Whole milk powder production using combined cryoconcentration and freeze-drying process

The aim of this study is 1to investigate the feasibility of coupling cryoconcentration and freeze-drying for the production of whole milk powder. A parametric study was carried out on the cold wall cryoconcentration process to identify the key parameters. The influence of three factors (initial and final cold wall temperatures, and freezing time) on response variables (separation yield and recovery rate) was analyzed. All factors were found to significantly influence responses. The optimum conditions chosen were: jacket temperature -0.5 degrees C, initial and final cold wall temperatures -3 degrees C and -6.5 degrees C respectively, with a freezing time of 3 h. These parameters enabled the production of cryoconcentrated solutions with a milk solution mass fraction of around 20% from initial solutions of 12%. The concentrated solution was then subjected to a pilot-scale freeze-drying cycle. Optimization of the freeze-drying conditions enabled to halve the total drying time, while achieving moisture levels below 5%. The freeze-dried powders were compared to powders obtained through cryoconcentration/freeze-drying coupling in terms of moisture content, surface area, dynamic vapor sorption, scanning electron microscopy observation, and mid infrared spectroscopy analysis. No significant difference was observed. Following this study, we concluded that the combination of cryoconcentration and freeze-drying is worthwhile, while preserving powder quality.