Research On Controllable Preparation Of Xylitol/Menthol Co-crystal

Xylitol, a pentitol with high sweetening power and anticariogenic properties, is one kindof sugar substitute, whose main branches of use are food production, perfumery,pharmaceutics, and chemistry. Xylitol crystals are white, odorless, and hygroscopic. Menthol,is a kind of white crystal，having effect of cooling and refreshing, and can be widely used insome common cold medications, tooth pastes, confectionery and cosmetics. Menthol is avolatile substance, and its volatility makes it difficult to be used in preparation and application.Co-crystallization is the encapsulation of the materials with different composition andproperties, then forming homogeneous mixtures with a variety of crystalline state. Theco-crystals exhibit good performance and improve the solubility of the product, uniformity,liquidity, compressibility and stability. In this thesis, a better preparing scheme for xylitol andmenthol is presented based on a systematic study of its crystallization process. The maincontents go as follows.The solubility and induction periods of xylitol in binary ethanol+water solvent mixturesat different temperature were measured with dynamic method, respectively. The solubilitieswere correlated by CNIBS/Redlich-Kister equation. The thermodynamic properties of thesolution process, including the Gibbs energy, enthalpy and entropy, can be calculated by thevan’t Hoff analysis. The primary nucleation rate of the xylitol/menthol co-crystal wasestimated based on experimental induction periods data.In this work, menthol was chosen as the active flavor compound. The co-crystallizationof xylitol with menthol was obtained in a supersaturated xylitol water and ethanol aqueoussolution. The optimal conditions within the range studied for preparation of thexylitol/menthol co-crystal were obtained by response surface methodology. Hygroscopicityand water activity (aw) of the xylitol/menthol co-crystal were determined in this work.The microstructure, thermal stability and crystallization mechanism of these co-crystallizedproducts were analyzed by scanning electron microscopy (SEM), differential ScanningCalorimetry (DSC)，X-rays Diffraction (XRD), respectively.Using Flynn-Wall-Ozawa and Friedman models, the thermal Kinetics of thexylitol/menthol co-crystal was analyzed，which provided basic data for thermal stability study,and provided important guidance for the storage and processing conditions.These analyses confirmed that co-crystals own different thermal property and crystal structure. This work can convey important information for application of co-crystallizationtechnique and the development of food new materials.