Many winemakers consider S02 essential for consistency and quality in wine, but there have been contentious moves to abandon its use. Are sulfites in wine harmful? And what are the effects on aroma and flavour of cutting back in the cellar? Simon Woolf takes a balanced view...

I have two bottles here in front of me. Both are Sauvignon Blanc 2012s made by Sepp Muster, a biodynamic grower in Austria’s southern Styria region, both sourced from his Opok vineyard. They taste very different: the first is extraordinarily alive, with concentrated citrus fruit and beguiling complexity; the second feels more muted, somehow more lemonade than lemon.

The difference between the two is a mere 10mg of sulfur dioxide (SO2) – or ‘sulphur dioxide’ – added after racking the second bottling. Muster isn’t just trying to prove a point – he’s one of a small but growing niche of winemakers seeking to reduce the intervention and additives used in wine production to close to zero. The spurning of SO2, typically used to prevent oxidation and keep unwanted bacteria at bay, is the final frontier in this quest. It’s regarded as lunacy by most conventional producers, and worshipped like the holy grail in natural wine circles. Why is opinion so polarised around this topic?

Are sulfites in wine harmful?

SO2 definitely has a bad rap when it comes to popular opinion. That could have a lot to do with the terse couplet ‘contains sulfites’, legally required to grace almost all bottles of wine sold in the US since 1988, and within the EU since 2005. Only those with less than 10 parts per million (PPM) are exempted, and here’s the rub – the fermentation process can produce more than that naturally, without any added SO2, meaning that even many ‘no added sulfite’ wines must display the offending words on the label.

Does this mean sulfites in wine are harmful? Probably not, at least not in the minuscule amounts found in modern wines – typically 20-200 PPM. Compare that to a handful of dried fruit, which will have been dosed with anywhere from 500-3,000 PPM. While this amount could theoretically cause an adverse reaction in an asthmatic, it’s extremely rare: sulfite intolerance reportedly affects less than 1% of the population. Sulfites are probably not responsible for your hangover either, as Andrew Waterhouse, professor of enology at UC Davis, asserts: ‘There is no medical research data showing that sulfites cause headaches.’

Given the apparent lack of health risks, why do winemakers like Muster insist on reducing their sulfite usage to a bare minimum, or even to zero? Despite its usefulness in slowing oxidation and knocking out harmful bacteria, some believe SO2 also mutes the delicate nuances that express vintage or vineyard character, as Muster proved to me so definitively in our tasting.

sulphur dioxide, Stellar wines

Stellar Winery in Western Cape make ‘no sulfur’ wines

Purity of wine

Fellow southern Styrian winemaker Franz Strohmeier has also moved to zero-added SO2. He explains: ‘When we purchased another vineyard, I found a whole load of old bottles that the previous owners had left in the winery. We tasted them and I loved the complexity, the strangeness of the flavours in these old wines. I feel that when you don’t use sulfites, this character comes through more strongly even in young wines.’

Purity is the ultimate goal for many producers on the no-SO2 path. Alaverdi Monastery, in Georgia’s Kakheti region, simply strives to make its wine ‘good enough for God’. In the eyes of the monks, any additive, SO2 included, would render the wine impure and thus worthless. Belgian Frank Cornelissen, who has made wine on the slopes of Sicily’s Mount Etna since 2000, has the similarly straightforward goal to make ‘wine with nothing added’. His imperative isn’t spiritual, but built on the conviction that fine wine can be a totally additive-free product. Cornelissen believes that the knowledge of how to make wine without sulfites has simply been lost over time: ‘We have to re-learn these skills, which is a slow process.’

Isabelle Legeron MW agrees: ‘Growers are still learning how to make wine with no added sulfur – they only get one go at it every year! Perhaps it’s better if a grower gradually reduces the SO2 each year, rather than immediately trying to make a no-sulfur wine.’

Challenges of no sulfite wine

There are challenges. When sulfite inputs are forsworn, the risk of bacterial or microbial infection is vastly increased. Obsessive hygiene has to take their place – Cornelissen uses ionised air to clean his cellar. A more ‘laissez faire’ attitude is required when it comes to speed of fermentation, and the yeasts that will be involved. Conventionally, SO2 would be used to see off any wild yeasts on the bloom of the grapes, so that the winemaker can inoculate with his or her choice of laboratory yeast.

Adverse effects vary in their seriousness – wines made without SO2 can have slightly wild, ‘funky’ aromas, which prompt the same love/hate reaction as a ripe/stinky cheese. ‘Mousiness’ is another matter – the curse of the ‘no-SO’ winemaker, this characteristic, feral finish is undetectable on the nose, but hangs around on the palate and can easily render a wine undrinkable. Once confused with brettanomyces, it’s now recognised as a completely separate problem.

How and why mousiness develops is still only loosely understood, as wine scientist Geoff Taylor of food and drink research company Campden BRI explains: ‘To the best of my knowledge, very little work has been done matching the taint with the compound.’ He clarifies: ‘The (lactic) bacteria can remain dormant for years and when conditions permit (sufficiently low free SO2, warmth), they will grow. And growth is slow.’ The risk is increased by poor hygiene in the winery or damaged grapes. As Taylor implies, this can cause severe bottle variation – another tricky factor to explain to wine drinkers used to more consistent, industrially made wines.

Producers working in this extreme fashion tend to be small, artisanal, and loosely allied under the ‘natural wine’ banner. There are exceptions – Stellar winery in South Africa’s Western Cape is a large-scale producer that very successfully introduced a no-SO2 range of wines to the UK’s supermarkets in 2008. No-SO winemaking has been around a lot longer – Jules Chauvet and Jacques Néauport, widely hailed as the godfathers of the natural wine movement, started experimenting in Beaujolais in the 1980s.

There’s little doubt that making wine without adding any sulfites is a high-wire act. Producers who succeed tend to be those with considerable experience. The results can be stunning in their clarity and character, but for most winemakers, the unpredictability and risks of spoilage or instability are simply too great. Keep a keen eye on those pushing the boundaries though – their wines might just surprise you.

Writer, columnist and natural wine specialist Simon Woolf won the 2015 Born Digital Award for best editorial/opinion wine writing. has used the spelling ‘sulfur’, but it can also be spelt ‘sulphur’.

  • For more on mousiness, here’s a longer piece I wrote focusing on that subject. Becoming something of an obsession of mine!

  • Late indeed!

    1) I find it pretty easy to guess if the level is either low or no added So2. Wines made in this way tend to have some telltale “wildness” on the nose, most of which I quite like. With no sulphur wines, if I taste mousiness on the finish then I know 99% sure it’s a no sulphur wine. Sad but true.

    2) Good question – I don’t believe any producer attempts to do this, but some are more experienced than others, and bottle/barrel variation will play a huge part with wines made in this way.

  • Late to the discussion but just a couple of points to make from a producer who has always used very low levels of sulphites.

    1) Have you ever tried to guess the total or free sulphite level in a wine tasted blind?

    2) What kind of producer attempts to sell a clearly faulty wine at a high price?

  • Paolo Bassanini

    There are actually many more No Sulphur Added wines. We are manufacturer of a product line, named Epyca, used to totally substitute Sulphites in wines and is made of tannins extracted from grape seeds and wood. With our product the quantity of tannin added is 2 grams per 2000 liters of wine, so no tannic effect, just protection. Moreover, Epyca integrates in standard winemaking processes. Epyca is also registered at Ecocert Oenologie for use in Bio wines. I invite you to check here some winemakers whose no added sulphur wines are made with Epyca: ITALY: Mirabella Franciacorta (, Perego&Perego (, Grosjean (, WAS (, Alepa (, Terra delle Ginestre (, Torre del Pagus (; SWITZERLAND: Cave St. Germain (, Cantina Sangiorgio (, Delea Vini (, Dominique Lousier (; USA: Principe di Tricase Winery (, Harrington Wines (

    At the end the only important factor is to have quality wines that last in time with a taste that people like. Nothing else. Paolo

  • Hi Jason,

    I’m very curious which wine you did the analysis on! In my experience it is certainly true that many winemakers say they do not use sulphites – but when push comes to shove they often admit to adding a bit at bottling.

    However, those that forego it altogether are normally fairly obsessive, and I would be extremely surprised if they were lying. Furthermore the “no added sulphites” claim on the label is something that could presumably be legally challenged if one suspected foul play.

    Also in my experience, most winemakers in the 21st century are a lot more adept – and spareing – in their use of sulphite inputs than previous generations may have been. No-one really wants to use more than they have to.

    As I implied in the article, any producer who is faintly risk-averse or producing on a large scale is going to add sulphur. It makes sense. But that doesn’t negate the benefits of pushing the envelope to aim for excellent wines that require no added sulphur.

    There are plenty of no added SO2 wines out there (including the ones I recommended in the article) which would rate as great wines on any level. They are clean, thrilling, complex and enjoyable. If a small proportion of brave souls want to make these experiments and advance the craft of fine wine making in the process, that can surely only be a good thing for the industy as a whole.

  • Jason Smith

    I am a commercial wine maker, and while I believe very strongly that a wine maker has an obligation to be truthful to their label, I would suggest to everyone that you not be naive and assume all “no sulfite added” wines are really that. I ran a TOTAL (not free) So2 on one of these wines one time and it was almost 100ppm! That’s WAY more sulfites than is produced naturally, so at some point the wine saw a big wack of So2. Other wines that really were no sulfite added were full of aldehydes from oxidized ethanol. I don’t care what anybody says, give me my So2 and I’ll give you a more quality wine. Just USE SO2 PROPERLY in winemaking and it’s very effective. You would be suprised how many wine makers don’t know how to use So2 properly. I think that’s the real problem.

  • Sounds like a storage issue to me. Have you tried visiting wineries and tasting in situ?

  • Andy Whiteman

    Hi Simon,

    Thank you very much for your response. It’s very strange as we used to sell Falernia SB, which was very Loire in style, in our pub/restaurant in the UK along with some Carmeniere, Merlot and Cab Sauv from Chile. Here we get Via Manaent, Trapiche, Tarapaca here but they all are flat.

    I don’t know what the problem is – we brought a few cases from the UK – some 2012 CdR, a few bottles of Burgundy 05, a few bottles of Bordeaux (small chateaux) – they got “stuck in customs” in a container “cooking” and they all survived – I’d written them off. One bottle of Champagne (Lancelot Royer Cramant) also survived.

    So, either my taste buds have gone in the hot weather or something else is going on. We have started using Riedel Magnum glasses again which have improved things a bit. Interestingly the “second” label of Tarapaca has performed best on the SB front.

    Once again – thanks for taking the time to reply.

    Pura Vida,


  • Hi Andy, thank you for reading!

    I’m slightly surprised as I’ve had plenty of attractive white wines from Argentina and Chile (guessing those are the biggest producers you see on your shelves domestically?) – but I have no knowledge of the market there.

    Certainly sounds possible that storage and transportation isn’t done with enough care – is there a strong wine culture in Costa Rica? Normallly that has to develop before people understand the logistics better.

    For example, I encountered numerous tired, oxidised wines in Bosnia last summer – despite there being some very good producers now. The restaurant trade in particular doesn’t seem to take any care with their stock – partly because very few can afford to drink bottled wine there.

  • Thanks for the comment Arnold. You make some bold claims, which I find hard to believe. I’ve seen plenty of US winemakers take strong stances on either side of the natural/conventional sulphur/no sulphur divide, which suggests to me that there is plenty of contention.

    An example comment from a US distributor on twitter yesterday: “for US, even w/refer distribution throughout, sans soufre is a microbial gamble, it’s a long journey from EP” – this suggests to me that there is neither accord nor comfort about the subject, at least not across the whole industry.

    I think your comment about “a lot of the motivation for natural and no added sulphur now is a metter of just doing it” is a bit glib. These aren’t easy decisions for winemakers, who take massive risks by not intervening. For example an English winemaker making wine in Bordeaux contacted me on twitter and summed it up nicely:

    “We’re certified organic but add (little) so2. None is a gamble. Losing a 50hl tank can be ruinous for small producers.”

    Sure, there are idealistic producers in every country who are happy to live with higher risks, lower yields and more specialised markets for their wines. But I’d imagine the vast majority in the US, as elsewhere, do not fall into this category.

    Note, for example Randall Grahm’s comments right at the end of this article: – commercial reality is often very different than ideals or experimentation.

  • Thanks Richard! Yes, it’s a rare thing to see a good discussion in a comments thread – instead of being confined to a very temporary existence on facebook.

    It is quite clear that this topic fascinates/concerns/obsesses a lot of people…

    I’ve been taken to task by various people which also tells me there’s scope for a longer piece sometime – and with the voice of pro-sulphur winemakes as well.

  • Richard Mark James

    I think that’s the longest discussion thread I’ve seen after an article on Decanter’s site, which neatly sums up people’s interest in the topic. So ‘nice one’ Simon for informing and provoking in a balanced and concise way, which can be read and understood by ‘normal’ wine drinkers who have usually only heard gossip and half-truths about the evils of SO2 or not. After all, Decanter is supposed to be a consumer magazine not a science journal. ATB Richard.

  • awaldstein

    Excellent piece Simon.

    Two things I might add.

    First that in the states even in the trade there really is no controversy as there isn’t with natural wine.

    Quality of no intervention organic wines made by small producers with and without so2 added are indeed just getting better. And the market increases along with that.

    Second is that a lot of the motivation for natural in the beginning and no added sulfur now is a matter of just doing it. Doing it because it can be done layered with an overall ethos towards the process.

    Sharing amongst winemakers is happening freely. Quality is getting better and innovation is improving.

    Great time to live down the street from a bunch great natural wine shops.

    Thanks for this.

  • You’re absolutely right, I should have mentioned that. The chap in question did say he’d just started and it was just an experiment. Not as easy as it seems…

  • Sounds like a plan to me. I love that wine!

  • Justin Howard-Sneyd

    It is possible that this nuance wasn’t communicated! Our discussion about SO2 use may have been when we were talking about the whites.
    I bought a bottle of their 2011 Saperavi which was epic! Let’s hope it survives the journey home, and maybe I should bring it to the next DWCC?

  • I’m pretty sure I know which VV producer you mean. I tasted those wines too, in Porto the week before and came to the same conclusion. He wasn’t sure about the no so version either, which suggests to me that he’s started to experiment but probably not pefected this way of working.

    It needs a very skilled hand, and near perfect fruit.

  • Good article, Simon. I’m glad you included the bit about sulphur dioxide levels in some foods and the general lack of evidence of health problems induced by low amounts in wine (and well said, Jiles).

    I was lucky enough to go to two low or no sulphur type wine fairs recently, SimplesmenteVinhoBCN and Vins Nus, both in Barcelona. Tried about 120 wines. At the risk of being annihilated, I found myself a few times putting “add SO2” in my notes. Of course most of the time it’s just a guess, as I have no knowing how the wine would have turned out. But there was one interesting Vinho Verde producer there who had bravely brought “the same” wine with them in both SO2 and no SO2 versions. I preferred the with SO2 version by a long way. The no SO2 wine for me was duller in colour, had a kind of cheesey burnt nose and seemed oxidised. Of course, I might be biased and it would have been nice to do this blind. I would hasten to add that there were also a lot of excellent wines at these fairs and above all, plenty of interesting wines.

    David you make a good point, there’s a huge difference between applying sulphur-containing sprays in the vineyards, adding sulphur-dioxide at the crusher or adding it pre-bottling. Depends what you are trying to do.

  • Thanks Justin. Alice Feiring told me this too. I visited them in 2012 and I have written in my notes from that visit that they only use SO2 in the white wines, as the red wines are used in religious ceremony and have to be free from any additives.

    Any chance you can verify or deny that?

    V best

  • Justin Howard-Sneyd

    Hi Simon,
    Really bizarrely, I am writing this from Georgia, where we just visited the Alaverdi Monastery. They DO use sulphur in their wines. We discussed this at length, and they confirmed it twice.
    There are quite a few qvevri users who eschew it, but not those lovely monks.
    Lovely article – and thanks for giving such a balanced view, but not forgetting to exhort all zealots (on either side) to keep an open mind.
    Very best

  • Andy Whiteman

    Thank you for a really interesting and thought provoking article.

    I live in Costa Rica. Most of the wines here are S American. Many are “over sulphured” with far too much free SO2. Most SB and Chard, are pretty bland, with muted aromas and taste. Wines I used to drink in the UK taste very different here. Maybe the Wineries do this to protect the wines they sell in my region against the climatic extremes. Virtually all the Chilean/Argentinian whites wines smell very strongly of sulphur. On the other hand I bought a Muga Blanco here which was lovely and much the same as in Europe.

    So I’m not sure what the problem is – maybe wineries are dumping rubbish cuvees here or maybe transportation and storage is not up to scratch in a climate where 30C plus is the norm.

    One thing for sure is that I’d love a really nice crisp, fresh bottle of Sancerre, Pouilly Fume or Menetou Salon!

  • That is a very valid question – seperate to the one I posed but equally important.

    As far as I understand it, this ridiculous piece of labelling hypocrisy is gifted to us by the US food industry, which at some point got its knickers in a twist about wine not having to have any mention of its sulphite content.

    That then of course led to a situation where any winery wanting to export to the US was faced with the same requirements, and I believe the EU adopted a consistent regulation rather than cause more problems for export markets.

  • Thank you to Mr. Woolf for a very interesting introduction to a complex subject.

    At one point Mr. Woolf writes “Given the apparent lack of health risks, why do winemakers like Muster insist on reducing their sulfite usage to a bare minimum, or even to zero?”

    Shouldn’t the question be reversed thus:” Given the the apparent lack of health risks, why do legislators in the USA and EU insist on the ‘ contains sulfites’ text being displayed on wine labels?”

  • Simon Nunns

    Note that sulfur dioxide must be written with a capital S, capital O and a subscripted 2.

  • Nils Lindgren

    Good point, and, I concede, I do not. I have had the pleasure of encountering the wines of the two producers many times in formal and informal settings, and the only complaint I ever had was a Cote de Py from Foillard which had traces of bret: I consider that inappropriate for a Morgon (to carry bret, I think a wine needs more tannins than even a sturdy Morgon has – my opinion, OK?) but never any oxidation nor mouse taint, but, yes, of course, others may have had misfortunes and, to quote Hippocrates, “experience is misleading”.
    I might point out that I used the word ‘appear’, though. I did not say I knew it for sure.

  • How do you know for sure Foillard and Lapierre never had this issue? Just curious.

  • Nils Lindgren

    I consider this paragraph central: “Cornelissen believes that the knowledge of how to make wine without sulfites has simply been lost over time: ‘We have to re-learn these skills, which is a slow process.’”

    The term “mouse taint” is historically described from an era before general sulphurisation at bottling, so, it would appear the problem existed, despite the knowledge and experience. Yet there are producers who never appear to have this problem (Foillard, Lapierre) which might indicate that a solution does exist. Pending that, one is obliged to weight the risk of a mousy/oxidised/iredeemably brett-y bottle against the perceived excellence of the correct bottles. Customers choice, ultimately, and Rabbi Hillel*) is still right.
    *) “If the wine tastes foul, don’t drink it. If it tastes good, do. All else is commentary.”

  • This is far from being the only factor. The strength of the wine itself is hugely important.

    A filtered, fined white wine with no phenolic content whatsoever isn’t going to do well as it has no organic matter within to help it fight off oxidation or a thousand other threats.

    A wine with some tannins, that has been carefully exposed to a limited amount of oxygen during fermentation and maturation is much more likely to stay stable and even to age for a considerable time.

    I’ve had no sulphur wines in my own collection which I’ve grossly mistreared. House moves, the lack of a cellar and so on have created less than optimal considitions. Yet in most cases where I’ve had prematurely aged or oxidised wines its been conventional bottles, not the “no so” ones.

  • Thanks for the comment David. I didn’t have time in this short article to get into the infinite details of which you speak – but of course they are interesting.

    My anecdotal evidence from tasting, and from talking with winemakers is that sulphur additions at any point can kill off interesting compounds or characteristics that one might term as “terroir”.

    As to the muting effect of SO2, I’m not sufficiently scientifically equipped to respond to your point. I’d guess that if elements of the wine have been lost or muted due to SO2 additions, they are not going to magically reappear just because the level of free So2 reduces or the wine is aerated.

    ON the subject of organic grapes and no so2 wines I have to differ strongly though. I know many, many winemakers who farm not just organically but biodynamcially (and with certification, I would add), who come from cooler climates and are certainly not rich to the extent of the famous Bordeaux/Barolo/Napa estates.

    In fact, all five of the wines I’ve recommended come from modest estates, from people who are certainly capable as businessmen/women but who also put their care of soil and palate before monetary gain.

    The recommended wines are from regions which are neither extremely cool or extremely warm, and in several cases (Slovenian Karst, Styria) they can be pretty wet and humid.

    Furthermore, I’d counter your point to say that in general having wines with a lower PH is beneficial when not using sulphur (many of the nasties such as lactobacillus infections are less likely to develop). Thus being in a warm or even hot region is not necessarily helpful.

  • David Creighton

    no one seems to be discussing the difference between adding sulfur at the beginning of winemaking vs. the traditional adding of it just prior to bottling. does using it at the beginning to give the wine a clean start, have a negative effect on the bottled wine if none has been added at that time? And the muting effect of SO2 is most apparent when you open the wine. up to 24 hours later, if the wine is kept open in the refrigerator you will have a really pure, clean wine. and yes, extreme cleanliness, colder fermentations and storage all are necessary for low/no sulfite wine. and what about humid and wet growing areas or vintages? there it is almost impossible not to use treatments in the vineyard – read non organic – if you want clean fruit in the winery. without clean fruit entering the winery, not using SO2 doesn’t seem like a viable alternative. people making no/low sulfite wine and organic grapes are probably in warm dry regions and have lots of money for the best and cleanest facilities.

  • jaso c

    When no SO2 wines are stored in cool conditons, and always that way, you have a great chance of pure stellar bottles. Given the vagaries of the transportation situation with wines, unless you know your wines are being stored cool from winery to your house, it can be tricky.