High strength, controlled release of curcumin-loaded ZIF-8/chitosan/zein film with excellence gas barrier and antibacterial activity for litchi preservation.

Polysaccharide films containing protein additives have good application prospects in agriculture and food field. However, interfacial incompatibility between hydrophobic proteins and hydrophilic polymers remains a major technical challenge. In this work, the interfacial compatibility between hydrophobic zein and hydrophilic chitosan (CS) is improved by the chemical crosslinking between zinc ions of curcumin-loaded zeolitic imidazolate framework-8 (Cur-ZIF-8) with CS and zein. With the improvement of interface compatibility, the results show that the elongation at break and O2 barrier property of synthesized Cur-ZIF-8/CS/Zein are 9.2 and 1.5 times higher than CS/Zein, respectively. And the Cur-ZIF-8/CS/Zein exhibits superior antibacterial and antioxidant properties as well. Importantly, Cur-ZIF-8/CS/Zein can also be used as an intelligent-responsive release platform for curcumin. As a result, Cur-ZIF-8/CS/Zein can keep the freshness and appearance of litchi at least 8 days longer than that of CS/Zein. Therefore, this study provides a novel method to improve the interfacial compatibility between hydrophobic proteins and hydrophilic polymers, and is expected to expand the application of protein/polymer composites in agriculture and food field.