D1.C17. Specific Options for Producing Wines with Residual Sugar

Question 1

What are the key ways to produce wines with residual sugar?

Answer 1

• Concentrating the sugar in the grape must
• Stopping fermentation before dryness
• Blending in a sweetening compound

Question 2

Which factors determine the method to be used for producing wines with residual sugar?

Answer 2

• Style of the wine
• Quality and the price of the wine
• Climate of the vineyard
• Local wine legislation

Question 3

How can the fermentation be stopped, when concentration of the grape must is the method of choice to produce a wine with residual sugar?

Answer 3

• It can stop by itself as concentration of sugars in the grape must may be sufficient to stop the fermentation
• It can also be stopped prematurely by chilling and/or adding SO2 and then filtering to remove the yeast (greater control over the balance of alcohol and sweetness)

Question 4

What are the effects of reduction of water in the must on the wine?

Answer 4

• Concentrate sugars
• Concentrate flavours
• Concentrate acidity

Question 5

What are the key reasons why many of the wines made by concentrating grape must tend to be very good or outstanding in quality?

Answer 5

• Increase in acidity and flavours helps to keep these wines in balance so that sweetness does not become too dominant
• It also add sits own flavours. For example, drying grapes off the vine can lead to flavours of dried fruits so can have more complexity than those simply made by other methods

Question 6

Why are the wines made by concentrating grape must usually sold for premium or super-premium prices?

Answer 6

• Because water is depleted, the volume of juice obtained from the grapes is low
• The very sugary pulp is also often hard to extract during pressing
• It has risks (like infection)
• Usually needs more and skilled labour

Question 7

What are the methods of concentrating the grape must?

Answer 7

• Drying grapes on the vine
• Drying grapes off the vine
• Noble rot
• Freezing the grapes

Question 8

What is the result of drying the grapes on the vine in terms of aroma profile?

Answer 8

It helps developing very ripe flavours e.g. Pinot Gris may develop from stone fruit when ripe to tropical fruits and dried stone fruits as it becomes extra-ripe

Question 9

Why dry autumns are needed for drying the grapes on the vine?

Answer 9

To avoid the development of grey rot, which would give off-flavours

Question 10

What are the common label terms used for the wines produced by the grapes dried on the vine?

Answer 10

• Late harvest
• Vendanges Tardives
• Spätlese

Question 11

What is another method for drying grapes on the vine? What is its advantage? In which wine regions is it used?

Answer 11

• Cutting or breaking off the cane from the while still attached to the trellis
• The grapes shrivel more quickly but the reduced hang time lowers, but does not eliminate, the risk of grey rot
• Jurançon and sometimes in Australia

Question 12

How long does the drying grapes off the vine last?

Answer 12

It can last from days to months depending on the extent of drying required and the speed of the drying process

Question 13

What are the ways to dry the grapes off the vine?

Answer 13

• They may be laid out to dry in the sun in warm climates, such as southern Italy or Spain
• They may be dried in a temperature- and humidity-controlled room in cooler climates to speed up drying and avoid the development of grey rot, for example in Valpolicella

Question 14

What is the Italian term for the wines produced by drying grapes off the vine? Name two wines produced with this method.

Answer 14

• Passito
• Recioto di Valpolicella, Vin Santo

Question 15

What are the conditions that are required for the noble rot to develop?

Answer 15

• Grapes must be ripe
• A region that provides humid, misty mornings followed by sunny, dry afternoons

Question 16

By which mechanism does the Botrytis cinerea concentrate sugar in the grapes?

Answer 16

The fungus punctures the grape skin with microscopic filaments, leaving tiny holes in the skin. The warm sunny afternoons slow the development of the rot and cause water to evaporate from the grape, concentrating its sugars, acids and flavours

Question 17

What are the unique flavours of the wine made from the grapes affected by noble rot?

Answer 17

Honey, apricot, citrus zest, ginger and dried fruit aromas

Question 18

What does the term “botrytis”denote?

Answer 18

Botrytis’ is frequently used as a synonym for noble rot, and the term ‘botrytised’ is often seen on sweet wine labels

Question 19

Why are the botrytised wines sold for premium to super-premium prices?

Answer 19

• The spread of noble rot is never uniform and several pickings by hand may be needed
  to select the best grapes
• This is an expensive process as it requires skilled labour over a prolonged period of time
• In some regions the ideal conditions for noble rot do not occur every year, making these wines relatively scarce
• If conditions are too damp, the fungus will develop too rapidly and cause grey rot, splitting the grapes and encouraging infections
• The fungus contributes an enzyme (called laccase) that is capable of oxidising a number of components in grape must and wine, and is relatively resistant to SO2 so chilling, high doses of SO2 and use of inert gases may be required
• The thick, high sugar content must is also difficult to press, clarify and ferment

Question 20

What is the aim of oak maturation for botrytised wines?

Answer 20

• Oak can give a broader texture (the oak contributes some tannins)
• New oak adds flavours such as vanilla

Question 21

Oak maturation is preferred for botrytised wines produced from what kinds of grapes?

Answer 21

Especially if relatively neutral grape varieties are used, for example Semillon. Wines made from more aromatic grape varieties tend to be stored in stainless steel or concrete to retain their more pronounced varietal aromas

Question 22

By which mechanism does freezing grapes on the vine concentrate sugar in the grapes?

Answer 22

When the grapes are picked and pressed,
this ice remains in the press and the sugar content of the resulting juice is concentrated

Question 23

At which temperature should Canadian Icewine grapes must be harvested?

Answer 23

At −8°C or below

Question 24

What should be the properties of the vines used to produce icewines?

Answer 24

• They should be winter hardy
• The grapes should have resilient skins that can offer protection from disease and can withstand the strain of freeze–thaw cycles

Question 25

What are the most popular grapes to produce icewines?

Answer 25

• Riesling
• Vidal

Question 26

Are black grapes used for producing icewines?

Answer 26

Black grapes suchas Cabernet Franc are occasionally used

Question 27

Is oak maturation a common practice for producing icewines?

Answer 27

No, they are often fermented and stored in stainless steel to retain the primary aromas. Oak maturation is sometimes used to add extra flavours (vanilla, clove, etc)

Question 28

Why do the icewines command premium or super-premium prices?

Answer 28

• It can only be produced in a few regions where and when weather conditions allow
• Juice yield from the grapes is very low
• There is considerable risk that the unpicked grapes may become infected by disease or eaten by pests (netting against birds is an important cost in ice wine production)

Question 29

What is the alternative way of producing icewine?

Answer 29

Cryoextraction: picking grapes in the autumn and then freezing them at a winery

Question 30

Can the wines produced by cryoextraction be labelled as “icewine” or “eiswein”?

Answer 30

No

Question 31

What is the economic burden of cryoextraction?

Answer 31

It requires energy to freeze the grapes, but overall is cheaper than traditional Eiswein and Icewine production

Question 32

What is the advantage of stopping the fermentation as a method to produce wines with residual sugar?

Answer 32

Winemaker has control over the level of sugar
in the final wine

Question 33

What is the usual residual sugar profile of the wines produced by stopping the fermentation?

Answer 33

These wines taste off-dry to medium-sweet, rather than fully sweet

Question 34

Why are the wines with residual sugar, produced by stopping the fermentation inexpensive or mid-priced? What is the exception?

Answer 34

• Because the process is relatively quick, simple and low risk
• Some fortified wines that may undergo long periods of ageing and be extremely complex

Question 35

What are the methods to stop the fermentation?

Answer 35

• Chilling to below 10°C snd/or adding a high dose of SO2. The wine is then racked off its sediment and sterile filtrated
• Fortification (radically changes the style of the wine)

Question 36

What is the easiest way to produce a wine with residual sugar?

Answer 36

Adding a sweetening component

Question 37

What are the advantages of producing wines with residual sugar by adding a sweetening component?

Answer 37

• The dry wine can be stored until it is ready to be bottled and then the sweetening component blended in (less susceptible to spoilage organisms)
• High level of control
• Enabling high volumes of a consistent product to be made
• It will maintain or possibly slightly increase the volume of the final wine

Question 38

What is the quality and price profile of the wines with residual sugar produced by adding a sweetening component?

Answer 38

• Acceptable to good quality
• High volume of inexpensive wines

Question 39

What are the common sweeetening components?

Answer 39

• Sugar
• RCGM (rectified concentrated grape must)
• Unfermented grape juice (Süssreserve)

Question 40

What are the advantages of RCGM over Süssreserve?

Answer 40

• RCGM s neutral unlike Süssreserve which contributes grape-juice like character
• Smaller amounts are needed to sweeten the wine

Question 41

How can local wine regulation can determine the substances that can be used to sweeten the wine?

Answer 41

• EU does not permit the use of sugar
• For PDO wines, the unfermented grape juice must come from the same wine region as the wine being made