31 Jan 2020
tagged with smoke taint , RD&E , fire , smoke effects
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When there is smoke on the horizon, it is natural to be concerned about what impact it may have. However, as we’ll explore in this article, just because smoke may be visible (or can be smelled) it doesn’t mean that you need to be concerned about smoke affecting your glass of wine.

An ancient dilemma, but a recent area of study

Fire is part of the Australian and global landscape and has been for thousands of years.

The study of the impact of smoke on grapes is more recent, commencing in 2003 following serious and widespread fires in south eastern Australia. Since that time, smoke impacts on grapes have been seen across wine-producing nations in Europe, North America and Africa. It has been a key area of research investment for Wine Australia and today, Australia is the leading nation when it comes to understanding smoke effects on wine and winegrapes.

Key facts about smoke effects

  • smoke affects the grapes, not the vines
  • there is no carry over between seasons
  • the risk is greatest close to harvest
  • fuel source doesn’t matter – smoke is smoke
  • proximity and age of smoke affect the level of risk
  • characteristics of smoke in wine change over time and are experienced differently by different people. 

Risk factors

Researchers in Australia and around the world have learned a great deal about how smoke affects wine in a relatively short period of time.

What we know is that the effects of smoke are dictated by the age of the smoke, the proximity to the fire, duration of smoke exposure, geography, weather conditions and how close the grapes are to ripening. When grapes are exposed to fresh smoke certain flavour compounds are absorbed by the skin of the grapes and are sequestered there – very little actually gets into the flesh of the berries.

There’s very little movement of smoke compounds from leaves into grapes, and they don’t enter the grapes through the soil or roots either. Any smoke effects are present for a single season only: if a vineyard is affected by smoke one vintage, there is no carry over to the following vintage.

Timing is key

One of the biggest risk factors during a smoke event is the growth stage of the grapes at the time of smoke exposure.

While there is a low-to-medium risk right up to the point of veraison (when grapes start to ripen, softening and changing colour) the greatest risk is during berry ripening – just before the grapes are picked.

In Australia, our harvest dates differ vastly from region to region, so the vulnerable period for grapes is different for each region.  

Proximity and ‘freshness’

When there is smoke present, we know that the risk is greatest the closer the vineyard is to the fire and when the smoke is ‘fresh’.

Even though smoke haze looks and smells bad, due to the way that smoke moves and disperses, research has identified that the greatest risk is from thicker, new smoke rather than from smoke that lingers after a fire event or has spread over a great distance. However, there are always exceptions and extended exposure to smoke is a concern.

What can growers and winemakers do?

Understanding the effects of smoke in wine is a complex science. However, laboratory tests are available to quantify some of the key compounds that create ‘smoky’ flavours so that grapegrowers and winemakers know if there is a risk that smoke will affect wine made from the grapes.

It is recommended that, at the same time that the grapes are tested, winemakers also carry out a micro-ferment and do a sensory evaluation before harvesting the grapes and committing to the winemaking process. The fermentation process breaks down some of the complex smoke compounds in the grape skins and converts them into the smoky flavour compounds – the substances we smell and taste.

Growers and winemakers can then make an informed decision about whether to pick the grapes and make wine.

This knowledge is really useful because, while some may relish smokiness in Ardbeg, Laphroaig and Lagavulin whiskies – consumers don’t always enjoy them in wine. Research has shown that we’re all different when it comes to noticing ‘smoke flavours’ in wine; this is a combination of our DNA-determined taste sensors and possibly differences in the microflora that live in our mouths.

Sensory testing at the Australian Wine Research Institute (AWRI) has shown significant differences among individuals. Up to 20 per cent of people cannot taste smoke flavours in wines that others find unpalatable.

Smoke characteristics also change over time in the bottle. The rule of thumb is that the longer the wine has been in the bottle, the more likely it is to show the smoky characters. However, style of wine, grape variety and how the wine is stored are important factors, and it may be more that the wines are losing complexity as they age, so smoky flavours come more to the fore.

What is happening in 2020?

Wine Australia, the AWRI, national, state and regional wine organisations are working together to ensure that growers in areas close to fires that have been exposed to smoke are able to get their grapes tested and a micro-ferment evaluated before picking, so they can decide whether or not to harvest them to make wine. This ensures that wine quality is protected.

Without testing, it is hard to predict the effect of smoke as the impact varies so enormously as we’ve discussed in this article. Many growers and winemakers will be testing grapes and carrying out micro-ferments as a precaution and will be making vintage decisions based on the results.

New research is also being carried out to gain increased understanding of the effects of smoke exposure during earlier stages of berry development (pre-veraison).

The Australian wine community values its integrity, which is why we’re honest in telling it as it is. It is still too early to know the impact of smoke this year but, while there may be fewer vintage 2020 wines from a handful of regions, consumers can rest assured that the wines produced will reflect the quality and regionality that they love in Australian wines. 


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