Specific options for producing wines with RS Flashcards
Spcific styles for producing wines with RS
The choice of method will be determined by the style the winemaker want to produce
The objective is to produce a wine with balanced RS and acidity, and with flavour concentration appropriate with the level of sugar
Key ways of producing wines with RS are:
- Concentrations the sugar in the grape must
- Stopping the fermentation before dryness
- Blending in a sweetening component to the wine
Concentrating the grape must
Method used to produce sweet and luscious styles of wine
The concentration of sugars in the grapes may be sufficient to stop the fermentation before reading dryness; yeast struggle in sugary environments, especially when alcohol is also present, and fermentation will naturally stop
However, fermentation can also be stopped prematurely by chilling or adding so2 and then filtering to remove the yeast, giving the winemaker a greater control over the alcohol and sugar levels in the wine
The must is concentrated by the reduction of water in the grape, hence this process does not only concentrate sugar, but acidity and flavors as well (the later help to keep the wine in balance so the sweetness does not become too dominant) and by that enhance quality
Drying grapes on the vine (evaporate water) leads to flavors of dried fruits; therefore these wines can have more complexity than those that are made by stopping fermentation by chilling or adding a sweetening component
Because water is depleted, the volume of juice obtained for the grapes is low, adding to the coast, premium and super-premium wines
Methods include:
- Drying grapes on the vine
- Drying grapes off the vine
- Freezing of grapes
Drying grapes on the vine
If grapes are left on the vine, the grape will enter stage 4 of ripening in which the grape starts to shrivel
Water is lost by grape transpiration and sugars concentrate
Flvours continue to develop, giving very ripe flavours (dried fruits)
Long dry autumns are needed for this option to avoid the development of grey rot, leading to off-flavors and lower yields
Wines may be labelled ‘late harvest’, like Vendanges Tardives from Alsace and Spatlase from Germany
Another method is to cut of the cane of a vine short before harvest while the grapes are still attached (cane usually remains attached to the trellis at this point), grapes will shrivel more quickly than the would if they were still attached to the vine, reducing hang time lowers the risk of grey rot and maintain grapes with very high levels of sugar without extra ripening flavours. Often used Jurancon, south-west France
Drying grapes of the vine
Grapes are picked and then dried for days to months
Grapes may be laid out to dry in the sun in warm climates (Spain) or dried in temperature and humidity controlled rooms in cooler climates, which give them the ability to speed up the process, avoiding the development of grey rot (Valpolicella). The later is clearly more expensive than drying grapes in the sun
The drying process causes water to evaporate, concentrating sugar, acids and flavours
Often referred to the Italian term, Passito
Wines made this way include Recioto di Valpoilicella and Vin Santo
Noble Rot
Involves the action of the fungus Botrytis cinerea
The same fungus that causes grey rot; however, under certain conditions can be used beneficially in sweet wine production, often termed noble rot
Grapes must be fully ripe for the development of Nobel rot, and grapes must be grown in a region that provides humid, misty mornings followed by sunny and dry afternoons. The damp conditions in the morning allow the rot to develop
The fungus enters the grapes skin, leaving tiny holes in the skin
Dry and sunny afternoons slow the development of rot and cause water to evaporate, concentrating sugar, acidity and flavors in the grapes
Wines that are affected by Noble rot have distinctive honey, apricot, citrus zest, ginger and dried fruit aromas
Premium, super-premium wines (Sauternes, BA, TBA and Tokaji)
The spread of noble rot is never uniform and therefore several picking by hand may be needed to select the best grapes (triage) this is an expensive process that requires skilled labour
Selective picking and the evaporation of water makes that the volume of juice obtained is low
Some regions do not have the ideal conditions every year, making these wines scare and expensive
These wines are often matured in oak, if a relatively natural variety is used, adding texture. However, wines made from aromatic varieties may be stored in stainless steel to retain their more pronounced varietal aromas
Freezing the grapes
Leaving grapes to hang on the vines into the late autumn or winter months
When its start freezing, the water in the grape pulp turns to ice
When grapes are picked and pressed, the ice remains in the press and the sugar content of the resulting juice is concentrated
Eiswein/Icewine
Vines used for these styles need to be winter hardy and produce grapes with resilient skins that offer protection from disease and can withstand the strain of freeze; Riesling, Vidal
Often fermented in stainless steel to retain the aromas and flavours of the variety
Conditions for producing these wines are very specific, and can only be produced in a few regions and even than grapes may become infected by disease or eaten by pests (netting against birds, adds to cost)
Juice yield from the grapes is also very low for this method, all these factors mean that these wines command premium or super-premium prices
Cryoextraction
Similar affect of freezing grapes on the vines
Grapes are picked in the autumn (same time as for dry wines) and frozen at the winery
Can be used in regions where the typical climate conditions to produce Eiswein not occur and does not include the risks of leaving the grapes on the vine into late autumn or winter and perhaps loosing yield to disease or pests
Not allowed in the production of Eiswien and Icewine, wines made by cryoextraction may not use these terms on the label
This method requires energy to freeze the grapes, but overall its cheaper than the production of traditional Eiswein or Icewine
Stopping the fermentation
Stopping the fermentation before all the sugars have converted to alcohol results in a wine with residual sugar
Winemaker has control over the lever of sugar in the final wine, the earlier the ferment is stopped the higher the level of sugar that remains, but also lowers the level of alcohol
Moscato d’Asti is made this way (4.5%-6%)
Usual these wines tend to be off-dry to medium-sweet, for example White Zinfandel, rather than fully sweet
The process is quick, simple and low risk (compared to concentrating the grapes must) and often used for wines that are inexpensive to mid-priced
Most common way to interrupt the fermentation is by chilling to below 10 and/or adding a high dose of so2 to inhibit the yeast
The wine is than racked of its sediment and sterile filters to ensure the fermentation does not start again at a later stage
Fortification, the addition of alcohol to kill the yeast is also an option, but this radically changes the style of the wine (fortified wines)
Blending in a sweetening component
Easiest way of producing a wine with residual sugar
Dry wines can be stored until its ready to be bottled and than the sweetening component is blended in (dry wines are less susceptible to microbial spoilage then wines with RS)
Winemaker is able to measure and add the amount of sweetener that is needed to produce the style that is desired, giving a high level of control
Compared to methods of concentrating the must where the volume of the wine made is reduced, adding a sweetening component will maintain or possibly increase the volume of the final wine and therefore does not add to the cost in this way
This technique is suited for high volumes of inexpensive wines, and quality is likely to be acceptable to good
RCGM and unfermented grape juice (sussreserve) are common sweetening components, both of these additions are inexpensive
Unfermented grape juice contributes as gape-juice like character. RCGM is processed so it just retains the sugar for the grapes (neutral, and not adding any flavour to the wine)
The use of sugar is not permitted in European PDO wines and unfermented grape juice must come from the same wine region as the wine is being made
