Enology – Sensory of Grapes and Wine Session

Surveying U.S Fresh-Market Grape Consumers to Determine Key Attributes and Willingness to Pay

Renee Threlfall,* Margaret Worthington, Melinda Knuth, Di Fang, Wie Yang, Amanda Fleming, Penny Perkins-Veazie, and Mark Hoffmann
*University of Arkansas, 2650 N. Young Ave, Fayetteville, AR, 72704 (rthrelf@uark.edu)

Grapes (genus Vitis) have two subgenera, Vitis and Muscadinia. While Vitis (especially Vitis vinifera) is the backbone of the grape and wine industry, it can be challenging to grow in many U.S. states due to disease susceptibility. Current grape breeding efforts focus on introgressing disease resistance from Muscadinia to Vitis and quality traits from Vitis to Muscadinia, resulting in new wide-hybrid cultivars. In 2023, an online survey was distributed targeting U.S. consumers of fresh-market grapes to assess demographics, purchase habits/intent, and willingness-to-pay (WTP). Consumers were screened based on age (over 18-years-old), residing in the U.S., and purchase of grapes in last 12 months, with a quarter of respondents from each U.S. area (southeast, northeast, northwest, and southwest). For the discrete choice experiment, there were 24 WTP choice sets (bunch grape, muscadine grape, or neither) with five price levels per pound ($2, $3, $4, $5, and $6), flavor (strong or mild), texture (soft or firm/crisp), size (small, medium, or large), seed presence (none or present), and color (purple/black, pink/red, or light/green). Consumers (n = 950) were 51% female, averaged age 45, had income of $95,000, and were mostly white/Caucasian (86%). Consumers purchased fruit from grocery stores (89%), super discount stores (43%), direct from the farm (30%), online (20%), or at health food stores (15%). Consumers ranked fruit attributes from most to least important (freshness, flavor, price, seed presence, texture, color, size, nutritional content, production style, and shopping environment). Consumers were willing to pay more for muscadine grapes ($5.57), firm texture ($1.44), and no seeds present ($3.59), but less for pink/red color ($0.94) or purple/black color ($0.69), and consumers had no preference for fruit size. Results indicated a consumer demand for both bunch and muscadine grapes, preference for firm, green, seedless grapes, and tendency to purchase from traditional fruit purchasing channels.

Funding Support: USDA NIFA Specialty Crop Initiative (SCRI) planning grant team for “Through the Grapevines: Building Research and Extension Potential between Subgenera Vitis and Muscadinia for the U.S. Grape Industry” (Award # 2022-51181-38326)

Danielle Fox | James Harbertson

Comparison of Pre- and Postfermentation Alcohol Manipulation of Cabernet Sauvignon Wines

Danielle Fox and James Harbertson*
*Washington State University, 2710 Crimson Way, Richland, WA, 99354-1671 (jfharbertson@wsu.edu)

Cabernet Sauvignon grapes were harvested at three potential alcohols (11, 13.5, and 16% v/v, ABV) from a vineyard in Sunnyside, Washington in 2018 and 2019. Alcohol was controlled for pre-fermentation by either dilution or chaptalization. At each harvest, the 13.5 and 16.0% ABV wines were dealcoholized to 11 and 13.5% ABV using a pilot-scale dealcoholization (DA). The initial experimental alcohol was treated as the control, the dealcoholized wine the treatment, and the wine sharing the same alcohol target and harvest date as the dealcoholized wine was designated as the negative control. Basic wine chemistry was determined and untargeted solid-phase microextraction gas chromatography-mass spectrometry was used to identify major aroma compounds present. Targeted analysis was performed on various classes of wine aromatics (alcohols, esters, aldehydes, terpenes, pyrazines) informed by the untargeted analysis. Descriptive analysis was performed on the 2019 wines by nine panelists (four males). Three taste, three mouthfeel, five ortho-, and seven retro-nasal aroma attributes were significant. DA had no significant affect on any basic wine chemistry other than the intended alcohol. For all aroma compound classes measured, the negative control and dealcoholized treatments were significantly lower in concentration than the higher ABV controls. Similarly, the retro- and ortho-nasal aroma attributes were rated lower intensity in the negative control and DA treatments than in the higher ABV controls. Generally, the experiment shows that dealcoholization is not absorbing or “scalping” aroma compounds. Instead, the reduction of aroma compounds is due to volatile compound partitioning effects that are directly influenced by ethanol concentration. These results show that wine aromas, and thus wine styles, may be manipulated postfermentation by dealcoholization.

Funding Support: Washington Wine Commission

Effect of Cap Management Protocols on Phenolic Composition, Redox Potential, and Sensory Properties of Pinot noir Wines

Federico Casassa,* Sean Kuster, Grace Putman, Gabriela Rivas, Dallas Parnigoni, Emily Stoffel, James Nelson, and Bob Coleman
*Wine and Viticulture Department, California Polytechnic State University San Luis Obispo (Cal Poly), 1 Grand Avenue, San Luis Obispo, CA, 93407 (lcasassa@calpoly.edu)

Pinot noir wines from the Sta. Rita Hills AVA of California were produced with five contrasting cap management protocols: pump-overs, performed at two full-volumes/day (PO); punch-downs, performed twice/day for 3 min each (PD); no cap management (NoCMgmt); air mixing, at two additions/day (AM); and nitrogen mixing, at two additions/day (NM). Redox potential spikes up to 340 mV were observed during maceration in AM wines. NM wines consistently showed negative mV values with subtle -40 mV spikes during N mixing. Temperature was controlled during fermentation (24 to 28°C), trending 2°C lower in PO wines. Alcoholic fermentation was completed in all wines within 10 days, with a slower rate of total soluble solids depletion in NoCMgmt wines. PO wines had lower alcohol levels (12.76%) than PD wines (13.76%), and acetic acid doubled in AM wines. AM wines showed the lowest levels of acetaldehyde and NoCMgmt the highest. Anthocyanins and tannins were 50% lower, and total phenolics were 44% lower in AM wines. Total polymeric pigment formation was favored in PD wines at 40% higher and 42% higher relative to PO and AM wines, respectively. The tannin, anthocyanin, total phenolic, and chromatic profiles of PD and NM wines were statistically indistinguishable, but lower in NoCMgmt wines, and the lowest in AM wines. An accelerated aging experiment was established by placing the wines in air-tight glass ampoules, then incubating them for five weeks at 38°C. After accelerated aging, alcohol, pH, titratable acidity, acetic acid, tannin, and total phenolics levels were essentially unchanged and consistent with those measured at bottling. Whereas anthocyanins dropped by 70% and polymeric pigments increased by 106% across all wines, the trend described at bottling for these phenolics persisted. Sensory analysis is currently underway. Present results emphasize the well-documented subpar effects of excessive oxygen dissolution, even during alcoholic fermentation, on Pinot noir wines.

Funding Support: Star Lane and Dierberg Vineyards, LLC (Santa Ynez, CA, USA), E. & J. Gallo Winery (Healdsburg, California, USA), and Treasury Wine Estates (St. Helena, California, USA).

Assessing the Effect of Grape Smoke Exposure on Different Red Wine Varietals using Instrumental and Sensory Analysis

Lik Xian Lim, Cristina Medina-Plaza, Ignacio Arías-Perez, Yan Wen, Bishnu Neupane, Larry Lerno, Jean-Xavier Guinard, and Anita Oberholster*
*UC Davis, 595 Hillgard Lane, Department of Viticulture and Enology, Davis, CA, 95616 (aoberholster@ucdavis.edu)

Fresh smoke from wildfires releases volatile phenols (VPs) due to the thermal degradation of wood lignin. VPs are absorbed into grape berries and rapidly glycosylated. Wines made from smoke-affected grapes are characterized as having smoky, medicinal aromas and a retro-nasal ashy aftertaste. Around 15 to 20% of general consumers are anosmic towards the ashy character of smoke. This study investigated the baseline levels of VPs in grapes across seven different red wine varietals spread across California and the sensory differences between the smoke-affected and non-smoke-affected wines using modified descriptive analysis (DA), gas chromatography-mass spectrometry, and liquid chromatography-triple quadrupole tandem mass spectrometry of the free and total VPs, and individual bound glycosides, respectively. The amount of smoke exposure was the largest contributor to smoke impact, but different wine matrices from different locations and varietals were also important in determining the level of perceived smoke impact. Low smoke-affected wines determined by free and total VP concentrations were not significantly different from the non-affected wines when rated by DA. The study also investigated the difference between the sensitivity of experts and non-experts towards smoke. From the same location, smoke-affected and non-smoke-affected wines made from Cabernet Sauvignon, Malbec, and Syrah grapes, respectively, were blended through serial dilutions to achieve wines with different levels of smoke impact. Wines were evaluated using a series of hedonic questions, just-about-right, and check-all-that-apply. The results indicate that experts could determine smoke impact at lower percentages of smoke-affected wine included in the wine blend than non-experts, who only distinguished smoke impact at higher percentages of smoke-affected wine in the wine blend, and thus smoke marker compounds. Research findings from both studies contribute to our understanding of grape smoke exposure and how it affects wine quality as determined by instrumental measurements, wine experts, and non-experts.

Funding Support: Jackson Family Wines, USDA-ARS

Jenna Fryer | Elizabeth Tomasino

The Efficacy of Common Winemaking Practices on Reducing Wildfire-Smoke Flavor Perception in Cabernet Sauvignon Wines

Jenna Fryer and Elizabeth Tomasino*
*Oregon State University, 3051 SW Campus Way, Corvallis, OR, 97331 (elizabeth.tomasino@oregonstate.edu)

With the increasing frequency of wildfires in wine-producing regions around the world, wine producers are looking for strategies to reduce the sensory impact that these fires have on wine. Wines produced from smoke-exposed grapes have been found to have smokey, burnt, and dirty aromas and flavors, along with a distinctive lingering ashy finish. Several mitigation strategies have been studied to determine their level of efficacy in reducing the effect of wildfires on wines, looking at both chemical composition and sensory alterations. This study further evaluated the influences of common winemaking practices on the sensory properties of wildfire-affected wines. Using descriptive analysis of Cabernet Sauvignon wines, blending, carbon fining, SRX resin treatment, oak chips, and differing oak barrel usage were all evaluated. The results indicated that blending did not consistently reduce smoke flavor perception as the percentage of smoke-affected wine in the blend was reduced. The resin treatment showed more promise for reducing smoke flavors than the carbon treatment. For oak, differences based on oak origin were observed, with greater intensities of smoke flavors with French oak than American oak. Finally, this study showed that from a sensory perspective, there was no carryover of smoke flavors from used barrels that previously held smoke-affected wine. Overall, this work showed that common winemaking practices can effectively reduce the effect of wildfire on wines; however, further trials must determine what provides the most benefit for a specific vintage. This work helps increase our knowledge of the sensory alterations that wildfires cause and how widely used winemaking practices affect wine sensory properties. With this knowledge, sensory-guided decisions can be made on what strategies to employ in future wildfire years.

Funding Support: USDA-SCRI grant no. 2021-51181-35862/project accession no. 1027470

8:15 am – 8:35 am	Surveying U.S Fresh-Market Grape Consumers to Determine Key Attributes and Willingness to Pay Renee Threlfall, University of Arkansas, Fayetteville
8:35 am – 8:55 am	Comparison of Pre- and Postfermentation Alcohol Manipulation of Cabernet Sauvignon Wines Danielle Fox, Washington State University, Tri-Cities
8:55 am – 9:15 am	Effect of Cap Management Protocols on Phenolic Composition, Redox Potential, and Sensory Properties of Pinot noir Wines Dallas Parnigoni, California Polytechnic State University, San Luis Obispo
9:15 am – 9:35 am	Assessing the Effect of Grape Smoke Exposure on Different Red Wine Varietals using Instrumental and Sensory Analysis Lik Xian Lim, University of California, Davis
9:35 am – 9:55 am	The Efficacy of Common Winemaking Practices on Reducing Wildfire-Smoke Flavor Perception in Cabernet Sauvignon Wines Elizabeth Tomasino, Oregon State University, Corvallis

Enology – Sensory of Grapes and Wine Session

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Speakers

Renee Threlfall

Danielle Fox

Dallas Parnigoni

Lik-Xian Lim

Elizabeth Tomasino

Moderator

P. Layton Ashmore