Wine research in New York, Texas and Mississippi
When the 2020 ASEV National Conference scheduled to be held in Monterey, Calif., Was canceled, the wine community across the country was hoping this year’s conference would be held in person. That didn’t happen, but the 2021 conference took place virtually from June 22-24. One advantage of online conferences is that speakers from many different regions were able to present their projects, and on June 24, the Eastern Viticulture session focused on finding three locations east of the Rockies: Finger Lakes of New York, Mississippi and Texas.
“Effect of sun exposure on the evolution and distribution of anthocyanins in interspecific hybrid red grape varieties”
Catharine Dadmun, a doctoral student in the laboratory of Dr Anna Katharine Mansfield in the Department of Food Science and Technology at Cornell University, began her talk on red hybrid grapes by noting that these grapes have become more important for cool climates due to their disease resistance and economic importance. As a result, it is now necessary to optimize their production. One of the main sensory parameters to consider when optimizing production is color, because the color of a wine is one of the first characteristics that consumers evaluate, and an atypical color can greatly affect acceptability. and the perception of the quality of a wine. Anthocyanins, which create the color of wine, are key compounds in determining the quality of wine.
While the color chemistry of vinifera wines has been widely explored, the color chemistry of hybrids is largely unknown. This prompted Dadmun to conduct a two-year study on the evolution of monomeric anthocyanins during hybrid maturation in order to establish the distribution of anthocyanins in three hybrid varieties: Corot Noir, MarÃ©chal Foch and Marquette. In order to study the effect of sun exposure and vine microclimate on the color of the red hybrid grape, leaf pulling established an exposed treatment block and a shaded control vineyard block, and was repeated in triplicate for each cultivar. Exposure to light and variations in air temperature were followed in the Corot Noir vines throughout the ripening period in order to determine the generalized microclimate of the vine.
Samples were taken from three different vineyards in the Finger Lakes area every two weeks until harvest. The berries were weighed for each sample, the pulp was separated from the skins, which were lyophilized and then ground into a fine powder. The phenolic compounds were extracted from the crushed skins using 80 percent methanol, and the monomeric anthocyanins were separated from this fraction using solid phase extraction. Monomeric anthocyanins were analyzed by HPLC (high performance liquid chromatography).
The results showed that the leaf pulling treatment did not significantly affect the total anthocyanin concentration in any of the three cultivars. However, some individual anthocyanins within each cultivar changed in response to excessive sun exposure, suggesting the possibility that the anthocyanin profile and therefore the perception of color itself could be altered by this treatment of the vineyard. Although photosynthetically active radiation (PAR) increases with tearing of leaves, negligible changes in berry temperature have been observed. This study laid the groundwork for understanding the evolution of anthocyanins in hybrid grape cultivars and further optimizing wine color.
“Effects of Timing of Pruning and Leaf Removal on the Quality of Southern Mississippi Grapes”
Haley Williams is a master’s student at Mississippi State University working with Dr. Eric Stafne on berry crops at the Coastal Research & Extension Center in Poplarville, MS. She began her speech by acknowledging that Mississippi has a climate with high summer temperatures, high humidity, and considerable rainfall all year round. Despite this, the MidSouth hybrid cluster grape has been successfully grown in the Mississippi climate, in part because it is resistant to Pierce disease. Its low total soluble solids content and high titratable acidity are a challenge for winemaking and are two things that researchers would like to improve.
Williams and Stafne developed an experimental design consisting of 48 vines divided into four blocks, with three repetitions of each of the four treatments: early pruning; early pruning and leaf stripping; normal size plus stripping; and normal size.
MidSouth vines were pruned to around 60 buds mid-December for early pruning and late February / early March for normal pruning. The aim was to assess whether the timing of pruning would affect fruit quality and timing of harvest, with vines pruned early having less impact from heat, humidity and rainfall. Leaf stripping on early-pruned vines took place at the end of March at the pre-flowering stage, while on normal-sized vines, leaf stripping was carried out in mid-May after fruit set. The two prunings could not take place at the same time due to an order for a Covid-19 shelter in place. Leaf removal consisted of removing three to six leaves from the cluster area of ââeach successful primary shoot.
When the vines were in veraison from mid-June to the end of June, the researchers measured cluster temperatures, total soluble solids, titratable acidity and pH. They took readings from several clusters on a vine and then averaged them for that vine. The results showed that each treatment had an average temperature of about 39 Â° C and that there was no significant difference between them for total soluble solids, titratable acidity and pH.
When crop yields were determined, early pruning with leaf stripping had the most negative effect, while normal pruning with leaf stripping had the best results. Below normal yields may be due to a lack of fungicide sprays, combined with additional precipitation from tropical storm systems before harvest. Normal pruning + leaf stripping had the best Ravaz index (yield: pruning weight) and the best balance of the vine. The general conclusion was that normal height, with or without leaf stripping, was greater than early pruning treatments.
“Adjustment of the harvest load through canopy management and its effect on the quality of fruit and wine of tempranillo in Texas”
Dr Pierre Helwi is an extension viticultural specialist at the Texas A&M AgriLife Extension Service in the High Plains region. He began by defining crop load as the relationship between canopy size and crop level. The Ravaz index (yield of the vine / weight of size) varies ideally from 5 to 10 for vinifera and from 8 to 12 for American and hybrid varieties. Values ââare variety specific and can be influenced by canopy management practices.
For this project, the researchers used two canopy management methods – fruit pruning and thinning – and examined their impact on harvest load and then its effect on grape and Tempranillo wine composition in the Texas. The aim was to answer three questions:
- Does fruit pruning / thinning have an impact on harvest load?
- Is fruit thinning with a mechanical harvester possible? Does it have an impact on the overall health of the vine?
- Is there a correlation between the harvest load and the quality of the fruits and wine of Tempranillo?
The research was conducted in 2019 at Lost Draw Vineyards in Brownfield, TX on 12-year-old Tempranillo vines rooted on a bilateral cordon with five spurs per bead. There were three treatments for this project, which are typical for the vineyards in this region: 2 buds / spur; 3 buds / spur; and 3 buds / spur plus fruit thinning by mechanical harvester. Thinning took place in June, 30 days after flowering, which reduced yield by 12.5%. The fruits of the three treatments were harvested in September at 24 Â° Brix, which is typical of the region. The 3 buds / speron plus thinning had the lowest yield per plant, while the yield for 2 buds / ergot was moderate and for 3 buds / ergot the highest. In February, the height weight was calculated and there were no differences between the three treatments in height weight per foot.
The researchers concluded that the size and / or thinning of the fruits affects the harvest load. Additionally, fruit thinning with a harvester can be used to adjust the harvest load, but some damage from this procedure can occur on shoots and clusters, and some grapes die. .
A second part of the project consisted of harvesting the berries from veraison to harvest in order to compare the chemistry of the berries between the three treatments. They used three measures of grape maturity: Brix, pH and titratable acidity. Harvest results showed that the low harvest load had a higher Brix, higher pH, and lower TA than the moderate and high treatments, and also showed that the berries in this treatment had a higher ripeness rate. berries faster.
All the grapes were picked when the grapes for any of the three treatments reached 24 Â° Brix, the typical Brix level for Tempranillo in the region, and wines were made for each treatment. The composition of the wine was analyzed nine months after bottling (in glass decanters) for alcohol, pH, TA, VA, malic acid, lactic acid, tartaric acid. and color. The results presented were for alcohol, pH, TA and color. There were differences in the composition of the wine: the low harvest load had the highest Brix, the higher pH, the higher TA, and also the darkest color of the three harvest loads.
The conclusions of the second part of the project were, firstly, that the low harvest load treatment had a faster berry ripening rate and secondly, that there was a difference in the composition of the wine. The final conclusion was that low-processed wines were characterized by higher alcohol and higher pH, but such chemistry may not be desirable for Tempranillo vines grown in a hot climate. In summary, the harvest load can be adjusted by pruning and mechanical thinning of the fruit and influences the chemistry of Tempranillo berries and wine.