Could fruit flies be responsible for the nice smell of most wines? This is a really interesting idea suggested by a research paper just published in scientific journal Ecology Letters. It’s by a New Zealand group, led by Dr Mat Goddard, who have already published some really interesting research on yeast ecology, showing that the wild yeasts completing fermentations in a number of New Zealand regions are local to the vineyard sites, and not escaped commercial strains resident in the winery. The lead author on the paper is Dr Claudia Buser, a postdoctoral researcher in Goddard’s lab.
The authors are looking at the broader ecological idea that niche construction can initiate the evolution of mutualistic interactions, but this work has relevance for wine. What is niche construction? Saccharomyces cerevisiae, the wine yeast, helps to construct an environment that suits it. It likes ripe fruit as a food source, but so do many other organisms. So S. cerevisiae uses alcoholic fermentation, which is a really inefficient way of using the sugar up, but which creates heat and alcohol that makes it a much less inviting environment for others. In particular, bacteria don’t tolerate alcohol the way that this yeast is able to.
But ripe fruits are quite seasonal, and spread far apart, and yeasts have a problem: how do they get to them, considering they are not mobile? The strategy they have evolved is to hitch a ride on insects, and in particular, fruit flies. These flies are attracted to fermenting fruit where yeasts are growing, and they lay their eggs there.
And this study shows that yeasts are actively producing aromatic compounds to lure the flies.
This has answered a question that previously had confused scientists. Why do yeasts go to the bother of producing all these aromatic compounds that we find in wine, when there is an energetic cost involved to them, and seemingly no benefit? It seems that the yeasts benefit because the aromas bring in their ride.
And the flies? They benefit too, because fermenting fruit is a fertile environment for them to lay their eggs in. It seems that the eggs laid in fruit with S. cerevisiae present do better. The most attractive smelling yeasts lure more fruit flies, and both dispersal and egg fertility are both enhanced. This is known in biology as a mutualistic symbiosis.
In the experiments Goddard’s lab undertook, flies were released into a glass tube maze where they could choose among different types of yeast, and these results were replicated in the field, which demonstrated that S. cerevisiae was being carried by 100 times more flies than you’d expect if the flies were randomly recruiting fungi from the environment.
So this raises the strong possibility that we have flies to thank for many of the pleasing aromas of the wines we drink.
11 Comments on Research suggests fruit flies could be responsible for wine’s pleasant aromas
A recent article by a Toronto Star wine critic belittled the appassimento style applied by several Ontario wineries, which included the observation that these wineries were often surrounded by swarms of fruit flies. My thought at the time was that these fruit flies probably knew something that the wine critic didn’t.
But C.cerevisiae isn’t a “wild yeast” is it? So the “wild yeasts” only contribute early on until killed off by alcohol/heat, and it finishes the job. And how does this translate to wine-growing areas with no fruit flies?
This is interesting in that the aromas produced by the otherwise unavailable glycosides cleaved from glucose during fermentation, are part of the “magic” of wine. Wine grapes are actually pretty bland as fresh fruit,and only after fermentation are these wonderful and sometimes “extra-vinous” aromas available to the olfactory. I’ve thought of wine as an “immaculate provision” with the miraculous, simultaneous concentration of sugar and yeast in the same place. Mankind was challenged to preserve the bounty of the grape crop, where it was impossible to consume it all as fresh fruit. I concluded that mother nature had created the conditions for alcoholic fermentation to make the grapevine attractive to human beings. We would them help the species by propagating vineyards wherever we settled, and would choose sites for settlements that would support our needs, including the suitability for grapevine. This study indicated that the evolution of successful yeast included a symbiotic relationship, with the flies to provide locomotion, and the yeasts to provide the decaying fruit for their hosts to feed upon. I guess were all in this complex relationship together!
Thanks for the laymen’s breakdown of very complex work…………. you always simplify complex science…….. wine is lucky to have you.
I hope we don’t have fruit flies in NZ. Vinegar flies maybe?
Damien- that actually made me laugh!
You find me a winegrowing area without fruit flies, and we will entertain your amusing hypothesis.
Any and all *S.* cerevisiae strains (as well as *all* the non-saccharomyces ones) available commercially were found in nature, and cultured up for sale. They are therefore natural, and wild, occurring in many wild ferments- one of the prequel studies to this piece of research found 108 different strains of S. cerevisiae in a wild ferment at Kumeu River winery near Auckland.
Hugh, so if S cerevisiae were originally found in nature and thus natural & wild, why the distinction? The commercial strains are simply provided in a box. It’s curious that the likes of UCDavis teach that any S Cerevisiae found in the ‘wild’ are in fact ‘feral’ having escaped from a winery at some point?
That would explain the 108 in the study you mention, now ‘wild’ but found near a winery?
Damien- what distinction? You will need to expand for that sentence to make sense. It distinguishes itself as one of the ones that is best at producing alcohol, something that humans value, does that answer your question?
Yes, commercial yeast strains come in a box, or in a liquid form. My partner has a patent on a yeast, which was isolated in exactly the same fashion as any other yeast, from samples made from vineyards or wineries. She didn’t manufacture, breed, or engineer it. It’s still a natural organism, present in the “wild” same as every S. cerevisiae that’s peddled.
Kumeu river may have inoculated ferments very early on in their existence, but there’s no way they used 108 different commercial strains. I really don’t get what your argument is here. Yeasts are natural organisms. They are part of the kingdom of fungi. There are ~1200 yeasts that have been classified, though there are probably many more to be discovered, and yes, they have sexual reproduction and evolution, same as any other living thing. There are strains that have been selected and cultivated, but not in the same way as you can take a coupla cows and breed them together. Just doesn’t work like that with yeasts, or fungi generally. There are genetically modified yeasts, but these are confined to a few careful labs around the world, and are not available commercially.
Effectively, the world’s wine science labs and wineries have been populated by yeasts which already existed in nature. Not the other way around. S.cerevisiae is not dominant in the vineyard, in fact it is the rarest of all, and is very hard to find. It is the one that finishes most alcoholic fermentations, for a variety of reasons.
There are PhD theses available which you can read which explain all of this and more, you could start by googling Auckland University Library and wine yeasts- it’s not all available free of charge to the public yet, but certainly there are a number that are.
Hugh, not really an argument I’m trying to start, or continue, here, just the distinction between the “wine” yeast S.cerevisiae being the only one that completes the fermentation to being what we call wine, and the “natural” yeasts which bring alternative aromas/flavours to wine, but not without S.cerevisiae’s help in completing the job.
And rather than being the one that produces alcohol, I thought it was the one that was most tolerant of alcohol, and thus can do the job of continuing the fermentation for longer?
I simply quoted (not necessarily saying they’re right, but know more than me) UCD as saying (as they do) wild yeasts are not to be confused with “feral” wine yeasts (“escapees” from wineries), and that when we’re talking “wild fermentation” that’s commercial yeasts that have gone “wild”.
Furthermore, they say, the fermentation is not conducted by truly wild yeasts, but by “house strains” of Sacchoromyces.
So, to clarify, my argument as you put it, is simply that “wild” fermentation are largely a desire to seperate oneself from “commercial” winemakers who rely on the commercial strains, when in fact they’re pretty much the same thing.
Thus we’re splitting hairs I imagine; there is just 1 yeast that makes wine, and whether it’s introduced by man or found on the grape skins, it’s the fella that does the final job. And after all, according to this study, even the flies prefer S.cerevisiae!
As for Kumeu River, I see they were founded in 1944. Just imagine the complications in yeast fauna in European vineyards that go back a few thousand years before then.
This is all getting a bit complex to follow, so I will quote your text and attempt to reply. You are right this is not “an argument,” this is a discussion based on different arguments.
” “wine” yeast S.cerevisiae being the only one that completes the fermentation to being what we call wine,”
no, it’s not the only one. and there’s not just *one* S.cerevisiae you can (and quite a few wineries do, in Catalonia and California) use S. bayanus strains as an alternative. S.bayanus will ferment wines to dryness, and to a higher alcoholic content than S.cerevisiae, only giving up around 18% ABV. Cava made with S.bayanus are faaaaaarking teeth rattlingly dry. Sometimes stupid Californians end up with cabernet grapes soooooooo ripe, (because in their minds somehow that’s better, and that is not always the case) that they still have residual sugar left at 15-16% when [most] S.cerevisiae just can’t handle it, and seeing noone will buy obviously-sweet Cali cab for US$100+/btl, they add s.bayanus to finish the job, ending up with an even more stupidly over-extracted cartoon wine than they were aiming for, and then adding “jesus units” to bring it back to the 15-16% dry red wine they will bottle. bung in a bit of Mega Purple, too, yum yum.
there are hundreds of different strains of S.cerevisiae.
commercial wineries look at a catalogue, and select one or more, depending on the characteristics they want to enhance or add to the finished product- strains of S.cerevisiae can have quite different effects. it’s not only the group of yeasts that ferments most wines, but also most beers.
” And rather than being the one that produces alcohol, I thought it was the one that was most tolerant of alcohol, and thus can do the job of continuing the fermentation for longer?”
I didn’t say it was the one that produces alcohol. to quote directly, what I said was “It distinguishes itself as one of the ones that is best at producing alcohol,” which is quite different to how you chose to read it! as stated above, S. bayanus is more alcohol tolerant.
“I simply quoted (not necessarily saying they’re right, but know more than me) UCD as saying (as they do) wild yeasts are not to be confused with “feral” wine yeasts (“escapees” from wineries), and that when we’re talking “wild fermentation” that’s commercial yeasts that have gone “wild”.
Furthermore, they say, the fermentation is not conducted by truly wild yeasts, but by “house strains” of Sacchoromyces.”
ok, dunno where you’re reading that from without a link, but it’s not incorrect nor is it incorrect. those commercial strains came from nature. yeast populations in vineyards are complex things.
“So, to clarify, my argument as you put it, is simply that “wild” fermentation are largely a desire to seperate oneself from “commercial” winemakers who rely on the commercial strains, when in fact they’re pretty much the same thing.”
NO, wild fermentations are complex, and involve many strains of S.cerevisiae AS WELL AS many other non-Saccharomyces yeasts, and of course a few bacteria as well, all acting at different stages, in a sequential fermentation.
contrast this against a commercial wine, inoculated with ONE SINGLE STRAIN of S.cerevisiae, after chilling and sulphuring the must to stump the action of anything else present before that takes hold, and basically fermenting the whole thing itself.
how exactly do you think those are essentially the same???
“Thus we’re splitting hairs I imagine; there is just 1 yeast that makes wine,”
NO, there are HUNDREDS of genetically distinct yeasts that make wine. you can make wine by chucking baker’s yeast into a drum of grape juice, cos guess what, that too is ONE of the many, many, many, many strains of S.cerevisiae. once again, S.bayanus does it too. There are others, hybrids between yeast species, and so on.
“and whether it’s introduced by man or found on the grape skins, it’s the fella that does the final job. And after all, according to this study, even the flies prefer S.cerevisiae!”
nothing in the real world is that black and white.
“As for Kumeu River, I see they were founded in 1944. Just imagine the complications in yeast fauna in European vineyards that go back a few thousand years before then.”
most French wineries, and many European wineries, have never used inoculation with commercial yeasts.
yeasts are almost as old as the hills themselves. the yeast populations in NZ and Europe are as old and complex as each other, they pre-date the vineyards, they predate man, even. yeasts are everywhere, they’re on your head, on your crotch, on your feet, on anything that’s not been cleaned with caustic and citric!!!!!!! put a bowl of water and flour in your lounge, hey presto, sourdough starter.
just cos someone stuck a homogenous strain of S.cerevisiae in a box and sold it to someone else, does not mean it was not already present in their own vineyards, it just means that it is a single STRAIN which has been cultured up, which they cannot easily do from their own vineyards without technological expertise and equipment.
Leewenhoek only became aware of micoorganisms a few hundred years ago, and we’ve only known what yeasts are, since Louis Pasteur took his studies further, on the backs of many scientifically inclined individuals in between.
before all that, noone knew it was due to yeasts, it just happened.
the argument about yeast being flora or fauna is for another time. most people agree that fungi are closer to plants than animals, but are in fact neither. they are fungi. most experts will refer to yeast flora in a vineyard.
who new Yeast could cause such debate! – fascinating stuff Jamie, Hugh & Damien