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.
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