Preparation And Characterization Of Active Smart Food Packaging Materials Based On Anthocyanins

The aim of this study was to prepare hydrophobic(or water-resistant)active smart packaging with high responsiveness using solvent-cast film technology and electrostatic spinning technology.Anthocyanin extracts from four plants(pterocarpus,black wolfberry,inky red rose,and mulberry)were used as p H natural dyes,cinnamaldehyde as an antimicrobial additive,and biodegradable aqueous polyurethane(WPU)and polylactic(PLA)as polymeric matrices.The prepared smart packaging was characterized for comprehensive performance and fresh beef was selected to explore the ability of the indicator film to monitor freshness and extend shelf life.The main research contents and outcomes are as follows:(1)Four anthocyanin extracts were prepared.Then,the extracts of Clitoria ternatea L.were purified using macroporous resin.All four anthocyanin extracts exhibited a wide range of color changes at different p H conditions with excellent color development ability.The purified extracts of butterfly pea showed significantly broader range of indications than before purification.(2)Smart indicator films based on four anthocyanin extracts and aqueous polyurethane were prepared by solvent-cast film method.It was shown that the anthocyanin extracts imparted different colors and properties to the indicator membranes,and filled the defects on the WPU membranes and improved the performance of the WPU membranes.The indicator film has better water vapor barrier and can exist in water-rich environment for a long time.The anthocyanin extract significantly enhanced the mechanical properties of the indicator films(P<0.05).Moreover,the films all had antioxidant properties.Among them,the membranes prepared by Rosa chinensis Jacq were stronger with 67% free radical scavenging rate.In addition,the color development properties and mechanical properties of the indicator membranes prepared from butterfly pea extract and WPU were better.(3)Nanofiber indicator membranes were prepared by electrostatic spinning technique using polylactide(PLA),cinnamaldehyde(CIN)and butterfly pea anthocyanin(BPA)as raw materials.The prepared indicator films showed outstanding antioxidant properties,antibacterial properties,colorimetric ability,hydrophobic properties and fast,non-destructive and reusable color development performance.The nanofiber structure gave the indicator film excellent responsiveness.In addition,the tensile strength of the indicator film(9.56 MPa)was higher than that of the pure PLA electrospun film(4.40 MPa).In particular,the introduction of BPA effectively enhanced the antibacterial ability of CIN.(4)The monitoring experiments on beef samples revealed that the freshness of beef could be easily identified by the naked eye based on the color change of PLA-BPA6/CIN indicator film,and the shelf life of beef was effectively extended at both 4°C and 25°C.