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

• The effect of impurity sugars on the thermodynamics and kinetics of d -TAG crystallization has been studied. • Impurity sugars reduce the rate of d -TAG primary nucleation and crystal growth, but accelerate secondary nucleation rate. • The mechanism of the effect of impurity sugars on the nucleation and growth of d -TAG crystals was revealed by experiments and MD 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. [ABSTRACT FROM AUTHOR]