A cooking oven (100) is proposed. The cooking oven (100) comprises a cooking portion (100 COOK ) adapted to cook food stored therein, a components portion (100 COMP ) for housing components that allow and control an operation of the cooking oven (100), a steam generation system for generating steam and for supplying the generated steam to the cooking portion, the steam generation system comprising a boiler (110; 110') with a vessel (115; 115') adapted to contain water to be converted into steam, and a descaling apparatus (200; 300; 400) adapted to remove scales/limestone from the steam generation system. In the solution according to an embodiment of the invention, the descaling apparatus (200; 300; 400) comprises a support body (240; 410) in fluid communication with the vessel (115; 115'). The support body (240; 410) is adapted to be provided with a descaling agent container (205). The descaling agent container (205) is adapted to store a descaling agent (210) and has an opening sealed by a sealing element (235). The support body (240; 410) is shaped so that once the descaling agent container (205) is coupled with the support body (240; 410), the sealing element (235) sealing the opening of the descaling agent container results exposed to the steam generated in the vessel (115; 115').