A heating medium injector includes an injector structure defining a heating medium flow path and a product flow path. The heating medium flow path extends to a contact location, while the product flow path also extends to the contact location. The contact location comprises a location at which the heating medium flow path and product flow path merge within the injector. A mixture flow path is defined within the injector structure between the contact location and an injector outlet of the injector structure and is defined at least in part by a mixture flow path outer surface comprising a mixture flow path wall. A cooling structure extends along both a product flow path boundary wall and the mixture flow path wall so as to traverse a plane extending transverse to the foodstuff flow path at the contact location.