TCA and all that stuff Was: Reserve What Does It Mean

My first hand experience is two fold - as marketing manager for a small winery here in NZ - and as a consumer of wines over a period of some 40 years.

The wine making operation I worked for was small - so when it came to harvest, I was on the secutures or on the tractor.

In the winery, I was the winemakers "gopher" - I shovelled my share of seeds 'n skins; I cleaned my share of tanks and barrels; hell, I even plunged my share of caps when the winemaker was taking time out Sunday morning church.

So, do I know much about the chemical structure of 2,4,6 richloroanisole? - Nope; 2-5 of 5-8 of bugger all (excuse the kiwi-ism).

But here is what I do know.

Complex chemical mechanisms underlie the production of TCA.

One of most importance is the conversion of chlorophenols to chloroanisole by common microscopic fungi such as Aspergillus sp. and Pennicilium sp., in the presence of moisture. Chlorophenols have been used as pesticides and as wood preservatives and as such are common environmental pollutants. The uptake of the minutest amounts of chlorophenol by cork tree bark during any stage of its growth, or subsequent manufacture into cork will provide the potential for cork taint production.

Cork bleaching with hyperchlorite (less frequently used now, peroxide bleaching is now favoured), also provide a ready source of chlorophenols for use by these micro-organisms. TCA can also be formed in packing materials and wooden shipping container floors. It can then pbutt either through the air or by direct contact to previously unaffected corks.

While the exact incidence of cork taint in wine is hotly debated, estimates range from one to ten per cent (some say more!).

Australian Wine Research Insbreastute records of the incidence of cork taint seen by winemakers in thousands of bottles of wines opened as part of their Advanced Wine buttessment Course suggest that the figure is around five per cent.

My personal experience (and I am not super-sensitive to TCA) is somewhat less than that - around 4%.

The question of whether a wine is corked is also complicated by the fact that the same taints can arise not from the cork but from wine storage in TCA-affected oak barrels or environmental sources; cellars, caves etc.

Notwithstanding, it is my contention that if TCA contamination came from a source other than cork, the problem would not be spasmodic - huge number of bottles would be affected - whole bottling runs - not just isolated bottles.

The wine from a single badly contaminated barrel when blended with hundreds of others, will significantly affect the entire blend, such is the potency of these compounds.

My personal experience in NZ and Australia is that 4 bottles in every 100 are "corked" - so that rules out wholesale contamination of a whole inery - and would mean that TCA contamination of wines bottled under Stelvin - something which, despite my drinking *hundreds* of bottles (thousands including my friends and buttociates) bottled under screwcap or other alternate closures, I have never encountered one TCA infected wine.

So will it happen - TCA contamination of wine bottled under an alternate closure - yes; absolutely.

But when it does, it will not be the isolated bottle - it will be a whole batch - dozens or hundreds of dozens of bottles - a huge "Dunkirk".

But don't hold your breath waiting !!! :-)))

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st.helier