RS wines and no/low-alc wines Flashcards
What are the three ways to produce wines with residual sugar?
- concentrating sugar in grape must
- stopping ferm before dryness
- blending in a sweetening component
What are the four ways of concentrating the grape must?
- drying grapes on the vine
- drying grapes off the vine
- noble rot
- freezing grapes on the vine
What are two keys reason why wines with RS made from concentrating the must tend to be very good or outstanding?
- Concentrating the must also concentrates the other components (like acidity and aromas)
- Other aromas are introduced (e.g., ripe fruit for drying on vine, dried fruit for drying off vine, or honey/apricot/ginger/etc. for noble rot)
How can the winemaker control the level of RS when fermenting grape must that has been concentrated?
By stopping ferm early
Why are wines with RS created by concentrating the must expensive?
- volume of juice from grapes is low
- sugary pulp is hard to extract during pressing
What are two major ways of drying grapes on the vine?
- leaving grapes on the vine
- cutting the cane shortly before harvest
What happens to grapes when they are left on the vine?
- no more water or sugar transported in
- water lost by grape transpiration, concentrating sugars
- extra-ripe aromas develop
What happens to grapes when the cane is cut just before harvest?
- grapes shrivel more quickly than if attached to the vine (concentrating more quickly)
- extra-ripe aromas don’t have time to develop
- risk of grey rot reduced (because of reduced hang time)
What two places is the technique of cutting the cane just before harvest used?
- Juracon
- Australia
How can grapes be dried off the vine, with examples?
- in the sun (southern Italy or Spain)
- in climate controlled room (in Valpolicella)
What is another name for drying off the vine?
appassimento
What are the two requirements for noble rot?
- the grapes must be fully ripe before the development of rot
- there must be humid/misty mornings followed by sunny, dry afternoons
How does noble rot lead to concentration?
- The fungus punctures the grape skins with microscopic filaments, leaving tiny holes on the skins
- Warm afternoons (i) slow the development of the rot and (ii) cause water to evaporate, concentrating everything left
What are five reasons why wines from noble rot are expensive?
- Often requires multiple pickings by hand, as noble rot on grapes is never uniform
- Volume of juice is low (as water has evaporated)
- In some regions, noble rot does not happen every year–i.e., they are scarce
- If conditions are too damp, the fungus will develop too rapidly, resulting in loss of grapes
- The grapes are not easy to process in the winery
What are two reasons why grapes with noble rot are difficult to process in the winery?
- The fungus produces laccase, which oxidizes a number of wine components and resistant to SO2
- High sugar must difficult to press, clarify, and ferment
What are four ways to deal with laccase produced by noble rot?
- Chilling the must
- High doses of SO2
- Use of inert gases
- Heated maceration (both flash détente and thermovinification)
When are wines from noble rot matured in oak (old or new)?
Especially when a neutral variety (like Semillon) is used. Not usually an aromatic variety (like Riesling).
What are three requirements for vines used to make Icewine?
- winter hardy
- grapes with resilient skins that can protect against disease and freeze-thaw cycles
What are typical grapes used for Icewine?
Most popular:
* Riesling
* Vidal
Occasionally black grapes, like Cab Franc
What is a requirement for Canadian Icewine?
Grapes have to be picked at -8 C or below
What are five conditions of Icewine that lead to premium or super premium prices?
- only a few regions can produce it
- picked late in winter (e.g., late January), as freeze-thaw cycles are thought to be important
- yield is low (as water is lost)
- considerable risk that unpicked grapes will be infected by disease or eaten by birds (netting is an important cost)
What is an attempt to mimic Icewine?
Cryoextraction– Pick grapes at normal time in autumn, and put them in a freezer. Much cheaper than Icewine, as much less risky.
- What is the advantage of stopping ferm to leave RS?
- What is a disadvantage?
- Winemaker can control the level of sugar.
- As it does not concentrate the must, it tends not to reach outstanding levels (an exception is some fortified wines, given the extended ageing process)
What is the most common way to stop ferm to leave RS?
- Chill to below 10 C and/or add high dose of SO2
- Rack wine
- Sterile filtered
What is a less common way to stop ferm to leave RS?
Fortification, which radically changes nature of wine
What are four advantages to blending in sweetening component to making a wine with RS?
- Easiest way to make a wine with RS
- Can store the unsweetened dry wine until it is ready for bottling, which reduces risk of spoilage
- High level of control, enabling high volumes with consistent product
- Maintains or slightly increases volume (as opposed to concentrating the must)
What are three common sweetening components for blending with wine to make a wine with RS?
- Sugar
- rectified concentrated grape must (RCGM) - processed so it is neutral sugar
- unfermented grape juice (Süssreserve)
What are two EU rules regarding addition of a sweetening component to make a wine with RS?
- Sugar not permitted
- For PDO wines, the unferm grape juice must come from the same region as the wine
What is the early method for removing alc and what are two problems with it?
Heat-induced evaporation (i.e., boiling)
Unfortunately, heating to 78 C caused:
* undesirable cooked aromas
* loss of essential volatile aroma compounds
What are the three primary techniques for reducing or removing alc from wine?
- membrane separation
- vacuum distillation
- spinning cone technology
the last two use “thermal distillation”
What are 7 factors to be considered in pre-ferm options for reducing alc?
- variety
- site selection: cooler
- vineyard management
- timing of harvest: harvested early
- blending
- dilution of must
- filtration of must
What varieties are less or more suitable to low-alc wines, and why?
- Less suitable: high-sugar varieties, like Grenache and Zinfandel
- More suitable: highly aromatic varieties, like Sauv Blanc and Riesling (as their varietal character shines in spite of loss)
What is a problem with picking grapes early, esp for reds?
Aroma and tannin ripeness may not have been achieved
How can pre-ferm blending be useful in creating a low alc wine?
- Blending of less ripe with riper grapes
- Blending of different varieties to boost color, aroma, tannins
How can must be diluted, and what is a problem with it, and is it commonly used?
- Add water
- Prohibited in the EU (and elsewhere)
- Not common for low alc wines
How can filtration of the must be used to assist in creating a low alc wine? What is a drawback?
- Use a membrane separation technique, like reverse osmosis, to remove sugar
- Unfortunately, can also remove color and volatile aroma compounds
- What are the most popular pre-ferm options for making low alc wine in the EU?
- Outside the EU?
- EU: early harvesting and blending
- Outside of EU (esp USA and Australia): diluting must
What are two methods to lower alc during ferm?
- Yeast strains
- Interrupted ferm
- What are two examples of use of yeast strains that can lower alc?
- What is a drawback of their use
- Metschnikowia pulcherrima can produce wine with reduced ethanol concentration when sequentially inoculated with Saccharomyces cerevisiae
- genetically modified yeast strains can also lower the amount of alcohol produced during fermentation
Can have negative effect on the wine
What are two impacts of lowering alc by interrupting ferm?
- RS will be left, which will change the style
- wine will need to be stabilized before bottling
Describe the use of reverse osmosis for removing alc from wine
membrane separation technique
* removes a flavorless permeate of alcohol and water
* permeate distilled to remove alcohol
* watery permeate is then blended back to recreate the wine
What is the most common high-tech option for removing alc from wine and why?
reverse osmosis, as:
* it is the most economically viable
* mobile reverse osmosis available in many countries
Describe vacuum distillation for removing alc from wine
- wine placed in vacuum, lowering boiling point of alc to 48 C
- some lost volatile aroma compounds can be captured and added back
Describe spinning cone technology for removing alc from wine
- a thermal distillation device that spreads the wine out to a very thin film
- volatile aroma compounds are extracted from the wine
- then the alcohol is removed
- then aroma compounds are blended back into wine
When is spinning cone technology viable?
only with large volumes of wine
What are two drawbacks of reverse osmosis?
- each pass removes only 1.5% abv, so multiple passes required (and it is only really suitable to minor adjustments)
- each pass involves considerable waste
What are 6 types of changes that generally happen when alc is removed from wine?
- volatile compounds lost
- phenolic compounds (like tannins and anthocyanins): can become more concentrated, esp in reds
- structural elements
- stability (need to stabilize, like pasteurization or adding a preservative like DMDC)
- shelf life
- cost
What is the typical change to structural elements with alc is removed?
- less body
- higher astringency and acidity (due to concentration)
- less aromatic intensity
What is the shelf life of no or low alc wines?
- 2 years in glass bottles
- 1 year if canned
What are the cost components of no or low alc wine?
- need for specialized equipment (costly)
- high yield loss (15-30%)
however, the alc extracted may be sold separately
What are 4 common post-dealc adjustments?
- sugar
- flavor enhancements
- tannins
- glycerol
How and why would sugar be added post-dealc?
- RCGM
- Correct weigh and mouthfeel by mimicking textural feel of alc
- Help balance out increased perception of acidity and astringency
What flavor enhancements might be added post-dealc?
Grape-derived, natural flavourings, made by flavour houses such as Dallant, Essencia, and Laffort
Why would tannins be added post-dealc, and how?
If tannins have been diluted pre-fermentation, for example by adding water to the must, powder or liquid tannins may be added to improve texture and flavor
Why would glycerol be added post-dealc?
Because it is viscous, used to boost body
How can a wine below 5.5% abv be labeled?
not wine, but a wine-based beverage
What are the abv levels for labeling low and no alc wines in the UK?
- Low alcohol –1.2% abv or less
- Non-alcoholic – 0.5% abv or less
- Alcohol free – 0.05% abv or less
