Cyclodextrin, which has a unique “outer hydrophilic and inner hydrophobic” structure, can be used as an excellent carrier to protect volatile bioactive compounds that are susceptible to oxidative degradation for improved solubility, stability, and bioavailability. In this paper, we summarize the structures and properties of cyclodextrins and elucidate their inclusion mechanism with respect to the interactions between the host cyclodextrins and guest molecules and the factors influencing them including the inclusion reaction between cyclodextrin monomers and guests, the self-assembly behavior of cyclodextrin monomers, and the inclusion mechanism between the supramolecular system formed by this self-assembly behavior and guest molecules. Then, the mechanism for the interface stability of cyclodextrins in the presence and absence of surfactants and the mechanism by which composite emulsifiers formed from the self-assembly of cyclodextrins with a surfactant stabilize guests. Finally, the release mechanism and the kinetic models of sustained release of guest molecules from inclusion complexes of cyclodextrins as well as the factors affecting them are elucidated, and future research prospects of cyclodextrins in the supramolecular field are discussed in order to provide a reference for follow-up research.

Grain and oil products, the most basic materials for human survival, are subject to various factors such as temperature, moisture, oxygen and microorganisms, triggering a series of biochemical reactions which can cause the generation of off-flavors such as sour and rancid odor. Clarifying the types and formation mechanism of rancid odor compounds and regulating them can help greatly improve the quality of grain and oil products. This article summarizes the key volatile compounds contributing to rancid odor produced during the storage and processing of grain and oil products, and clarifies their formation mechanisms from three aspects: lipid hydrolysis and oxidation, protein oxidative aggregation and the interaction between volatile and non-volatile compounds. Furthermore, the control measures to remove or mask the rancid odor are reviewed. The removal methods mainly include biological breeding and improvement, new storage and preservation technologies, traditional and emerging processing techniques and chemical methods; the masking methods include encapsulation technology based on host-guest interaction, aroma enhancement with exogenous enzymes and the addition of exogenous aroma enhancing ingredients. This paper can provide a theoretical reference and technical support for rancid odor control and flavor quality improvement of grain and oil products.

Cyclodextrin (CD) can form inclusion complexes with the guest molecule through supramolecular interaction, preserving or even enhancing the properties of the guest molecule. Molecular simulation is an important research tool to explore the interaction of CD with the guest molecule, which has been widely used in research on cyclodextrin inclusion reaction. In this paper, a brief overview of molecular simulations including quantum mechanics, molecular docking and molecular dynamics simulation was given, and the basic principles of and mainstream software and commonly used force fields for molecular docking and molecular dynamic simulation were summarized. Moreover, recent progresses on their application in cyclodextrin inclusion research were reviewed from four aspects: characterization of molecular structure changes, characterization of intermolecular interaction, solvent effects and synergistic stabilization. Research results show that the size of the hydrophobic cavity and the initial orientation of the guest within the cavity have very important effects on the structure of guest/cyclodextrin inclusion complexes; van der Waals interactions are the major driving force for the cyclodextrin inclusion reaction, and the formation of intermolecular hydrogen bonds is an important factor for the stability of the inclusion complex. The explicit solvent model is a powerful tool to study the solvent effect of the cyclodextrin inclusion reaction. Finally, the authors believe that molecular simulation will be useful for further investigations of the cyclodextrin inclusion process from the perspectives of multi-scale phenomena and machine learning.