Impacts of Regulated Deficit Irrigation on Cabernet Sauvignon Grapes and

WineJim Harbertson, Richard Larsen, Federico Casassa,

Markus KellerWashington State University

Viticulture & Enology Program

RDI

• Provide less than full evapotranspiration demand (Keller, 2005)– More uniform ripening– Reduce water usage– Reduce vigor – Control berry size

100 % ETcPruning weight = 0.91 kg/vine

25 % ETcPruning weight = 0.42 kg/vine

Berry size

• Winemakers want small berries• Berries do not grow like balloons

Shellie (2004), cv. Merlot

Winemakers Like Phenolics

• Grape and wine pigments: Anthocyanins• Astringency of Red Wine:

– Tannins are heterogeneous class of molecules– Interaction with salivary proteins

• Long Term Color:– Polymeric Pigments known as stable Color– Anthocyanins react with tannins and other phenolics

• Antioxidant– Role of SO2, Fe, Cu

Where do they come from and why does that matter?

• Skins contain anthocyanins and large MW tannins– Large MW Tannins are effective protein ppt

• Seeds contain low molecular weight tannins– Small MW tannins are more less effective protein ppt– Tend to be more bitter than astringent

• When you pick fruit and how you make wine influences types of tannins and amount of pigments you extract

Concentration (mesocarpreduction)

A)

RDI

Biosynthesis(vacuole

concentration) B)

RDI

Back to RDI & berry sizeRDI

Two Sets of Experiments

• Dr. Keller, Dr. Smithyman, Dr. Riley Dr. Larsen & now Dr. Casassa

• Cold Creek Vineyard: Cabernet Sauvignon• 1st Exp. When should deficit be applied? Early, Late,

or Full?• 2nd Exp. Full season deficit severity and compensation

Fruit & Wine Chemistry

Industry Standard (IS) fruit & Late Deficit fruit and wine have low phenolicsEarly and Full Deficit fruit and wines have high phenolics

Late Deficit and Industry Standard Wines driven by Red and Brown hue

Early and Full Deficit Wines driven by Astringency, Color

So who would win a fight between…• T-Rex and Great White

Shark?• Lion and Tiger?• Snake and Mongoose?• Great White Shark and Orca?• Answer: Clearly it depends.• Land vs. Water; Future vs.

Past

• We pit vineyard vs. winery in these experiments

• Which one controls phenolic content of wine?

• Deficit Irrigation in the Vineyard vs….Extended Maceration & Saignée

• Not really.• But it makes it more exciting.

Berry weight, irrigation percent reduction and yields over 3 consecutive seasons (2011-2013) inCabernet Sauvignon grapes of the different RDI treatments.

TreatmentsEntire

seasonΨs (MPa)

Berry weight Irrigation Yield

Berry weight

(g)

% reduction

Applied (mm)

% reduction

Kg/vine

% reduction

Full irrigation: 100% ETc -0.83 a 1.15 a ----- 315 a ----- 6.53 a -----Industry Std: 70% ETc -1.03 b 1.11 a 3 % 228 b 28 % 4.91 b 27 %Late irrigation: 25/100% ETc -1.03 b 0.99 b 14 % 180 c 43 % 5.68 b 15 %Full deficit: 25% ETc -1.22 c 0.87 c 35 % 77 d 76 % 2.76 c 60 %Different letters within values in the same column indicate significant differences for Fisher’s LSD test and p < 0.05.

Berry weight and yield(2011, 2012, 2013)

Irrigation treatment

100% ETc 70% ETc 25/100% ETc 25% ETc

Phen

olic

s (m

g/be

rry)

0

1

2

3

4

5

6

a a aa

a a aa

a a aa

Phenolics FW basis Phenolics per berry basis

Irrigation treatment

100% ETc 70% ETc 25/100% ETc 25% ETc

Phen

olic

s (m

g/g

FW)

0

1

2

3

4

5

6

7

Anthocyanins Skin tannins Seed tannins

c b acb a ab

b ab ab

Casassa, Keller, Harbertson, unpublished

Fruit phenolics(2011, 2012, 2013)

Casassa, F., R. Larsen, C.W. Beaver., M.S. Mireles, M. Keller, W. Riley, R. Smithyman and J.F. Harbertson. Journal of Agricultural and Food Chemistry.

Tannin distribution by concentration: RDI

13

YEAR : Tannin Structure

14

Effect of EM and RDITannin distribution

100% ETc

70% ETc

25/100% ETc

25% ETc

15

Effect of EM and RDIQuantitative Descriptive Analysis 2011

Descriptive analysis (2011)

100% ETc

70% ETc

25/100% ETc

25% ETc

Casassa et al. (AJEV 2013)

Descriptive analysis (2011)

Casassa et al. (AJEV 2013)

Controls EM

Descriptive analysis (2011)

Casassa et al. (AJEV 2013)

Controls EM

Conclusions• Winemaking Techniques vs. Vineyard Techniques: Draw!

– Extended Maceration has impact on tannin structure and perception of astringency whereas RDI did not

– Extended Maceration impacted tannins, wine color and had more evident impact than vineyard treatments

– Flavor profile changes evident from sensory showing RDI has impact too

• Vineyard Treatments Reduce Yield too much– 25% ETc reduced yield by 66% but differential gain in phenolics

and color did not outweigh crop reduction– 25/100 % ETc was best choice for maintaining yield and some

phenolic improvements

Acknowledgements• Washington Wine Commission• Chateau Ste. Michelle Wine Estates

– Dr. Russell Smithyman, Dr. Bill Riley, Joe Cotta, & Juan Uribe• My coauthors and collaborators:

– Viticulture: M. Keller, L. Mills– Enology: F. Casassa, R. Larsen, M. Mireles, C. Beaver

• Sensory Impact of Extended Maceration and Regulated Deficit Irrigation on Washington State Cabernet Sauvignon Wines. L. F. Casassa, R.C. Larsen, C.W. Beaver, M.S. Mireles, M. Keller, W.R. Riley, R. Smithyman, J.F. Harbertson. American Journal of Enology and Viticulture 2013, 64 (4) 505-514.

• Effects of Vineyard and Winemaking Practices Impacting Berry Size on Evolution of Phenolics during Winemaking. L.F. Casassa, R.C. Larsen, J.F. Harbertson. American Journal of Enology and Viticulture 2016, 67:257-268

• ASEV.org (ASEV Best Paper Award Winners: 2014 & 2017)