WINEMAKING | DESCRIBE KEY PROCESSES Flashcards
Oak Vessels
Allow small levels of oxidation
Extra tannin and flavour from oak
Smaller vessels = more of the wine is in contact with the oak
Age = effects of the oak diminish with each use
Crushing
Breaks the skins of the grapes and ‘liberates’ free run juice without damaging the seeds.
Pneumatic pressing
Inflatable rubber tube within a perforated, horizontal stainless steel cylinder.
Apply pressure over a larger area in a controlled way.
Can be closed to minimise oxygen contact
Rectified Concentrated Grape Must (RCGM)
Added to increase sugar levels, in cases of the must weight in the juice being too low, either before or during fermentation.
Raises the alcohol level of final wine.
Removing water from juice
To increase sugar levels, in cases of the must weight in the juice being too low, before fermentation.
Raises the alcohol level of final wine.
But concentrates everything (tannin, acid, flavour and faults).
Acidification
Addition of tartaric acid in powdered form.
Deacidification
Excess acid neutralised by the addition of an alkali.
Malolactic Fermentation (MLF)
After alcoholic fermentation.
Lactic acid bacteria convert tart malic grape acid into softer lactic acids.
Softens and reduces acidity + creates buttery flavours.
Encouraged by raising the temperature of a wine and not adding SO2.
Avoided by cool temperatures, adding SO2, or filtering out bacteria.
Lees
Yeast die and form a sediment of lees (dead yeast cells and grape fragments).
Dead yeast cells begin to break down and release chemical compounds into the wine.
Gross lees (large particles) fall to the bottom and are ‘racked off’ to prevent unpleasant aromas to develop.
Fine lees (smaller particles) are removed gradually depending on desired flavour.
The longer the wine spends in contact with the dead yeast cells (fine lees) the more intense the bread and biscuit flavours produced + the richer the texture.
Sedimentation
Part of the clarification process to produce a perfectly clear wine.
After gross lees have settled the wine is slowly and gently pumped into a different vessel (racking).
Process is repeated (sediment settles, wine is racked).
Relies on gravity but can be sped up by a centrifuge.
Fining
Haze/deposits appear in a wine when constituents clump together over time.
Fining speeds this up so that the particles can be removed before bottling.
Involves adding a fining agent that forms bonds with certain wine constituents and causes visible clumps to form.
This is filtered out.
Depth Filtration
Physically removes particles from a wine as it is passed through thick layers of material. Solid parts become trapped.
Can be filtered after fermentation and during maturation to remove gross and fine lees quickly.
Also filtered prior to bottling.
Surface Filtration (Sterile filtration)
Solid particles are trapped on the surface of the filter as the wine flows through ‘pores’.
Generally used for wines that have already been depth filtered.
Sterile filtration is when ‘pores’. are small enough to trap yeast and bacteria.
Tartrate Stability
Tartaric acid forms crystals called tartrates. Harmless and flavourless but can spoil the appearance.
Either: long maturation in cool cellars
or
Chilling the wine down to 0 degrees for a short period, then filtering.
Microbiological Stability
Yeast and bacteria can spoil a wine.
Fortified wines - alcohol too high
MLF wines - quite resistant due to alcohol, acidity and lack of nutrients
Non-MLF wines - SO2 and sterile filtered
Oxygen Stability
Wine can oxidise and lose fresh fruit aromas.
Minimised by keeping avoiding exposure to oxygen and keeping SO2 levels topped up.
Pre-fermentation extraction
Once the fruit has been crushed, the grapes are left to macerate for a period at a low temperatures before fermentation.
Extracts colour and flavour compounds. Tannins are more soluble in alcoholic solutions and are less readily extracted at this point.
Temperature during fermentation
Red wine - 20 to 32 degrees
White wine - 12 to 22 degrees
Carbonic maceration
Whole uncrushed bunches placed into vats
Vats filled with CO2 to remove all oxygen.
Fermentation starts in the grapes and the grapes split at 2% alcohol.
Split grapes release their juice.
Grapes pressed to separate the skins.
Ambient yeast complete fermentation off the skins.
Semi-carbonic maceration
Whole bunches placed in vat
Fruit at the bottom of the tank is crushed by the weight of the fruit above it.
Grapes split and release juice.
Ambient yeast ferment the juice at the bottom of the tank
CO2 forms and blankets the rest of the fruit in the vat
Remaining berries undergo carbonic maceration.
Whole bunches with crushed fruit fermentation
Mix whole bunches with crushed fruit in the fermenting vessel.
Whole bunches aren’t blanketed in CO2, but the crushed grapes protects them from oxygen and intracellular fermentation occurs.
Whole bunches crushed as the cap is punched down.
Direct pressing
Rose winemaking
Black grapes are crushed and pressed to extract some colour from the skins
Care should be taken not too extract too much tannin
Fermentation takes place off skins in cool fermentation conditions.
Short maceration
Rose winemaking
Black grapes are crushed and allowed to macerate to extract flavour and colour (duration depends on required colour and tannin)
Free juice will be drained off the skins and fermented at cool temperature
Second alcoholic fermentation
Sparkling - traditional method
Liqueur de tirage is added (wine, sugar, yeast) to the bottle.
Bottle is sealed.
Bottles are stacked horizontally and cool, constant temperatures .
Slow fermentation.
Raises alcohol by 1.2-1.3% abv and CO2 created dissolves into the wine making it sparkling.
Yeast Autolysis
Sparkling - traditional method
After second fermentation the yeast dies and forms sediment of lees in the bottle.
Dead yeast cells break down releasing chemical compounds into the wine.
Add bread, biscuit, toasty notes.
Four to five years. After which lees keep the wine fresh.
Riddling
Sparkling - traditional method
After maturation the lees sediment is removed by moving the bottle very slowly from horizontal to vertical.
Yeast sediment is dislodged and collects in the neck.
Disgorgement
Sparkling - traditional method
Upturned bottle placed into a very cold brine solution to freeze the wine in the neck.
Crown cap removed and the pressure from the dissolved CO2 ejects the frozen wine taking the sediment with it.
Liqueur d’expédition
Sparkling - traditional method
Mixture of wine and sugar.
Often known as dosage.
Used to balance the acidity and helps with flavour/ house style.
Transfer method
Sparkling
Same as traditional method but at the point of riddling the entire contents of the bottle is disgorged into a sealed tank.
Wine is filtered, Liqueur d’expédition added and wine is rebottled.
Look for ‘bottle-fermented’
Asti method
Sparkling
fermentation takes place in pressurised tanks.
Initially CO2 is allowed to escape. Part way through the tank is sealed so CO2 is retained.
Ferment continues until 7% abv.
Fermentation stopped early, by chilling the wine, before all the sugars are fermented.
Wine is filtered to remove the yeast and wine is bottled immediately.
