Smoke Taint 101

Smoke Taint 101

Definition:

Smoke taint refers to the smoky/ash like characters in wines made from grapes exposed to smoke from wildfires. These are undesirable characters and can be described as smoky, burnt, ash smoky bacon and ashtray.

It started to be an issue since 2003 vintage in Australia and more recently, other part of the world such as California and Europe. AWRI in Australian has done extensive research on this subject.

What is smoke taint:

When woods are burnt, the smoke escapes into the atmosphere which can travel hundreds of kilometers. When the vines come in contact with smoke, they start its natural defence mechanisms and look at how to detoxify the smoke when it actually enters the into the leaves or the grapes. As smoke is toxic to the plant, they will attempt to detoxify by binding with compounds so that it makes it more less of an impact to the plant. It binds with the volatiles volatile phenols, a conversion of biotransformation to *glycoconjugates happens. Grapes and leaves uptake the volatiles and biotransform it to glycoconjugates. Grapes and the resulting wines may contain free volatiles (guauacol) and bound forms (glycoconjugates).

How does it get to the berries:

Through direct absorption from the environment from the from the smoke particles, the particulate matter in the environment, directly onto the berries.  Vine doesn’t have a defence system to prevent the smoke from entering. What they do is to detoxify by binding it.

How long does vines need to be exposed to smoke to get the taint.

It’s impacted by by many, many factors such as the concentration of the smoke, the duration, sometimes how many repeated events of smoke there are whether it’s day or night because it obviously impacts on humidity and temperature and aspect and distance. so all of these all of these pretty much come into play. So there’s no real formula to say.

Can it be prevented?

Vineyard sensors and satellite imagery. Both early stages.

actually sensors in the vineyards and they can identify when there’s a spike event or not. And the real the real interesting challenge is going forward is actually having that satellite data and the imagery that we’ll be able to to provide that kind of information in real time and that’s one of the projects that we’re also working on at the moment.

When are grapes more sensitive to smoke?

No safe period. But when berry side is less than 2 mm (early growing stage) it’s less at risk. So early growing stage.

In the past, fires tend to happen later in the vintage, ie 2020 happened around harvest time but this is less predictable and it happens earlier and earlier.

Smoke taint is additive so if it happens early in the growing season, it stays there.  The tiny good news is, it doesn’t carry over between vintages.

Smoke is high variable.  AWRI research shows that the valley bottom is easy to accumulate smoke.

Think smoke taint as an iceberg. There is a small part you can see from the surface but a lot more you can’t see. It’s not something that can be detected by smell. Some taint can only appear when you taste the wine.  This is because  smoke (volatile phenol glycosides) is partially hydrolyzed (水解). They are hydrolyzed over a long period of time. during fermentation that process is accelerated, but that process also continues on as the wine ages. So you have this volatile phenols and the sugars and what happens through hydrolysis because why is an acid medium is that they cleave apart because that bond is actually relatively weak and so they cleave apart through fermentation and also through through through ageing. And so therefore, we can essentially what happens is that you have more of those volatile phenols being created as the wine ages.

So what is in fact is happening there is that you actually have bacteria in your tongue in your mouth that actually have that ability, that that bacterial ability to actually cleave off that same the separate the volatile phenols from the sugars and actually ended up with a, with a what we call it some of that Nashi character. So again that’s sort of that, that chemistry is also again quite complex, but that also does does occur, actually when you taste a wine.

What can a producer do?  

-small ferments in early stages

-send samples to AWRI to analyses so producers can make informed decisions. They can decide not to pick those grapes.

Can you remove smoke taint from wine?

To some extent but very costly such as reverse osmosis, nano filtration, carbon (stripe out lots of flavours and colour)

Blending back 2-3% the tainted wines with very large volumes of sound taint free wines – not a viable option for most producers with regionally specific labels.

Ways to minimise the extraction of smoke:

-hand harvest

-remove leaf material

-keep fruit cool (10C) less extraction of smoke-related compounds at this temperature.

-Whole bunch press (for white wines) have shown some positive results

-Separate press fractions

-use of enzymes to increase breakdown of berry structure.

-Addition of oak chips and tannins to reduce intensity of smoke effect

-Avoid Barrel ageing if barrels are contaminated with smoke taint in previous fill

-Market wine for immediate consumption (as smoke taint will increase with time)

This is part of the MW study programme webinar on 30/11/2022

About this session:

Smoke taint refers to the smoky/ash like characters in wines made from grapes exposed to smoke from wildfires. This presentation summarises why smoke taint is a threat to global viticulture and draws on key work, over eighteen years, including research undertaken by the AWRI.

Presenter:

Con Simos is a winemaker by background with a Bachelor of Applied Science in Oenology from Roseworthy Agricultural College and a Masters in Business Administration from the University of South Australia.

Con is the Group Manager – Industry Development and Support The primary objective of the Industry Development and Support group is to disseminate research outcomes, provide technical and practical support to the Australian grape and wine sector.

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