I bought two nice Ahi Tuna steaks, put them in the freezer for three days, then marinated them in sesame oil, a little lime juice, green onions, garlic and soy sauce. My husband grilled it perfectly to obtain the white edge and rare in the middle but warmed through nicely. Usually, I can cut it with a fork, but last night noticed right away, it was stringy. Tried it again today for lunch by just warming for 20 seconds in the microwave. i ended up tossing it out. I still have the second steak which we have not cooked, sitting in the fridge. What can I do with this expensive stringy piece of fish? I am also wondering why it was so stringy. Some bites, I could not swallow because I just had a stringy lump in my mouth even after chewing.