PIA SORENSEN: So, welcome.
Welcome, everyone.
Who is here for the first time?
I love that.
Wonderful!
Welcome.
So this is the Science of
Cooking Public Lecture Series,
and we do this every Monday at 7:00 PM.
And very soon, I'm about to
introduce Sandor Katz, who
is going to talk to us about
all things fermentation.
But first I just want to
put this into context.
So who was here last week?
Wonderful.
So for those of you who are
new, you know that we're
playing a little game every week?
Yeah?
Do you know?
So if you paid very
careful attention to what
happened last week when Chef
Lydia Bastianich was here,
you had the chance to win prizes.
And in order to do that, you
have to answer a question.
The prize is these aprons, which I'm
going to try to do with one hand--
aprons with equations.
[APPLAUSE]
So we clap for equations.
So Lydia made risotto.
And she said it's very important
to make risotto in a wide saucepan
rather than in a deep saucepan.
Why is that?
Yes.
[INAUDIBLE]
The increased area of the saucepan
allows all the greens to cook evenly.
Anything else you may want to add?
Yeah.
Good.
There's more area for
liquid to evaporate.
OK.
Next question.
As Chef Lydia slowly cooked
the rise for the risotto,
a component that contributes to
that creamy base of the risotto
was pulled out of the
rice and into the sauce.
What is the name of this component,
and what kind of macromolecule is it?
That's two questions.
But you get an apron.
Anyone?
Yeah.
AUDIENCE: A starch and a carbohydrate?
PIA SORENSEN: Do you know the
name of the specific starch?
Anyone?
Yeah?
AUDIENCE: Amylopectin.
PIA SORENSEN: Amylopectin.
[APPLAUSE]
OK, I think this one is easier.
So Chef Lydia claims that it is very
important that the stock is hot.
So she had a pot of
risotto, and then she
had a stock which she was adding to
the risotto just one little at a time.
And she claimed that it's very important
that this stock is also kept hot.
It can't be at room temperature.
Is it true that it has to be hot?
OK, raise your hand.
Yes.
It is important.
I could have asked you to show me why.
So if you were here, you remember the
equation of the week, which was this.
[APPLAUSE]
And if you were a student in
this class, on your homework--
which is actually due tomorrow,
so please don't spread the word--
you would have calculated how much this
affects the temperature of the stock.
So if you add, early
in the cooking process,
you add one ladle stock to it-- you
don't have to pay attention to this--
the final temperature, after you've
added a ladle of stock to your risotto,
is 72 degrees Celsius if you do
it early in the cooking process.
If you do it late in the
cooking process, it's about 82.
So yes, adding that
ladle of stock actually
does bring the temperature down by like
20 or 10 degrees, which you can imagine
is enough to actually not really keep
the risotto at the right temperature.
So these equations
are useful, sometimes.
OK, so that's it for aprons.
So last week, we cooked with heat.
Lydia added all kinds
of things to water,
but basically what she did, from
a scientific standpoint, was
she added grains to water
and then she added heat.
And then she waited.
That was basically it.
This week, we're going
to cook with microbes.
So you would think at first glance
that these are kind of opposite ways
to cook.
Most of you know that
adding heat to food
is what sanitizes food,
is what kills microbes.
And when we cook with microbes,
as Sandor will tell us,
you really want to make sure that you
keep those microbes not just surviving
but happy, thriving, dividing, doing
their thing so they add flavor,
preserve the food, do their thing.
So that's kind of our goal for today.
And the reason for this is that
microbes are busily banks of enzymes.
Enzymes are basically proteins.
Usually when we cook food,
we mess with proteins, right?
If you cook a steak, you're
messing with the proteins.
If you're whipping egg white, you're
actually messing with the proteins.
If you are cooking an egg,
you're denaturing the proteins.
You're messing with the proteins.
Now if you messed with the proteins
inside these cute little yeast,
you would be messing with all of
these enzymes and the yeast would die.
So you don't want to do that.
So they may seem opposite, but
they have actually a lot in common.
So one of the things that cooking
with heat and cooking with microbes
have in common is it's something
humans have been doing for millennia.
So I guess the most
current number for how long
we've been doing this is fish
found in Sweden, actually--
that is 7000 BC, so 19 years old
is some of the earliest evidence.
Our second earliest evidence
is similarly about 7,000 B.C.
is beer, ancient beer recipes in China.
So this is something how
humans have manipulated foods
in this way for way, way, way back.
The other thing that cooking with
heat and cooking with microbes
have in common is that
they're really simple recipes.
I mean, cooking pasta--
you add pasta, water, heat, done.
Here is sauerkraut-- add sauerkraut,
a little salt, time, wait, wait.
But then you're done--
eventually you're done.
So simple-- really simple recipes.
You know, often when
we think of cooking,
we think of these complex things.
You add this, you do
this, it's very complex.
You have to have a lot
of skill and training--
not necessarily that hard.
The other thing that cooking with
heat and cooking with microbes
have in common is they
break down larger molecules.
So the large molecules of food, the
proteins, the carbohydrates, the fats--
you break those down when
you cook, say, a steak.
So the delicious molecules
on top of a brown steak--
it's due to the breaking
down of the proteins.
And similarly, when
you ferment, say, milk,
you're basically breaking down the
long carbohydrates in the milk,
adding lots of microbes.
And over time, you're getting
these beautiful flavors,
but they come from that milk.
They come from the long, big molecules.
It's the breaking down of them that
creates this beautiful, new flavor.
So very quickly-- so microbes
are good at what they
do because they divide really fast.
And I like this.
I usually do this.
So if you have one bacteria, it
divides and makes two bacteria.
Then the first one dies, and each of
these create two new ones, blah, blah,
blaH.
They keep doing this.
And over time, you get
something like this.
[APPLAUSE]
Good, good, good.
So you can put all this
together in an equation.
The equation looks like
this, and it basically
says that if this much time elapsed
and if the time of a generation
is this long--
so the time of a human
generation is like 30 years--
microbes, 20 minutes, 30
minutes, an hour to two hours.
You plug it in.
You can basically find
out how many there'll
be after a certain amount of time.
So as I thought we should do an
experiment, do a little calculation.
So question number seven--
this is an old homework problem.
E. coli divide every 20 minutes.
If the spinach you had
for dinner at six--
that's an hour ago--
and there was one bacteria
on it, how many extra E. coli
do you currently have in your body now?
It's seven.
And how many do you have
tomorrow morning at 9:00 AM?
So you can do your
exponentials in your head.
I'm sure you're good at that.
But I can also just show you.
So after an hour--
so two-- after an hour we have 60
minutes, the time per generation
is 20 minutes.
So now you have about eight
E. coli in your stomach.
It's OK.
Tomorrow morning-- that's about 15
hours later, an hour is 60 minutes,
over 20 minutes, lots
and lots, 10 to the 13.
And if every E. coli weights
ten to the negative 10 grams,
that means you would have three
kilograms of E. coli in your belly
tomorrow morning.
That's a lot.
That's why exponentials are amazing.
You produce all lot of microbes.
Is that true?
Is that going to happen?
Yes or no?
Why Stomach acid?
[INAUDIBLE]
The early generations die.
They run out of nutrients.
Yes, exactly.
In order for them to divide
and build that biomass,
they would have to eat
stuff in your stomach.
And so they would have to eat of you.
So they run out of nutrients,
and they can't divide that much.
You'll still have some
E. coli, and you still
may get sick, but maybe not as sick.
OK so things to think about
as we go into this lecture.
So it is a great honor for me, huge
honor for me, to introduce Sandor Katz.
Sandor Katz is one of the great
fermentation experts of our time,
and we go way back, by like
two years, because Sandor
has Skyped into my classes and
talked to my students for years.
And so it's super exciting for me
and many of the people on the staff
to finally have him here.
So please welcome Sandar Katz.
[APPLAUSE]
SANDOR KATZ: All right, well, thank you.
Can everybody hear?
OK, great.
No more equations.
So OK, what I want to start with is
just addressing the question, what
is fermentation anyway.
But first, I want to do a little poll.
How many people here would
say that they have eaten
or drunk something fermented
in the course of this day?
OK, I'm seeing a lot of
hands, maybe most hands.
But I would bet that most of the people
who didn't raise their hands actually
have eaten something
fermented already today.
Almost every individual in
almost every part of the world
eats and drinks products
of fermentation every day.
So if you're here in Cambridge and sort
of eating a standard American diet,
maybe you had some coffee this morning.
Coffee is fermented.
Maybe you ate some bread.
Bread is fermented.
Maybe you had some cheese on that breed.
Cheese is fermented.
Maybe you had salami or some
other kind of cured meat
on that bread, which is fermented.
Maybe you had a salad
with salad dressing
that included vinegar,
which is fermented.
Maybe you ate some chocolate,
which is fermented.
Maybe something with vanilla
in it, which is fermented.
But an incredibly diverse range
of everyday foods and beverages
are products of fermentation.
And what is it that unites
all of these disparate foods.
They're all produced by
the transformative action
of microorganisms.
And from a food and
beverage perspective,
that's how I would define
fermentation-- it's
the transformative
action of microorganisms.
Now I imagine we have some
biologists in the house,
and the biologists are already shaking
their heads because, for a biologist,
fermentation means
something a little bit
different than that-- something
that's both more specific, and also
a little bit broader.
For biologists, fermentation describes
anaerobic metabolism, the production
of energy without oxygen.
And in fact, the cells of our
bodies are capable of fermentation.
And mostly we operate with respiration.
And the most efficient way that our
cells produce energy is with oxygen,
and we have this elaborate
system to distribute oxygen
to each of the cells of our bodies.
But if we exert ourselves in ways
that sort of demand energy beyond what
that oxygen can
facilitate, then our cells
revert to this fermentive mode of energy
production, which is less efficient.
It produces this byproduct
with lactic acid,
which can be responsible for
giving us that feeling of a muscle
burn when we exert ourselves.
Now how does this relate to
these foods and beverages?
Most of the foods in beverages
that we describe as fermented
meet the biologist's definition.
They are anaerobic.
When we turn this bowl of
cabbage and other vegetables
into sauerkraut, that's an
anaerobic process that does not
require oxygen. When we take milk
and fermented into yogurt, that's
an anaerobic process that
does not require oxygen.
When we take grape juice
and ferment it into wine,
that's an anaerobic process
that does not require oxygen.
The reason why I typically depart
from the biologist's definition
of fermentation is that there are a
large handful of microbial transformed
foods and beverages that do
require oxygen. So if any of you
like to drink kombucha, a kombucha
is an example of an aerobic ferment,
call it an oxymoronic
ferment because it's
a microbial transformation
that requires oxygen.
But everybody thinks of it as fermented.
Similarly, vinegar
requires oxygen. Similarly,
many types of cheese require oxygen.
The Indonesian soy ferment tofu--
I'm sorry, tempeh requires oxygen.
So because there are all of
these microbally transformed
foods that don't meet the biologist's
definition of fermentation,
I like to work with this
broader lay definition
that fermentation is the transformative
action of microorganisms.
However, not every transformative action
of microorganisms results in something
delicious that we're ready
to put into our mouths.
And for most people,
our primary awareness
of the microbial transformation of food
comes when we clean the refrigerator.
In the deep recesses
of the refrigerator,
you find decomposed vegetables and
things that have begun to mold.
And that's also the transformative
action of microorganisms.
But we don't call that fermented.
We have a different
vocabulary to describe that.
We call that rotten.
We call that spoiled.
And we reserve the word fermentation
to describe intentional or desirable
microbial transformations.
But I think the fact that
we all inevitably experience
food decomposition maybe
can give us some insight
into the inevitability of microbial
transformation of our food.
Now in terms of science and
cooking, one of the things
that's most fascinating
to me about fermentation
is that people have been
practicing this for 10,000 years--
I would argue longer, that what the
archaeological record really as is
finding is it's telling us
about the history of pottery.
And that's when pottery emerged and
that the earlier vessels were all
biodegradable.
So we're not finding remains of them.
But anyway, who knows?
But the people who figured
out fermentation techniques,
they didn't have the
benefit of microbiology.
They didn't know about microorganisms.
And what we now understand is that all
of the plants and all of the animal
products that make up
our food are populated
by these elaborate
communities of microorganisms.
So the question is, are
these microorganisms going
to decompose our food
into something disgusting
that nobody would ever
put into their mouths,
are these microorganisms going to
create toxic byproducts or make us sick,
or are these microorganisms
going to somehow elevate the food
and make it more delicious,
more stable, more digestible,
or improve the food in some way.
And without knowing about the
existence of microorganisms,
people in every part of the world
figured out through observation,
through trial and error,
through happy accidents,
who knows how they figured it out how
to guide the microbial transformation
of the food.
And really what the practice
of fermentation amounts to
are manipulations of
environmental conditions
that determine which of the multitude of
organisms that are present on anything
that makes up our food are
going to develop and in what way
they will be transformed.
So a head of cabbage--
here, I'll be referring to this
repeatedly through the evening.
But if we just left a
bowl of cabbage like this
sitting on the counter for
two weeks or two months,
it is not going to turn
itself into sauerkraut.
And it's really quite predictable
what's going to happen.
And some of us have seen
the early stages of this--
like maybe you had a piece
of cabbage like this leftover
from something you cooked.
And let's just say there was no
room in your fermentation slowing
device, your refrigerator, and
you left it on the counter,
and you didn't get back to it the next
day, and it sat there for a few days.
Has anyone ever seen like
a little film of a mold
develop on those cut surfaces?
And you can still use the cabbage.
You just sliced those away.
But where the carbohydrates are
losing out in the presence of oxygen,
mold is going to grow.
So it's possible to have a bowl of
cabbage turned into a cloud-- oh, here,
you're not gonna see where it's--
it's possible to have a bowl of
shredded cabbage turn into kind
of a cloud of mold that
could literally reduce
that cabbage into a
puddle of slime that bears
no resemblance to delicious,
tangy, crunchy sauerkraut.
Also, I mean not to
scare anyone about eating
cabbages or other raw
vegetables, but the bacteria that
produces the scariest food
poisoning pathogen that we know of,
Clostridium botulinum, which
produces a toxin called botulism,
it's such a common soil bacteria
that probably none of us
have ever eaten a vegetable
in our lives that didn't
have cells of Clostridium botulinum.
But we really only ever hear about
botulism in the context of canning.
So if you sterilize
food in a jar in order
to preserve it but you
fail to use adequate heat,
Clostridium botulinum can survive
higher than boiling temperatures.
So what you do is you sort
of kill everything else
and leave that as the sole survivor
in the very contrived environment
where it can thrive in the
total absence of oxygen--
obligate anaerobic.
It can only function in
the absence of oxygen.
We don't really spend much of our time
in a totally anaerobic environment.
So when you chop up cabbage to make a
coleslaw or to ferment into sauerkraut
or to make a stir fry, you don't
have to worry about the botulism.
It's only if you put it in that
specific environment where it can grow.
So there's a lot of potential ways
that a cabbage or a glass of milk
or a glass of grape juice or
anything that we could eat--
there's a lot of different ways
that it can microbially transform.
And which of the microbes that
are on it are going to develop
is entirely an environmental question.
And so fermentation is all
about manipulating environments
to encourage the growth of
certain kinds of organisms
while simultaneously discouraging the
growth of other kinds of organisms.
So I mean, what we'll be doing
eventually with this bowl of cabbage
is we're going to get the vegetables
submerged under their own juices.
And that just protects them
from the free flow of oxygen.
So the molds can't grow.
It's not totally anaerobic.
There's dissolved oxygen in the water.
So the Clostridium botulinum
can't grow, and in that sort
of protected environment the lactic
acid bacteria, which are generally
believed to be present on all plants
growing out of soil on planet Earth,
they can thrive and flourish.
And as they acidify
the environment, they
kill off most of the other
organisms that are present.
And that's part of what enables the
food to be so effectively preserved.
So fermentation is the transformative
action of microorganisms.
There is no food that
cannot be fermented.
It doesn't mean every food has equally
prominent traditions of fermentation.
Avocados are like an
example of a food that, I
don't think that there's
much tradition of fermenting.
But I've put avocado in sauerkraut.
It works great.
And nothing that we could possibly
eat could not be fermented.
And then a related issue is
fermentation is practiced everywhere.
I definitely do not possess encyclopedic
knowledge of culinary traditions
everywhere in the world.
But I've been looking really
hard for counter-examples
for more than 20 years,
and every time someone
has proposed I'm a part of the world
where they believe that fermentation
is not practiced, I've
been able to learn
about a fermented food or beverage
from that part of the world.
So I think it would be conceptually
possible for hunter-gatherer people
to live without fermentation.
If you're going to spend each day
procuring the food resources that
are going to get you
through that day, you
don't really have to think too
much about the dynamics of how
food fares over time.
But as people in different
parts of the world
transitioned from hunter-gatherer
societies into agricultural societies,
if you're going to invest
your energy and your resources
into crops that are ready at
a certain moment of the year,
then that is only feasible
as a strategy for survival
if you have some
strategies in mind for how
you're going to preserve the harvest to
get you through the rest of the year.
So I would argue that
agriculture itself would not
be possible without fermentation.
It's not the fermentation is the
only ancient method of preservation,
but most of the ways that
we preserve food today
just hadn't existed in the past.
I mean, OK, we can't even imagine
how you live without a refrigerator.
And if we were sitting
here just 100 years ago,
nobody would have a refrigerator.
And bear in mind that most
households on planet Earth in 2017
do not have a refrigerator.
Refrigeration is not
universally available.
And so people use other
techniques for preserving food.
Then, we might think about canning.
Some of us might think of canning as
an old time preservation technique
because we mostly associate it with
a grandparent or great grandparents
or something like that.
Canning is a 200-year-old technology.
It was patented in France in 1812,
where it's called up appertization
because they remember
the name of Nicholas
Appert, the clever Frenchman who
invented the process of sterilizing
food in a jar.
So if you take away refrigerators
and freezers and canning,
there aren't that many other
methods of preservation.
There's drying food.
Drying food preserves food
basically by depriving
the microorganisms that are
on the food of the water
that they need in order to function.
So dried foods are not sterilized
in the way that canned foods are.
The microbes are present, but
they're in a state of dormancy
because they lack the water that
they need in order to function.
And certain foods are just
dry when they're mature.
That's their nature-- any kind of grain,
any kind of bean, any kind of nut.
They're just dry when they're mature.
Other foods can be dried, like fish
or meat or fruit or vegetables.
Really any food could be dried.
And then beyond that, fermentation
has been just a major way
that people have preserved food.
Sauerkraut, kimchi, pickles--
these are all strategies for people
in temperate parts of the
world to preserve vegetables
from the limited season when
they can be grown to get people
through the rest of the year.
Cheese, we mostly think about
cheese as something that's tasty
and something that you
walk into a gourmet store,
and there's all these different choices
and exciting flavors and textures
and all that.
But I mean, really what
cheese is preserved milk.
Cheese and yogurt and kefir and
other forms of fermented milk
really are strategies for
extending the life of this,
or the usefulness of this you
know extremely perishable food.
Salami-- you walk into a
delicatessen, and the salami
is just like hanging from
a string in the ceiling.
I mean, that's preserved meat.
You take this animal that
you've been feeding for months,
and you know it weighs 300 pounds.
And you can't eat it all at one sitting.
So you have to have strategies to
preserve the meat so you can eat it
over a longer period of time.
And that's what all cured meats are.
So preservation has been just an
incredibly, incredibly important reason
why people ferment.
I wish I could say that I got
interested in fermentation for something
as high minded as that.
But what first made me start
thinking about fermentation
was the flavors of
fermentation, and fermentation
creates compelling flavors.
And if you walk into a
gourmet food store anywhere,
most of what you're going to see and
smell are products of fermentation.
And most of the world's
greatest delicacies
are products of fermentation.
And fermentation creates strong flavors.
Of course with strong
flavors, not everybody
loves every flavor of fermentation.
And I think cheese
illustrates this so well.
So as my taste has evolved--
and I wasn't born like this-- but
like I love stinky, stinky cheese.
And if I can smell it
from hundreds of it away,
it-- just catches my attention,
and I'm dying to try it.
And I'm so sure not
everyone in here would share
my passion for stinky cheeses and.
Whenever I have a really very
ripe, sticky piece of cheese
and I invite some friends over
to share it with me, inevitably
somebody gets to the door and
just makes this awful face.
And they're thinking, did
something die in here.
And they would never ever
think about putting something
that smelled like that into their
mouths, and the world of fermentation
is just full of these strong flavored.
They're what we would
call acquired tastes.
You're not born loving a stinky cheese.
You're not born loving surstromming,
the Swedish low salt fermented Herring.
Just the stronger
flavors of fermentation,
people learn to like through exposure,
through seeing other people get excited
about them, through being willing to
taste them a second and a third time.
So flavor is a very important
aspect of fermentation.
What's getting a lot
of people interested
in fermentation at the present
moment is perceived health benefits.
So I want to just address
that a little bit.
It's not like all of these foods
have precisely the same qualities.
It's not like coffee and bread and
cheese and kimchi are all the same.
They're all different.
They're all based on different
foods that have different qualities,
the fermentations are
different, every food is unique.
But the process of fermentation
transforms nutrients
in some very clear patterns of ways.
The first way Pia referred
to in her introduction,
and that is what I would call
pre-digestion and the idea
that, while the food is fermenting,
the bacteria or the fungi that
are fermenting it are breaking down
nutrients into more elemental forms.
And frequently these simpler
forms are easier for us to access.
I would say that the most dramatic
example of this is soybeans.
The reason why the vegetarian
subcultures of the West
became so interested in soybeans
and they became almost a singular
replacement for meat and
milk is that soybeans
are considered to be the plant food
with the most concentrated protein.
But you really never
hear about people just
you eating a plate of
soybeans for dinner the way
they might with lentils or chickpeas.
And the reason for this is that
our human digestive systems are not
capable of breaking down
the protein in soybeans.
And it won't kill you if you eat
a plate of soybeans for dinner,
but it'll make you really gassy.
It'll give you terrible
indigestion, and you're not
going to get the protein
out of the soybeans.
And so somehow thousands of
years ago, the Asian cultures
that pioneered soy
agriculture recognized
the indigestibility of
the soybeans and figured
out how to make soybeans digestible.
And we have this whole range
of fermented soy foods.
There's soy sauce.
There's miso.
There's tempeh.
There's natto.
There's really like dozens
of other variations.
The four that I mentioned
are very different in flavor,
they're different in texture, they're
different and fermentation processes,
they're different in the
organisms that ferment them.
But what they all have in
common is that that protein
gets broken down into amino acids,
the building blocks of proteins.
Similarly, when you
ferment milk, lactose--
the milk sugar that so many people have
a hard time digesting-- breaks down.
And many people who can't drink a glass
of milk have a fine time eating yogurt.
But of course, it's not
a question of yes or no.
It's a matter of degree,
and most commercial yogurt
that's available I mean the assumption,
at least in the United States,
is that people want their
yogurt minimally sour.
And so most commercial
yogurt in the United States
is fermented for about
2 and 1/2 hours, which
is enough to just set the yogurt
but without making it too sour.
But what the sourness is is lactic
acid, and that's with the lactose
is being transformed into.
So the more sour it is,
the less lactose there is.
So if you make yogurt
yourself at home, instead
of fermenting it for 2 and 1/2 hours,
you can fermented for eight hours.
You can fermented for 12 hours.
You can fermented for 24 hours, and
you'll have a different product.
It'll be more sour, but there
will be less lactose to it.
That's pre-indigestion.
Even gluten, the notorious wheat
protein that so many people
have a hard time digesting, can
be broken down by fermentation--
not by yeast, but by bacteria.
And yeast you can go
to any store and buy.
Yeast has been present
with us forever, and people
have been making bread for something
like 10,000 years and using yeast.
But until Louis Pasteur isolated
yeast in the 19th century,
yeast was never alone.
Yeast has always been
used with the bacteria
that it travels with-- so on the wheat
itself, like on grapes or on barley.
The yeast is there, but it's not alone.
It's with lactic acid bacteria.
So what we now call sourdough,
which is natural leavening--
which is really how bread for
the first 1900 years was made.
The fermentation included
not only yeast but bacteria,
and those bacteria
can break down gluten.
So there's a much lower level of gluten
in bacterially fermented bread or bread
made with natural leavening
or a mixed culture.
And this question of mixed cultures
is really kind of essential
because until the emergence
of the science of microbiology
there was no such thing as
singular microorganisms.
Microorganisms are everywhere,
but they're never alone.
They always exist in communities
and in pretty elaborate communities.
And we've all been reading a
lot about the human microbiome
over the last couple of
decades, and more and more
is known and understood about that.
And each of us is host to something like
a trillion bacteria, many more bacteria
than we have human cells
with our own unique DNA.
I mean, the carrot and the
cabbage also have a microbiomes.
Every living thing has a microbiome,
has its sort of simbiance
that they live with.
But there are always these
elaborate communities.
It's never one singular micro-organism.
Pre-digestion-- OK, I got
off on a little tangent.
A flip side of
pre-digestion is in addition
to breaking down nutritious
compounds, fermentation
can break down toxic compounds.
So there's all kinds of toxic
compounds in different kinds of plants
that fermentation can break down.
And some of them are dramatic,
like cyanide in cassava.
Cassava in certain parts of the world
grows with these extraordinarily high
levels of cyanide.
And if people were to eat
unprocessed cassava roots,
they would literally kill them.
And yet it's this very
important source of nutrients
for about a billion people around
the equatorial regions of the world.
And so in the parts of
the world where cassava
grows with high levels of cyanide, one
of the major strategies for removing
the cyanide is fermenting it.
And it's very simple.
You peel it.
You coarsely chop it, put it
in a vessel filled with water
that initiates a fermentation.
And it breaks down the cyanide
compounds into benign forms.
A lot of food toxins are not
quite as dramatic as that.
Oxalic acid found in a lot of
vegetables breaks down by fermentation.
Phytic acid, which is found in
the outer layers of seed foods,
breaks down through fermentation.
There's even some evidence showing that
residues of organophosphate pesticides
can be broken down through fermentation.
So all kinds of toxic
compounds and foods
can be broken down by fermentation.
Then another interesting
aspect that's really
just beginning to be investigated
are the metabolic byproducts
of fermentation.
And a lot of them are turning out to
have interesting therapeutic potential.
So for instance, in sauerkraut
and other fermented vegetables,
there are these compounds
called isothiocynates which
are regarded as anti-carcinogenic.
And they're not found in the
vegetables you begin with.
They're generated by
the lactic acid bacteria
over the course of the fermentation.
Natto, the Japanese soy ferment--
that's never really caught
on in our part of the world
because it's got a slimy texture
and it's an example of
an alkaline ferment.
So it sort of smells a
little bit like ammonia.
I know.
I'm making it sound very appealing.
But it's actually incredibly delicious.
And in that slimy coating
that develops on the soybeans
is this compound called
nattokinase, and you could go in
and any vitamin supplement store in
North America and buy nattokinase
that's been extracted from
natto because so many people
are taking it because it's
been found to dissolve fibrin.
Fibrin-- when you hear about people
with clogged arteries, the fibers that
build up inside of our blood
vessels, that's fibrin.
And this compound that's a metabolic
byproduct of bacillus subtilis
as it ferments soybeans actually
can break that fiber down.
And so a lot of people are
taking it in therapeutic ways.
Then finally, what I
would consider to be
the greatest potential
benefit of fermentation
would be the bacteria themselves.
So I talked a little bit
about the microbiology.
I mean, all of us older people here
who grew up through the 20th century,
we were brainwashed with this idea
that bacteria are our enemies,
bacteria need to be avoided.
And when they are encountered
bacteria need to be destroyed by any
means necessary.
And science is actually telling a
much more nuanced story these days.
Bacteria are the matrix of all life.
There's an emerging consensus
in evolutionary biology
that all life is
descended from bacteria.
The flip side of this is that
no multicellular form of life
lives without bacteria.
And just as we're dependent on
these trillion microorganisms that
are part of us, so too is the cabbage
and the carrot and the cow and the pig.
And really everything we
eat has its own microbiome.
And yet we're still in this
war on bacteria mentality,
and we all have chemical
exposure to compounds
that are designed to kill bacteria,
whether it's antibiotic drugs,
whether it's anti-bacterial
cleansing products, whether it's
the chlorine that's on all of
our municipal water systems.
But we all have exposure
every day to these compounds
that are designed to kill bacteria.
And luckily none of
them kill all bacteria.
But what they do is they
diminish biodiversity.
And we think a lot about biodiversity in
terms of the oceans and the rainforest,
but biodiversity is a concept that
applies inside our bodies as well.
And as we learn about the incredible
range of our functionality
that involves bacteria,
we're also learning
ways in which we are hurting ourselves
through this chemical exposure that
diminishes our biodiversity.
So I mean, bacteria in our bodies do
way more than enable us to digest food.
I mean, that's a very
important thing, that bacteria
enable us to effectively digest food
and assimilate nutrients from food.
What we call our immune
systems are largely
the work of bacteria in our intestines.
In the last few years has been
incredible groundbreaking work
demonstrating that serotonin and
other compounds that determine
our neurological function--
how we think, how we feel--
are regulated by bacteria
in our intestines.
And it turns out that nearly
every process in our bodies
involves these bacteria, and yet
we continue killing them all.
And so this has given rise
to what is called probiotics.
It's the antidote to
antibiotics to ingest bacteria.
And there's a huge industry of you
know little capsules that you can buy,
probiotics.
And each of these capsules
is saying, oh, this
is a billion cells in
this little capsule.
Well, it's a billion
copies of one or two
or three different bacteria which
has limited impact on biodiversity.
The current contrast to that would
be traditional fermented foods, none
of which involve singular bacteria.
They all involve these elaborate
communities of bacteria.
And so when we ingest
living fermented foods,
I mean we are promoting
biodiversity in our gut.
And we don't fully understand it at all.
I mean, there are elaborate interactions
between the bacteria we ingest
and the bacteria in
residence in our intestines.
The earliest articulations of the idea
of probiotics Elie Metchnikoff writing
110 years ago.
I mean, his vision of it was you eat the
yogurt, and the bacteria of the yogurt
just take over the intestine
and make everything better.
And it's a highly competitive
environment in there.
It's not like the bacteria in
residence in our intestines
just sort of move over and
make room for the new bacteria
in the yogurt to take up residence,
but there is an elaborate interaction.
And part of that interaction
is a genetic interaction.
And one of the most fascinating
things about bacteria
is their genetic flexibility.
So in contrast to us and
animals and plants and fungi--
which all have fixed genetics
for the course of our lives--
bacteria aren't constrained in that way.
Bacteria are extremely
genetically flexible.
They can exchange genetic information.
They can pick up genetic
information from the environment.
They can get rid of
genetic information that's
no longer relevant to their existence.
And so part of that interaction
is a genetic interaction.
All of that said, I think that
fermented foods are very important.
I think there's also a lot
of unsubstantiated hype.
There are web sites telling people
that, if they drink kombucha everyday,
their diabetes will go away,
your hair will never get gray,
you'll reverse aging.
I mean, there's a lot of ridiculous
things that the people are saying.
But I mean I think that
the underlying idea
that there is great potential when we
ingest bacterially rich food to improve
digestion, improve immune
function, potentially improve
mental health and other systems of the
body without any risk, is significant.
OK, now let me talk a little bit
about some fermentation concept.
So the first book that I wrote about
fermentation-- my books are up there.
I'm going to do a little
book signing after--
was called Wild Fermentation.
I didn't make up this expression.
It's found throughout the literature,
and it describes something specific.
While fermentation is fermentation
that is based on the organisms that
are present on the food
like nobody-- well,
I won't say nobody uses
starters to make sauerkraut
because people are selling
starkers to make sauerkraut.
But I mean it's totally unnecessary.
Lactic acid bacteria are
present on all plants.
There's no reason to add a
starter because you'll find
the bacteria you need on all plants.
You don't need yeast
to make wine either.
I mean, nobody had used to make wine you
know until Louis Pasteur did his work.
I mean, you crush the grapes.
The yeast and bacteria are
on the skins of the grapes.
They initiate the fermentation, and
they transform the sugars into alcohol.
And then if you don't protect it from
oxygen, other bacteria that are there
will transform alcohol into acetic acid.
But that's wild fermentation.
It's just sort of basing your
fermentation on the organisms that
are spontaneously present.
The contrasting style of
fermentation, no less wonderful,
is when you introduce
some sort of a starter.
There's basically three different
categories of starters I would say.
I reference the packet of yeast.
That's something that Louis Pasteur and
the emerging science of microbiology
made possible, isolating
singular microorganisms.
Yeast is the most common one.
If you wanted to make Camembert
cheese here in Cambridge,
initially it was done as a
wild fermentation with raw milk
in a certain cave system in France.
But if you could simulate
the temperature and humidity
conditions of those caves,
you can go on the internet
and you could buy the right
bacteria and the right fungus
and follow procedures
that have been outlined,
and you could sort of simulate the
conditions of the caves of France.
And you could produce Camembert
cheese in your apartment in Cambridge.
I make koji, which is a Japanese
rice with a fungus grown
on it that's the starter for
making soy sauce, for making miso,
for making Sake, for making
Amazake and many other foods.
And so I buy imported from Japan
a fungal starter to make my koji.
But what's important to
understand about these singular
microorganisms is they are brand
new in the scheme of things.
They're 20th century technology
of isolating organisms,
and an incredible range
of starters are available.
But they're new in the scheme of things.
The ancient form of a starter is what
I would describe as backslopping.
And that's basically,
you take the old batch
and you put some into the new batch.
This, is how people make yogurt.
The way you make yogurt is you
save a little bit of the old batch
and you put it into a
fresh batch of milk.
And there's some temperature
manipulation involved in there too,
but the source of the bacteria is
typically the last batch of yogurt.
This is what a sourdough is.
I mean, generally a sourdough is
started as a wild fermentation
because really all of those use and
bacteria are present on the wheat
or on any other grain.
But once you have a nice vigorous
sourdough with a good flavor
and a good lifting action for your
bread, you never bake the whole thing.
You always save a little
bit to perpetuate it,
to introduce into some
fresh flour and water.
And I've met people who have sourdoughs
that are hundreds of years old
that's been passed down in
their families for generations.
And you can do lots of things this way.
I mean, before pure yeast was
available a lot of breweries
made beer by saving a
little bit of the last batch
to introduce into the next batch.
This is the way a lot of
traditional salami making
has been done-- save a
little bit of the old batch
to introduce into the next batch.
So that's really the
ancient form of a starter.
And then the third form of a starter
are what we would describe generically
as scobies, S-C-O-B-Y, which is an
acronym which stands for Symbiotic
Communities Of Bacteria and Yeast.
And so there's really
just a handful of these.
The most famous example right
now would become kombucha.
The scoby is the mother of kombucha.
It looks like a rubbery pancake, and
it floats on top of the sweetened tea.
And that community of organisms
that are part of the rubbery pancake
grow into the sweet tea
and digest carbohydrates
and transform it into kombucha.
Another example of this would
be kefir, grains of kefir--
very different appearance from kombucha.
They look more like little
florets of cauliflower.
And embedded in those
florets of cauliflower
is an incredibly complex community with
more than 30 distinct organisms that
have been identified that somehow
coordinate their reproductions,
spin this skin that they share,
and ferment milk in the process.
There's a handful of other ones.
There's one called tibicos, also known
as water kefir, which comes from Mexico
and looks more like little
crystalline structures.
And you put them in any kind
of carbohydrate rich liquid,
and they'll ferment the carbohydrates
into acids and a little bit of alcohol.
And you can make delicious
beverages with them.
Now I mean, conceptually
all of these starters
had to start as a wild fermentation.
I mean, where did the
first yogurt come from?
I mean, it's a little bit of
a chicken or an egg problem.
But I mean, in my mind
it's very clear that it
was a happy accident in some
very warm place on a hot day,
and somebody sort of realized that the
temperature had something to do with it
and figured out a technique for,
through backslopping, reproducing
their results.
But the questions of origins are,
with anything, and certainly with any
of these foods is very, very
murky and highly speculative.
And there's a huge literature
that's addresses the question,
how did humans discover
or invent fermentation.
And I mean, my perspective is totally
that humans didn't invent or discover
fermentation, that we
evolved already knowing it.
There's a lot of great documentation
of different kinds of animals
gorging themselves on fermented
fruit, including primates.
And it just so happens that we evolved
with enzymes that can digest alcohol.
Interesting.
So I mean, humans didn't invent alcohol.
I mean, alcohol is a natural phenomenon.
If you ever pick a lot of berries,
you'll note some of them are fermented.
And it's a natural phenomenon that
our clever ancestors figured out
how to make happen, and we
developed a lot of technology.
I referred to pottery earlier, but
we developed lots of technology
to enable ourselves to sort
of your master techniques
for making these foods and beverages.
OK, let me just talk about
the cabbage a little bit.
And then we're going to leave some time
for questions, which hopefully there
are some.
So this is cabbage, some green cabbage,
some red cabbage, some carrots,
some onions-- sauerkraut does
not just have to be sauerkraut.
It doesn't have to just be cabbage.
Like literally you could
ferment any vegetable you want.
We cut the kernels off of
an ear of corn into here.
Know we could put ocra in here.
Any vegetable you want
you could put it here.
I lightly salted them.
OK, for the sauerkraut method,
the dry salting method,
you have to chop up the vegetables.
If you leave the vegetables whole, then
you need to mix up a brine solution
and ferment it in the brine solution.
But when you shred your
vegetables, then you
can have a more concentrated
flavor because you're not
diluting the flavor with water.
But remember, at the beginning
I said that our objective here
is to get the vegetables
submerged under liquid.
So we have to get some
juice out of the vegetables.
And so earlier when we shredded the
vegetables, we lightly salted them,
lightly salted them because
it's easier to add salt
than it is to subtract salt. So at some
point I'll taste it and I'll evaluate--
does it need more salt.
What I'm doing right now is
I'm squeezing the vegetables.
I'm massaging the vegetables.
And really what I'm doing
is I'm breaking down
cell walls to release juice.
In larger scale production,
families or villages
that would get together
in northern Europe
and make big barrels of sauerkraut,
they weren't usually doing it like this.
They had some kind of a
big, blunt, heavy tool,
and they were smashing
down on the vegetables.
Or a story I hear over and over again--
generally people my age or older
who grew up in Eastern Europe
is memories of having
their feet scrubbed
and being put inside the
barrel so that they'd
have their kids jump up and down.
Whether you're going to jump up and
down or smash it with the heavy tool
or, on a small scale, do this and
just squeeze it with your hands,
you're doing the same thing.
You're breaking down
cell walls-- oh, OK.
And you're releasing juice.
I'm going to keep
doing this for a couple
more minutes while I talk
about some of other issues.
OK, first of all, let's talk
about salt. A lot of people
imagine sauerkraut has
to be extremely salty.
Sauerkraut definitely does not
have to be extremely salty.
I'm going to add a little bit more
salt. But I mean, I'm just doing that.
That's just to taste.
If we had five different versions,
one at a half a percent salt,
1% salt 1 and 1/2% salt,
2% salt, 2 1/2% salt,
we wouldn't all agree about
which one tasted the best.
I mean, we would probably
have people thinking
each one of them tasted the best.
And if you follow a recipe
in the Joy Of Cooking which
by the way is where I first
learned how to make sauerkraut--
if you follow a recipe for lentil soup,
it will never tell you how much salt.
It'll say salt to taste.
And people imagine that
that fermentation somehow
requires more precision than that, that
you need a scale to weigh your salt.
I mean, if you're going to
have a commercial business
and you want to make
a consistent product,
then you need a scale to weigh your
salt so that it tastes consistent.
But if you're just making it for
your own personal pleasure at home,
there's no need to measure the salt.
The reason why many of us have the
idea that it needs to be very salty
is that this was a survival food.
If these were the last vegetables we
were going to see for the next six
months, we have an incentive to use
more salt. If on the other hand,
we're trying to make something that
we're going to enjoy eating, that's
going to support our
continued good health,
then there's just no reason
to make it extremely salty.
I mean, I get emails
every week from people
who say like, oh, I really
want to eat sauerkraut
but my doctor told me I can't
eat heavily salty foods.
It does not need to be heavily salty.
This is not rocket science.
It doesn't need to be a precise
proportion of salt. In fact, you
can make it with no salt at all.
I mean, it doesn't taste very good, and
it has or it has a really soft texture.
The salt does very helpful things.
So the first thing the
salt does is it starts
to pull juice out of the vegetables--
osmosis.
The second thing the salt does is, what
makes vegetables crispy are pectins,
and salt hardens the pectin.
So it makes the vegetables crispier.
The third thing is, if you
from vegetables for a long time
or in a warm environment
or certain vegetables--
mostly watery, summer vegetables
like cucumbers and zucchini,
they'll get very soft, very
quickly when you ferment them.
What makes the vegetables soft--
and it'll happen with sauerkraut
too if you do it for a long time
or in a warm environment.
What makes the vegetables
get soft are a class
of enzymes called pectinase enzymes
that break down the pectins,
and salt slows down
the pectinase enzymes.
It also slows down the
lactic acid bacteria.
And when your objective is
preservation, slowing down the process
is actually very helpful.
So salt does all these wonderful things.
But you don't need a lot of salt.
So, OK, I squeeze the vegetables until--
oh, you can't really
get it on the camera.
What if I go--
no.
Oh.
[LAUGH] OK.
Can you see that, when I'm squeezing
the vegetables, it's like a wet sponge
and all this juice is coming out.
That's when you know that it's juicy
enough to get the vegetables submerged.
You could measure the salt.
The generic proportion
that is repeated over and over again
in the literature is 2% salt by weight.
But you don't need to.
Just lightly salt it.
It's always easier to add salt
than it is to subtract salt.
As for a vessel, a
glass is perfect, a jar.
Wide mouth is a little bit easier
to deal with than something
with a narrower neck.
But you can do it in a mayonnaise
jar, and it would be totally fine.
You can use ceramic crocks.
You can use wooden barrels.
You can use plastic buckets.
The material you really
want to avoid is metal
because we're using salt as we cultivate
bacteria that are producing acids.
And both salt and acids
can corrode metal.
And while stainless steel
theoretically resists corrosion,
it turns out that household
grade stainless steel just
has a thin coating that's stainless.
And anywhere where it gets
scratched, it'll start to corrode.
Then the million dollar
question in fermentation
is how long do you ferment it.
And there's just there's
no straightforward
answer to that question.
The acids accumulate over time.
As a survival food, people
in a temperate environment
might make this in September, October,
November, depending on where they live
and keep eating it through the next
spring when there's fresh vegetables.
It doesn't mean you have to
wait for six months to eat it.
It means it's still
good after six months,
particularly if you have a nice
cool place where you can store it.
So you just fill the jar,
then fill it some more.
You don't want to fill
it to the very, very top
because it's going to produce carbon
dioxide and expand a little bit,
and we don't want it to all spill out.
You can see, as I press
down, the juice is rising up.
I chopped up too much.
It takes about two pounds of
vegetables to fill a quart
sized jar, a kilo for a liter.
So now the vegetables are
submerged under liquid.
There'll be more liquid tomorrow.
No matter how much liquid
there is, the vegetables
are going to want to float to the
top, like our bodies in the ocean.
So what I like to do is--
I mean, there's all kinds of
gadgets people are making.
Somebody just gave me
pickled pebbles that
are like these little glass disks that
go in the jar and hold everything down.
A ceramicist friend of
mine made me some little
ceramic disks to do the same thing.
But the good old-fashioned
improvisational method
is to take one of the outer leaves of
the cabbage that has a strong spine,
use that almost like a
spring, stuffing it in,
get the little spines stuck
under the shoulders of the jar,
and let it hold everything down.
And then if it peeks up, it
can be sort of sacrificial.
I say sacrificial because we're
protecting it from oxygen,
and there's a surface.
There's a place where
it's meeting the oxygen.
There are all kinds of
clever vessel designs
that are engineered to protect
the surface from oxygen.
But OK, how many people here
have ever fermented vegetables?
How many of you have ever had
any funky surface growth develop?
Oh, look, it's the same people.
So I mean the vulnerable
place is the surface.
That's where your protected
environment meets the oxygen.
And where the oxygen is all these
other forms of life can develop,
most prominently molds.
So the funky surface growth can be
a combination of yeasts and molds.
Almost always the molds are
white molds that will get darker
as they mature and sporulate.
I don't want anyone to go
home thinking they heard
me say it's OK to eat any kind of mold.
But because there are definitely molds
that are extremely, extremely toxic
and you definitely don't want to
touch any like bright colored mold,
but molds that start out white
and stay in a monochromatic range
are generally regarded as safe.
Everybody scrapes them off the top.
Remove any discolored or
softened vegetables near the top.
And what's underneath it is fine.
And this is sort of like repeated
throughout the literature.
And I mean, just the fact that
I've been doing this for 15 years
and never had anybody say
I followed your advice
and then my friend with extreme
mold sensitivity has had a reaction.
It just makes me feel
increasingly confident that they
were totally, totally harmless.
And just everybody who does
this has this experience,
and it's not a problem.
OK, I could go on and on
and maybe I will but--
PIA SORENSEN: But how about we--
thank you all of you for coming,
and thank you, Sandor.
