Review of the Effects of Grapevine Smoke Exposure and Technologies to Assess Smoke Contamination and Taint in Grapes and Wine

Abstract

Grapevine smoke exposure and the subsequent development of smoke taint in wine has resulted in significant financial losses for grape growers and winemakers throughout the world. Smoke taint is characterized by objectional smoky aromas such as “ashy”, “burning rubber”, and “smoked meats”, resulting in wine that is unpalatable and hence unprofitable. Unfortunately, current climate change models predict a broadening of the window in which bushfires may occur and a rise in bushfire occurrences and severity in major wine growing regions such as Australia, Mediterranean Europe, North and South America, and South Africa. As such, grapevine smoke exposure and smoke taint in wine are increasing problems for growers and winemakers worldwide. Current recommendations for growers concerned that their grapevines have been exposed to smoke are to conduct pre-harvest mini-ferments for sensory assessment and send samples to a commercial laboratory to quantify levels of smoke-derived volatiles in the wine. Significant novel research is being conducted using spectroscopic techniques coupled with machine learning modeling to assess grapevine smoke contamination and taint in grapes and wine, offering growers and winemakers additional tools to monitor grapevine smoke exposure and taint rapidly and non-destructively in grapes and wine.

Evaluation of Different Interstimulus Rinse Protocols on Smoke Attribute Perception in Wildfire-Affected Wines

“…With the increase in wildfire occurrence in wine regions around the globe, there are new challenges that winemakers face. Due to global climate change, it is estimated that elevated temperatures will increase the number of very high to extreme fire danger days by up to 70% by 2050, along with a lengthening of the wildfire season [ 1 ]. In 2021, the California wildfire season began in April, months before their traditional start, and will last through the grape growth and harvest season.…”

“…The concentration of these compounds in the wine is heavily dependent on grape varietal, time in the growth cycle, duration of exposure, and environmental conditions, such as wind and topography, along with wine production practices [ 3 , 4 ]. These smoke volatiles then enter the grapes through the leaves or from direct absorption by the berries, with a higher concentration found in the skin than the pulp [ 1 ].…”

“…It has been observed that retronasally the best-estimated threshold of guaiacol is 13 µg/L, 4-methylguaiacol is 65 µg/L, and syringol is 1650 µg/L in water [ 5 ]. These values may be different in wine systems, with research showing that higher concentrations are required for the orthonasal detection of these compounds in wine over water, along with different varieties of wine having differing thresholds [ 1 ]. Some of these phenols, predominantly guaiacol and 4-methylguiacol, can be introduced during winemaking through fermentation and aging in heavily toasted oak.…”

Thinking Inside the Box: A Novel Approach to Smoke Taint Mitigation Trials

“…Vineyard exposure to smoke can taint grapes due to the absorption of smoke-derived volatile compounds, including volatile phenols [ 7 , 8 , 9 ], which can impart smoky, medicinal, burnt rubber and ashy characters to wine [ 8 , 10 , 11 ]. In the last 5 years, fires have affected one or more vintages in prominent wine regions in Australia, Canada, Chile, New Zealand, South Africa and the USA [ 12 , 13 ], and revenue losses arising from ‘smoke taint’ are thought to be in the hundreds of millions of dollars [ 14 , 15 ]. Strategies that mitigate or ameliorate the effects of vineyard smoke exposure are therefore needed.…”

Digital Smoke Taint Detection in Pinot Grigio Wines Using an E-Nose and Machine Learning Algorithms Following Treatment with Activated Carbon and a Cleaving Enzyme

“…The degree of smoke taint in the final wine depends on several factors, including the timing and duration of smoke exposure and winemaking practices such as yeast selection and skin contact time during fermentation [3,6,11,12]. Some techniques have been investigated to mitigate the effects of grapevine smoke exposure in-field and to find methods for ameliorating smoke taint in the final wine.…”