Yeasts are used to manipulate flavour; myth or reality?

All I can think is what a great dissertation problem this would make. Are there any graduate oenology programs looking into this?

...Soapbox moment: Please correct your friends if they say . . . .
'Yeasts add flavor." They do not, any more than bread yeasts flavor your bread....

I generally agree, but with the following exceptions: Yeast autalycis (sp?) in bottle fermented bubblies and when some winemakers choose to leave the wine on the lees for extended periods, even stirring on occasion.

You're correct, Howie. This practice does add a yeast flavor, which may be described as pastry, pie, bread, cookie, Christmas, French toast, etc. What I and others are trying to make clear is that yeasts do not "add" aromas and flavors like violets, cherries, blood, plum, citrus, or Trix. Well, maybe Trix.

Tom, Coturri is a planet with its own star. Some tweaky dudes are lazy, some are just . . . tweaky. Pleasantly, tweaky old souls who march to no drum at all.

Dave, nice link! I remember that article. Written by food scientist/renowned chefs, I thought it a refreshing take on wine and terroir because they didn't have an investment in the philosophy of terroir. Very well done.

First, there is quite a common misunderstanding about what yeasts can do — and what they cannot do. Aromas in wine, chemically spoken, are terpenes, and yeasts definitely cannot create terpenes, period.]

Michael, perhaps this is a result of your stated lack of expertise with English, but terpenes are not the only "aromatic" molecules in wine. Broadly, classed, you have esters, thiols, aromatics (TCA -- hooray!) and terpenes. Terpenes are only produced by plants, so that part of what you say is certainly true, but yeasts can and do produce thiols and esters, and perhaps some aromatics too.

Mark Lipton

Thanks everyone for your contributions. I am learning a lot from this discussion and particularly from Hoke, Mary, Michael and Mark.

However, I am not yet prepared to convict Robinson of sloppy journalism. Let me elaborate.

The effect of the yeast is most apparent when the wine is young, and it fades with even 6 months bottle age. The effect of the yeast is due to its conversion properties--does it run hot or cold, slow or fast, its nutrient requirements, etc. Depending on its performance a yeast may enhance floral properties (even in reds) color, pepper, or tannin.

This is a very important point, which, if true of all yeasts, puts the debate into perspective for wine geeks who age their wine as well as partially invalidating the claims of some of the yeasts' suppliers. Let me, however, say that the first 6 months in bottle is crucial for critical appraisal as well as being the period during which a high proportion of wine is consumed. Mary does, indeed, go on to explain how some critics can be programmed by producers

Like many observers of the wine scene I have been dimly aware of how the wines of the world are starting to taste much more similar, despite the fact that they come from a wider range of geographical sources than ever before. I strongly suspect that the widespread use of a relatively narrow range of commercial yeasts has accentuated this phenomenon.

I am disappointed that Robinson would say something like this, and is apparently earnest. It is complete and utter flapdoodle and unworthy pot-stirring, very disappointing journalism.

First, thank you for teaching me a new word. However, I think that this criticism is unfair as it stands. Robinson precedes and supports the above extract by quoting quite a few examples from the Lallemand catalogue. Here is the relevant passage -

"Lallemand is one of the most important suppliers of commercial yeasts to the wine industry. A look at their catalogue may be reassuring to a nervous winemaker, but as a wine drinker who savours the idea that a wine communicates the unique characteristics of where it was grown, I find it deeply depressing.
The Product positioning (sic) of Enoferm Assmannshausen®, for example, is listed as “for making Pinot Noir and Zinfandel. It is considered a color friendly strain that enhances spicy (clove, nutmeg) and fruity flavours and aromas”. Lalvin CY3079® is designed “for barrel fermented Chardonnay and ageing on lees. Gives rich, full mouthfeel and aromas” while Uvaferm SVG® is designed “to enhance typical Sauvignon character, diminished acidity and with good fermentation kinetics”. This would explain the growing number of wines I have tasted over the past two or three years, while the fashion for leaner Chardonnays has been growing that say Chardonnay on the label but taste eerily like aromatic, crisp Sauvignon Blanc."



I think that these detailed claims need to be rebutted in order to undermine the thrust of Robinson's article. At the same time, it would be useful to rebut the following from Nicolas Joly before we can confirm him as a windbag propagandist -

“Did you know that research has made available, to winemakers, yeasts that generate specific characteristics? Everyone who makes wine knows that if you use BDX in a cabernet you will get intense aromas of red fruit jam and a stronger tannic structure. On the other hand, if you use GRE, you will be favoring aromatic freshness and red fruit flavors. D21 will inhibit herbaceous aromas, and so on… You make exactly the wine you want and not the wine that the soil gives you. So, it is not surprising that all wines now taste the same.”


Finally, here an extract from Lallemand's website, which, with the exception of re-starting stuck fermentations, seem to me to smack of manipulation -

"Specialist yeasts, in addition to their fermentation properties, possess interesting technological and oenological aptitudes which offer winemakers improved control over their alcoholic fermentation objectives: they permit certain varietal aromas to be revealed, extraction of compounds which have an effect on colour preservation, tannins, roundness or volume on the palate, restarting stuck fermentations…"


Any comments, please?

First, there is quite a common misunderstanding about what yeasts can do — and what they cannot do. Aromas in wine, chemically spoken, are terpenes, and yeasts definitely cannot create terpenes, period.]

Michael, perhaps this is a result of your stated lack of expertise with English, but terpenes are not the only "aromatic" molecules in wine. Broadly, classed, you have esters, thiols, aromatics (TCA -- hooray!) and terpenes. Terpenes are only produced by plants, so that part of what you say is certainly true, but yeasts can and do produce thiols and esters, and perhaps some aromatics too.

Mark Lipton

As of this moment, the above scientific exchange seems to say that yeasts can have some influence on flavours.

It's a pity that serious journalists — and I do admire Jancis Robinson, finding her one of the most serious around — sometimes are not aware about simple scientific facts.

Thank you for listening.

It's one of the reasons that make me react negatively to wine critics who have no-to-minimal technical training. It would be much nicer to say nothing rather than to speculate in public, but when you are speculating, make it crystal clear--readers aren't exactly dwelling on every nuance.

Jancis has the qualification MW, which is probably the best in the world for commercial aspects of wine. It surely includes technical and scientific aspects, although these may be somewhat superficial in view of the number of English Arts graduates who are MWs. As to the charge of speculating in public, I think that I deal with that above.

Technology can be abused. So can a lack of technology. There are a number of lazy producers who profess a philosophy of minimalism, and whose wines are filled with VA, brett, unfermented sugars and/or unnecessary sediment. I am not a fan of squeaky-clean wines btw, but both sides of that argument have their extreme examples, don't they?

I agree. But my perhaps jaundiced view of human nature is that, where technology and expertise give the power, a significant amount of abuse is likely to follow. Last week's events in the financial markets give a good illustration of that.

So all in all, I am not yet convinced that yeasts do not play a part in the manipulation and homogenization of taste which is observed by many in today's wines in spite of the increasing geographical diversity.

I don’t doubt the claims that Lallemand makes about their “specialized” yeast strains. However the yeast must be given an “environment” that is very “favorable”. Besides things like temperature, SO2 concentration, pH, and yeast nutrient requirements, the grapes themselves (or the must or juice) must posses certain precursors so that the yeast will interact with them. One can not expect to take a majority of un-ripe red or black grapes (possible balance sugar and acid prior to inoculation) and produce a wine with aromas of ripe red or black fruit just by using a “specialized” yeast strain and giving it favorable temperatures and the required yeast nutrients. The resulting wine will most likely undergo a “healthy” fermentation and might turn out “better” than if a neutral yeast strain or “wild” yeast strain was used to ferment it, but that’s about it.

Salute

First, thank you for teaching me a new word. However, I think that this criticism is unfair as it stands. Robinson precedes and supports the above extract by quoting quite a few examples from the Lallemand catalogue. Here is the relevant passage -

"Lallemand is one of the most important suppliers of commercial yeasts to the wine industry. A look at their catalogue may be reassuring to a nervous winemaker, but as a wine drinker who savours the idea that a wine communicates the unique characteristics of where it was grown, I find it deeply depressing.
The Product positioning (sic) of Enoferm Assmannshausen®, for example, is listed as “for making Pinot Noir and Zinfandel. It is considered a color friendly strain that enhances spicy (clove, nutmeg) and fruity flavours and aromas”. Lalvin CY3079® is designed “for barrel fermented Chardonnay and ageing on lees. Gives rich, full mouthfeel and aromas” while Uvaferm SVG® is designed “to enhance typical Sauvignon character, diminished acidity and with good fermentation kinetics”. This would explain the growing number of wines I have tasted over the past two or three years, while the fashion for leaner Chardonnays has been growing that say Chardonnay on the label but taste eerily like aromatic, crisp Sauvignon Blanc."

I think that these detailed claims need to be rebutted in order to undermine the thrust of Robinson's article.

Tim, it's a huge leap to take a catalog's sales pitch and use it to condemn an industry trend. Correction: what one critic perceives as an unsubstantiated industry trend. As Victorwine points out in some detail, yeasts cannot "create" a wine or even a style. Here is a description of Assmannshausen yeast from Vinquiry catalog, which as you can see is much more accurate in its description, with less vague, hyperbolic sales language:

Useful for Pinot noir and Zinfandel. Long lag time with slow to medium fermentation rate. Optimum fermentation temperature 20° to 30°C reaching 15% (v/v) alcohol. Color in red fermentation is protected and the wine is enhanced with spicy, fruit flavor and aroma. Good strain domination is obtained with this strain if the culture is allowed to develop in about ten percent of the total crush for about 8 hours before final inoculation.

At the same time, it would be useful to rebut the following from Nicolas Joly before we can confirm him as a windbag propagandist

I own Joly's book, have enjoyed reading it more than once and I have heard him speak. He is very passionate about what he does and believes. But he is also a little pampered, intolerant, and suspicious of other views. Plus, you will note that he does not point out in this passage that working with native yeasts also opens the door to brettanomyces and spoilage bacteria, part of "what the soil gives you."

Finally, here an extract from Lallemand's website, which, with the exception of re-starting stuck fermentations, seem to me to smack of manipulation -

I think you're reading an awful lot into what is clearly a sales piece. We buy some Lallemand products, but we prefer the Vinquiry catalog, which as I pointed out above, has less hyperbole. And Scott Labs. Another thing to keep in mind is that Lallemand is a research facility and yeast propagator, so they have an invested interest in wholesaling their products as well as selling direct. And another thing . . . saying that a yeast is "designed for" or "meant for" zinfandel and pinot noir does NOT mean that it creates zin or pinot profiles. It simply means that it has fermentation properties that work well with those varieties. Zin is prone to fast, hot ferments (undesirable) so a slow, cool fermenting yeast is a plus, and the long lag time before starting gives the skins a little more time to soak, therefore releasing more pigment once the fermentation gets underway. A number of other yeasts are also good choices for zin and pinot. Frankly, in practice, AMH is mostly used on sangiovese these days, along with traditional Brunello yeasts.

So all in all, I am not yet convinced that yeasts do not play a part in the manipulation and homogenization of taste which is observed by many in today's wines in spite of the increasing geographical diversity.

If you are convinced, I doubt there is much anyone can say to unconvince you, nor am I at all sure we should try. But I can say, as a producer, as someone who PAYS for these products, and USES these products in real world applications, that they are not powerful nor influential enough to create an entire industry trend. Which is not to say that there are not winemaking interventions that do have a powerful effect. For years I have been trying to point out on these forums that a strong trend to high pH wines--over 4.0!-- (which the critics love, but these wines do not age well) is creating a market of fat, uber-silky behemoths that fade quickly or worse, develop off flavors and aromas. But then, we produce a more classic, high acid style of wine so I also have an agenda and am, in my own way, a windbag propagandist.

For years I have been trying to point out on these forums that a strong trend to high pH wines--over 4.0!-- (which the critics love, but these wines do not age well) is creating a market of fat, uber-silky behemoths that fade quickly or worse, develop off flavors and aromas. But then, we produce a more classic, high acid style of wine so I also have an agenda and am, in my own way, a windbag propagandist.

Yeah, but you've been correct anyway

So all in all, I am not yet convinced that yeasts do not play a part in the manipulation and homogenization of taste which is observed by many in today's wines in spite of the increasing geographical diversity.

If you are convinced, I doubt there is much anyone can say to unconvince you, nor am I at all sure we should try. But I can say, as a producer, as someone who PAYS for these products, and USES these products in real world applications, that they are not powerful nor influential enough to create an entire industry trend.

You should try, Mary. I like to think that I am not impervious to reason, along with many others. (For example, my initial knee-jerk hostility to screwcaps has been largely reversed by discussion on this board, although I think that the case for their use with age-worthy classics is still not proven.) You are very persuasive and the discussion here has gone a long way to set the issue of yeasts into perspective.

And this quote from Victor is particularly interesting -

I don’t doubt the claims that Lallemand makes about their “specialized” yeast strains. However the yeast must be given an “environment” that is very “favorable”. Besides things like temperature, SO2 concentration, pH, and yeast nutrient requirements, the grapes themselves (or the must or juice) must posses certain precursors so that the yeast will interact with them. One can not expect to take a majority of un-ripe red or black grapes (possible balance sugar and acid prior to inoculation) and produce a wine with aromas of ripe red or black fruit just by using a “specialized” yeast strain and giving it favorable temperatures and the required yeast nutrients. The resulting wine will most likely undergo a “healthy” fermentation and might turn out “better” than if a neutral yeast strain or “wild” yeast strain was used to ferment it, but that’s about it.

Salute

This all leaves me feeling that the manipulative potential of yeasts is much less than the extreme claims but also more than nil.

I would love to get the reaction of Jancis, who strikes me as sensible person, to this discussion. However the only way I know of doing that is via her forum, which means subscribing to her Purple Pages at a cost of $ 135. Think of the nice bottles which I could buy for that.

I would love to get the reaction of Jancis, who strikes me as sensible person, to this discussion. However the only way I know of doing that is via her forum

I don't know if she would reply here, but she is easy to contact: http://www.jancisrobinson.com/page/contact_us.html

The main reason why a certain yeast strain is chosen to ferment a given batch of juice or must is because of its fermentation characteristics and properties. As Mary has stated, winemakers are more concerned with things like- temperature tolerance; alcohol tolerance; SO2 tolerance; high, medium, or low H2S producers; lag time (how long it takes the culture to assimilate); “Killer instinct” (will the culture dominate fermentation); slow, medium, or fast fermenter; low, medium, or high foamer; low, medium, or high yeast nutrient requirements; poor, medium, or good flocculation properties (how well it settles), I’m probably missing something.
Scientists are just beginning to identify some of the chemical compounds responsible for certain aromas and flavors in a wine. But as far as understanding the exact mechanism behind its formation, they have a ways to go yet.

Salute

Not being a winemaker I can only post from my own experience. We tasted in the Barossa Valley at the end of 2004 and at one winery we tasted a 2004 Zinfandel from Langhorne Creek that had been fermented with different yeast strains. Stored in French oak the first wine used a Bordeaux yeast and was loaded with rich ripe flavors of blueberries and blackberries. Very well balanced the tannins were just a little hard. The second wine was also from French oak but had seen a Rhone yeast and was completely different. Almost closed to me, others said they detected spice notes including nutmeg. I have not tasted the wines after that.

There is also this. Hentie Swiegers, a molecular biologist at Adelaide's Australian Wine Research Institute, is examining whether selecting the right type of yeast can allow wine makers to create the best aroma for consumer tastes.

Here is Swiegers CV. I have not read any of these papers but some that may be of interest to this foruum are:-

Swiegers, J.H. & I.S. Pretorius. 2005. Yeast modulation of wine flavour. Advances in Applied Microbiology 57:131-175.

Swiegers, J.H. 2005. The role of the wine yeast, Saccharomyces cerevisiae, in the amplification of the Sauvignon blanc varietal aroma. Anchor Yeast Technical Notes, 2005.

King. E., J.H. Swiegers & I.S. Pretorius. 2007. Enhancing Sauvignon Blanc wine aroma through co-inoculated fermentations. Technical Review, No. 167:19-22.

Lilly, M., F.F. Bauer, M.G. Lambrechts, J.H. Swiegers, D. Cozzolino, & I.S. Pretorius. 2006. The effect of increased yeast alcohol acetyltransferase and esterase activity on the flavour profiles of wine and distillates. Yeast 23:641-659.

Cordente, A.G., J.H. Swiegers, F.C. Hegardt, I.S. Pretorius. 2006. Modulating aroma compounds during wine fermentation by manipulating carnitine acetyltransferases in Saccharomyces cerevisiae. FEMS Microbiology Letters 267:159-166

J.H. Swiegers, A. G. Cordente, R. L. Willmott, E. S. King, D.L. Capone, I.L. Francis, I.S. Pretorius. 2007. Development of Flavour-Enhancing Wine Yeast. Proceedings of the thirteenth Australian wine industry technical conference, Adelaide, Australia

Mike

A yeast strain could differ from another strain in many ways. Some might have different fermentation characteristics and properties. (These are the most obvious or apparent differences). Others could have very similar fermentation characteristics and properties but differ in other ways. As Mark L pointed out, during fermentation yeast strains have the ability to release non-aromatic precursors in must or juice to aromatic components such as volatile thiols. They also have the ability to convert these released thiols into aromatic esters. A given yeast strain might be extremely “talented” and be pretty good at doing both tasks. Others might not be as “talented” and might not necessarily be good at both tasks. Because of this the Australian Wine Research Institute (AWRI) has grouped certain yeast strains as being good “releasers” and others as being good “converters”.

Salute

Thanks for that bit of research, Mike.

I can see Dr. Hentie Swiegers (lovely name) being set up as a terroirists' hate figure to be burned in effigy on their bonfires.

It's all about whether one wants one's wine to taste like an agricultural product or something from a confectionery factory or a perfumery lab.

If Dr. Swiegers' research bears fruit, I am sure that some producers will use it with discretion in a way that I will not be able to detect in drinking their products. However, it will also enhance the potential for abuse of technique of the kind can already be tasted in most of the world's mass market wines and in some trophy wines as well.

If Dr. Swiegers' research bears fruit

Pun intended?

My personal conclusion from this interesting discussion is that yeasts CAN alter wine flavours/aromas significantly, but currently the state of the art is a lot less developed than yeast suppliers are claiming. And it seems that journalists are latching onto yeast suppliers hype.

While Jancis seems to draw some rather broad conclusions from her experience of wines getting to taste more similar, she does not seem to have bought into the hype as much as some, e.g. those responsible for the Channel 4 documentary.

Pun intended?

No. Please explain.

My personal conclusion from this interesting discussion is that yeasts CAN alter wine flavours/aromas significantly, but currently the state of the art is a lot less developed than yeast suppliers are claiming. And it seems that journalists are latching onto yeast suppliers hype.

While Jancis seems to draw some rather broad conclusions from her experience of wines getting to taste more similar, she does not seem to have bought into the hype as much as some, e.g. those responsible for the Channel 4 documentary.

I broadly agree, Steve. Yeasts seem to part of an armoury of techniques, if not the main arm, which, if used with tact, can make for better wines but which, if abused, can be highly manipulative usually in the direction of a homogenization of taste profiles.

Pun intended?

No. Please explain.

OK, but puns are never as funny when explained (and mine was not particulary great to start with).

The guy's research was about yeasts giving rise to fruit flavours. Hence if it is successful it would (almost) literally bear fruit.

The guy's research was about yeasts giving rise to fruit flavours. Hence if it is successful it would (almost) literally bear fruit.

I wondered if you meant that. I would then say that the choice of words was partly intentional.

Ah yes, Dr. Hentie Swiegers. Who was very busy promoting himself and his grant in 2005, sending out press releases and photos, and giving radio interviews. (You'll notice nearly all the articles about his grant have the exact same wording--that's because they were lifted directly from his press releases.) He was very good at promoting himself, but we haven't seen any real results from that research--or at least original, earthshaking results. And this summer of 2008 he took a job with a Denmark biotech company.

Between 2005 and 2008 he published only two technical reports in the AWRI journal, and then only as a senior supervisor. One, in 2007, is on co-inoculation, and does not include anything an experienced winemaker doesn't already know. Likewise, from his 2006 report, here are his conclusions from his research on yeast (emphasis mine):

the choice of yeast strain for fermentation offers the
potential to modulate aroma profiles in order to match predetermined specifications
that are dictated by various consumer markets, enhance regional characteristics, or
allow winemakers to more reliably produce wines in their desired style. So, depending
on the desired style of Sauvignon Blanc wine required by the winemaker, different
wine yeast strains can be selected to modulate specific thiol aromas that comprise the
‘tropical’ profile. For example, preference for box tree and passion-fruit aromas would
require a yeast that expresses greater release of 4MMP, while preference for
passion-fruit, grapefruit, gooseberry and guava aromas requires a yeast having the
ability to release greater quantities of 3MH and/or convert 3MH into 3MHA. Therefore,
this study offers prospects for the development of wine yeast starter strains with
optimised thiol-producing capability that could assist winemakers in their effort to
consistently produce wine to definable specifications and styles.

Translation: He narrowed some tropical flavors down to 4MMP, and 3MHA, which already exist in the grapes, had no further ideas on how to get from here to there, and the $8,000 is gone.

Reality: For years, Aus and NZ winemakers have been making different styles of sauvignon blanc for the Australian continent vs. the American and European markets, and have been doing so by using common sense, practical working knowledge of their vineyards and wines, and by tasting and selective blending.

Mary,

We probably should post the whole comment on Swiegers move to industry, viz.

Wine researcher Hentie Swiegers has taken up a new position with the Denmark-based biotech company Chr. Hansen, a leading supplier of cultures, probiotics, enzymes, yeasts and colors to the global food and beverage industries. Prior to taking up the position as the manager of Chr. Hansen's wine group, Swiegers worked for five years with the Australian Wine Research Institute (AWRI) as senior research scientist.

And its probably wise to note that he published 10 times bewteen 2005 and 2008, only two of those articles being reviews - just insert Swiegers JH in the search for bar.

Being a research scientist I'm always intrigued when someone moves to industry especially if it appears that the industry involved is good fit for the work they have been doing in the public arena.

Mike

Thanks, Mike. That's a sweet search engine. I had no idea it could be used for wine-related research. Also, upon re-reading my earlier post, I think my tone comes across as snarky and I did not mean it to. It's just that I feel there is a Chicken Little reaction in the media to these reports from scientists who are studying what causes a wine aroma to be the way it is, so that they can then create GMO yeasts (see Sweiger's #7, so I assume that is what he was attempting?) that might possibly, someday, be used to create amplified aromas through ester management in a somewhat predictable and consistent manner in real life. Maybe. Someday. If they can get winemakers to agree on what aromas they want (:roll: ) so they can then invest money in production of those GMO yeasts. If they will even be legal in most countries, and if they can find a consumer base in wine production willing to be associated with them. And somehow, out of all that iffi-ness, Robinson and others have found a scapegoat for their present boring wine experiences, blaming them on currently existing yeasts, of which there are dozens, all harvested from nature. And many, if not most, producers use different yeasts on their different varieties, and frequently on different vineyard lots, and frequently blend them together along with native yeast fermentations for complexity--so the resulting wines are a yeast soup just like ye wines of auld except without the brett, toxins and bacterial infections which never improved any wine no matter what its pedigree. Just trying to see where the media prophets are coming from on this issue is making my brain tired. One positive thing I have learned from all this is that it shouldn't be difficult to start a rumor that new oak causes cancer.

new oak causes cancer.

Remember - you heard it here first.

new oak causes cancer.

Remember - you heard it here first.

Thanks for the warning, Mary.

More seriously, whilst I enjoy your lampooning of Robinson's article, I am glad that she wrote it as it is thought provoking and has led to an informative debate.

Nothing that I have read here convinces me that this statement in the middle of her article is a serious exaggeration -

"Like many observers of the wine scene I have been dimly aware of how the wines of the world are starting to taste much more similar, despite the fact that they come from a wider range of geographical sources than ever before. I strongly suspect that the widespread use of a relatively narrow range of commercial yeasts has accentuated this phenomenon."


However, her final paragraph is well over the top -

"So, there you have it. Remember that your next glass of wine may owe its character to something unacknowledged that can be every bit as influential as the grapes."


I sent an E-mail with link to the Robinson address provided by Steve but so far have had no acknowledgment.

Here's an interesting aside to this whole yeast thing:

Trapped inside a Lebanese weevil covered in ancient Burmese amber, a tiny colony of bacteria and yeast has lain dormant for up to 45 million years...

from Ancient yeast reborn in modern beer - MSNBC