This is an updated and significantly longer version of an article which originally appeared in Issue 2/2017 of Meininger’s Wine Business International with additional input from Joseph di Blasi, and Geoff Cowey. And yes, another outing for that photo….
Imagine a yoghurt manufacturer decides one day that using predictable, laboratory cultured lactic bacteria to create their product compromises its integrity. They decide to market a completely “natural” yoghurt where the milk is left to ferment at will, without any additions, interventions or preservatives.
The product becomes wildly variable, sometimes delicious, sometimes outright mouldy, with strange and rather unpleasant odours. The yoghurt manufacturer’s line would probably be dropped from retail outlets after customer complaints. They’d go out of business shortly after.
Implausible? Maybe, but it almost parables the developing niche of natural wine, and specifically the exponential growth in wineries who work without sulphur dioxide (SO2) additions. The resulting wines span the entire gamut from sensational and pure, to dirty and borderline drinkable.
It’s somewhat ironic that the use (or not) of sulphur has become such a philosophical minefield. There is no evidence that the minute levels in wine cause any health issues, excepting the sub-1% of wine drinkers who have a true allergy or asthma – it’s worth remembering that products such as dried fruit, soft drinks and processed or frozen foods commonly contain far higher amounts than wine. Yet for natural wine hardliners SO2 seems to have become synonymous with the devil, symbolising the fight between good and evil, between “natural” and “industrial”. Sulphites must be shunned, as vigorously and devoutly as powdered tannins, mega-purple or yeast enzymes.
Arguably this puritanical stance has gone too far. Reducing SO2 inputs to zero is a seriously risky business. Without pristine grapes and a squeaky clean cellar, there’s more than a chance that volatile acidity, brettanomyces or oxidation will show up like uninvited guests at a party.
Most producers and wine professionals recognise and understand these faults. They’re even tolerated to some degree, depending on the perception threshold or personal taste of the drinker. Plus, there’s a solid body of wine science available to help mitigate the problems.
This unmistakable taint seems to be on the increase, scurrying ever more rampantly around the cellars of a thousand radical vignerons.
The mucky aftertaste generally known as “mousiness” is a much more slippery pest. Poorly understood in the industry, virtually opaque to consumers, it has neither been conclusively researched nor openly acknowledged by some producers. Yet this unmistakable taint – once recognised, never forgotten – seems to be on the increase, scurrying ever more rampantly around the cellars of a thousand radical vignerons.
My sensory sampling at Rawfair Berlin 2016 found 20 tainted wines out of 100 tasted. It put a serious dampener on my enjoyment of the day. The problem was no doubt exacerbated by warm conditions, and bottles that in some cases had been open for a few hours – but if these wines are so fragile that they don’t remain at their peak for more than an hour or two after opening, one must seriously question the quality of the raw materials and/or the winemaking. Are these producers almost wilfully putting faulty wine up for sale, or are they just in denial about the scale of the problem?
Definitions
Mousiness is not synonymous with Brettanomyces, although the two often cohabit, and the latter can stimulate the former.
Mousiness is defined as a taint caused by lactic bacteria or possibly by Dekkera (AKA Brettanomyces) – the jury is still out on the latter. The compounds have long been isolated (since at least 1977, see Tucknott, O. G. Mousiness: A taint in fermented beverages. Ph.D. Thesis, University of Bristol, Bristol, England, 1977), to one or more of the following:
- 2-acetyl-3,4,5,6-tetrahydropyridine
- 2-acetyl-1,4,5,6-tetrahydropyridine
- 2-ethyltetrahydropyridine
- 2-acetyl-1-pyrrolene
The taint manifests itself in a unique and troublesome fashion – the compounds are not volatile at the normal pH level of wines, and thus are virtually undetectable by smell. When infected wine mixes with the taster’s saliva, the pH is raised to a level where the 2-acetylpyridines are perceived retronasally – an aftertaste which is technically an aroma. This nasty surprise can sometimes take as long as 30 seconds to develop in the mouth, giving an entirely new meaning to wines with a “long finish”.
Natural wine advocate Alice Feiring offers the grimly accurate descriptions “puppy breath” or “dog halitosis”. Caged mouse or cheese biscuit are barely less colourful similes. The Oxford Companion to Wine is declarative on the subject: “Once detected, the taint renders the wine undrinkable and worsens in the glass, but as many as 30% of winemakers are unable to detect it.”
That last statistic ought to raise eyebrows on its own, but it’s not only winemakers who vary in their ability to taste mousiness. Anecdotal evidence suggests there’s a very wide range of tolerance amongst wine professionals and consumers, from blissful ignorance to super sensitivity. An individual’s ability to detect mousy taint might even hinge on the characteristics of their saliva – ergo possibly a genetic condition.
The confusion in the industry isn’t surprising, given the complexity of the problem and its sensory analysis. Some commentators insist that “mousiness” is a subjective tasting term. It’s not – the word has been used scientifically as a fault descriptor for decades – for example, Reinhard Eder’s classic “Weinfehler” textbook from 2003 uses the German translation “Mäuseln”. The French equivalent is “La goût de souris”, a poetic sounding phrase describing a problem which is anything but.
The research
Research into mousiness exists, notably from the Australian Wine Research Institute and the Klosterneuburg Wine School, but still leaves many unanswered questions. Geoff Cowey, senior oenologist at the Australian Wine Research Institute, confirmed to my frustration just how many loose ends remain:
“The AWRI microbiology team is not doing any active research in this space currently. There have been some project proposals for funding in Australia for new research but as yet none of these have been successful.
Dr Alison Soden (AWRI) and Dr Paul Grbin (Adelaide University) did some research about 10 years ago (2006). There has been some research investigating if Brettanomyces contributes toward mousiness but no clear correlations have been found.
Wine researchers are also still unsure of which of the N heterocyclic compounds is the most important contributor toward mousy flavour, or if it is actually a combination of compounds. Kunzler and Nikfardjam (2013) detail some of this in proposing a chemical pathway for mousy formation in wine.
A lot of research has been difficult because there were none of the mousy taint compounds commercially available to do research on – thus why there isn’t great sensory threshold data or common analytical techniques to measure wines for mousiness. Kunzler [and Nikfardjam] have developed a method and measured some wines for mousy characters. Our team is also working on a similar method to allow quantification of mousy compounds. It will be interesting to see which of the many proposed mousy compounds are actually causing the mousy characters, and if in fact it is the same compounds each time.”
So what do we know for sure? Wine scientist Geoff Taylor of Campden BRI explains that low SO2 levels, high pH (usually related to low acidity), poor hygiene and the presence of oxygen provide the best conditions for mousy taint to develop – given that the right lactic bacteria are already floating around in the winery. My own anecdotal evidence from tasting some 2,000 wines a year suggest that the problem occurs almost exclusively in wines made without any SO2 additions.
A risky business
Making wine without using any SO2 is comparable to a trapeze artist refusing to use a safety net. The risk of catastrophe is ever present. There’s a particular challenge when winemakers who spurn the use of SO2 become ardent, or quasi-religious about the topic.
Mas Zenitude is a small estate in Languedoc, farmed on biodynamic principles. It’s run by Swede Erik Gabrielson and American Frances Garcia. In 2013 the estate had a serious problem with mousy taint, which developed in the barrels holding their white wine “Solstice”. The wine was bottled and sold, but by Gabrielson and Garcia’s own admission was far from representative of their desired standards.
Geoff Taylor (Campden BRI) confirms that free SO2 levels above 10mg/L are enough to inhibit mousiness. I asked Gabrielson why he wouldn’t just add a tiny amount of SO2 to prevent the taint taking hold – The reply was simply “principle”. It’s as if Gabrielson would rather accept a compromised end product than give way on his no sulphur stance. Is this taking dogma too far? In my opinion, yes it is.
Gabrielson and Garcia successfully prevented the issue occurring in future vintages (which produced some delicious wines), by removing the infected barrels and moving to concrete eggs, but to date they remain dogmatic on their refusal to use SO2.
Not all producers in the “natural wine” space are this dogged. The Slovenian family Mlečnik are highly regarded for their skin contact white wines, made in an ultra-traditional style. But father and son Valter and Klemen are unequivocal on the topic of mousiness: “In all cases it is absolutely unacceptable to bottle or sell a wine like this.” Their solution is to use SO2 sparingly, having had issues with the taint developing in their wines in the past.
Fad or fashion?
In some cases producers appear to be swept along on the tide of fashion. Michael & Erich Andert run a tiny 4.5 hectare estate in the Neusiedlersee area of Austria’s Burgenland. Biodynamic principles are ingrained into the whole operation, with fruit, vegetables and animal husbandry all coexisting amongst the vineyards. Over the last 18 months Andert attracted attention from international press and importers, mutating from a hyper-local operation to an increasingly renowned name in the natural wine bars of London, Paris and New York.
Joseph di Blasi, a well known distributor of natural wines, asked the brothers to bottle some of their Muscat 2013 without added SO2, which they did. The experiment was successful, so they expanded it to include more wines in the range in the following year – but some of these resulting wines have mousy taint. Only one of the brothers is able to detect it when tasting, and they are now in discussion about the best way forward. Michael Andert is stoical on the issue: “We’re lucky to have had all this success so quickly, we’re now exporting to several different countries. But we need time to figure out whether to abandon the use of sulphur or not – we don’t want to make a hasty decision.”
Blasi is keen to point out that he is no lover of mousiness, but that when he tastes wines that seem to be strong and healthy, he is often tempted to suggest that the producer bottles them without any additions. This is his account of the Andert affair:
“It was early 2014 when I first met Michael Andert at his place. We eventually arrived at his only stainless steel tank where his 2013 Muskat was sitting. I remembered being blown away by this wine. The purity, clarity, minerality, firm acidity, all in place. Most importantly, ripe grapes. I recall asking what the next steps were for this wine. His reply was that he would usually do a light sulfuring and light filtration before bottling. He looked at me curiously as if he knew what my next comment would be.
So I took the bait, I said why would you add sulfur when the grapes and this wine are so healthy? Why would you filter it? Have you ever produced a wine without added SO2? So I told him I would help him take this risk if he would keep the wine as is.
The 2013 Muskat turned out to be a beautiful wine which according to Andert, got him on the road to being discovered. Many of his clients were calling and asking about this wine. It was a success and had ZERO mousiness and ZERO additives – thank goodness as i am not a fan of either.”
Obsession
At the other extreme, Belgian maverick Frank Cornelissen has been vinifying on Mount Etna without SO2 for 16 years. His wines can be idiosyncratic and frequently divide opinion, but Cornelissen generally avoids problems with mousiness. This doesn’t relate to romantic notions that Etna’s eruptions might maintain a high level of natural sulphur, but is due to an obsession with cleanliness. “You have to be a maniac when it comes to hygiene,” he admits. “I’ll invest in any tool, any substance, anything that keeps my winery clean so long as it doesn’t spoil the wine. The sky’s the limit.” Cornelissen uses ozone, compressed air and anti-bacterial sprays in his fight against stray infections, whilst keeping his storage and packing areas hermetically sealed under ionised air. When I was tasting in his cellar earlier this year, he wiped down the table where we placed our tasting glasses twice in the space of an hour tasting.
Wouldn’t it be easier to use a sprinkle of SO2 instead of this barrage of expensive high-tech solutions? Maybe, but Cornelissen’s mission is to “make wine with nothing added”, and from that he will not be swayed. Only a hypothetical scenario posed in our interview showed a pragmatic chink in his idealist’s armour: Suppose that an entire vintage risked infection with mousy taint. Would he then intervene with sulphur? “Throwing away wine is a really radical decision. You worked your ass off for a whole year for that. If I risked an entire vintage, yes, I’d add sulphur, or buy in grapes, or do something to stop going bankrupt.”
Cornelissen is now an elite member of that very small club of winemakers who have close to 20 vintages under their belts working without sulphur, joining “noSO” stalwarts such as Radikon and Mas Coutelou. Natural wine’s grand daddies Jules Chauvet and Jacques Néauport, the first in the modern age to make wine with no sulphur inputs, put in decades of research and experimentation before their ideas were later popularised by the “gang of five” (Marcel Lapierre et al).
The risk with less experienced producers who’ve since adopted this most challenging winemaking method is that the same mistakes are repeated endlessly, perhaps even implying that mousy wine is excusable on idealogical grounds. The fact that some don’t even recognise the flaw in their own tasting is the coup de grace.
The Mlečniks have no truck with this situation: “All the unwanted flaws in wine are a reflection of our misunderstanding of natural processes – or even worse, deliberate and conscious disregard, which ultimately leads to anarchy.”
Assuming that anarchy isn’t a desirable endgame, the natural wine world ought to call out mousiness as the growing scourge it is. Winemakers need to be transparent about the problem – ideals and dogmas, however worthy, are not enough to rid their cellars of its pestilence.
Well articulated and I have an interesting perspective to add. The issue is not about sulfur being bad for you; we put far worse things in are body. For me, mousiness is not lack of sulfur, but lack of technique and know how. Sulfur itself is not toxic, but it is far from pleasant. Anyone that has worked in a winery knows that crippling smell that can take the air out of your gut, make you cough and drop to your knees. When added to other elements, sulfur becomes toxic and corrosive; therefore it is a controlled substance. Imagine taking a small shot of straight sulfur; it probably would not kill you, but you would be ruined for days. Think sulfur is not bad? You might never know because it is in a lot of foods and our water supply (tap or bottled). If you could find a way to… Read more »
Jeffrey, thanks for this hugely detailed and interesting comment. I think it’s nearly as long as the article! You are quite correct to point out that Sulphur is unpleasant stuff, but we should not forget that it is typically used in wine at levels of around 50-100 parts per million (PPM). That is a minute, almost homeopathic concentration. In terms of denial, I had a lot of issues getting winemakers to talk about it. Many brush it off as if it does not affect them. Sometimes these are the producers who one realises cannot taste it. I know the Burgundy producer you mean, and I had one of those wines with the wrong vintage on the cork. It caused a colleague of mine who is the distributor in NL some head scratching. Now we know why, so thank you! I’m not a fan of his wines in particularly, but they… Read more »
Indeed! I love the topic. I agree that 50-100 ppm is minuscule, but I’ve done a few tastings of the same wines with less added and it was a huge difference. The one with no added sulfur was not moussy, just more fresh. I do not like mouse taint and would rather have added sulfur, but I’ve tasted too many producers who do not use it and the wines never have mouse. It is strange. It sucks that about the lack of discussion of mouse taint. I’ve had exposure, but could understand how people would not acknowledge it or even detect it! I forgot to mention this before, but I think all wines, if left open indefinitely (in bottle under cork), eventually leads to mouse taint. I cannot say that this is the absolute truth, but I’ve had bottles open for up to 2 weeks before the taint reveled itself.… Read more »
Well, Radikon’s wines are often ever so slightly mousy for the first 6-12 months or so after bottling. I try never to drink them young for that reason. Never had any issues with mature ones. And I reckon I’ve enjoyed 10 – 12 different vintages or more. Again anecdotally, 10-20 ppm is enough to completely banish any mouse issues. It’s so little, frustrates me when this is all it takes between having something I can’t enjoy and something that is magical. I remember tasting a La Biancara wine at Raw one year. It was the most beautiful, magical, enlivening thing. And then the mousiness kicked in on the finish. It was really like the princess turning into the frog. Just horrific. (not that I have anything against frogs you understand, but I’d rather have a princess if I can choose!) For me the drinkability of a wine is a complex… Read more »
I am very interested in learning more about the genetics of tasting. This has interested me since my husband confessed to me that he thinks cilantro is disgusting. He always said it tasted like soap, and I never believed him until I read an NY Time article on the subject and it turns out that yes, indeed, to him, it does taste like soap. He has the gene that makes him taste that herb in that way. The reason this subject interests me in wine is because I am now moving forward with wine education, Diploma, and was recently at a tasting at the school. We were learning the more in depth approach they use which is supposed to be systematic, so that all tasters are calibrated the same (within reason). But is that really possible? Each human body is so different. I know I don’t taste salt the same… Read more »
I am very interested in learning more about the genetics of tasting. This has interested me since my husband confessed to me that he thinks cilantro is disgusting. He always said it tasted like soap, and I never believed him until I read an NY Time article on the subject and it turns out that yes, indeed, to him, it does taste like soap. He has the gene that makes him taste that herb in that way. The reason this subject interests me in wine is because I am now moving forward with wine education, Diploma, and was recently at a tasting at the school. We were learning the more in depth approach they use which is supposed to be systematic, so that all tasters are calibrated the same (within reason). But is that really possible? Each human body is so different. I know I don’t taste salt the same… Read more »
Definitely a very interesting topic this. Having been through the WSET process myself, I did find it useful because it gave me a framework. Sure, everyone tastes differently but somehow we have to agree on a common language to be able to communicate. That ultimately is what WSET try to achieve I think. I believe cultural loading can be quite significant. Americans have a much sweeter tooth than most Europeans, because they’ve allowed their entire food chain to be polluted with cheap sweetners. Americans are lucky if they get raw sugar in their food. It’s much more likely to be HCFS or glucose fructose syrup. It scares me that most bread you buy in the US has added sweeteners. Kiwis and maybe Ozzies are more susceptible to mercaptans. Apparently the Portuguese are much more sensitive to brett taint than the French. These are huge generalisations but I think they are… Read more »
Man, you nailed it! Thank you for answering on many of my questions!
Pleasure!
Thank you, it answers a long standing family query regarding why some family members can happily drink wine that others find have a hint of bottom-of-the- bird-cage which requires a cleansing lager to remove.
Glad I cleared that up!
Regarding:
“I’ll invest in any tool, any substance, anything that keeps my winery clean so long as it doesn’t spoil the wine. The sky’s the limit.” Cornelissen uses ozone, compressed air and anti-bacterial sprays in his fight against stray infections, whilst keeping his storage and packing areas hermetically sealed under ionised air. When I was tasting in his cellar earlier this year, he wiped down the table where we placed our tasting glasses twice in the space of an hour tasting.”
This is “natural”?
Frank’s take on this has always been “I don’t make natural wine – I just make wine with nothing added”. His approach is certainly quite extreme in many ways, I grant you that. But the wine itself is very “natural”, in that it contains nothing but fermented grape juice, is from hand harvested, organically grown fruit, isn’t filtered or fined etc etc etc.
Everybody’s definition of what “natural” means is different.
Yes unfortunately natural means nothing and like philosophy, everyone has a different view. Natural wine gets attacked because wine does not exist naturally, but I think it’s a start in the right direction. Natural is like the word “craft” which is now being used by breweries in the USA. 99% of brewers force carbonate their beer and there is nothing craft about that. That’s Prosecco. A lot of craft brewers also add tetra hop to their beer. To me craft, natural, artisan and boutique are usually the kiss of death. These terms are abused. For me, I accept added sulfur (it is a natural element) in natural wines, because it is done to preserve/prevent. It is not added to change body, texture (although it does), tannin, acid or flavor. Natural is now being linked to terroir, but there are many adjustments that I do not believe can be used in… Read more »
re: added water. Have you read Alice Feiring’s “Naked wine”?
re: Prosecco, this is why I love the col fondo movement. There are great producers doing great things in that region.
[…] Are natural winemakers in denial about mousiness? Simon Woolf continues the discussion. […]
[…] tannins, the wine gains structure with air. My bottle unfortunately started developing the dreaded mousiness after a few hours. Simon has reported that some Japanese drinkers like this taste. Being Japanese, […]
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Hi Simon,
I’m a natural winemaker in Languedoc (www.domainedesamiel.com) and share 100% of your comments and concerns. Mousiness is our most challenging issue after 5 years of natural winemaking. I’m ready to share all my info / background with you if you want. And you’re welcome to come and taste! Our idea is to make natural wines that are clean and healthy, with no dogma but true conviction that it is possible (thought not always successful). Hope to talk soon!
Hi Aymeric,
Great to hear from a winemaker who acknowledges this issue. I was briefly in Languedoc last autumn, not sure when I’ll make it there next but will certainly keep your details ready when I do. Do you attend any of the natural wine fairs in Europe?
[…] Are natural winemakers in denial about mousiness? Simon Woolf on the risks of Natural Wine. […]
Hi Simon, great article! Like you i am very susceptible to mousiness and your article explained a lot to me. Unfortunatly I taste often samples of wines that would be great, if not for the mousiness. Do you (or other people here) think it fades away with bottle aging? I can’t really remember ever having tasted a wine with mousiness that aged in the bottle for more than two years?
Hi Karel, Difficult to say. I’ve definitely had wines that seem to get more stable with age – for example, most Radikon falls into this category. It does seem to be true that a large proportion of wines that are mousy when young can sort themselves out after a year or two in the bottle. The issue is that I don’t believe there is any guarantee about this – so it’s a dangerous pronouncement for a winemaker (or anyone else) to make. And I’ve also had plenty of wines with 3-5 years of bottle age that have been disgusting and undrinkable due to mouse taint. What I hate most is those bottles where you realise you’ve opened a ticking timebomb – and you have maybe an hour or so to enjoy the wine before it turns. I truly don’t believe a top winemaker would want to put something so unstable… Read more »
Thank you, Simon. I agree. As a wine importer you can’t really order a tainted wine to hide the bottles for two years, hoping an avoidable defect goes away.
Also you hit the spot by using the word ‘denial’. When I mention mousiness to producers they close up and change topic. I can’t get my head around why you would neglect this problem and make tainted wines again the next year. It must be hard for them too to sell these wines, right?
Yes and no – so many people can’t taste it, or don’t recognise it as a fault. Which is frustrating, because this isn’t the taste of terroir. It’s the taste of unwanted bacterias!