Preparation and characterization of the dimethyl sulfide-β-cyclodextrin inclusion complex

Dimethyl sulfide has been widely used in flavors and can also be used as a solvent and catalyst. However, dimethyl sulfide is volatile, and its lasting power is weak. Furthermore, dimethyl sulfide is insoluble in water and is unstable in some cases. This study concentrated on the encapsulation of dimethyl sulfide in β-cyclodextrin to form an inclusion complex and to improve the durability, water solubility, and stability of dimethyl sulfide. The product was successfully produced and characterized by scanning electron microscopy, diffraction of X-rays, and thermal analysis. The dimethyl sulfide loading capacity is 6.40±0.08%. Based on the thermal release characteristics of dimethyl sulfide, the kinetic and thermodynamic parameters were obtained. The apparent activation energy, pre-exponential factor, and reaction order of the dimethyl sulfide release reaction were obtained and the values were 95.0 ± 0.1 kJ/mol, 1.03 × 10¹⁵ s^-1 , and 1, respectively. The activation entropy change, activation enthalpy change, and activation Gibbs free energy change were 41.6 J/K, 95.0 kJ/mol, and 81.3 kJ/mol, respectively, during the process of dimethyl sulfide release at 56.7℃. To make it clear that the dimethyl sulfide molecule interacts with β-cyclodextrin molecule, molecular simulation was used to investigate the formation process of the dimethyl sulfide-β-cyclodextrin inclusion complex. The binding energy and the optimized structure were obtained. When the Z coordinate of the S atom in the dimethyl sulfide molecule is 1.1 × 10^-10  m, the binding energy attained the minimum value, -51.3 kJ/mol. These basic data are helpful for understanding the dimethyl sulfide-β-cyclodextrin inclusion complex formation mechanism and the interaction between dimethyl sulfide and β-cyclodextrin. PRACTICAL APPLICATION: By forming an inclusion complex with β-cyclodextrin, the stability, durability, and water solubility of dimethyl sulfide can be improved. Dimethyl sulfide-β-cyclodextrin inclusion complex can be widely used in the food, beverage, flavor, and fragrance industries. The kinetic and thermodynamic parameters, binding energy, and the results of molecular simulation are helpful to understand the dimethyl sulfide-β-cyclodextrin inclusion complex formation mechanism and the interaction between dimethyl sulfide and β-cyclodextrin.