Elfie's Changed Preference

I bought a small packet of ikan bilis for my hamster Elfie, only to realize that he has changed his taste for food. He doesn’t like ikan bilis anymore! He literally turns his head & whole body away when I offer him an ikan bilis! Shocking! And when I offered him a black seed & he threw himself at it, as if he had not eaten one in ages! I think he just wants to eat those black seeds. Hmm…