The shrimp's muscle structure is similar to that of lobster, resulting in a more substantial chew than flaky fish. Due to their small size, the proteins bind tightly together in a matter of minutes. Look for a slight “C” curled shape and opaque appearance. Some varieties will turn pink due to the natural pigment called astaxanthin being released at 120ºF (49ºC). They're ready at 140ºF (60ºC).