More wine faults

By Ian Hickinbotham
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Ian Hickinbotham, author of Australian Plonky

Ian Hickinbotham, author of Australian Plonky

A cellar full of old wine

 

Oxidation of bottled wine is not very common nowadays due to advances in winemaking equipment and knowledge.

However, a qualification of that claim can be due to the practice of serving wine by the glass in modern restaurants – if the bottle of wine has been undisturbed when ullaged for days. But, many modern restaurants have installed those machines that neatly cover the surface of the wine in half-empty bottles with inert gas, like nitrogen, or even carbon dioxide (some of which dissolves in the wine) which has affinity with all wine, being produced when the original grape sugar is fermented by yeasts into alcohol and gas – carbon dioxide. In fairness, there are also restaurants that pour particular wines from particular bottles quickly, meaning before oxidation can occur.

Oxidised wines, white and red, taste flat and just plain dull. Putting that another way, any wine fruitiness purposefully retained by the winemaker, is dissipated. Having stated that, there is the qualification that simple fruitiness alone in red wines is coveted by some, and current New Zealand pinot noir wines come to mind, but it is not enough to satisfy those who want classic ‘Burgundian’ farmyard smell and taste. Complexity, in other words! With white wine, browning of colour is more obvious, though oxidation has to be considerable before sight confirms oxidative damage.

Volatile acidity is the most common fault found in red wines especially. However, a qualification of that assertion is the wines are made by non-oenologists, and sadly ‘organic’ wines come to mind first. Put simply, some bacteria (that arrive at the winery on the skins of the grapes) are present in the bottled wine and they develop ‘vinegar’ type taste and smell. ‘Vinegary’ acidity ‘grasps’ the throat, while smell can be likened to nail polish remover (not that half the population know it). For the population of bacteria to be present, such wine is bottled un-filtered, an increasingly fashionable practice lately, but it should not be of concern when practised by an oenologist (and Grange immediately comes to mind).

International wine writers bang on about wines that open as unwanted sparkling wines. This condition spells fermentation in the wine after being bottled and is a major ‘sin’ when an oenologist is responsible. It is just an elementary fermentation and is due to the presence of wayward yeasts or a particular type of bacteria that any qualified winemaker should be able to manage.

Prevention of any haziness in a bottled wine is possibly the most difficult task for winemakers, especially when trace amounts of iron or as little as a quarter of a part per million of copper acting as a catalyst, is responsible. Such copper is often sourced before the wine is made when the juice of the grapes comes into contact with the common metal and the poor winemaker is completely unaware of the history. Perhaps even worse, the haziness often only develops months after the relevant wine has been bottled and stored.

Truth be told, nowadays the most common dry red wine fault is bitterness of taste often wrongly ascribed to excessive pressure being applied to the grape skins to extract the last of the fermenting red juice. Bluntly, the afflicted wine can be so bitter it is nearly undrinkable. The bitterness is due to certain bacteria attacking the glycerine in the wine and is defined as ‘bitterwerden’ by the Germans and ‘amertume’ by the French.

It is not generally known that pleasant sweet tasting glycerine is a natural important component of dry red wine, after water, alcohol and acidity.

 

 

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).

 

 

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September 15th, 2011
 
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