Preparation, physicochemical characterization, and computational studies of aldehyde aroma compounds/cyclodextrin inclusion complexes

Encapsulation with cyclodextrins (CDs) is one of the effective means for the controlled release of aroma compounds. Nevertheless, the aroma profile of the essence or essential oil often exhibits significant differences before and after encapsulation, which seriously affected the aroma quality of steady-state products. However, the exact mechanism underlying this issue has yet to be fully elucidated. In this study, the formation and mechanism of ICs between α-, β-, γ-CD and 5 characteristic aldehydes (citral, cinnamaldehyde, benzaldehyde, citronellal, and 5-methylfurfural) were investigated through a combination of experimental methods and computer simulations. The molar inclusion ratio between each CD and 5 selected aldehydes were consistently 1:1 according to phase solubility method, equimolar continuous transformation (Job’s) method and isothermal titration calorimetry (ITC) method. Based on this, each corresponding IC was constructed and confirmed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) spectroscopy. Molecular dynamics (MD) simulation was used to further analyze the formation and stabilization mechanisms of the ICs, and MMPBSA and independent gradient model (IGM) analysis was combined to analyze the driving force inducing the formation of ICs. The results showed that the dominant driving force for stabilizing ICs was identified as van der Waals interaction, followed by hydrophobic interaction and then coulomb interaction. Moreover, hydrogen bond (H-bond) and steric hindrance also exerted certain influence on the combination between host and guest.