From the Vault: Kimchi

What exactly is kimchi and what is the chemistry of its deliciousness? In this classic episode of Stuff to Blow Your Mind, Robert and Joe explore this spicy, fermented staple of Korean cuisine. (originally published 6/25/2020)

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Episode Transcript

Speaker 1 (00:05):
Hey, welcome to Stuff to Blow Your Mind. My name
is Robert Lamb and I'm Joe McCormick. In today's episode
is from the Vault. It's Saturday. Of course, it's Vault
time as always, and so today we're reaching back into
June of This one originally published on June of last year,
and this was our episode about fermented vegetables, about kimche

(00:26):
and sour Crowd and that whole funky awesome world. All right, well,
let's the vault is open, the kim Chi rise it,
let's enjoy. Welcome to Stuff to Blow Your Mind production
of My Heart Radio. Hey you, welcome to Stuff to

(00:49):
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 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

(01:10):
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 here Kim she a Song of Salt and Cabbage,
I guess it's a missed opportunity for us to have
done some sort of um wester Roast themed cold open
skit about about Kim She. Well, I guess the real

(01:34):
prince who was promised in the story is the lacto
basilla s bacteria and and he must come in order
to rescue the fermentation 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 wester Ros books,
because it seems like they were always lengthy descriptions of

(01:57):
what kind of foods UH actors were eating. Yeah, but
a lot of it is I think like a classic
Anglo cuisine inspired, 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,

(02:23):
all right, But then I do we do have to
to point out that I guess there was beer, there
was cheese, 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

(02:44):
some of the more um elaborate examples. For instance, uh,
there's the kivak, which is the traditional Inuit food from Greenland,
in which little ox, these these little birds are caught
and then fermented in a seal skin and it's buried
beneath rocks. There's a great feature on this in the
documentary series Human Planet that came out several years back

(03:07):
and was at the time narrated by John Hurt. I
gotta admit, as much as I love fermented foods, I
have never tried 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 chi have seen more of
an international renaissance and in recent years. Yeah, I feel

(03:30):
like when I was a kid, I wasn't as exposed
to as many fermented foods aside from these obviously fermented foods,
you know, like they I remember being 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 bad? Uh? I'm just I'm just so
sorry for your deprived childhood. I mean, I I can

(03:51):
remember loving sour kroud as long as I had. One
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's some sort

(04:13):
of German um, oh, some sort of purple cabbage 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 sour kroud and I
love Kim she I love exploring the various fermented veggie
or mushroom items you'll find uh in various cuisines. And

(04:35):
and my son, who is eight now, he's been pretty
pretty into all things fermented pretty much his whole life,
as long as they're not actually spicy. That's where he
has a little more of a 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

(04:55):
of unfamiliar flavors and aromas that takes him getting used to,
So I would imagine that having a taste for fermented
foods is somewhat learned. Though then again, I 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,

(05:18):
since this could be a possible vector to get useful
gut bacteria and other beneficial microbes that I think there's
good 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.

(05:38):
So I wonder it's it's possible. I can imagine that
there's some kind of instinctual predisposition that animals that like
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 kimchi or yogurt with smell

(06:00):
of food that's rotting due to an unambiguously unfriendly micro
But in these cases, our visceral reaction to 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 kimchi or sauerkraut, But I think that negative
reaction is qualitatively different than the like, you know, hot

(06:22):
garbage kind of reaction people have to the smell of
like real dangerous spoilage in foods. Yeah, 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 know 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

(06:43):
I've I've I've read some different things about about kids
in flavor just through I think virtue 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 poisons, that that they going
to be overly sensitive to certain strong smells or flavors. Um.

(07:04):
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 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

(07:26):
be developed in the womb or during very early life.
So we're talking prenatally and postnatally, involving both the amniotic
fluid and breast 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

(07:47):
from the from the parents environment can come through to
the child like that. Um. 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
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

(08:08):
them the smell is coming from a cheese, but find
it disgusting if you blindfold them and tell them it's
coming from a sock. Uh. For people on a Western
diet who are unfamiliar with kim chi 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

(08:31):
reason to associate them with, say 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 western circles, and I

(08:56):
think part of that is, like, if my my take anyway,
is that 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.
IM more accustomed to a really sweet smell with a

(09:18):
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 experience new flavors
and aromas as pleasurable when you're not used to them.

(09:40):
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
to like regular consumptions. So I would love to hear

(10:02):
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 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 once
unfamiliar to us can become very very central to our

(10:23):
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
kim chi is one of my favorite foods. I mean,
if you, if 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.
I would try to reach for something like, well, something

(10:44):
that could be served with bon schon, you know, all
those little dishes like Korean side dishes of various different
vegetable preparations and kim chi 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 say mature, just as we go on in life.

(11:05):
So in terms of just fermentation in general, we'll get
back more specifically to kimchi 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 sauerkraut king. Yeah.
Cats points out that if you venture into any restaurant

(11:28):
on the planet, if you dig into any cuisine, you're
going to find products of fermentation. And again this includes
more obvious examples such as you know, the sour krout
and the kimchi, but it also means bread. She's saladdressing alcohol, etcetera.
In fact, you know, he contends that it's hard to
get through the day without engaging with a product of fermentation.

(11:49):
All right, so we're naming fairly disparate seeming food items.
I mean, what do bread and cheese and sauerkraut and
kimchi really have in common? What? What? What is it?
It 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

(12:12):
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. Is something
a way that you could take your food with you
and it would survive and be edible when you get

(12:32):
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 vegetables and products
through the winter. The traditional preparation cycle for kimchi involves
packing it into pots in the autumn that can be

(12:53):
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 a taste preference,

(13:15):
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 kimchi. It's not always
like this, but certain kinds of kimchi not only have
these great complex flavors and pleasing crunch, it sometimes has

(13:38):
something you don't find in other solid foods, which is
a palpable taste of carbonation in the mouth. Sometimes kim
chi 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 this bubbling
property of fermentation is all so what creates. Of course,

(14:01):
you know the crumb structure, the holes in a loaf
of bread. But these bubbles are gas given off by
the yeast in bread as they metabolize the sugar in
the dough. The effervescent property in uh in kimchi, of course,
is the is the CEO two produced by the bacteria
as they break down the sugars in the cabbage. But
this effervescent property of giving off bubbles or gas was

(14:24):
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 alcohol
to make wine, it would give off bubbles as if

(14:46):
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 at different

(15:06):
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 organism. Specifically,
what they're doing is they're participating in the chemical breakdown

(15:27):
of molecules in the food. So they're breaking down long
starch chains into different pieces of those chains, getting a
little different sugars 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

(15:49):
of oxygen and uh ands. 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
micro 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 sourkroud and kim chi is lactic acid bacteria.

(16:14):
And we'll 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'll kind of whilt down, release water, create a brine
that's salty in nature, and the salt creates an environment
where certain kinds of bacteria that are tolerant of salt

(16:36):
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.

(16:59):
It lowers the h 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

(17:20):
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 of
fallen fruit to the interuric fermentation inside a creature's digestive system. Yeah,

(17:41):
and this is actually an evolutionary adaptation. Interect 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,

(18:02):
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,

(18:25):
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 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 that

(18:47):
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 herbivores have a kim chi
jar inside their digestive system. But you know, if you've
ever tried to make kimche at home, which I am
doing right now, one thing you know is that as
the fermentation happens, you either need to have a ventable

(19:09):
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
terrek fermentation, because these room at herbivores end up having

(19:30):
to burp out an awful lot of byproduct gas, generally methane, right,
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 to fiddle with that,

(19:51):
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 mic orobiota
or two 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, of the fermentation process,

(20:14):
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. Alright,
we're back. So Robert, you you've teased us about the
history of fermentation, saying that intentional use of fermentation of

(20:37):
foods by humans is something that goes back to the
Stone Age, the Neolithic era, right, you know, at least
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 fermented mixture of rice, honey

(20:58):
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. H in two thousand four
written by A McGovern at all and then I was
also looking at a two thousands sixteen study from Adam
Bothius in the Journal of Archaeological Science, and that puts
a date on Scandinavian fermentation evidence to nine thousand, two

(21:23):
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
fish in preserving it for later. The author discovered evidence
of this gutter along with vast quantities of well preserved
fish bones to support this argument. And fermented fish products

(21:46):
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 nonplaw. These are made by salting fish and then
using the extracted liquid that comes out as the strong,
deeply complex salty flavoring agent. Another example would be an

(22:09):
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 or you know, controlled
rot but that's what they are. Yeah. And if you

(22:30):
want more on garam and 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. Yeah. Now, as
for the fermentation of vegetables, that's key to what we're
talking about here with Kimche And it's believed that this

(22:51):
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. This
is fascinating and it reminds me of the evidence that

(23:12):
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, taking,

(23:33):
taking those grains and then baking 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

(23:54):
that looks very much like breadcrumbs there. So these would
be bread, predating the agricultural revolution by thousands of years now.
As for kimchi itself, so yeah, 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 if you'd agree

(24:16):
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 kim chi 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 napa cabbage Korean radish, made with a

(24:38):
varying selection of traditional seasonings. Yeah, A very common preparation
for kimchi would be you take napa cabbage, you salt
it to 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 chugaru, which is a red

(24:58):
chili flake um. And then ginger garlic, often 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 that's a pretty standard preparation. Now.
I was reading about kimchi in the history of Korean

(25:20):
go Chu Go go Chang and Kimchi in the Journal
of Ethnic Foods from And 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 kimchi cabbage as
it is known today, it decomposes at normal temperatures due
to the action of micro organisms. The authors here point

(25:42):
out that specifically with with modern kim chi, you add
red pepper powder containing capsation to the cabbage and this
suppresses the growth of of putrefying bacteria and promotes lactic
acid bacteria. The micro organisms here the authors where I
grow and change into a form that emans can consume. Now,
the basic process here is responsible for other key Korean

(26:04):
fer minted food products as well UH, such as a
go go chang, uh, Chian cook chang, 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 beatification and leads to
the production of lactic acid. And there are different varieties
of go go chu. I think they're like four main

(26:26):
categories now in terms of when the gochu peppers become
involved in the process, apparently there I was, 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

(26:50):
with modern political concerns, like when exactly different types of
kim chi came to exist. Yeah. For instance, that Quan
paper that I that I had 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.

(27:10):
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 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 jag at All

(27:32):
in Journal of Ethnic Foods, citing the Chronicles of the
Three Kingdoms of Korea as a as an historical source,
dating kimchi back 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 bolical, we see it at least some evidence of
it fifteen hundred years ago. Yeah, based on the historical

(27:53):
sources I was reading, it seems like the most likely
thing is that kimchi is definitely an ancient Korean food,
but the introduction of peppers specifically is more recent. Right, Yeah,
that seems to be the case that you don't you
don't need, or you at least didn't need peppers for
kim chi, uh, you know, throughout most of its history,

(28:14):
but then you end up seeing the introduction of these peppers.
I was reading The Colombian Exchange, 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

(28:36):
what is today Bolivia and southern Brazil. From there they
traveled into meso America and the Caribbean before the arrival
of Europeans, who then took it elsewhere. So along these lengths,
it'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 J. Bock Park wrote

(29:00):
about it in Red Pepper and kim 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 we're altered into
several types of kimchi to suit the taste of Koreans
during the Sheila and Korea dynasties. That's C through and

(29:24):
cen through two respectively. Uh. Anyway, the author continues, quote,
Since red peppers were imported to Korea in the early
part of the seventeenth century, whole cabbage 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

(29:46):
flake is a very important ingredient in some of the
most popular forms of kimchi, I believe there are still
forms of kim she 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 brian or the marinade. But

(30:06):
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 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,

(30:26):
it seems like it is difficult to overstate just how
important kim she is in Korean culinary culture. Uh. There's
a two thousand sixteen article on NPRS The Salt titled
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

(30:48):
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 win Napa,
cabbage and a twelve other ingredients chili, carrots, radishes, and
anchovies among them, are at their best prices. Yeah, there's

(31:08):
been a pretty concerted 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
to to help engender love for your culture around the world. Yeah, yeah,
share it with the world. And that's where you see

(31:29):
initiatives like the Kimchi bus. I don't know if you
ran across articles about this, No, I didn't um. This
was which was supported 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 and kimchi. Um,
you know, very very much spreading the word of kimchi.

(31:50):
It's like an Iowa campaign bus for kimchi. The kimchi
is going to get out and give a speech. Now.
That article from The Salt it also points out some
other uh cool facts about about the culture of kimchi
and in related foods. At points out that kim jang,
the tradition of making kimchi, has long been a unifying
tradition amid Korean villages and a sustaining one through periods

(32:13):
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
to make their their pots of kim chi in the
autumn that can be buried for the winter or the

(32:34):
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 amid a large group of people.
So it's not just you know, my household is making
kimchee today. It's no we we as a community, you know,
or even we as you know, as people are making

(32:54):
kim che 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 the kids
because like, the kids can maybe work on massaging the

(33:17):
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 fun. You were mentioning the specific jars you
have for it, and I think we actually have one
of those jars, because I think we have some sort
of Sauer kraut kit that just hasn't been used yet,

(33:38):
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, in case you forget about the kimchi you've
got going in the jar, It's not going to blow
the lid off or anything. It's got a little vent

(34:00):
where if the pressure really builds up inside the CEO
two can escape out the vent. Now, speaking 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 as culturally important as kimchi. Uh. This is
one of the reasons that kimchi has gone into space.

(34:21):
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 into space that we're space ready, uh for
just such an individual. Now, as for why why take

(34:43):
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 to send something as important and
is kim chi up with them on an individual level.
We've talked about this in the past concerning space food.

(35:06):
You know that this is um going into spaces 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 some sort of food that that not
only sustains them 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

(35:27):
is sent up with astronauts. But then on top of that,
micro gravity often is often described as uh is living
in microscrap. Gravity rather is often described as being in
this kind of state of perpetual nasal blockage, right, because
everything is 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

(35:49):
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 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

(36:12):
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 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

(36:36):
is part of Korean cuisine, but that it is such
a regular part of traditional Korean culinary life, that um,
that kim chi. You know, it's 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,

(36:56):
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 kimchi 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 kimchi that are not
the case with other foods. Because have you ever seen

(37:19):
what happens when there is a sealed jar of kim
chi without a burping lid, and the fermentation gets a
little too aggressive, gets a little frisky. Uh, you should
look up video of this, Robert. And so the microbes
inside the fermentation will produce c O two as they
do their business, and they can produce so much c

(37:41):
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, it's like mintos in 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 pudding. Uh,

(38:01):
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 if they let you do that anymore, but
this at least has been a problem for some people.
I'd 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

(38:25):
in spicy, rotting cabbage water, which is delicious but not
really something you want to fully saturate your underwear. Um
that that 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 you, asked
younaut about this, asking you know, what was it like.

(38:47):
And the one thing they point out is that for
the kimchie to go into space, it had to be
radiated to kill all of the micro organisms in it,
which he says 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 kimchi that it did

(39:08):
the job. You know. It um It packed the you know,
the spicy fermented punch, and it reminded them of home.
So Nitian accomplished. Well, this is an important point because Okay,
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.

(39:28):
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 kimchi is at
its core a living product, and you can have kimchi
that's been sterilized. I mean sometimes people sometimes I cook

(39:50):
it before I eat it, especially when it gets older.
You know, you can saute in the pan and add
as a as an ingredient to things. And then of course,
like kimchi fried rice, fantastic delic just but at that
point it is sterile before cooking it or 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,

(40:10):
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 is still evolving as an ecosystem. Absolutely.
Now speaking of that that ecosystem, let's bring everything back

(40:31):
down from space. Uh, not only to the Earth, but
under the earth. Because we've already referenced a few types
of fermentation. Uh. That entails bearing a vessel or using
some sort of a gutter, you know, made in earth
or stone. It's worth noting that the traditional means of
creating kim she also entails bearing, uh, the the container

(40:54):
bearing what Michael Pollen in his two thousand book Cooked
described as a child old sized earthenware croc. So I
wanted to read just an excerpt from that that excellent book, which,
by the way, mentions kimchi a lot. So if you
if you're looking for, you know, a really good book
about about food science and history, you know, a horse

(41:15):
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, 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,

(41:39):
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 conditions that the lacto
bacilly prefer. The earthenware croc is a good reminder that
every ferment is food and drink stolen or borrowed from

(42:02):
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. That sounds like a
great story to where is I would be shocked if

(42:22):
there was not some mythical tradition that had a story
of a god giving the gift of pickling or fermentation
to humans. Yeah, it's seen. I hadn't haven't had a
chance to look into it, but I would assume that
some god or another would have that at least on
their their resume. You know. For Paullen's part, he goes
on in this book to think, well, okay, pickling, fermentation,

(42:44):
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 a only put it on
par with fire in our history, saying like, like pickling,

(43:05):
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 you Remember we talked previously about the importance
of bread in the development of human civilization because of
the kinds of nutrition that it could provide relative to

(43:27):
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 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

(43:49):
idea of the prometheus of pickling. Now, in this case,
I think pollen is 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. So some pickled foods are also fermented,
but they don't have to be. Yeah, Like, for example,

(44:10):
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, Like I do some of
these box meals, um like you know, Martha Meles, etcetera.

(44:32):
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 it pickle? Or did
I just throw some salt at some cucumbers for like
ten minutes? Oh, you can call it a pickle. It's
just not fermented. I mean, pickling is is a broader umbrella.

(44:53):
Um and and there are major differences in flavor. I'm
sure you've noticed. Like you can achieve the same preservative
fact either by salting cabbage allowing the lactic acid bacteria
to thrive, which in turn produces lactic acid, which lowers
the pH of the environment and preserves the cabbage. Or
you can just dump a bunch of acid like vinegar

(45:14):
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 much greater diversity of flavorful compounds. Vinegar pickled

(45:35):
foods 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 tons of them. But for for example, the cabbage

(45:56):
fermentation process in many kinds of kimchi produce is not
only lactic acid, but compounds like diocetal, which in other
contexts diocetel is known to produce a distinctly buttery taste. Sometimes,
for example, it's used as a flavoring in popcorn quote
butter um. But this is one of the reasons that

(46:16):
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 tasted strangely like butter Uh.

(46:38):
There could be multiple reasons for that, but a major
one is diocetle. Diocetal 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

(47:00):
lacto 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

(47:21):
Wolf 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 inside

(47:46):
and locust warming, and I moved to Sydney and looked
at locust in Australia. And then I became a high
school teacher but miss science, and then did walk in
a biotech company that also looked at the insects. So
I did a sort of diverse range of things before
um coming to a PhD at Task University, and it tough.

(48:09):
You do rotations, and I did a bit of a
project in the Wolf lab and I loved it. And
I love 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 locust or

(48:30):
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 getting cheese.

(48:50):
But I wanted to keep on with the plant research
and that sort of background, so I asked Professor Wolf.
So I'm in the Wolf Club. 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 u sauer kraut and fermented vegetable products and

(49:11):
he'll at me and it's um. It was great. So
from there I started developing ecological questions in this fermented
vegetable wild 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 Cook's Illustrated a few years ago, that you said
that part of that research involved tickling the legs of locusts.

(49:33):
But I was curious what what that was in service
of studying What were you trying to find out by
tickling locust legs? Yeah? So, um, the desert locus, the
scog area, 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

(49:54):
the desert locusts. And they come in that dusky like
they're sort of dar 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

(50:14):
a shift um and it's a serotonin spite that shifts
until it becomes gregarious and they start swarming. 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 if you like agitate them, if they're jostling,

(50:36):
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 knocking against one another.
So tickling them, yeah, yeah, you said, you use the
paint brush to tickle their So you tickle a locust
lag for five seconds every minute for eight hours, and

(50:59):
then it will have a completely different behavior. So the
the the parents takes a generation to come through and
it will be brown and yellow later on. But the
behaviors it goes from being uh, scared of locus and
running away to wanting to aggregate, like moving together. Did
you have any interest in fermentation as food before you

(51:22):
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 strong emphasis on outreach.
So it's very hard to get people excited about bacteria
and people are just like, oh, it's a disease, or
what your hands, or of the use of antibiotics. But

(51:43):
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 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?

(52:06):
And what is going on with this microbe and that microbe?
Oh that's great, Yeah, that's like the Sauer Kraut can
be a foot 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
immediately draws people in because you're like, hey, smell this,

(52:28):
and then they're like, okay, that's really cool. Um boy,
I suppose you can do that with kimchi as well.
UM and sauer kraut. They have like smells and textures
that are exciting, you know, totally. Um, So maybe you
can start off by giving me sort of a character
sketch of lactic acid bacteria as a group. What are

(52:50):
these organisms like, what do we know about them? And
how do you think about them? So lat gas of
bacteria are a whole group, and there's many different you
sees 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

(53:12):
you find, so there's hundreds and you know, so they're
not gonna go around saying this one is safe and
this one 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 electic acid. That's pretty much the basics. Some
of them are a little more complex and they'll turn

(53:34):
things into lactic acid and um acetic acid and CEO
two and so those are the hetero fomentors. They do
more than one thing, so they sort of think they're
making two different assets, whereas the home of fomentors there
is doing one thing. They're just making lactic acid. And
that's the two big groups when you're thinking about lacto acid,

(53:56):
and if I ever call them LBS, it's lactic acid veteria.
So we know lactic acid bacteria are one of 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.

(54:17):
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
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

(54:37):
started on sauerkraut, I think sauerkraut is under utilize compared
to sour dough. But if you've done any fermenting of
souer crout, which I think you shared um do you
know that you don't add a starter so that's sour dough.
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,

(55:02):
or you can make other ferments like adding in carrots
or whatever, and the bacteria, these light casa bacteria just
present on the surface. But the one the first thing
that I did in my project was paid out the cabbages,
and I found that light casa bacteria really low. If
you're looking at the bacteria present on a vegetable, there
are lots and lots of proteo bacteria, many many things

(55:27):
like pseudomonas um, spingle mona. So these are bacteria that
like living on plant leaves, 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 exploited.

(55:47):
It really really high levels of UV light and it
doesn't have a lot of water accessible on the leaf surface.
So leaves are normally covered in a waxy film and
so there's not a lot of nutrients, there's had 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

(56:09):
plant and help them survive. And it's not really the
lactic astive bacteria's way of living, so not really high
like very abundant on the leaf. But when you chop
that leaf up to make your SA 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

(56:30):
out those sugars and you completely change the playing field.
So you've gone from a high oxygen, highlight, low nutrient
condition 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 abiotics selective pressure that

(56:54):
will change who can live. And that's when the lactics
of bacteria really come into their own and they can
start increasing in abundance. Now I mentioned earlier the two
big groups of lactic aso bacteria, the petro fermentors and
the homo fermentors. So at the very start of fermentation,

(57:15):
we get a massive increase in the hetero fermentors, so
as things like luconna stocks and versalia um and they
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

(57:38):
a two phase I wish I had a white water
you could draw it out where you have one population
that increases and then a second population, so a second
wave UM, and that lowers the pH even more. And
as the pH falls um there was proteo bacteria that
we're talking about. They can't survive and they won't they
won't be present at the end of amentation. So if

(58:01):
I'm corrected, this first group the hetero from enters that
produced the multiple byproducts you said lactic acid and acetic acid.
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

(58:22):
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
of the lactic acid bacteria causes the pain of exercise. Well,
it's the same lactic acid. I'm sorry, did I say bacteria. Sorry,
I didn't mean to say that the lactic acid. Yes, yeah, yeah, exactly, yes.

(58:46):
And actually lactic acid is a less harsh acid. So
if it was just fomented by hetero fomentos and it
just we ate a sour crout that was just made
with a stic acid, it wouldn't be that nice. It
would be very very 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

(59:10):
have sour krout, it should have a softer, buttery flavor.
So you have to sort of trust me on this
one and go home and eat some and compare it
to you just straight pickles, which are quite acidic, Because
that lactic acid has a softer um like, it's not
as sharp. Yeah, that's definitely something you notice, is a
difference between quick pickled foods that you use vinegar to pickle,

(59:32):
versus fermented foods where it comes from the bacteria. It's
a much more soft, round, 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

(59:55):
still going to see a lot of different species involved,
right that there can be 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 lact to
basilist broad vis in basically everything at a really high percentage,

(01:00:17):
and then there'll be a lot of UM low numbers
of many other ones. So 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

(01:00:40):
research in Europe, but this is the first United States
sauner Craft survey and we found on average teen point
eight species of lactic gas of bacteria her jar, but
most of them are as some of the really common
lactic gas of bacteria. They take, They take up the bulk.
So would you find any noticeable differences in in like

(01:01:05):
aromas or flavors produced depending on 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 sauerkraw, which is hard to measure

(01:01:25):
in terms of the bacteria that are present because there's
so many other flavors going on. So some kim cheese
are fermented at a lower temperature, and when you're fermenting
in a really cool temperature, like between ten to fourteen
degrees celsius, you're promoting those hetero fermentors, so you get
a different flavor. So there can be a lot of

(01:01:47):
asalia in kimchi, which is less prevalent in souer crawl
like they'll still be there but in lower numbers. But
it's very hard to compare the flavors and attribute that
to the bacteria when you've also garlic, ginger, red paper,
and everything else. That's one thing I found hard in
doing this survey is that every producer might have different vector,

(01:02:10):
but they all have like the slight tweaking of recipes.
So some had like caraway seeds or they threw 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

(01:02:31):
from the farm before fermentation. So where do we have
any idea about where these microbes generally 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

(01:02:54):
to farms or common gardens um in the summer of
twenty seven and team and tried to find environmental sources
of lactics of bacteria. So I took soil and leave
samples and not cabbage leaf um. We'd leaves are things
that were just growing next to crop plants um, and
I found that they had pretty low levels of lacticas bacteria.

(01:03:16):
So I didn't find like a big environmental reservoir of
these bacteria, which I think it's pretty incredible that we
know so much about them in the human micro like
the human got microbiome and probiotics and probiotics and fermented foods,
but very little is known about the ecology, and I

(01:03:36):
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 you are US papers
where honey bees have lacticas bacteria and that gut um,
and they're very specific two bees. Though, I think because
bees taken nectar and then the sugars in the nect

(01:03:58):
you can get broken down by l to gas a bacteria.
But I haven't yet found any evidence that the insects
and the insect droppings go on to be the source
of black to Gasa bacteria and fermented vegetables. So perhaps
a very small amount of black to Gasa bacteria in
soil can then try and like dispussed onto cabbages repeatedly

(01:04:20):
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 where fermentations are prepared, that it's on jars,
it's on spoons and all that kind of stuff that's
been sort of talked about a lot. And I'll have

(01:04:40):
to look up the name for you, but there was
a recent paper where they looked at stuttle Craft facility,
so they I think there 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
Casa bacteria in the environment. They only found levels on

(01:05:00):
the cabbage. But if you're thinking about making sour crowd
in a facility, you're going to 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
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

(01:05:24):
might make one that didn't have enough or didn't have any.
But if you multiply the amount of ingredients, I think
you will always have some amount. I would like to
guess bacteria. Now, was I reading that previously you did
some research with trying to grow sterile cabbage in order
to to inoculate it with bacteria and see how the

(01:05:45):
bacteria did on it. Yeah, I'm very excited about 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 to grow cabbages in glass tubes and they are

(01:06:06):
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 calcaine clay. You
can articulate that. So if you put in the articlave
high heat, high pressure, will be sterile at some nutrient
broth and they're really happy. And now did that research

(01:06:28):
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 do actual competition experiments with large cast of
bacteria and the philosphere microbiome. So the philosphere is the

(01:06:51):
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 eat a particular microbe to
grow with or there's competition. So I made all of
this sterile cabbage. It took me years and then I
inoculated it. We lead Casa bacteria and they don't grow.

(01:07:12):
Like if you just spray a cabbage with lat 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 or the lactic 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 find with

(01:07:35):
or without a microbiome. I sprayed some yeast on cabbages
once and they didn't enjoy that. The cabbages brown and
just with it. But bacteria 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 pseudomonist that I mentioned. So things like that break

(01:08:00):
them on the cabbage and they will increase and you
will see like they're happy growing on a cabbage. The
lattic as a batteria tank. 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 gust Wow.
So we know that obviously these lactic acid bacteria are

(01:08:22):
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 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

(01:08:42):
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 papers from a long time
ago stating at yeast um sometimes found as spoiler organisms.
But when I did this North American sourkrout survey or
fermented vegetable product survey, so it was sour karts and

(01:09:04):
kin cheese. I found over half of them had yeast,
like a lot, a lot of yeast, Like some of
them had more counts of yeast than bacteria, which I
was really surprised by. So the FA 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

(01:09:24):
not toxic, but everything that you read says the undesirable
and fermented vegetable products because they give musty, yeasty, sort
of dankish flavors I guess, and they can form a film,
which I think is pretty off putting if you're trying
to create a new product and that's covered in a
yeast film. Yeah, you want your sour smell like skunky beer. No,

(01:09:47):
definitely not, it's already Yeah, so tough. So I when
I had this, I had fifty one jars and I
was delighted, and I was like, Hey, who wants some?
And I would. I opened and sampled them all in
the conference room, a smaller room than the toughs, and
people were not happy. They're like, Wow, the whole room
stank for a week. I think it's just in an

(01:10:09):
enclosed space. Opening fifty jars of sauer kraut and kim
schi was a little much, but yeah, and I tried
to eat them all, but I I really couldn't. That's
a lot. But you couldn't eat fifty jars of kimchi
by yourself or sauerkraut and kimchi. No. I tried so
hot and I can do it. And part that's why
I wrote the grant, as like, now I can get

(01:10:31):
to eat all of it. If I write a grant
that says I need to buy them all so well,
that makes me think you you correctly guessed that. One
of the things that got me interested in talking about
kimch 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 kimchi

(01:10:53):
for years, and I've always put off trying to make
it because it seemed like a scary, daunting, potentially 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 kimchi or

(01:11:16):
some other lacto fermented vegetable. Is this something that's probably
gonna poison you if you screw it up, or is
it pretty forgiving. That's that's a great, great question, because
I think people are really scared, and when people come over,
they're like, because I have a lot of ferments on
my friends these days, but they're actually pretty safe. Anything
that's anaerobic, um, you're really really making it very hard

(01:11:40):
for things like equally and mysteria to grow. 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

(01:12:00):
probably not an official thing to say, so basically, 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,

(01:12:22):
like you're just taking random ingredients and salt, and yet
it works so consistently um worldwide. 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,

(01:12:43):
what do you find amazing about fermentation? Well, that bacteria
that we don't know how they where they live in
the environment. We can't find them in the environment get
into everything that we eat, and a consistent like it's
amazing we can't try them, but all over the world
there's it's the same species and you can't follow it

(01:13:06):
from a field to a cabbage. You know, that's amazing.
That is amazing. Uh, I don't know. 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 you, I guess you don't see any microbes with

(01:13:26):
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, it's it's amazing.
Like I was trying to write a review on dispersal,
like how do how does a bacteria get from here
to that? And you can read about the moving miles
and thousands of miles on wind. It just gets in

(01:13:48):
the wind and just dispersed. But you you've got no
way of really knowing unless you sort of make genetically
modified bacteria and release them, which I'm not going to you,
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

(01:14:09):
been working on recently that you wanted to talk about? Well,
I I was gonna say, and I forgot to mention
that I am doing community assembly experiment. 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

(01:14:30):
competing the yeast and the bacteria together in little jaws
of sterile vegetable extract too, and I put them under
different conditions, like different temperatures, different salt concentrations, um and
using different cabbage extracts of red cabbage, grain cabbage, and
Napa cabbage to see if any of those influence the

(01:14:50):
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 used. So maybe the North American fermenters are using
different conditions and that's why the ferments have more used.
But I'm still working in it. Interesting. So, if if

(01:15:12):
you're making kimchi at home or making sarokraut 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
put it in the basement or somewhere a little cooler.
And I did notice that if you don't put salt in,
it can go horribly wrong. The pH just doesn't fall

(01:15:34):
as much because I tried that, and I was even
adding like to cast of bacteria, and the pH wasn't
dropping as well as it should with two. But there
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

(01:15:57):
of bacteria and microbes to thrive. But the to gas
in bacteria or tolerant of salt is that it is it.
That's what I always assumed um and think is right
when you have just regular cabbage. But I was using
sterile felted vegetable extractures, you know, so just completely sterile
media and adding lac to gas of bacteria in the east,

(01:16:18):
so they allowed to gas about. You 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. So maybe the salt is even helping it
in some way. I think there's going to be something
going on with the salt as well. M M, well
that's very interesting. Yeah, all right, well, I think we

(01:16:41):
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 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

(01:17:03):
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
other episodes of Stuff to Blow your mind, you know
where to find us. That is, wherever you happen to
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review and subscribe. Those are just simple things you can

(01:17:24):
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(01:17:48):
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