Vineyard Sprays to Improve Ripening in Merlot (in collaboration with VT) (2017)

This study examines the impact of different desiccation sprays on the resulting juice and wine chemistry of Merlot. 8 rows of Merlot from the same block were divided into 4 pairs, each pair of rows receiving a different treatment. The following treatments were performed: 1) Control (no spray), 2) RG 1950 spray in collaboration with Dr. Mizuho Nita, where rows were sprayed 4 times weekly, over four weeks, starting from veraison, 3) VT Tech Dehydration spray in collaboration with Dr. Bruce Zoecklein, where rows were treated on the fruit zone at approximately 19 degrees Brix using a 2% solution of methyl esters of fatty acids in a 2% solution of potassium carbonate in water, and 4) Sugar Express (Miller Chemical) Spray (4-10-40 Nitrogen-Phosphate-Potash), where rows were treated on the full canopy at approximately 19 degrees Brix at 10 lbs/acre. All other viticultural and winemaking practices were equal. Grapes were harvested on September 20, after processing musts were inoculated with D21, and each fermentation received a 16 day maceration. The two VT sprays had the greatest impact on Brix and Average Berry weight during ripening. Fluctuations are due to rain events around September 2 and September 6. The VT sprays produced juice with higher Brix, although the Zoecklein spray had higher TA and the RG 1950 had lower TA. Wine chemistry showed higher ethanol for these two sprays, higher TA and tartaric acid for all three sprays, and lower levels of lactic acid. Color intensity was increased by the desiccation sprays. Anthocyanins were slightly lowered for the VT sprays, although polymeric anthocyanin was increased for these sprays. Tannin showed slight increases for these sprays as well. These phenolic differences, however, were not very great.

Overall, the desiccation sprays had a tendency to lower the Herbaceous character of the wines. Overall Aromatic Intensity and Body tended to be increased by the Zoecklein spray, although RG 1950 also had a slight tendency to increase Body. These two sprays also had a slight tendency to increase Fruit Intensity, although this was weak. In general, the control wine was more similar to the Sugar Express treatment, and the two Virginia Tech desiccation sprays were more similar to each other. Preference trends were hard to determine, but the Sugar Express treatment tended to be less preferred. The two Virginia Tech desiccation sprays were perhaps slightly more preferred control when considering that these two wines were fairly similar to each other. These results suggest that desiccation sprays may be a valuable tool in Virginia winemaking, and studies like these merit more rigorous analysis, especially with regard to sensory attributes of the wines. These studies should be continued to be repeated, on multiple varieties over multiple vintages.

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The Effect of Desiccation Spray on Ripeness in Chambourcin (2016)

This study examines the impact of a desiccation spray on the chemical and sensory profiles of Chambourcin grapes and wine. One block of Chambourcin was divided so that one section of fruit was sprayed with a potassium bicarbonate desiccant, and another section was not sprayed. The desiccated fruit was sprayed at the beginning of veraison and then weekly for a total of four sprays over four weeks. The fruit was harvested and processed on the same day, and all treatments between the fruit were identical. The desiccation treatment slightly concentrated berry components, although not many differences were found in wine. The desiccation treatment, however, lowered the color intensity and slightly lowered the tannin and anthocyanin content in the wine. Other parameters were not greatly affected. At one tasting, the wines were found to be significantly different (p<0.05), and in general there was a preference for the wine made without desiccation. At another tasting, there was no significant difference between wines, and no major preference trends. More studies on desiccation across vintages would be beneficial to further elucidate the impact of these treatments in Virginia.

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The Effect of Crop Adjustment and Desiccation Spray on Ripeness (2016)

This study examines the impact of different crop adjustment techniques on yield, juice and wine chemistry, phenolic and color profiles, and sensory characteristics of Merlot. The four treatments in this trial were performed in the same vineyard block as follows: two control rows, two rows sprayed with RG 1950 desiccant spray, two rows with clusters dropped at veraison down to one cluster per shoot, and two rows with clusters pinched at approximately 20 Brix. All other treatments, through vinification, were the same. The desiccation spray exhibited faster ripening kinetics and lower average berry weight. At harvest, Brix and pH were not very different, but TA was higher in the treatments. No differences were apparent in wine chemistry. All treatments exhibited increases in color intensity, especially the cluster dropped treatment. In spite of increasing color intensity all treatments lowered anthocyanins. The desiccant treatment slightly increased tannins. The week before harvest, 6 inches of rain fell, which may have reduced the impact of these treatments. Overall, desiccation and crop reduction had a slight tendency to enhance Fruit Intensity. The treatments also tended to enhance Overall Aromatic Intensity. These trends were weak and often conflicted between tastings. There seemed to be a general preference for wines produced from dropped clusters and desiccated clusters, but this varied. The rain event may have reduced the impact of these treatments. This study suggests that crop adjustment techniques have the potential to impact fruit and wine quality in Virginia, but much more studies are needed to fully quantify this impact as well as to account for vintage variation.

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