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Objectives of this study were to quantify starch and soluble sugar concentrations in wine grape (Vitis sp.) scionwood and rootstock material, and to examine relationships between carbohydrate (CHO) metrics and both grafting success and shoot growth. CHOs of three wine grape scionwood cultivars [Merlot and Riesling (Vitis vinifera) and Vidal blanc (Vitis sp.)] harvested from four separate vineyards in the Niagara Peninsula in Ontario were analyzed for starch, total CHOs, total sugars, sucrose, monosaccharides (glucose, fructose), and oligosaccharides (raffinose, stachyose) to determine if CHO differences existed between scionwood cultivar and site, and whether these impacted propagation success when grafted to two different rootstocks [‘3309 Couderc’ (3309) and ‘101-14 Millardet et de Grasset’ (101-14) (V. riparia × V. rupestris)]. Differences in CHOs existed between vineyards for all cultivars, and their relationship with propagation success was most evident with ‘Vidal blanc’. Differences were also observed between sites for some cultivars in terms of grafting success and shoot length of grafted vines. Hot water treatment (HWT) of rootstock increased total sugars, glucose, fructose, and stachyose in 3309, and led to lower starch, total CHOs, and higher sucrose in 101-14 when measured immediately following HWT. At time of grafting, HWT 3309 had lower starch sucrose and raffinose, and higher glucose, fructose, and total sugars compared with non-HWT material, whereas HWT 101-14 contained lower total sugars, raffinose, and sucrose and higher stachyose and glucose. Stachyose, raffinose, sucrose, glucose, fructose, and total sugars in scionwood at time of grafting were correlated with propagation success. However, CHOs at time of scionwood collection in February did not correlate to successful propagation. Relationships between scion viability of all cultivars vs. stachyose and total sugars for both rootstocks suggested a possible relationship between these CHO metrics and propagation success. Differences likewise existed between propagation success on rootstocks 3309 and 101-14 on most occasions with 3309 displaying higher percent scion viability and shoot growth. This may be of particular importance in grafting difficult-to-propagate rootstock cultivars.

Pinot gris, Riesling, Cabernet franc and Cabernet Sauvignon from a vineyard in Virgil, Ontario, Canada were subjected by cluster thinning to two crop-level treatments (full crop, half crop), combined with three harvest dates (commercial harvest (T0), three weeks after T0 (T1), six weeks after T0 (T2)) in a randomised experiment in 2011 and 2012, with wines produced from all treatment replicates. We hypothesised that a full crop with substantially delayed harvest date might have a greater impact on wine aroma than reducing crop level. Wine aroma volatile analysis was carried out by GC-MS, with quantification by calibration with analytical standards prepared in model wine. Delayed harvest overcame the effects of crop reduction for almost all volatiles. Pinot gris and Riesling displayed increases in varietal aromas in the T1 and T2 wines, e.g. monoterpenes and norisoprenoids, and in esters, aldehydes and alcohols. Reduced concentrations of volatile acids and green odour compounds (e.g. 1-hexanol) with delayed harvest were also evident. Increases in ethanol were related to increased berry sugars, but higher alcohols did not necessarily increase with harvest date. Crop level had little impact on the sensory properties of these cultivars in both seasons. However, delayed harvest resulted in substantial sensorial changes. Due to these chemical and sensorial effects, delayed harvest is recommended, rather than crop-level reduction, to enhance wine quality in these cultivars. Extended harvest, e.g. T2 treatments, was associated with the production of benzaldehyde, diethyl acetal, and higher concentrations of higher alcohols, e.g. isoamyl alcohol and nonanol, which could be linked to pre-harvest desiccation. GC-MS sample preparation Aroma analysis by GC-MS was carried out in the 2011 and 2012 wines for the four grape cultivars based on Bowen and Reynolds (2012), with adjustments. A 30 mL sample was taken from each wine treatment replicate immediately prior to bottling, and was kept at 4°C in the presence of N 2 inert gas until analysis. In duplicate, 100 μL of an internal standard, prepared with 10 μL of 98% 1-dodecanol (Aldrich; Oakville, ON) in 10 mL of 100% ethyl alcohol (Commercial Alcohols, Brampton, ON), was poured into a 10 mL volumetric flask, followed by the addition of wine to the mark and mixed. The prepared sample was transferred into a 10 mL Gerstel extraction vial. A 10 mm stir bar ("Twister"; Gerstel, Baltimore, MD), coated with polydimethylsiloxane (0.5 mm film thickness), was added to the sample and it was stirred for 1 hr at 1 000 g for extraction at room temperature. After extraction. the stir bar was removed, rinsed with Milli-Q water (Millipore, Bedford, MA), and dried out with lint-free tissue, then placed in a 4 mL amber vial at 4°C until analysis on the same day. The stir bar was then inserted into the extraction glass tube inside the thermal desorption unit (TDU) attached to GC-MS. GC-MS conditions, and conditioning of material An Agilent 6890N/5975B GC-MS equipped with a Gerstel TDU, cooled inject...

Cabernet Sauvignon (CS) and Cabernet franc (CF) vines were subjected to two crop levels (full, half) and three harvest dates (earliest to latest; T0, T1, T2) over two vintages. Wines were analyzed for anthocyanins, phenolics, and proanthocyanidins. Crop level increased CS hue (2011-2012), increased CS pH and reduced CS color intensity (2012), and reduced CF hue (2012). Harvest date had a greater effect than crop level, with many treatment interactions. Half crop (2011) increased three CS anthocyanins plus procyanidin B. Extended harvest increased eight compounds. Quercetin and (+)-catechin decreased in T1. Crop reduction (2012) increased malvidin-3coumarylglucoside and (+)-catechin, but decreased petunidin and delphinidin-3-coumarylglucoside. Harvest date (2012) impacted all but two compounds, with the highest anthocyanin concentrations in T1 wines. Gallic acid, (+)-catechin and resveratrol increased with harvest date, while three phenols decreased. Half crop (2011) increased CF peonidin. Extended harvest increased four phenols while three others decreased. Crop reduction (2012) increased delphinidin-3-acetylglucoside, cyanidin-3-coumarylglucoside and caffeic acid; (−)-epicatechin and p-coumaric acid decreased. Several anthocyanins and phenols decreased between T0 and T2, nine of 13 anthocyanins decreased between T0 and T1, while others decreased from T1 to T2. Gallic acid and (+)-catechin increased with harvest date; (−)-epicatechin, p-coumaric acid, quercetin, and resveratrol decreased.

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Abstract:The polygalacturonase (PGU), hemicellulase (mannanase) and protease enzyme activities in commercial macerating, pectinase-enzyme preparations commonly used by wineries in Ontario (Scottzyme Color X and Color Pro) were measured under various simulated process conditions (temperature, pH, and ethanol concentration). Treatments included three temperatures (15, 20 and 30 • C; pH = 3.0, 3.5, 4.0 and 5.0; ethanol = 0%), four pH levels (3.0, 3.5, 4.0 and 5.0; temperature = 15, 20, 30 and 50 • C; ethanol = 0%), and four ethanol concentrations ((2.5, 5, 7.5 and 10%); temperature = 20 • C and pH = 3.5.) Polygalacturonase enzyme activity in Color X increased linearly with temperature at all pH levels, and increased with pH at all temperature regimes. Polygalacturonase activity decreased with increasing ethanol. Color X mannanase activity increased with temperatures between 15 and 40 • C, and decreased with increased pH between 3.0 and 5.0. Response of mannanase to ethanol was cubic with a sharp decrease between 8 and 10% ethanol. Protease activity increased linearly with temperatures between 20 and 40 • C. These data suggest that the PGU, mannanase and protease components in these enzyme products provide sufficient activities within the ranges of pH, temperature, and ethanol common during the initial stages of red wine fermentations, although low must temperatures (<20 • C) and presence of ethanol would likely lead to sub-optimal enzyme activities.