Smoke Taint Update

Thomas Collins, PhD Washington State University Wildfires and Wine

• Overview of smoke taint & the 2017 vintage

• Review of smoke marker compounds

• Glycosides of smoke related phenols

• Risk assessment research project

View from the WSU Roza vineyard on 05 September 2017 Smoke taint

• Wines made from vineyards exposed to smoke from wildfires have can develop characteristic aromas and flavors – Smokey – Ashy – Cigar or cigarette smoke

• Strong ashy, cigar-butt aftertaste can also occur First smoke taint research report--2007

• Kennison, et al, demonstrated that fruit exposed to smoke produced wine which had smoke taint aromas and flavors

• Guaiacol, 4-methyl guaiacol, 4-ethyl guaiacol, 4-ethyl phenol, eugenol and furfural were identified in wines made with smoked grapes

guaiacol 4-methyl guaiacol syringol furfural 4 B.C. smoke event, August 1st-12th 2017

Wildfires in B.C. resulted in poor air quality for much of Washington Smoke exposure at Roza vineyard, August 02-12, 2017

0.6

0.5 3

0.4

mg/m 0.3 2.5 0.2 PM

0.1

0 1:07:09… 5:17:09… 9:27:09… 2:37:12… 6:47:12… 3:09:35… 7:19:35… 0:09:59… 8:41:30… 1:26:04… 5:36:04… 9:54:20… 2:41:20… 6:51:20… 3:53:48… 8:03:48… 16:47:09… 20:57:09… 13:51:50… 18:01:50… 22:27:12… 11:06:27… 15:16:27… 12:41:08… 16:51:08… 21:01:08… 14:39:35… 18:49:35… 22:59:35… 11:37:59… 15:49:59… 19:59:59… 12:51:30… 17:01:30… 21:16:04… 14:04:20… 18:14:20… 22:31:20… 11:06:31… 15:16:31… 19:33:48… 23:43:48… 12:20:17… Smoke exposure at Roza vineyard, August 02-12, 2017

0.6

0.5 3 3 TWA was less than 0.2 mg/m 0.4 mg/m

2.5 0.3 PM 0.2

0.1

• Berry samples analyzed for presence of smoke related volatile phenols and glycosides – Samples collected from August 3rd-12th did not have observable levels of free compounds or glycosides

• Combination of relatively low smoke density and pre-veraison fruit limited the extent of smoke taint from this smoke event Labor Day Smoke Event, September 5-8th 2017

Smoke from Eagle Creek fire, Jolly Mountain and Norse Peak fires covered much of the Columbia Basin as well as the Columbia Gorge Labor Day Smoke Event, September 5-8th 2017

PM2.5 was much higher than for the BC event—ranged from 0.7-0.9 mg/m3 at the Roza vineyard

Smoke from the Control wines from the Eagle Creek fire smoking trials have seen from the detectable levels of WA side of the smoke taint volatiles Columbia and glycosides Oregon & California fires

Significant wildfires in southern and central Oregon and the devastating fires in Sonoma and Napa counties starting October 9th Smoke from conifer bark

GC/MS chromatogram of smoke collected from burning conifer bark cresol - m guaiacol ethylguaiacol - methylguaiacol cresol 4 - - 4 o phenol Guaiacol Guaiacol is used as a marker for smoke exposure

Guaiacol or 2-methoxy phenol Guaiacol Guaiacol is used as a marker for smoke exposure

Guaiacol is produced by thermal degradation of lignin when wood or other plant material is burned Guaiacol or 2-methoxy phenol 4-Methyl Guaiacol 4-methyl guaiacol is usually used along with guaiacol as a marker for exposure 4-Methyl Guaiacol 4-methyl guaiacol is usually used along with guaiacol as a marker for exposure

4-MG is also produced during the thermal degradation of lignin 4-Methyl Guaiacol 4-methyl guaiacol is usually used along with guaiacol as a marker for exposure

4-MG is also produced during the thermal degradation of lignin

Both guaiacol and 4-methyl guaiacol are found in barrels, again from the thermal degradation of lignin in the oak wood 4-Methyl Guaiacol 4-methyl guaiacol is usually used along with guaiacol as a marker for exposure

4-MG is also produced during the thermal degradation of lignin

Neither guaiacol and 4-methyl guaiacol are well correlated with the perception of smoky characters in affected wines Lignin Lignin is an irregular highly cross-linked phenolic polymer found in woody plant material Lignin Lignin is an irregular highly cross-linked phenolic polymer

It cross-links with carbohydrate polymers such as cellulose to provide rigidity and strength to wood Lignin Lignin is an irregular highly cross-linked phenolic polymer

It cross-links with carbohydrate polymers such as cellulose to provide rigidity and strength to wood Lignin When lignin is heated, the bonds cross-linking the phenolic subunits can be cleaved, releasing guaiacol and other small volatile phenols

Cleave here to produce guaiacol Lignin When lignin is heated, the bonds cross-linking the phenolic subunits can be cleaved, creating guaiacol and other small volatile phenols

Cleave here to produce vanillin Volatile phenols 4-ethyl guaiacol Thermal degradation of lignin produces a range of small volatile phenols o-cresol All of these compounds have been found in smoke affected wines syringol

Parker et al, 2012 showed cresols could contribute to smoky character in wines 4-vinylguaiacol Smoke taint glycosides

• In addition to the free volatile phenols, glycosides are also present

• Glycosides are less volatile than the free compounds and generally odorless

• Glycosidic bond is acid labile and Guaiacol-glucoside can hydrolyze at wine pH Analysis of 2015 vintage wines from WA and CA

• Several wines affected by regional wildfires in 2015

• Free volatile phenols: – Guaiacol, 4-methyl guaiacol, syringol

• 23 Glycosides: – Guaiacol, 4-mg, cresols, syringol – Glucosides, di-glucosides, di-pentosides and pentosyl- glucosides Role of the glycosides in smoke taint

• Mayr, et al, 2014, reported that in a model system, the addition of both free volatile phenols and their glycosides produced the strongest off-aromas in a descriptive analysis experiment – Enzymatic activity in saliva hydrolyzes both mono- and di-saccharides – Variable hydrolysis dependent on glycosides present

• Glycosides are acid labile and will hydrolyze over time in affected wines, releasing free volatile phenols associated with smoky aromas Smoke taint project

• Develop a system for exposing vineyards to moderate levels of smoke for extended periods

• Monitor extraction of smoke compounds from fruit into the wine

• Evaluate techniques for mitigation of smoke related compounds in wines

Project funded by the Washington State Wine Commission Modular Hoop-house in Use: 2017 Smoking Trials

• 3 trials—Chardonnay, Merlot and Cabernet

• Chard and Merlot smoked with rangeland plants – Sage, rabbit brush, cheat-grass, prickly lettuce, etc.

• Cabernet smoked with cedar and fir bark mulch

• Chardonnay was smoked for 26 hours, Merlot and Cabernet for 48 hours Key Take-aways

• Smoke related compounds are present both as free compounds and as glycosides – Free compounds responsible for wine aromas – Glycosides play a role in the flavor/aftertaste – Glycosides hydrolyze over time to release more free compounds • Reverse osmosis can provide short term reduction of free compounds – Hydrolysis of glycosides is relatively quick at wine pH

• Removal/reduction of glycoside pool is a key component to mitigation of smoke taint in affected wines Thank you! GC chromatograms for several rangeland plants

Rabbit brush

Russian thistle

Wood mulch Guaiacol content of R.O. treated wines over time

14 June 12 August 10 October

µg/L 8 December February 6 April 4 June 2

0 Wine 3 Wine 20 Wine 25 Wine 32 Wine 40

34 Guaiacol content of R.O. treated wines over time

14 June 12 August 10 October

µg/L 8 December February 6 April 4 June 2

0 Wine 3 Wine 20 Wine 25 Wine 32 Wine 40

By December 2009 ~60% of these wines were perceptibly 35 affected again! Guaiacol released by strong acid hydrolysis one year after R.O. treatment

50 June August 40 October

(ug/L) December 30 February 20 April June 10 June hydrolyzed