Seaweed, sushi and science

Sushi!
iStockphoto/ShyMan

I prefer my seaweed applewood smoked. However, truthfully, before yesterday, I’m not sure I could have told you whether I liked seaweed, smoked or otherwise.

I do like sushi, but the seaweed within a maki roll has always seemed more functional than flavorful– a necessary material to keep the whole thing held together.

But when I heard about yesterday’s Experimental Cuisine Collective meeting– “The Science of Sushi and Seaweed”– I couldn’t resist. The speaker’s day job is as a biophysicist at a Danish university, and he haunts sushi restaurants (and even writes a book) in his spare time. Perfect.

And so I spent yesterday afternoon at a sushi science talk and algae tasting. Seaweeds are algae after all, not plants. So though many algae synthesize food from the sun, unlike plants, seaweeds are complexes of single cells. Plants are interdependent multicellular organisms– seaweed are communities of independent operators.

Ole Mouritsen talked in a lovely cultural and scientific hodgepodge– part cultural history and part science. The flavors of sushi– the sweetness of the rice, the sour from the vinegar– date back to old methods for preserving fish. Though no longer necessary, those lingering elements of taste are part of the sushi experience. A tidbit about wasabi– though it may be fiery– its punch comes from isothiocyanates (funky molecular structures that have carbon, nitrogen and sulfur lined up next to each other). But unlike other molecules that set our taste buds on fire (capsaicin in chili peppers, for example), isothiocyanates are water soluble. That’s why you can actually cleanse your palate pretty easily if you get a little too much of the evil green stuff.

But back to the seaweed. I’m definitely not ready to become an algaetarian, but seaweed definitely makes an interesting, sometimes pungent garnish. Nori– the ubiquitous sushi wrapping– is actually paper-like, easily torn. But when wrapped around sushi rice, it quickly absorbs water and the complex sugars become gummy. The Japanese annually fete Kathleen Mary Drew-Baker, the British botanist who figured out how to culture this particular algae.

Oboro kombu looks a little like vacuum cleaner lint and melts in your mouth like umami cotton candy. And then there’s the dulse– dark red, tangy, particularly the almost bacony applewood-smoked version. Don’t forget to sniff first.

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Practical phase changes: more carbon dioxide

I get to talk about an interesting application of carbon dioxide today in my latest article for Scientific American: sterilizing transplanted tissues such as tendon and bone. Before I heard about this technology, I certainly wouldn’t have suspected that the ubiquitous gas that we exhale could become a super-scrubber with a little heat and a lot of pressure.

I’ve ended up playing with a lot of carbon dioxide over the years. Like most kids, I had ghoulish carbon dioxide bubbles from dry ice that fizzed my Halloween drinks. As a chemist, dry ice became almost too “normal.” As an undergrad, I made my own bricks of the stuff from a tank of compressed CO2, and in graduate school, I’d weigh it out by the tens, if not hundreds, of pounds. Mostly, I used it to cool things down.

But though it’s easy as a working organic chemist to think  it cliché, watching the supercritical fluid form and dissipate is amazing. That sense of wonder within a high pressure chamber– and the practical applications that come from it– keep me coming back to work everyday.

Speaking of clichés, this professor probably fits the stereotypical scientist image a little too well. But I love his giddy enthusiasm when he talks about how he uses the demonstration to see whether a prospective student might be a good fit for his research group.

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