IVAS 2022 banner
IVES 9 IVES Conference Series 9 IVAS 9 IVAS 2022 9 Smoke taint: Understanding and addressing the compositional consequences of grapevine exposure to smoke

Smoke taint: Understanding and addressing the compositional consequences of grapevine exposure to smoke

Abstract

Climate change has become a major challenge for grape and wine production around the world. Grapegrowers and winemakers are not only affected by increasing temperatures and prolonged drought, but by vineyard exposure to bushfire/wildfire smoke, which can taint grapes and wine, causing significant revenue losses where unpalatable smoky, ashy characters render wine unsaleable. Considerable research has therefore been undertaken over the past ~20 years to understand the compositional and sensory consequences of grapevine exposure to smoke. 

Early studies measured guaiacol and 4-methylguaiacol as markers of smoke taint, because these compounds were oak volatiles (deriving from the thermal degradation of lignin during the toasting process of cooperage) known to impart smoke-related sensory attributes, and analytical methods existed for their quantitation in wine. Today, a suite of volatile phenols (guaiacols, cresols and syringols) are measured as smoke taint marker compounds – in both free and glycosylated forms.

Volatile phenols have been identified as constituents of smoke, and can be found in grapes immediately after smoke exposure, but are rapidly glycosylated, giving volatile phenol glucosides, gentiobiosides, diglycosides and rutinosides. During fermentation, some glycoconjugates are hydrolysed by yeast and/or enzymes, releasing volatile phenols into wine. However, a significant portion of the glycoconjugate pool remains after winemaking, and can contribute to the sensory perception of smoke taint due to in-mouth hydrolysis. Ideally, smoke taint risk assessments should therefore comprise determination of both volatile phenols and volatile phenol glycoconjugates, either directly (by GC-MS and LC-MS/MS, respectively) or indirectly (by GC-MS, before and after acid or enzyme hydrolysis).

The detection/evaluation of smoke taint is further complicated by the natural occurrence of some volatile phenols (and their glycoconjugates) in the fruit (and therefore wine) of some grape varieties, without smoke exposure, for example Shiraz and Petit Sirah. Research is therefore underway to establish the varietal, regional and temporal variation in naturally-occurring volatile phenol glycoconjugate concentrations, to better inform decision-making in the lead up to vintage, where vineyards are potentially impacted by smoke. 

This presentation will provide an overview of the chemistry of smoke taint, the analytical methods available for determination of smoke taint, and the latest strategies for mitigation and amelioration of smoke taint in grapes and wine. 

DOI:

Publication date: June 23, 2022

Issue: IVAS 2022

Type: Article

Authors

Professor Kerry Wilkinson¹

¹ Department of Wine Science, Waite Research Institute, The University of Adelaide, Australia

Contact the author

Keywords

grapes, glycosylation, smoke taint, volatile phenols, wine

Tags

IVAS 2022 | IVES Conference Series

Citation

Related articles…

Management of grapevine water status with the DSS Vintel® provides evidence of sustainable irrigation strategies while maintaining wine quality of Pinot gris in Friuli-Venezia Giulia region, NE italy

Deficit irrigation strategies can be valuable means to improve grape quality while saving important amounts of water. A simple way to use deficit irrigation can be based on irrigating a vineyard with a determined level of crop evapotranspiration. Using a precise physiological parameter indicating water status, irrigation could be managed to maintain a specific pre-dawn leaf water potential.

Microwave-assisted maceration and stems addition in Bonarda grapes: effects on wine chemical composition and sensory properties over two vintages

AIM: Bonarda, the second red grape variety in Argentina, produces high yields per hectare generating, in several cases, wines with low levels of quality compounds.

Combining effect of leaf removal and natural shading on grape ripening under two irrigation strategies in Manto negro (Vitis vinifera L.)

The increasingly frequent heat waves during grape ripening pose challenges for high quality wine grape production. Defoliation is a common practice that can improve the control of diseases in bunches, but also it increases the exposure to sunlight. Grapes exposed to solar radiation reach temperatures over the optimum for berry development and maturation. This makes the development of irrigation and canopy management techniques of great importance to maximize yield and grape quality. A field experiment was carried out during 2021 using Manto negro wine grapes to study the effect of applied irrigation and different light exposure levels on grape quality. Two irrigation treatments were imposed based on the frequency and amount of water doses in a four-block experimental vineyard at Bodega Ribas (Mallorca). Three light exposure treatments were randomly applied in each irrigation plot. The light treatments included exposed clusters from pea size, non-exposed clusters, and shaded clusters after softening. Leaf area index and canopy porosity was estimated every 2 weeks. Midday leaf water potential was measured weekly. Additionally, apparent electrical conductivity was measured between rows to estimate the soil water content variability. Light and temperature sensors were installed at the bunch level to quantify the differences in bunch temperature and light intensity among treatments. The effect of irrigation and cluster light exposure on berry weight, TSS, TA, malic acid, tartaric acid, K+, and pH were analysed at 5 moments along grape ripening. During different heat waves, the natural shading technique decreased the maximum bunch temperature around 10 °C respect to the exposed bunches in both irrigation strategies. The combination of defoliation and shading techniques after softening decreased TSS at harvest and affected most of the quality parameters during the last stages of ripening, showing an interesting technique to delay ripening in warm viticulture areas.

Cross analytical and sensory differentiation of monovarietal white wines from four autochthonous grape varieties: focus on macromolecules

White wines contain macromolecules such as proteins, phenolic compounds and polysaccharides. On a sensory
level, these compounds contribute to the ‘mouthfeel’ that differentiates the white wines worldwide [1].

Colloidal color stabilization in wine: A comparative study of Saccharomyces and non-Saccharomyces mannoproteins

Structure-function relationships between the polysaccharide part of S. cerevisiae Mannoprotein Pools (MPs) and their potential to interact with anthocyanins and Protein-Tannins aggregates was previously assessed [1,2].