Transcript
[MUSIC PLAYING]
Wine is just a really fascinating kind
of aspect of microbiology to study.
You're looking at a lot of different microorganisms
together, all kind of interacting together.
You're not necessarily looking at just one
yeast or one bacteria.
You're really looking at how they all get along together
or don't get along together during the fermentation.
So my name is James Osborne.
I'm an associate professor here at Oregon State University
and a core faculty member of the Oregon Wine Research Institute.
There's a lot of different microbes within yeast
or bacteria that can grow during the winemaking process
and can produce a variety of different aroma compounds
and flavor compounds.
Some of those can be quite beneficial to the wine,
like, esters, for example, that can
give some fairly fruity notes.
On the negative side, there's also some aroma compounds
that some of these yeast or bacteria
could produce that may make a wine
smell like a barnyard or a horse's stable or some things
that you don't really want to be smelling in a wine.
And so understanding where those compounds come from
and how to control the growth of organisms
that produce those compounds is really important.
So from the winemakers' point of view, the microbes that
are doing the fermentation are a key component
to the whole process.
Without them, we wouldn't, obviously,
get alcohol from the sugars.
And of course, we wouldn't get all these lovely aromas
and flavor compounds that they are producing.
You can have the Saccharomyces cerevisiae strains of yeast.
And those are kind of the workhorses of the fermentation
industry.
In winemaking, those are the yeast
that are taking the sugars and producing alcohol.
And then there's a whole host of other yeasts
that can come in on the grapes or be naturally
present in the winery.
And we often kind of categorize those
as non-Saccharomyces yeast.
And those yeast, some of them can produce desirable compounds
and flavors and aromas.
And some of them produce undesirable flavors
and compounds.
So one area during the winemaking process
where these non-Saccharomyces yeast may
have quite an influence on the wine's flavor or aroma
is during a technique that winemakers use
called the cold soak.
And cold soaking is just where grapes are,
when they're harvested, red grapes are processed.
But instead of directly being inoculated for fermentation,
those grapes are taken and chilled down at a tank
and held at a cold temperature.
It's thought that by soaking the grapes at a cold temperature
before fermentation starts, you can soak out
maybe some color compounds, maybe some tannin compounds,
and kind of help improve the color or mouth
feel of the wine.
Secondly, winemakers feel that doing a cold soak
impacts the wine's aroma and flavor compounds.
So they have a different wine at the end of the day
if they do a cold soak versus not.
That's what we try to do.
That's what we set up a series of experiments to investigate.
In our research winery, we have this small 100-liter
[? jacketed ?] tanks, where we can chill down to temperatures
that we need them.
So we were able to get pinot noir grapes.
We're able to chill them down to about 8 to 9 degrees Celsius.
And then we were able to perform those cold soaks just like what
would be done in a winery, just on a smaller and more
controlled scale, so we could actually
figure out what was going on.
The first thing we did was during harvest,
we went to a few wineries up at the [INAUDIBLE] valley.
And then we sampled grape samples from beer tanks
and they go into cold soak.
And we took those samples, and we brought them back
to the lab.
And we isolated what yeast were in there.
So we did a number of different methods
to figure out what yeast were in there.
We isolated those yeast.
We identified what those yeast were.
And then we've used those yeasts in a series
of our own experiments here in our research winery.
We made these little vessels that I
like to think of as a giant French press
to do small-scale red wine fermentations where
we could have a submerged cap.
So inside the vessel is a plunger.
You push down, and it submerges the grapes below the juice.
And then as the fermentation occurs,
we don't need to come back or keep
punching those ferments down.
The submerge cap does that for us.
So we use these fermenters for making [INAUDIBLE]..
And that allowed us to look at the specific contributions
of these different yeasts during a cold soak
and how they may affect the final flavors
and aromas of, in this case, a pinot noir wine.
So another really important aspect
of what we do here at the University
and what OWRI is involved in is educating the next generation
of winemakers.
So we're teaching students all about the fundamental sciences
that underpin everything that goes into making wine.
And then we're training them in very practical ways
to be the next winemakers to come on line.
[MUSIC PLAYING]
James Osborne is a microbiologist and researcher with the Oregon Wine Research Institute, based at Oregon State University. His work takes him into the universe of tiny living things — the microorganisms and chemicals that make such a big difference in the quality of wine. Read more about his work (PDF).
Special Thanks to: Bill Boggess, Executive Associate Dean, OSU College of Agricultural Sciences Danielle Gabriel, inspiration for OWRI research video series.
Want to learn more about this topic? Explore more resources from OSU Extension:
Wine, beer, cider and spirits
