Los Angeles has brand new bars devoted¹ to an Italian style of raw fish, called crudo. President Obama kicked off his visit to Asia last month noshing（点心，小吃） nigiri（生鱼片寿司） at Jiro's famous sushi bar. And back in December, The New York Times named Sushi Nakawaza as its top restaurant of the year.

 

But why do so many of us find utter bliss²（极乐） in eating raw sea creatures but aren't so inclined to chow down（大快朵颐） on uncooked birds, cows or pigs?

 

A big part of it is gravity -- or the effective lack of it in the ocean, says biophysicist Ole Mouritsen, author of Sushi: Food for the Eye, the Body and the Soul.

 

"Fish are so soft. You can stick your finger through their muscles," he says. "Try doing that with a chicken or cow. Fish muscle is very different than that in land animals."

 

Why? Because fish can afford to be lazier than terrestrial animals. Fish essentially³ float all the time. So their muscles don't work constantly to fight gravity.

 

"Fish don't have to support their body weight," Mouritsen says, "so their muscle fibers⁴ are shorter and less tough than those in land animals." The same goes for the connective tissue holding the muscle fibers together: It's delicate and weak.

 

The result? Fish has a silky, smooth texture⁵ when it's raw, and a flaky（薄片的）, light texture when it's cooked.

 

By contrast, "Land animals -- like ourselves -- are always working to keep themselves upright and keep their shape," Mouritsen says, so our muscle fibers are thicker, tougher and firmer.

 

The result is a ropy（绳状的，粘稠的）, chewy -- and less appetizing -- texture when the meat is raw. Cooking softens⁶ the connective tissue in meat and improves its texture (it also makes it juicy and flavorful).

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