17.1 Concentrating the Grape Must Flashcards
What styles of wines are made by concentrating the Grape Must?
many sweet and luscious styles of wine
When grape must is concentrated, what else is concentrated?
Concentrates all other grape components:
- acidity
- flavours
Why is it beneficial that as the sugar becomes concentrated, so do other components in the grape?
The concentration of acidity and flavors helps to keep these wines in balance so that sweetness does not become too dominant
What is a key reason why many of the wines made by concentrating sugar tend to be very good or outstanding in quality?
As the sugar becomes concentrated, so do acidity and other flavors, resulting in an incredibly well-balanced wine.
What can add to the costs of producing sweet wines made from grape must concentration?
- Because water is depleted, the volume of juice obtained from them is low
- The very sugary pulp is also often hard to extract during pressing
What quality of wines are typically made from concentrating the grape sugars?
premium and super premium wines
What quality of wines are typically made from concentrating the grape sugars?
premium and super premium wines
How does concentrated grape must become sweet wine?
- high level of sugars may be sufficient to stop the fermentation before reaching dryness (yeast struggle in very sugary environments especially when alcohol is also present)
- fermentation can also be stopped prematurely by chilling and/or adding SO2 and then filtering to remove yeast, giving the winemaker greater control over the balance of alcohol and sweetness
What are the 3 methods of concentrating the grape must?
- drying grapes on and off the vine
- the development of noble rot
- the freezing of grapes
If left on the vine past ripening, what happens to a grape?
- grape enters stage four of ripening
- starts to shrivel
- water is lost by grape transpiration
- the sugars concentrate
- flavours continue to develop, giving very ripe flavours
What climactic conditions are required for drying grapes on the vine?
- Long, dry autumns
- Avoid the development of grey rot, which would give off-flavours
How are wines made from dried grapes on the vine typically labelled?
Late Harvest
Give 2 examples of sweet wines made from drying grapes on the vine.
- Vendanges Tardives from Alsace
2. Spätlese from Germany or Austria
Describe how grapes can be dried on the vine in another way but not harvest late.
- the cane is cut or broken off from the vine a short time before harvest.
- grapes shrivel more quickly
- concentrates the sugars, acids and flavours within the grapes
When grapes are removed by the cane, what are the benefits?
- reduced hang time lowers risk of grey rot
- results in grapes with high levels of sugar without extra-ripe flavours
Where is the method of cutting or breaking the cane used to make sweet wine?
- Jurançon, south-west France
- sometimes used in Australia
How are sugars concentrated in grapes dried off the vine?
- grapes are picked and then dried
After they are picked, where can the grapes be left to dry? Name an example region for each option.
- may be laid out to dry in the sun in warm climates (Italy, Spain)
- dried in a temperature- and humidity-controlled room in cooler climates (Valpolicella)
How long does it take for sugar to concentrate when grapes are dried off the vine?
- can last from days to months depending on:
1. the extent of drying required
2. the speed of the drying process
What are the main benefits of drying grapes in a temperature- and humidity-controlled room?
- speed up drying
- avoid the development of grey rot
What else happens to the grapes while drying?
- causes water to evaporate
- makes sugars, acids and flavours more concentrated
What is the term for drying grapes in Italy?
Passito
Name 2 sweet wines made from drying the grapes off vine.
- Recioto di Valpolicella
- Vin Santo
What is noble rot?
- involves the action of the fungus Botrytis cinerea
- same fungus that causes grey rot
- under certain conditions it can be used beneficially in sweet wine production
Describe how noble rot-affect grapes become sweet wine.
- grapes must be fully ripe before the development of the rot
- humid, misty mornings allow rot development
- sunny, dry afternoons slows development, causes water to evaporate from the grape (concentration)
What conditions are required for the successful development of noble rot? Why?
- region that provides humid, misty mornings followed by sunny, dry afternoons
- damp morning conditions allow rot to develop
- fungus punctures the grape skin with microscopic filaments, leaving tiny holes in the skin
- warm sunny afternoons slow the development of the rot and cause water to evaporate from the grape, concentrating its sugars, acids and flavours
What aromas are introduced from noble rot?
- fungus can modify some of the aroma compounds in the grape
- can generate its own unique flavours: distinctive honey, apricot, citrus zest, ginger and dried fruit aromas
What quality of wines are typically made from noble rot affected grapes?
premium and super premium sweet wines,
Name 4 types of wines made with noble rot affected grapes.
- Sauternes
- Beerenauslese
- Trockenbeerenauslese
- Tokaji
What term is typically seen on sweet wine labels made with noble rot affected grapes?
‘botrytised’
What color grapes can be used to make noble rot wine?
White only
What are the costs associated with making noble rot wines?
- spread of noble rot is never uniform and several pickings by hand may be needed to select the best grapes (skilled labour, long period of time)
- selective picking and the fact that water has evaporated from the grapes means that the volume of juice obtained is low
- ideal conditions for noble rot do not occur every year, making these wines relatively scarce and therefore expensive
- not easy to process in the winery.
What happens if conditions are too damp?
The fungus will develop too rapidly and cause grey rot, splitting the grapes and encouraging infections
Why are noble rot-affected grapes not easy to process in the winery?
- fungus contributes enzyme (called laccase)
- capable of oxidising components in grape must and wine
- relatively resistant to SO2
- chilling, high doses of SO2, and use of inert gases are all options to minimise the oxidation - thick, high-sugar-content must difficult to press, clarify, and ferment
How are noble rot wines typically matured if relatively neutral grape varieties are used? What does this add to the wine? Give a grape example.
- oak (old or new)
- gives broader texture
- gives tannins
- adds new oak flavors (vanilla)
- e.g. Semillon
How are noble rot wines typically matured if relatively aromatic grape varieties are used? What does this add to the wine?
- stainless steel or concrete
- retain their more pronounced varietal aromas
Describe the method of sweet wine production that involves freezing grapes on the vine.
- requires healthy grapes to be left to hang on the vine into the late autumn or winter months
- when freezing temperatures arrive, water in pulp turns to ice
- when picked and pressed, ice remains in the press and the sugar content of the resulting juice is concentrated
Where is freezing grapes on the vine used?
- Eiswein in Germany and Austria
- Icewine in Canada
In Canada, at what temperature must grapes be harvested to be labelled Icewine?
−8°C (18°F) or below.
What types of vines/grapes must be used to freezing?
- winter hardy
- grapes with resilient skins that offer protection from disease
- grapes that can withstand the strain of freeze–thaw cycles
What are the 2 most popular grapes for Eiswein/Icewine? What other grape is occasionally used?
- Riesling, Vidal
- Cabernet Franc
In what vessel are Icewines typically fermented and stored? Why? What else could be used?
- stainless steel to retain the aromas and flavours of the grape variety
- Oak maturation is sometimes used to add extra flavours (vanilla, clove, etc.)
What are major risks of unpicked grapes left on the vine to freeze?
- may become infected by disease
- may be eaten by pests
How do Icewine producers protect against pests?
Netting against birds is an important cost in ice wine production
What climactic conditions are thought to be important for the development of typical ice wine character?
Freeze–thaw cycles
When are the highest quality but lowest yielding grapes picked?
late in the winter season, for example in late January
Why factors contribute to the cost of Icewines?
premium or super premium prices:
- juice yield from the grapes is very low
- conditions needed are specific
- pests and birds netting
What is cryoextraction?
- when grapes are picked in autumn (same time as dry wines) and then frozen at a winery
Where does cryoextraction typically occur?
used by winemakers in regions that would not get the typical climatic conditions required for Eiswein and Icewine
What is the main benefit of cryoextraction?
- avoids risk of leaving the grapes on the vine into late autumn or winter and perhaps losing yield to disease or pests
Why factors contribute to the cost of cryoextraction?
- requires energy to freeze the grapes
- overall is cheaper than traditional Eiswein and Icewine production
