Encapsulation and sustained release properties of watermelon flavor and its characteristic aroma compounds from γ-cyclodextrin inclusion complexes

Encapsulation of flavors with cyclodextrins can improve their stabilities, sustained release properties, and shelf-lives. However, few studies have attempted to ascertain whether the aroma composition of the encapsulated flavor changes during preparation and release processes. This study investigated the inclusion and release behavior of a sustained release system of watermelon flavor (WF) encapsulated within γ-cyclodextrin (γ-CD). Gas chromatography-mass spectrometry (GC–MS) was employed to determine the aroma composition of encapsulated watermelon flavor. The inclusion complexes were characterized by dynamic light scattering (DLS), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and wide angle X-ray diffraction (WAXD). Individual release behavior of the seven characteristic aroma compounds from γ-CD was investigated based on the Avrami equation. Results showed that the aroma composition of the encapsulated watermelon flavor was different from that of the free, although watermelon flavor was successfully encapsulated in γ-CD. Both the inclusion and release behavior of this sustained release system were significantly affected by the molecular structures of the aroma compounds. The inclusion efficiency decreased in the order of alcohols > aldehydes > esters, while the release ratio decreased with the increase of hydrophobicity, implying the different affinities of hydrophobic flavor guests to γ-CD. Therefore, the aroma composition of the encapsulated flavor during preparation and release processes cannot keep initial due to various structures of aroma compounds. This phenomenon should not be ignored to achieve prospective release patterns of flavor from inclusion complexes.