Hot Stuff: Rising Alcohol Levels In Wine

Why are alcohol levels rising? Caroline Gilby MW explores the reasons and discovers that it is too simplistic to blame it all on changes in climate

Alcohol - wine's double-edged sword

Wine has almost certainly been a social lubricant since people first settled in one place long enough for fruit to ferment. Even 6,000 years ago, wine already had a ritualistic role around funeral rites - as shown by evidence from the oldest winery so far discovered in the Areni-1 cave in Armenia.

The oldest winery ever discovered in Areni-1 cave in Armenia

The oldest winery ever discovered, in Areni-1 cave in Armenia

Alcohol aware

However, we need to be aware of what we are drinking to avoid tipping over into the harm zone - the World Health Organisation lists alcohol as a definite carcinogen, never mind all the accidents and behavioural problems we have become used to seeing in the news. And nowadays everyone is well aware of the risks of drink-driving too.

Alcohol units were introduced in the UK as far back as 1987 to help people keep track of their drinking. And much as many of us like to believe that wine is a superior form of booze, part of its attraction is the very alcohol it contains.

Units not universal

In the UK, a unit is defined as 10ml or 8 grammes of pure alcohol, though interestingly this is not a universal standard - in the USA a unit is 14 g of alcohol, while Italy's unit is 10g and France's is 12g.

In the late 1980s, a glass of wine was roughly equivalent to one unit, a notion that has stuck firmly. However, back then as a nation we drank huge amounts of Liebfraumilch, Piesporter and Hock at around 8-9% alcohol, and even red table wine or bog-standard claret would have only been around 11%. Serving sizes were also a lot smaller with the ubiquitous Paris goblet holding no more than 125ml.

Bigger glasses, stronger wine

Bigger measures: today a 'small' glass is equivalent to ¼ of a bottle

Today the picture is very different, with many wines hitting 14 to 15% alcohol, and sometimes even higher. There has also been inflation in glass sizes, so while it's still a legal requirement for outlets to serve 125ml measures if asked, this size is almost never listed and 175ml is now typically the 'small' offering. This is actually a quarter of a bottle while a 'large' 250ml serving is a third of a bottle.

According to the NHS website, a 750ml bottle of wine at 13.5% contains 10 units so a quick calculation shows that a large glass of wine could easily be 3.5 units, and more if the wine is stronger. This means that a single glass of wine could exceed the UK's current recommended daily maximum for a woman (2-3 units per day) while it looks likely that the UK's Chief Medical Officer is about to recommend an even lower limit. Food, or drink, for thought.

Why the increase in alcohol?

Climate change

The reality is that wine has become stronger, and we drink more of it in larger glasses, but why? One thought is that climate change may be a factor, and while this has many implications for the future of the wine world, it seems it is not the most important factor in increasing alcohol levels.

Changes in taste

A paper published by the American Association of Wine Economists in May 2011 found that 'rising alcohol content of wine may be a nuisance by-product of producer responses to perceived market preferences for wines having riper, more-intense flavours, possibly in conjunction with evolving climate.' Read more on that here.

Rising sugar levels

Average sugar content in California had gone up 11% between 1980 and 2007

Researchers had observed that average sugar content at harvest in California had gone up 11% between 1980 and 2007, which means a corresponding rise in alcohol too. Matching data on finished wine in California are hard to track, as labelling tolerances are very lax in USA (the US allows 1.5% tolerance whereas the EU requires labels to be within 0.5% of actual alcohol in the wine).

Looking at the evidence

However, usefully for this research, Ontario in Canada has a state alcohol monopoly called LCBO (Liquor Control Board of Ontario), self-proclaimed as the world's largest purchaser of beverage alcohol, and it analyses every wine it imports.

The researchers took 16 years of data from 1992 to 2007, finding 91,432 useable samples of dry wines and also looked at patterns of changing climate across a number of wine regions to calculate a growing season heat index. Every country showed an increase in average alcohol across the period - ranging from just 0.2% to 2.0%.

Human factor more important than environmental

A series of regressions were run to explore the effects of climate change (represented by the heat index) to examine whether this was a contributor to the rising alcohol content. However, they concluded that the change in alcohol levels was much higher than could be accounted for by climate changes and therefore it is largely a man-made phenomenon.

The research also showed that on average white wines had lower alcohol than reds, and that new world countries (the Americas, Australia, New Zealand and South Africa) had higher average alcohol levels than Europe. As UK drinkers have switched towards drinking more new world wine, and more red wine, this will also partially explain rising alcohol in our glasses.

The dilemma for winemakers

The problem for winemakers is that to turn the boring simple flavours of grape juice into complex wine requires yeast to ferment the fruit sugars, producing alcohol as well as wine flavours, and higher sugar inevitably means higher alcohol.

Also consumers, and certain critics, seem to have a preference for softer, fruitier, less astringent wines - which means riper fruit to achieve this. A lot of effort has gone into better viticulture, lower yields, canopy management and techniques like leaf plucking to increase sun exposure, selection at harvest and so on to get this riper fruit.

Better viticultural practices result in riper grapes which skilled pickers are able to select at harvest time

Better viticultural practices result in riper grapes which skilled pickers are able to select at harvest time

Sugar accumulates through photosynthesis and high temperatures and sunlight increase its rate. However, varietal flavour and tannin ripeness are more closely linked to sunshine hours, so many growers are now finding a mismatch, with sugar levels rising before flavours are fully developed or tannins soft enough for today's tastes. And waiting for flavours to develop before picking can mean very high alcohol. Drought can make things even worse as vines shut down if there's not enough water, so tannins can stay unripe and astringent while sugar still concentrates due to grapes shrivelling.

Effects of climate warming already with us

In fact, a simple heat index doesn't cover all the factors involved in a warming climate and some changes are already happening - extreme weather causing flooding, soil erosion or droughts, while earlier spring budburst brings risk of frost damage.

Risk of frost damage from early spring budburst at the Hugel vineyards in Alsace

Risk of frost damage from early spring budburst at the Hugel vineyards in Alsace

Earlier harvests also have a range of effects that are not fully understood yet. For instance, fruit ripening while it's still hot at night affects acid levels, particularly malic acid which is involved in respiration (this process continues at night at a higher rate when it's warm, one of the reasons why high malic varieties like pinot noir don't do so well where it is warm at night).

Other factors linked to climate changes include the thinning ozone layer allowing through more UVB which may be linked to a characteristic called atypical ageing aroma. This can cause aromas of mothballs or floor polish, and early loss of varietal expression in whites.

A backlash in consumer tastes

Whether higher alcohol levels in wine are due to taste preferences, vineyard factors or climate change, maybe consumer preferences are starting to turn the tide back again. It is notable that many producers are increasingly concerned about alcohol and are moving away from the new world-style 'fruit bombs' of the past few years.

Techniques to combat rising alcohol levels

Lighter and more refreshing styles of wine are coming to the fore, with drinkability and balance being winemakers' goals rather than concentration and power. In some parts of the world, (especially but not exclusively the USA) technological solutions have been developed to reduce alcohol levels in finished wine (such as Reverse Osmosis and Spinning Cone Column), though it's rarely talked about as it can be perceived as industrial manipulation of wine, and indeed is only allowed within the EU in limited circumstances.

There's also research going into developing less efficient yeast strains that naturally produce less alcohol during fermentation. Over the longer term, vineyard techniques may evolve to slow down ripening, and we may see changes to what varieties are grown where, as each has its own climatic preferences.

A change in perception of premium vineyard sites

Marginal vineyard zones may become more successful while some currently premium sites may just become too dry and hot, and cooler sites at altitude may become more appealing. Pest and disease pressures may also change as they can survive across bigger ranges, while in the worst-case scenario rising sea levels may wipe out some coastal areas like Carneros or Bordeaux.

Selecting lower alcohol wines

For now, for anyone concerned about alcohol levels, some wines are normally lower in alcohol, and you can set alcohol level as a search term on The Wine Society website. This turns up a wide variety of interesting and tasty wines including riesling, muscat, cortese, cserszegi and more, from regions as diverse as the Loire Valley, Côtes de Gascogne, Germany's Pfalz, Soave, vinho verde and even Gloucestershire.

Look out for The Society's offer of wines of 12.5% and below which we is being prepared for publishing early next year, including several wines from the new world.

Enjoy, responsibly.

Caroline Gilby MW

Caroline Gilby: Master of Wine

Caroline Gilby is a Master of Wine and a scientist by training. She is a wine writer with a passion for the wines of Central and Eastern Europe and contributes to several wine books, magazines and websites.

November 2015

> More articles on winemaking

> More articles from Caroline Gilby MW

> More articles on alcohol levels & climate change:


Members' Comments (1)

"Personally I would say that far from being "The mark of a generous and gracious host," serving champagne is the mark of someone with more money than sense, or someone who is out to make an impression. Just a personal view from someone not keen on carbonated drinks and I expect many will differ.. but champagne marques do more than enough advertising, without us making sweeping statements like that! Formula 1 victory celebrations, that is the best... Read more > use of champagne :-)"

Mr Jeremy Whitmarsh (30-Nov-2015)

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