Gadgets Release the flavour
A chemical solution

27 August, 2008

To many it appears as a sharp, eggy aroma and a wine that's subdued and light on flavour - an irritation. To some though, it's the cause of headaches, sneezing and even asthma attacks in the worst cases.

Sulphur dioxide (SO2) is routinely used as an anti-oxidation agent during the winemaking process. It usually remains chemically bound after bottling but on occasion, and particularly in wines in their first couple of years, it breaks free of its chemical moorings and that's when it causes problems - a phenomenon increasingly recognised in young wines under screwcap.

Winemaker James Pennington, of Rivendell Wines in Western Australia's Margaret River region, has developed and patented a handy solution to the problem. His PEWA system (Preservative Elimination in Wine at Consumption) is a means of adding tiny quantities of hydrogen peroxide (H2O2) in order to neutralise the SO2.

"We have it available in two forms at the moment," says Pennington. "One is a special stopper with the exact amount of agent calibrated to the wine and the other is a dropper bottle which can dispense different amounts depending on the wine's preservative level."

The stopper system, available on bottlings of Rivendell's 2007 Semillon/Sauvignon Blanc and 2005 Shiraz, involves raising a lever to release the H2O2, lowering the lever and gently mixing the wine, then raising the lever again to remove t he stopper. With the dropper bottle (sufficient to treat on average 60 bottles at a cost of A$20), one drop will neutralise a free SO2 level of three parts per million (ppm), seven drops 22ppm - the common range for young red wine - and nine drops 29ppm - the common range for young white.

Pennington is quick to dismiss any concerns over the concept of adding a substance more commonly recognised as a bleaching agent to wine.

"It is an extremely low concentration of H2O2 and we refer to it as a neutralising agent or oxygenated water," he says. "Most customers don't care too much about the chemistry so long as it works, particularly those who suffer from preservatives."

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