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10 Things About Sushi

At our 2014 Science of Sushi event, Dr. Ole Mouritsen and Chef Morihiro Onodera illuminated the science underlying some of our favorite components of sushi. In case you still haven’t had your fill, here are 10 scientific facts related to sushi: Read more

The Science of Sushi

The Science of Sushi
Featuring Dr. Ole Mouritsen and Morihiro Onodera
April 23, 2014

To kick off our 2014 public lecture series, Dr. Ole Mouritsen joined Chef Morihiro Onodera to satisfy our craving for sushi-related science. The duo explained everything from sushi’s early history to the starchy science of sushi rice. Watch the entire lecture or check out some of the shorter highlights below.

Ole Mouritsen on the history of sushi

“The history of sushi is really the history of preservation of food. . . . Throughout Asia, in particular in China and later in Japan, people discovered that you can ferment fish – that is, you can preserve fish – by taking fresh fish and putting it in layers of cooked rice. . . . After some time the fish changes texture, it changes taste, it changes odor, but it’s still edible and it’s nutritious. And maybe after half a year you could then pull out the fish and eat the fish. That is the original sushi.”

Ole Mouritsen on the science of rice

“If you look inside the rice, you have little [starch] granules that are only three to eight microns, or three t0 eight thousandths of a millimeter, big. . . . When you cook the rice, you add some water and the water is absorbed by the rice and [the granules] swell. And the real secret behind the sushi rice is that when they swell, these little grains are not supposed to break.”

Morihiro Onodera on examining the quality of sushi rice

“First what I do is I soak uncooked rice in water. . . . Sometime after 20 minutes it will start to break. . . . I take a sample to check to see if there are any cracks. . . . With good rice, which has less cracks or breaks, you’re able to feel the texture of each of the grains in your mouth, whereas with the lower quality rice you’re just going to get the stickiness [from the starch].”

Follow-Up Q&A with Ole G. Mouritsen

Onodera, translator, and Mouritsen at Science of Sushi. Photo Credits: (Matthew Kang/Eater)

Onodera, translator, and Mouritsen at Science of Sushi. Photo Credit: Matthew Kang/Eater

The audience present at The Science of Sushi asked our guest lecturers some great questions, and quite a few of them! Unfortunately, there wasn’t enough time to answer them all, but Ole G. Mouritsen has been kind enough to answer some of the lingering questions that went unanswered. Below his responses, we have included some additional information to help quench your thirst for knowledge (and sake).

Q: Are parasites within fish common? Are they a passable health problem?

A: Parasites can be common in some species, e.g., cod, mackerel, herring, and wild salmon. If in doubt, always freeze or marinate fish before eating raw.

The FDA provides guidance under their Parasite Destruction Guarantee on the preparation of raw fish. Fish intended to be consumed raw must be “frozen and stored at a temperature of -20°C (-4°F) or below for a minimum of 168 hours (7 days)”. [1]

Photo Credits: (Antony Theobald/Flickr)

Photo Credit: Antony Theobald/Flickr

Q: What exactly is ‘sashimi/sushi grade’ fish?

A: Fish that can be eaten raw. If in doubt, ask a fishmonger you trust.

 In the United States, the term ‘sushi grade’ is unregulated. However, many suppliers have set up their own parameters for their products, often reserving the term for their most fresh fish.[2]

Photo Credits: (Marla Showfer/Flickr)

Photo Credit: Marla Showfer/Flickr

Q: What are your thoughts on using brown rice in sushi?

A: I don’t myself like brown rice in sushi. If you worry about the calories in white rice, don’t eat sushi.

During the milling process, the germ and bran layer of brown rice are left intact, and are not removed as they are in white rice. The only layer removed is the outermost layer, the hull. Some health-conscious people often opt for brown rice because several vitamins and dietary minerals are lost in this removal process and the subsequent polishing.

Photo Credits: (Thokrates/flickr)

Photo Credit: Thokrates/flickr

Q: What’s your thought on cooking rice with ‘bamboo charcoal’?

A: I don’t understand this question. In principle the source of heating does not matter (except if the cooking pot is open and takes taste from the burning material).

Q: Sake: does it add, hide, or subtract?

A: It is a matter of taste. An old Japanese proverb says that one should not drink sake with rice (too much of a good thing). So drink sake before the sushi meal, or after.

Sake, the alcoholic rice beverage officially known as “Seishu” is defined as one of the following:

  1. Fermented from rice, rice-koji (the mold used to convert the starch in rice into fermentable sugars), and water.
  2. Fermented from rice, water, Sake-Kasu (the lees that remain after pressing Sake; these can still contain fermentable elements), rice-koji, and anything else accepted by law.
  3. Sake to which Kasu has been added.

After any of these processes, the liquid is then strained through a mesh to produce a clear beverage. [3] 

Photo Credits: (atmtx/flickr)

Photo Credit: atmtx/flickr

 

References

  1. “FDA Food Code 2009 – Chapter 3 – Food.” Fda.gov. N.p., n.d. Web. 28 Apr. 2014.
  2. Ransom, Warren. “Sushi Grade Fish.” The Sushi FAQ. N.p., n.d. Web. 28 Apr. 2014. <http://www.sushifaq.com/sushi-sashimi-info/sushi-grade-fish/>.
  3. “Sake.com: Sake Making.” Sake.com: Sake Making. N.p., n.d. Web. 28 Apr. 2014.

Elsbeth SitesAbout the author: Elsbeth Sites is pursuing her B.S. in Biology at UCLA. Her addiction to the Food Network has developed into a love of learning about the science behind food.

Read more by Elsbeth Sites


Texture and Color of Sashimi

photo credits (sake puppets/flickr)

Whether or not you like eating sashimi, such a fine specimen of fish is undeniably an incredibly beautiful food. The subtle flavors, delicate texture and vivid colors make sushi and sashimi such a unique eating experience. To whet your appetite for The Science of Sushi at UCLA, here are some bits of sashimi science we learned from Ole G. Mouritsen’s book, Sushi: Food for the Eye, the Body, and the Soul.

Sashim刺身

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Salmon and Tuna Sashimi – Photo Credits: (avlxyz/flickr)

Why are fish muscles soft?

If you used your finger to poke a raw filet of a bony fish like salmon or tuna, then tried this on meat from a terrestrial animal like beef or pork, you would notice that fish muscle is significantly softer than terrestrial meat. On a very fresh piece of fish, you could poke your finger through the muscle. From a basic understanding of meat texture, it seems strange that the meat of a fast-swimming predator is soft while the flesh of a slow-moving grazer is firm; typically the more an animal uses its muscles, the tougher its muscles.

Yet fish tend to have the same density as the water in which they live, so they do not use their muscles to bear their own weight; fish need only to exert their muscles when they want to move. By contrast, terrestrial animals frequently use their muscles to counter gravity and remain upright. Fish simply have less work to do, and so their muscles do not develop the same chewy texture that land animals do. But not all fish have smooth and tender muscles; some species like shark have tougher meat. Why? Sharks’ bodies happen to have a specific gravity greater than the water they inhabit, so they must exert their muscles at all times to keep afloat, and thus their muscles more closely resemble a ruminant’s in firmness.

Fresh is best

About six hours after the fish is killed a phenomenon common to all animals, rigor mortis, sets in. During rigor mortis calcium ions of the proteins embedded in the muscle fibers are released, causing the muscle fibers to contract and become stiff.

To delay rigor mortis for up to a few days, fish can be deep-frozen immediately after they are caught. Once the process of rigor mortis has run its course, the fish begins to decompose, the muscle fibers separate, and the connective tissue loosens. At this point it is ideal to consume the fish, as it is at its peak of softness and freshness. This type of sushi is called nojime, the type made from fish that are not kept alive after being caught. The opposite is ikijime sushi, prepared from fish with firmer muscles as they are kept alive until the last moment and prepared before rigor mortis can set in.

A rainbow of fish

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Orange, pink, red, white; there is remarkable variation in fish meat color. Photo Credit: Kake Pugh (kake/flickr)

Orange and pink

The muscles of wild salmon and sea trout are typically orange-pink in color. The origins of this distinct shade of salmon begins at the bottom of food chain, with plankton. These little organisms contain a pigment astaxanthin. It belongs to the family of pigments called carotenoids, which includes the pigment that makes carrots orange. Tiny crustaceans eat plankton, and thus ingest astaxanthin, whereupon it is bound to proteins called crustacyanins in the animals’ tough shell. While bound to these proteins, the pigment is blue-green or a dark red-brown. This will seem familiar if you have ever seen live crab or lobster. When a fish comes along and eats the crustacean, the crustacyanins are denatured and they release the pigment, allowing its own red-orange color to become visible. The color change that occurs upon cooking crustacean shells is caused by the same protein-denaturation and pigment-release process that occurs in fishes’ digestion systems.

Red Fish

Although the proteins that form the muscles themselves are colorless, a lot of fish meat is deep red, like tuna. These colored muscles are classified as slow muscles, as they take care of work that has to be carried out on an on-going basis, namely, continuous swimming. Since they require a continuous oxygen supply to produce energy, they contain myoglobin. Myoglobin is responsible for the transport of oxygen within muscle tissues. Each myoglobin molecule can bind one oxygen molecule to form oxy-myoglobin, which is bright red.

White fish

In contrast to slow muscles, fast muscles undertake smaller and more rapid movements like the slapping of fins and tail. These muscles do not contain myoglobin; instead they use the colorless starch glycogen to supply energy. No myoglobin means that these muscles stay colorless or white.

Interested in learning more sushi science from the experts? UCLA Science & Food’s public lecture, The Science of Sushi, is on April 23rd. In this lecture, Dr. Ole Mouritsen will illuminate the science underlying sashimi, nori, sushi rice, umami, and more.  He will be joined by Chef Morihiro Onodera who will share his approach to sushi as well as an inside look into his partnership with a rice farm in Uruguay.

References:

  1. Mouritsen, Ole G. Sushi: Food for the Eye, the Body & the Soul. New York: Springer, 2009. Print.

 


Elsbeth SitesAbout the author: Elsbeth Sites is pursuing her B.S. in Biology at UCLA. Her addiction to the Food Network has developed into a love of learning about the science behind food.

Read more by Elsbeth Sites


Science of Sushi & Sushi in Space

spacesushi

Dr. Ole G. Mouritsen discusses his book Sushi: Food for the Eye, the Body, and the Soul, and astronaut Soichi Noguchi prepares sushi aboard the ISS. Read more

Morihiro Onodera

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Chef Morihiro Onodera trained as a sushi chef in Tokyo, and at seminal Los Angeles restaurants including Katsu, R-23, Matsuhisa, and Takao as well as Hatsuhana in NY. By the time he opened his first restaurant, Mori Sushi in Los Angeles, he was preparing many of the same handmade ingredients, harvesting his own locally grown rice and creating handmade pottery to be used in the restaurant. After selling Mori Sushi in 2011, Mori began creating handmade pottery for several Michelin Guide restaurants in Los Angeles and established a partnership with rice farmer, Ichiro Tamaki. Tamaki farms in Uruguay will harvest its first crop in May of 2013 and will be available for distribution world-wide.

See Morihiro Onodera April 23, 2014 at “The Science of Sushi”

What hooked you on cooking?
The desire to want to eat and taste delicious food.
The coolest example of science in your food?
My basic approach to cooking is to think about the natural ingredients and the climate (seasons) of its origin, ingredients that are kind to the body and to earth—a very simple-minded attempt with natural science at its core.
The food you find most fascinating?
I’m always seeking the true flavor of a given ingredient—that’s what fascinates me.
What scientific concept–food related or otherwise–do you find most fascinating?
Natural science.
Your best example of a food that is better because of science?
Konbu and natural salt.
How do you think science will impact your world of food in the next 5 years?
It will be interesting to see how the true flavors of ingredients change over time—how natural science will affect that change. Simultaneously, I will continue my studies in discovering and knowing what’s kind for the human body and our earth.
One kitchen tool you could not live without?
Rice cooker, including donabe (Japanese clay pot).
Five things most likely to be found in your fridge?
Fresh local vegetables, miso, umeboshi (pickled plum), homemade yuzu kosho (pepper), and leftover cooked brown rice. Outside of the fridge: dry goods, salted bran (used for pickling), rice, oil (sesame and olive), salt, konbu.
Your all-time favorite ingredient?
Rice.
Favorite cookbook?
Book series by Rosanjin (Kitaoji Rosanjin, Japanese artist and epicure).
Your standard breakfast?
Black tea (straight). Seasonal, local fruits. Bread or hot rice cereal. Sometimes eggs (steamed) cooked with sautéed spinach.

Ole G. Mouritsen

ole-mouritsen

Ole G. Mouritsen is a professor of molecular biophysics at the University of Southern Denmark. His research concentrates on basic science and its practical applications to biotechnology, biomedicine, gastrophysics, and gastronomy. He is an elected member of the Royal Danish Academy of Sciences and Letters, The Danish Academy of Technical Sciences, and the Danish Gastronomical Academy. His books include Life: As a Matter of FatSushi: Food for the Eye, the Body, and the SoulSeaweeds: Edible, Available, and Sustainable and Umami. Unlocking the Secrets of the Fifth Taste.

 

See Ole G. Mouritsen April 23, 2014 at “The Science of Sushi”

What hooked you on science? On food?
Science: Curiosity, in particular in the history of natural sciences (thermodynamics, statistical physics). Food: A combination of a continuously growing interest in cooking, a liking to eat good and challenging food (in particular Japanese food), a challenge to apply science principles to food and cooking, as well a deep interest in using food and taste as a vehicle for science communication.
The coolest example of science in your food?
Access to foodstuff from the ocean as a prime source for unsaturated essential fatty acids together with the invention of cooking for producing soft food as key driving forces for human evolution. Next to that, dairy products have a wonderful science content.
The food you find most fascinating?
Almost all traditional Japanese food, because of the combination of its cultural history, deliciousness, aesthetic looks, freshness, and bounty of good stuff from the ocean.
What scientific concept–food related or otherwise–do you find most fascinating?
Self-assembly and interface-active compounds.
Are there any analogies you like to use to explain difficult or counter-intuitive  food science concepts?
I have found that a pacman analogy is a great way of making people understand the secrets of the synergy in the umami taste sensation. Not really counter-intuitive, but somewhat surprising and good to understand better what you already know.
How does your scientific knowledge or training impact the way you cook? Do you conduct science experiments in the kitchen?
I am an intuitive cook in my own kitchen and I have no patience for recipes, and hence never use cookbooks. Sometimes I ask science questions, but in most cases cooking to me is more like performing music (not that I know since I am not a musician). Also, the kitchen for me is a place for mental repair and relaxation, the foreplay being shopping at food markets.
One kitchen tool you could not live without?
My Japanese all-purpose kitchen knife.
Five things most likely to be found in your fridge?
Skyr (or yoghurt), a selection of tsukemono, marinated herring, miso, yuzu juice, and dried/smoked/aged sausages.
Your all-time favorite ingredient?
Avocado.
Favorite cookbook?
I have no favorite cookbook (don’t care much for cookbooks). My favorite food-related book is no doubt McGee’s On Food and Cooking.
Your standard breakfast?
At home, always skyr (or yoghurt), home-mixed basis muesli with no dried fruit but always with roasted buckwheat, topped with a sip of fresh orange juice and possibly some fresh blueberries, if in season. To drink, fresh orange juice with as much pulp I can get and black tea. When traveling, I am an omnivore and prefer to eat like the locals.