Martin Day

Use of early oxygen exposure to modify style in white and red wines

There’s nothing new in Science

both lab-scale and pilot winery-scale

Why consider oxygen?

Oxygen content of juice at inoculation can vary due to: Protection during preparation Time to inoculation

Oxygen exposure during ferment can vary due to: Winery practices Fermentation type Winery hardware Active aeration

Two key nutrient limitations during fermentation: Nitrogen Oxygen

A driver of yeast metabolic activity: Membrane synthesis Redox balancing Biomass production

How to assess early O2 exposure?

Oxidation occurs just as the berry is crushed open

Whole bunch pressing in a tank press with inert gas

Does protecting must/juice after pressing have an effect?

What about after fermentationHandlingUni Adelaide

PressingBucher “Inertys”

Grape pickingBarossa

Hand-picked CHA grapes

(Barossa)

Aerobic press mode (‘normal’)

OxidativeReductive (‘normal’)

Inert press mode

Oxidative Reductive (‘normal’)

Aero Ox (AO) Aero Red (AR) Inert Ox (IO) Inert Red (IR)

+ oxygen

12 tonnes Chardonnay grapes; four treatments in triplicate; 500 L ferments

DO = 3.3% air sat (±2.1) or ~370 ppb (±230)

Time

Normal modeInert mode

DO

80% air sat

Flushing

Early outcomes: Somers' white wine phenolic indices

Total Phenolics [A280 – 4]

InertRed InertOx AeroRed AeroOx0

2

4

6

AU

A B

C C

Total HCA [A320 – 1.4]a

b

c c

Total flav [(A280-4) – 2/3(A320-1.4)]

α α β β

Group differences at P = 0.01

Juice after cold settling

PCA – volatile and non-volatile compounds

INERT

amino acids

Bad eggfruity

Fusel, spiritous

Cooked potato

Cheese, sweaty*

Citrus, tropical *

Struck flint*

Sweaty, tropical

Phenolics

chroma

Banana, fruity

Fusel, spiritous

Green apple

Honey, floral*

Rancid, harshAA(Gln)

AEROBIC OXIDATIVE

REDUCTIVE

Green, grass

PC-2

Sweet-perfume

PC-1

Chemical ‘attributes’ in bold are present > OAV

Oxidation compounds

5

10

15

20Ph

enyl

ace t

alde

hyde

(µg/

L )

0

10

20

30

40

benz

alde

hyde

(µg/

L )

300

400

500

600

met

hion

ol(µ

g/L )

Honey, floral ** Cooked potato

Bitter almond

Aroma compounds: inert vs. aerobic pressing

90

100

110

120

130Ethyl propanoate (mg/L)

500

600

700

Ethyl butanoate** (mg/L)

5.0

5.5

6.0

6.5

7.02&3-methylbutyl acetate (mg/L)

17

18

19

20

21 2-methy propanol (mg/L)

800

1000

1200

Butanol (mg/L)

1000

1500

2000

Ethyl hexanoate** (mg/L)

Sensoryimpact?

1.20

1.40

1.60

1.80

2.00

2.20

Confection

3.40

3.50

3.60

3.70

3.80

Overall Fruit Aroma2.35

2.45

2.55

2.65

2.75

Yellow Col. Int.

1.70

1.90

2.10

2.30

2.50

Floral

3.15

3.25

3.35

3.45

3.55

Citrus flavour

4.30

4.40

4.50

4.60

4.70

4.80

Acid

Laboratory-scale fermentation suite

Small scale ferments (250 mL)• DO measured by Firesting in flask• Gas O2 composition in feed line

Experiments to assess:• Influence of initial juice DO• Timing of oxygen addition• Amount of oxygen required

Oxygen concentration in juice at inoculation

• Moderate increase in biomass

• Moderate acceleration of fermentation kinetics

• No differences in wine chemistry

How much O2 is enough?

• Biomass and fermentation kinetics increased proportionally with increasing oxygen concentration

• Stimulatory effect limited at higher oxygen concentrations

When is oxygen addition most beneficial?

• Impact decreased with later treatment times

• Some stimulatory effect even at 50% initial sugar

Treatment – 2 hours at a dissolved oxygen concentration of 2 – 2.5 mg/L

90755030

% initial sugar at treatment

Oxygen addition regimes:Hard and fast or low and slow?

TreatmentDuration

(h)

Input gasConc

(% air)

DissolvedOxygen

Conc (mg/L)

Total oxygen consumption

(mg/L)

2 5 0.2 8

2 50 2.0 65

24 1 0.02 16

72 1 0.02 65

• Total oxygen delivered is the most important factor

• High and fast trumps low and slow

Treatment times

Pilot-scale experiments

550 L fermentersHeadspace flushing ŵ 40% CO2 in N2DO monitoring/logging in tank

Firesting O2 probe

Effect of O2 treatment during fermentation on sugar utilization

Early-Long treatment leads to

• Highest conc:- hexanol- propanoic acid- ethyl 2-methyl propanoate- 2 & 3-methyl butanoic acid+ ethyl ester

• Lowest conc:- hexyl acetate- ethyl butanoate- 2&3-methylbutyl acetate- Butanol- 2-phenylacetate- ethyl acetate- hexanoic acid+ ethyl ester - octanoic acid + ethyl ester - decanoic acid + ethyl ester

Barossa CHA, 2015

Effect of O2 treatment during fermentation on sugar utilization

0.0

1.0

2.0

3.0

4.0

Yellow ColourOverall Fruit Aroma

Tropical Fruit Aroma

Stonefruit Aroma

Citrus Aroma

Confection

Floral

Green Aroma

Flint

Sweaty/Cheesy

Chemical

PungentOverall Fruit Flavour

Tropical Fruit FlavourStonefruit Flavour

Citrus Flavour

Green Flavour

Sweet

Salt

Viscosity

Oily

Acid

Hotness

Astringency

BitterFruit Aftertaste

Control

Early-Long

Early-Short

Late-Long

LSD = 0.26

LSD = 0.22

LSD = 0.22

*

*

*

Summary

• Aeration is an effective strategy for the management of fermentation performance

• Hard and fast at around 80% initial sugar most effective

• Attenuated benefits later in ferment

• Inoculation immediately following aerobic racking

• Are there risks of oxidation? - No

• What are the effects on sensory properties? - minimal

Is there a dose-effect with O2 at crushing/pressing?

Hand-picked Pinot Gris (Eden Hills)

Whole bunch pressed;1,200 kg loads

Five O2 concentrations in N2 :

0%, 5%, 10%, 15%, 20%

20 L keg collected after press cycle

Fermented in 5 L scale

Is there a dose-effect with O2 at crushing/pressing?

050 oteUotal Photal Hy

Variation in summed volatile compounds

Somers’ phenolics (wine)

Fermentation efficiency

Oxygen addition during pump-overs

O2

DO out

DO in

Treatments:

Early (20% drop in TSS)

Daily (5 consecutive days)

Late (80% drop in TSS)

No treatment

1 aeration post pressing

Details:• 350 kg Shiraz

• 2 x 03 min pump-over ŵ irrigator per 24 hrs

• 1 x 60 min sub-cap aeration @ 5 L/min per 24 hrs

• DO monitored in tank & before/after aerator

Tannin and colour outcomes

E a r lyD a ily

L a te

p o s tPre

s s

N o T r tmt

1 0

1 1

1 2

1 3

1 4

W in e C o lo u r D e n s ity (S O 2 c o rr )

AU

B

A A AA

E a r lyD a ily

L a te

p o s tPre

s s

N o T r tmt

0 .4 5

0 .5 0

0 .5 5

0 .6 0

C o lo u r H u e

A4

20

/A5

20

(A

U)

B

A

B B B

E a r lyD a ily

L a te

p o s tPre

s s

N o T r tmt

4 0 0

5 0 0

6 0 0

7 0 0

T o ta l A n th o c y a n in s

Σ A

nth

oc

ya

nin

s (

AU

)

B

A A AA

E a r lyD a ily

L a te

p o s tPre

s s

N o T r tmt

3 5

4 0

4 5

5 0

5 5

6 0

T o ta l p h e n o lic s

ΣP

he

no

lic

s (

AU

)

B

A B

A A A

E a r lyD a ily

L a te

p o s tPre

s s

N o T r tmt

8

1 0

1 2

M e a n D e g re e o f P o ly m e r is a t io n

mD

P

B

A A A A

E a r lyD a ily

L a te

p o s tPre

s s

N o T r tmt

1 5

2 0

2 5

3 0

% S k in T a n n in

%T

ri-O

H

C

B

A A A

Acknowledgements

Oxygen Project TeamSimon SchmidtRadka KolouchovaEric WilkesPaul Smith

AWRI Sensory TeamAlice BarkerWes PearsonLeigh Francis

This work is supported by Australia’s grapegrowers and winemakers through their investment body Wine Australia, with matching funds from the Australian Government. The AWRI is a member of the Wine Innovation Cluster in Adelaide.

Measuring DO in the winery

Presens (blue-red optoluminscence)

Pyroscience “Firesting”

(uses better red-NIR optoluminscence)

Process-grade probe

miniDOT: DO logger in-situ

(AWRI technology transfer from the

waste water treatment industry)

Standard hand-held DO meter:

Measuring oxygen inside the press

Inside the press(Tscharke Wines)

DO = 3.3% air sat (±2.1) or ~370 ppb (±230)

Time

Normal modeInert mode

DO

80% air sat

Flushing