Justine E. Vanden Heuvel

Timing of Cluster Light Environment Manipulation during Grape Development Affects C13 Norisoprenoid and Carotenoid Concentrations in Riesling

Sunlight exposure of winegrape clusters is frequently reported to increase C(13)-norisoprenoids in resulting wines, but the timing and mechanism of this influence is not well understood. Fruit zone leaf removal was applied to Vitis vinifera cv. Riesling at three timings: 2, 33 and 68 days past berry set (PBS), and compared to an untreated control. Free and total 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN), vitispirane and beta-damascenone were measured in juice and wines, and carotenoid profiles were determined in grapes at midseason and maturity. Significantly higher total TDN was observed in grapes from the 33-day PBS treatment compared to the control and other treatments (195 microg/L vs 54-87 microg/L). Total vitispirane in juice was also significantly increased in the 33-day PBS treatment, while total beta-damascenone was reduced in the 68-day PBS treatment compared to the control. Existing HPLC protocols were modified to allow for quantification of zeaxanthin in V. vinifera berries, and zeaxanthin was determined to be significantly higher in the 33-day PBS treatment than the control or other treatments (p < 0.05). Total TDN in juice correlated with free TDN in wine, with 11.0% +/- 2.5% of total juice TDN converted to free TDN in wine. In contrast, total vitispirane increased significantly during fermentation, and was not correlated with vitispirane in juice. In summary, leaf removal at 33 days PBS significantly increased zeaxanthin in Riesling grapes midseason, total TDN and vitispirane in the juice of mature Riesling grapes, and free and total TDN in finished wine, while earlier or later leaf removal had no effect.

Impact of Shoot and Cluster Thinning on Yield, Fruit Composition, and Wine Quality of Corot noir

Cluster thinning (CL), shoot thinning (ST), and a combination of the two practices (ST+CL) were applied to vigorous Corot noir (hybrid sp.) winegrapes grown at a commercial vineyard in the Finger Lakes region of New York State. Yield was reduced by CL (by up to 4.8 kg/vine) but not ST in 2008, and by ST (by up to 2.0 kg/vine) and not CL in 2009; however, high pruning weights (up to 4.5 kg/vine in 2008) and low crop-load ratios (ranging from 2.3 to 7.1) indicated that vines in the study were undercropped regardless of treatment. CL increased soluble solids by up to 2.5 Brix in 2008 and by up to 0.8 Brix in the ST+CL treatment in 2009, while ST increased soluble solids in 2009 by 0.8 Brix. The treatments had variable impacts on wine anthocyanin, berry skin tannin, berry seed tannin, and wine tannin depending on year. Wine tannin (42 to 64 mg/L) and tannin extractability (5 to 6%) were both very low compared to values typically observed in red wines produced from V. vinifera. Using a two-alternative forced choice test, panelists reported ST+CL wines were fruitier than the control and ST wines and that ST wines were less fruity than the control in both years. An economic analysis indicated that in order for growers/wineries to maintain their economic welfare, bottle prices would have to increase by

Impact of Shoot Thinning and Harvest Date on Yield Components, Fruit Composition, and Wine Quality of Marechal Foch

0.02 to

Cluster Thinning Reduces the Economic Sustainability of Riesling Production

0.41 depending on the practice and year to compensate for additional labor costs and lost yield in implementing these crop-load management practices.

Modeling Impacts of Viticultural and Environmental Factors on 3-Isobutyl-2-Methoxypyrazine in Cabernet franc Grapes

Marechal Foch grapevines were subjected to shoot thinning (~15 shoots per meter of row and no shoot thinning) in combination with two harvest dates (early harvest and late harvest) in a factorialized treatment arrangement for two years (2007 and 2008). With shoot thinning, yields were reduced by 3.1 to 7.2 kg per vine and clusters were reduced by up to 59 clusters per vine, while berry weight increased by 0.03 to 0.09 g. Shoot thinning reduced crop load by 4.3 to 7.8 kg yield per kg pruning weight, and increased soluble solids in 2008 by 0.7 to 1.2 Brix. Shoot thinning increased berry anthocyanins by 1.25 to 2.24 mg/g fresh skin weight malvidin-3-glucoside, but no corresponding increase was observed in wine anthocyanins. Delaying harvest resulted in increases of soluble solids (0.5 to 2.3 Brix) and berry anthocyanins (0.32 to 1.48 mg/g) and significantly higher anthocyanins in finished wines. Both late harvest and shoot-thinning treatments resulted in decreased six-carbon alcohols (3 to 33%) in finished wines. The total concentration of tannin in Foch fruit was comparable to that of some vinifera (0.75 to 1.05 mg/berry catechin equivalents). However, the extractability of tannins during winemaking was very low compared to most vinifera (2 to 4%), in part likely due to the low skin tannin concentration. Using a two-alternative forced choice test, panelists reported that later harvest 2008 wines were more “fruity” than their early harvest counterparts for both treatments and that shoot thinning did not affect fruitiness.

Impact of Undervine Management on Vine Growth, Yield, Fruit Composition, and Wine Sensory Analyses in Cabernet franc

Crop levels of 1 (low), 1.5 (medium), and 2 (high) clusters per shoot established by cluster thinning (CT) were compared to nonthinned (control) Riesling vines over a three-year period. Yields ranged from 5.2 to 12.4 t/ha in 2008 and from 4.0 to 9.3 t/ha in 2009, while crop loads (yield/pruning weight) ranged from 2.9 to 8.7 in 2008 and 2.9 to 9.9 in 2009. By 2010, yield and crop load (yield/pruning weight) did not differ among treatments. Cluster weight was unaffected by CT in 2008 and 2009 but in 2010 control clusters weighed 39% less than low crop. There was little or no CT effect on berry size, pH, titratable acidity, pruning weight, cluster light exposure, or bud cold hardiness. Soluble solids at harvest ranged from 18.2 Brix in control to 22.3 Brix in low crop in 2008, from 18.9 to 22.1 Brix, respectively, in 2009, and from 20.5 to 22.0 Brix, respectively, in 2010. A consumer wine aroma sorting trial revealed that the low crop wine, and the low and medium crop wines, differed in aromatic attributes from the other treatments in 2008 and 2009, respectively. Grower financial net return per hectare ranged from

Use of Normalized Difference Vegetation Index Images to Optimize Vineyard Sampling Protocols

2,832 in low crop to

Vineyard under-vine floor management alters soil microbial composition, while the fruit microbiome shows no corresponding shifts

16,055 in control in 2008, from −

Palissage Reduces Cluster Zone Lateral Shoots Compared to Hedging

115 to

Annual Under-Vine Cover Crops Mitigate Vine Vigor in a Mature and Vigorous Cabernet franc Vineyard

8,596, respectively, in 2009, and from