Sulphites in wine – effect on flavour

This was actually the post I intended to write a few weeks ago, but then I realised there are many poorly-understood aspects of sulphites, and decided first to embark on a mini-series of posts on the subject – clearing up a few points, maximum and typical concentrations and headaches.

Health-effects aside, most people seem to regard the primary function of sulphites to be the prevention of spoilage. It kills off bacteria and yeasts that can create nasty off-flavours, and works against oxidation, allowing the supposedly unsullied essential wine characteristics to shine through. And many people who object to the use of sulphites think and argue in the same arena, saying that the off-flavours add interest and character. However, it is true that some also praise the clarity and brightness of fruit flavours in natural wine. Terroir is mustered by both pro- and anti-sulphite factions to serve their separate causes: either saying the faults resulting from insufficient sulphur mask terroir, or that those qualities are actually a reflection of terroir, because the microorganisms that cause them are an essential component of it.

What is often common to both sides of the argument is a general failure, beyond the mere existence or absence of faults, to recognise the far-reaching consequences of sulphites on the organoleptic properties of wine. This point was clearly made in a recent SevenFifty Daily article, How Sulfites Affect a Wine’s Chemistry, which I make no apology for summarising below. I encourage you to read the whole article for further details and references.

There is a lot we still don’t know about how sulphites impact on wine chemistry, but research is starting to show that they affect a large number of chemical components in wine, and its organoleptic properties. Notably, sulphites act with oxygen and acetaldehyde to affect colour and mouthfeel, and aromatic compounds are also altered significantly. For example, a Sauvignon Blanc made reductively with sulphites in stainless steel tanks has a very different aromatic profile to one made in barrels with no sulphite additions. The effects are not only wide-ranging, but long-lasting. Research with Chardonnay shows that differing amounts of sulphite cause differences in the finished wine, even after several years of bottle age

Sulphite additions early in the winemaking process are particularly important. You either allow oxidative processes at that stage by not using sulphites, or must commit to fighting oxidation with sulphites throughout the winemaking process. Counterintuitively, winemaker experiments in vinifying with and without sulphites have shown that the “without” wines tend to have better long-term resistance to oxygen. They also tend to taste older when young, but show freshness of fruit as they get older, also exhibiting softer tannins, lighter colour, and more floral notes. On the other hand, reductive notes (not necessarily a bad thing) and cassis are more likely to be associated with sulphite additions.

The author of the SevenFifty Daily article seems to argue for the pragmatic approach of letting science decide how sulphites are to be used, with the goal of creating a stable wine that has the organoleptic properties intended by the winemaker. I certainly have some sympathy with that view, but on the other hand I also fully appreciate the ideological stance that added sulphites simply do not belong in wines. Should we use them simply because they are perceived by some to be beneficial? And if so, what other additions should be permitted on the same basis?

Irrespective of what we think, the presence or absence of sulphites in wine is an undeniably important issue – it affects stability in complex ways, and sulphites are a dangerous allergen for some – but also, as is becoming increasingly clear, its effect on flavour and mouthfeel can be profound, and cannot be ignored.

Author: Steve Slatcher

Wine enthusiast

8 thoughts on “Sulphites in wine – effect on flavour”

  1. I think you have addressed the most important aspect in some ways. The health issues are, I know, what some people wear by though I am sceptical. I do think the principle of not wanting to add anything to the wine is most crucial (I would with my background). But flavour is vitally important too. I am currently in Spain and a umber of white wines that I taste are very artificial in flavour to my palate. Then, I am so suffused in natural wine that may not be surprising. I do detect different flavours and mouthfeel (horrible word but you know what I mean).

  2. Thanks Alan. I hesitated to use both “mouthfeel” and “organoleptic”, but on balance though they were better than the alternatives! Health issues are important for those that are actually affected, but a bit of a distraction for most people. I hope I did not downplay too much the importance of flavour to natural-wine lovers. I was very aware that it is important for some, but as a part-time drinker of natural wines it is often the ideology that seems to get most emphasis.

  3. Plus…sulphites also used by some to block (in part or fully) the malolactic secondary fermentation in white wines. That changes the resultant acidity, texture etc, in other words, a fundamental style change and one that adds diversity. For me, it’s about how much sulphur is used to achieve style and stability and hence the care and skill used to achieve this – there is a Goldilocks usage zone.

  4. To achieve a particular result there is indeed a Goldilock’s zone in terms of usage – quantity and timing – and we are learning more about how to do that. I think that was the main point of the article I was reading. But we must also remember that one person’s ideal result may not be another’s.

    And how did we even get ouselves into a position where we add sulphites at all? I am not totally decided, but after my few weeks of reading and writing on the subject I am now moving towards the ideological position of zero-tolerance.

  5. Excellent, Steve.
    I often think hard about added sulphur. Some producers really seem to have got the hang of not using it, whilst some natural wines, albeit to a lesser extent than some years ago, seem to suffer from a lack of it. And when I say suffer I don’t just mean spoilage. Sometimes, when you get the chance to taste cuvées identical to each other save for being made with and without added sulphur, you do sometimes feel that the added sulphur wine is somehow dulled in comparison (some say less alive).
    Whilst sulphur is not fully understood in the ways it affects a wine’s chemistry, I am not one of those who feel a “natural wine” definition must include “no added sulphur”. But at the same time, I want to see sulphur additions minimised.
    There are some truly amazing wines made without sulphur additions, and we need to understand what makes them so good.

  6. Thank you, David. Perhaps something that bears more consideration in “minimal or no added sulphites” wines is the “natural sulphite” content, which can also be manipulated more or less naturally.

  7. The position was probably created by commercial realities. Having stable saleable fresh wines at merchants that were no longer local that could survive the various vagaries of transportation plus the ability to replicate the same wine in a recognisable way year in year for what is a Batch process. Long before the invention of other means such as cold chilling and micron filters or adding enzymes, all of which are modern tech and expensive. And markets still prefer whites which are clear and fresh and diverse. The is room thankfully for no or low sulphur but my take is that careful use is fine. My objection is to the indiscriminate use that is a blight

  8. That sounds like a likely history, Paul. I don’t diagree with your views on sulphites either – it’s just that my mind is not fully made up.

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