Introduction to Smoke Taint
Wine made from grapes exposed to bushfires smoke can exhibit unpleasant smoky, “ashy” characters, which have been attributed to the presence of smoke-derived volatile phenols (VPs) in free or glycosylated forms in grapes. VPs and, to a lesser extent the glyco-conjugated phenols, are located in the skin tissue of smoke-affected berries. The two most common VPs are guaiacol and 4-methyl-guaiacol. Both the free volatile phenols and their glycoside forms are important in the development of smoke taint and can be used as markers for smoke exposure.
Vps are higher in hard press juice while only a trace concentration (≤1 μg/L) of guaiacol could be detected in the free-run juice from grapes of smoke-affected vines. The release of a substantial quantity of guaiacol and other volatile phenols during the fermentation have been monitored, demonstrating the likely presence of a substantial concentration of phenols as glyco-conjugates. Glycosides are easily extracted into wine and can act as a pool of precursors which release volatile phenols during fermentation, wine aging and bottle storage (see chart: concentration of Vp’s depending on skin contact).
Fermenting reds to dryness on the skins, crushing and de-stemming white grapes, and whole bunch pressing of white wines resulted in 85%, 25%, and 18% extraction of glycosides, respectively.
Another study found that 72-87% of smoke derived volatile phenols exist in glyco-conjugated form at bottling and after 19 months of wine aging it was found that 70% of VPs remain bound.
Further, sensory investigation established the importance of both non-volatile glycol-conjugates and VPs on the in-mouth flavor characteristics of smoke-affected wines, and help write some guidelines to ameliorate smoke taint in your final wine.
How to Ameliorate Smoke Taint
Processing of Grapes and Wines:
- Hand harvesting: release of juice/skin contact is limited therefore extraction of negative flavors and precursors is limited.
- The exclusion of leaf material was shown to prevent the release of VPs from leaves into the wine/juice, washing grapes helps with removal of ash from the surface but VPs would have been absorbed at that stage.
- Keeping fruits cool after harvesting and processing at ≤10ºC provided less extraction of VPs from the skin (-50%).
- Increased extraction of guaiacol and 4-methylguaiacol was observed beyond 40% press yield.
Whole bunch press is more effective in reducing extraction of VPs in white wines.
- Minimizing skin contact at any point of the wine making process allowed for decreased extraction from the skin of a high number of VPs and glycosides.
- Cold fermentation decreases the extraction of phenolic compounds compared to normal fermentation.
Fining agents are routinely used at different stages of winemaking to address constituents that are considered to adversely affect juice or wine quality, and also have been used to remove volatile compounds responsible for the occurrence of various off-odors and flavors in wine.
- Carbon is regarded as a severe and relatively non-specific fining agent which can reduced the concentration of total volatile phenols/ glycosides between 58 and 71% (at a concentration of 0.6 g/L for 3 days, or 1-2 g/L for 24h)
- The use of specific yeast hulls presents a less severe alternative to decrease volatile phenols in wine and shown to reduce Vps with different efficiencies (20% reduction at 5 g/L concentration x 1h).
AEB products that can Adsorb Volatile Phenols
- Free4Fenol: deodorizing carbon
- Antibrett: Yeast hulls specific for adsorbing volatile phenols
- Fermoplus Pyr-off: Yeast nutrient with a yeast hulls matrix specific for adsorbing volatile phenols
Yeast and Yeast Nutrients:
Descriptive sensory analysis on smoke taint wine trials, showed the yeast strains most capable of reducing ‘smoke’, without compromising ‘fruit’ descriptors, are aromatic yeasts which increases aroma and palate complexity without beta-glucosidase activity.
Masking of smoke aromas was investigated with addition of oak and tannins. The addition of oak chips to fermentations resulted in higher guaiacol and 4-methylguaiacol concentrations. However, certain oak tannins added during the winemaking process can significantly reduce the perception of smoke-related sensory attributes. This was found to be because of the masking effect of flavors such as vanillin, acetovanillone, and syringaldehyde. Also, the mixture of yeast hulls and mannoproteins showed promising results for removal of VPs and may provide another alternative to decreasing faulty aroma and taste.
AEB products that can help "Mask"
Ellaginan Barrique Liquid line: different ellagic tannin which can be evaluated during or at the end of fermentation to optimize their utilization and efficacy.
Ellagitan Extreme: ellagic tannin with high vanillin content, often used in red wines to hide vegetal characters and to open them up, helping to release a bouquet richer in cherries and red fruits.
Protan Peel: proanthocyanidins tannin from grape pomaces, it helps to supplement the wine and balance for shorter skin maceration.
SuperMANN: yeast mannoprotein
Batonnage Elevage: yeast polysaccharide
Suggested guidelines with AEB products:
Add 2ml/hL of Endozym ICS 10 Éclair to speed up depectinization only after press.
Add Free4Fenol to free run/hard press in dosage 3-6 #/1000 gal.
Add 1#/1000 gal Bentogran and 0.5#/1000 gal of Gelsol to help carbon removal (sedimentation or flotation).
Inoculate Fermol Chardonnay at 1-2 #/1000 with Fermoplus Energy Glu 3.0 0.25-0.5 #/1000 during rehydration. Fermentation temperature 60-65 F.
Add Fermoplus Tropical 2-4 #/1000 gal at beginning of fermentation to maximize fermentation aromas.
Add Elevage Glu or Batonnage Elevage at 2/3 fermentation at 2#/1000 gal to protect fermentation aromas.
Evaluate after bench trials addition of:
- 2-6#/1000 gal, SuperMann 1-4 #/1000 gal, Ellagitan Barrique Liquid.
Reds & Rosé:
Add 2 #/1000 gal Ellagitan Extreme and 1#/1000 gal of Protan Peel directly to the crusher.
Add 2 #/1000 gal of Fermoplus PyrOff
Inoculate Fermol Mediterranée, Fermol Premier Cru (bigger reds) or Fermol PB 2033 (rosé or light reds) at 1-2 #/1000 with Fermoplus Energy Glu 3.0 0.25-0.5 #/1000 during rehydration. Fermentation temperature 65-68 F.
Add Fermoplus DAP Free 2-4 #/1000 gal at the beginning of fermentation to maximize fermentation aromas.
Add Batonnage Plus elevage at 2/3 of fermentation at 1#/1000 gal
Evaluate after bench trials addition of:
- 2-6#/1000 gal Antibrett, Free4Fenol 3-6 #/1000 gal
Evaluate after bench trials addition of Ellagitan Barrique Liquid 1-2 #/1000 gal
- Beta-glucosidase enzymes release some of the glycosides and increases VPs into the wine. Because it has been proven that glycosides are stable in the bottle, we suggest to evaluate the addition of Endozym Beta Split only at the end of fermentation with bench trials. In any case, the enzyme can help to understand how much smoke taint is being hidden in your wine and might come out with aging.
- Blending can be an effective option for remediation of smoke-affected wine. Dilution with 75% or more of an unaffected wine were not significantly different from the unaffected wine alone. The level of dilution will depend on the level of smoke compounds in the wine and the sensory properties of the unaffected wine used as the blending wine, but it can be an option also to increase color in reds/rose’.
- To avoid the risk of tainting your barrels, we recommend the use of liquid tannins which are fast to integrate.
- These techniques may help reduce the extraction and expression of smoke taint compounds, but they are unlikely to eliminate the problem completely: therefore, we recommend to market for quick sale to avoid smoke-related characteristics in bottle as wine ages.
Ristic, R., Osidacz, P., Pinchbeck, K. A., Hayasaka, Y., Fudge, A. L., & Wilkinson, K. L. (2011). The effect of winemaking techniques on the intensity of smoke taint in wine. Australian Journal of Grape and Wine Research, 17(2), S29-S40.
Krstic, M. P., D. L. Johnson, and M. J. Herderich. "Review of smoke taint in wine: smoke‐derived volatile phenols and their glycosidic metabolites in grapes and vines as biomarkers for smoke exposure and their role in the sensory perception of smoke taint." Australian journal of grape and wine research 21 (2015): 537-553.
Ristic, R., van der Hulst, L., Capone, D. L., & Wilkinson, K. L. (2017). Impact of bottle aging on smoke-tainted wines from different grape cultivars. Journal of agricultural and food chemistry, 65(20), 4146-4152.
Langa, N. (2019). Amelioration of smoke taint in wine using commercially available and legally permissible additives.
Jiménez-Moreno, Nerea, and Carmen Ancín-Azpilicueta. "Sorption of volatile phenols by yeast cell walls." International Journal of Wine Research 1 (2009): 11-18.