...The enzymes in the shrimp denature when exposed to the higher heat. Enzymes denature at high heat. That's what kills you when you're fever is too high, your enzymes denature, which means they are deformed/ become the wrong shape. Since the activation sites on enzymes are very sensitive to shape, they wouldn't work anymore. The cold doesn't denature enzymes however. They don't work as quickly but they still retain their shape.