Abstract: A method for introducing a vaporous heat carrier into a liquid product, in particular a food product or beverage, and more particularly viscous products, for example desserts, sauces or concentrates, includes using the carrier to heat the product to form a germ-free product. An injector for carrying out the method is also described. A reduction in the heat transfer capacity of the injector is prevented over the entire production time. This is achieved in that three physical measurement variables which can be detected during operation of the injector are used as indicators of the formation of product deposits. At least one of said three physical measurement variables is detected, and depending on these variables, an automatically controlled axial movement of the displacement body is carried out such that the heat transfer capacity from the vaporous heat carrier into the liquid product remains the same.