SPRAY- AND FREEZE-DRYING OF ADDITIVE-FREE WHOLE MILK: PHYSICOCHEMICAL, TECHNO-FUNCTIONAL, FLOW, AND MORPHOLOGICAL CHARACTERISTICS OF POWDERS, AND PROCESS EFFICIENCY

Resumen

This study evaluated the effects of spray drying and freeze drying on additive-free whole milk powder in terms of physicochemical, color, techno-functional, flow, morphological, and process-efficiency properties. Three independent milk batches were processed under four spray-drying conditions defined by inlet air temperature (130 and 180 °C) and feed flow rate (0.2 and 0.8 kg/h), and one freeze-drying condition was used for comparison. Spray-dried powders showed lower moisture and water activity than freeze-dried powder, indicating greater water-removal efficiency and storage stability under the conditions evaluated. They also exhibited spherical, denser particles and narrower size distributions than the irregular, porous freeze-dried particles. In contrast, freeze-dried powder showed much faster wettability and better flowability, but also higher hygroscopicity, water activity, browning index, and drying losses, suggesting lower physicochemical stability. Among the spray-drying conditions tested, 130 °C/0.8 kg/h provided the best overall balance between stability and process efficiency, although the higher moisture variability observed for this condition indicates that additional replicates would be needed to confirm reproducibility. The 180 °C/0.8 kg/h condition produced a narrower particle-size distribution and lower moisture, but it also impaired wettability and increased mass losses.