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UCLA Science & Food Lecture Recap: Umami and Sushi

[Photos: Matthew Kang/Eater]

Last night, UCLA's Science and Food began its third year of public lectures, starting with Ole Mouritsen, professor of molecular biophysics at the University of Southern Denmark, and LA sushi chef Morihiro Onodera. Mouritsen, who's written several books ranging from Sushi: Food for the Eye, the Body, and the Soul to the nearly released Umami: Unlocking the Secrets of the Fifth Taste, spoke at length about the unique properties of foods that contain umami while Morihiro discussed the effects of rice quality on the overall flavor of sushi.

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Amy Rowat, professor of life science and the organizer of the annual Science and Food lecture series, introduced the night's guests.

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Ole Mouritsen began by explaining that the science of sushi is actually about the rice. Sushi began as a way of preserving fish hundreds of years ago because the rice would aid in the fermentation of fish, enabling it to last for months.

Because of modern technology such as refrigeration, this style of sushi isn't necessary anymore, but originally the rice was essential for nurturing good bacteria. While this changed the texture and odor of the fish, it remained nutritious and edible. This way of preserving fish isn't unique to Japan, as Nordic countries have things like rakefisk, gravlax, surströmming, the last of which is like fermented herring in a can.

Mouritsen then transitioned over to taste at the molecular level. When we eat sushi and other kinds of food, everything is essentially broken down to carbohydrates, proteins, fats, and nucleic acids. Molecules interact with the osmotic pressure on our palate, with certain molecules resulting in more flavor. One reason saltwater fish tends to be more flavorful than its freshwater cousins is because of the balance of osmotic pressure their molecules lend to the palate.

Next, Mouritsen set down the foundation for Onodera's part of the presentation by delving into the science of rice. Home cooks might soon realize that cutting fish isn't as difficult as making the perfect sushi rice. The milled part of rice that's common in sushi is about 60 to 70 percent starch. When cooked, the grains swell, but they are not broken because the layers of proteins keep them together.

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Morihiro Onodera and translator.

Morihiro Onodera, former chef and owner of Mori Sushi in Los Angeles, started with the balance between neta and shari. Neta is the fish aspect, which can't be too heavy or big compared to the rice, or shari. The balance has to be delicate and perfect.

One little insider tip that Onodera shared (but didn't necessarily promote for all sushi fans): He orders one tekkamaki, or simple tuna roll, to determine the quality of the establishment. This roll shows everything from the knife skills, fish preparation, and overall technique. And of course, this roll shows off whether the rice is cooked properly and perfectly. Think of it as a litmus test for sushi restaurants.

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As an experiment, Onodera examined two kinds of rice and found that higher quality grains result in one crack in 100 grains while the lower quality showed between seven and eight significantly cracked grains. Cracked grains lead to starchy rice that's too sticky. Onodera then spoke about his involvement with a rice farm in Uruguay that uses age-old techniques. He also demonstrated his method for washing rice on stage.

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Mouritsen took the microphone again to review some of the scientific aspects behind sushi.
before things rolled over to nori, which both Onodera and Mouritsen discussed at length for its unique properties in sushi. For example, nori has its own polysaccharine, a soluble dietary fiber that acts as a glue to keep it together like paper. That's why seaweed extracts produce gelatin agents like agar agar.

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Finally, Mouritsen had the audience taste different kinds of dashi, made with kombu, a Japanese seaweed; katsuobushi, or preserved bonito; and dulse seaweed, which in this case was harvested in nearby Monterey, California, but also grows in the Atlantic. The Danish professor then discussed how Kikunae Ikeda discovered the secret behind flavorful Japanese broths: Umami.

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An interesting revelation was the discovery of glutamic acid and its reaction to nucleotides: It isn't just glutamate-rich foods like tomatoes, parmesan, and soy sauce that create deliciousness, but their synergy with foods rich in corresponding nucleotides like katsuobushi, shiitake mushrooms, and more.

Mouritsen finished by saying that while there is some science involved, in the end, flavor and aesthetics come first when it comes to sushi.

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