Ref: Herve E., Price S. and Burns G. Free Guaiacol and 4-Methylguaiacol as Markers of Smoke Taint in Grapes and Wines: Observations from the 2008 Vintage in California. Proceedings 8e Symposium International d’OEnologie, Bordeaux France 15-17 June 2011.
Checking Grapes and Wines for Smoke Taint Background
“Smoke Taint” in wines was first identified as a serious problem following the 2003 wildfires in Australia and British Columbia. Subsequent fires in Australia during 2006 and 2007 caused additional losses in the millions of dollars. The California wildfires of 2008, with over 1,700 individual fires at their peak, caused smoke to cover most of Northern California during June and July.
Although it was too early to know the extent of smoke taint problems from the 2008 California fires, ETS Laboratories developed an analytical tool to screen grapes for smoke taint. This tool helped growers and winemakers identify potential problems and take immediate corrective actions whenever possible. In addition, ETS offered analysis of smoke taint markers in juice and wine. Smoke Taint Markers
“Smoke taint” is caused by a wide range of volatile phenols. Phenols in smoke are absorbed on vines and grapes and end-up in finished wines where they can cause objectionable odors described as “burnt”, “smoked fish”, “salami”, “ash” and “ashtray”.
Guaiacol and 4-methylguaiacol have been identified as the primary indicators of smoke taint. Both appear to be present in all smoke damaged wines and their concentration in unoaked wines usually correlates to the degree of taint present.Current Research
“Smoke Taint” research has been conducted primarily in Australia. Current research and observations suggest that the uptake of smoke compounds is greater immediately post-veraison. Vines do not need to be exposed to thick smoke to produce tainted wines. There is strong evidence that smoke taint compounds absorbed by vines are partly bound to glycosides, making them difficult to detect through sensory evaluation of grapes.
Vineyard washing treatments have not been successful in removing smoke taint compounds. Since smoke compounds are readily transferred from juice to wine during skin contact, mitigation actions during red winemaking don’t seem to be successful. On the other hand, final concentrations in white wines are highly dependent on harvesting and winemaking parameters and techniques. Applications
The main indicators of smoke taint in both grapes and wine, guaiacol and 4-methylguaiacol, can be used both to screen grapes and assess the intensity of smoke taint in wines. In Australia, grapes have been reportedly downgraded for guaiacol levels in the low µg/kg(ppb) range.
When a wine is suspected to be impacted by smoke, the determination of guaiacol and 4-methylguaiacol can often confirm the presence of taint and its intensity. Knowing the levels of both compounds often helps to make decisions when considering treatments to remove smoke taint from wine. Since significant amounts of guaiacol and 4-methylguaiacol can be released into wine by toasted oak, however, it is often preferable to submit wine that did not have any contact with oak, or alternately from “neutral” barrels.Berry Sampling
Testing berry samples is the most effective way to detect smoke taint. Berry samples can be taken in the vineyard or directly from harvest containers. A good sampling program is essential to ensure that the sample is representative. Spatial variability is particularly important when selecting berries, since location within the vineyard can determine exposure to smoke particles.
Juice and Wine Sampling
|• ||A representative sample of 200 to 400 berries taken from at least 20 to 40 vines should be collected in the vineyard.|
|• ||Cluster samples require special handling. A $30 sample preparation fee will apply to all samples submitted as clusters. We encourage our clients to submit berry samples to minimize additional sample preparation fees.|
The smoke taint panel measures the primary markers of smoke taint, guaiacol and 4-methylguaiacol. Juice testing is not the preferred tool for screening fruit before harvest. Accumulation of smoke compounds in skin makes berry testing the method of choice for preharvest screening. Testing wine samples for smoke taint is a useful tool for evaluating perceived sensory impact and making decisions regarding taint removal treatments.
This document is a compilation of information and views from various sources provided for the convenience of our clients. Information in this document is provided "as is" without warranty of any kind, either expressed or implied, including but not limited to the warranties of merchantability, fitness for a particular purpose and freedom from infringement. User assumes the entire risk as to the accuracy and the use of this document. This document may be copied and distributed subject to the following conditions: 1) All text must be copied without modification and all pages must be included; 2) All copies must contain ETS's copyright notice and any other notices provided therein; and 3) This document may not be distributed for profit. All trademarks are acknowledged. Copyright ETS Laboratories 2001-2013.
|• ||Juice and wine samples should have a minimum volume 60 mL without headspace.|
|• ||Wine samples should be taken prior to aging in oak.|