Twin screw extruder for batch freezing

An apparatus (10) for at least partially freezing a food product which is at least partly liquid in a batch mode is disclosed including a double screw extruder (12) including first and second, substantially intermeshing, self-wiping screws (14, 16) rotatably received in a figure 8-shaped barrel (30) with minimal clearance. In the preferred form, the freezing block (20) includes multiple refrigerant channels (36) spaced closely and in the most preferred form spaced approximately 0.32 centimeters from the barrel (30) and from each other. Thus, the refrigeration system can change the barrel surface temperature rapidly and specifically in approximately one second when the food product is introduced into the barrel (30). A ratio between the radius of the flight (40) at the crest (42) to the radius at the root (38) of the screws (14, 16) is in the order of 1.04 to reduce the total amount of product in the barrel (30) at any given time and decreasing the product residence time in the extruder (12). In the most preferred form, the food product is aerated and is supplied in discrete volumes from at least one and preferably from multiple sources (48), with the supply of discrete volumes for individual servings being delayed to substantially prevent intermixing in the extruder (12).