Preparation, Characterization, and Release Kinetics of Zanthoxylum bungeanum Leaf Polyphenol–Chitosan Films

Abstract

This study aimed to prepare a composite film with antioxidant activity for fruit and vegetable preservation. Polyphenols were extracted from Zanthoxylum bungeanum leaves (ZMP), and their composition was studied. ZMP-chitosan film (ZMP/C-film) was prepared by tape casting and the film properties were evaluated. The results revealed that ZMP was mainly composed of seven components: epicatechin (3.24 mg/g), chlorogenic acid (3.59 mg/g), coumarin acid (1.40 mg/g), ferulic acid (4.36 mg/g), quercetin (7.61 mg/g), quercetin (4.52 mg/g), and kaempferol (2.51 mg/g). The opacity of the film incorporated with ZMP significantly increased by 2.28 times. Flexibility (elongation at break) increased by 72%, while the ZMP/C-films had lower tensile strength (32.15–40.3 MPa). Microstructurally, scanning electron microscopy results indicated that ZMP and Chitosan (CS) were compatible. Fourier transform infrared spectroscopy revealed the formation of a dense structure between ZMP and CS. Analysis of X-ray diffraction indicated a tendency toward an increase in the amorphous characteristic of the ZMP/C-film. The kinetic results of polyphenol release indicate that ZMP release was mainly achieved through the dissolution of CS-based polymer frameworks. The release rate and rate of ZMP in the membrane were highest in 3.0% acetic acid (v/v) (33.62%). The scavenging rates of DPPH and ABTS+ free radicals by the 1 g/dL ZMP/C-film were 0.83 and 0.82 times higher than those of 1.0 mg/mL vitamin C (Vc) under the same conditions. In addition, ZMP/C-film was used for strawberry preservation. When stored at 25 °C for 7 d, the weight loss rate and VC content of strawberries preserved with ZMP/C-film decreased by 23.4% and increased by 14.2% compared to C-film, respectively. ZMP/C-film prolonged the shelf life of strawberries by more than 4 days.