This year’s ASVO Oenology Paper of the Year award was presented in part because of the project’s potential for high rates of immediate adoption by the sector – and that potential is already being realised.
Winemakers are using oxygen during fermentation with more confidence and much greater knowledge of the impact in specific situations, thanks to the work of a team at the Australian Wine Research Institute (AWRI).
The four-year project, funded by Wine Australia, is still under way, but findings are being disseminated via roadshows, seminars, webinars, journal articles and a workshop at the recent Australian Wine Industry Technical Conference. The workshop – which included a tasting – looked not just at the value of using oxygen, but also at ways to remediate the reductive characteristics that can occur if you don’t.
‘It is fantastic to see how we can support the sector and give winemakers practical advice on how they can produce better wines’, said Research Scientist Dr Marlize Bekker, who was one of the authors on the paper that impressed the ASVO judges.
‘The project included a number of elements. We not only investigated the unwanted aroma compounds associated with “reductive aromas” that may be produced during fermentation during low oxygen conditions, but also investigated the beneficial varietal aroma characters, as well as compounds associated with wine texture, such as tannins and polyphenols. It’s many of the things a winemaker would want to know if they applied a specific treatment to their wines, what would the overall outcome be?’
The project was led by Dr Martin Day, who worked with Drs Simon Schmidt, Paul Smith and Eric Wilkes to develop the experimental design. Dr Bekker managed the sulfur chemistry and analysis, with Drs Helen Holt and Wes Pearson responsible for the sensory side of things.
There’s also been a lot of sector input, both before and during the research. ‘Several wine sector players have been doing their own work, so empirically we have learned from them and then we have brought some scientific assessment to the things they were observing’, Dr Smith said. ‘So I think we’ve been able to explain the reasons behind the effects they were seeing. We’ve closed the loop.’
One of the main findings to date is that when using oxygen to create specific wine styles the overall amount of oxygen is important, but also when you add it and how long you take to add it is also important.
‘We thought adding oxygen late in the process might cause negative stylistic attributes, but that doesn’t seem to be the case’, Dr Schmidt said. ‘But timing is critical when using oxygen to stimulate fermentation. You have to be within a certain window for maximum benefit.’
The ultimate aim of the project is to create a tool kit to guide winemakers in how and when to use oxygen to achieve different results.
Strangely, given the impact oxygen can have on wine, not much research has been done in this area internationally. Dr Day found only a handful of papers over the past 20 years that carry research through to the sensory stage.
Part of the reason may be that it is a challenging area. The sensors that make it possible to measure oxygen levels in a liquid have not been around for long, and even with this new technology it can be exacting work.
The AWRI’s initial research looked primarily at the impact of large doses of oxygen, but the focus now is on refining the knowledge by comparing different dosages to see which are the most beneficial in specific situations.
‘We want to be able to provide accurate advice to winemakers on what to expect from their fermentation efficiency and wine aroma profiles when applying oxygen treatments to their wines’, Dr Bekker said.
Photo credit: Australian Society of Viticulture and Oenology (ASVO)