Effect of Crystalline Metastasis of Lactose on Hardness of Compressed Baby Milk Powder

The purpose of this study was to examine the relationship between the crystalline metastasis of lactose, which is a main component baby milk powder, and the hardness of baby milk powder compressed by humidification followed by drying. Because baby milk powder is manufactured using a spray dryer, lactose in compressed baby milk powder exists in an amorphous (solid dispersion) form. X-ray diffraction measurement showed that this amorphous lactose metastasized to β-form crystalline lactose, and thereafter metastasized to the α-form during the humidification-drying process. As a result of this crystalline metastasis, the hardness of the compressed baby milk powder increased, and then decreased. Furthermore, scanning electron microscopy (SEM) showed bridging structures between the particles increased and then decreased during the humidification-drying process. This showed that bridging structures between the particles produced by crystalline metastasis of lactose as a result of the humidification-drying process, which leads to an increase in the hardness of the compressed baby milk powder. These results show that the necessary degree of hardness of the porous compressed baby milk powder (necessary for packaging and transportation) resulted from the humidification-drying process.