Lecture 17: Aging. Reading Assignment: Text, Chapter 10, pages 382-415

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”