The present invention relates to a method including heat treatment of a composition including chitin and water-soluble vitamins and/or derivatives thereof. The invention also relates to a granule which can be obtained by the method according to the invention, a granule comprising chitin and water-soluble vitamins and/or derivatives thereof, and the use of said granules in human food or animal feed, more particularly in fish feed. Finally, the invention relates to the use of chitin to protect water-soluble vitamins during heat treatment.