The performance of an extrusion process designed to convert acid casein to sodium caseinate was evaluated relative to screw speed, temperature and feed rate; their effects on mixing, conveying, specific energy consumption (SEC), pressure, product temperature and end product physicochemical characteristics were considered. The effect of the process variables were assessed in terms of resulting residence time distribution (RTD) and associated parameters, and compared to theoretical models in an attempt to describe the flow behavior in the extruder The process variables did not have a significant effect on physicochemical properties, however they strongly affected RTD patterns, SEC, pressure generated and product temperature. A detailed analysis of the process is presented, indicating that the twin-screw extruder reactor is well described by a plug flow/perfect mixing model. The process produced a well mixed homogeneous product of comparable quality to conventionally manufactured caseinate and the performance analysis carried out provides a solid basis for the further optimization of such a process.