Improving Wine Quality from Hot Climate Regions

In Texas, Black Spanish is primarily grown in the Hill Country, South East, and along the Gulf of Mexico, where Pierce’s Disease is prevalent making it the fourth leading wine grape in the state. The cultivar carries a natural resistance to Daktulosphaira vitifoliae and Pierce’s Disease. Black Spanish grapes make wine with undesirable flavors (funk), color instability and low tannins. The wine made from Black Spanish grapes for this experiment utilized a Flash détente. The flash détente disrupts cellular structures by super heating grapes for a short period of time and rapid cooling in order to increase extraction of anthocyanin pigments and copigments. The wine made from treated grapes was evaluated by a train panel to define funk. Panelists found that there was a decrease in Black Spanish funk and an increase in mouthfeel, astringency, and tannins in flash treatments. The second study aimed to improve wine from cultivars grown in hot climates that lead to low pH juice. If hot temperatures drive up pH values > 3.7 wines will become less stable and will more habitable for spoilage organisms leading to negative sensory effects. Riesling grapes used for the experiment had a pH 4.0 were treated with Catazyme® 25L (glucose oxidase and catalase) that utilizes glucose oxidase to enzymatically reduce pH with minimal sensory detection. The conversion of d-glucose into gluconic acid immobilizes its ability to act as a fermentable sugar and increases acidity. The increase in acidity from the production of gluconic acid caused a significant pH decrease in treated wines. Panelists found that treatments with Catazyme® 25L increased in positive flavor and aroma attributes while also improving wine color. This research stands to benefit the wine industry by finding viable ways to improve wine quality