13.1 Oxygen and Sulfur Dioxide - Sulfur Dioxide Flashcards
WSET Issue 1.1 2020
Name the 2 main functions of SO2.
- Anti-oxidant
- Anti-microbial
How does SO2 act as an antioxidant?
- SO2 only reacts with oxygen itself very slowly
- Reacts with the PRODUCTS (e.g., oxidative enzymes) of oxidative reactions
- These products cannot oxidize further compounds in the wines
How does SO2 act as an anti-microbial?
- Inhibits development of microbes (yeast and bacteria)
- Different species vary in SO2 tolerance
In what state is SO2 applied?
Gas, solid or liquid.
Name 3 chemical forms of SO2.
- Sulfur dioxide
- Metabisulfite
- Potassium bisulfite
Does SO2 occur naturally? In the context of wine, how does it occur? What amount are produced?
Small amounts (10 mg/L) naturally produced during fermentation
What are the maximum allowable levels of SO2?
- 160 mg/L for red, 210 mg/K white
- Sweet wines permitted higher levels
- Organic wines – lower levels
Is SO2 a toxic substance?
Yes. Its use is determined by local law.
What can So2 cause in some people?
Allergic reactions
If a bottle of wine contains more than 10 mg/L of SO2, what must happen?
“Contains Sulfites” must be printed on the label.
Do natural wine producers use SO2?
Usually no, but may in tiny amounts.
Is SO2 found in organic wines in the US?
No. SO2 use in organic wines is forbidden in the US.
At what points in the winemaking process is SO2 often used?
Larger amounts added at
1. Crushing
2. End of MLF
3. Bottling
Is it better to add SO2 throughout the winemaking process?
No. Adding it in small amounts at each step of the winemaking process is less effective than adding it in larger amounts at 3 stages: crushing, end of MLC and bottling.
What is “bound” SO2?
“Bound” SO2 reacts with compounds in the liquid
