With fires in Canada, Washington, Oregon and California, smoke taint is becoming a concern for the 2017 vintage. The stage of grapevine growth and development, smoke concentration, duration of exposure and the composition of smoke impact the level of aromatic precursors present in grapes. Winemaking practices strongly impact smoke taint levels in finished wines.
Assessing the level of smoke taint risk before harvest is strongly recommended in order to adjust the winemaking process to limit the extraction of smoke taint compounds.

How are grapes and vines affected by bushfire smoke?
Numerous volatile phenols are present in bushfire smoke and can be absorbed by grape berries and vine leaves during a smoke event. Vineyard and grape exposure to smoke may result in wines with undesirable sensory characteristics such as smoky, burnt, bacon, medicinal or ash, usually described as ‘smoke tainted’. 

How much smoke causes a smoke effect in wine?
Studies have shown that a single exposure to heavy smoke (30% obs/m) for 30 minutes at a sensitive stage of vine growth (7 days post veraison to harvest) was sufficient to cause a smoke effect in wine (Kennison et al. 2008). Whereas smoke effect characteristics such as smoke-like aromas and flavors are pronounced in wines produced from high smoke densities (20% obs/m) for short durations and low smoke densities (2.5% obs/m) for long durations. It is important to note that grape harvesting, handling and winemaking techniques can influence the creation of smoke effect in wine. 

What compounds are responsible for smoke taint?
The primary compounds in smoke responsible for taint are free volatile phenols (guaiacol, 4-methylguaiacol, o-cresol, p-cresol, m-cresol, etc) which are produced and released into the atmosphere when lignin in wood is burnt. 

How to assess the level of smoke taint risk
Vinquiry Laboratories by Enartis USA has developed a robust method for the quantification of Smoke Taint Markers (volatile and non-volatile) in grapes, juice and wine. Vinquiry Laboratories offers analysis for total guaiacol and 4-methylguaiacol, which have been identified as smoke taint markers. A representative grape, juice or wine sample is required. Sample volume: grapes = 5 clusters or 200 berries; juice or wine = 50 mL. 

When is the best time to have samples tested?The most effective time to test levels of volatile and non-volatile phenols in grapes is as close to harvest as possible. 

See our Winemaking Guidelines Red Wines and White Wines for recommendations on how to manage smoke taint grapes.