I don't think any food has changed more in my lifetime than this one right here. When
I was a kid, most of the sweet corn that you encountered wasn't actually sweet, and sweet
corn that isn't sweet is one of the most disappointing foods in the world. You'd get this sad little
half an ear on your school lunch tray, and it would taste like, well, nothing, basically
nothing. These days, even bad sweet corn is usually pretty good, or at least it's pretty
sweet. The texture might actually be not as good as it used to be, and those two developments
are directly related. We'll get to that, but let's start at the beginning. What even is
sweet corn?
Like all cereal grains, corn is grass seed — giant seeds from giant grass plants, first
domesticated in what is now southern Mexico about 10,000 years ago. Botanically, corn
is way closer to wheat, and oats, and rice, and such than it is to carrots or broccoli,
so why do we consider corn a vegetable? Well, we don't, right? We consider sweet corn a
vegetable, but sweet corn is like a tiny fraction of all of the corn that's grown in the world.
Here in the U.S., It's 1% of the total corn crop.
The rest of the crop is this: field corn. Most corn is field corn, and this corn we
consider a grain, a starch. This corn is tortillas, and grits, and polenta, and cornbread, and
Corn Flakes, and popcorn, and a million non-food products like ethanol fuels, and a million
semi-food products like high-fructose corn syrup. All those things are corn, and none
of them are vegetables, yet, sweet corn is. Why?
Well, in part it's genetics, but arguably the bigger difference is simply when you harvest
it. Sweet corn you pick when the plant is still green, long before the seeds are mature
and dried, and ready to drop and grow into new corn plants. It's like if you were to
harvest wheat when it's still green, and eat the seeds when they're soft and wet on the
inside — which you can do, by the way. Corn probably works better as a vegetable than
other grains, because the grains of corn are just so huge. You get lots of juicy inside,
relative to the fibrous outside. That is sweet corn.
Field corn is called field corn because you let the plants grow, live, die, and shrivel
up right there in the field, so that the seeds will dry out. This is also how we do most
other grains like this rye here. It lives, then it dies, and there's your "amber waves
of grain." These are also amber waves of grain, though I always think that field corn blowing
around looks less like the ocean, and more like a mosh pit. See, doesn't it look like
they're moshing? Do the kids today still mosh?
Now, dried grain is great stuff. It's preserved, so you can store it and eat it all year long.
You don't have to spend every single day of your life hunting and gathering. You have
time to do other things like invent civilization. But there comes a brief window in every grain
farmer's season when they can pull some of the seeds off and eat them fresh — raw,
even. That's way easier than eating dried grains. For all of their advantages, dried
grains are hard. You have to grind them up into flour, and then mix them with water,
and then boil them or bake them.
These you can just put in your mouth, and when I get good sweet corn, I don't even really
cook it. I just steam it for like a minute until it's warm enough to melt butter. Ancient
American farmers ate at least a bit of their corn fresh or green, like this. Many different
tribes developed green corn festivals to celebrate the summer harvest, and they gradually developed
corn varieties that taste better when eaten green. Specifically, they bred corn with a
tweaked gene that scientists now call su1, sugary-1. Golden Bantam — one of the most
common heirloom sweet corn varieties still grown today — that's an su1 variety.
"Native peoples isolated different sugary-1 mutants that all do the same thing, but different
mutants at least five times in the Western hemisphere."
That's Dr. Bill Tracy at the University of Wisconsin. He's one of the most prominent
sweet corn breeders in the world. Check out his chair in the background. A-maize-ing.
I'll see myself out now, but now is a good time to clarify that Dr. Tracy uses the term
"maize" rather than "corn" when he is referring to sweet corn genetics. Maize is a word of
indigenous origin. "Corn" is a very old Germanic word for any and all grains, or actually any
object that's little and hard. In America, English-speaking colonists first called this
"Indian corn," which gradually just got shortened to "corn." Anyway, that sugary-1 gene that
farmers first started isolating maybe 6,000 years ago, what's it do?
"I have to say something here that might confuse you and your viewers. The genes that I'm talking
about knock out function. So I will actually be talking about the sugary gene as doing
something, but what it's doing is preventing the normal action. So the dominant sugary
gene, the kind that all the field corn has, actually makes starch."
Right. So normal field corn photosynthesizes carbon dioxide and water into sugar, which
the plant then converts into huge chains of sugar called starch. Raw starches feel a little
gritty in the mouth and do not taste sweet to us, but they are much more useful to the
plant. The seed eats the starch to fuel its growth up into a new corn plant. This sugary-1
gene mutation hinders the plant's normal starch conversion process.
"You knock that gene out, and instead — with like the gene that's Golden Bantam has, this
'little su,' if you will — that increases the sugar level and increases this compound
called phytoglycogen, at the expense of starch."
And phytoglycogen is this kind of rare and special substance that makes sweet corn creamy.
It's a carb that retains a lot of water, and it feels nice and smooth in the mouth. Field
corn has mostly starch, sweet corn has starch and sugar, and phytoglycogen, and some proteins
and fats and such that all corn has. But don't kid yourself — even if we call it a vegetable,
we're talking about a carb here. You're mostly eating water, and fiber, and carbs.
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So for millennia, we've had this mutant corn that fails to convert all of its sugar into
starch — at least, not at first. Problem is, you have a very narrow window in which
to harvest sweet corn when it's still sweet, and then once you do harvest it, take it off
the plant, you got to move real quick, because enzymes in there start to convert the sugar
into starch crazy fast. How fast?
"The old story was that if you were going to pick sweet corn, the old fashioned type
of sweet corn, the way to make sure it was optimal is to get the water boiling on the
stove before you go out, go out to the patch, pick the corn, and then run back to the house,
and if you drop one ear, don't stop to pick it up, because it'll all lose its quality.
That's of course an exaggeration, but that's the legend, and a lot of it's true. Sweet
corn, as I said, the old fashioned sugary type of corn, when picked at a prime stage,10
to 15% sugar, in 24 hours at room temperature, it will lose at least half its sugar. So the
next day, it really won't be very good."
And that, kids, is the world that Old Man Ragusea was born into. Most sweet corn that
you'd find was simply too old to be sweet anymore. All of the sugar had converted into
starch. There were three ways that you could get sweet corn that was still sweet. Option
one was get it frozen. Corn was one of the first foods to be frozen successfully by Clarence
Birdseye about a hundred years ago. Freezing halts those enzymatic processes. Problem is,
he had to cut the kernels off the cob to increase their surface area, and freeze them really
fast. If you freeze stuff too slow, it goes mushy. I have a whole video about flash freezing
in the description.
Option two was grow your own sweet corn, which we did when I was growing up in rural Pennsylvania.
We grew Golden Bantam, and I had corn on the cob every night for dinner all the way through
August, and I did not appreciate it as much as I should have.
Option three was go to a farm stand like this one, buy some corn straight from the hand
that picked it that same day, and go home and cook it that night. But hold on, what
variety are they growing here? What's that called, peaches and cream? That is not an
heirloom. That's one of these newfangled corn varieties that is likely to be sweet, even
if it isn't super fresh. The new sweet corn has its origins in the 1950s at the University
of Illinois, where there was a botany professor named John Laughnan. It's a super blurry photo,
but that's him in the '50s, when all this started. Laughnan was not trying to revolutionize
sweet corn.
"He was doing a study on what's known as genetic linkage. He was a basic scientist, and he
was trying to understand how genes were linked on a chromosome, or why they were linked."
Another geneticist in Michigan sent Laughnan some corn to study that had this weird sh2
gene, shrunken-2 gene. It was this gene that made the kernels kind of small, and they would
shrivel up, which you would consider to be a bug and not a feature, but then Laughnan
tasted it.
"And he got a hit of sugar. So he thought, Ah, something's going on here. And he actually
then did the basic biochemistry and found indeed, instead of the 10 to 15% sugar that
the sugary-1 crop corn had, some of these had 35 to 40% sugar, but they had no phytoglycogen.
They don't make the phytoglycogen. They make lots of sugar."
Laughnan went on to hybridize the first commercial supersweet variety, Illini Xtra Sweet. It's
still in the seed catalogs today. It starts off extremely sweet, so it can stand to lose
some sugar post-harvest, and it loses that sugar at a slower rate. The problem was the
texture — super crunchy, but not creamy. Also, these new supersweet hybrids tended
to have trouble germinating in the field. The seed's main food source is the starch,
not sugar. That's why the plant is supposed to make starch. Humans come along and we screw
all that up. Also because the supersweets shrivel, they tend to crack when they dry,
and then water gets in and they rot in the field, and they just have trouble germinating.
As a result, supersweets didn't even start to get popular with farmers until about the
'80s, as supersweet breeders, like Dr. Tracy, were able to fix a lot of these problems.
I can't remember the last time I saw old fashioned sweet corn at a regular grocery store. Something
like Golden Bantam or Silver Queen, they're just not at the store anymore. There's no
reason for a grocer to sell heirloom varieties, because it's nearly impossible for them to
get it to you and into your kitchen, into your mouth, while it's still sweet. Funny
thing is, some of these newer varieties might actually be too sweet when fresh picked. You
have to let them simmer down for a few days. But what about the texture?
"We're now working on a new type of corn that has a different gene. It's called the shrunken2-i
gene, and it's the same supersweet gene, but it does something slightly different. It improves
the mouthfeel of the supersweet. You still get a sweet flavor, but mouthfeel, the supersweets
don't have that phytoglycogen, So they're not really creamy. They're kind of watery.
They're good, people like them, but these new ones that we're developing have a crunch
like a Honeycrisp apple, very different from what we normally expect in sweet corn. And
people tend to love it, and we're really excited about this. There are some of these coming
to the market now, and hopefully we'll see some more, very soon."
It's also worth pointing out that the new supersweet varieties actually have more protein
per calorie than the old heirloom sweet corn. So rejoice, this is all good, and there's
nothing unnatural about it. People like Dr. Tracy arrive at these varieties via crossbreeding,
the same way humans have done for thousands of years to domesticate crops. Now, a few
sweet corn varieties are also GMOs, but that is purely incidental. They're not GMO-ing
them to make them sweeter, they're genetically engineering them to make them herbicide resistant
or pest resistant, like you do with all the other GMOs. And whether or not GMOs are even
a thing to be feared is something that we should talk about another day.