The early influence of oxygen investigated

A new four-year research project at The Australian Wine Research Institute aims to reveal new insight into the timing and amount of oxygen required to benefit red and white winemaking and prevent ‘reductive’ odours.

Funded by the GWRDC, the project started in July 2013 and is being led by AWRI Research Scientist Dr Martin Day, with complementary small-scale laboratory work by AWRI Senior Research Scientist Dr Simon Schmidt.

Dr Day said the science and technique of adding oxygen in the early stages of fermentation is relatively new in wine science terms, and more widely accepted and used in France than in Australia.

‘But, since we launched this project we’re finding more people interested all the time, and there seems quite a lot of small-scale anecdotal work and positive results coming through from Australian wineries’, he said.

‘In the beginning, a lot of the work being done by the AWRI in this area was around oxygen ingress during bottling and from closures, but we’ve definitely moved on in the past couple of years.

‘Over time our own research results were telling us that more than 20% of wine faults were related to ‘reductive’ characters and these weren’t limited to wines sealed under screw cap – this made us think that lack of oxygen in the early stages of winemaking could be to blame!

‘It’s taken us down this path of identifying the importance of adding a controlled amount of oxygen in the early stages of winemaking – but it also showed us that much more work needs to be done to understand the importance of timing and amounts necessary for beneficial results.

‘We know it’s not a process that works for every wine variety or style but there’s enough anecdotal knowledge out there to say if used correctly, it can reduce ‘reductive’ odours in wine and can influence certain styles’.

The first stage of experiments have just begun for vintage 2014, with Dr Schmidt carrying out small-scale ferments in the lab to reflect the extremes of oxygen exposure during normal white winemaking techniques.

Dr Day said the effects of the oxygen exposure will be tested from early stages (pressing) to later post-ferment.

‘Two pressing techniques will be used – inert and aerobic – and the musts will be subject to two handling methods each, reductive and oxidative’.

At the end of this first project, Dr Day said there would be four wines with four very different stylistic results, reflecting the extreme use of oxygen in this process.

‘Over the next four years, the project will see small-scale ferments first carried out in the lab, with a particular focus on timing and amounts of oxygen, and then the same experiments will be matched on a large-scale in participating wineries’, he said.

‘At the end, we hope we will have a much greater understanding that will enable wineries to use oxygen in a controlled manner to influence their wine styles of choice’.

Inert press used for the first round of lab experiments this vintage
Inert press used for the first round of lab experiments this vintage