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Wiens on Wine - Understanding Sulphites

Posted on October 6, 2023

This post originally appeared in our Wine Line email newsletter. Stan was kind enough to let us post it on our blog as well. Thanks, Stan!

Learn alongside Stan as he completes WSET Level 4.

Days to Final Exam: 384

This week’s focus: The dreaded "S" Word: Sulphites

“This product contains sulphites” is what we will commonly read on the back label of many wines. Is this good or bad? I will start with my conclusion. Yes! Sulphur Dioxide is necessary, even unavoidable in various aspects of winemaking, yet can be harmful if consumed in too large a quantity. Thankfully, regulations around SO2 quantities that are allowed are moving in a more restrictive direction.

Being concerned about sulphite consumption is understandable, but with wine, the worry sometimes needs a bit of context to understand what the proportion is and what it means. Consider that dried fruits, which many of us consume regularly, can carry as much as ten times the amount of sulphites compared to even the most heavy-handed use in wine.

With all of the concern about sulphites, why do wines contain them at all? There are good reasons for adding SO2. Below is an explanation of how, when and why sulphites are used in the wine industry:

  •   So2 is used as a preservative in winemaking to prevent oxidation and bacterial growth.
  • They are added to wine in small amounts during fermentation, and again before bottling, to preserve freshness and protect against spoilage.
  • Sulphites also have a role in stabilizing colour and flavour in wine.
  • SO2 can be applied in gas, liquid or solid forms and will often be added to the bins of grapes immediately after harvesting to enable a safe trip to the winery.
  • In red wines, the European countries limit SO2 to 150 mg/L and in white wines, 200 mg/L. Sweet wines will usually contain even more sulphites than dry wines.
  • The timing of adding SO2 is everything. You can use less SO2 overall if you use larger amounts during more critical times of wine production, such as during grape crushing or just before bottling.
  • Good winery hygiene and diligent grape sorting limit the amount of microbial spoilage and therefore the need for additional SO2.
  • Picking grapes often happens at night, when temperatures are cool, which also limits microbial spoilage.

Fun Fact:

Even in organic and natural winemaking, SO2 occurs, well, organically and naturally. SO2 is a natural by-product of fermentation. If it can stay below 10mg per litre, a producer can label their wine “sulphite free”. However, even in the most conservative winery (sustainable, biodiverse, organic, natural or otherwise), a wine will contain more than 10mg per litre.


Just drink wine and enjoy!

Stan Wiens can be found working at our shop sporadically in between lengthy bouts of drinking wine ("studying") in order to complete Level 4 of the WSET program.

You can also find Stan on Instagram: @wiensonwine

This entry was posted in Wine, Wiens on Wine



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