Lecture 17:
Aging
Reading Assignment:
Text, Chapter 10, pages 382-415
AGING:
As a means of achieving stability
Aging: To Achieve Stability
• To allow reactions that are going to happen to occur before bottling– Polymerization of tannin– Polymerization of pigment– Stabilization of color– Loss of volatile esters
Polymerization
AGING:
To correct a problem
Aging: To Correct a Problem
• Allow “negatives” to disappear– Volatilization– Hydrolysis– Oxidation– Precipitation– Other Chemical reactions
AGING:
As stylistic
Aging: As Stylistic
• “Oxidative” versus “reductive” aging• Allow formation of new characters• Addition of new characters from
cooperage• Addition of new characters from yeast
lees/autolysis• Increase/Decrease complexity depends
upon varietal/composition
Aging Variables
• Time
Time
Time
[Co
mp
oun
d]
Different reactions will occur at different rates.
A steady state value may or may not be reached.
Aging Variables
• Time
• Temperature
Temperature
Faster at Higher Temperature
Slower at Higher Temperature
Temperature Independent
Aging Variables
• Time
• Temperature
• Oxygen
Oxygen Exposure Leads To:• Polymerization of phenolics
– Good: softens astringency– Bad: too much loss of color
• Browning/Pinking– May be desirable or neutral (reds)– May be undesirable (whites)
• Acetaldehyde• Stabilized color• Oxidized flavors
Acetaldehyde Formation
R
OH
OH
+ 02
R
O
O
+ H2O2
H2O2 + H3C-CH2
OHH3C-CH + 2H2O
O
Stabilization of Color
Reaction of oxygen with anthocyanins leads to polymerization and stabilization of red color.
Control of Oxygen Exposure
• Use inert gas flush (N2, CO2)
• Limit headspace– Top-off barrels
• Monitor saturations
Air Saturations
• One “saturation” = 6 mL O2/L• Capacity for O2 is dependent upon the
phenolic composition• A single saturation occurs with each air
exposure– Racking– Fining– Filtration– Centrifugation– Movement to tank/barrel
Aging Variables
• Time
• Temperature
• Oxygen
• Cooperage
Cooperage
• Glass
• Stainless steel
• Wood
Wood Variables
• Source of wood– French– American– Other
• Aging of wood• Toasting level• Number of times it has been used• Barrel, Staves, Chips
Wood
• Allows limited oxygen exposure
• Allows some evaporative loss
• Adds nuances
• Surface area versus volume of wine important
Aging Variables
• Time
• Temperature
• Oxygen
• Cooperage
• Yeast lees
Yeast Lees
• Yeast autolysis adds flavors– Long chain esters– Stimulates Malolactic Fermentation
• Activity of yeast enzymes continues post-lysis
• Impacts mouth feel
Aging Variables
• Time
• Temperature
• Oxygen
• Cooperage
• Yeast lees
• pH
pH
• Affects rates of some reactions
• Phenolic oxidations 9 times faster at pH 4.0 versus pH 3.0
• Affects microbial persistence and activity
Aging Variables
• Time
• Temperature
• Oxygen
• Cooperage
• Yeast lees
• pH
• Catalysts
Catalysts
• Metal ions can increase rates of some chemical reactions
Aging Variables
• Time• Temperature• Oxygen• Cooperage• Yeast lees• pH• Catalysts• Chemical composition of wine
Chemical Composition of Wine
It’s what in there that counts!
The 5 Goals of Post-Fermentation Operations:
5. PACKAGING
Packaging
• Bottling– Sterile– Non-sterile
• Closure– Cork– Synthetic cork– Screw cap– “Bag-in-box”