Smoke Signals

What does the latest research, testing and winemaker insights tell us about smoke taint?

By Mark O’Callaghan

Managing Director, Wine Network Consulting, Healesville, Victoria. Email: mocallaghan@winenet.com.au

With around 4% of this year’s national grape crop estimated to have been lost due to smoke taint and fire, Mark O’Callaghan reviews the latest research into the effect of smoke on grapes and wine, the options for managing those effects and talks with two Australian producers about their experiences.

If the 2020 vintage in Australia is remembered for anything, it will be drought, fire, destruction and smoke taint. As unfair as that might be to unaffected regions or vineyards, the saturation media coverage of human and animal suffering, smoke haze in capital cities and environmental carnage made it tough for any good news stories to cut through. During peak coverage of the fires, one could be forgiven for thinking the entire continent was ablaze – certainly friends of mine from overseas were under that impression.

Despite some sage reminders to the wine world that all was not lost and the end was not nigh, the fact is that too many vineyards still had to grapple with smoke taint; some for the first time, some not, some during the heat (no pun intended) of the crisis and others for many months or years to come. With the spectrum of damage ranging from vineyards burnt to the ground to those with marginal taint levels, it is impossible to generalise about the best way forward.

This article recaps the recent R&D and testing progress, considers (subjectively) the management options and discusses the 2020 experience with industry practitioners with sharp insights. Personally, I have seen smoke taint in China and India which I think is from air pollution but we shall stick to conventional sources like bushfires and fuel reduction burns.

There are now many more indicator compounds than just guaiacol and 4-methyl-guiacol in both free and bound forms that can be markers for taint from smoke

WHILE YOU WERE SLEEPING

Alas, smoke taint is nothing new and has been problematic around the world over recent years. However, the extent of viticultural damage in Australia in 2020 was at a whole new level entirely.

Before 2020, smoke damage tended to be more localised or limited to a smaller number of regions in any given season, such as Canberra and North­Eastern Victoria (2003), Eastern Victoria (2007), the Black Saturday fires (2009), parts of Western Australia (2016) or parts of Tasmania (2016 and 2019). It hasn’t necessarily been front-of­mind for the broader industry, so many people were unaware of the research work and testing improvements of the last 10 years or so.

Without doubt, the single most important of these is the measurement of many more indicator compounds than just guiacol and 4-methyl-guiacol in both free and bound forms. This is a total game changer and paints a much more complete picture of the risk than the methods of just a few years ago. Back then, winemakers would often test fruit, proceed with harvest based on low results only to find the wines tainted. Even when we all learned about the glycosidic bound forms of taint compounds and started micro ferments in buckets or coffee plungers, we still grappled with the uncertainty from having only two compunds to measure, tasting awfully green trial wines and the insidious way that taint became much worse over time.

Tests for indicator compounds are only useful if they are timely – tricky during widespread damage – and wineries can interpret them – tricky without the experience. Unsurprisingly, turnaround times were under pressure this season, as Dr Mark Krstic, managing director of the Australian Wine Research Institute, highlighted: “Typically, we would receive 400-600 samples per season but by mid-March, we had received around 3400. At the start of the season numbers were manageable but in late February we received 1700 alone in only a two week period”.

Interpretation can be another minefield entirely. Armed with a laboratory report showing total bound glycosides of, say, lS0µg/kg, what should one do? Is it for red, white, sparkling or fortified wine? Will it be hand picked? Is it from your vineyard or from a grower? What does the contract say?

For a take on the New South Wales experience, I spoke to Liz Silkman, chief winemaker at First Creek in the Hunter Valley, which makes wines for clients across the state.

“At the start of the season, people were talking about less than 50 (total bound glycosides) and you’re OK. Then it went to, ‘Oh, 80 is OK’, then to 120 but this talk wasn’t linked to any particular variety or wine style. It was just scuttlebutt across the region or talk at the pub! None of this was coming from any reliable source and I got the sense that people wanted it to be OK. In all honesty, if you’re greater than 80, I think you’re screwed,”Silkman said.

Some people suggest that the cut-off should be lower than that, even for sparkling wines, but in the end, wineries need to make their own assessment of risk – the laboratories should only provide the numbers. I also discussed this year’s smoke taint experiences with another senior winemaker who preferred to speak off the record – a reminder of the sensitivity of this issue – and was particularly focussed on the timing aspect:

“This year the smoke was gone by the end of January, so at least we had time to test and plan. We tested extensively at veraison but I still think you can get useful results earlier. The industry desperately needs rapid turnaround – 24 hours would be amazing! This is just so important when you get smoke just before harvest. If we’d had that this year we would have been in even more trouble.”

The other changes in understanding include the mode of ingress of taint compounds (more through berry skin than vine leaves), the rate of binding to sugars (a rapid detoxifying technique of the vine) plus the relative sensitivity of different varieties (jury still out) and growth stages (later seems to be worse). Some of this work might be useful for techniques in the future, such as spray barriers on berries, but at present these make little operational difference in the field.

Work has also been done on the effect of different fuel types, bushfires versus controlled burns and stubble burn-offs and at this stage it seems these make no noticeable difference. The work to date on measuring smoke intensity, composition and duration in the atmosphere has been interesting too but is not yet a practical adjunct to grape testing.

We are yet to see the new methods of testing reflected in the text of grape supply contracts but they will make interesting reading for 2021.

In my personal view, a great deal of thanks should also go to the AWRI for its measurement of background levels of smoke compounds in recent years. This improved understanding to enable benchmarking against these compounds has helped a great deal with context and interpretation and shouldn’t be underestimated. The AWRI was also working on this while practically nobody was paying attention.

WHO CARES?

The media does, the trade does and consumers do. Governments produce media releases which say they do.

The AWRI has recently completed some insightful consumer testing on responses to smoke taint which torpedoes the notion that the wine community could be over-sensitive and consumers might be ambivalent.

The AWRI obtained consumer liking responses under blind conditions for a strongly smoke-affected Pi not Nair wine from the 2019 Tasmanian fires, and blended it with different proportions of a clean, unaffected wine of the same variety and style. The results clearly showed that the smoke-tainted wine had a liking score that was very much lower than that of the clean, unaffected wine, with the score so low that it would not be considered suitable for release on the market according to usual consumer testing practices. Only a small proportion of consumers did not respond negatively to the smoke flavour. In fact, the largest consumer cluster identified showed a linear decrease in liking with an increased proportion of the smoke-affected wine, with even 6% of smoke tainted wine in the blend reducing the liking score.

There are many anecdotes to support these results but a good one comes from a winemaker friend of mine who began a new appointment in 2009. The winemaker noticed a 2007 red wine sitting almost untouched in China, so requested samples. The wine was clearly smoke tainted but this had gone unnoticed by the winemaker’s predecessor. Even in a relatively undeveloped wine market at the time, the push-back was emphatic and although they couldn’t explain why they didn’t like it, distributors and consumers wouldn’t touch it.

First Creek winemaker Liz Silkman

A refresher on the nature of sensory thresholds is also timely and it is important to remember that these are population average thresholds. This means that 50% of a population has a sensory threshold below the published level which is critical in considering sensory assessments and market reactions. Variation within a group of winemakers can also vary considerably, so sensory assessments should certainly be done by more than just one person. The AWRI recommendations for sensory panels are worth reading.

When it comes to media, the global interest and saturation coverage in 2020 was perfectly understandable and their predilection for drama is just the nature of the beast. It should come as no surprise then that bad news travelled fast and, at times, it seemed the entire vintage was written off.

That does not mean we cannot learn from it and, as a community, improve the messaging and make it more constructive. It is certainly something that had Liz Silkman a little frustrated at times: “Frankly, there were a few people acting like Chicken Little at the start of it all, running around saying the sky was falling, vintage was ruined, etc. I’m just not sure the average reader takes in that bit buried in the eighth paragraph about there still being some lovely wines, have confidence in the wines from the houses you trust. I’m fully supportive of individual wineries putting out their own releases like the one from Clonakilla but I do think the Hunter message was really poor.”

One of the more noteworthy contributions to the public discussion came – perhaps unsurprisingly – from Brian Croser (‘Be-calmed – Brian Croser iterates his thoughts on the 2020 Australian vintage’, wbmonline.com.au, 11 February, 2020) In typically thoughtful style, it was quite telling that he felt the need to “reintroduce some civility and logic into the discourse” while he made his points about staying positive and the fact that the fundamentals of the season had actually been very good. Sometimes it can be best to think before posting, shouting at each other, or maybe just have a Bex and a good lie down.

IN THE VINEYARD

If the threat of smoke taint is here to stay – and sadly, I think it is – I look forward to the day when we can provide growers with a list of practices or products that can mitigate it at the source, but I won’t be holding my breath. In fact, smoke taint risk is now one of the items on our checklist for vineyard site suitability or due diligence assessments at Wine Network.

The heartbreaking nature of smoke taint was summed up by my off-the­record interviewee: “Compared to most other adverse things that can happen, there is really nothing you can do. You are restricted to a finite pool of things in the winery and even these can be temporary in their effect. Whether it’s botrytis, mildews or hail, kangaroos and deer, there is always something you can do. With smoke you’re at the mercy of things beyond your control.”

If that is an exaggeration, it is only minor. The techniques that can help are certainly no panacea and often expensive and totally impractical. It is well known that hand picking is beneficial but this is totally unaffordable for most wine made in Australia and only getting more expensive each season. Re-purposing fruit is possible but redirecting Pi not Noir from red wine to sparkling, for example, only works in a handful of cases. Work is under way to test whether the new generation of machine harvesters will pick up less taint than the old versions (through reduced green tissue) but conclusive results will take time.

Contract and commercial arrangements between growers and wineries also explored new territory during 2020 and it will be interesting to see how this evolves around the world over the next few years. Since 2007, many grape supply agreements have included options for outright rejection and/or price downgrades if any smoke taint is measurable whatsoever. As harsh as that may seem, it made commercial sense at the time and these clauses should evolve with the improved testing.

Some new arrangements for fruit supply include guaranteed minimum pricing to cover harvesting and transport costs – ensuring growers spent no more cash – with other payments based on the final allocation of the wine. In other cases, growers have been given the option of having the wine made under contract and selling the bulk wine to the original buyer if it is fit for purpose – an approach complicated by WET rebate considerations.

Perhaps the most surprising, generous and astute approach to the grower relationship from 2020 was the winery that did not pick but made a cash gift to its growers to support them. The growers were then free to sell their fruit to other customers who could still make use of it, making this one of the most proactive strategies for sharing agricultural risk I have ever seen.

IN THE WINERY

In cellars across Australia – or at least on the east coast – there has been a great deal of experimentation with techniques to minimise the effect of smoke taint. Much of it is well considered but there are still no magic bullets. There are, however, new