Research On The Crystallization And Caking Mechanism Of Maltitol

Maltitol is crystallized with seeding by cooling in industry, often with largeamount of fine crystals and wide crystal size distribution, caking during drying. Theinvestigation on the crystallization and caking of maltitol has been performed.Firstly, the solid-liquid equilibrium behavior of maltitol in water, water-ethanoland water-DMF was investigated by the gravimetric method, Apelblat equation wasemployed to correlate the solubility data. Additionally, the viscosity of maltitolaqueous solution with different concentration was obtained at20℃, and the linerelationship between the logarithm of viscosity and the reciprocal of temperature wasdetermined.Secondly, the nucleation kinetics of maltitol in batch cooling crystallization wasinvestigated using focus beam reflectance measurement(FBRM) and a novel methodwas proposed to determine the induction time from the trend of the crystal medianchord distribution given by FBRM. Based on the relationship between the inductiontime and the supersaturation, the nucleation mechanism was obtained. Additionally,combining the classical nucleation theory (CNT) and Arrhenius’ principle, thecrystal-solution interfacial energy and the energy barrier of homogenous nucleationwere calculated. From the scanning electron microscope(SEM) images, the growthmechanism of maltitol was identified as surface nucleation growth and the surfaceentropy factor calculated from the kinetic analyses of tinddata corroborated thisgrowth mechanism.Based on the investigation of the crystallization thermodynamics, nucleationkinetics of maltitol, the effects of temperature, the amount and size of seeds, stirringspeed, the cooling rate on the crystal size distribution were experimentally studied indetail, and the conditions of cooling crystallization were initially identified. Abberefractometer, FBRM (Focused Beam Reflectance Measurement), MalvernMastersizer and polarization microscope etc. were employed to investigate thesupersaturation, nucleation, growth and secondary nucleation in the process ofcrystallization. Moreover, the product without fine nuclei was obtained by optimizingthe process of crystallization.According to the orthogonal experiment, the primary and secondary orders of factors which affect the caking of maltiol were identified. Combining the SEM imagesand the hot stage microscope, the mechanism of caking was derived and theconditions of drying with no-caking products were also obtained.The research results in this work were not found in literatures.