Ever noticed that most wine labels carry a somewhat ominous warning "contains sulphites"? Read on as we bust the myths and explain what sulphites are, why they can be found in wine, and what you need to know about sulphites.
Where do wine sulphites come from?
Sulphites are preservatives commonly added to many foods - including wines.
Sulphites, sometimes referred to as sulphur dioxide, are actually a sulphur containing salt dissolved in the wine. As a stabiliser and preservative, sulphur dioxide is added during the fermentation process by winemakers, it helps to preserve a wine's character, colour and flavour. Sulphur dioxide dissolves to produce the sulphites, and as an anti-oxidant and an anti-microbial, it prevents the wine turning to vinegar (oxidising) and protects against invasion by bacteria or unwanted yeast activity. It is especially common in wines with low acidity where added stability is needed.
Wineries also often use sulphur dioxide as a cleaning agent for fermentation tanks and equipment, so sulphites can enter the wine from surface residues.
What's the issue with sulphites? Are sulphites bad for you?
Some people are allergic to sulphur, so may experience allergies as headaches and stuffy sinuses after a glass or two of sulphite containing wines. This is one of the potential causes of so-called "red wine headaches" - though other allergens and histamines that settle on the grape skin can contribute.
As an additive to wines, its usually derived from rock sulphur and industrially processed into sulphur dioxide. This extractive and industrial process - if it can be avoided - should be, to avoid overloading the sulphur cycle in our terrestrial and marine ecosystems. Increasing the amounts of active sulphur in our environment impacts climate change and marine acidification among other things.
Do organic wines contain sulphites?
In wines, sulphites also occur naturally at low levels, produced during the wine making process. This is why organic wines can also contain sulphites - these will be from the natural wine making processes, and are typically at much lower levels than if added by the wine-maker.
How much is too much?
The amount of sulphites in wine ranges from nearly zero to 350 parts per million (ppm) - the legal upper limit for conventional winemaking.
Organic and bio-dynamic wines have a lower upper limit on sulphites in their certification schemes (less than 100ppm), so you'll never experience a high sulphur wine if you drink these wines.
Note that any wine containing more than 10 ppm (parts per million) of sulphites must be labelled "CONTAINS SULPHITES". Even organic wines which have no additional sulphites added can cross this threshold. This low threshold is to alert those with allergies.
Generally in conventional wines, red wines need less added sulphites (100-150ppm), and dry, delicate whites can be higher in sulphites (130-200ppm). Sweet whites which use sulphites are usually highly dosed (270+ ppm) as the sugar binds with the sulphite first, leaving less available to do its job.
Should I avoid sulphites?
If you're allergic (approximately 1% of the adult population), then yes. If you don't know if you're allergic, but have asthma or other allergies, try sulphite-free wines and see if you can see an improvement (better sinuses, no flushing etc). Note that 5-10% of asthmatics are also allergic to sulphites.
For everyone else, there's no empirical evidence yet that avoiding sulphite laden wines is better for your health or definitely reduces headaches, but there's growing anecdotal evidence from wine-drinkers that they have clearer heads after drinking low-sulphite wines.
There's also an increasing number of people who look at avoiding additives as a stepping stone towards health improvement.
We'd also recommend avoiding wines that are very high in sulphites as at the top end, it can start impacting on the taste profile.
Finally, sulphur for sulphur dioxide production comes from either mined rock sulphur or from extraction from petroleum (though less appropriate for foods as these can be associated with higher arsenic!) - both resource intensive and if they can be avoided, we probably should!