The kind of katsuobushi sprayed with fungus, which is called "karebushi," includes more flavor ingredients and vitamins than other kinds, so it's traded as a luxury.
また、カビを生やした枯節（かれぶし）と呼ばれる種類の鰹節は、うま味成分やビタミン類が他の鰹節より多く含まれ、高級品として扱われている。