Extreme Winemaking Overcoming the challenges in

Icewine production and the application to other wine styles.

Debra Inglis, Derek Kontkanen, Gary Pigeau,

Caitlin Heit and Gary Pickering Cool Climate Oenology and Viticulture Institute

Brock University, ON, Canada ICCWS May 28, 2016 Brighton, England

Introduction To Icewine

•  Icewine is the most extreme of the late harvest dessert wines

•  made from grapes that have naturally frozen on the vine

•  First made commercially in Canada in mid 1980’s

•  Canada now annually produces one million Litres

The Varieties Used In Canada

•  Mainly Vidal – 80% •  Riesling – 15% •  Cabernet Franc- 5%

•  Other varieties are used in very limited supply

•  Vidal is the only hybrid grape allowed for Icewine production

What Are The Challenges In Icewine Production?

1.   Strict regulations •  protect authenticity of product

2.   Hanging the grapes until harvest

3.   Harvesting and pressing the grapes while they remain frozen

4.   Fermenting the juice into wine

5.   Stabilizing the wines

1. The Regulations

•  Registration •  Grapes must be registered before Nov 15, and

harvested after Nov 15 •  Correct Temperature

•  Grapes must naturally freeze on vine •  Grapes must be harvested and pressed below -8°C

(18°F) (usually –10 to -12°C, 14-10°F)

•  Call in to register when harvesting •  Must record weight of grapes

•  Volume of juice must be inline with weight of grapes pressed

•  Juice Brix: min of 35° prior to fermentation •  Alcohol 7-14.9%v/v; Residual sugar 125 g/L; VA <2.1

g/L

2. Hanging the Grapes “The Risks”

•  Temperature – will it get cold enough?

•  Disease – botrytis NOT wanted in Icewine

•  Predation – birds and other wildlife

Predation

• BIRDS • starlings

• Deer

• Racoons

• Coyotes

3. Harvesting And Pressing The Grapes While Frozen

•  The temperature must remain below -8°C (18°F) for harvesting and pressing •  If too cold (<-14°C, <7°F), juice is too

concentrated, Brix are too high and volume is too low

•  Best temperatures for picking and pressing are -10 to -12°C (14°F to 10°F) to ensure: •  the water in the berry freezes •  the juice is concentrated between 35°-40°Brix •  Good volume return from the frozen grapes

Limited window to harvest, now use regular machine harvester

Berries shaken right through the nets

4. Fermenting Icewine

•  Fermentations are slow •  (commercial scale: 6-8 weeks, sometimes 3-4 months)

•  Wine yeast only double 2-3 times •  Difficult to reach target ethanol values (10% v/

v) •  High sugar in the juice evokes a stress response

in the yeast (hyperosmotic stress) •  Environment leads to high levels of glycerol (10

g/L) for yeast to survive accompanied by acetic acid (0.5-2.3 g/L) in commercial Icewines

What are the effects of high sugar concentration on wine

yeast?

Concentrated juice causes yeast cells to shrink

Icewine Juice 40 Brix

Dilute Juice 20 Brix

5 hours post-inoculation

How do wine yeast survive when they lose water by

osmosis, shrink in size and stop growing?

Let’s look at some metabolic biochemistry

OCH2OH

HOOHOH

OH

OCH2OH

HOOHOH

OH OCH2OH

HOOHOH

OH

OCH2OH

HOOHOH

OHO

CH2OH

HOOHOH

OH

OCH2OH

HOOHOH

OH

OCH2OH

HOOHOH

OH

OCH2OH

HOOHOH

OH

OCH2OH

HOOHOH

OHO

CH2OH

HOOHOH

OH

Glucose

G-6-P

F-1,6-bP Gly-3-P

Pyruvate

Acetaldehyde

EtOH

NADH

NADH NAD+

NAD+

Glycerol 3-P

DHAP

Glycerol

NAD+

NADH

Acetate

NAD(P)H

NAD(P)+

Cell Morphology

5 h 24 h 48 h 72 h 96 h 120 h

20 Brix

40 Brix

Sugar Stress Generates Glycerol

0.0

2.0

4.0

6.0

8.0

10.0

12.0

0 100 200 300 400 500 600

Gly

cero

l (g

/L)

Time (h)

40 Brix

20 Brix

Sugar Stress Increases Acetic Acid

0.00.20.40.60.81.01.21.41.61.8

0 100 200 300 400 500 600

Time (h)

Ace

tic A

cid

(g/L

)

40 Brix

20 Brix

Acetic Acid production is a function of juice concentration

0.000.200.400.600.801.001.201.401.601.80

15 25 35 45

Soluble Solids (Brix)

Ace

tic A

cid

(g/L

)

Overcoming the challenges of Icewine Fermentation

1.   Juice Concentration: Keep below 42 Brix

2. Use enough yeast (Inoculate at 0.5 g/L)

3. Allow yeast to get use to concentrated juice (acclimatize)

4.   Give yeast vitamins and minerals to help them overcome the stress

Tips for Successful Icewine Fermentation: Juice Concentration

To reach target ethanol, DO NOT EXCEED 42°Brix Theoretically, wine yeast would not ferment

Icewine juice above 52.5°Brix.

39 40 41 42 43 44 45 46 47 48 49 50 51 52 530

100

200

300

°Brix

Sug

ar C

onsu

med

(g/

L)

39 40 41 42 43 44 45 46 47 48 49 50 51 52 530

2

4

6

8

10

12

14

°BrixE

than

ol

(%)

Tips for Successful Icewine Fermentation: Use sufficient yeast

0

2

4

6

8

10

12

0.2 g/L 0.5 g/L

Etha

nol (

%v/

v)

Yeast Inoculation Rate

Ethanol Production at 0.2 g/L vs 0.5 g/L

For 38-42°Brix juice, to reach target 10% v/v ethanol, use 0.5 g/L yeast

(50 g/hL)

Tips: Step-wise acclimatization of yeast to Icewine juice

3 hour procedure (Kontkanen et al. 2004 Am.J. Enol. Vitic. 55: 363-370)

•  After yeast are rehydrated with warm water (40°C, 104°F) and micronutrients for 15 minutes •  Dilute a small amount of Icewine juice in half to

20°Brix and allow it to come to room temperature (25°C, 77°F)

•  Add equal volume of room temperature diluted Icewine juice to rehydrated yeast, hold 1 hour, gentle stirring every 30 min ⁻  Starter culture now at 10°Brix

•  Add equal volume of room temperature Icewine juice to starter culture, hold for 2 hours, gentle stirring every 30 min ⁻  Starter culture now at 20°Brix

Step-wise acclimatization of yeast to Icewine juice Con’t

•  Inoculate Icewine juice (warmed to 20°C, 68°F) at 0.5 g/L yeast using acclimatized starter culture

•  Recommended to allow yeast to further acclimate in the fermentation at 20°C (68°F) for 1 day after which temperature can be reduced to 17°C (63°F) for fermentation

Yeast Acclimatization

0 .00 .20 .40 .60 .81.01.21.41.61.82 .0

0.5 g/L 0.5 sw g/L

Aceti

c a

cid

(g

/L)

No GO-FermGO-Ferm

c

a

a

b

******

Not acclimatized Step-wise acclimatized

The results of using Micronutrients and Step-wise acclimatization of yeast to Icewine juice

•  Derek Kontkanen developed the procedure for his MSc thesis to reduce stress on the yeast and improve Icewine quality

•  Now professional winemaker in BC, Canada

•  he won World’s Best Dessert Wine for his Icewine at the International Wine and Spirits Competition in London, England in 2010

•  Then repeated it in 2011!

(Kontkanen et al. 2004 Am.J. Enol. Vitic. 55: 363-370)

Summary: How to avoid fermentation problems in high sugar juices

•  Recommended to not exceed a juice concentration of 42°Brix in order to reach target ethanol

•  Use a sufficient yeast inoculum for the juice concentration •  20 g yeast dry weight/hL (0.2 g/L) is a sufficient

inoculum rate for table wine fermentation •  50 g yeast dry weight/hL (50 g/hL) is a sufficient

inoculum rate for Icewine fermentation when using juice at 38-42 Brix.

Summary: How to avoid fermentation problems in high sugar juices •  Micronutrients and step-wise acclimatization reduce stress

on yeast •  reducing acetic acid production and the time required to

reach target ethanol •  Stabilize the wines with SO2 and potassium sorbate •  The acid profile in Icewine has a significant contribution

from weaker yeast organic acids (acetic and succinic) that elevate the TA in Icewine by 2 g/L but may also elevate the pH. •  Further acidulation may be required for palatability to

reach the desired sweetness:sour ratio

Summary

•  From the challenges of bird and disease pressures to harvesting in the middle of bone-chilling nights followed by the yeast’s struggle to ferment in such a hostile environment, a treasure comes forward from the extremes

ICEWINE

Acknowledgements

Lab Group •  Gary Pigeau PhD student •  Stephanie Martin PhD student •  Derek Kontkanen MSc student •  DiQing Tang MSc student •  Caitlin Heit MSc student •  Elisa Bozza (4th year, Udine) •  Jamie Quai (4th year student) •  Marc Pistor (4th year student)

Industry partners •  Vincor Canada and Inniskillin Wines

(Niagara-on-the-Lake, ON) •  Lallemand Inc. •  Karl Kaiser, Donald Ziraldo, Gerald

Klose (Inniskillin) •  David Sheppard (Coyotes Run)

CCOVI Colleagues •  Gary Pickering, Andy

Reynolds, Ian Brindle, Kevin Ker

Funding •  Natural Sciences and

Engineering Research Council of Canada (NSERC)