Dr. Ron S. Jackson, Wine Science, Practice pt.2

Ξ May 3rd, 2010 | → 1 Comments | ∇ A Day at a Time, Interviews, Technology, Wine News |

In this second part of three, Dr. Ron S. Jackson gets down to business. Here he discusses subjects both great and small, but all with an endearing charm and wit. He possesses that great teaching skill of measuring the demands of the question for all audiences. Equally at home discussing amines, esters, nematodes, yeast and the life cycle of phylloxera, he can easily shift to marketing strategies and his favorite beer. He is an academic at home in the world. Without further ado…
Part 1 may be read here.
Admin What lives on the surface of a wine grape? I mean the microbiota, especially with respect to wild yeast populations. Just how complex is that micro-universe?
Ron Jackson It is clearly very complex. Most of the organisms that are growing there have a limited effect on the characteristics of the wine. In most instances, if it’s going to have a marked influence, it’s going to be negative. It will not be positive. At least that is how most microbiologists view it. Now, there are some other people who have a different point of view. It’s like Brettanomyces, the yeast. Certain winemakers love it. And my suspicion as to why this is so is that their nose is not particularly sensitive to the off odors. Now, there is a lot of variation between people. If you’re a winemaker with an olfactory capacity that does not detect it, or you become adapted to it, then you don’t really think your wine smells of barnyard manure. To this microbiologist it mostly smells real bad. But some winemakers think it is wonderful. What is one to say?
If the consumer doesn’t reject this odor and the winemaker can sell their wine, then they say that makes their wine distinctive. Well, so be it. Most microbiologists just find it abominable. Certain of these wild yeasts, if they start to grow in the ferment at the beginning, they can produce some pretty unpleasant odors. Now, again, does this add complexity? If the concentrations are low enough, yes, it can add an element of complexity to the wine that it wouldn’t have otherwise. If it gets much higher, if you are sensitive to it, then it simply makes the wine almost undrinkable.
Most of these organisms require oxygen. And, of course, as soon as you crush the grapes and you start getting the fermentation going then the oxygen level goes down to almost undetectable levels. These organisms then cannot grow. Or don’t grow for very long. Then the Saccharomyces cerevisiae starts to grow, produce alcohol, which is toxic to most of these yeasts, so they simply stop growing, under most circumstances. Not all! There is no absolute here.
We’ve talked about Portuguese winemaking approaches before. Whether on the Açores or elsewhere on the mainland, wild or native yeasts populations are almost exclusively used. Would you explain the differences between wild yeasts and S. cerevisiae?
RJ Saccharomyces cerevisiae is there. It definitely is already there. It probably is there as the predominant yeast in the winery. In most places the grapes may come in with very few cells of S. cerevisiae on them. But the winery equipment is covered with S. cerevisiae! Now, when we say “wild” strains, those are kinds of indigenous strains with slight modifications, but there are still the same species. They have slightly different characteristics. Some produce a little bit more ethyl acetate, some produce a little bit more glycerol, things like that; so there are slight differences. If you really select strains then you can markedly affect the character of the wine by the kind of yeast you use to inoculate. This is equally true of the wild versions of S. cerevisiae that actually are occurring in the winery, on the winery equipment, in the fermentation tanks and so on.
I’m asking because I have friends who champion wild yeast fermentations. And I recently came across an article out of Australia about a biodynamic grower who was looking for a legal remedy to stop a brewery from opening nearby because she is afraid that her vineyard would become colonized by a yeast variety that is contrary to her principles. What would be your response and advice to the grower?
RJ Oh, boy! We are really becoming paranoid, I’m afraid! (laughs) Well, I’m sure that person would not consider anything I said to be of any value whatsoever. I’m in the wrong camp. I’m in the enemy camp. So obviously I would be telling her lies! There would be no reason for me to mention anything. But the evidence at the moment is that if you take to pomace from a fermentation, take it out and use it as fertilizer in the field, most of the residual yeasts will die very quickly and you may not be able to detect it in a year’s time. It’s what survives in the winery that’s important. Not what you put out on the vineyard. Sure, it my splash up on to your vine, but S. cerevisiae does not grow well at all outside. It is a really unique organism, specialized to fermentations, and does not grow well on grapes. It does not grow at all well on grapes.
Most breweries are not going to have many yeast cells getting out into the air. At least most breweries that I know of certainly don’t have much floating outside.
So what accounts for the massive die-off of yeast?
RJ The yeast has a comparatively short lifespan. Certainly the ultraviolet radiation from the sun will damage it. Drying will kill individual cells, especially if they are by themselves. Now, if you get a big clump of them, ok, they’re protected inside.
Like something you’d buy from Lallemand.
RJ Sure. You’ve got millions inside, coated; they dried down slowly. They can survive. But once they go onto soil and you get moisture then they will break down. There are microbes in the soil, they will eat the yeast. It’s a food source. So the yeast will be consumed and die fairly quickly. It simply has no place to grow. It will die off. It’s like taking a bunch of seed and tossing them onto dry soil. Leave them there for a year or so and all the seeds are dead. If the yeast does not have a favorable environment to grow then it will die off.
The origin of Saccharomyces cerevisiae seems to be on the exudate of Oak trees. There are a few other related species, but the exudate sap of Oak seems to one of the few places where you can find the progenitor of Saccharomyces cerevisiae. Also included would be acorns. It’s probably from that that the yeast got into fermenting barley and fermenting grapes.
With respect to the effect of smoke taint on grapes in the field, I’ve read some preliminary research that Pine and Eucalyptus trees and other very aromatic plants, like sage, when grown near vineyards that there may be some aromatic component that somehow infuses the grapes, and therefore helps to distinguish the unique character of one vineyard’s wines from another. What is your opinion of that line of thinking?
RJ I think it is a distinct possibility. My question is how many people are able to tell? I would say only a few in 20,000. First we have the problem of establishing that there is a difference, then of recognizing the difference, which is even more complex. Most people won’t be able to do this. So, in essence, it is a tempest in a teapot simply because the vast majority of people would never be able to tell. It is amazing how imprecise human beings are in this realm of distinguishing subtle differences. If you have two shades of color right next to one another, put them together, of course, people can tell that difference. But if you then take them away and bring one back and ask which was the lighter or darker, you’ll find that people cannot make that distinction.
It is the same with two wines. I’ve done it with 5 or 6 wines. It’s one of the most complicated tests for trainees to have any success at. You give them 5 or 6 wines, quite distinct (you don’t want to make it impossible), usually reds. Ask them to write down their comments, how that they may distinguish each wine next time they see it. So then those 6 wines go away. Now 8 wines appear. Tell me which wine is which? And which wines were not originally there? Finally, are any of the wines you tried before present here twice? (laughs) That separates the men from the boys pretty fast! People are just stunned at how poor they are at answering accurately. They then see how much work is ahead for them!
This must be why some wine critics are so leery of double blind wine tastings! Your format would be quite challenging.
RJ It is very, very challenging, and certainly very humbling.
You yourself have written a book on wine tasting and appreciation. How do you approach the subject?
RJ The book is for universities. It’s for courses in wine sensory evaluation. That’s primarily what it’s designed for. Or for industry people who want to set up tastings. For critical tastings the first thing people have to figure out and decide is what do they want to learn from a tasting. Are they looking at it from a strictly quality point of view where is used the standard terms of quality? Or at you looking at from a varietal expression? Regional expression? Stylistic? How well the wines might go with a particular food? So each one of these ways of looking at it will influence how you assess the wine.
Now, from a scientific point of view, if you want to know are wines from region ‘A’ distinguishable, on average, from those from region ‘B’ and ‘C’, then in that case you have descriptors and a ranking, say from 0 to 6, or 1 to 100, and so you have your tasters rank the wines on a set of aroma descriptors. You ask about how much pineapple do you detect, for example, in a given wine. Is it 10 out of 100? Ninety out of 100? Then you take everybody’s results, measure them, do statistical analysis to see if anybody can distinguish any difference in pineapple character in of the wine. Then you can study for consistent patterns. By extension, could you then distinguish wines from regions ‘A’, ‘B’ and ‘C’?
Whether wines were from a cool or warm climate…
RJ That’s right. Or even the different regions of Napa. Northern Napa, central Napa, southern Napa, are there really consistent patterns? Perhaps consistent for the year, but sadly most tastings of this kind are not done over multiple years so as to see whether these patterns tend to remain. Or is it just that climactic change marks where these shifts, these differences appear.
Also relevant would be changes in winemaking style, longer hang time, new oak, various masking elements…
RJ That’s right. Which type of oak, toasting level; was it natural seasoning or was it fired… multiple things that make it terribly complicated and correspondingly very interesting.
What’s always bothered me with a lot of the wine tastings is that one never knows whether a winery uses liquid oak extract, mega purple for mouthfeel and color density, there are all kinds of additives and technological tricks currently available. Or at least they don’t talk about it. Is it possible through sufficient training to distinguish what is a ‘natural’ wine product, in quotes, one with minimal winery intervention, from one which has been so treated?
RJ I would say, humanly, no. Chemically, yes. But humanly, no. I have seen absolutely nothing that would give me any confidence that people, unless there is some hound dog out there, can do it. Certainly the majority of people can’t. It’s just one of those things: that the perception of reality and reality are often markedly different. Most people don’t realize the difference between those two. Often they are afraid to believe themselves and will follow what anybody says, just like sheep.
And the winery that might use such adulterants protects the secret. For the information to get out would significantly alter the perception, shall we say.
RJ You can pretty well tell who is doing what just by looking at the price they charge. (laughs) You simply can’t have a wine produced for about $8 a bottle that has been in French oak! Pricing is an instructive element. Of course, if you charge $50 a bottle that does not necessarily mean you used high priced oak. You could have used oak extract, too, and laughed all the way to the bank that you fooled everybody. You’d at least better have a few oak barrels there for the people who walk into your winery! (laughs)
You could rent them from Hollywood.
RJ That’s right! (laughs)
End of part 2


One Response to ' Dr. Ron S. Jackson, Wine Science, Practice pt.2 '

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  1. Pietro said,

    on May 5th, 2010 at 9:57 am

    Great to see an interview with one of the guys who wrote the book that many of us use as a bench reference in the winemaking world.

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