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Scientists harness yeast to cut wine alcohol level

Scientists have moved a step closer to being able to make full-flavoured wines with lower alcohol levels after pioneering work on yeast strains in Australia.

Experiments by Dr Cristian Varela at the Australian Wine Research Institute (AWRI) led to a 1.8% ethanol reduction in both Shiraz and Chardonnay ferments, thanks to working with a combination of three separate yeast strains.

The research, funded by the Australian Grape & Wine Authority (AGWA), comes as many New World producers are looking to reduce alcohol levels – linked by some to climate change – both to reflect consumer tastes and to ease health concerns.

The researchers have now moved onto pilot-scale trials at the Hickinbotham Roseworthy Wine Science Laboratory on the Waite Campus in Adelaide, but Dr Varela warned that much work remained to be done.

‘Sometimes things that work in the lab don’t work in the real world, if only because of the larger volumes,’ he said. ‘Temperature could be an issue or wild yeasts might have a negative impact.’

Dr Varela has been working with colleagues from Australia, Chile and Spain to study the ability of about 50 non-conventional yeast strains to produce lower alcohol wines that are still full in flavour.

One key issue is that many non-conventional yeasts struggle to work alongside saccharomyces cerevisiae, the most commonly used wine yeast strain, because it is so fast and strong.

But Dr Varela found that a combination of saccharomyces cerevisiae and two non-conventional strains – metschnikowia pulcherrima and saccharomyces uvarum – reduced ethanol levels in Shiraz and Chardonnay, once the juices had been treated to remove microbes.

The key with larger-scale trials will be to get the non-conventional yeast strains to work, and to avoid off-flavours in the final wine, Dr Varela said.

‘Now we need to work with bigger volumes and with naturally-occurring yeast and bacteria coming from the grapes in the mix, to see if the two non-conventional strains are still able to deliver the goods,’ he added.

‘The ultimate aim is to translate this into something that winemakers can use to maker lower alcohol, full-flavoured wines.’

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