Effect of grapevine red blotch disease (GRBD) on flavor and flavor precursor formation in the grape and on wine quality

AVF Proj. ID: 2225 / /Cat.:
Primary Investigator(s): Michael Qianby

Two field experiments were established to investigate the effects of grapevine red blotch disease (GRBD) on flavor and flavor precursor formation in the grape berry and on resulting wine quality. The two objectives of the overall study were to 1) investigate the effect of GRBD on grape berry development with a specific focus on flavor and flavor precursor formation; and to 2) investigate the effect of GRBD on wine quality. Both experiments were located in the same vineyard located near the town of Jacksonville, OR. In both experiments, data vines were identified by visual disease symptoms (or lack thereof), and disease status was confirmed using PCR-based assays in Dr. Achala KC’s laboratory at SOREC.

To evaluate the response of flavor and flavor precursor compounds to GRBV infection during berry development (objective 1), clusters from GRBV+ and GRBV- vines were sampled weekly beginning from just before veraison through to commercial harvest. Vine water status, berry growth, and development were also monitored in those plots subjected to different irrigation treatments. Vine water status was monitored by measurements of midday stem water potential (Ψstem). Results showed that there was no significant interaction between irrigation treatment and disease status on Ψstem. However, there were significant effects of irrigation treatment and disease status on Ψstem independently. Berry size (fresh weight; FW) was consistently higher in GRBV+ vines, significant differences in TSS between GRBV+ and GRBV- vines were observed. There were no significant differences in berry pH between vines of different disease status over the entire course of berry development. Berry titratable acidity (TA; g L-1) were lower in GRBV+ fruit. These responses were only observed after veraison, but they are not as consistent. Flavor and flavor precursor analysis in the grapes is underway.

To evaluate the response of wine quality to GRBV infection (Objective 2), replicate wines were produced from field plots under the supervision of Dr. James Osborne using a standard protocol. Wines were analyzed for volatile aroma compounds using  different techniques including headspace-GC-FID, solid-phase microextraction gas chromatography-mass spectrometry (SPME-GC-MS) and stir bar sorptive extraction-gas chromatography-mass spectrometry method (SBSE-GC-MS), stale-isotope compounds were used as internal standards for accurate analysis. Monomeric anthocyanin and total phenolic contents in wine were also analyzed. Results showed that the RB negative wines under irrigation condition have the highest level of monomeric anthocyanin than other three groups. Total phenolic content varies in wines with different irrigation conditions. Fermentation derived aroma compounds did not show any difference between RB+ and RB-, nor free form grape-derived aroma compounds. Since the free form of grape derived aroma compounds only exist in a small portion, and the majority of these compounds exist in the bound form, analysis is underway for the bound form of volatile flavor compounds in the wine.

Investigation of different amelioration techniques to remove smoke taint character from wine

AVF Proj. ID: 2248 / /Cat.:
Primary Investigator(s): Anita Oberholsterby

Research regarding smoke taint has mostly been undertaken in Australia with a focus on vine susceptibility, potential mitigation actions during winemaking to limit smoke taint expression and potential ways to remove smoke taint in the final wines. Thorough review of published smoke taint research indicated large gaps in knowledge and inconsistent results. The objective of the proposed research is to compare all the suggested amelioration techniques using the same wine and follow the changes in free and bound smoke taint compounds before and after treatment as well as with wine aging up to one year. Results from this study will enable us to better advice the wine industry during future smoke events. SPME-GC-MS and UPLC-Q-TOF-MS methods employing stable isotope dilution methodology (SID) have been implemented. Smoke-exposed Cabernet Sauvignon wine was made from Oakville Experimental Station fruit. Wines were treated for one to six weeks with a range of different enzymes (Lafazym AROM, Lyvarome A5, Sumizyme BGA and Zimarom) at two different addition levels (2 and 4 g/hL). Control and enzyme-treated wines (those showing elevated volatile phenols) will be treated with activated charcoal fining, reverse osmosis, Conetech smoke removal technology and molecular imprinted polymers. Those treatments showing a significant decrease in free and/or bound volatile phenols will be evaluated by descriptive analysis.

Managing Protection of Varietal Aromas From Wine Oxidation

AVF Proj. ID: 1820 / /Cat.: ,
Primary Investigator(s): Andrew L. Waterhouseby

In order to investigate the reactions of quinones with unknown nucleophiles to further understand how quinones react in wine. The quinone reaction products are investigated by Q-TOF using 13C6 labels. Since the labeled compound is expensive, we used the unlabeled catechol (12C6) first to determine the levels of 13C6 labels we needed, the incubation time, and the Q-TOF method development. We have set up a list of the products from quinone with the known nucleophiles and optimized the analysis method to maximize the numbers of the detection of these known products. Considering the total amount of catechols, such as caffeic acid, catechin, cyanidin, are around 2g/L for red wines and 0.5g/L for white wines and the expecting detection limit of the product is around 2 mg/L, 0.1g/L quinone was added to wines and the level was confirmed by the trials. The incubation time was also tested and finally chosen as 2 hours.

Chiral Terpenes – Quantitation, Threshold Determination and Sensory Impact on Aromatic White Wines

AVF Proj. ID: 602 / /Cat.: ,
Primary Investigator(s): Elizabeth Tomasinoby

The specific accomplishment of the last year for this project was the development of a quantitative method using MDGC to measure chiral terpenes in white wine. Two hundred and three white wine samples, Pinot Gris and Riesling with diverse residual sugars had been already collected from different places of origin all over the world. Wines were donated from top wine companies from New Zealand, New York, Australia, Germany, Oregon, Washington, France, to name a few. Fifteen chiral mono-terpene compounds were collected from head space solid phase micro-extraction coupled with multidimensional GC-MS with stable dilution isotope quantification analysis. Results for the Pinot Gris wines are presented in this report. In short here were difference sin chiral terpene content between the wines. Additional differentiation was established for place of origin of Pinot Gris wines based on chiral terpene content.

Understanding Pinot Noir Grape and Wine Aroma Composition as a result of changes in Vine Balance, year 1 of a 3

AVF Proj. ID: 562 / /Cat.: ,
Primary Investigator(s): Michael Qianby

Vine balance is important in determining fruit and wine composition. Excessive canopy density is known to produce unbalanced musts, resulting in poor wine quality. In Oregon, crop thinning is normally conducted between fruit set and lag phase to increase the leaf area: fruit weight ratio in order to prevent over cropping, as well as to improve fruit size and composition. Earlier studies have shown that cluster thinning reduces fruit yield and increases the berry weight, soluble solids, and color of table grapes. However, the impacts of the timing and severity of cluster thinning on subsequent berry growth and fruit flavor composition has not been widely investigated. The main objective of the present study was to evaluate such effects in association with grape and wine aroma composition in Pinot noir grapes and wine. Preliminary results indicated that crop thinning had very limited impact on the grape major volatile composition analyzed in 2011 and 2012. However, the composition of other minor and important compounds, such as methoxypyrizes, are still under investigation.

Judging Wine Quality: Do We Need Experts, Consumers or Trained Panelists?

AVF Proj. ID: 523 / /Cat.: ,
Primary Investigator(s): Hildegarde Heymannby

The overall objective is to determine if quality can be reliably evaluated by wine consumers, wine aficionados and/or wine experts and what their quality scores actually mean relative to the intensities of the sensory attributes we get from trained panels, and the liking scores we get from wine consumers. To choose wines with different quality levels we used the judging scores assigned to 27 Cabernet sauvignon wines in the 2012 California State fair judging competition.

At this competition Cabernet wines are divided into 9 regions. Within each region we picked the wine with the highest score (usually a gold medal wines), the wine with the lowest score (a wine that did not medal) and then a wine with a score as close to the mean between the highest and lowest score. The 15 descriptive analysis panelists (10 males, 22-72 years old, average age 37 yrs, median 31 yrs, standard deviation 17 yrs) were recruited from the students, staff and faculty of the Departments of Viticulture & Technology, Food Science & Technology, and Aerospace Engineering. They participated in 6 1-hr training sessions to collect, generate and obtain consensus on 21 aroma, 3 taste and 3 mouthfeel attributes. Their evaluation of the wines, in triplicate will be complete on 2/7/13. The consumer hedonic evaluation, using the 9-point hedonic scale has been scheduled for February 2, 2013 – we are aiming to have about 192 participants and each participant would evaluate 6 wines. Thus each of the 27 wines would be evaluated by 42 or 43 consumers.

Evaluating the Effects of Sterile Membrane and Other Filtration on the Sensory and Chemical Properties of Wine

AVF Proj. ID: 490 / /Cat.: ,
Primary Investigator(s): David E. Block, Roger Boultonby

The goal of our project is to evaluate the effects of sterile membrane and other filtration on the sensory and chemical characteristics of wine. To do this, we have filtered two red wines, a Cabernet Sauvignon and a Merlot, and one white wine blend through 0.45 µm PVDF and PES membrane filters and compared the sensory and chemical characteristics of these wines to unfiltered control wines. Treatments were expanded with the Merlot and white blend to also examine the effects of a pad filter and cartridge depth filter used as prefilters. We have examined changes in dissolved oxygen content, tannin content, and color during the course of filtration and found only minor changes. Sensory panels were trained for each of these wines and each of the treatments evaluated immediately after filtering and then on a regular basis for 9 weeks (for the Cabernet), 24 weeks (for the Merlot), and 20 weeks (for the white blend). While all three wines changed significantly over time in the bottle, very few significant differences were observed in aroma or mouthfeel between filtration treatments. In other words, our results thus far indicate limited impact of sterile filtration on the sensory or chemical properties of the wine, regardless of the type of filter material used. We did observe a small decrease in tannin and astringency with the pad filter for the Merlot wine, but we are continuing to investigate the significance of this change. In addition, we are preparing to evaluate the effects of filtration of both a red and white wine using a cross-flow filter, as well as evaluating the effects of the associated pumps, during the next three months.

Production and Management of Aroma Compounds by

AVF Proj. ID: 450 / /Cat.: ,
Primary Investigator(s): Linda F. Bissonby

The yeast Dekkera/Brettanomyces is commonly found in wines and is responsible for a wide array of characteristic odors. The primary aim of this project is to illuminate the factors that are most important in the survival and growth of Brettanomyces bruxellensis in wine and how these factors influence the production of off odors. The role of growth in wine and defined medium on the metabolic state of Brettanomyces cells was investigated. Three strains were analyzed during growth over 54 days in wine and a defined medium. Differences in the metabolic profile were determined and correlated with each variable, strain and growth medium. Ten Brettanomyces strains for the production of odor active compounds in defined medium with specific substrates added were also analyzed. These ten strains were chosen from approximately 100 Brettanomyces strains that were screened for differences in aroma production. The ten strains were selected for lower levels of odor production both in defined medium and wine. The analysis of the metabolic profile of Brettanomyces in wine and defined medium revealed some expected differences in lipid and carbon metabolism. Unexpected differences in amino acid and nitrogen compounds were also found. Fatty acids and lipids are involved in ethanol tolerance and general stress tolerance. The changes seen in fatty acid metabolism suggest the cells are altering membrane lipids in ways designed to stabilize the membranes under stress conditions. Fatty acids such as isovaleric and isobutyric acid are also involved in off-aroma production so this adaption to stress may be correlated with off-character formation. Proline and urea were uniquely increased in wine-grown cells. The increase in these nitrogen compounds could be due their use as nitrogen sources but proline may play another role as well. Plants and bacteria use proline as an osmoprotectant. It may play a similar stabilizing role in Brettanomyces in wine. An increase in metabolic compounds involved in the use of pentose sugars was also found in wine grown cells. Differences between strains were also observed. Surprisingly there was a consistent and significant trend showing that strain UCD 2091 was different from strains UCD 2082 and UCD 2807 in multiple metabolic pathways.

Metabolic Profiling of Grape and Wine Aromas

AVF Proj. ID: 460 / /Cat.: ,
Primary Investigator(s): Dr. Susan E. Ebeler, Dr. Mark Matthews, Dr. Hildegarde Heymannby

Most aroma compounds exist in grapes as glycosidically bound precursors and the aglycones (‘free’ aroma compounds) are released by enzymatic or acidic hydrolysis during crushing, fermentation and wine aging. We evaluated procedures for measuring the glycosidically bound volatiles using both acid and enzyme hydrolysis conditions followed by analysis of the free volatiles by Headspace Solid-Phase-Microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS). Acid hydrolysis of a mixture of standard compounds at pH 1 and 100º C for 1 hour released 20-60% of the bound volatiles, however, these conditions also resulted in significant degradation (>50%) of the free volatiles. Enzyme hydrolysis was generally more effective at releasing glycosidically bound compounds with minimal artifactual changes in the concentrations of the free volatiles. However, esterase and oxidase activity was still observed resulting in artifactual degradation of the free volatiles. Most previous procedures for evaluating volatile glycosides employ an initial sample preparation step using column chromatography to isolate the glycoside fraction from the grapes prior to hydrolysis and analysis of the free volatiles. We observed that different types of sample preparation columns were not equally effective at retaining the glycosides and no column-type was effective for all the glycosides in our mixture. Using optimized conditions obtained from the previous studies with model systems, we compared direct enzyme hydrolysis of Cabernet Sauvignon and Chardonnay grape homogenates with and without prior isolation of the glycoside fraction. Both procedures resulted in new ‘free’ volatiles. However, results varied depending on the type of treatment. This research is providing important insight into approaches for rapid estimation of ‘aroma potential’ of grapes.

Development of an Enology Outreach Program

AVF Proj. ID: 416 / /Cat.: , ,
Primary Investigator(s): Linda Bissonby

There has been a chronic underinvestment in extension and outreach for the wine industry. The specific goal of this proposal is the development of a comprehensive program for extension and outreach in enology. This comprehensive program includes an interactive web site that will serve both researchers in enology and winery personnel. With the plethora of information sources currently available on the internet, searching effectively and efficiently for pertinent and accurate information has become challenging. This site will function as a means to link researchers across the United States and internationally that have an active program or interest in enology. The aim of the site is to share information within the research and production communities, facilitate collaboration, eliminate unnecessary redundancy, and foster communication on issues of regional, national or global importance. The site was renamed ‘EnologyAccess’ ( http://enologyaccess.org/ ) and launched under this name with an inaugural webinar in August of 2008. In this past year we developed the interactive tools and social networking for the site (ea2) which will be launched in the next couple of months. We are actively migrating content to this site and providing links to extension specialist and researcher websites across the nation and the world. For this site to be more useful we will need to develop a stream of income that will support the site curation. This year we launched one of the signature programs of our new extension center, Wine Flavor 101. The first courses in this series were sold out and we received a response rate on the course questionnaire of over 70%. The surveys provided a wealth of ideas and constructive criticism for the programs which will assure their continued success. As we develop solid income streams we will be able to hire content curators and add more and more content to the site and offer an expanded line of programs. Progress on meeting our goals is slow but steady.