SO2

Question 1

Addition of SO2 to the unfermented must will do what to a white wine must?

Answer 1

1) preserve the must from oxidisation
2) stun the weaker yeast allowing the good, stronger yeasts to thrive
3) kills bacteria

Question 2

Addition of SO2 to the unfermented must will do what to a RED wine must?

Answer 2

micro-organisms on the skins cannot be fully controlled by the SO2. Some of them will become active and create acetaldehyde . Acetaldehyde binds to free SO2, rendering it useless. SO2 also binds to anthocyanins, meaning it can’t protect the wine from O2.
BUT - it helps with the extraction of polyphenols (reasons unknown)

Question 3

Name some of the different forms in which SO2 can be used.

Answer 3

1) gas
2) liquid
3) solid
4) potassium bisulphite
5) potassium metabisulphite

Question 4

what are the two main benefits of SO2

Answer 4

1) anti oxidant (note: it works most effectively on the products of oxidation - rather than on the oxygen itself)
2) anti-microbial (yeast and bacteria)

Question 5

What is the legal EU limit of SO2 in

a) red wines
b) white wines
c) sweet wines

Answer 5

a) red: 160mg/L
b) White: 210 mg/L
c) sweet: >210mg/L

Question 6

What is the average amount of SO2 produced naturally during pfermenation

Answer 6

10mg/L

Question 7

A higher pH level will have what effect on SO2 levels in molecular form?

Answer 7

The higher the pH the must (so the more alkaline it is), the less free SO2 is converted into molecular (useful) form, so the wine is less protected. The result is you need more SO2 to ensure there is enough in molecular form to keep the wine safe from O2.

Question 8

What is bound SO2?

Answer 8

Bound SO2 is ineffective against O2 and microbes. It is has been dissolved in the must and binds to other compounds, rendering it useless for its primary purposes.

Question 9

What state is most free SO2 in?

Answer 9

Gas form. It is relatively inactive. A smaller percentage of the free SO2 will be in molecular form - this is the most effective against O2 effects and killing microbes.

Question 10

What are the key times to add SO2 during winemaking?

Answer 10

1) Crushing
2) End of MLF
3) Bottling

It’s considered better to add a larger amount at those three key stages than small amounts throughout the process.

Question 11

What is a draw back of too much SO2? (4 reasons)

Answer 11

1) It will dull the flavour of the wine.
2) Legal limitations must be considered
a) red: 160mg/L
b) White: 210 mg/L
c) sweet: >210mg/L
3) In the states no SO2 is allowed for Organic and BD wines, only naturally produced amount (10mg/L)
4) Can give a harsh flavour

Question 12

What is an alternative to addition of SO2 to reduce microbial presence?

Answer 12

Good winery hygiene and meticulous sorting to remove diseased grapes.

Question 13

What is an alternative to the addition of SO2 to reduce oxidation ?

Answer 13

Temperature control - keeping the grapes, must and wine cool will slow the effects of O2 as well as limit damage from bacteria.