Issue link: http://winesandvines.uberflip.com/i/116287
WineEast eugenol, cis-3-hexenol, 1,8-cineole, 3-isobutyl-2-methoxypyrazine (IBMP) and 3-isopropyl-2-methoxypyrazine (IPMP). These latter two compounds are common in Cabernet Franc, Cabernet Sauvignon and Sauvignon Blanc, and are responsible for their green bean and bell pepper characteristics. Quantitative GC-MS confirmed that these compounds were at higher concentrations in non-vinifera wines. In 2010, 3-isobutyl-2-methoxypyrazine (IBMP) and 3-isopropyl2-methoxypyrazine (IPMP) concentrations were measured in accessions of V. riparia, rupestris and cinerea. IBMP concentrations in V. riparia and cinerea were generally above concentrations found in mature V. vinifera, with nine of 14 and six of 10 accessions, respectively, containing >50 pg/g IBMP at harvest (median sugar level: 20.4° Brix), which is considered high. For example, IBMP in 2010 Ontario Cabernet Franc wines ranged from 30 to 76 pg/g, while IPMP ranged from 17 to 36 pg/g (Susanne Kögel, pers. comm.). One V. cinerea accession harvested at 20o Brix contained 353 pg/g IBMP. IPMP was also detectable (>1 pg/g) in seven of 10 V. cinerea accessions, and IBMP and IPMP were modestly correlated across all accessions (r = 0.55, p < 0.05). 1, 1, 6-Trimethyl-1, 2Dihydronaphthalene Vitispirane O ß-Damascenone Norisoprenoid compounds found in Riesling (Meyers et al., ASEV-ES, 2011). Fruit-zone light response curves for sensory compounds in Riesling. We generally think of most aroma compounds as being products of enzymatic reactions and therefore dependent upon berry temperature. However, we also know that compounds such as methoxypyrazines can break down under intense sunlight. This, of course, has implications for canopy management, although optimal cultural influences with respect to cluster exposure timing and intensity have not been established. The work of J.M. Meyers et al. (ASEV-ES 2011) showed that some odor-active compounds in Riesling responded to fruit-zone cluster exposure. To explore the spatio-temporal relationships between fruitzone cluster exposure and chemical concentrations in Riesling berries, correlations were measured among eight odor-active compounds that are well-known to be important for Riesling aroma: [glycosylated tridihydronaphthalene (TDN), β-damascenone, vitispirane, linalool oxide, α-terpineol, 4-vinylguaiacol, vanillin and eugenol], five cluster exposure metrics of varying spatial precision, two sites and two phenological stages in two consecutive seasons. At Site A in 2008, TDN ("petrol") and vitispirane ("flowery") were positively impacted by exposure at fruit set as measured by two metrics of cluster exposure: cluster exposure layer (CEL) or cluster exposure flux availability (CEFA) (TDN: log CEL, r2 = 0.50; vitispirane: CEFA, r2 = 0.45). TDN and β-damascenone (enhances "fruity" in a matrix) positively correlated with CEFA at veraison (r2 = 0.76 and r2 = 0.53, respectively), but these relationships were not as strong at Site A in 2009 or at Site B in both years where fruit was more heavily shaded (average CEFA <0.2). Eugenol ("smoke" M. Crandles, 2010, undergraduate thesis, Brock University O or "spice") negatively correlated with veraison cluster exposure (log CEL, r2 = 0.44), even at low light levels. Relationship of IBMP with 3-isobutyl-2-hydroxypyrazine and removal of IBMP from musts using nonpolar sorbents. Dr. Sacks' program has also placed focus upon ways of reducing methoxypyrazines in wines, with the ultimate goal of lowering vegetal aromas in cultivars such as Cabernet Franc. Controlling final concentrations of the herbaceous-smelling IBMP is of interest to the wine industry not just in New York but elsewhere in the East. Some of this work has focused on canopy management (e.g., basal leaf removal), while other work has taken place on the enological side—and two experiments were performed toward this goal (Sarah Harris et al.; ASEV-ES 2012). In one experiment, the behavior of a likely IBMP precursor, 3-isobutyl-2-hydroxypyrazine (IBHP), was characterized during the growing season. Following development of an improved method for IBHP measurement, IBHP and IBMP were quantified from fruit set to harvest at one site in California's Central Valley and two sites in the Finger Lakes region of New York. IBHP was detectable at the earliest sampling point (four weeks pre-veraison), increased to up to >800 ng/L and started to decrease about two weeks after IBMP decrease began. The highest IBMP was observed at the site with the highest IBHP, suggesting that IBMP accumulation is dependent on IBHP formation. In a second experiment, they investigated the effects of treating must with a nonpolar sorbent (silicone) prior to fermentation. Silicone is a polymer that contains silicon. Food-grade silicone formulations are sold by home-winemaking companies as anti-foaming agents, while aluminosilicates and silicon dioxide are both permitted under North American and EU regulations for de-foaming and clarification. To the best of my knowledge, silicone is not a permitted additive in wines. Treatment of four different musts with silicone pre-fermentation resulted in noteworthy decreases of methoxypyrazines in the final wine (53% to 93%), without affecting the majority of other wine volatiles. This has major implications for producers of varieties such as Cabernet Franc—not just in eastern North America but worldwide. Yeast nutrition Assessment of yeast nutrient supplements, residual nitrogen in wine and amino acid profile in hybrid varieties. If most winemakers are like me, they probably add a fixed amount of diammonium phosphate (DAP) to their must every year and cross their fingers. I don't know many wineries that actually analyze must nitrogen or verify that the amount of DAP added was sufficient. This is the situation addressed in work by Amanda Stewart and Christian Butzke (right) of Purdue University (ASEV-ES 2011). Christian Butzke Yeast-assimilable nitrogen (YAN) is essential for growth and fermentation properties of yeasts. Two main sources of YAN are found in grape juices and musts: α-amino acids and ammonium ions. The Purdue program developed recommendations for YAN based on initial sugar content more than 10 years ago, and these have proven successful in most situations. YAN in juice or must ranges between 40 and 559 mg/L based Win es & Vi n es A PRI L 20 13 93