Trans-2-hexenal/β-cyclodextrin effectively reduces green mold in citrus fruit

Green mold, caused by Penicillium digitatum, is the primary postharvest disease in citrus fruit. Trans-2-hexenal was found to exert a considerable inhibitory effect on the mycelial growth of P. digitatum with a minimum fungicidal concentration (MFC) of 0.106 g L−1. To overcome its hydrophobic restriction, a trans-2-hexenal-β-cyclodextrin inclusion complex (β-CDIC) was prepared by the saturated aqueous solution method. In vitro assays revealed that the MFC of β-CDIC for P. digitatum mycelial growth was 1.00 g L−1, and 10.0 g L−1 β-CDIC apparently reduced the incidence of green mold in citrus fruit inoculated with P. digitatum while maintaining fruit quality. The structure of β-CDIC was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), fourier transform-infrared spectroscopy (FT-IR), thermogravimetric (TG), and nuclear magnetic resonance (NMR) analyzes. The results showed that the H-1 proton of trans-2-hexenal correlated with the H-5′ proton of β-cyclodextrin (β-CD), which was further confirmed by molecular docking analysis. The present study suggests that β-CDIC is a promising candidate for controlling postharvest diseases in citrus fruit.