Objective 1:  Evaluate and select Pinot noir and Cabernet Sauvignon wines that contain various levels of smoke taint.

As detailed in the previous years report more than 120 wines were collected that have various levels of smoke taint. The majority of wines (~100) were Cabernet Sauvignon and Pinot noir, but a few other varietals were also included such as Petit Verdot, Merlot and Syrah. Sensory analysis for these wines were completed in August 2023. We spent 9 months, running weekly sensory panels. This was longer than anticipated but we managed to collect a significant number of smoke impacted wines and did not want to miss the opportunity for larger data set, which can result in stronger causation in the last objective. At the start of each term panelists went through training and they also had retraining after 5 weeks, half way through the 10 week school term. The sensory protocol that was used can be found in Fryer and Tomasino (2022).

Objective 2:  Measure the volatile and nonvolatile chemical composition of the wines from Objective 1.

Measurement of volatile compounds are in progress. We are about half way done with this analysis. The protocol for volatile analysis was adapted from Zhang et al. 2023. We are about 3 months behind on the chemical analysis due to an installation delay with the liquid nitrogen tank used to provide gas to the equeipment and several compounds (utilized as chemical standards) that were back ordered. As of December 2023 analysis was able to recommence. Now that the sample prep for measuring smoke compounds (free volatiles, bound compounds and thiophenols) have been completed the student has started prepping for nonvolatile analysis at the start of January 2023. Free smoke phenols are being measured according to Liu et al. (2020) and bound smoke glycosides according to Caffrey et al. (2019). We are in the process of developing the method to measure the smoke thiophenols. The timeline in the 3rd year grant has been updated to reflect this change in timeline.

Objective 3:  Determine the chemical interactions causing smoke taint perception in Pinot noir and Cabernet Sauvignon wines using fsQCA – this will commence once chemical testing is completed.

Objective 4:  Validate results for fsQGCA using sensory testing – this will commence once chemical testing is completed.

The malolactic fermentation (MLF) is a key process in the production of red wines and some white wines.  While it is commonly conducted after the completion of the alcoholic fermentation (sequential), it can also be induced at the same time where Oenococcus oeni is inoculated shortly after the beginning of alcoholic fermentation (AF).  While a concurrent MLF is typically completed in a shorter time period than a sequential MLF, it is often avoided due to concerns over the production of excess acetic acid, loss of color, and competition with the fermentative yeast Saccharomyces cerevisiae.  Finally, the impact of concurrent MLF on the organoleptic qualities of red wines is relatively unknown and may present an obstacle for the adoption of this practice.  This project addressed some of these concerns and determined the impact of MLF timing on Pinot noir wine chemical and sensory properties.  In addition, the use of non- Saccharomyces yeast during cold soaking and the potential impact on a concurrent MLF was determined.

The timing of MLF inoculation had a significant impact on color with wines produced using a concurrent MLF having lower color density and polymeric pigments.  Interestingly, lower color and polymeric pigment content was only present in concurrent wines that had undergone a cold soak.  While MLF timing affected color, the addition of Torulaspora delbrueckii during cold soaking did not.  For the sequential MLF treatments, there was no difference in color or polymeric pigment content in wines that underwent a cold soak compared to those that did not.  After nine months of aging, the color and polymeric pigment differences present at the end of MLF were no longer present.  Of note was that wines produced with a concurrent MLF increased in color while all other wines saw a reduction in color as is typical during aging.  In addition, all wines increased significantly in their polymeric pigment content.  While all treatments increased in polymeric pigments, the largest increases in polymeric pigment occurred for the three treatments that underwent concurrent MLF.

While measurable color differences in the wines declined during aging, sensory analysis did reveal color differences between some treatments.  Wine produced with a concurrent MLF was noted to be more violet in color than other wines while wine produced with cold soaking + T.delbrueckii + concurrent MLF had higher red intensity.  The more red colored wine was also liked significantly more than the other wines when evaluated in clear glasses.  However, there were no differences in liking when black glasses were used emphasizing the effect of color on liking.  Sensory evaluation also revealed significant differences between the wines in aroma and mouthfeel.  Wines produced without cold soaking had significantly different aroma than those produced with a cold soak, and non-cold soak wines were also significantly different from each other due to MLF timing.  In contrast, timing of MLF did not impact the aroma of the cold soaked wines, whether an addition of T. delbrueckii had been made or not.  Non-cold soaked wines made with a sequential MLF were described as having cedar, fruity, and herbal aromas while those made with a concurrent MLF were described as having spicy, dried fruit, and woody aromas.

Cold soaked wines made with a sequential MLF had dark berry fruit and leather aromas.  For mouthfeel, the major differences were between wines that had T. delbrueckii added and those that did not.  Cold soaked wines with an addition of T. delbrueckii produced wines with desirable mouthfeel characteristics such as smooth, soft, and balanced.

Wines produced in 2023 included an additional variable, the use of Lactiplantibacillus plantarum to conduct MLF.  As was seen with the 2022 wines, the use of T. delbrueckii and/or conducting concurrent MLF had minimal impact on the speed of the alcoholic fermentation.  MLFs conducted by L. plantarum proceeded rapidly due to the higher inoculation rate but those conducted by O. oeni also completed MLF in 14 days or less.  Early analysis of color and phenolic properties shows different color trends between wines produced with concurrent MLFs induced by O. oeni or L. plantarum.  Polymeric pigments  trended higher  in concurrent MLFs with L. plantarum compared to O. oeni, except for concurrent MLF wines with an addition of T. delbrueckii (no cold soak).  Further analysis of these wines will determine which variables are significant as well as any significant interactions between the treatments.

We have successfully extracted and chemically characterized red wine with tannins, as well as the interactions between red wine tannins and salivary proteins by chemical methods. The effect of tannin-protein interactions on friction forces has been introduced. A tribology method has been developed to show an effect of red wine tannin on mouth lubrication. The formation of turbidity had the strongest relationship to the sensory effect of astringency.
This research has successfully chemically characterized tannins and the consequences of their interaction with saliva or proteins. The tribology experiments carried out on the two red wines with different lubricant (saliva or mucin) has also given promising results, and received much attention in the press. The research is continuing with Watrelot and Kuhl.

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.