17.2 Stopping the Fermentation

Question 1

When a fermentation is stopped before it is finished, what is the result in the wine?

Answer 1

-sugar in grapes is converted to alcohol by yeast
When this process is interrupted the result will be
- higher levels of residual sugar
- lower levels of alcohol

Question 2

Explain how and when sweet wine is made by stopping the fermentation?

Answer 2

Target product:
inexpensive or mid-priced wines
off-dry to medium-sweet
- the winemaker has control over the level of sugar in the final wine

The process is quick, simple and low risk.

• chilling to below 10°C (50°F) and/or
• adding a high dose of SO2 to inhibit the yeast
• racked off sediment
• sterile filtered to ensure fermentation does not start again later

Question 3

Give an example of a wine that is sweet because fermentation was stopped earlier. What is the g/l of RS? What is the abv?

Answer 3

White Zinfandel
35 g/l RS
10 abv

Question 4

What are the disadvantages of making sweet wine by stopping the fermentation?

Answer 4

• rare to find the same intensity and/or complexity of the wines produced by concentrating the grape sugars
• tend not to reach outstanding levels of quality
• exception is fortified wines which will have additional alcohol adjustments, and will develop complexity while ageing