Revealing the relationship between the anti-caking function of wet hydrate crystals and water migration: a case study of glucose monohydrate†

The inadequate understanding of multisource water migration during the drying of wet hydrate crystals often results in the loss of the anti-caking function. Taking glucose monohydrate as a case, this work traced the water migration of wet hydrate crystals during the drying process, elucidated the essential relationship between water migration and the caking resistance of products and put forward the optimal drying scheme based on the caking behavior. Experiments and simulations indicate that the free water on the crystal surface escapes first, resulting in high caking resistance. Subsequently, the remaining free water and crystal lattice water escape, collapsing the crystal. While physically destroying the crystal morphology, the crystal form also changes. Both of them can accelerate caking. Based on the understanding of water migration and caking behavior, the optimal drying scheme for wet glucose monohydrate crystals was proposed as drying at 60 °C for 25 minutes to control the total water content close to the theoretical crystal water content (9.09 wt%). The knowledge obtained can guide the design of drying schemes for retaining the anti-caking function and competitive marketability of hydrate crystals.