Smoke taint is a broad term for a set of

smoke Smoke is a suspension of airborne particulates and gases emitted when a material undergoes combustion or pyrolysis, together with the quantity of air that is entrained or otherwise mixed into the mass. It is commonly an unwanted by-produc ...

imparted compounds found in affected

wine Wine is an alcoholic drink typically made from fermented grapes. Yeast consumes the sugar in the grapes and converts it to ethanol and carbon dioxide, releasing heat in the process. Different varieties of grapes and strains of yeasts are m ...

s, constituting a

wine fault A wine fault or defect is an unpleasant characteristic of a wine often resulting from poor winemaking practices or storage conditions, and leading to wine spoilage. Many of the compounds that cause wine faults are already naturally present in wine ...

. Increasing incidences of smoke tainted wines are an important issue, given the recent occurrences of

wildfires A wildfire, forest fire, bushfire, wildland fire or rural fire is an unplanned, uncontrolled and unpredictable fire in an area of combustible vegetation. Depending on the type of vegetation present, a wildfire may be more specifically identif ...

or bushfires in

grape producing regions during the growing seasons. Examples of wildfires resulting in smoke tainted wines include the fires in South Africa in late 2017,

October 2017 Northern California wildfires The October 2017 Northern California wildfires, also known as the Northern California firestorm, North Bay Fires, and the Wine Country Fires were a series of 250 wildfires that started burning across the state of California, United States, b ...

, the

2019–20 Australian bushfire season The 201920 Australian bushfire season (Black Summer), was a period of bushfires in many parts of Australia, which, due to its unusual intensity, size, duration, and uncontrollable dimension, is considered a megafire. The Australian National ...

, and the 2020

Glass Fire The Glass Fire was a wildfire in Northern California, that started on September 27, 2020, at 3:48 AM ( PDT) from an undetermined cause and was active for 23 days. It was part of the 2020 California Wildfires and the 2020 Western United States wi ...

in Northern California. Whenever ambient smoke comes into contact with developing grapes on vines for a period of time, there is a risk that the grapes will carry smoke taint and impart this in wine made from them. The risk is higher with red wines, because their fermentation process includes the grape skins. Around 20-25 percent of people are estimated to not be able to taste the smokiness, possibly because of a lack of enzymes in their saliva.

Causes

Smoke taint occurs when developing grapes are exposed to the smoke from wildfires. There are a number of factors that will determine the level of impact the smoke will have on the berries, including the state of berry development during the episode, the grape variety, the type and concentration of smoke and the duration of exposure. Wildfires in forested areas tend to burn a lot of wood, releasing volatile

phenols In organic chemistry, phenols, sometimes called phenolics, are a class of chemical compounds consisting of one or more hydroxyl groups (— O H) bonded directly to an aromatic hydrocarbon group. The simplest is phenol, . Phenolic compounds are ...

into the atmosphere. When these are absorbed by developing grapes in nearby vineyards, they can bind to grape sugars within the grapes. These bound phenols, known as

glycoside In chemistry, a glycoside is a molecule in which a sugar is bound to another functional group via a glycosidic bond. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycoside ...

s, are likely to be odorless and tasteless until the bond with the sugar is broken during winemaking processes or aging. When the volatile phenols become unbound, the characteristic "smoky" flavor is likely to become detectable. This bond can also become undone upon tasting, when an affected wine comes in contact with enzyme-containing saliva. Thus, smoke taint can exist masked in wine for a period of time before it becomes apparent.

Sensory compounds and impacts

The major volatile compounds responsible for smoke taint include

guaiacol Guaiacol () is an organic compound with the formula C6H4(OH)(OCH3). It is a phenolic compound containing an methoxy functional group. Guaiacol appears as a viscous colorless oil, although aged or impure samples are often yellowish. It occurs wid ...

and methylguaiacol. Others include ortho-, meta- and para-

cresol Cresols (also hydroxytoluene or cresylic acid) are a group of aromatic organic compounds. They are widely-occurring phenols (sometimes called ''phenolics'') which may be either natural or manufactured. They are also categorized as methylphenol ...

as well as

syringol Syringol is the organic compound with the formula HO(CH3O)2C6H3. The molecule is a phenol, with methoxy groups in the flanking (2 and 6) positions. It is the symmetrically dimethylated derivative of pyrogallol. It is a colorless solid, althou ...

and methylsyringol. There are a number of enological laboratories around the world that can analyze for the presence of these compounds and help potentially affected wineries interpret the results. Similar to

cork taint Cork taint is a broad term referring to a wine fault characterized by a set of undesirable smells or tastes found in a bottle of wine, especially spoilage that can only be detected after bottling, aging and opening. Though modern studies have sho ...

, a wine can suffer from a minor, barely detectable case of smoke taint or it can be so obvious as to render the wine undrinkable. Descriptors for the smell and taste of a smoke tainted wine include smoky, wood smoke, chargrill, smoked meats, bacon and ashtray. The taste tends to be persistent, lingering long after the wine has been spat out or swallowed. Some smoke-taint compounds can be very similar to oak-aging compounds, especially if a wine has been aged in oak with a high level of toast. There is some anecdotal evidence that smoke taint can also impact the texture of wine, resulting in what some describe as a "hard" finish.

Treatments

Berries, grape juice and wine can be tested for the presence of volatile phenols indicating smoke taint, the primary markers being guaiacol and 4-methylguaiacol. If found, there are measures that can be taken to minimize, remove/reduce or counterbalance the impact of smoke taint at various stages of the winemaking process. Common treatments include minimizing skin contact and maceration, adding enological

tannin Tannins (or tannoids) are a class of astringent, polyphenolic biomolecules that bind to and precipitate proteins and various other organic compounds including amino acids and alkaloids. The term ''tannin'' (from Anglo-Norman ''tanner'' ...

s and/or oak chips to contribute to structure and counterbalance the impact of smoke taint, and the use of fining and/or filtration to remove/reduce some of the smoke compounds.

References

{{reflist Wine chemistry Oenology