Long before Pokemon, magical girls, and Los Angeles Dodgers pitcher Kenta Maeda, the Japanese
gave us one of the world’s most perfect foods.
Sushi is sublime.
Just fresh fish and seasoned rice in its simplest form, or rolled up with some veggies in a
seaweed wrapper.
But while the ingredients are straightforward, making perfect sushi isn’t.
Japanese sushi chefs can spend seven years learning the art.
While some of you were off getting your Ph.D., sushi chefs studied the blade.
Er, the chef’s knife.
Let’s get into the chemistry that creates the subtle interplay of flavors in your tuna nigiri.
But first, a little history.
Sushi started out as a way of preserving fish, as early as three or four centuries B.C.E.
Fish packed with rice would undergo a year-long process of fermentation.
Fermentation occurs when friendly bacteria munch on carbohydrates like the starches found
in rice and convert them to acid.
In this case, lactic acid.
The buildup of acid makes it more difficult for harmful bacteria like botulinum to grow.
That means they can’t get a foothold to contaminate or spoil the food.
Hey, people had to get creative in the days before refrigerators.
They didn’t even eat the rice in this earliest form of sushi.
They tossed it out, maybe because it was a year old and full of sour-tasting lactate.
But fast forward a few centuries and people started to acquire a taste for the stuff.
Modern sushi rice is seasoned with vinegar to give it that acidic sharpness.
By the bustling Edo period in the 19th century, sushi had become a popular street food.
Lightly cured fish was served over seasoned rice for on-the-go working folk looking for
a quick bite.
Now that we have refrigerators, the fish can be served completely raw, although some kinds
like eel and octopus are still served cooked.
Two of those years sushi chefs spend studying is spent just on rice.
The rice is seasoned with vinegar and sugar.
Some chefs also add a type of seaweed called kombu--more on that in a second.
The rice itself has to be perfect.
When cooked, it should just hold together without being a sticky, mushy mess.
A grain of sushi rice contains granules of sticky starch like amylopectin.
When cooking, chefs try not to break open the individual grains.
Doing so would release the starch, which would cause the grains to stick together too much.
Plus, it’s considered aesthetically important for the grains to maintain their shape.
Then there’s the seaweed.
The wrappers that hold sushi rolls together are a kind of seaweed called nori, whereas
the kombu sometimes used to season the rice is a variety of kelp.
Seaweeds have a huge variety of flavor compounds like mannitol that give it sweetness and iodine
and bromophenols that contribute a certain seabreeze-y tang.
But there’s one other important ingredient.
Early in the 20th century, chemist and professor Kikunae Ikeda was sitting down to a hot supper.
He asked his wife just what was in the soup that made it so delicious and started studying
the kelp she used to add flavor.
After years of research, he discovered what his wife and Japanese cooks like her already
knew: Kombu gives foods a savory deliciousness captured by the Japanese word umami.
This was the Fabled “fifth taste” after salty, sweet, sour and bitter.
And he was able to isolate the compound responsible for umami-ness: glutamate.
Glutamate in the form of glutamic acid, is an amino acid, one of the twenty common building blocks of protein.
But our tongues also have a taste receptor for it, so we perceive it as meaty, cheesy
GLORIOUSNESS.
Adding a sodium ion, like the kind in table salt, turns glutamate into MSG.
WAIT, don’t close the tab!
MSG has gotten plenty of bad press on food labels and health websites. It’s been
blamed for all kinds allergies and headaches.
But scientific evidence for those claims just hasn’t emerged.
Anyway, what about the star of the sushi show? You know, the fish?
Yeah, of course, there’s plenty going on there too.
Fish itself also contains glutamate, for more umami goodness.
But the flavor of fish is thanks in large part to the fats it contains, which vary based
on the fish’s diet and habitat.
Those fats include brain-healthy omega-3 fatty acids, which are also in seaweed--making sushi
a very smart snack.
Well, at least if you’re not getting one of those big mayo-y fried things.
Omega-3, by the way, refers to the chemical structure of the long chains of carbon and
hydrogen in fatty acid molecules.
Omega refers to the end of the tail, and the 3 means a double bond first appears three
carbons inward from the end.
Our bodies can’t just throw double bonds into fatty acid molecules willie-nillie wherever they want.
Which means, to get those molecules in our bodies, we have to consume them in our diet.
Thanks for looking after our brain and heart health, sushi!
Fish also come in colors from the deep red of tuna to the whitish hue of flounder.
And that depends on the fishy’s lifestyle.
Tuna are strong swimmers, and their muscles need tons of oxygen.
That’s delivered by a protein called myoglobin that turns those muscles red.
Lazier fish like this flounder -- the couch potato of the ocean floor -- still sometimes
need to make a quick dash to escape predators.
That kind of quick movement doesn’t depend on oxygen, so there’s less myoglobin in
their muscles and they tend to be lighter in color.
There’s one weird exception.
Salmon are also lazy.
Well, apart from that time when they swim upstream and all.
But they eat crustaceans, whose shells contain a pigment called astaxanthin that turns their muscles pink.
Without it in their diet, farmed salmon would be gray.
So aquaculturists add the pigment to salmon feed rather than offer up gray fish to squeamish shoppers.
That’s it for the main ingredients in sushi, which come together to form a harmonious sweet-sour-umami
treat.
Next time your friends say they don’t eat raw fish, you can wow them with the chemistry
that makes sushi objectively amazing, or you can just say “Cool, more for me.”
We’d like to thank chef Kaz Okochi of Kaz Sushi Bistro in Washington, DC, home of the
beautiful eats you see in this video.
We didn’t have time to go into all the sides and fixin’s.
Like, did you know the little lump of green stuff in your plastic sushi tray isn’t real
wasabi?
Lies!
Scandalous lies!
Sound off in the comments on your favorite kind of sushi, and thanks for watching!