by Dave Williams
If there is one wine that gets more scrutiny than others, it must be Champagne, if for no other reason than reverence and cost. And with science now catching up to what history has shown, once again another finding of minutia to ponder when consuming your bubbles. In a recent 5 year study science has shown a benefit to cork during tirage (champagne’s in bottle second fermentation) in comparison to lesser expensive crown caps which are plastic coated metal caps similar to conventional beer bottle caps.
The study was performed by Amorim, a Portuguese cork producer which included sparkling wines from across the globe, not just champagne. Three properties were assessed: 1) retention of CO2, 2) oxygen kinetics and 3) volatile components. The study found measurable differences of volatile components and oxygen kinetics. While cork had similar CO2 values with crown caps, it showed greater preservation of volatile components like esters which we can sense in the nose and taste.
However, it was differences in oxygen kinetics that the study highlighted. It was explained that there is a balance between oxygen and reduction. During tirage there is a breakdown of components such as dead yeast cells, which consumes some of the dissolved oxygen in the wine making the second fermentation reductive (reducing oxygen). This can lead to unpleasant Sulphur-like aromas. It was shown that the small amount of air trapped in the micro pores of cork were injected into the bottle when it was compressed for insertion adding 2-2.5mg of oxygen per bottle. This small amount of O2 helped reduce the oxygen consumption during tirage creating a better balance. On a scale of 1-10 most winemakers preferred a balance of 3-4. Crown caps had an average measurement of 2.5 whereas cork had 4. The lack of reductive aromas and better preservation of esters creates more flavors, more fruit, more toast and brioche in sparkling wines. While the study ran for 5 years many of these differences were noted after 2.5 years. The unanswered question is what happens after 10 or 20 years?