Kinetics of lactose crystallization in milk powders – Preconditioning to preserve functionality during storage

This study aims to evaluate the kinetics of lactose crystallization, as influenced by temperature (25–45 °C) and relative humidity (RH) (31–75 %), and to explore strategies for enhancing the storage stability of milk powder by controlling lactose properties. In a fat-filled milk powder, anhydrous β-lactose growth increased with both temperature and RH, whereas α-lactose monohydrate growth increased with RH but was inhibited by elevated temperature at 64 % RH and showed an initial increase followed by a decrease at 75 % RH. The lactose state diagram showed that RH had a greater influence on crystal growth than temperature. Powder preconditioned at 25 °C and 43 % RH, containing anhydrous β-lactose, showed greater resistance to elevated RH (from 43 % to 75 %) and temperature (from 25 °C to 40 °C) than powder with amorphous lactose. The findings suggest that tailoring lactose properties can enhance the storage stability of milk powder.