This project’s objectives were to mitigate the impacts of climate change on the national wine industry by reducing losses to smoke taint from bushfires and controlled burns and improve public land management. An early warning remote sensing network of smoke detectors was established and, using correlations between smoke, grape and wine measurements taken around controlled burns and bushfires, has enabled early stage predictions of the risk of smoke taint from smoke events in vineyards. Additionally, a chitosan coating was found to reduce the uptake of smoke taint by grapes in controlled smoking experiments, whereas other coatings generally increased uptake.
The exposure of vineyards and grapes to smoke from bushfires and/or controlled burn events may result in ‘smoke tainted’ wine, that can cause serious economic losses to industry. Since 2003, major fire events have affected over $400M worth of grapes and wine that were either rejected commercially or downgraded as a result of smoke taint. The frequency of bushfires and controlled burns is expected to increase under various climate change scenarios, thus it is important that the Australian wine industry develop cost effective remediation tools to manage smoke affected grapes and wine. This collaborative DJPR and La Trobe University project was part of a larger program funded by DAWR and Wine Australia, and focussed on providing the industry with an early warning system and mitigation tools in the vineyard, while the Australian Wine Research Institute focussed on mitigation of smoke taint in wine.
This DJPR/La Trobe University project focussed on:
(i) Setting up a network of smoke detectors in wine regions prone to smoke,
(ii) Testing the smoke detector network to predict the risk of sensory smoke taint in wines produced from smoke affected vineyards
(iii) Determination of how smoke dose and composition linked to grape and wine levels of phenolic smoke taint compounds and sensory outcomes in wine.
A state-wide network of 7 remotely accessible aspirating smoke detectors was set up and operational from the 2017 autumn controlled burning period onwards. Commercially available Very Early Smoke Detection Apparatus (VESDA®, Xtralis P/L) units were modified to suit the purpose of the study. This network consisted of three VESDA®'s in the Ovens and King Valleys in north east Victoria, three VESDA®'s in the Yarra Valley, and one VESDA® in the Otways region. In addition, roving VESDA®'s were used to take smoke measurements at and around controlled burns, along with measurements of smoke composition and, where possible, grape uptake of smoke taint compounds. Wines were produced from smoke exposed grapes, both from bushfire affected vineyards and from grapes deliberately smoked at controlled burns.
Our in-field measurements allowed the establishment of some key relationships to be developed between smoke measurements and levels of smoke taint compounds in wine. When combined with wine sensory analysis results, these relationships will allow the development of a smoke taint risk assessment tool which can be used by industry to guide their decision-making process following smoke events.
The early warning network of smoke detectors proved to be effective for monitoring widespread smoke events during the growing season and quickly providing industry with objective measurement results. The current static VESDA® network was of limited value for monitoring the impact of smoke from small bushfires and controlled burns, which impacted a much smaller area than large bushfires, and was often found to be very localized. Accurate measurement of the impacts of these smaller fires would require a much more extensive network of smoke detectors because of highly variable smoke concentrations in the atmosphere.
It is recommended that a more extensive statewide and national network of smoke detectors and smoke composition monitoring be developed and that this be made readily accessible to industry, such as via a mobile phone app, which could provide interpretation of smoke exposure levels in terms of smoke taint risk.
An effective coating to reduce the uptake of smoke taint compounds was found — chitosan — which is a biopolymer that was applied to grapes as an aqueous solution and found to reduce the uptake of smoke taint compounds by 30 – 60% during controlled experiments. Further research is required to develop a product which could be practically and economically applied in the field. Another important finding of this work was that coating products such as commercially available liquid anti-transpirants and sunburn protectants have the effect of increasing, in some cases by greater than 50%, the uptake of smoke taint compounds by grapes, and thus some products should be avoided when there is the risk of smoke exposure. Investigations also showed that absorption of smoke taint compounds by grapes is rapid, generally complete within a day of smoking, meaning any attempt to wash the compounds from the grapes after this time would be unlikely to have any significant effect.
This project was funded by the Commonwealth Department of Department of Agriculture, Water and the Environment Rural R&D for Profit program through Wine Australia with co-investment from La Trobe University and the Department of Jobs, Precincts and Regions.