Kimchi: A Song of Salt and Cabbage

What exactly is kimchi and what is the chemistry of its deliciousness? In this episode of Stuff to Blow Your Mind, Robert and Joe explore this spicy, fermented staple of Korean cuisine.

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Episode Transcript

Speaker 1 (00:03):
Welcome to Stuff to Blow Your Mind production of My
Heart Radio. Hey you welcome to Stuff to Blow Your Mind.
My name is Robert Lamb and I'm Joe McCormick, and
it's fermentation day here at the Stuff to Blow Your
Mind podcast. We're gonna be talking about kim she one
of my favorite foods of all time. Uh. And also

(00:26):
later in the episode, just wanted to give you a
heads up. Robert and I are going to chat about
kimchi for a while first, but later on we're gonna
be speaking with a bona fide fermentation expert from a
Tufts fermentation lab. Her name is Dr Esther Miller, and
it sounds like she's got one of the coolest jobs
in the world. Yeah. Given the title we went with

(00:46):
here kim che a song of salt and Cabbage, I
guess it's a missed opportunity for us to have done
some sort of um Wester Ross themed cold open skit
about about kim she Well, I guess the real prince
was promised in the story is the lacto Bacillus bacteria
and and he must come in order to rescue the fermentation,

(01:08):
for the jar is dark and full of spores. That's
pretty good. But of course you know there's some there.
There has to have been some pickling and from and
or fermentation in the west Ro's books, because it seems
like they were always lengthy descriptions of what kind of
foods uh of characters were eating. Yeah, but a lot
of it is I think like a classic Anglo cuisine inspired,

(01:31):
which is is actually very low. Well, I don't want
to be insulting, I would say at least the perception
is that it's relatively low on on spices and and
complex flavors. It tends to be a rather bland cuisine,
kind of focused on grain, meat and dairy. All right,
But then I do we do have to to point
out that, I guess there was beer, there was cheese,

(01:53):
there was bread. And that's one of the reasons that
fermented foods are so fascinating because there there are these
things that we often forget are fermented, like cheese and
bread and chocolate, and then we have these fermented um,
you know, staples of various fermented goods that you're going
to have in your your kitchen. And also some of
the more um elaborate examples. For instance, Uh, there's the kivak,

(02:16):
which is a traditional Inuit food from Greenland in which
little ox These these little birds are caught and then
fermented in a seal skin that's buried beneath rocks. There's
a great feature on this in the documentary series Human
Planet that came out several years back and was at
the time narrated by John Hurt. I gotta admit, as
much as I love fermented foods, I have never tried

(02:37):
that one, and a lot of the fermented foods that
I've never really gotten into, or the various kinds of
fermented meats and dairy products from around the world, which
are extremely common. Though I think fermented vegetable dishes such
as kim she have seen more of an international renaissance
and in recent years. Yeah, I feel like when I
was a kid, I wasn't as exposed to as many

(02:58):
fermented food aside from these obviously fermented foods, you know,
like they I remember being you supposed to sour kraud
but not really digging it for a long time. But
but now, well, you know, is that is that a
good or a bad? Uh? I'm just I'm just so
sorry for your deprived childhood. I mean, I I can
remember loving sour kroud as long as I had. One

(03:20):
of my earliest positive food memories is actually a memory
of eating a half sour pickle. Um. Yeah, I just
I don't know, it's it's always been there for me,
the love of especially like fermented pickled vegetables so good.
I think I just had kind of work up to it,
like some of those strong flavors, Like there was some
sort of German um oh, some sort of purple cabbage

(03:42):
type thing that I also didn't have a real strong
uh attraction to at the time. But all these things
have grown on me today. I love sauer kroud, and
I love kim she. I love exploring the various fermented
veggie or mushroom items you'll find uh in various cuisines.
And my son, who is eight now, he's been pretty
pretty into all things fermented pretty much his whole life,

(04:05):
as long as they're not actually spicy. That's where he
has a little more to struggle. But ultimately, I don't
know how much of this is his nature versus nurture
with him though, Yeah, I wonder about that too, because
for minute vegetables, definitely they can have strong kind of
unfamiliar flavors and aromas that takes him getting used to.
So I would imagine that having a taste for fermented

(04:28):
foods is somewhat learned. Though then again, I wonder if
there could actually be an instinct, or at least a
slight predisposition that humans would have to find certain kinds
of smells and flavors associated with vegetable fermentation appetizing, since
this could be a possible vector to get useful gut
bacteria and other beneficial microbes that I think there's good

(04:49):
evidence that a lot of these good microbes do actually
survive the digestion process and and can help recolonize the
gut with with beneficial bacteria. And then of course having
healthy gut bacteria could provide some kind of survival advantage.
So I wonder it's it's possible. I can imagine that
there's some kind of instinctual predisposition that animals that like

(05:10):
humans could have uh to to find these smells and
flavors appealing. And another thing I would say is that
you can contrast the appealing or at least potentially appealing
smell of fermented foods like kim chi or yogurt with
the smell of food that's rotting due to an unambiguously
unfriendly micro But in these cases, our visceral reaction to

(05:32):
the smell, I think it's much different. It's sort of automatic,
instinctive revulsion. Uh. You know, some people might be grossed
out by the smell of kim chi or sauer kraut.
But I think that negative reaction is qualitatively different than
the like, you know, hot garbage kind of reaction people
have to the smell of like real dangerous spoilage in foods. Yeah,

(05:53):
like the like the actual like dead animal smell which
really connects with us on a on a primal level,
Like when you smell it, you it. You not might
not be able to summon that smell in your head
right now, but it's undeniable when you encounter it. Um
And now I've I've I've read some different things about about,
you know, kids and flavor, just through I think virtue

(06:13):
of of being a parent. I know, there's the the
argument that you know, since a child has a smaller
body and is more susceptible to the dangers of of poisons,
that that they are going to be overly sensitive to
certain strong smells or flavors. UM. And there's also this angle.
I've not done any like full research into it, and
perhaps this would be a topic for the future, but

(06:35):
I know that biopsychologist Julie Manila has researched the topic
a bit regarding uh, you know, uh, whether we're born
with certain food preferences in mind. And she has some
work that shows that food preferences may be developed in
the womb or during very early life. So we're talking

(06:55):
prenatally and postnatally, involving both the amniotic fluid and rest milk.
So if I'm understanding it correctly, the diet of a
child's biological mother can influence the child's taste later on. Yeah,
that would not be surprising to me. I mean, I
think a lot of things from the from the parents
environment can come through to the child like that. Um.

(07:17):
But another thing, you know, I'm thinking about with with
people's taste for fermented foods is that it could be
a psychological framing issue. You know, We've talked before about
the research showing that people you can take the same
smell and that people might find it appealing if you
blindfold them and tell them the smell is coming from
a cheese, but find it disgusting if you blindfold them

(07:38):
and tell them it's coming from a sock. Uh. For
people on a Western diet who are unfamiliar with kim
chie or with other fermented vegetables and find the smell
off putting, it's possible that it's you know, that it's
similar aromas that they would find appealing if they just
had more of a reason to associate them with, say

(07:58):
the idea of vegetables, because like some of the aromas
that come off of kim chi can smell kind of cheesy,
and that's a strange thing to smell coming off of
vegetables if you're not used to it. Yeah, I've I
think I've voiced a similar thing with Durian fruit before.
Durian fruit, of course, is is beloved in many parts
of the world, but sometimes is less appreciated, certainly in

(08:19):
Western circles, and I think part of that is, like
if my my take anyway, is that if you approach
the Durian as being a cheese and not a fruit,
then then that's going to dismantle some of these associations
you you make, because when you take in the aroma
of the Durian fruit. You might think, well, that that
doesn't smell like I expect a fruit to smell. I'm

(08:40):
more accustomed to a really sweet smell with a fruit
or something much milder. But if you approach it thinking cheese,
then I think you're in a better position to enjoy it. Yeah.
I think that's a really good point, and it almost
makes me wonder if there is there a certain kind
of meditation practice that has been honed in order to
ready the mind to exp orient's new flavors and aromas

(09:02):
as pleasurable when you're not used to them. I wonder
if there is such a thing. I think maybe, yeah,
maybe just a general sort of centering of the self
is probably would probably be helpful in those cases. I
do want to point out to the in terms of
Durian fruit, I don't have a lot of experience eating
Durian fruit, so anytime I have encountered it, I am
very much I feel like encountering it as an outsider

(09:24):
to like regular consumption. So I would love to hear
from anyone out there who is, like, you know, grown
up with Durian fruit and how you like, because ultimately
my whole think of it as a cheese and not
a fruit thing that maybe entirely based as well. In
my situation as kind of a Durian outsider, yeah, I
can see that. But obviously, I mean, tastes that were

(09:44):
once unfamiliar to us can become very very central to
our way of experiencing food in the world. I mean,
so I grew up loving pickled vegetables, but I did
not um, I did not grow up with kim chi,
and now kimchi is one of my favorite foods. I mean,
if you you like pin me down and said, like,
you know, uh, if you could only eat one kind
of food the rest of your life, what would it be.

(10:06):
I would try to reach for something like, well, something
that could be served with bonsch on, you know, all
those little dishes like Korean side dishes of various different
vegetable preparations and kimchi and things like that. That's the
bulls eye for me. That's like the best thing, and
it wasn't always there. So like clearly, our orientations about
food can change as we mature or maybe I shouldn't

(10:28):
say mature, just as we go on in life. So
in terms of just fermentation in general. We'll get back
more specifically to kim chi here in a bit, I
was reading a bit about it from fermentation expert sand
Or Cats. I'm sure he's come up in your research
as well. Um uh, you know, often cited and had
written several books on the topic. And our crowd king Yeah,

(10:50):
Cats points out that if you venture into any restaurant
on the planet, if you dig into any cuisine, you're
gonna find products of fermentation. And again this includes more
obvious examples such as you know, the sour crowd and
the kimchi, but it also means bread, cheese, salad, dressing, alcohol, etcetera.
In fact, you know, he contends that it's hard to
get through the day without engaging with a product of fermentation.

(11:13):
All right, so we're naming fairly disparate seeming food items.
I mean, what do bread and cheese and sauerkraud and
kimchi really have in common? What? What? What is it?
What is the core process of fermentation? Well, in a nutshell,
we're talking about the chemical breakdown of a substance by bacteria, yeats,
or other micro organisms, typically involving uh effervescence and the

(11:36):
giving off of heat. Most notably, it enables humans to
preserve food and store it for travel, um or for
you know, for hard times, and as such it was
often vital for human expansion into harsher climates. It's something
a way that you could take your food with you
and it would survive and be edible when you get

(11:57):
to your destination, or allow you to to have food
in a destination that is that is harsher, right. I mean,
one of the big roles of fermentation I think clearly is,
especially the fermentation of vegetables, is preserving vegetable and products
through the winter. Uh. The traditional preparation cycle for kimchi
involves packing it into pots in the autumn that can

(12:18):
be eaten throughout the winter, I guess throughout the rest
of the year, when fresh vegetables would be hard to
come by. So, as is often the case with food traditions,
I think many forms of fermentation, vegetable fermentation likely followed
a path of beginning with a mistake and then moving
to utilitarian innovation as a preservative, but eventually just becoming

(12:39):
a taste preference, becoming something people liked because it's good.
But I also wanted to go back to a note
you had on the idea of effervescence in fermentation. This,
this idea of effervescence or bubbling uh this is actually
one of my favorite things about certain kinds of kim chi.
It's not always like this, but certain kinds of kim
chi not only have these great complex flavors and pleasing crunch,

(13:02):
it sometimes has something you don't find in other solid foods,
which is a palpable taste of carbonation in the mouth.
Sometimes kim che can kind of bubble and fizz and
zing in your mouth while you're chewing on it, the
same way that a sip of a carbonated drink does.
And and this is one thing I really love that

(13:22):
this bubbling property of fermentation is also what creates, of course,
you know the crumb structure, the holes in a loaf
of bread. But these bubbles are gas given off by
the yeast and bread as they metabolize the sugar in
the dough. The effervescent property in uh in kim che,
of course, is the is the ceo to produced by
the bacteria as they break down the sugars in the cabbage.

(13:45):
But this effervescent property of giving off bubbles or gas
was actually probably where the word fermentation comes from. It's
derived ultimately from the Latin word for very, meaning to
boil or to seethe, and ancient Latin speakers probably would
have been able to observe that as grape juice sat
in vats and the natural yeasts turned sugar content into

(14:07):
alcohol to make wine, you would give off bubbles as
if it were somehow boiling without an external heat source.
But anyway, so I was reading about fermentation in a
in a book called the Noma Guide to Fermentation is
written by the staff of the famous Nordic Cuisine restaurant.
But there there are several ways they point out that
you can define fermentation, which are basically all scientifically correct

(14:30):
at different levels of zooming in the first is that
fermentation is the transformation of foods by microorganisms. You let
the microbes do something to the food. The second is
that it's the transformation of foods by enzymes produced by
the micro organisms. Specifically, what they're doing is they're participating
in the chemical breakdown of molecules in the food. So

(14:53):
they're breaking down long starch chains into different pieces of
those chains, getting a little different sugar ers and things.
They're breaking down long protein chains into smaller pieces of
those chains. But then finally they say it is quote
the process by which a micro organism converts sugar into
another substance in the absence of oxygen and uh and

(15:17):
as as we know that, there are different microbes that
are involved in different kinds of fermentation. So for example,
you've got yeast, which is a fungal microbe. It's a
fungus and it's the agent primarily involved in the creation
of bread, but also wine and beer. While the agent
most important to the fermentation of vegetables like cabbage in
sauerkraud and kim chi is lactic acid bacteria. And we'll

(15:39):
get into more detail on that later, but the gist
is that if you take a bunch of vegetables such
as cabbage, doesn't have to be cabbage, but this is
often the vegetable used you put salt on them, they
will kind of whilt down, release water, create a brine
that's salty in nature, and this salt creates an environment
where certain kinds of bacteria that or tolerant of salt

(16:01):
can thrive and overtake other microbes which are less tolerant
of salt, and as they take over these lactic acid
bacteria further drive out other biological contaminants with the byproducts
of their metabolism. In the case of lactic acid bacteria,
as they eat the sugars and the vegetables and the brine,
they excrete lactic acid, which of course is an acid.

(16:23):
It lowers the pH of the brine. It acts as
a preservative, so it inhibits the growth of other microbes,
kind of like if you had added an acid directly,
like if you added vinegar or some of their acid
to pickle your food. Except a major difference is that
the flavors that come out of the bacterial acid production
process are so much more complex and rich than the

(16:45):
sort of one note flavor of a simple dash of vinegar. Now, fermentation,
of course, uh as I think is already coming out,
occurs without human intention all the time. No humans are
required for this, and examples range from the fermentation a
fallen fruit to the inturic fermentation inside a creature's digestive system. Yeah,

(17:05):
and this is actually an evolutionary adaptation. Terreic fermentation is
really interesting. So it is a symbiotic adaptation involving multiple
different species working together, and it's used by many animals,
including ruminant herbivores like sheep and cattle and camels, and
it allows them to survive on a diet of tough,

(17:27):
cellulose riddled plant matter that animals like us simply couldn't digest.
I mean, if you and I go out and eat
a bunch of grass. My dog tries it sometimes, but
I don't think it really helps them all that much.
Um and we we we just would not be able
to get much energy out of it at all. But
there's an advantage to surviving on a diet like this
if you can. Obviously, tough plant matter like grass is abundant,

(17:49):
it's easy to capture, there's lots of it. It doesn't
run or fight back, but it's just hard to get
useful chemical energy out of it. So animals with natural
enteric fermentation and use the help of a cultivated microbiome.
They have chambers in their digestive system specifically for the
microbial breakdown of tough plant matter, and it transforms all

(18:11):
that grass and stuff like that into simple sugars that
can be easily used as energy by the animals. So
it's almost like these room and at herbivores have a
kim chee jar inside their digestive system. But you know,
if you've ever tried to make kim chee at home,
which I am doing right now, one thing you know
is that as the fermentation happens, you either need to

(18:32):
have a ventable lid on the jar that will allow
gas to escape, or you need to burp it frequently.
You need to take the top off and let the
gas out, or pressure can really build up with some
disastrous consequences, which we can talk about at a little
more later. And a similar thing actually goes on with
animals that undergo terreic fermentation because these room and at

(18:53):
herbivores end up having to burp out an awful lot
of byproduct gas, generally methane, and in large enough quantity,
which is generally the case with say cows that are
that are that are raised by humans, that actually adds
up and has an impact on climate. Yeah, that's absolutely right,
And in fact, I know they're ongoing projects to try

(19:15):
to fiddle with that, to say, like, can we actually
get down the level of methane that is exhaled by
these room and herbivores by making certain tweaks to say
their gut microbiota or to there or to exactly what
the sugars in their diet are and things like that.
So that's cows. But when it comes to humans, and
specifically when it comes to the intentional use of fermentation,

(19:37):
of the fermentation process, this is widely considered a Neolithic technology.
We're gonna take a quick break, but when we come back,
we will dive into what we know of the history
of fermentation. Than all right, we're back. So Robert, you
you've teased us about the history of fermentation, saying that

(19:59):
intend channel use of fermentation of foods by humans is
something that goes back to the Stone Age, the Neolithic era, right,
you know, at least uh So. Evidence of fermented beverages
in China, for instance, seemed to date back to the
seventh millennium BC, based on evidence from a Neolithic village
in Henan Province uh and this this evidence revealed a

(20:21):
a fermented mixture of rice, honey and fruit. This was
mentioned in um in a in a paper titled Fermented
Beverages in pre and Protohistoric China from P and A.
S Uh in two thousand four written by A McGovern
at all and then I was also looking at a
two thousand and sixteen study from Adam Bothius in the
Journal of Archaeological Science, and that puts a date on

(20:44):
Scandinavian fermentation evidence to nine thousand, two hundred years ago
during the early Mesolithic. UH. This would have been processed fish,
so the idea here is that they were using something
described as a gutter to ferment fishing and preserving it
for later. The author discovered evidence of this gutter along

(21:05):
with vast quantities of well preserved fish bones to support
this argument, and fermented fish products are actually very common now.
You might not know that you've been consuming them, but
examples include Worcestershire sauce this is a fermented fish product,
or of course, Asian fish sauces nonpla. These are made
by salting fish and then using the extracted liquid that

(21:27):
comes out as the strong, deeply complex salty flavoring agent.
Another example would be an ancient Roman food known as garum,
which was actually in many many ways similar to Asian
fish sauce. So fermented fish products are are actually in
wide use around the world today. You might not always
think about them being the product of rotting fish, but

(21:51):
or you know, controlled rot, but that's what they are. Yeah.
And if you want more on garam and in in
various fish fermentation in products sauces, we did an episode
of Invention about ketchup and and how all this ties
into the history of the product we now know as ketchup. Now.
As for the fermentation of vegetables, that's key to what

(22:12):
we're talking about here with kimchi, and it's believed that
this too came before the agricultural revolution, so before we
were able as humans to harness crop technology to control
uh and manipulate the way crops grow for our benefit,
we harness the power to preserve those goods through fermentation.

(22:33):
This is fascinating and it reminds me of the evidence
that we've discussed previously that the invention of bread probably
predates the invention of agriculture, before wheat and other grains
were staple crops that people grew on purpose. It looks
like we have pretty good evidence that Stone age people's
were harvesting wild grains such as iron corn, wheat, grass,

(22:57):
taking taking those grains and then aching bread out of it.
The evidence we talked about was a paper published in
in p N. A. S. By Iran's oteg we at
all and basically the authors here, we're looking at an
archaeological site in Jordan's that was an ancient cooking site
from about fourteen thousand years ago, when they found matter

(23:19):
that looks very much like bread crumbs there. So these
would be bread, predating the agricultural revolution by thousands of years. Now.
As for kim chi itself, so yeah, we we've already
described it a bit and talked about it a bit.
We're gonna do a little more detail here. There are
a lot of fermentent items out there that we can
compare to kimchi. But Joe, I don't I don't know

(23:40):
if you'd agree with this, but I feel like, in
many ways, there's nothing quite like it. Oh yeah, I mean,
I love for minute vegetables generally, but kimchi is in
a class all of its own. It is a culinary suet. Gennaris. Now, now,
at a very basic level, what we're talking about here
is a traditional side dish of salted and fermented vegetables,
generally something like now a cabbage Korean radish, made with

(24:02):
a varying selection of traditional seasonings. Yeah, a very common
preparation for kimchi would be you take nap a cabbage,
you salt it to begin a wilting process that will
bring water out of it, and then you prepare a
brine or a marinade that will be made out of
a Korean chili flake, often go chu garu, which is
a red chili flake um, and then ginger garlic, often

(24:27):
some kind of fermented fish products such as salted shrimp
or fish sauce uh. And then other other ingredients such
as maybe graded carrots, scallions UM. I might I might
be leaving a few things out here, but but that's
a pretty standard preparation. Now. I was reading about kimchi
in the History of Korean go Chu Go go Chang
and kimchi in the Journal of Ethnic Foods from and

(24:50):
this was by Kwan at All and it points out that,
you know, as you might imagine, fermentation in Korea began
as a means of preserving vegetables, normally the Chinese cabbage,
or MG cabbage as it is known today, It decomposes
at normal temperatures due to the action of micro organisms.
The authors here point out that specifically with with modern
and kim chi, you add red pepper powder containing capsation

(25:13):
to the cabbage, and this suppresses the growth of of
putrifying bacteria and promotes lactic acid bacteria. The micro organisms
here the author's right, grow and change into a form
that humans can consume. Now, the basic process here is
responsible for other key Korean fermented food products as well, uh,
such as a go go chang, uh chion, gook chang,

(25:35):
and doan jang. But one of the key ingredients in
modern kimchi is the go chu, the Korean red pepper. UH.
This powder, which again is involved in arresting putrification and
leads to the production of lactic acid. And there are
different varieties of go go chu. I think they're like
four main categories. Now in terms of when the gochu
peppers become involved in the process, apparently there I was.

(26:00):
I was not really prepared for this, but apparently there's
some back and forth about when they actually enter Korean cuisine. Yeah,
I was surprised to find that there's some kind of controversy.
It's apparently a somewhat contested issue, uh that's infused maybe
with modern political concerns, like when exactly different types of
kim chi came to exist. Yeah, for instance, that Quan

(26:23):
paper that I that I just mentioned uh In that
they contend that quote go chu started to grow on
the Korean peninsula a few billion years ago, and it
is safe to say it is original to Korea. So
that's that is very much um uh in disagreement with
with some of the information we're gonna get to here
in a second, but I wanted to go ahead and

(26:43):
put that out there. There's also apparently an argument that
kim chi is less than a century old, with the
pepper being introduced to Korea via Japan during World War Two,
but this is strongly dismissed in many sources, including a
two thousand fifteen paper by Jaying at All in journal
Ethnic Foods, citing the Chronicle of the Three Kingdoms of
Korea as a as an historical source dating kimchi back

(27:04):
at least fifteen hundred years in Korean culinary tradition. The
argument here is that it it would have been invented
thousands of years ago. Uh and then but we see
it at least some evidence of it fifteen hundred years ago. Yeah,
Based on the historical sources I was reading, it seems
like the most likely thing is that kimchi is definitely

(27:24):
an ancient Korean food, but the introduction of peppers specifically
is more recent, right, Yeah, that seems to be the case.
So you don't you don't need, or you at least
didn't need peppers for kimchi, uh, you know, throughout most
of its history, but then you end up seeing the
introduction of these peppers. I was reading The Colombian Exchange,

(27:44):
A History of Disease, Food and Ideas by Nathan Nunn
and Nancy Kuan, who point out that the peppers used here,
the peppers alone, not the Korean fermentation traditions, etcetera, have
a New World origin. So, uh, these peppers would have
originated in areas of what is today Bolivia and southern Brazil.
From there they traveled into Mesoamerica and the Caribbean before

(28:06):
the arrival of Europeans, who then took it elsewhere. So
along these lines, that's the Korean chili pepper was probably
introduced to Korea in the early sixteenth century, and the
actual kimchi tradition was much older, however, and seems to
have its roots in Chinese pickling. And here's what Jay
bock Park wrote about it in Red Pepper and kim

(28:27):
she in Korea. In the Chili Pepper Institute paper from
nineteen quote, it's thought that kim she may have originated
from Chinese pickles. These pickles were brought to Korea and
were altered into several types of kimchi to suit the
taste of Koreans during the Sheila and Korea dynasties. That's
c Through and cen Through respectively. Uh. Anyway, the author continues, quote,

(28:55):
since red peppers were imported to Korea in the early
part of the seventeenth century, whole bitch kimchi and other
kim she prepared with hot red pepper became popular. Yeah,
and this matches up with everything I was reading. Uh.
And And in fact, while go chugaru, the red pepper
flake is a very important ingredient in some of the
most popular forms of kimchi, I believe there are still

(29:16):
forms of kimchi made that don't involve it, that might
be known as like white kimchi, that might in fact
be more similar to the older tradition that would of
course involve salting the cabbage, It would involve adding flavorings
to the to the brine or the marinade, but would
but but don't bring in the hot peppers. Yeah, so,
I know. I do want to stress though, that we've
only briefly gone over the history here, but obviously we've

(29:39):
touched on various elements that involve colonial and imperial expansion.
So I think it's it's it's obvious why Uh. Sometimes, um,
you know, some of these are very impassioned arguments. Um. Plus,
it seems like it is difficult to overstate just how
important kimchi is in Korean culinary culture. Uh. There's a
two thousand six article on MPR as the Salt titled

(30:02):
how South Korea uses kimchi to connect to the world
and beyond, and it shares the following quote. Kimchi is
not just cabbage salad. It is essential to the culture
of the country. There are hundreds of different varieties of
kimchi and Korea, and about one point five million tons
of it is consumed each year. Even the Korean stock
market reflects this obsession. The Kimchi Index tracks when Napa

(30:26):
cabbage and the twelve other ingredients chili, carrots, radishes, and
anchovies among them, are at their best prices. Yeah, there's
been a pretty concerned effort over the years by the
South Korean government to promote kimchi as a as a
sort of trendy food worldwide. And I can't you know,
I can't say I blame them like that. You've got
you've got this great culinary tradition. Why not use that

(30:48):
to to help in gender love for your culture around
the world. Yeah, yeah, share it with the world. And
that's where you see initiatives like the Kimchi Bus. I
don't know if you ran across articles about this. Um
this was which was support it in some part by
the South Korean government and it, you know, I don't
think it's active right now, but it at least was
traveling around to various countries and spreading traditional Korean food

(31:10):
and kimchi um, you know, very very much spreading the
word of kimchi. It's like an Iowa campaign bus for kimchi,
Like the kimchi is gonna get out and give a
speech now. That article from The Salt It also points
out some other cool facts about about the culture of
kimchi and in related foods. At points out that kim jang,

(31:31):
the tradition of making kimchi, has long been a unifying
tradition amid Korean villages and a sustaining one through periods
of hardship, and that kim jang was even added to
the UNESCO Representative List of the Intangible Cultural Heritage of Humanity,
which is pretty impressive. Absolutely, so again, the kim jang
would be these, uh, these events where people gather together

(31:54):
to make their their pots of kim chi in the
autumn that can be buried for the winter or the
rest of the year. Yeah. Yeah. Based on this article's description,
it seems like, you know, a sort of a community
wide or even cross community kimchi making enterprise, spreading the
labor intensive process out a maide a large group of people.
So it's not just you know, my household is making
kim cheet today. It's no we we as a community,

(32:16):
you know, or even we as you know, as people
are making kim chee today. Well you know, I was
telling you about this the other day actually that, uh,
my experiments in making kimchi at home have been a
solitary project so far. But I can absolutely see how
making kimchi would be a really fun social, family and
friends kind of project. Is something fun to do with

(32:38):
kids because like the kids can maybe work on massaging
the salt into the cabbage and massaging in the marinade
between the leaves, and you can talk while you're doing it.
I mean, it seems like an ideal social food preparation situation. Yeah,
it sounds funn You were mentioning the specific jars you
have for it, and I think we actually have one

(32:59):
of those jars, because I we have some sort of
sauerkraut kit that just hasn't been used yet, you know,
we've been eyeing, and so that might it seems like
that might be usable for this process as well. Oh yeah,
So to further clarify out there, what what I had
been offering to share with Robert was was burp lids
for jars, which I got, which allows you to, you know,

(33:19):
in case you forget about the kimchi you've got going
in the jar. It's not gonna blow the lid off
or anything. It's got a little vent where if the
pressure really builds up inside the CEO two can escape
out the vent. Now, speaking of of pressure, I spaces
this gets right Intoto. The next thing I wanted to
talk about here that I know you were excited about
as well, Joe. Yeah, and that's you have something as

(33:39):
is culturally important as kimchi. UH. This is one of
the reasons that kimchi has gone into space. So in
two thousand eight, South Korea's Uh sillan Ye was selected
to be the country's first astronaut, and the government apparently
had worked nearly a decade to create UH kimchi as
well as other Korean dishes they could potentially be taken

(34:02):
into space that we're space ready UH for just such
an individual. Now, as for why why take kim she
into space? Well, okay, so there are a few different reasons.
So one of them, of course, we again we've touched
on the cultural importance of the dish. If you're sending
an astronaut into space, that is not only a scientific endeavor,
it is you know, it's about you know, national pride
to a large extent, So it makes sense to want

(34:23):
to send something as important as kimch up with them
on an individual level. We've talked about this in the
past concerning space food. You know that this is um.
Going into space is a physically and mentally um you know,
exhausting endeavor. So if you have something meaningful for them
to eat up there, you know, some sort of bit
some sort of food that that not only sustains them

(34:45):
but perhaps reminds them of home, etcetera. Like that's that's
that's a win. So there's been there's always been an
effort to do that with the food that is sent
up with astronauts. But then on top of that, micro
gravity often is often described as us living in microscradic
gravity rather as often described as being in this kind
of state of perpetual nasal blockage, right, because everything is

(35:06):
just kind of you know, without gravity, everything just kind
of moves up and it just floats free. So this
is one of the reasons that it's kind of difficult
to taste food in space, and so you want something
with a strong flavor perhaps spice to it, if you
really want to to to taste anything. And that's one
of the reasons that NASA's shrimp cocktail has apparently been

(35:27):
popular for years, not because people want those you know,
those shrimp that have been kind of stepped on orbit,
but it's that it's the horse radish in the cocktail sauce,
like it has a strong spicy flavor and it can
kind of clear your head a bit, that's right. Yeah,
it opens up those nasal passages. There's there's something there
you can detect as as far as flavor and aroma

(35:47):
goes um. But another thing I wanted to emphasize again, uh,
the idea of a Korean astronaut having access to kim
chi as part of their food in space. This is
not just important because obviously it is part of Korean cuisine,
but that it is such a regular part of traditional
Korean culinary life that um, that kimchi. You know, it's

(36:09):
not unusual for kim chi to be served at basically
every meal on every on a Korean table, right, yeah,
it is. It is the the traditional side dish, so
you know it would be so in a similar sense.
You know, it's like, of course there's ketchup in space
or some version of it, because that is like the
staple of some people's diets, right, Kimchi is very much
the same affair. But the idea of taking kim chi

(36:30):
into space, well, of course a wonderful idea as far
as the flavor and the comfort that that it can provide.
It immediately calls to mind some particular hazards in the
case of kim chi that are not the case with
other foods, because have you ever seen what happens when
there is a sealed jar of kim chi without a
burping lid, and the fermentation gets a little too aggressive,

(36:52):
gets a little frisky. Uh, you should look up video
of this, Robert. And so the microbes inside the fermentation
will produce co O two as they do their business,
and they can produce so much c O two that
they can basically blow the lids off of jars, or
maybe maybe if they don't blow the lid off, when
you open the jar, suddenly it's like when you know,

(37:15):
it's like mintos and a diet coke. It's like spewing
spicy marinate everywhere, and the cabbage puffs up out of
the top like you know, a muffin coming out of
its mold, or like a Yorkshire putting. Uh. It can
it can look really funny. And I've actually read stories
of this being a real problem for people who have
tried transporting kimchi in luggage and airplanes. I don't know

(37:36):
if they let you do that anymore, but this at
least has been a problem for some people. I've read
about it in the past, Like you would take a
jar overseas with you or something, and sometimes the jar
can explode in your luggage and soak everything in spicy,
rotting cabbage water, which is delicious but not really something
you want to fully saturate your underwear. Um that that

(38:00):
that article from the Salt that I mentioned earlier. They
have a little bit more about the about taking kimchi
into space, and they actually talked to youth astronaut about this,
asking you know, what was it like? And the one
thing they point out is that for the kimchee to
go into space, it had to be radiated to kill
all of the micro organisms in it, which he says

(38:21):
left it looking quote so saggy. It looked like it
was a hundred years old. So it apparently, you know,
didn't taste maybe like terrestrial kimchi, but apparently it tasted
it tasted enough like kim chi that it did the job,
you know it um It It packed the you know,
the spicy fermented punch, and it reminded them of home.
So mission accomplished. Well, this is an important point because okay,

(38:45):
so obviously there there are multiple reasons you'd probably want
to kill all of the microbes in the kimchi, and
you'd want to radiate it before you take it into space.
You definitely don't want kimchi blowing the lid off of
its jar inside a space station. That would be Uh,
that could be disastrous, like spills are not good in microgravity.
But anyway, it really emphasizes that that kim chi is

(39:08):
at its core a living product. And you can have
kim chi that's been sterilized. I mean sometimes people sometimes
I cook it before I eat it, especially when it
gets older. You know, you can saute it in a
pan and add as an as an ingredient of things,
and then of course it's fantastic and delicious. But but
at that point it is sterile before cooking it or

(39:28):
before radiating it. If you've just got a jar of
kim chie sitting in your fridge, I mean, this is
a living organism. This, this kim chi that you're eating.
The life goes on within it, and it will even
though the fermentation will be much slowed down by the
temperatures inside a refrigerator. Uh, it is still alive and
things are still happening there. It is still maturing, it

(39:50):
is still evolving as an ecosystem. Absolutely. Now speaking of
that that ecosystem let's bring everything back down from space. Uh,
not only to the Earth, but nder the earth. Because
we've already referenced a few types of fermentation. Uh that
entails burying a vessel or using some sort of a gutter,
you know, made in earth or stone. It's worth noting

(40:11):
that the traditional means of creating kim she also entails burying, uh,
the the container bearing what Michael Pollen in his two
thousand book Cooked described as a child sized earthenware croc.
So I wanted to read just an excerpt from that,
that excellent book, which, by the way, mentions kim she

(40:32):
a lot. So if you if you're looking for, you know,
a really good book about about foods, science and history,
you know, of course always turned to Michael Pollan, but
particularly this book has a lot of kimchi in it.
But here's what he had to say. Quote. Nowadays, pit
fermentation strikes most of us as primitive, strange, and unsanitary.
Yet we think nothing of aging cheese is underground in caves,

(40:55):
which is not so very different? And how different is
a pit fermentation really from fermenting food in a croc
earthenware as it's called, is really just earth once removed,
cleaner and more portable, perhaps, but otherwise the same basic idea.
Even today, Koreans bury their child sized crocs of kimchi
in the backyard in order to maintain the even cool

(41:17):
conditions that the lacto but silly prefer. The earthenware croc
is a good reminder that every ferment is food and
drink stolen or borrowed from the Earth by temporarily diverting
its microbial gravitational pull to our own ends. Everyone knows
who stole the power of fire from the gods for
the benefit of humankind, But who is the prometheus of pickling?

(41:42):
That sounds like a great story to where is? I
would be shocked if there was not some mythical tradition
that had a story of a god giving the gift
of pickling or fermentation to humans. Yeah, it seemed I
hadn't haven't had a chance to look into it. But
I I would assume that some god or another would
have that at least on their their resume, you know.

(42:04):
For Pollen's part, he goes on in this book to think, well, okay, pickling, fermentation,
these are not going to be as as jazzy as
killing animals or um or or certainly creating fire, these
other acts of early human endeavor that were so important.
But there's still there are others, including sand or cats.
We mentioned earlier who has apparently put it on par

(42:26):
with fire in our history, saying like like pickling, um fermentation. Uh,
these processes are up there with our fire technology in
terms of their importance to our our our history. Well, yeah,
I would say, especially if you go with Remember we
talked previously about the importance of bread in the development

(42:47):
of human civilization because of the kinds of nutrition that
it could provide relative to its own ingredients raw. And
of course fermentation is an important part of many bread
so there are also unleavened breads. But you know, yeah,
so I think it's there at the heart. I don't
know if it's quite at the level of fire, but
especially if you're going for like the richness of human

(43:08):
life and pleasure and foods and all that, it's got
to be right up there. Now, I do want to
say something real quick about the idea of the prometheus
of pickling. Now, in this case, I think pollen is
using pickling a little bit informally, but there is a
distinction to be made between pickling and fermentation. Basically, pickling
is preserving food with a salt brine, while fermentation involves bacteria.

(43:29):
So some pickled foods are also fermented, but they don't
have to be. Yeah, Like, for example, you can make
pickled foods that have no microbial action in them at all.
Like you just dump a bunch of like vinegar and
other flavors that you can make a pickle brine out
of vinegar and salt and sugar or something like that,
and it will be so vinegary that nothing will live
within it, so there's no fermentation going on at all. Yeah,

(43:51):
Like I do some of these box meals um uh,
like you know Martha meals, etcetera, and uh, And they'll
often have me do some like very quick fridge pickles
or sometimes they don't even go in the fridge. And
I have to say, sometimes I feel like I doubt myself.
I'm like, am I really making something that I can
call pickle? Or did I just throw some salt at
some cucumbers for like ten minutes? Oh, you can call

(44:13):
it a pickle. It's just not fermented. I mean, pickling
is is a broader umbrella. Um. And and there are
major differences in flavor. I'm sure you've noticed. Like you
can achieve the same preservative effect either by salting cabbage
allowing the lactic acid bacteria to thrive, which in turn
produces lactic acid which lowers the pH of the environment

(44:34):
and preserves the cabbage. Or you can just dump a
bunch of acid like vinegar directly onto the food and
just cut out the bacterial middleman. But you're losing a
lot when you do that, because the bacterial middleman actually
makes a huge difference in the aroma, taste, and texture
of the final product. That the bacterial middleman produces a

(44:55):
much greater diversity of flavorful compounds. Vinegar, pickled food, It's
can be great. I like them sometimes, but they are
fairly one note. Fermented foods, on the other hand, or
very often described as funky and complex because of these
wide ranges of of different flavorful compounds that come out
of the microbial metabolism. Just one example, and there are

(45:18):
tons of them. But for example, the cabbage fermentation process
in many kinds of kim chi produces not only lactic acid,
but compounds like diocetl which in other contexts. Diocetl is
known to produce a distinctly buttery taste. Sometimes, for example,
it's used as a flavoring in popcorn quote butter um.

(45:39):
But this is one of the reasons that fermented vegetables
like kim chi can sometimes take on these counterintuitively dairy
reminiscent flavors buttery, nous, cheesiness, despite having no dairy content. Uh.
And you might have encountered a similar flavor crossover from
alcoholic beverages like wine, like if you ever had a
a chardonnay that tay stood strangely like butter Uh. There

(46:02):
could be multiple reasons for that, but a major one
is diocetle. Diocetle from the metabolic processes of lactic acid
bacteria in the wine could be partly responsible for that
buttery flavor. And anyway, it's it's all of these metabolic
byproducts of the lactic acid bacteria that that create this
richness and complexity of flavor that comes along with lacto

(46:25):
fermented vegetables like kimchi. Okay, we need to take a
quick break, but when we come back, I'm going to
be chatting about vegetable fermentation with Dr. Esther Miller. Thank
thank We are back and now we're going to head
straight into my chat with Dr Esther Miller, who studies
fermentation and microbial ecology at a center called the Wolf

(46:46):
Lab at Tufts University. Here we go. Esther Miller, thanks
so much for joining us today. So to start off,
could you talk a bit about your background and how
you got into studying microbial ecology. Sure. Yeah, So I
did a sort of wandering path to get into a PhD.
So I started doing research at Oxford University on insight

(47:11):
and locust warming, and I moved to Sydney and looked
at locusts in Australia. And then I became a high
school teacher but with science, and then did work in
a biotech company that also looked at the insect. So
I did a sort of diverse range of things before
um coming to do a PhD at Tough University. And

(47:33):
it toughs you do rotations, and I did a bit
of a project in the Wolf Club and I loved it,
and I loved that it's uh ecology and so you're
looking at how communities interact and how different populations interact
is but it's very small. I can do it in
the lab. I don't have to go across Australia gathering

(47:54):
locust or anything like that. It's just on a blade
in the lab. It's very simple. But it's also in food,
and I really love food, and it was in cheese UM,
and I love cheese, and you know, I moved to
America from the UK and I didn't have access to
good cheese. So the lab was a great place for
um getting cheese. But I wanted to keep on with

(48:17):
the plant research and that sort of background. So I
asked Professor Wolf. I'm in the Wolf Lab. I asked
Professor Wolf if I could start looking at microbial ecology,
so the same things in the same questions that he
was asking, but in um, sauer kraut and fermented vegetable products,
and and he'll at me and it's um. It was great.

(48:38):
So from there I started developing ecological questions in this
fermented vegetable world. So one thing I can't leave off.
You mentioned that you had done research with locusts. I
was reading in another interview with you that I think
was in Cooke's Illustrated a few years ago, that you
you said that part of that research involved tickling the
legs of locusts. But I was curious what what that

(49:00):
was in service of studying. What were you trying to
find out by tickling locust legs? Yeah, so, um, the
desert locus, the cycle gagaria, which all of your listeners
will know if they've ever been to a pat shop
and looked at the lizard food. So the yellow and
black locusts that hop around and you feed them to
your lizards, that's the desert locusts. And they come in

(49:22):
that dusky like they're sort of dark when they're adults,
but they also come in bright green and it's the
exact same species. It's the same thing. It just has
a phase change where it goes from a solitary, beautiful
grasshopper that's all alone eating, not hiding anybody, and then
there can be a shift, um, and it's a serotonin
spike that shifts until it becomes gregarious and they start swarming.

(49:47):
So the research there it was Professor Steve Simpson was
looking at how what is that shift, what is triggering
that serotonin spike, and he found a few like agitate
if they're jostling, if you sort of have them in
a crowd, and they start knocking against each other. That's
when that chemical shift happens. So it was simulating locust

(50:10):
knocking against one another. So particularly yeah, yeah, you said
you use the paint brush to tickle their news. So
you tickle a locust leg for five seconds every minute
for eight hours, and then it will have a completely
different behavior. So the the parents takes a generation to
come through, and it will be brown and yellow later on.

(50:33):
But the behaviors, it goes from being uh, scared of
locusts and running away to wanting to aggregate and like
moving together. Did you have any interest in fermentation as
food before you got into the science of it, particularly,
I like, I like food, and so I think that's
what drew me to the lab, as well as the

(50:54):
strong emphasis on outreach. So it's very hard to get
people excite did about bacteria and people are just like, oh,
it's a disease, or wash your hands of of the
use of antibiotics. But this is something that I can
take a cheese or a jar of kimchi and talk
to somebody about it, and I think, um, it became

(51:16):
important to me to be able to talk to the
general public about research. I think from a teaching background,
finding a way that you can easily explain complex scientific
ideas by being like, Hey, this cheese is like this,
and why is it like that? And what is going
on with this microbe and that microbe? Oh that's great. Yeah,
this is like the sour krout can be a foot

(51:37):
in the door to a to a broader view of
the microbiological world. Yeah, and the cheese as well, Like
you can you can take cheese anywhere and people will
be excited because it stinks like it's immediately draws people
in because you're like, hey, smell this, and then they're like, Okay,
that's really growth. Um boy. I suppose you can do

(51:57):
that with kimchi as well. Um. And so they have
like smells and textures that are exciting, you know, totally. Um.
So maybe you could start off by giving me sort
of a character sketch of lactic acid bacteria as a group.
What are these organisms, like, what do we know about them?
And how do you think about them? So laticasi bacteria

(52:21):
are a whole group and as many different species in
this group. And then for the most part they are
called grass generally regarded as safe. So the FDA doesn't
really care about them. Um, there are in so many
food products. The more you study, the more you find,
So there's hundreds and you know, so they're not gonna
go around saying this one is safe and this one

(52:42):
and this one. They're just as a blanket they're safe.
Um there are in so many foods. Um And as
a rule, they take sugars and they ferment them into
lactic acid. That's pretty much the basics. Some of them
are a little more complex, and they'll turn things into
actic acid and um acetic acid and CEO two and

(53:04):
so those are the hatero fomentius. They do more than
one thing, so you sort of think they're making two
different assets, whereas the home of fermentus they're just doing
one thing. They're just making lactic acid. And that's the
two big groups when you're thinking about lactoc acid. And
if I ever call them LBS, it's laptic acid vecteria.
So we know that lactic acid bacteria are one of

(53:26):
the major players in uh in vegetable fermentations like kim
chi or sauer kraut. But could you give us a
broader picture about what's going on in the whole life
cycle of a of a microbial ecosystem inside a vegetable fermentation.
So if you take like a jar of freshly made
kim chi and it starts to ferment, who else is
in this microbial cast of characters and what do the

(53:50):
struggles for dominance look like inside that jar? So I'm
sure you and your lessons have maybe started experimenting during
COVID with fermentation, so you know that. Um, if anyone
started on souer cut, I think souer crt is under
utilize compared to sour dough. But if you've done any
fermenting of soun cut, which I think is shared, um,

(54:12):
do you know that you don't add a starter So
that's sour door. When you first do the starter culture,
you're just relying on the natural who is there to
inoculate the ingredients. So you take cabbage or if you're
making kimchi, other ingredients, or you can make other fermats
like adding in carrots or whatever, and the bacteria these
light to Casa bacteria just present on the surface. But

(54:35):
the one the first thing that I did in my
project was paid out the cabbages, and I found that
light to Cassa bacteria really low. If you're looking at
the bacteria present on a vegetable. There are lots and
lots of um proteo bacteria, many many things like pseudomonas
um spinglemona. So these are bacteria that like living on

(54:59):
plant le and for the most part, they're really beautiful
and colorful because they contain pigments that protect the bacteria
from UV light. So if you think of a cabbage
out in a field, it's actually exposed it really really
high levels of UV light, and it doesn't have a
lot of water accessible on the leaf surface. So leaves

(55:20):
are normally covered in a waxy film, and so there's
not a lot of nutrients, there's not a lot of water.
It's really hard to survive. And the bacteria that are
there have a lot of pigments and ways that they
can adhere to the surface of the plant and help
them survive. And it's not really the lactic as of
bacteria's way of living. They're not really high but like

(55:41):
very abundant on the leaf. But when you chop that
leaf up to make your sua crowd, you're releasing those
punch sugars. You're making them like very readily available. And
then when you add the salt, you further draw out
those sugars, and you completely change the playing field. So
you've gone from a high oxygen, highlight, low nutrient condition

(56:04):
to all the nutrients in the leaves are out and
slashing about. You take away the oxygen when you push
it down into a messenger, and you add salt, and
this is really really strong abiotic selective pressure that will
change who can live. And that's when the lactic asa
bacteria really come into their own and they can start

(56:25):
increasing in abundance. Now I mentioned earlier the two big
groups of lactic asa bacteria, the petro fermentors and the
homo fermentors. So at the very start of fermentation, we
get a massive increase in the hetero fermentors. So that's
things like lucona stocks and ver clia um and they

(56:48):
really take off and they're super abundant, and they're making
lactic acid and acetic acid. Now these two acids start
lowering the pH and that makes it easier for the
homo fomentous to start growing. So you sort of see
a true phase. I wish I had a white water.
You can draw it out where you have one population
that increases and then a second population, so a second

(57:11):
wave UM, and that lower is the pH even more.
And as the pH falls um, those proteo bacteria that
we're talking about they can't survive, and they won't they
won't be present at the end of fermentation. So if
I'm corrected, this first group the hetero from enters that
produced the multiple byproducts. You said lactic acid and acetic acid.

(57:34):
So acetic acid would be basically the the acid and vinegar, right,
And lactic acid is also what's coming out of the
homo from enters, the lactic acid bacteria that come in
the second wave um. And is that am I correct
in thinking? That's also the same thing that builds up
in our muscles when we exercise and start to feel
the aching and and all that sort of the presence

(57:55):
of the lactic acid bacteria causes the pain of exercise. Well,
it's the same lactic acid. Oh, I'm sorry, did I
say bacteria. Sorry, I didn't mean to say that. The
lactic acid. Yes, yeah, yeah, exactly, yes, And actually lactic
acid is a less harsh acid. So if it was

(58:17):
just fermented by hetero fomentors and it just we ate
a sourer krout that was just made with a seedic acid,
it wouldn't be that nice. It would be very very
it would be like a very harsh like a pickle,
Like you wouldn't eat all of the pickle juice because
it's very vinegary um. But when you have sour krout,
it should have a softer, buttery flavor. So you have

(58:39):
to sort of trust me on this one and go
home and eat some and compare it to just straight pickles,
which are quite acidic, because that lactic acid has a
softer um like, it's not as shark. Yeah, that's definitely
something you notice is a difference between quick pickled foods
that you use vinegar to pickle versus fermented foods where
it comes from the back to it's a much more soft, round,

(59:02):
complex kind of flavor. So so normally when you ferment
vegetables and uh, and you're trying to you know, you
salt them, you make a brine, and you encourage the
lactic acid bacteria. You said, you see these two broad
spikes with the hetero fomenters and then the homo fomenters um.
But even within that, you're still going to see a
lot of different species involved, right, that there can be

(59:25):
widely different profiles of what exact lactic acid bacteria are
taking over. Is that correct? Yes, there's a lot so
UM looking at who's there, there's just some big players,
so they'll be like lacto, basilis, bravis in basically everything
at a really high percentage, and then there'll be a
lot of UM low numbers of many other ones. So

(59:47):
we've just recently done a survey of North American fermented
vegetable products UM, which I was really excited about because
there's a lot of research on UM Asian products. So
there's a whole research institute of kimchi in Korea, and
there's UM a lot of research in Europe. But this
is the first United States Sauer Kraft survey and we

(01:00:11):
found on average teen point eight species of lactic gas
of bacteria her jar. But most of them are some
of the really common laticas of bacteria. They take they
take up the bulk. So would you find any noticeable
differences in in like aromas or flavors produced depending on

(01:00:32):
what the microbial ecosystem in the fermented jar vegetables looks like?
I haven't. I haven't done any specific research on that,
but I haven't myself noticed anything. I think there can
be a big difference between kimchi and sauerkraut, which is
hard to measure in terms of the bacteria that are
present because there's so many other flavors going on. So

(01:00:56):
some kim cheese are fermented at a lower temperature, and
when you of fermenting in a really cool temperature, like
between ten to fourteen degrees celsius, you're promoting those hetero fermenters,
so you get a different flavor. So there can be
a lot of asalia in kimchi, which is less prevalent
in souer crawl like, They'll still be there but in

(01:01:18):
lower numbers. But it's very hard to compare the flavors
and attribute that to the bacteria when you've also got garlic, ginger,
red pepper and everything else. That's one thing I found
hard in doing the survey is that every producer might
have different vector, but they all have like their slight
tweaking of recipes, so some had like caraway seeds or

(01:01:43):
they throw in an apple just like So you mentioned
that that the lactic acid bacteria tend to be found
in very low numbers. If you just takes a raw
leaf of cabbage from the farm before fermentation. So we're
do we have any idea about where these microbes generally

(01:02:04):
come from. Is it just something that's probably there on
a leaf of cabbage even though it's in very small numbers,
and then the fermentation environment helps those numbers bulk up
over time, or there are other possible vectors. Yeah, So
I went out to farms or common gardens um in
the summer of sen and tried to find environmental sources

(01:02:28):
of Lactica Sa bacteria. So I took soil and leave
examples and not cabbage leaf um, wead leaves and things
that were just growing next to crop plants um, and
I found that they had pretty low levels of lactic
as bacteria. So I didn't find like a big environmental
reservoir of these bacteria, which I think it's pretty incredible

(01:02:48):
that we know so much about them in the human
micro like the human got microbiome and in probiotics and
probiotics and fermented foods, but very little is known about
their pology, and I couldn't find too much. I think
I definitely talked about it in the in a previous
podcast about maybe they're being affected in by insects. If

(01:03:11):
you are USU papers where honey bees have let to
gas a bacteria and that guy um and they're very
specific two bees though, I think because bees taken nectar
and then the sugars in the nectar can get broken
down by lack to gas of bacteria. But I haven't
yet found any evidence that the insects and the insect
droppings go on to be the source of lack to

(01:03:33):
Gasa bacteria and fermented vegetables. So perhaps a very small
amount of lack to Gasa bacteria in soil can then
try and like dispersed onto cabbages repeatedly, and then maybe
it's just low levels everywhere it's it's still a puzzle.
Is it possible also that some amount of it just
comes from the kitchen environments or other environments where this

(01:03:57):
where fermentations are prepared, that it's on jar as, it's
on spoons and all that kind of stuff that's been
sort of talked about a lot, and I'll have to
look up the name for you, but there was a
recent paper where they looked at a saddle crowd facility,
so they I think it was at one facility in
Rhode Island. They went to this one place and they
sampled fridges, doors, walls, everything, and they didn't find like

(01:04:20):
to cast a bacteria in the environment. They only found
levels on the cabbage. But if you're thinking about making
sadle crowd in a facility, you're gonna have tons of cabbage.
So even if you put together like ten cabbages in
one giant fact, there's a lot of cabbage and you
only need a tiny bit of the bacteria to make

(01:04:40):
it to get it to take off. Whereas if you
think if you were making it at home and use
half a cabbage, then just by probability, by chance, you
might make one that didn't have enough or didn't have any.
But if you multiply the amount of ingredients, I think
you always have some amount of l to casper to
you now, was I reading that previously you did some

(01:05:03):
research with trying to grow sterile cabbage in order to
to inoculate it with bacteria and see how the bacteria
did on it. Yeah, I'm very excited about it. It It
came out in the Journal of Visualized Experiments, and then
I couldn't film because of COVID. But they will be
coming in on Wednesday. Um, but I managed to grow
cabbages and I can send you pictures. Um, I managed

(01:05:26):
to grow cabbages in glass tubes and they are sterile
as far as I can tell. Like you know, maybe
there's some media that one bacteria could grow on, but
as far as we can tell, they're completely sterile, and
they're happy, and they're growing in calcined clay. You can
articulate that. So if you put in the articlave, high heat,

(01:05:47):
high pressure, will be sterile at some nutrient broth and
they're really happy. And now did that research involve you
trying to see what kind of environment those previously sterile
cabbages would make for different microbes or was that just
to study the cabbage itself and how it could how
well it did without a microbiome. No. I wanted to

(01:06:08):
do actual competition experiments with large caste bacteria and the
philosphere microbiome. So the philosphit is the community of bacteria
living on a leaf. So I wanted to say, well,
maybe like to cast a bacteria in low abundance because
they need a particular microbe to grow with, or there's competition.

(01:06:28):
So I made all of this sterile cabbage. It took
me years and then I inoculated it with lead casa
bacteria and they don't grow. Like if you just spray
a cabbage with lack to caste bacteria and it's happy.
You don't put any other thing in there to compete
with it, it won't grow. The cabbage are the lactic

(01:06:48):
acid bacteria. The cabbage is fine. The cabbage I wasn't interested.
I haven't done any measuring of cabbages or their growth. Um,
they do fine with or without a microbiome. I sprayed
some yeast on cabbages once and they didn't enjoy that.
The cabbagies went brown and just with it. But bacteria

(01:07:11):
fine on cabbage. They don't influence the cabbage. But yeah,
I did twenty bacteria that you just naturally find on
a cabbage and things like the uh pseudomonist that I mentioned,
So things like that, I sprayed them on the cabbage
and they will increase. You will see like they're happy
growing on a cabbage. The lattic as a bacteria tank.

(01:07:32):
So it's very hard to do an experiment with something
that won't grow, like I mix it with other things.
They grow Bacteria gus wow, Uh, so we know that
obviously these lactic acid bacteria are the main player and
vegetable fermentations, but there are fungal microbes like yeast, so
we've mentioned a little bit that are major players and

(01:07:54):
other kinds of fermentation of course, in like bread or
in wine or beer. Did you mention over our email
that um that in looking at store bought preparations of kimchi,
you've found yeast in some of them. That seems kind
of surprising. Yeah, So I tried really hard to find
some literature on this, and you only see a few

(01:08:15):
papers from a long time ago stating that yeaster um
sometimes found as spoiler organisms. But when I did this
North American sour krout survey or fermented vegetable product survey,
so it is sour kart's and kim cheese, I found
over half of them had yeast, like a lot a
lot of yeast, Like some of them had more counts

(01:08:37):
of yeast than bacteria, which was really surprised by. So
the back the use that I found is safe. There
are things like kazakhstania, which you do find in sour dough,
so they're not they're not toxic. But everything that you
read says there undesirable and fermented vegetable products because they
give musty, yeasty, sort of dankish flavors, I guess, and

(01:09:00):
they can form a film, which I think it's pretty
offputting if you're trying to create a new product that's
covered in a yeast film. Yeah, you want your cut
smell like skunky beer. No, definitely not. It's already yes,
a tough sull. I when I had this, I had
fifty one jars and I was delighted and I was like, hey,

(01:09:21):
who wants some? And I would open I opened and
sampled them all in the conference room. It's smaller rooms
and they's a tough and people were not happy. They
were like, wow, the whole rooms stank for a week.
I think it's just in an enclosed space. Opening fifty
one jars of sauer kraut and kimshi was a little much,
but yeah, and I tried to eat them all, but

(01:09:41):
I I really couldn't. That's that's a lot. But you
couldn't eat fifty jars of kimchi by yourself, or sauerkraut
and kimchi. No, I tried so hard. I can do it.
And part That's why I wrote the grant. I was like,
now I can get to eat all of it. If
I write a grant that says I need to buy them, well,

(01:10:02):
that makes me think you you correctly guessed that. One
of the things that got me interested in talking about
kimchi on our podcast is that I had been trying
to make it at home for the first time recently.
Uh and one thing that has so I've loved kim
chi for years, and I've always put off trying to
make it because it seemed like a scary, daunting, potentially

(01:10:25):
dangerous procedure if you're fermenting things and you don't know
what you're doing. But honestly, i've I've found it easier
than I expected it to be. So I guess one
thing a lot of people are probably wondering is how
safe is it to experiment with making sauerkraud or kim
chi or some other lacto fermented vegetable. Is this something
that's probably gonna poison you if you screw it up,

(01:10:46):
or is it pretty forgiving. That's a great, great question
because I think people are really scared and when people
come over there, because I have a lot of fim
it's on my friends these days, but they're actually pretty safe.
Anything that's anaerobic, um, you're really really making it very
hard for things like et coli and my steria to grow,

(01:11:07):
So they're pretty safe if you do get the anaerobic
conditions correctly. So sometimes if you're fermenting in a massenger
and you have like a pocket of air on the top,
you'll notice the very top layer of your ferment might
be a little off, and then you can just take
that off and then push it down so it's submerged.
But probably not an official thing to say, so basically,

(01:11:30):
as long as you've got the salt there and the
stuff's underwater, it's it's going to be safe. Yeah. I
think that's one thing that I found remarkable with everything
that I've done, with everything that I've read. I think
that's why I just love this project so much, because
it seems so haphazard, like you're just taking random ingredients
and salt, and yet it works so consistently um worldwide.

(01:11:53):
You know, That's what blows my mind. The things that
we found in this North American survey are the exact
same things that they find in Europe, to the exact
same things that they find in everything in Asia. So
you're like, it's so robust. Broadly, what do you find
amazing about fermentation? Well, that bacteria that we don't know

(01:12:15):
how they where they live in. We can't find them
in the environment get into everything that we eat, and
a consistent Like, it's amazing we can't track them. But
all over the world there's it's the same species and
you can't follow it from a field to a cabbage.
You know, that's amazing. That is amazing. Uh, I don't know.

(01:12:38):
It's one of the things we actually love to talk
about on this show is kind of the hidden realities,
the things that are so important to human culture but
that you know, you wouldn't be able to see them
looking at I mean, I guess you don't see any
microbes with your eyes normally unless they're starting a really
big colony. But but even with scientific instruments, like you
don't know where all these microbes are coming from. Yeah,

(01:13:00):
it's amazing. Like I was trying to write a review
on dispersal, like how do how does the bacteria get
from here to that? And you can read about the
moving miles and thousands of miles on wind. It just
gets in the wind and just dispersed. But you you've
got no way of really knowing unless you sort of

(01:13:21):
make genetically modified bacteria and release them, which I'm not
going to do. But you know, like, how could you
know if there's bacterias that, because they're so small, you'd
never tracked them. I think it's amazing. So is there
anything else you've been working on recently that you wanted
to talk about? Well, I was gonna say, and I
forgot to mention that I am doing a community assembly experiment.

(01:13:43):
So I've got three yeast and three bacteria that were isolated.
Most of them were isolated from that Sauerkroud survey. So
I took the bacteria that I found in that survey,
and I'm competing the yeast and the bacteria together in
little jaws of sterile vegetable extract two, and I've put
them under different conditions, like different temperatures, different salt concentrations,

(01:14:07):
um and using different cabbage extracts a red cabbage, grain cabbage,
and Napa cabbage to see if any of those influence
the presence of yeast. And actually, I think it looks
like the temperature that I fermented at could be influencing
the abundance of yeast. So at higher temperatures, perhaps you
get more yeast. So maybe the North American fermenters are

(01:14:28):
using different conditions and that's why the ferments have more yeast.
But I'm still working in it. Interesting. So, if if
you're making kimchi at home or making sarokrawd at home,
and you want to keep the yeast out, a lower
temperature fermentation might be a better way to do that. Yeah,
So if the temperature in your room is getting sort
of like above twenty four degrees, you might want to

(01:14:49):
put it in the basement or somewhere a little cooler.
And I did notice that if you don't put salt
in it, it can go horribly wrong. The pH just
doesn't fall as much because tried that, and I was
even adding LA to Casa bacteria and the pH wasn't
dropping as well as it should with two. But there

(01:15:09):
wasn't a big difference between two and four. So I
think sticking at two percent salt is good. Am I
understanding the causality right there that the salt essentially makes
um makes an environment that's less hospitable for other types
of bacteria and microbes to thrive. But the lactic acid
bacteria or tolerant of salt is that it is it.
That's what I always assumed um and think is right

(01:15:32):
when you have just regular cabbage. But I was using
sterile filted vegetable extractures, you know, so just completely sterile
media and adding LA to CASA bacteria in the east,
So they allowed to Casabactero didn't have that much competition,
you know, they're there with the East, and yet they
still didn't do that well when there's no salt. Mm hmm.

(01:15:54):
So maybe the salt is even helping it in some way.
I think there's got to be something going on with
the salt as well. M m, well that's very interesting. Alright, Well,
I think we have to call it there. But thank
you so much for joining us today. This has been
so great and we really appreciate you sharing your time
and your expertise. It's been a lot of fun. Yeah,
thank you very much for having me. Well, I guess

(01:16:18):
that wraps up this episode, but once again, huge appreciation
to Dr Esther Miller for taking the time to speak
with us. And I will say, though this episode is over,
there is that whole hidden world flowing into the fermentation jar.
So it's possible that we may have to come back
and explore other corners of that world again in the future.
In the meantime, if you would like to listen to

(01:16:38):
other episodes of Stuff to Blow Your Mind, you know
where to find us. That is, wherever you happen to
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(01:16:58):
for the future, or just to say hi, you can
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(01:17:18):
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