VA Filtration Smoke Taint Bulletin – August 2020
What is smoke taint and how do I know it is there?
We have all become far too familiar with smoke taint in wine over the past 3 years. Sadly, this has become a new reality for so many wineries. This is a quick update on the latest treatment methods related to the removal of smoke taint from wine. Drawing experience from 2008 and most recently 2017, highly tainted fruit can result in some very ashy, astringent, bacony wine (think of drinking red wine around a smoky camp fire). It is not one of those taints that is easy to mask or to remove and can be difficult to pick up in the juice prior to fermentation. There are hundreds of compounds related to smoke taint that are present in the wine. The AWRI has had the most extensive published research to date on smoke taint and have been able to analyze the bound glycosides related to smoke, which has helped us immensely in developing a reduction method. They are also able to analyze many of the free compounds including 4-methylguaiacol, Guaiacol, o-Cresol, p-Cresol, m-Cresol, Syringol, Methyl Syringol. There are some local labs now offering an expanded smoke panel in the USA fortunately and they do offer juice panels to check if grapes have seen smoke exposure.
Treatment in the Juice Stage
The BIG question is how to deal with this problem. There are several helpful tools in dealing with it, but no “magical” cure. One option is to flash the recently harvested fruit (reds only) to remove as much smoke taint from the skins before it has a chance to integrate with the juice. It is suspected that the smoke taint is concentrated in the skins of the berry due to some interesting observations of the contamination process in 2008 and 2017. Juice samples that showed little to no sign of smoke taint in 2008 resulted in highly tainted wine after fermentation and whites showed lower levels of smoke taint due to limited skin contact. In 2017 we did see the flash process reduce a significant amount of taint and we would definitely recommend exploring this option for reds. Smoke tainted white wines though are a lot harder to remediate due to their delicate aromatic profile.
We are planning on trialing a new process on white juice this year in order to target the bound compounds prior to fermentation. We hope to have some more information related to the success of this trial later this year.
Wine Stage and development of smoke taint
During fermentation, the level of smoke taint increases as fermentation proceeds. We think it is related to the breakdown of the glycosides during the fermentation process releasing the bound smoke. This needs more research however. To find out if wine is contaminated, a guaicaol analysis will prove its presence and show the level of taint. Ideally, you will want to run a smoke panel including Syringol and Cresol to get an idea on the extent of the smoke damage. Guaiacol levels can range from 4 ug/l to as high as 200 ug/l and Cresol and Syringol numbers vary from 1 ug/l to 30 ug/l and higher. Note that all analysis needs to be carried out before any oak products are added to the wine and after fermentation is complete.
The Treatment Process – Lessons learned from 2017 and breakthrough in the removal of bound smoke
The removal of the free compounds has always been fairly simple. The bound portion is the key though to reducing the smoke permanently and eliminate the return effect. After extensive research in 2018 a breakthrough was finally found. After testing a myriad of membranes and medias related to the removal of phenolics and glycosides, we stumbled on a process that was able to reduce BOTH the free and bound portion of the analyzable smoke compounds. The bound compounds include Syringol gentiobioside, Methylsyringol gentiobioside, Phenol rutinoside, Cresol rutinoside, Guaiacol rutinoside and Metylguaiacol rutinoside. Our testing during processing showed the reduction of Cresol rutinoside from 71 ug/l down to 34 ug/l after 3 passes and Syringol gentiobioside from 10 ug/l down to 3 ug/l after 3 passes. The ARC Process, as it is now called, was implemented in early 2020 and has successfully been deployed as a standard process for smoke taint processing. Due to the harsh nature of the ARC process, we also offer a process that targets only the free and leaves the glycosides untouched. Since the process of reducing smoke related glycosides is non-discriminatory, the desirable glycosides will also get reduced and this can affect mouth feel and flavor profile. If you are looking at a gentler method of reduction and are willing to risk a return affect, then we recommend waiting at least 9 months to treat the wine. For Pinot Noir and other delicate varieties, the least aggressive method might be best if smoke taint is minimal.
When to Process?
Historically we have suggested waiting to process. With our new ARC process we feel that processing after fermentation might be just as successful because of the reduction in the bound compounds. Again though, we do not have long term data on the success of earlier processing. We do know that the process works after letting the wine age for 6 months. We do not recommend going to new barrels though. There is a loss of oak compounds during processing. So we suggest neutral oak until processing can be completed.