Sweet winemaking

Question 1

What are the principals ways of obtaining sweet wine ?

Answer 1

1. Stopping the fermentation
2. Adding a sweetening component
3. Concentrating grape sugars (as well as acids and flavours)
4. a Noble rot
5. b Passerillage, drying grapes on the vine, e.g. Late harvest
6. c Drying grapes after picking, e.g. passito wines
7. d Freezing grapes on the vine, e.g. Eiswein

Question 2

What are the ways to stop fermentation ?

Answer 2

• fortification (addition of grape spirit) kills the yeast
• addition of a high dose of SO2
• chilling and filtering (to remove any remaining yeast), e.g. Kabinett and Spätlese and Asti sparkling wines. These wines are typically low in alcohol.

Question 3

Name 3 wines made with noble rot and explain how the development of noble rots changes the wine flavour and style

Answer 3

Sauternes, Tokaji, Beerenauslesen and Trockenbeerenauslesen from Germany and Austria.

The fungus creates its own unique flavours in the grape. Distinctive honey, apricot, citrus zest and dried fruit aromas.

Question 4

The fungus botrytis cinerea punctures the grape skin with microscopic filaments, leaving tiny holes in the skin. Under which conditions does noble rot develop instead of grey rot ?

Answer 4

The fungus Botrytis cinerea also creates grey rot, but under specific conditions noble form instead:

• grapes must be fully ripe before development of rot
• the region must provide humid misty mornings (allowing the rot to develop). But if too damp, grey rot will develop, splitting the grape berries and encouraging infections.
• and sunny dry afternoons (that slow the development of rot and cause water to evaporate, thus concentrating acids, flavours and sugars).

Question 5

Why is botrytised wine expensive ?

Answer 5

It requires several pickings by hand by skilled labour over a prolonged period of time, as the spread of noble rot is never uniform.

Question 6

What weather conditions are required for drying grapes on the vine ?

Answer 6

When grapes have reached full sugar ripeness, they begin to dehydrate and to to raisins on the vine, increasing the sugar concentration in the juice.
Warm dry autumns are needed, or else grey rot can develop.

Question 7

What are the characteristics of a wine made from grapes dried on the vine ?

Answer 7

Over-ripe fruit character (dried fruit, trpical fruits) and a richly textured mouthfeel.

Question 8

What conditions are required to dry grapes after picking ?

Answer 8

Conditions must be warm and dry, and care must be taken to remove all rotten grapes or the rot will spread.

Question 9

What are the characteristics of a wine made from grapes dried after picking ?

Answer 9

Wines can have a raisiny quality, e.g. Recioto della Valpolicella DOCG

Question 10

How is Eiswein made ?

Answer 10

Healthy grapes are left hanging on the wine into the winter months. When freezing temperatures arrive, the water in the grape pulp turn to ice. When grapes are picked and pressed, this ice remains in the press and therefore the sugar content of the resulting juice is increased.
e.g. Eiswein from Germany and Icewinee from Canada.

The wines have a very pure varietal character.

Question 11

Why are sweet wines often low in alcohol ?

Answer 11

The sugar concentration makes the alcoholic fermentation stop when the yest have converted as much sugar into alcohol as they can. This can happen at as low as 7 % abv, because yeast struggle to survive in very sugary environments.
E.g. Trockenbeerenauslese.

Question 12

How is the creamy, spicy style of Californian Fumé blanc as well as of the whites of Pessac-Léognan obtained ?

Answer 12

Sauvignon blanc is barrel fermented
Ambient yeast may be favoured to obtain greater complexity
Maturation on the lees for months incl. MLF, normally
New oak barrels for at least a proportion of the wine.