Mentaiko (明太子) is made from fresh pollack or cod roe and is used in Japanese dishes.
Most commonly it is served with a bowl of rice or used as a filling for Onigiri (お握り).
The taste of Mentaiko can be difficult to describe, but it is somewhat saulty, fishy and spicy.
The main ingredients of Mentaiko are cod roe, sault and chili. It might also contain sake, yuzu, kombu or any number of other ingredients.
Mentaiko is also used with pasta. Mentaiko pasta has become a very popular dish among the Japanese.