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.

Read Full Report (PDF)

Vineyard Sprays to Improve Ripening in Cabernet Franc (in collaboration with Bruce Zoecklein) (2017)

This study examines the impact of vineyard desiccant sprays on grape ripening and wine quality in Cabernet Franc. A block of Cabernet Franc was divided so that part of the block was backpack-sprayed with a desiccant spray (2% solution of methyl esters of fatty acids in 2% solution of potassium carbonate in water) provided by Bruce Zoecklein. The spray treatment occurred when the grapes had reached approximately 19 Brix (September 22, 2017) and clusters were coated until dripping with spray. Grapes were harvested on September 28 and were processed identically. Wines were pressed after 11 days of maceration. Cluster weight, total anthocyanins, and tannin were decreased in sprayed fruit. Brix was increased and acidity was decreased in sprayed fruit as well. Alcohol and potassium were higher in the sprayed wine, and acidity was lowered. Color, tannin, and polymeric anthocyanin were also higher in the sprayed wine, in spite of opposite trends being seen in this regard with the grapes. Overall, these wines were found to be significantly different. There was a tendency for the desiccated wine to have higher Body. Desiccated wines had a slight tendency for higher Acidity and Astringency, and lower Fruit Intensity. However, more sensory studies are needed to confirm these trends. There may have been a very slight preference for the non-desiccated wine. In the future, more studies should be performed on fruit desiccation, as it has potential to be a useful tool in Virginia grape growing. These studies should include the timing of desiccation sprays before harvest.

Read Full Report (PDF)

The Impact of Different Leaf Pulling Treatments in Cabernet Franc (in Collaboration with Cain Hickey) (2017)

This study examines the impact of different leaf pulling regimes on ripening in Cabernet Franc. Grapes received either: 1) No leaf pulling, 2) Standard leaf pulling (leaf pulling before mid-June on East side of vine), 3) pre-bloom leaf pulling (May 17, both sides of vine), 4) post fruit-set leaf pulling (June 2, both sides of vine), 5) Mechanical leaf pulling (May 26, post fruit-set, both sides of vine), 6) bagged clusters (July 22). Grapes were harvested on the same day. All other treatments were identical. Mechanical Leaf Pulling and Post-Fruit Set Leaf Pulling had the smallest average berry weight (no data is available for the bagged clusters). Pre-bloom leaf removal saw the greatest increase in average berry weight, but this was not significant when compared with No Leaf Pulling and Post-Fruit Set. Yield per vine was significantly lower on the pre-bloom leaf removal compared to No Leaf Pulling and Post-Fruit Set, but Brix was significantly higher. This yield difference likely resulted from the significantly lower cluster weight in the Pre-Bloom treatment, as well as the lower number of berries per cluster and the lower number of clusters per vine found in the leaf pulling treatments. The Pre-Bloom and Post-Fruit Set treatments spent much more time at critical temperatures between 35-40°C than the No Leaf Pulling treatment, due to greater exposure of the grapes. The Pre-Bloom treatment was overall cooler than the Post-Fruit Set treatment, possibly because of the decreased berries per cluster and thus looser cluster architecture allowing for better air flow and cooling.

Leaf pulling always increased tannin, quercetin, and anthocyanin concentration in grapes, with the greatest concentration of tannin in the Pre-bloom Leaf Removal and anthocyanin and quercetin in the Post-Fruit Set Leaf Removal. Leaf-pulled juice tended to have less malic acid and lower YAN. In general, TA and color was higher in finished wine with leaf pulling, with the greatest increases seen in post-fruit set leaf pulling. Caftaric acid, gallic acid, quercetin, tannin, and anthocyanin were generally increased by leaf pulling, with the most profound differences found in pre-bloom and post-fruit set leaf pulling. Bagged clusters showed much lower color and tartaric acid.

Due to the complexity of this project, the Mechanical Leaf Pulling and Bagged treatments were not tasted. Overall, descriptive results for these wines were inconsistent between tastings. Wines which had received leaf pulling were generally more preferred by judges, with preferences generally being for early leaf pulling regimes. This study should be repeated several times in order to further validate these results. It should also be performed on different grape varieties, at different sites, and on different trellising systems. More rigorous descriptive work should be performed on these projects, as well.

Read Full Report (PDF)

The Impact of Bloom Leaf Removal vs Veraison Leaf Removal (2017)

This study examines the impact of leaf pulling at either bloom or at veraison. The goal was to have looser clusters and smaller berries from pre-bloom leaf removal. A block of Cabernet Sauvignon (planted 2006) was divided so that every other row was a different treatment. One row had the four-most basal leaves removed at 30% bloom (mid-May), exposing the entire fruiting zone. Continuous passes were made to ensure fruit zone exposure throughout the season. Every other row had leaves removed at the start of veraison, in mid-August. Grapes were harvested and processed at the same times, and all other vineyard and winemaking treatments were identical between treatments. Each wine received a 6-day cold soak, and 25 days of total maceration. Grapes from prebloom leaf removal had lower TA, malic acid, and tartaric acid, with a similar pH to the control. Tannin was higher in grapes with pre-bloom leaf removal, but anthocyanins were lower. Pre-bloom wine chemistry was similar except for slightly lower acidity. Color intensity and tannin was also slightly increased in the pre-bloom wine, although these differences were not very pronounced. For the triangle test, of 19 people who answered, 6 people chose the correct wine (32%), suggesting that these wines were not significantly different. In general, of those who answered correctly, no preference trends could be seen between wines. For the descriptive analysis, there were no strong trends for the descriptors used in this study. Most descriptive results were mixed, but Pre-bloom leaf pulling may have had slightly lower Acidity and higher Body. It also may have had slightly less Herbaceous/Green  character, but these trends were weak. These results suggest that pre-bloom leaf removal may not always have as large of an impact as is often seen. This practice should be performed more at different sites, on different varieties, and in different vintages (perhaps rainier vintages which may benefit more from this kind of leaf pulling regimen). 

Read Full Report (PDF)

The Impact of Crop Management Timing on Wine Quality (2017)

This study examines the impact of the date of cluster thinning on juice and wine chemistry. The goal was to attempt to dilute the impact of potassium uptake during veraison by cluster thinning at later dates, in order to keep the pH lower. A block of Cabernet Franc was cluster thinned either pre-veraison (around Mid-August), halfway through veraison (around the end of August), and post-veraison (first or second week of September). Every third row received one of these treatments, so that treatments were evenly dispersed throughout the block to minimize variation. All grapes were harvested on the same day, and all other treatments between each juice and wine lot were identical. The later the clusters were dropped, the higher the average berry and cluster weight. The later the clusters were dropped, the lower the Brix and phenolic compounds. YAN was slightly higher in later cluster thinning sweeps. In general, wine made from later cluster dropping had slightly less ethanol, and slightly higher TA and tartaric acid. Color intensity was decreased with later cluster thinning, as were most phenolic compounds. Thus, earlier cluster thinning tended to enhance grape “ripeness” characteristics. For the descriptive analysis, there was a strong tendency for the 50% veraison treatment to have higher Herbaceous/Green character (LSD=0.43). There was a slight tendency for this wine to also have higher Bitterness. Pre-veraison cluster thinning may have had higher Fruit Intensity. Post-veraison cluster thinning may have had slightly lower Overall Aromatic Intensity and Astringency. In general, the wines which were cluster thinned at 50% veraison were most preferred. These results suggest that the beneficial impacts of cluster thinning prior to veraison on chemistry may not be beneficial towards flavor profiles. However, this study should be repeated over multiple vintages, at different sites, and with different grape varieties to better understand how this timing of cluster thinning affects a Virginia appellation.

Read Full Report (PDF)

The Effect of Canopy Area on Ripening and Wine Quality (2017)

This study examines the impact of canopy height and ripening on wine quality in Merlot. Three sets of five rows of Merlot were hedged to different heights in mid-June: 52 inches (High canopy), 44 Inches (Medium canopy, normal height), and 36 inches (Short canopy). All other vineyard treatments were identical. Not much additional shoot growth occurred after hedging. Grapes were harvested on August 25 and processed into separate T Bins. All other treatments were identical. Juice Brix was slightly higher for the short canopy compared to the higher canopy. This may have been due to a seeming resistance to rain dilution seen in the short canopy vine compared to the medium and higher canopy vines. The ethanol, TA, color, and tannin increased with decrease in canopy height, and pH decreased with canopy height. Overall, descriptive analysis had difficulty distinguishing the wines consistently. The short canopy treatment tended to have slightly more Bitterness and Overall Aromatic Intensity. The short canopy wine also exhibited some slight reduction relative to the other two wines, which may have influenced results. Fruit Intensity and Astringency tended to vary between wines between tastings. In general, the high canopy wine tended to be the most preferred. Future studies should examine how bud fruitfulness and yield are impacted by multiple vintages of heavy hedging, pick fruit at different times depending on which treatment is deemed “optimally” ripe, and hedging shoots when they reach their designated height to try to force lateral growth. More studies are needed to confirm the trends seen in this study, as well.

Read Full Report (PDF)

The Impact of Bagging Grape Clusters on Grape Ripening and Quality (in Collaboration with VT) (2017)

This study examines the impact of bagging grape clusters during the growing season on grape and wine flavor, chemistry, microbiology, and phenolics. The vineyard uses organic grape growing practices, and the goal of this project was to see if bagging grape clusters would improve disease resistance without negatively impacting grape and wine quality. The bags used were 19x27cm white paper bags with micropores. Corot Noir grapes in one block experienced 4 treatments: 1) not bagged, 2) bagged at pea-sized berries, 3) bagged at berry touch, and 4) bagged at veraison. Because of a prediction of reduced disease incidence in bagged clusters relative to unbagged clusters, and because unbagged, rotting clusters were going to be dropped during the season, green harvesting of the treatment clusters was undertaken on lagging blooming clusters at berry set in order to attempt to keep crop levels similar between treatments. Lagging clusters were also not bagged on treatment rows. Control and treatment grapes were harvested 2 days apart from each other, and the 3 treatments were combined into one must to ferment. Both control and treatment musts received a 10% saignee, both were inoculated with Renaissance Ossia yeast, and all other treatments between wines were equal. Both bins received 2 weeks extended maceration. Bagging clusters might have reduced incidence of black rot, with the earlier bagging treatments being more effective; however, more intensive work is needed to confirm this. The grape treatments generally exhibited slight increases in berry weight and cluster weight, as well as increases in malic acid, pH, and YAN. Juice and wine chemistry was not much impacted, except that acidity was lowered in the bagged treatment. Bagging clusters lowered the microbial content of the juice, although wine was not much impacted. All phenolic and color parameters, in grape and wine, were either reduced or did not change as a result of bagging. 64% of people were able to distinguish the wines in triangle testing, suggesting a statistically significant difference between them (p<0.001). Of those who correctly distinguished between the wines, there was not a major preference for one wine over the other, perhaps slightly favoring no bags. There were strong trends for the unbagged treatments to have higher Overall Aromatic Intensity and higher Acidity. There was a slight tendency for Fruit Intensity to be higher in the unbagged treatments as well.

Read Full Report (PDF)

Leaf Pulling on One vs Two Sides of Petit Verdot Vines (2017)

This study examines the impact of leaf pulling on one vs both sides of the vine in Petit Verdot. Petit Verdot vines (clone 400, planted 2012, 9x4 spacing, ESVC/CW index of 2.4) from the same block were split so that all vines received leaf pulling on the east side at flowering, and one portion of the vineyard received leaf pulling on the west side as well at veraison. Grapes were harvested on the same date, and all winemaking practices were identical between treatments. Must was inoculated with D80, Enzyme CX was added, punched down twice per day until fermentation was complete, and then switched to one punchdown per day during extended maceration (25 days maceration time, total). Juice chemistry was similar between treatments, although leaf pulling on one side resulted in higher alcohol content and lower acidity. Color and anthocyanin were not much impacted by treatments. Seed tannin indices (catechin, epicatechin, and gallic acid) may have been slightly lowered with leaf pulling on both sides. Tannin may have slightly decreased by this treatment, as well. The sensory results suggest that the two wines were significantly different. No strong trends could be seen for the descriptors used in this study,  although Acidity seemed to be lower in the one sided leaf pulling wine. No major preference trends could be seen between treatments. This study should continue to be performed over multiple years, in different regions, as well as on different grape varieties.

Read Full Report (PDF)

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.

Read Full Report (PDF)

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.

Read Full Report (PDF)

Surround Crop Protectant Trial with Petit Verdot (2014)

Petit Verdot that received heavy leaf pulling was either sprayed or not sprayed with Surround Crop Protectant in the fruiting zone in order to prevent sunburn.  No chemical, phenolic, or sensory differences were found in this study, suggesting that Surround does not negatively impact finished wine quality.  However, this year was a relatively light "sunburn" year at this vineyard, so the true impact of Surround may not have been adequately quantified.

Read Full Report (PDF)

Leaf Pulling Trial with Petit Verdot (2014)

For one half of a single block of Petit Verdot, leaf pulling was done on the east side of the vines. For the other half of the block, leaf pulling was done on both the east and west sides. The leaf pulling was done approximately one month prior to harvest. There were very little chemical differences between the wines, and no significant sensory differences were found.

Read Full Report (PDF)