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A Conversation With Professor Roger Boulton

The U.C. Davis researcher and teacher discusses outliers, the value of a broad education and his contributions to understanding pH, fermentation curves, co-pigmentation and more
by Jim Gordon
January 22, 2020
Wine Business Monthly recently sat down with professor emeritus Roger Boulton of the University of California, Davis, to explore some of the most important research and teaching projects in which he was involved during his 43 years on the faculty of the Department of Viticulture & Enology.

Boulton will receive the Lifetime Innovator Award during Wine Business Monthly's Innovation + Quality conference Feb. 27. The IQ Advisory Board selected Boulton as the honoree to recognize his dedication to the pursuit of wine quality and his numerous contributions to the industry as a teacher, researcher and winery designer.

The Australia-born and educated Boulton holds bachelor's and doctoral degrees in chemical engineering from the University of Melbourne and has long held a second position in Davis's Department of Chemical Engineering. The following excerpts from the interview touch on Boulton's philosophy of learning as well as several of his concrete contributions to the science of winemaking.

-- Jim Gordon

Q: As a lifelong teacher as well as researcher, how do you describe the difference between knowledge and understanding?

Boulton: A lot of people don't think there's a difference. Actually it's a very big difference. So you can get knowledge off the web, but you certainly can't get understanding. The question is how much knowledge and discussion do you have to have to get the understanding? Some of that understanding comes at an educational institution, when you go out and you gain experiences, it's how to interpret those experiences, which is the understanding. That's not knowledge.

Q: We have heard U.C. Davis criticized for teaching chemistry and micro-biology to would-be winemakers, and not teaching them winemaking. Is that a valid criticism?

Boulton: When it gets back to Davis or people who went to Davis, I usually just say, "I think you missed the bus." If people went there thinking that they're going to get some magical gift, that's a mistake. But that would be the same mistake if I went to any other institution with that false expectation.

Q: You have talked about how the people at Davis and later in international academic circles lifted you. How big a role did those connections and that encouragement play in your life and career?

Boulton: A lot of people say, "What's the secret to your success?" And I'd go back and say, "There is no secret. It's this combination." You can plan and walk down the same paths, but it's not going to get you there because the opportunities weren't available at the same time. Anyone who's gone through and sees the kind of lifting and encouragement from others that I got, they don't take their success to be due to them.

I don't have this self-fulfilling image that I did these great things or I worked really hard to get these things. I did work hard, but that didn't get me where I got to. It was these other things that actually helped me to get to there, almost unconsciously while I'm doing other stuff.

Q: Was it the kind of thing that Malcolm Gladwell describes in his book "Outliers"?

Boulton: I think in the Gladwell book there are several examples like that. As I kept reading through the chapters, I'm going, “I have something just like that. Oh yes. I could have written that chapter.” Again, he's a relatively thoughtful writer, but it seemed that he'd interviewed various people and he was trying to work out what it was. And it wasn't what school they went to. It so happens that University of Melbourne is the best university in Australia. That isn't why I went there. I went there because I lived at home and we couldn't afford to live in an apartment. It was the cheapest and it was local. I couldn't afford to go to Sydney or Adelaide and live independently. I didn't have those resources. Going off to college wasn't an option in my Australian world, so it's back to what was nearby.

Q: How did you come up with the theory that ATPase explains pH in grapes?

Boulton: When I first came, nobody knew why you had a high pH or why you had low pH. They just knew it was different. It turns out that if you do the calculations on the acids, the pH should be 2.2 and the titratable acidity should be 10. Well, it's not. It's 7 and 3.5.

In plants and in grapes, there is an enzyme which takes up potassium from the soil, that takes up potassium from the vascular system of a plant into a berry, and when it does so it spits out a hydrogen ion from acidity. It's swapping. It's losing it, yes, but it's swapping them and the marker of how much it's lost is how much potassium you gained.

The potassium content of a berry is the reason why the pH is not 2.2, it's 3.5, because you've taken all these guys out as you brought this much potassium in. And the titratable acidity isn't 10, it's back to 7 and those extra ones show up as potassiums. When you do the calculations, the answer is, it looks like the amount that we have in potassium is exactly equal to the amount that we've lost that we can't account for. That's one thing.

Then the question is: how on earth could that be because they just don't sit there and swap? That's reading literature on root uptake in wheat and barley, going to seminars in agronomy and hearing people talk about this enzyme called ATPase and how it actually does this. In 1979 I wrote a paper, a hypothesis paper, that you would have this enzyme in grapes and it would change the uptake of roots and it would affect the uptake of potassium in berries and that would determine acidity and pH. That's arithmetic with a bit of physical chemistry and a bit of plant biochemistry on how that could happen for all of those things.

That's not mathematics, that's enzymology, that's a sort of combination of things to explain a phenomenon which was pH.

Q: You basically solved the mystery of pH in berries?

Boulton: The cause. It's the understanding of the cause that leads to the condition. The understanding is why we do research. A lot of people tried to correlate potassium but it's not a linear function, so the correlation doesn't work. But if you do the mathematics in a nonlinear case, you see the pattern. Does that make sense? Anyway, that paper proposed that ATPase would be present in grapevines. It was 20 years before anybody reported ATPase in grapevines and berries.

Q: Is it another way of saying that it's important to do research even if you don't know what it's going to teach you or what problems it may eventually solve?

Boulton: That's right. Doing nothing will get you nowhere. If you made a mistake, you're wrong, but hopefully you'll learn from your mistake. Doing something can't help but improve you if you learn from a mistake. And if you don't make a mistake, then you find the discovery. But doing nothing will guarantee you'll get nowhere.

Q: How did you come to focus on modeling fermentation in your first few years at Davis?

Boulton: There was one other model around except it was for glucose only. Now, we had glucose and fructose, and most of the work on glucose fermentations would have given you maybe 4 percent alcohol. It was about beer, sake, those kinds of fermentation conditions, not wine. It turns out the alcohol content inhibits growth, the levels of the sugars fight with each other.

There were a few features where those models failed when you looked at a grape juice fermentation. Again, you have to actually calculate them to realize what we thought was happening would give you, and that's actually not what we see, so something's missing. Part of it is quantifying what is known in a problem and seeing how much can be accounted for and begging the question, what would be causing the discrepancy?

Usually then you go back and you read more about sugar transporting yeast. Now you want to understand why two sugars are competing. It's like a Black Friday sale: two people trying to get to the door. They actually can't. Or the escape from a fire in a theater. People will jam up and can't get through as quickly as if they all lined up orderly and went through one by one. It's competitive inhibition of sugar transport and ethanol inhibition of growth.

That model was published in 1979. I presented it and nobody asked any questions, and for me that usually means either I explained it perfectly or they didn't get what I was talking about. It was the second one, unfortunately.

The other feature of that was that everybody at the time, including all the books that I'd read, and what I'd learned, was that the cells are still 100 percent viable and they're still finishing up the fermentation. It turns out, at our alcohol strength and the conditions we grow at, in time they start dying off. The latter part of the fermentation is done by a declining, aging population.

That hadn't been understood. The viability, the competition, and the inhibition weren’t in the wine literature, weren’t in the biochemical fermentation literature. Putting them into a mathematical model, now you could take a Brix curve, know how many yeast you put in, know what temperature you're at, and you had a pretty good idea of how that curve was going to play out, and the factors which were causing it to be higher or lower in the way it played out.

Long story short, right now at school we all follow the fermentations automatically and we will run that model. That model will help us understand whether it looks like they're going to struggle, or they're not going to struggle before the fermentations get to the midpoint.

Q: Was it similar detective work to explain co-pigmentation?

Boulton: It's quantifying what we know and being able to use it to understand the problem. That was the case with the color co-pigmentation work, where 30 percent of the color of a young wine couldn't be explained for every wine because when you analyze the pigments and worked out how red they should be, and you looked at the polymer pigment and worked at how red it was, and then you measured the color, they didn't add up. Thirty percent was missing.

Well, it turns out there's one called co-pigmentation. There are a series of compounds which are colorless which, when you put them in mixture with the pigments, they make the pigments deeper in color than you would expect, and more purple in color than you would expect. We only have red pigments, but we have purple wine, young wine. And you've seen young red wine, which doesn't have a lot of these, and you've seen young purple wine, which has lots of these.

And the question is, “Well, but do these compounds have nothing to do with color?” It turns out they do have a lot to do with this bit of the color, and people couldn't understand—they couldn't quantify red wine color. They measured it but they couldn't explain it and the answer is, “Well, there's a gap there.”  What was the cause of that gap? Again, that's physical chemistry, that's reading in other fields, that's learning about fruit pigments and chemistries and phenolics—a lot of other little things to be able to do that. That leads to an assay now where we can split that up.

That's brought a completely different perspective on why you would focus on compounds that have no color, to get better color in red wine. You'd be interested in a great metabolism for these co-factors.

Q: Does that explain why it was traditional to put Viognier with Syrah in the Rhone Valley? Viognier should dilute the color, you'd think.

Boulton: Yeah that's right. There are lots of examples from Chianti where you can have whites in with a blend, with Sangiovese. There are examples in Rhone with Marsanne and Roussanne, with Syrah and others. There are examples with Malbec in Argentina. The point there is you have to have a red grape, which was low in these co-factors and a white grape that had these co-factors, that didn't have pigments. You had to have few enough of them that it didn't dilute, but enough of them to give you a lift.

Q: What mysteries remain unsolved?

Boulton: Oxidation is still a mystery. Redox potential is still a mystery. And in recent times, more work groups tried to quantify oxygen activation. A lot of the oxygen we expose wine to never reacts. It reacts with SO2. But if we didn't have SO2 it wouldn't really react with a whole lot. We get confused by adding oxygen and see it go away in the presence of SO2. And if we didn't have the SO2 where the oxygen would or wouldn't go, it turns out it doesn't go very far because it doesn't matter what the phenolics are. Okay, a lot of people say, “Oh well the amount of oxygen you can have is really the phenolics.” The truth is no, it's not. It's related to the iron content. And if you don't have enough iron, you need the iron to activate the oxygen.

Again, this is the quantification of what we understand, and the gap between what we observe versus what we understand. The other one is redox potential. The redox potential is like the pH. It's a property in the mixture of how things assemble themselves. And in the case of pH it's the acids and how much they want to ionize. Well in the redox potential, it's a few metals and a few compounds they want to interact with, and yet that determines whether bacteria can grow and whether it’s used to produce certain products. Trying to understand what this juice redox potential is and why it is what it is will help us understand why it moves, and what we're trying to do now, which is control it so it doesn't go into areas which give us sulfites for example.

Q: More detective work?

Boulton: All of these things are like a Lego structure. If I gave you the finished Lego structure, most people in the world of chemistry could pull all the pieces apart and put them in the boxes, black and white and pink and blue with yellow and green. And we can count them and quantify them, but we wouldn't know how to put it back together again. The problem that we see with the Lego structure is that we try to often analyze it by how many of what color, but we're missing how they want to assemble themselves.

Q: Does a winemaker have to know all this to make great wine?

Boulton: In the empirical world you don't need to know the answer to make good wine, I'm not suggesting that you do. So the argument is, how many loads of excellent grapes don't end up as excellent wine? We can talk about how great the great ones are, but in a normal distribution, there's going to be some that don't make it. And the question is why don't they? They cost you the same. They had the same initial chemistry and qualities, but for some reason it didn't end up that way. My focus is on how to get those ones back up to where they have their potential. It's attaining full potential, more precisely.

Anyone could do 10 wines, 10 tanks, and select the three best. Anybody could do that. The trouble is what do with the other seven in the business world and if that's a second label and you're a small producer, you don't have space for a second label. Now the question is, well, when is it seven out of 10, or three out of 10 or five out of 10? What's that number that becomes the make or break of your business?


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