Pour the tuna into a sieve and drain well. Pluck the tuna apart. Put mayonnaise, sour cream, capers (except for 2 teaspoons for garnishing) with liquid and tuna into a high mixing bowl and puree with a blender.
Season to taste with salt, pepper and lemon juice. Prepare pasta in boiling salted water according to package instructions. Meanwhile, clean and wash the rocket and drain in a sieve. Wash the mint, shake dry and pluck the leaves from the stalks.
Drain the pasta, rinse and drain. Mix the noodles, rocket and mint leaves. Divide into 4 plates. Pour sauce over them. Garnish with capers.