High alcohol wine – its cause and what it means

Does your wine taste 'hot'?

By Ian Hickinbotham
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Ian Hickinbotham, author of Australian Plonky

Ian Hickinbotham, author of Australian Plonky

Australian Plonky by Ian Hickinbotham


Table wines of increasing alcohol content are becoming the bane of consumers in many countries.

Even the French have been critical, and there are reports that wines of their latest 2009 vintage are testing at 15 percent alcohol (meaning alcohol by volume, abbreviated to ABV in some publications). Twenty years ago, 12 percent was about the norm.

Of course global warming is the cause, which is rather proven by the phenomenon being reported in all wine-producing countries.

Regular drinkers especially are alarmed. Because of wine's natural alcohol content, they usually decide precisely how much wine they will drink on any one occasion, based on long experience. Higher alcohol content requires unwanted and perhaps inconvenient quantity adjustment*. Putting it bluntly, the phenomenon is new to them and they do not like it, essentially complaining of hotness of taste.

One repeating demand, which seems quite logical – and simple – is that grapes be picked earlier so that, with less sugar to convert by the fermentation yeasts, less alcohol would result.

However it is well known that unripe fruit have less taste than ripe fruit: thus a ripe apricot is more appealing than one under-ripe and likewise, a ripe tomato is more tasty than an unripe one.

But perhaps more important, in the case of grapes, unripe ones contain more malic acid and less tartaric, the main acid of grapes, especially ripe ones.

It is nature' s way that after the yeast fermentation a second fermentation occurs, often in the following spring, which converts malic acid to lactic acid, also known as 'milk acid'.

The eminent bacteriologist Koch suggested in 1891 that bacteria were responsible, and in 1901 the great Seifert proclaimed that when the bacteria were present in wine, malic aid was converted to lactic acid.

Importantly, only recently it has been demonstrated that our palates can differentiate the taste of lactic acid. Of all the acids, significantly, it is the only one that most of us can readily identify.

Further, malic acid is an especially hard-tasting acid: it is the dominant acid of apples (hence its name). Lactic acid, on the other hand, is the pleasant acid of yoghurt , cheese and many other important foods of history, like metwurst, dill gherkins, olives, beer and sauerkraut. It could be claimed to be 'nature's acid'.

Logically, this is how the first Champagne, as we know it, was made. The very young wine from under-ripe grapes was bottled early, the malo-lactic fermentation occurred in the bottle and the gas developed was retained by the cork being tied down. This same process was how the original vinho verde ('green' wine) of northern Portugal was made: their grapes were grown climbing on trees so that surrounding land could be cropped, but were under-ripe due to lack of sunshine.

One reason lactic acid is appreciated is because it is actually much less 'tart'. But because of this, when there is a lot of malic acid in the grapes (meaning under-ripe grapes) converted to lactic acid, the wine then lacks natural protection from other undesirable bacterial activity which can change the colour of a red wine to brownish, a condition defined as tourne by Pasteur. Or it can develop intense bitterness of taste (often assumed to be due to excessive pressure being applied during the juice extraction from the original grapes) a condition defined as amertume by the French and bitterwerden by the Germans.

Especially in the case of white wines made from unripe grapes, they can even take on an unsightly viscosity akin to motor oil, a condition known as graisse. The wine actually pours with a 'plopping' sound!

However, oenologists can now handle wine so the secondary fermentation does not occur in the cellar, but absolute wine-making hygiene is required, while oenophiles can legitimately assert that such processing is extremely unnatural**.

No doubt this debate will heat up along with the weather.


Ian Hickinbotham, one of the most innovative and influential oenologists in Australia over his 50 year career, is the author of Australian Plonky (see related reviews below).


*Editor's notes: The corollary is that – being more difficult for two people to comfortably consume a bottle of 15 percent ABV wine, mid-week especially (if our household is any indication) – less wine is consumed in one sitting, and now with the variety of 'wine saving' devices available, it can be more effectively preserved for later. A second bottle is not opened, less wine may be purchased; ultimately this may reduce demand.

** Technology also exists to remove some of the alcohol from wine, also 'unnatural', and adding to the cost of production.


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March 27th, 2010
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