With fire comes smoke. However, research has shown that just because smoke may be visible or be able to be smelt doesn’t necessarily mean that there is a high risk of smoke affecting the grapes.
Smoke exposure can affect grapes any time during their development, with the greatest risk occurring from about a week after veraison through to harvest. Smoke taint risk also depends on other factors such as intensity and duration of the fire, proximity of the vineyard to the fire, prevailing weather conditions and grape variety.
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If the wine is showing high levels of the volatile smoke phenols, we refer to this as smoke tainted wines. The volatile phenols can leave flavours in the wine including smoked meat, disinfectant, leather, char, salami or even ashtray.
These compounds come from smoke and they are absorbed directly by grapes exposed to smoke. Some of these compounds get converted by the grapevine into glycosylated precursors but can convert back, essentially acting as a pool of compounds waiting to be released. The conversion occurs during the fermentation process, which releases the smoky compounds into the wine. Volatile phenols can also be released in the mouth when the wine is tasted, enhancing any smoky flavours.
More details about vineyard risk factors can be found in the following information on the AWRI website here :
- Fact sheet: Smoke taint – entry into grapes and vineyard risk factors
- Fact sheet: Stubble burning – a possible source of smoke taint in grapes
- Fact sheet: Minimising the impact of prescribed burns on wine-grape production
- Article: I can smell smoke – now what?
Grape samples can be sent to designated laboratories for chemical analysis and identification of any volatile compounds and glycosylated precursors. This, coupled with a small-lot fermentation a few weeks before harvest, allows for an assessment of the likelihood of wines being affected by smoke.
The following organisations offer grape testing services in Australia:
Australian Wine Research Institute Commercial Services
If grapes have tested positive to smoke effects, its impact can be reduced by minimising extraction from skins by hand harvesting, keeping fruit cool and whole bunch pressing, or using oak to add complexity and mask some of the smokiness. Other options to reduce the effects of smoke taint in wine are to use carbon fining or dilution with unaffected wine.
More details about steps that can be taken in the vineyard and winery to minimise the sensory impacts of smoke exposure can be found in the following information on the AWRI website here
- Fact sheet: Smoke taint – practical management options for grapegrowers and winemakers
- Fact sheet: Treating smoke-affected grape juice with activated carbon
- Fact sheet: Treating smoke-affected wine with activated carbon
- Fact sheet: Remediation of smoke-affected wine by dilution
- Webinar: Tackling smoke taint head on: winery remediation options for smoke-affected juice and wine (AWRI webinar 23 July 2020)
Producers may make the decision not to harvest fruit for winemaking if the levels of smoke are too high. While there is no risk of carry-over smoke effects from one season to the next, there are factors to consider in managing the vineyard.
The AWRI factsheet ‘Managing smoke-affected vineyards where fruit is not harvested for winemaking’ provides advice on management practices and can be found here.
The webinar ‘Options and considerations for dealing with unharvested fruit in smoke-affected vineyards’ by the AWRI discusses in detail the key points to consider when managing a vineyard that will not be harvested for wine production.
Fire management authorities in several Australian states conduct controlled burns in an effort to minimise the impact on human life and property in the event of a bushfire. These burns are often carried out in autumn, when wine grapes may still be ripening and at risk of smoke damage.
Controlled burns are generally lower in intensity and of shorter duration than bushfires and will therefore pose a lower risk to grapes. However, smoke from any fire can damage grapes and all the factors mentioned above come into consideration. In addition, conditions may change during a burn and heighten the potential for smoke damage to vineyards. Growers should liaise with local fire authorities, monitor the fire and test grapes if they are concerned.
The factsheets below were developed in a Wine Australia project and contain the latest information for fire managers and vineyard managers to use in the planning of controlled burns to minimise the risk of smoke damage to vineyards.
Protocols for fire managers to minimise smoke taint in wine (Agriculture Victoria)
Protocols for vineyard managers to minimise smoke taint from prescribed burns (Agriculture Victoria)
For further information about fire damage or smoke affects, please contact the AWRI helpdesk on (08) 8313 6600 or firstname.lastname@example.org.
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