the stems, skins and seeds of the grape, and as red wines have more contact with the skin there is more time for tannins to dissolve in the liquid. On the other hand, wood tannins dissolve in wine if they are in contact with the liquid.

Examples of red wines that are high in tannins include Petite Sirah, Monastrell, Nebbiolo and Cabernet Sauvignon. Lower tannin wines include Zinfandel, Grenache and Pinot Noir, which is why the researchers used Cabernet Sauvignon and Pinot Noir to discover more about tannins.


Different factors affect wine taste

The researchers also found that tannins don’t make these changes happen on their own. Other factors within wine affect the tannins and how they affect the flavour and taste of the wine.

In the article, the team of researchers say: “When the opposite type of tannin was put into Cabernet or Pinot wines, the sensory panellists could not detect differences in dryness. For example, when Cabernet tannins were added to a Pinot wine, the drink appeared to have the same dryness as the original Pinot.”

They also point out that aromas from the wines would also have influenced the test panellists’ perception of the flavour of the wine.


Figures show 2018 was a very good year for wine harvests

Figures from the International Organisation of Vine and Wine (OIV) show that 2018 was a record-breaking year for global wine production. While 2017 was disappointing, with a small production due to adverse weather conditions, last year recovered to produce 293 million hectolitres globally.

Europe remains the biggest producer by a long way. The continent was responsible for the production of almost 70% of the total amount produced in 2018.

Why was 2018 a good year for wine harvests?

The world’s wine production increased to almost 293 million hectolitres last year. This is the biggest wine harvest since 2004, showing a large increase of almost 43 million hectolitres from 2017.

However, it should be remembered that the extreme weather in 2017 led to the smallest wine harvest for two decades. The bounce-back for 2018 was helped by the global vineyard surface area remaining the same size at 7.4 million hectares. More favourable weather conditions for growing also contributed to the increase in global wine production.

The biggest wine producers are still France, Italy and Spain who all increased their wine harvest production by around 24%. Most other European countries produced significantly more than in 2017 as well.

Wine production remains stable

The European Union (EU) produced 62% of the total in 2018, which is equal to 181.9 million hectolitres. However, the EU’s share is declining due to its more restrictive regulations making it trickier to plant new vineyards.

Outside of Europe, key wine producing countries include Australia, Chile, Argentina and America. Around 22% of the world’s wine production comes from these New World countries.

Other significant countries for wine production growth include China, Mexico and New Zealand. China is now the second largest grower of grapes in the world but doesn’t produce much wine in relative terms. Mexico increased its vineyards space to 34000 hectares, which is approximately the same size as Champagne in France.

How much wine is drunk every year?

The global consumption of wine is estimated at about 246 million hectolitres. This has been relatively stable since 2009 after a period of intense year-on-year growth. The US is the largest market for wine and has been since 2011 at 33 million hectolitres consumed.

China is the fifth largest wine market in the world at 18 million hectolitres, which marks a decrease of more than 6.5%. While consumption of wine in China has been rapidly increasing since 2000, last year represents a decline. Whether this is a temporary decline, or the beginning of a dramatic slide in wine consumption remains to be seen.

Is it all over for traditional food and wine pairing?

Everyone knows that red wine goes with steak, and white with fish. These are the traditional food and wine matching rules that have been around for decades. However, Master of Wine Tim Hanni says that pairing of food and wine in this way is “pseudo-science”.

The American wine expert says: “A perfect wine pairing doesn’t exist. We’re doing a lot of damage in the way we’re matching wine and categorising it. We need to stop wine and food pairing.”

History of food and wine pairing

Historical records show that wine has long been served as a food accompaniment. Its early history also shows that wine was served in place of water, due to the latter’s unsanitary condition. At this time, there isn’t much evidence to show that there were strict wine and food pairing rules.

As culinary traditions developed throughout the world, so did wine-making. The kinds of wine pairings we consider ‘classic’, came from the relationship between a region’s food and the wine they make. For example, many leading wine regions in Europe had lamb as a staple meat. This leads to red wines from regions such as Rioja, Greece, Bordeaux, the Rhone and Provence being considered a classic pairing with lamb.

Old ideas have survived, including the adage “White wine with fish; Red wine with meat”. Its exact origins are unclear, but it’s been given as advice for centuries. The root of this is the idea of matching the body (or weight) of the wine with the weight of the food. The heavier the food (for example, meat), the heavier and therefore ‘red’ the wine should be.

Modern food and wine pairing

In more recent years, there has been much focus on food and wine pairings. The rules have expanded and interest in pairing wine increased. Sommeliers in restaurants exist to instruct on the perfect pairings with the establishment’s food.

This kind of interest started in the 1980s in the US, when the wine industry began advertising its products as a key part of the dining experience. Previously, they have been marketed simply as an alcoholic drink for consumption. Winemakers started to emphasise the foods their wines would go with and the media ran with the idea.

These days, you can find advice all over the place for the perfect food and wine pairing. And it looks as though the strictness of the traditional rules is relaxing. Many wine buyers and drinkers go with their instinct or choose what they like the taste of.

Speaking at a wine conference in New Zealand, Mr Hanni adds: “We need to celebrate the diversity of consumers, not make them feel stupid. You can serve sauvignon blanc with steak – why not? We need to get over the notion that food and wine grew up together. Food and wine matching is pseudo-science full of metaphors and misunderstandings.”

How will climate change affect the wine industry?

Wine has always been connected with environment, location and climate. Grapes harvested in different regions have different depths of flavour. Even grapes from the same vineyard can differ every season, depending on the weather. Given that, it’s not surprising that the vast differences in weather patterns we are experiencing around the world thanks to climate change are affecting the wine industry in a big way.

How does extreme weather and climate change affect wine?

The flavour profiles of different wines are impacted by increased temperatures and unpredictable weather. This is the main difference for consumers. But for farmers and vineyard producers, there is a much bigger impact.

Scientists now say that growers must implement changes to the way they grow. For example, they should experiment with different, lesser-known grape varieties and try different irrigation methods. However, these are often too expensive and risky for many.

The past four years have presented the world with the hottest ever temperatures. As grapes generally need temperate climates, this has vastly affected crops. The unpredictability of droughts, rainfall, hail and heatwaves is also devastating. And while farmers of all kinds are affected, grapes are particularly vulnerable.

The climate and soil is changing

While wine growing regions such as California battle with ever-increasingly devastating wildfires, other subtle changes are impacting grapes too. Some regions are undergoing changes in soil salinity, due to rising sea levels. Growers are also dealing with increased vine diseases and damage caused by pests.

In the past, the chill of winter frosts has been enough to kill off many pests. However, if the temperatures continue to be higher than freezing, pests will only increase and cause more problems.

The wine industry is hugely dependent on changes in climate and soil. Experts say that four aspects make up wine: the soil, the grape, the topography and the weather. Even a single vineyard can include multiple different microclimates, due to exactly how much sun grapes receive in different positions. The weather affects the acidity of the grape, as well as its sugar and tannin content.

Harvests shifting forward

As temperatures continue to increase year on year, grapes are harvested sooner than ever before. If they stay on the vine, too much sun will mean the grapes contain too much sugar and therefore alcohol. However, harvesting earlier means losing some of the complexity of flavour. This is drastically changing previously reliable flavour profiles. For example, in New Zealand, most of the exported wine is Sauvignon Blanc, which is loved for its acidic gooseberry notes. Its flavour profile is changing and is now more ‘mellow tropical fruit’.

Many vintners have already started to use climate-intelligent agricultural practices. But this isn’t always possible for all farmers, due to cost and availability of the technology needed. The kinds of measures taken include drop irrigation and cover cropping to help conserve water and soil, using nets to protect vines from hail and growing shorter vines.

Others are shifting their focus onto slops that face south to reduce exposure to the sun. Yet others are moving their whole vineyards to cooler regions and higher altitudes. Even the simplest changes to the way farmers grow grapes comes at a higher cost in terms of additional labour and equipment.

There’s no doubt that the global wine industry is experiencing a time of change. Decisions must be made by growers regarding investment into new growing practices to future proof their crops.

What exactly is oaked wine?

If you’re a lover of wine, then the chances are you have heard about ‘oaked’ wine. But do you know what it means and how it affects the wine you choose to buy?

Oak barrels have been used for centuries to store wine, but it’s only much more recently that winemakers have started to understand the way they affect the wine. Oak barrelling affects the body and flavour of the wine and adds softer tannins to the final product.

How is oaked wine made?

A range of woods and different kinds of oak are used to make vessels to store wine around the world. However, there are three distinct types that are recognised for the specific effect they have on wine when it’s stored in barrels made from them. These are Quercus Robur and Quercus Patrea, which are both used in France. In the United States, the white oak variety Quercus Alba is used most often and is generally described as ‘American’ or ‘French’ oak.

Before oak is used as material to make the wine barrel, it is specially seasoned. This can be achieved by warming the wood using a kiln. The best method to achieve this, according to winemakers, is to season the wood in the open air. This allows the sun, wind and rain to slowly remove chemicals and bitter tannins from the wood, leaving it perfect to use for wine barrels.

Weathering the oak in this way takes between two and three years, which is perhaps why some prefer to use a kiln.

Constructing wine barrels with oak

When the oak has been appropriately seasoned using either method, it’s chopped into small lengths called staves. The winemaker will decide on the size of the barrel according to their needs. If they want a very large barrel, this will be to expose the wine to as much oxygen as possible. This softens the natural tannins in wine and gives dried fruit flavouring to the wine.

Often, flavouring is added to the wood used. This needs smaller barrels and for Rioja and Bordeaux, barrels that hold 225 litres are used. Wood used in this way adds sweeter spice flavours to the wine, such as vanilla. It also softens the tannins, making the wine smoother on the palate.

How long is wine aged in oak barrels?

The length of ageing can be from just a few months to a number of years, depending on the tannin and phenol levels in the wine. These act as preservatives and keep all the fruity flavours and aromas.

Winemakers all over the world use oaked barrels to age their wine using both French and American oak. The latter gives more intense flavours to the wines and are also less costly. These flavours are generally too intense for more delicate wines, and it’s usually used for medium and full-bodied reds, as well as full whites like chardonnays from the New World.

French oak barrels cost approximately €1,000 and are notably more expensive than those made from American oak. This adds a significant cost to each bottle made using barrels made from French oak. There are various ways to give a similar ‘oaked’ effect without paying premium prices. These include putting the oak directly into the wine rather than paying a craftsman to make, fire and finish a barrel. Instead, staves are placed inside containers made from stainless steel to impart the oak flavours into the wine. The cheapest way of all is to use oak ‘chips’, which are put in a muslin bag and dropped into the wine. To be sure which method has been used on the wine you choose, look out for the labels. If it says ‘aged in oak’, then that uses the traditional method, while ‘oak aged’ could refer to a cheaper way of imparting flavours into the wine.