Smoke taint thresholds close to being found

Last year’s world-first discovery that smoke dose is directly linked to the level of smoke taint in wine was an ‘absolute gamechanger,’ according to Professor Ian Porter.

‘We discovered that provided the burn is not right next to the vineyard, it actually takes a lot more smoke to cause smoke taint than we originally thought’, Professor Porter from La Trobe University said.

He said he hoped the finding – and the risk prediction tool being developed as a result – would allow growers to feel more comfortable with managing fire risk in the future.

It’s important to note, however, that smoke from any fire can damage grapes, provided there is enough of it. There are many examples of smoke taint arising from both bushfires and controlled burns.

Professor Porter will present his findings at the National Wine Sector Bushfire Conference on 25 May. The free conference will feature research updates, practical bushfire preparedness and best practice techniques for smoke effects and recovery from fire – to ensure that grapegrowers, winemakers and businesses are better prepared, better informed and better equipped to handle the decisions that need to be made before, during and after bushfires. 

Professor Porter recently completed a project that studied the impact of the 2019–20 bushfires across Victoria and New South Wales (NSW). Smoke exposure in bushfire areas varied greatly across regions, providing a spectrum of risk of smoke taint from low risk to very high risk.

His team worked closely with the sector to monitor smoke levels and collect samples of grapes from vineyards with a wide variety of smoke exposure. A total of 91 wines across 8 different grape varieties were made. These will serve as reference wines for the sector as well as contributing to data that provides a link between smoke dose, levels of smoke compounds in grapes and wine and development of smoke taint in wine.

This data will build on a previous research program at La Trobe University and Agriculture Victoria, which determined how much smoke in a vineyard would cause tainted fruit.

A number of smoke detection units were used in combination with the existing EPA networks to monitor bushfires in the winegrowing regions of Tasmania, NSW and Victoria from 2018 to 2020. The researchers worked with local wine producers to determine the risk of taint according to the measurements determined by the smoke sensors. 

The research teams also tested a number of commercially available coating products for their ability to reduce the uptake of smoke compounds by grapes in the vineyard. While most actually increased the uptake of smoke taint compounds one of the tested products – chitosan – showed promising results for grapegrowers.

Professor Porter said there was a common, long-held belief that even small amounts of smoke and smoke haze caused smoke taint.

As a result of their findings, the research team is close to setting smoke taint thresholds.

He said this – coupled with the risk prediction tool – would allow growers to manage potential smoke taint before it occurred.

The risk prediction tool will send growers a message on their phone and alert them to possible risk. Growers can then put in place appropriate wine mitigation strategies, which might include less time on skins for red grapes or reducing the press of white grapes to less than 50 per cent.

You can register for the free National Wine Sector Bushfire Conference here.

Photo credit Professor Ian Porter, Giselle Roberts, LaTrobe University