Investigating Fruitiness Perception in Red and White Wines

This report details activities that occurred from February 2018 – January 2019. The final date of this project is August 2019 and the next 6 months will include completing the last of the sensory panels and combining all data analysis. A final report will be submitted in January 2020. We are still slightly behind on the timeline due to issues detailed in last year’s report and we also had to renew our IRB (human ethics approval) in June 2018. Once the renewal is submitted it is illegal to run sensory tests on the project until approval is given, which was obtained in September 2018. In January 2019 we completed the last of the Pinot noir sensory panels, although we have not yet done data analysis on the January 2019 panel. Also as stated previously, we have not been able to complete any predictive modeling, some initial reviewer comments said that this objective might have been too ambitious in the timeline and after the 1st year we have to agree and have since removed this objective. We plan on working on predictive modeling in the future but this would be after the current grant is completed.

To date we have investigated 80 different compound combinations and their impact to fruit aroma in Pinot noir wine. We have also completed a panel that shows the influences of phenolic content on fruity aromas in Pinot noir and one panel that shows the impact of ethanol content on fruity aroma in Pinot noir. We have 2 potential marker compounds for red fruit aroma in Pinot noir and 4 red fruit solution sets using fsQCA that show the cause of red fruit aroma in Pinot noir. We have also found 5 solution sets for dark fruit aroma in Pinot noir using fsQCA.

We have also investigated 49 compound combinations for fruitiness in white wine. We are still working on using fsQCA to analyze this data. Preliminary results suggest a combination of low thiols and high esters are responsible for tropical fruit aromas, low to no esters are needed for citrus aromas, and esters and terpenes cause pear, peach and apricot aromas.

We will be running the last 4 Pinot gris sensory panels from February2019-June 2019 and completing the final data analysis. We are in the process of writing the first paper for publication and have done 2 presentations at domestic conferences on the analytical data analysis. Spring /Summer 2019 we will be presenting at 4 different international conferences in Europe and have plans for at least 3 more peer-reviewed publications.

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

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

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.

Characterization of Aroma Volatiles and their Glycosidic Precursors in Grapes and Wines

The complex aroma of wine is derived from many sources, with grape-derived components being
responsible for the varietal character. The ability to monitor grape aroma compounds would allow
for better understanding of how vineyard practices and winemaking processes influence the final
volatile composition of the wine. Previously we developed a procedure using GC-MS combined
with solid-phase microextraction (SPME) for profiling the free volatile compounds in grapes and
wines. We also developed a method for monitoring the ‘aroma potential’ of grapes and wines
without the need for initial isolation of the glycoside precursor fraction. However, this method still
depends on indirect measurement of the glycosides and acid or enzymatic hydrolysis is needed to
release the volatile aglycone which can result in artifact formation. In the current project we
validated a novel method using UHPLC-qTOF MS/MS for direct analysis of intact aroma
glycosides in grapes with minimal artifactual changes in composition. Using this method we
tentatively identified 27 monoterpene glycosides including two monoterpene trisaccharide
glycosides, tentatively identified for the first time in any plant. We measured the terpene
glycosides in six cultivars at three maturity time points and demonstrated differential profiles
depending on cultivar and maturity. We also modified the method so that it can be used to monitor
monoterpene glycosides in wines and during winemaking. We have analyzed the glycoside content
during fermentation for wines made in fall 2016 and 2017 with different varieties (Chardonnay,
Merlot, Cabernet Sauvignon) and winemaking/processing methods. Monoterpenyl glycoside
profiles differed between the grapes and the first alcoholic fermentation samples. In red wines,
malonylated monoterpenol glucosides and monoterpenol hexose-pentoses decreased after the
completion of alcoholic fermentation. We also measured the volatile composition of the wines
during fermentation and we have started to relate changes in terpene volatiles to changes in the
glycoside profiles. This work sheds important insight into possible biochemical changes in
glycosylation during grape berry maturation. In addition, this research will allow us to better
understand the effects of viticultural and winemaking practices on grape and wine components
that affect flavor.

Managing Protection of Varietal Aromas From Wine Oxidation

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

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

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?

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

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

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.