The public weighs in on wine science : questions from the ACS Webinar with Susan Ebeler

I just sat in on the ACS Webinar ( or by UC Davis researcher Susan Ebeler on “Wine Science: Designing Wine.  While the content itself was very interesting, most of it was familiar to me as Dr. Ebeler came to give a lecture series to my class in Valencia (as mentioned in this post), what I found particularly fascinating was the stream of questions rolling in from audience members over the course of the hour-long lecture.

The audience consisted of over 1001 participants, from all around the world (Argentina to Poland), and ranged from winemakers to bloggers to researchers to an entire “Chemistry of beer, wine, and bourbon” class.  Thus the questions represent an interesting cross section of what the world wants to know about wine.  What people don’t understand, such as the question wondering if the floral and fruity notes in wine just come from the added flavors, or if there is another source, as well as suggestions that those embedded in the wine world on a day-to-day basis might never have considered.

Dr. Ebeler didn’t have time to respond to most of the questions (something like 180 were posed), but I collected some of the ones that I found particularly intriguing, for one reason or another, whether they were answered or not :

  • “Do you think most of the flavor components in wine have been chemically identified, and can be measured with current GCMS technologies?” – this one Dr. Ebeler was able to get to.  Her response was that we’ve found all the major compounds, and anything else would be trace compounds (such as Rotundone, the compound responsible for the black pepper aromas of syrah) and that finding new compounds will continue to get more difficult as we already have found the ‘easy’ ones.  I don’t disagree with any of what she said here, but I think that it is important to qualify this statement given her description of the complexity of the sensory effects of wine.  Since there is often little correlation between the concentration of a compound and our ability to perceive it, as well as the complex interactions possible between different aromatic and flavor compounds, it is very possible that molecules present in trace quantities could have a significant impact on the perceived flavor, aroma, or even texture of a wine.
  • “I have heard that some people, particularly in Japan, choose their wines based on their GC spectra, what are your thoughts?” – this one she didn’t have time to answer, but I thought it was a particularly interesting comment.  I don’t know if this is indeed the case, though it does ring a bell.  I’d love to know if anyone has more information about this.  If it is true, I think that this is a fascinating use of what most nonscientists would consider a highly complex analytical technique into popular culture, and would really like to know how this came about and the specifics of how it is used.
  • “Has there been any work on transesterification during fermentation, to tailor the finished wine for a specific bouquet?” –   Dr. Ebeler responded that this would likely be too complicated and difficult to target any specific ester, and wasn’t confident that it would be able to reliably give the desired effects.  However, I thought it was a very interesting question, and one that could only come from the mind of a chemist approaching wine from an outside perspective.  I doubt many winemakers or even wine chemists would consider attempting such a reaction on wine, but why not? And ideas like this one, though they may never lead to technological advances in wine, could help us think of processes that already occur in wine in a different light, giving new insight that may lead to new or deepened understanding.
  • “Is there an objective testing mechanism that does not involve subjective human perception?” –  I thought this was a great question to be posed, in terms of how it reflects upon the current scientific paradigm. Why do we feel the need to eliminate ‘subjective human perception’ from the evaluation of a process (tasting wine) that is entirely dependent on human perception, in fact, it IS human perception.  But this is a quest that we are constantly on, how to remove subjectivity from a subjective experience.  This should, I think, cause us to raise our own questions about how science works, where its limits are, and what new approaches/philosophies might be able to help us resolve this quest to understand rigorously a subjective, sensory process.

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