Enology Notes

This information was originally published as e-mail missives to Virginia vintners.

Back Issues:

Click here for Enology Notes from 2000 (numbers 1-11)
Click here for Enology Notes from 2001 (number 12-35)

Enology Notes from 2002 (numbers 36-67) {Note: the links below take you to a different page}:

  1. Roundtable Meeting Reminder: Cork Quality Control and Microoxygenation Research
  2. Potassium Bitartrate Stability, Winery Planning and Design Manual Available
  3. Bitartrate (Cold Stability)
  4. Viticulture and Enology Interns, Enology Notes vs. Vintners Corner Newsjournals
  5. Canada's VQA
  6. Wood Fermentations and Sur lie Storage of Red Wines
  7. Tannat, Tannat BATF Proposal of Rulemaking, and APM's Scholarship program
  8. Fining Agents, Isinglass and Structural Balance, and Summary of Fining Agent Use
  9. Viticulture and Enology Interns
  10. Gelatin Fining, Virginia Wine Guide, Student Award Winner
  11. Gelatin Fining Agents continued: Alginates, Casein, and Milk
  12. Winemakers Roundtable Meeting June 24 (Sensory Evaluation of Reds, VQA and Remission Phtometry), New Web Site Domain Address, Fining Continued-PVPP
  13. Pre-Harvest Workshop (White Hall Vineyard, August 5, 2002), Norton Round Table, Additional Web Domain
  14. Juice and Wine Analysis Short Course, January 8 and 9, 2003
  15. Maturity Evaluation
  16. Norton Roundtable, Laboratory Service Reminder, New Analytical Technologies, Pre-Harvest Workshop
  17. Out of Office, 80 Virginia Bonded Wineries, Pre-Harvest Workshop, Scholarship Recipient, ASEV-Eastern Section Meeting, Red Wine HACCP-like Plan, Calendar of Up-Coming Programs
  18. Grape Sampling, Asynchronous Berry Development, 2002 Vintage
  19. Uninoculated Yeast Fermentations
  20. Pre-Harvest Workshop, Best Student Paper Award
  21. Practical Considerations and Recommendations for Fermentation, Survey of All Virginia Vineyards
  22. The 2002 season-pH and TA, Sur Lie Storage, HACCP-Like Outline, and Survey
  23. This Year's Aroma/Flavor Potential
  24. The 2002 Vintage and Red Wine Quality; Red Wine HACCP Planning; New - Enology Notes Subject Index
  25. Upcoming Enology Programs - Juice and Wine Analysis Short Course, January 8 and 9, 2003; Red Wine Fermentation with Oak; High Potassium/High pH
  26. Red Wine Phenolic Management; Special Topic in Grape and Wine Analysis: Tannin-Color Measurement and Management Short Course, January 16, 2003; Industry Economics
  27. Red Wine Phenolic Management, continued; Mechanical Harvester Demonstration
  28. Aroma/Flavor and the 2002 Season; Organic Grape Growing; Enology Notes and Vintner's Corner On-Line; Custom Crush
  29. Aroma/Flavor and the 2002 Season, continued; Enology Advisory Committee Formed ; Virginia Winegrowers Advisory Board Progress Reports On-line.
  30. Aroma/Flavor and the 2002 Season, continued; Budget Reduction; Filtration: Absolute
  31. Filtration, continued; Precoating and Body Feeding
  32. Sterile Filtration

Enology Notes #36 January 7, 2002

To: Virginia Vintners

From: Bruce Zoecklein

Subject: Winemaker Roundtable Meetings: Cork Quality Control and Microoxygenation Research, Cork Quality

I will host two Winemaker Roundtable meetings in January:

The subjects will be cork quality and an update on our microoxgenation research. Bruce Scott of Scott Labs will join me for a discussion of the issues related to cork quality. Bruce will review the current body of knowledge with regard to cork taint, discuss the impact on the industry, and what people should be thinking about with regard to corks and cork quality.

I will present and discuss some of our research findings with regard to microoxgenation of red wines.

If you are a commercial Virginia producer, please join us for one of these meetings. Both programs are the same. Note, one begins in the afternoon, the other in the morning. If you plan on attending the morning meeting, bring a bag lunch.

Corks and Wine Quality. Over 50 naturally occuring volatile compounds have been identified in defect-free cork. These include phenolic aldehydes, such as vanillin, phenols, and fatty acid esters, and furans, such as furfural. Cork taint, however, results from the contributions of a relatively small group of volatile metabolites linked by their musty odor and flavor-active properties. These include chloroanisoles, 1-octen-3-one and 1-octen-3-ol, 2-methylisoborneol, and guaiacol.

In the U.S., the incidence of cork taint is reported to range from 0.5% to more than 2%. Whether or not cork exhibits taint upon bottling may depend on its intrinsic structural integrity. Imperfections, such as cracks, increase available surface area for extraction and, therefore, the potential for development of off odors.

How does cork grade impact the incidence of cork taint? One study suggested that more expensive corks show greater incidences of taint, suggesting that these may be stored for special use and, hence, potentially subject to storage-related mold growth.

The primary compound implicated in cork taint is 2,4,6-trichloroanisole (TCA). Its extraordinarily low sensory threshold in wine (reported to be 1.4 ng/L) makes TCA particularly problematic. Other chlorophenols which have very low sensory thresholds may be involved. Additionally, a variety of other compounds have been reported to elicit musty odors in wine. These include guaiacol, geosmin, and 2-methylisoborneol. What all of this means to the winemaker will be discussed at the Roundtable Meeting.

Microoxygenation Research. As reported in previous editions of Enology Notes and the Vintner's Corner (posted on-line at www.fst.vt.edu/zoecklein/index.html), microoxygenation is a process whereby young wines are continuously exposed to oxygen. Oxygen, supplied via a micron-size gas diffuser, catalyzes the oxidation of ethanol to acetaldehyde which acts as bridging agent linking anthocyanins and other phenols. At the Roundtable Meeting I will discuss the results of our research on this process and have wines for evaluation.

Happy Holidays!

Subscription to Enology Notes. All past Enology Notes and Vintner's Corner newsjournals are posted on the Enology-Grape Chemistry Group's web site at: www.fst.vt.edu/zoecklein/index.html. Enology Notes are different in content from this subscription-based Vintner's Corner newsjoural. To be added to the Enology Notes list serve send an email message to bzoeckle@vt.edu with the word "ADD" or "REMOVE" in the subject line.

Dr. Bruce Zoecklein
Associate Professor and Enology Specialist
Head, Enology-Grape Chemistry Group
Department of Food Science and Technology
Virginia Tech, Blacksburg VA 24061
Enology-Grape Chemistry Group Web address: www.fst.vt.edu/zoecklein/index.html

Phone: (540) 231-5325
Fax: (540) 231-9293
E-mail: bzoeckle@vt.edu