A steam injection heater (10) and related methods for injecting steam into a sterile fluid delivery system used to transport a flowing sterile fluid food product. The device (10) includes a tubular member (12) having an inlet (34) for receiving a flow of the fluid food product, an outlet (69) for discharging the flow, and a longitudinal passsageway (20) therebetween. A chamber (14) is disposed radially outward of the passageway (22). The chamber (14) receives steam that is exhausted through an annular opening (52). A flow diverter or valve member (68) is disposed within the longitudinal passageway (20) and fluid food product must flow about the valve member (68). The diverted flow of fluid food product is intersected by the annular flow of injected steam.