Iowa State University, Horticulture Research Station ISRF09-36

Experimental Making

RFR-A9066 Edelweiss, Esprit, Gris (grey , but treated as white for this study), Murli Dharmadhikari, director LaCrescent, LaCrosse, Prairie Star, Seyval Sebastian Donner, assistant scientist Blanc, , and . Jennifer Hansen, research associate Midwest and Wine Industry Institute Pre-fermentation treatments. All red grapes were destemmed, crushed, and treated with Introduction 30 mg/L SO2 (sulfur dioxide in potassium The substantial growth of the Iowa grape and metabisulfite form) and 200 mg/L diamonium wine industry over the past decade resulted in phosphate. If necessary, sugar was added to the establishment of the Midwest Grape and obtain 23° brix. Three batches of Frontenac Wine Industry Institute to investigate various were treated according to the manufacturer’s cold climate grape cultivars and their potential instructions with ProMalic® yeast 4 hours for wine making. Unfortunately, due to the prior to inoculation with EC 1118 yeast. Three climate encountered in Iowa, we are not able batches of St Croix were treated with to simply adopt wine making practices used in 400 mg/L, 800 mg/L, and 1,200 mg/L of other parts of the world to achieve the best tannin supplement VR Supra®. Three batches quality possible for our region. The of were treated with 1,000 mg/L project described herein focused on the VR Supra®. Control batches for Frontenac, St production of small batches of experimental Croix, Marquette and the other reds did not wine to evaluate cold climate cultivars and the receive any further treatment prior to impact of conditions on the composition of the inoculation. final wines. Select white varieties (Esprit, Frontenac Gris, Materials and Methods LaCrescent, Traminette, and Vignoles) were The majority of grapes used in this project frozen and then pressed (whole clusters) to originated from the Horticulture Research produce concentrated juice. This juice was Station, Ames, IA. The remaining grapes used to make ice wine. Some white varieties originated from the Armstrong Research (Brianna, Edelweiss, Esprit, LaCrescent, Farm, Lewis, IA; Southeast Research Farm, LaCrosse, Prairie Star, and ) Crawfordsville, IA; and Northeast Research were destemmed, crushed, and pressed Farm, Nashua, IA. Details on the grapes without freezing. All white juices were treated themselves can be found in the viticulture with 30 mg/L SO2, 200 mg/L diamonium sections of this Annual Research Report. phosphate and 0.1 g/L Lafazym Press. The Treatment products listed herein (except juices were racked after 24 hours to minimize Acidex) were provided by Scott Laboratories. solids.

Varieties. Red varieties fermented on the skins Fermentation conditions. All wines were for this project were , fermented using standard wine making , (NY 70), DeChaunac, procedures using EC1118 yeast. Reds were Frontenac, GR 7, Leon Millot, Maréchal Foch, fermented at room temperature until dry. Marquette, (NY 73), and St Croix. Whites were fermented at 14°C to dryness White varieties, or grapes pressed and with the exception of ice wines. For ice wines, fermented without skins, included Brianna, sugar and alcohol levels were monitored Iowa State University, Horticulture Research Station ISRF09-36 throughout fermentation. Once the alcohol Results and Discussion level reached 10.5%, fermentation was Batches prepared have been and will be used stopped by moving the wines to a -5°C for trainings and workshops. Additional post- freezer. fermentation treatments will be performed to address the training needs. Due to the nature Post-fermentation treatments. Reds were of wine and its consumption, this project does pressed and treated with 50 mg/L SO2. Reds not necessarily focus on positive and negative were racked after two to eight weeks to outcomes. The goal is to give winemakers the remove more solids. Several batches of St knowledge and experience to develop their Croix were treated with varying amounts of own styles by providing examples of how post-fermentation tannin additions. These different cultivars and techniques can products included Biotan, Tanin Galalcool, influence the final product. Tan’Cor, Tan’Cor Grand Cru, Quertanin, and Tanin Plus. Acknowledgements These research efforts are supported by the Whites were racked after completion of Iowa Department of Agriculture and Land fermentation and 50 mg/L SO2 was added. Stewardship, the Leopold Center for White wines were treated with different Sustainable Agriculture, the Iowa Board of clarifiers, including Argilact (bentonite and Regents, Iowa State University College of casein), Casei Plus (casein), Gecoll Supra and Agriculture and Life Sciences, Department of Gelarom (liquid gelatins), Ichtyocelle Food Science and Human Nutrition, and ISU (isinglass), polyvinyl polypyrrolidone (PVPP), Extension. Treatment products were in part Polylact (PVPP and casein), and hot mix donated through Mike Jones by Scott Sparkolloid. Laboratories. The highly valued in-kind support by the Horticulture Research Station Various post-fermentation deacidification and staff, primarily superintendent Nick techniques, such as using Acidex, calcium Howell and agricultural specialist Dennis carbonate, or potassium carbonate to lower the Portz, also is greatly appreciated. acidity, were and will be employed to determine their effect on the organic acid profile and palatability of wines. Chemical analysis was performed throughout the process and included hydrogen ion concentration (pH), titratable acidity, volatile acidity, organic acid profile, alcohol, and sugar. Sulfur dioxide concentrations were monitored and adjusted as necessary to prevent oxidation. All wines were coarse filtered prior to bottling. Wines with residual sugar (ice wines) were treated with 250 mg/L potassium sorbate just prior to bottling.