Oxygen management at disgorgement is important to improve consistency, and allow the winemaker to use less sulphur dioxide

Unlike ageing, oak use, or sugar levels, the topic may not be exciting Champagne enthusiasts, but oxygen management on the bottling line is important for two main reasons: when done effectively it will improve consistency, while it will allow the winemaker to use less sulphur dioxide (SO2) ?a key anti-oxidant, but also a compound that can impart an unpleasant aroma and possibly headaches at high-levels.

Although not new to Champagne, one important advance in the fight against oxygen entering the wine at disgorging is a method called jetting, although not everyone is convinced of its need.

The process sees a small amount of wine added to the bottle just before it's closed with a cork. This injection of wine ensures the liquid foams, expelling any oxygen in the headspace.

One strong advocate of the technique is Bollinger's new winemaker, and former oenology head at the CIVC, Denis Bunner, who has overseen the installation of jetting at Bollinger earlier this year.

Bollinger's Denis Bunner said that jetting ensures a consistently low level of oxygen in each bottle

Bunner told db, "Now we can decide to jet or not to jet, but jetting is important to control not only the amount of oxygen in the neck of the bottle, but the regularity between bottles."

Noting that something as common as bottles bumping into each other on a bottling line can create variable levels of oxygen ingress, he said that before Bollinger installed the method, one might find between 1 and 10mg/l of oxygen in a sealed Champagne, but with jetting, "we have 1mg/l in each bottle."

Bunner stressed that Bollinger don't actually add any sulphur dioxide at disgorgement, but wanted to use jetting to remove "variability between bottles".

For those that do add sulphur dioxide just before the Champagne is sealed, Bunner warned that it could be necessary to lower the amount of sulphur dioxide used if jetting is employed, otherwise there is a risk of unwanted aromas. These can range from a gently sulphurous burnt matchstick note to something stronger that can be reminiscent of drains or rotten eggs.

Another house which has installed the method this year is Jacquart. Winemaker Floriane Eznack said that the addition of jetting "has cost a huge amount of money, but investing in our wines is part of the strategy to build the brand."

She also said that it was necessary to improve consistency. "We have been studying the impact of oxygen in the whole process up until bottling to make sure there is no variation in the wine 's exposure to oxygen -and all our wineries are now equipped with the jetting system to maximise the homogeneity of the cuvee."

Moet is another advocate of the technique and was one of the first houses to employ jetting for its Champagnes, however, its sister house Veuve Clicquot will not be installing the system.

Veuve Clicquot winemaker Cyril Brun explained: "We have experimented with jetting on different types of wine but after several months of comparison blind tastings we have seen no tangible differences between the references and the bottles which have been through jetting, so we have decided not to use it."

Nevertheless, Brun said that Veuve Clicquot was attempting to reduce the level of total sulphur dioxide in its wines, admitting that the Champagne contains "close to 40 mg/l but the house would like to potentially bring that down by 5mg/l.

To add a sense of proportion, the legal maximum for white wines sold in the EU is 210 mg/l, so Veuve Clicquot's level is already extremely low.

Bunner commented, "Champagne has very low levels of sulphur [dioxide] but there are people who are very sensitive to sulphur, so anything we can do to lower the level further is very positive."

Current techniques to achieve this at Veuve Clicquot include trialling different types of crown cap during ageing on lees. "We have tested different types of metal cap to manage the oxygen as the closure could be another tool in our attempt to reduce the amount of sulphur dioxide,"he said.

However, he warned, "We don't want to change the style of our Champagnes,?while stressing that sulphur dioxide "is not just about oxygen management, it also has a role to eradicate unexpected bacteria."

As a result, he pointed out that it was vital to harvest "healthy"grapes, because berries with botrytis require the use of high levels of sulphur dioxide during vinification because the bacteria accelerates oxidation.

Interestingly, he said that one technique to achieve cleaner berries was the use of intervine planting. "We grow grass in the vineyards to give gentle competition to the vine which reduces the vigour of the plant, so when the fruit grows it develops a thicker skin, which makes it harder for the botrytis to enter the fruit."

Elsewhere, at Louis Roederer, employing the jetting method could both negatively alter the house style, as well as also take away a welcome level of bottle variation, according to chief winemaker and chef de caves Jean-Baptiste Lecaillon.

"We were the first to trial jetting and we stopped, because our wines were already reductive and they needed to breath, and they were allowed to do that at disgorgement,"he told db, before stating, "We need oxygen; others need protection against it."

But he also commented, "In Champagne, every bottle is a fermenter, so every one has a different story. During the ageing too there is a difference; for example, there is a 3-degree difference in temperature depending on where the bottle is stored in the stack. So I don't think we should pursue too much the idea of homogeneity ...and if we all use the same techniques, then we will kill the story -difference is important."