Sweet Winemaking Flashcards
List the key ways of producing wines with residual sugar
Concentrating sugars in must
Interrupting fermentation
Blending a sweet component
Describe the sweet winemaking method called concentrating the grape must
Concentrating the grape must method is used to produce many sweet and luscious styles of wine. Concentration of sugars in must may be sufficient to stop fermentation before reaching dryness. Yeast struggles in very sugary environments, especially when alcohol is present, and naturally stops fermentation at low levels of alcohol.
Describe an alternate way to prematurely stop fermentation when making sweet wines
Fermentation can also be stopped prematurely by chilling and/or adding SO2 and then filtering to remove yeast. Gives winemaker greater control over the balance of alcohol and sweetness.
Describe the effect that concentrating grape must has on sweet wines.
Grape must is concentrated by reduction of water content in the grape. This concentrates sugar, acidity and flavours. The increase in acidity and flavours helps keep these wines in balance so sweetness doesn’t become too dominant - key reason why many wines made using this method are very good or outstanding quality.
Because water is depleted, volume of juice from grapes is low. Very sugary is harder to extract during pressing. Adds to the cost of producing these wines, which means they often sell for premium and super-premium prices
List the methods of concentrating grape must
Drying grapes on the vine
Drying grapes off the vine
Development of noble rot
Freezing the grapes
Describe the process of drying grapes on the vine
If grapes left on the vine, they enter stage 4 of ripening where grapes start to shrivel. Water is lost by grape transpiration and sugars concentrate. Flavours in grape continue to develop, giving very ripe flavours.
Wines produced in this way are sometimes labelled as ‘Late Harvest’, Vendanges Tardives and Spatlese
Describe an alternate process of drying grapes while still attached to part of the vine
The cane of the vine is cut or broken off from the vine a short time before harvest. Grapes shrivel more quickly than if still attached to the rest of the vine. This concentrates the sugars, acids and flavours in the grapes.
Reduced hang time lowers, but does not eliminate risk of grey rot and means it is possible to obtain grapes with very high levels of sugar without extra-ripe flavours.
Technique used in Jurancon, south-west France and Australia
Describe the process of drying grapes off the vine
Grapes are picked and then dried for days to months depending on extend of drying required and speed of drying process.
Bunches of grapes laid out to dry in the sun in warm climates (southern Italy, Spain).
Or grapes are dried in temp- and humidity-controlled rooms in cooler climates - gives ability to speed up drying and avoid development of grey rot. Example is Valpolicella.
Drying process causes water to evaporate, making sugars, acids and flavours become more concentrated.
Referred to by Italian term appassimento - wines made this way include Recioto della Valpolicella and Vin Santo
Describe the noble rot method of producing sweet wines
Method involves action of the fungus Botrytis cinerea.
Grapes must be fully ripe before development. Grapes must be grown in a region that provides humid, misty mornings followed by sunny, dry afternoons. Damp conditions in the morning allow rot to develop. Fungus punctures grape skin with microscopic filaments, leaving tiny holes in the skin. Warm sunny afternoon slow the development of rot and cause water to evaporate from the grapes, concentrating its sugars, acids and flavours.
Fungus can modify some aroma compounds and generate distinctive aromas - honey, apricot, citrus zest, ginger and dried fruit aromas.
Describe the freezing grapes on the vine method of producing sweet wines
Healthy grapes left to hang on vine into late autumn and winter. When freezing temps arrive, the water in the grape pulp turns to ice. When grapes picked and pressed, this ice remains in the press and the sugar content of resulting juice is concentrated.
For Canadian Icewine, grapes must be harvested at -8C or below.
Vines need to be winter hardy and have resilient skins that offer protection from disease and can withstand the strain of freeze-thaw cycles.
Describe the common way that winemakers can stop fermentation
Most common way of interrupting fermentation is by chilling to below 10C and/or adding a high dose of SO2 to inhibit yeast. Wine is then racked off its sediment and sterile filtered to ensure 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 wine - covered in D5.
Describe the advantage of using the stopping the fermentation method to produce sweet wines
Advantage of this method is that winemaker has control over the level of sugar in final wine. The earlier fermentation is halted, the higher the level of residual sugar that will remain, but also the lower the alcohol level.
Describe how the blending in a sweetening component method is used to produce sweet wines
Adding a sweetening component is the easiest way of producing a wine with RS. Dry wine is stored until ready to be bottled and the sweetening component is blended in.
Sugar, rectified concentrated grape must (RCGM) and unfermented grape juice (sussreserve) are common sweetening agents.
Unfermented grape juice contributes grape-juice-like character.
RCGM is processed so it just contains the sugar from grapes. It is neutral and smaller amounts required to sweeten wine.
All additions are inexpensive.
Use of sugar not permitted in EU. for PDO wines, unfermented grape juice must come form same wine region as the wine being made.
Describe the benefits of blending in a sweetening component when producing sweet wines
Benefit is that dry wines are less susceptible to spoilage organisms than wines with RS.
Winemaker can trial, measure and add amount of sweetener that is needed to produce the style of wine desired. This method allows a high level of control, enabling high volumes of a consistent product to be made.
Adding a sweetening component will maintain or possibly slightly increase the volume of the final wine and therefore does not add to costs in this way.
