Ferulic Acid-in-CD-MOF-1 and Natamycin Nanocapsules as a Dual-Functional System for Antioxidant and Antifungal Litchi Preservation

Litchi ( L. chinensis Sonn.) is a perishable fruit that is vulnerable to oxidative browning and fungal infection. Herein, ferulic acid and natamycin were chosen as the antioxidant and antimycotic agents, respectively. To improve their water solubility, we used CD-MOF-1 to encapsulate ferulic acid. Meanwhile, natamycin was encapsulated with gum arabic and pullulan. The most homogeneous and stable natamycin nanocapsules were fabricated through stirring 0.5 mg/mL natamycin using 2.5% (w/v) gum arabic-pullulan (1:1, w/w, 1.25% each) in water. The main encapsulation mechanisms of ferulic acid and natamycin were electrostatic interactions between the carboxyl groups of ferulic acid and K + ions from CD-MOF-1 and hydrophobic interactions between the macrocyclic lactone ring of natamycin and the protein part of gum arabic, respectively. In addition, pullulan was indispensable for stabilizing natamycin. The antioxidant and antifungal composite sol presented 99.85% oxidation inhibition and 79.06% mycelial growth inhibition and effectively delayed the oxidative browning and fungal decay on litchi pericarps.