Flashcards in Vini 2: Fermentation Deck (73)
Equation for fermentation:
C6H1206 -> 2C2H5OH +2CO2 + energy
Sugar needed to create each 1% alcohol by volume:
Sugar preferred by most yeasts:
Main by-product of fermentation:
Glycerol (glycerine) - colourless, viscous.
Other woods used as vessels:
Chestnut, cherry, acacia and walnut.
Main difference between wood and stainless steel:
Wood retains heat more readily.
Lining for cement tanks:
Epoxy resin, tiles, wax or glass.
Percentage abv. by which Saccharomyces yeasts will normally dominate:
French for starter culture:
Le pied de cuve
Why use a starter culture?
To allow Saccharomyces to dominate immediately, to start fermentation quickly and to kill off other indigenous microflora. Slow fermentation is risky.
Measuring must density:
Keeping fermentation rate uniform is key. France: relative density/Baumé. Aus, NZ, USA: Brix/Balling. Germany, Switzerland: Oechsle (hydrometer). Italy: Babo. Austria: KMW.
Substance responsible for banana/pear drop aroma at low temps.:
Substance responsible for high levels of VA at low temps.:
Pumping over, punching down and rack and return in French:
Le remontage, le pigeage et le délestage.
Level of unfermentable sugars even in driest wines:
Up to 2 g/L
Getting a stuck fermentation started again:
Increasing levels of nutrients rich in nitrogen: di-ammonium phosphate (DAP) or thiamine (vitamin B). Oxygenation early on is also key.
Yeasts deprived of nitrogen:
They break down amino acids releasing hydrogen sulphide (H2S).
Typical fermentation temp. for white wine:
Between 14-20 deg, though can reach up to 25 in small barrels.
Cooling of newly fermented white wine:
Down to 12 deg to aid yeast settling.
Addition of SO2 to avoid MLF in whites:
Temp. of white wine if MLF desired:
17-20 deg. Lees stirred once a week.
Reduced hydrogen sulphide can produce...
Mercaptans - onion-smelling substance.
Treating severely reduced wine:
Pass through a copper pipe or add copper sulphate.
Aim of using rollers for bâtonnage:
Stirring in less oxygen.
The three rosé winemaking techniques:
Drawing-off/saignée, direct pressing and blending.
Most common. Destemmed, crushed, sulphited grapes. Mild colour, treated as white must. Cool temps. with no oxygen. MLF blocked. Young consumption.
Direct press of freshly harvested grapes. Care taken to reduce tannin extracted. Pale colour.
Rosé Champagne and New World rosés. Not allowed in EU.
Two kinds of phenolic compounds:
Non-flavonoids (simpler) and flavonoids (catechins and anthocyanins).