The effects of initial water temperature (X-1, 20-72 degrees C), pressure reduction rate (X-2, 60-90 mbar/min), agitation speed (X-3, 300-600 rpm) as well as condensing temperature (X-4, -10 -2 degrees C) during immersion vacuum cooling (IVC) of Irish cooked sausages were evaluated and optimised by response surface methodology for the first time. The cooling loss, colour, texture and moisture content of the sausages were estimated. The significant polynomial regression models on cooling time (P < 0.001) and hardness (P < 0.05) were established. Results showed that the condensing temperature affected the cooling time of IVC sausage significantly (P < 0.001), while hardness was significantly influenced by initial water temperature and condensing temperature. Three optimum operational modules were determined and validated. The cooling times in all modules were compliant within US Department of Agriculture (USDA). Module 3 (X-1: 4.51 degrees C, X-2: 72.88 mbar/min, X-3: 459.09 rpm, X-4: -8 degrees C) was the most practical option for achieving the required high cooling rate with high-quality properties.