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
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
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
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)+
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)
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