Ch. 17: Specific Options for Producing Wines with Residual Sugar

Question 1

Drying grapes on the vine

2 types, effect on grapes, examples

Answer 1

Leaving the grapes on the vine late into harvest, the grapes will lose water and start to shrivel. Sugars, acids, and flavors become concentrated, and flavors become ripe. Dry autumns are needed to prevent grey rot, which would give off-flavors. Wines produced in this way are called late harvest, (Vendages Tardives in Alsace, Spatlese in Germany or Austria).

Another way to dry grapes on the vine is cutting off a part of the cane before harvest. The grapes shrivel more quickly than they would if still attached to he rest of the vine. This concentrates sugars, acids, and flavors, and lowers the risk of grey rot. The grapes have high sugar concentrations without ripe fruit flavors. Jurancon is made this way.

Method: Concentrating the grape must

Question 2

Drying grapes off the vine

how it’s done, effect on grapes, example

Answer 2

Grapes are picked, then laid out to dry in order to concentrate the grape must. Bunches of grapes may be laid out in the sun in warm climates, such as Italy or Spain, or dried in a temperature/humidity controlled room, as is done in Valplicella.

The drying process causes waters to evaporate, thereby concentrating the sugars, acids, and flavors.

This method is often referred to by the Italian term, appassimento (passito for short). Wines made in this way include Recioto di Valpoicella and Vin Santo.

Method: Concentrating the grape must. Passito.

Question 3

Noble rot

Answer 3

Caused by the Botrytis cinerea fungus. In order to be used for sweet wine production, the following conditions need to be met:

1. the grapes must be fully ripe before the rot develops
2. the grapes must have mislty mornings followed by sunny, dry afternoon

These conditions cause water to evaporate, concentrating sugars, acids and flavors, without the development of grey rot. The fungus also creates in own distinctive aromas of honey, apricot, orange zest, ginger, and dried fruit.

Used for Sauternes, Beerenouslese, Trokenbeerenlauslese and Tokaji.

Making wine out of grapes affected by noble rot is very expensive:
* selective picking over a long period
* lower volume of juice in grapes
* ideal conditions are not guarenteed every year
* the fungus is oxidising
* the thick, high sugar must difficult to press, clarify, and ferment

Method: Concentrating the grape must.

Question 4

Freezing grapes on the vine

Answer 4

Healthy grapes are left to hang on the vine in the fall and winter. The water in the grape turns to ice when the temperatures reach freezing. WHen the grapes are pressed, the ice remains in the press and the sugar is concentrated.

Grapes need to be winter hardy with resilient skins. The most popular grapes are Riesling and Vidal. Only wines made from grapes frozen on the vine can be called icewine (Canada) or eiswein (Germany, Austria)

There is considerable risk that the unpicked grapes may become infected or eaten by pests. Yields are typically low.

Method: Concentrating the grape must.

Question 5

Cryoextraction

Answer 5

Grapes are picked at harvest and frozen at the winery. This can be used in regions that would not be cold enough to freeze the grapes on the vine. Wine made from cryoextraction cannot be called icewine or eiswein. It is cheaper than traditional icewine production.

Question 6

Stopping fermentation

Answer 6

Stopping the fermentation process before the sugars have been converted to alcohol by yeast, resluting in a wine with residual sugar.

The winemaker has control of the level of sugar. These wines taste off-dry to med-sweet. The process is simple, quick and low risk and is used to produce wines that are inexpensive and mid-priced (white zin is an example).

There is not the same level of intensity or complexity as wines made by concentrating the sugar.

The most common way of interrupting the fermentation is by chilling to below 50F, and/or adding a high dose of SO2 to inhibit the yeast.

Process: Stoppong the fermentation

Question 7

RCGM

Answer 7

Rectified Concentrated Grape Must. It’s a sweetening component added to dry wine before bottling.

It is processed so that it just contains the sugar from the grape, and is therefore neutral flavor-wise.

Process: Blending in a sweetening component

Question 8

Süssreserve

Answer 8

Unfermented grape juice. It’s a sweetening component added to dry wine before bottling.

Process: Blending in a sweetening component