D1.C17. Specific Options for Producing Wines with Residual Sugar Flashcards
What are the key ways to produce wines with residual sugar?
- Concentrating the sugar in the grape must
- Stopping fermentation before dryness
- Blending in a sweetening compound
Which factors determine the method to be used for producing wines with residual sugar?
- Style of the wine
- Quality and the price of the wine
- Climate of the vineyard
- Local wine legislation
How can the fermentation be stopped, when concentration of the grape must is the method of choice to produce a wine with residual sugar?
- 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)
What are the effects of reduction of water in the must on the wine?
- Concentrate sugars
- Concentrate flavours
- Concentrate acidity
What are the key reasons why many of the wines made by concentrating grape must tend to be very good or outstanding in quality?
- 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
Why are the wines made by concentrating grape must usually sold for premium or super-premium prices?
- 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
What are the methods of concentrating the grape must?
- Drying grapes on the vine
- Drying grapes off the vine
- Noble rot
- Freezing the grapes
What is the result of drying the grapes on the vine in terms of aroma profile?
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
Why dry autumns are needed for drying the grapes on the vine?
To avoid the development of grey rot, which would give off-flavours
What are the common label terms used for the wines produced by the grapes dried on the vine?
- Late harvest
- Vendanges Tardives
- Spätlese
What is another method for drying grapes on the vine? What is its advantage? In which wine regions is it used?
- 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
How long does the drying grapes off the vine last?
It can last from days to months depending on the extent of drying required and the speed of the drying process
What are the ways to dry the grapes off the vine?
- 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
What is the Italian term for the wines produced by drying grapes off the vine? Name two wines produced with this method.
- Passito
- Recioto di Valpolicella, Vin Santo
What are the conditions that are required for the noble rot to develop?
- Grapes must be ripe
- A region that provides humid, misty mornings followed by sunny, dry afternoons
By which mechanism does the Botrytis cinerea concentrate sugar in the grapes?
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
What are the unique flavours of the wine made from the grapes affected by noble rot?
Honey, apricot, citrus zest, ginger and dried fruit aromas
What does the term “botrytis”denote?
Botrytis’ is frequently used as a synonym for noble rot, and the term ‘botrytised’ is often seen on sweet wine labels
Why are the botrytised wines sold for premium to super-premium prices?
- 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
What is the aim of oak maturation for botrytised wines?
- Oak can give a broader texture (the oak contributes some tannins)
- New oak adds flavours such as vanilla
Oak maturation is preferred for botrytised wines produced from what kinds of grapes?
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
By which mechanism does freezing grapes on the vine concentrate sugar in the grapes?
When the grapes are picked and pressed,
this ice remains in the press and the sugar content of the resulting juice is concentrated
At which temperature should Canadian Icewine grapes must be harvested?
At −8°C or below
What should be the properties of the vines used to produce icewines?
- 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
