The liquid nitrogen would be perfect. And it's really fun to play with. You wouldn't get the excess moisture from putting them in the freezer. I'd say cryovac-ing them would help, but when you cryovac fruit it ends up pulling some of the juice and moisture out, then it would freeze weird. Makes for some good conceptual things, though. Like tuna tartar made of cryovac-ed watermelon instead of tuna.