Chapters 7-10 Winemaking Flashcards
What 2 acids are present in the pulp of a grape?
Tartaric acid
Malic acid
What methods are used in a winery to limit oxidation during the winemaking process?
Antioxidants - sulfur dioxide
Night picking - effect of O2 is reduced as chemical reactions occur slower in cool temperatures
Grapes chilled until they reach the winery
Winery equipment filled with CO2 or nitrogen before use
What name is given to the process of winemaking with no oxidation?
Anaerobic or protective winemaking
What vessels are used to protect wine from oxidation during maturation?
Stainless steel inert, airtight tanks or vats
Cement tanks lined with epoxy resin
What changes occur to red wines that are matured in oak?
Small amounts of oxidation Softer tannins Primary fruit flavours fade Tertiary flavours (leather, earth) develop Red wines become paler
What are 3 pronounced tertiary flavours (normally seen in sherry or port) that are assocoated with oxidation?
Caramel
Toffee
Nuts
What has happened to a wine that is ‘oxidised’?
Too much exposure to oxygen
Fresh fruit flavours are lost and wine smells stale.
In an extreme case, bacteria will use oxygen to change the wine into vinegar
What 2 purposes is sulfur dioxide used for in a winery?
Antioxidant
Antiseptic
What effect do oak tannins have on a wine?
Oak tannins give more structure to both red and white wines, increasing textural complexity
What 4 aromas and flavours can oak maturation add to a wine
Toast
Vanilla
Smoke
Cloves
What 4 features of an oak barrel impact the effect it will have on a wine?
Species/origin of oak (European vs USA)
Size
Production of barrel - toasting
Age - how many times its been used
What are 2 alternatives to oak barrels that will impart oak aromas and tannins?
Oak planks (staves) Oak chips
As freshly picked grapes arrive at the winery, what is the first step in grape processing?
A first dose of sulfur dioxide is added
If a premium wine, they will be individually checked to eliminate unripe or rotten grapes
What will grape seeds add to a wine if inadvertently crushed?
Bitter oils and tannins
Unpleasantly astringent and bitter
What is ‘must’?
Grape juice
What can be added to wine to increase sugar levels?
Rectified Concentrated Grape Must (RCGM)
What is chaptalisation?
The addition of sugar from sources other than grapes eg. sugar beet
What can be added to wine to increase acid levels?
Tartaric acid in powder form
What can be added to wine to decrease acid levels?
Alkali
What is the name of the yeast that is responsible for the majority of wine fermentation?
Saccharomyces cerevisiae
Sugar + yeast = ?
Alcohol + CO2 + heat + flavour compounds
Alcohol fermentation will not start if the temperature is below what?
5°C
At what maximum temperature will alcohol fermentation stop?
35°C
What are 3 ways of either killing or removing yeast in order to stop fermentation?
Adding sulfur dioxide
Adding grape spirit
Chilling below 5°C and filtering
What are 2 ways in which a winemaker can control fermentation?
Choice of yeast
Temperature management
What is malolactic fermentation (MLF)?
Occurs after alcohol fermentation finished
Lactic acid bacteria + malic grape acid = lactic acid
What effect does MLF have on wine?
Softens and reduces acidity
Creating buttery flavours
How does a winemaker encourage MLF?
After alcohol fermentation
Increases the temperature of the wine
Does not add sulfur dioxide
What are ‘lees’?
Dead yeast cells and grape fragments
What are the 6 constituents that make up a bottle of wine?
Water Ethanol Tannins & Colour Aroma & Flavour Compounds Sugars Acids
What 3 qualities must a wine have in order to age well?
Sufficient tannins
Sufficient acid and/or alcohol
Flavours that will develop in an interesting way
What are 3 methods of clarification?
Sedimentation
Fining
Filtration
What is ‘racking’?
A process of removing the lees from a wine Once the lees have settled in a deposit the wine is gently pumped to a different vessel.
Relies on gravity
What is ‘fining’?
The addition of a fining agent.
This agent forms bonds with certain wine constituents and causes clumps to appear which can be filtered out
What are the 2 types of filtration?
Depth filtration (gross lees) Surface/sterile filtration (yeast, bacteria)
What are 3 important areas that require stabilisation?
Tartrate stabilisation
Microbiological stability
Oxygen Stability
What are tartrate crystals?
Clear (white wine) or purple (red wine) crystals formed due to tartaric acid being less soluble in wine than in grape juice
Harmless and flavourless
How are tartrate crystals removed prior to bottling?
Chilling wine down to below 0°C for a short time and filtering
What wines are not at risk of microbiological contamination?
Fortified wines because of the high level of alcohol
How can a winemaker avoid microbiological contamination?
Keep winery equipment completely clean
Sterile filter wine
Sulfur dioxide
How can a winemaker ensure oxygen stability?
Avoiding exposure to oxygen
Keeping sulfur dioxide levels topped up
Flushing bottles with either CO2 or nitrogen
In white winemaking, grapes are crushed, pressed & skins removed before alcoholic fermentation. What other processes can happen before fermentation?
Sort
Destem
Allow skin contact - few hours
Clarification
What is the optimum temperature for white wine alcoholic fermentation?
12°C - 22°C
When making white wine from aromatic grape varieties what winemaking choices are important to maintain fruit and floral aromas?
Sulfur dioxide monitoring
Crushed fruit or whole bunches in the press
Clarification prior to fermentation (so fruit flavours not masked by anything in juice)
Inert vessel fermentation (no interference with pure fruit character)
Very little post fermentation winemaking (MLF avoided, SO2 added)
Bottle quickly
What are 5 aromatic white grape varieties?
Riesling Sauvignon Blanc Muscat Gewurztraminer Torrontés
What are 2 less aromatic white grape varieties?
Chardonnay
Pinot Gris/Grigio
When making white wine from less aromatic grape varieties what winemaking choices are important?
Depends on style they want to produce
Crushed fruit or whole bunches in the press
Clarification prior to fermentation
Fermentation may occur in range of vessels
Possible barrel maturation = oxidation
MLF or lees contact
True or False?
Malolactic fermentation is standard practice in red wine making
True
In red wine making, what is the purpose of low temperature maceration prior to fermentation?
Referred to as cold maceration or cold soaking
Extracts colour and flavour compounds without tannins
What is the optimum temperature for red wine alcoholic fermentation?
20°C - 32°C
In red wine making, what is the ‘cap’?
A thick mass of pulp and skins that accumulates on the top of fermenting red wine
What are 4 cap management techniques?
Punching down
Pumping over
Rack and return
Rotary fermenters
In red wine making, what is the purpose of maceration after the fermentation?
Further extraction of tannin, if desirable
Can help create a smoother tannin structure
What are the names of the 2 wines that are produced after fermentation?
Free run wine Press wine (may be divided into press fractions)
In red wine making, what is whole bunch fermentation?
Whole bunches of uncrushed grapes are added into the fermentation.
Creates an oxygen free environment for the uncrushed fruit
Berries create alcohol in their cells without any yeast = intracellular fermentation
How does whole bunch fermentation affect the taste of a wine?
A range of distinctive fruity aromas are produced inside the berry which gives wines made in this way unique qualities
What are the 3 forms of whole bunch fermentation?
Carbonic maceration
Semi-carbonic maceration
Whole bunches with crushed fruit
What is the process of carbonic maceration?
Only whole uncrushed bunches
Put in vats filled with CO2
Intracellular fermentation begins
Once alcohol at 2% skins split, juice released
Grapes pressed - juice & skins separated
Yeast completes fermentation off skins
What are the flavour characteristics of a wine that has been produced using carbonic fermentation?
Colour but little tannins from skins
Soft, full of fruit
Notes of kirsch, banana, bubble gum and cinnamon
What is the process of semi-carbonic maceration?
Vats filled with whole bunches (No CO2)
Grapes at the bottom crushed under weight and juice released
Ambient yeast starts fermentation
Vat fills with CO
Remaining intact berries undergo carbonic maceration
Grapes compressed
Yeast completes fermentation off skins
What is the process of whole bunch fermentation with crushed fruit?
Whole bunches added to crushed grapes in fermenting vessel
No CO2 but largely submerged so kept away from O2
Intracellular fermentation takes place
Whole bunches crushed during fermentation as cap is regularly punched down
What environmental conditions encourage Noble Rot?
Humid misty morning followed by sunny afternoons in the Autumn
How does Noble Rot occur?
Damp conditions in the morning allow rot to form on fully ripened grapes
Fungus punctures the grape skin with microscopic filaments leaving little holes
Warm sunny afternoons slow rot, and promote water evaporation from the grape
What are the flavour characteristics of a wine affected by Noble Rot?
Honey
Apricot
Citrus Zest
Dried fruit aromas
Name 4 sweet wines that are produced with Noble Rot affected grapes
Sauternes
Tokaji
Beerenauslesen
Trockenbeerenauslesen
What is the name of the fungus responsible for Noble Rot?
Botrytis cinerea (Also responsible for Grey Rot)
What are 6 ways in which the sugar levels in a wine can be increased?
Stopping the fermentation Adding a sweetening component Noble Rot Drying grapes on the vine Drying grapes after picking Freezing grapes on the vine
What are 3 ways of stopping fermentation while sugar is still present?
Fortification
Adding a high dose of SO2
Chilling
What is ‘passerillage’?
Drying grapes on the vine
Name an appellation which uses the technique of drying grapes after picking
Recioto della Valpolicella
What is the process of making Eiswein?
Healthy grapes are left on vine into Winter
With freezing temperatures the water in the grape pulp turns to ice
When the grapes are picked and pressed, the ice remains in the press and the sugar content in the juice is increased
