The Impact of Racking and Returning on Wine Quality (2017)

This study examines the impact of racking and returning during aging on red wine quality. Petit Verdot wine was split into two identical barrels. Once malolactic conversion was completed, one barrel was racked into tank, the barrel was pressure washed and ozonated, and then the wine was returned to the barrel and topped. The other barrel had no treatment. All other treatments between wines were identical. No major chemical differences were apparent between treatments. VA was slightly lower in the racked wine. Some sulfide parameters were lower in the racked wine, although whether these differences would impact flavor is hard to say. For the triangle test, of 20 people who answered, 7 people chose the correct wine (35%), suggesting that these wines were not significantly different. In general, of those who correctly identified the wines, 2 had no preference, 2 preferred the control, and 3 preferred the rack and returned wine. For the descriptive analysis, there were no trends for the descriptors used in this study. Judges commented that these wines were very extracted, which may have masked differences between wines. In the future, this study should be repeated on less intense grape varieties. Furthermore, the wine should be allowed to age more in future studies.

Read Full Report (PDF)

The Impact of Adding Viognier Skins to Petit Verdot Fermentations (2017)

This study examines whether adding Viognier skins to Petit Verdot fermentations alters the chemical and sensory qualities of the wine. The goal of adding Viognier skins was to mellow out some of the harsher characteristics of Petit Verdot. Petit Verdot grapes were crushed and split into two separate T Bins. To one bin, 10% w/w of Viognier skins were added (the skins were received a couple of days before processing Petit Verdot and were refrigerated prior to addition). An attempt was made to sort stems out of the Viognier skins. The other bin did not receive Viognier skins. All other treatments between wines were identical. Volatile acidity was slightly higher in the wine with Viognier skins. Color, and several phenolic parameters, were reduced in the Viognier skins treatment. For the triangle test, of 7 people who answered, 2 people chose the correct wine (29%), suggesting that the wines were not significantly different. No preference trends were discernible. For the descriptive analysis, there were no strong trends for the descriptors used in this study. The wines with Viognier skins had a slight tendency towards higher Bitterness, and perhaps higher Astringency. Although the chemistry suggests that the Viognier would reduce the tannic character of the wine, the sensory results suggest otherwise. More studies are needed in order to more fully evaluate the impact of adding white grape skins to red wine fermentations on chemical and sensory qualities.

Read Full Report (PDF)

Whole Cluster Inclusion in Petit Verdot Fermentations (2017)

This study examines the impact of whole cluster fermentation versus more traditional fermentation techniques in Petit Verdot winemaking. Petit Verdot grapes were harvested and processed into two T Bins. One treatment was completely destemmed, whereas the other treatment was 100% whole cluster inclusion. The 0% inclusion treatment was punched down, whereas the whole cluster treatment was stomped for punchdowns. When the 0% treatment reached approximately 8 Brix, the fermenting wine was delestaged and the pomace was stomped, and the wine was then racked back into the stomped pomace. Wine was pressed 16 days after processing. Juice and wine chemistry were very similar between treatments, except TA was slightly lower in the whole cluster treatment. Color was slightly increased, and many phenolic compounds were increased by whole cluster inclusion. Although anthocyanin was lower from whole cluster treatment, polymeric anthocyanins were increased. Overall, these wines were not found to be significantly different. There may have been a slight preference for the whole cluster wine. The whole cluster wine tended to score higher in Bitterness, Astringency, and Fruit Intensity. The whole cluster inclusion treatment had the clusters stomped during T Bin filling, which may have reduced some of the more estery characteristics often seen in whole cluster winemaking. Thus, these results may be more in line with what would be expected with a stem inclusion wine, rather than a purely whole cluster wine. This study suggests that whole cluster inclusion may be a useful method for creating a Petit Verdot which could serve as a valuable blending component, but more studies on whole cluster Petit Verdot are needed to determine whether any strong trends can be seen between treatments over time.

Read Full Report (PDF)

The Impact of Soil Conductivity on Petit Verdot Ripeness and Wine Quality in VSP Trellising (in collaboration with Bubba Beasley) (2017)

This study attempts to quantify the impact of soil conductivity on VSP-trained Petit Verdot juice and wine chemistry, as well as on the sensory qualities of wine. Soil conductivity was determined by EM mapping performed by Bubba Beasley, in order to find areas of low and high conductivity within the vineyard block. The low conductivity soil had a low rock content, and the high conductivity soil had high rock content (75%, shale). Then, fruit from each conductivity region was harvested on the same day but kept separate and destemmed into two T Bins: One for low conductivity fruit, and the other for high conductivity fruit. Fermentations were punched down twice per day, and all other treatments between wines were identical. Yield and viticultural parameters suggest an ESVC:CW index of 1.2 for both the low conductivity and high conductivity. Acidity and potassium was higher in the high conductivity juice. Indeed, soil pH was found to be negatively correlated to petiolar potassium and positively correlated to fruit pH. Petiolar potassium was also found to be positively correlated to juice potassium. Wine made from higher conductivity grapes had higher acidity and lower potassium. The high conductivity treatment had slightly lower anthocyanin and tannin measures. These results, overall, suggest that the lower conductivity wine had generally “riper” characteristics. These results would not be expected, as the higher conductivity soil (with higher rock content) would be expected to have less total available water in the soil for the grapevines to use. It would be more expected, therefore, that the high conductivity vine would have had less water, and thus potentially more “ripe” chemistry characteristics. Overall, the wines were not found to be significantly different at tastings. There may have been a slight preference for the low conductivity wine, but if so it was very weak. There were slight tendencies for the high conductivity treatment to have higher Acidity and Bitterness, and slightly lower Body. These further suggest a less “ripe” wine was produced at the high conductivity block. This study should be repeated over multiple vintages in order to determine whether these results are replicable.

This study should be read with its companion study in Ballerina trellising.

Read Full Report (PDF)

The Impact of Soil Conductivity on Petit Verdot Ripeness and Wine Quality in Ballerina Trellising (in collaboration with Bubba Beasley) (2017)

This study attempts to quantify the impact of soil conductivity on ballerina-trained Petit Verdot juice and wine chemistry, as well as on the sensory qualities of wine. Soil conductivity was determined by EM mapping performed by Bubba Beasley, in order to find areas of low and high conductivity within the vineyard block. The low conductivity soil had lower soil rock content (10%, channers), and the high conductivity soil had higher rock content (50%, shale). Then, fruit from each conductivity region was harvested on the same day but kept separate, and destemmed into two T Bins: One for low conductivity fruit, and the other for high conductivity fruit. Fermentations were punched down twice per day, and all other treatments between wines were identical. Average berry weight and cluster weight were slightly higher in the high conductivity treatments. Yield and viticultural parameters suggest an ESVC:CW of 1.7 and 1.9 for the low conductivity and high conductivity, respectively. Juice Brix and potassium was lower, and acidity and nitrogen were higher in the high conductivity treatment. These differences transferred through to wine chemistry. The high conductivity treatment seemed to have lower levels of phenolic compounds, and lower color. These results, overall, suggest that the lower conductivity wine had generally “riper” characteristics. These results would not be expected, as the higher conductivity soil (with higher rock content) would be expected to have less total available water in the soil for the grapevines to use. It would be more expected, therefore, that the high conductivity vine would have had less water, and thus potentially more “ripe” chemistry characteristics. Overall, these wines were not found to be significantly different in triangle testing. No preference trends could be seen. Additionally, descriptive analysis results were inconsistent between tastings, and no general trends can be seen except perhaps that the high conductivity wine had slightly lower Body. In the future, this study should be repeated over multiple vintages, on different grape varieties, and at different sites.

This study should be read with its companion study in VSP trellising.

Read Full Report (PDF)

The Impact of Cold Soak vs Extended Maceration in Petit Verdot Wine (2017)

This study examines the impact of cold soaking vs extended maceration on Petit Verdot wine, with maceration time being equal between treatments. The goal was to have on treatment spend more time exposed to an aqueous phase, with the other treatment having more time exposed to an alcoholic phase. Petit Verdot grapes from the same vineyard block were harvested on the same day and destemmed into two separate T Bins. One T Bin underwent a 4 day cold soak prior to inoculation, whereas the other was immediately inoculated without cold soak. Both treatments underwent a 25 day maceration before being pressed off on the same day: thus, the cold soak received less time in contact with must in an alcoholic phase. All other treatments between wines were identical. Wine chemistry and ester profiles were not much different between treatments. The extended maceration treatment had higher levels of color, epicatechin, and tannin, but other phenolic compounds were not much different. The wines were not found to be significantly different via triangle testing. However, there was a strong trend for the cold soak wine to have higher Astringency than the extended maceration wine. There was a slight tendency for this wine to have increased Bitterness and lower Body as well. The total maceration time for these wines was long in both cases, and as such the differences seen here may be greater if smaller overall maceration times are used. In the future, this should be performed, and more microbial analysis should be performed 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 Bactiless on Microbial Stability in Petit Verdot (2016)

This study examines the impact of Bactiless (ScottLabs) on the chemical, microbial, and sensory profiles of two Petit Verdot wines, one of which was not tasted. Petit Verdot wine was racked into two separate barrels for each wine, and allowed to undergo natural malolactic conversion. After malolactic conversion, one barrel from each wine received a sulfur dioxide addition of 6.6g/hL, whereas the other barrel from each wine received 4.4g/hL sulfur dioxide and 50g/hL Bactiless. After 10 days both barrels were racked and returned. Bactiless seemed to lower cell counts for Pediococcus sp, acetic acid bacteria, and Oenococcus oeni. The results varied between wines, however. Other microbes were not strongly impacted by the treatment, but in many cases the cell count may have been too low to be impacted by the treatment. The wines were not significantly different from triangle testing. No major descriptive trends could be seen in this study.

Read Full Report (PDF)

The Effect of Toasted and Untoasted Oak Chips and Granular Oak Additions to Red Must (2016)

This study examines the impact of toasted and untoasted granular oak additions to Petit Verdot must. Petit Verdot grapes were sourced identically and processed identically into 4 separate fermentation vessels, one without oak additions, one with untoasted oak chip additions, one with toasted oak chip additions, and one with Xtrachene medium toast French granular oak additions. All other treatments were kept the same between wines. The Xtrachene granular oak exhibited the greatest increase in color intensity, tannin content, and polymeric anthocyanins (suggesting more color stability). Color was only slightly improved by oak chips. Untoasted oak chips and Xtrachene toasted granular oak exhibited an increase in caftaric acid, catechin, epicatechin, and gallic acid. Oak consistently lowered caffeic acid, although the numbers are very small. Anthocyanin extraction was not enhanced by oak, and was even lowered by toasted oak chips. In general, oak saw increases in color, catechin, epicatechin, and tannin, with granular oak resulting in the largest increases. In general, people preferred the control wine. The second-most preferred and least-most preferred wines were made with Granular Oak. No strong trends were found for the descriptors used in this study. The Granular Oak treatment seemed to increase Bitterness, Fruit Intensity, and Astringency more than the other treatments. Toasted Chips appeared to increase Fruit Intensity, along with Granular Oak. However, these tendencies were weak. Wines made with Granular Oak were often described as being oaky or smoky.

Read Full Report (PDF)

Andante, D254, and IONYS WF Yeast Trial in Petit Verdot (2015)

Andante, D254, and IONYS WF yeast strains were used in the fermentation of Petit Verdot.  IONYS WF yeast seemed to increase the titratable acidity and lower the pH slightly, and also seemed to lower the overall phenolic content of the wine.  IONYS WF and D254 wines were slightly more preferred than Andante wines.

Read Full Report (PDF)

Reverse Osmosis Trials (2014)

Reverse Osmosis was performed on Merlot, Malbec, and Petit Verdot wine in order to assess its effect on the chemical and sensory aspects of these wines.  Chemical parameters were not much affected by reverse osmosis, although color intensity was increased in RO wines.  Hue was also slightly increased, suggesting some oxidation from RO.  The Merlot and Malbec wines were found to be significantly different between treatments through triangle testing, but Petit Verdot showed no discernable difference.

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)