Development of Disulfide Bond Crosslinked Gelatin/ε-Polylysine Active Edible Film with Antibacterial and Antioxidant Activities

Abstract

It is of great significance to use safe raw materials, and spontaneously form covalent crosslinking during the fabrication process to obtain active edible films with excellent performance. Herein, l-cysteine as the source of thiol group was firstly conjugated onto gelatin backbone via 1-ethyl-3-(30-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS) chemistry. Afterwards, the thiol groups in gelatin-l-cysteine (G-Cys) conjugates were oxidized in air to form disulfide bonds, meanwhile the antibacterial polypeptide e-polylysine (e-PL) was incorporated into gelatin matrix to fabricate gelatin/e-polylysine active edible films. The results show that the amount of conjugated l-Cys in G-Cys conjugates ranges from 43.5 to 159.4 mg/g. The disulfide bond crosslinking generated by the oxidation of thiol groups resulted in compact and dense microstructure, which in turn could decrease the moisture content, total soluble matter, water vapor permeability and swelling behavior of gelatin-based edible films, means enhanced water resistance. Moreover, the fabricated gelatin-based edible films showed good mechanical properties, excellent UV light barrier property and effective antioxidant activity. In addition, the incorporated antibacterial polypeptide e-PL endowed gelatin-based edible films with robust antibacterial activity. Overall, the disulfide bond crosslinked gelatin-based edible films incorporated with e-PL could find potential application in the food and drug packaging fields.