Uncovering the role of impurity sugars on the crystallization of d-tagatose crystal: Experiments and molecular dynamics simulations.

Impurity sugars produced in upstream process of functional sugars are significantly impacting the product quality. In this work, the effect of congeners (d-maltose (d-MAL), d-fructose (d-FRU), d-glucose (d-GLU)) on primary and secondary nucleation of d-tagatose (d-TAG) crystals was investigated. The impurity sugars showed an inhibition on primary nucleation of d-TAG crystals, while a promotion on the secondary nucleation of d-TAG. Interestingly, the impact of impurity sugars on d-TAG crystal growth was similar to that on primary nucleation. The diffusion ability, hydrogen bonding forming ability, interaction energy of d-TAG crystal surfaces and impurity sugars were evaluated by molecular dynamics (MD) simulations to reveal the nucleation and growth behavior. Based on the above findings, we designed the d-TAG crystallization experiments, and obtained d-TAG crystals with uniform particle size distribution and regular morphology. This study helps to understand the influence of impurity sugars on crystallization, guiding the industrial manufacturing of functional sugars.