Lecture 17: Aging

Reading Assignment: Text, Chapter 10, pages

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

[Compound] Different reactions will occur at different rates. A steady state value may or may not be reached.

Aging Variables Time 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 R O O + H 2 O 2 H 2 O 2 + H 3 C-CH 2 OH H 3 C-CH + 2H 2 O 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 (N 2, CO 2 ) Limit headspace –Top-off barrels Monitor saturations

Air Saturations One “saturation” = 6 mL O 2 /L Capacity for O 2 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

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

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

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”