Impacts of Regulated Deficit Irrigation on Cabernet Sauvignon Grapes and Wine Jim Harbertson, Richard Larsen, Federico Casassa, Markus Keller Washington 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 % ETc Pruning weight = 0.91 kg/vine 25 % ETc Pruning 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 SO 2, 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
Back to RDI & berry size RDI RDI A) Concentration (mesocarp reduction) RDI B) Biosynthesis (vacuole concentration)
Two Sets of Experiments Dr. Keller, Dr. Smithyman, Dr. Riley Dr. Larsen & now Dr. Casassa Cold Creek Vineyard: Cabernet Sauvignon 1 st Exp. When should deficit be applied? Early, Late, or Full? 2 nd Exp. Full season deficit severity and compensation
Fruit & Wine Chemistry Industry Standard (IS) fruit & Late Deficit fruit and wine have low phenolics Early 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 and yield (2011, 2012, 2013) Berry weight, irrigation percent reduction and yields over 3 consecutive seasons (2011-2013) in Cabernet Sauvignon grapes of the different RDI treatments. Treatments Entire season Ψs (MPa) Berry weight Irrigation Yield Berry weight (g) % reduction Applied (mm) % reduction Kg/ vine % reduction Full irrigation: 100% ET c -0.83 a 1.15 a ----- 315 a ----- 6.53 a ----- Industry Std: 70% ET c -1.03 b 1.11 a 3 % 228 b 28 % 4.91 b 27 % Late irrigation: 25/100% ET c -1.03 b 0.99 b 14 % 180 c 43 % 5.68 b 15 % Full deficit: 25% ET c -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.
Fruit phenolics (2011, 2012, 2013) 7 Phenolics FW basis Phenolics per berry basis 6 6 Anthocyanins Skin tannins Seed tannins 5 Phenolics (mg/g FW) 5 4 3 2 1 0 b b ab a b b a a c c b a 100% ETc 70% ETc 25/100% ETc 25% ETc a a a a a a a a a a a a 100% ETc 70% ETc 25/100% ETc 25% ETc 4 3 2 1 0 Phenolics (mg/berry) Irrigation treatment Irrigation treatment Casassa, Keller, Harbertson, unpublished
YEAR : Tannin Structure Tannin distribution by concentration: RDI 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. 13
Effect of EM and RDI Tannin distribution 14
Effect of EM and RDI Quantitative Descriptive Analysis 2011 25% ET c 25/100% ET c 70% ET c 100% ET c 15
Casassa et al. (AJEV 2013) Descriptive analysis (2011) 25% ET c 25/100% ET c 70% ET c 100% ET c
Casassa et al. (AJEV 2013) Descriptive analysis (2011) Controls EM
Casassa et al. (AJEV 2013) Descriptive analysis (2011) 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% ET c reduced yield by 66% but differential gain in phenolics and color did not outweigh crop reduction 25/100 % ET c 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)