A method and an apparatus in form of a disinfecting apparatus comprising a steam device for combating germs on the surface of products, in particular of food products. The apparatus employs a combination of steam and ultrasound to kill germs on the surface of a product which is conveyed past the steam device. Pressurized steam is fed through a steam passage to an opening conveying the steam to a cavity, in which the steam is made to oscillate at a ultrasonic frequency. The oscillations in the steam prevent the steam from heating the products excessively, while germs presents on the surface of the products are heated and killed.