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.