Wine making Flashcards
What is good wine made from?
Good grapes - these can only be grown in suitable weather conditions
What will stop wine from being high quality?
Bad weather conditions
What can spoil a good vintage?
Mistakes
Carelessness
Ineptness
What are the 2 main styles of wine making?
Laissez Faire
Interventionalist
What is Laissez Faire style of wine making?
No intervention (no irrigation, traditional methods, wild yeast fermentation, oak fermentation, no temp control, spontaneous malolactic fermentation)
What is interventionalist style of wine making?
Constant intervention
- irrigation, PC controlled crushing, managed harvest, yeast cultures added, stainless steel fermenting, careful temperature control, controlled malolactic fermentation
How were white grapes formed?
Ancient grapes likely red so mutation = white
What type of grapes is white wine made from?
- its yellow
- Can be made from green or red grapes cleared from their skin and seeds
What is vinification and how does it vary for red and white wine?
Conversion of grape juice to wine
- White is more delicate than red
- Differences at several of the vinification stages
What is crushing in white wine production?
1st stage
- Carried out to make juice accessible but is in contact with skins and seeds - so control of contact required as this affects flavour
- With white grapes there is a gentle crushing = free run
Then remaining pulp is pressed.
When red grapes used, light crushing and straight into press
When is a key decision made about when to destem during white wine production and why?
Crushing
- usually stems left for white grapes (tannin source)
- Stems left on = juices flow more freely and easier to press
What is chaptalisation?
When sugar is added during crushing for white wine and this would increase the alcoholic strength
When are preservatives added during white wine production?
Crushing
- stops oxidation of grape juice.
- Include enzymes which produce SO2 and AST which is a mix of tannins, SO2 and ascorbic acid
What do SO2/AST do to wine?
Too high a concentration can spoil the taste
What type of wines is protection against oxidation important for?
Aromatic white wines
- riesling
- vidal blanc
- gewurztraminer
What types of wine can benefit from the oxidation of the grape juice but what may a negative be?
Non-aromatic -chardonnay -Pinot Grigio - Cayuga However some phenolics (contribute to wine flavour) can be oxidised as well
How can white wine be fined and what effect does this have?
Using PVPP and potassium caseinate to stop astringency in the final wine
What is the cooling stage in white wine production?
2nd stage
Carried out to delay fermentation until after pressing asnd settling
If ambient temperature of must is high, then cool by pumping through must chillers
What is the pressing stage in white wine production?
3rd stage
White grapes are always pressed
Best quality if this is gentle - not breaking pips and stems
What are the 2 types of press used in white wine production?
- Traditionally vertical wooden presses in cylinders with slats for juice
- Modern pneumatic presses used (membrane bladder in slatted cylinder that inflates)
How many times is pressing done in white wine production and why?
Twice
- Must from pressing is added to the free run must
- Must contains juice, stems, skins and seeds
What is settling in white wine production?
4th stage
Juice is drained from the press into settling vats - allow skin, pips, stem settle to the bottom of vat or float so they can be removed
What is racking/raking in white wine production
During settling when the skin, pips and stems settl at the bottom/top of vat allowing them to be removed
Takes 6-12 hrs
What happens to the clean juice after racking during settling?
Transferred into separate vats
Juice can be centrifuged to clarify (excessive process which can strip wine of some desirable components)
If any solids remain they will impart bitterness during fermentation
What is acidification in white wine production?
Prior to fermentation, warm climate must can be acidified if acidity is low
What are the 4 fundamental traits of wine?
Acidity
Alcohol
Sweetness
Tannins
What are acids in wine and why are they important?
Come from the wine grapes, add sourness and tartness.
They preserve wine - bacteria doesn’t like acid
What are the most prevalent types of acid found in wine?
Tartaric
Malic
Citric
Which acid is added in the acidification step of white wine production and what does it do?
Tartaric
Helps fix colour and flavour
Not as astringent as other acids
What does citric acid add to wine?
Helps prevent ferric hazes and add freshness to wine
What does malic acid add to wine?
Seen as harsh and astringent
Why is it more advantageous to do acidification before fermentation?
pH control
retains SO2 effectiveness
What is fermentation in white wine production?
5th stage
- is initiated (if not wild) by the addition of 1-2% cultured yeast to the must.
- Traditionally performed in oak casks (difficult to control temp), modern methods = stainless steel vats with temp control jackets
How long does fermentation of white wine take and at what temperature?
Prolonged fermentation at cool (180C and less) temps ensures complete sugar conversion.
Can either be left in contact with or removed from lees (dead yeast particles) which can add flavour, creaminess and freshness
2-3 weeks
What does sur lie mean on bottles of wine?
Left in contact with lees
Is there natural yeast in wine? If so what does it do?
Yes
Causes fermentation
- some are considered as part of personality of vineyard and give wine personality (terroir)
- Modern method removes natural yeast using SO2/flash pasteurisation
What happens in modern wine once natural yeast is removed?
Cultured yeast is added suitable to fermentation temperature used.
What happens regarding yeast once fermentation is underway and why?
Generous amounts of active yeast added
- no longer any oxidation problems
What are the main sugars in ripe grapes?
glucose
fructose
What are the main sugars in uripe grapes?
Glucose
overripe = fructose
What are the products of wine yeast?
Ethanol
Co2
glycerol
How much glycerol is produced by wine yeast and what does it provide?
2-11g/L
Adds sweetness and fullness to wine
How is the amount of co2 in wine determined?
By fermentation temperature
How do home winemakers degas their wines?
BY agitation or the application of vacuum.
Racking and other processes will generally remove bubbles from commercial wines prior to bottling
How do commercial winemakers measure co2 and why?
They may add more co2 to stop oxidation and bacterial contamination of their product.
What is malolactic fermentation wrt white wine production?
Generally performed as a secondary fermentation to soften astringent acidic flavours and to add complexity - can be natural or artificial.
Converts the harsh malic acid to softer lactic acid using various bacteria- for cold climate wines.
CO2 produced as a by product of this process
What type of white wine is malolactic fermentation prevented?
In white wines from warmer climates which have higher sugars, more fruit flavours and less acid.
Process removes yeast and proteins needed for bacterial action
What might be necessary after malolactic fermentation?
de or re acidification.
Calcium carbonate is added to remove tartaric acid (cooler climates)
Acidex is used to remove malic.
In warmer climates can add natural acids - which can be from stems and oak.
What is maturing in the production of white wine?
Clarification by filtration, filtering or fining with bentonite clay (precipitates, yeasts, proteins and grape skin particles to vat bottom)
This prevents unwanted malolactic ferment or further yeast activity.
Wine gains stability but some clarification methods believed to be aggressive and lead to flavour loss
Can have racking
What is cold clarification in white wine production ?
Performed at 40 C to remove tartaric acid (which crystallizes out) easiest in steel tanks. If in wooden casks need cold cellars. Can be bottled at this point or matured in oak casks
What does cask maturing in new oak do in the production of white wine?
overpowering flavours to subtle wines but adds depth and complexity to others.
older barrels give more moderate flavours
What happens in terms of flavour to cask fermented white wine?
Nutty and roasted flavours as wooden barrels breath and some oxidation in fermentation
What happens in terms of cask matured white wine?
Picks up vanilla flavours and tannins - get more of oak flavours
What flavours does barrel oak aging add to white wine?
Vanilla, spicy, buttery, butterscotch and sometimes smoky flavours - also a source of tannins.
Can be other woods but mostly oak used.
Only for white wines of strong character and constitutions.
Light white wines will not take on wood flavours