γ-Cyclodextrin-Encapsulated Cinnamaldehyde for Citrus Preservation and Its Potential Mechanisms against Penicillium digitatum

In this study, aγ-cyclodextrin-cinnamaldehyde inclusion compound (γ-CDCL) was prepared to control green mold caused byPenicillium digitatum(P. digitatum) in citrus. The results showed that the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) ofγ-CDCL against the mycelial growth ofP. digitatumwere 2.0 g L−1and 4.0 g L−1, respectively. Simultaneously, eight × MFCγ-CDCL could effectively reduce the incidence of green mold in citrus fruit without impairment of the fruit qualities, meanwhile, eight × MFCγ-CDCL was comparable to Prochloraz in controlling fruit under natural storage conditions. The structure ofγ-CDCL was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), and nuclear magnetic resonance (NMR) analyses. Results showed that the successful preparation ofγ-CDCL was due to the spatial interaction between H-4,8 of cinnamaldehyde and H-5′ ofγ-cyclodextrin. Meanwhile, the cell membrane permeability ofP. digitatumwas impaired byγ-CDCL through massive accumulation of reactive oxygen species, whereas the cell wall integrity was barely affected. These results indicated thatγ-CDCL might inhibit the growth ofP. digitatumthrough a membrane damage mechanism and it is a promising alternative to chemical fungicides in controlling the post-harvest citrus decay.Keywords:inclusion compounds;inhibitory activity;green mold;action mechanism;membrane permeability