Smoke Taint Update. Thomas Collins, PhD Washington State University

Transcription

1 Smoke Taint Update Thomas Collins, PhD Washington State University

2 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

3 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

4 First smoke taint research report 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 4 guaiacol 4-methyl guaiacol syringol furfural

5 B.C. smoke event, August 1 st -12 th 2017 Wildfires in B.C. resulted in poor air quality for much of Washington

6 0.6 Smoke exposure at Roza vineyard, August 02-12, 2017 PM 2.5 mg/m :47:09 20:57:09 1:07:09 5:17:09 9:27:09 13:51:50 18:01:50 22:27:12 2:37:12 6:47:12 11:06:27 15:16:27 12:41:08 16:51:08 21:01:08 14:39:35 18:49:35 22:59:35 3:09:35 7:19:35 11:37:59 15:49:59 19:59:59 0:09:59 8:41:30 12:51:30 17:01:30 21:16:04 1:26:04 5:36:04 9:54:20 14:04:20 18:14:20 22:31:20 2:41:20 6:51:20 11:06:31 15:16:31 19:33:48 23:43:48 3:53:48 8:03:48 12:20:17

7 Smoke exposure at Roza vineyard, August 02-12, PM 2.5 mg/m TWA was less than 0.2 mg/m 3 16:47:09 20:57:09 1:07:09 5:17:09 9:27:09 13:51:50 18:01:50 22:27:12 2:37:12 6:47:12 11:06:27 15:16:27 12:41:08 16:51:08 21:01:08 14:39:35 18:49:35 22:59:35 3:09:35 7:19:35 11:37:59 15:49:59 19:59:59 0:09:59 8:41:30 12:51:30 17:01:30 21:16:04 1:26:04 5:36:04 9:54:20 14:04:20 18:14:20 22:31:20 2:41:20 6:51:20 11:06:31 15:16:31 19:33:48 23:43:48 3:53:48 8:03:48 12:20:17

8 Smoke Exposure at Roza vineyard Berry samples analyzed for presence of smoke related volatile phenols and glycosides Samples collected from August 3 rd -12 th 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

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

10 Labor Day Smoke Event, September 5-8 th 2017 PM 2.5 was much higher than for the BC event ranged from mg/m 3 at the Roza vineyard Smoke from the Eagle Creek fire seen from the WA side of the Columbia Control wines from the smoking trials have detectable levels of smoke taint volatiles and glycosides

11 Oregon & California fires Significant wildfires in southern and central Oregon and the devastating fires in Sonoma and Napa counties starting October 9th

12 Smoke from conifer bark GC/MS chromatogram of smoke collected from burning conifer bark phenol o-cresol m-cresol guaiacol 4-methylguaiacol 4-ethylguaiacol

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

14 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

15 4-Methyl Guaiacol 4-methyl guaiacol is usually used along with guaiacol as a marker for exposure

16 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

17 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

18 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

19 Lignin Lignin is an irregular highly cross-linked phenolic polymer found in woody plant material

20 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

21 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

22 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

23 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

24 Volatile phenols Thermal degradation of lignin produces a range of small volatile phenols All of these compounds have been found in smoke affected wines Parker et al, 2012 showed cresols could contribute to smoky character in wines 4-ethyl guaiacol o-cresol syringol 4-vinylguaiacol

25 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 can hydrolyze at wine ph Guaiacol-glucoside

26 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 pentosylglucosides

27 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

28 Develop a system for exposing vineyards to moderate levels of smoke for extended periods Smoke taint project 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

29 Modular Hoop-house in Use:

30 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

31 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

32 Thank you!

33 GC chromatograms for several rangeland plants Rabbit brush Russian thistle Wood mulch

34 Guaiacol content of R.O. treated wines over time µg/l June August October December February April June 2 0 Wine 3 Wine 20 Wine 25 Wine 32 Wine 40 34

35 Guaiacol content of R.O. treated wines over time µg/l June August October December February April June 2 0 Wine 3 Wine 20 Wine 25 Wine 32 Wine By December 2009 ~60% of these wines were perceptibly affected again!

36 Guaiacol released by strong acid hydrolysis one year after R.O. treatment (ug/l) June August October December February April June June hydrolyzed 0 36