Preparation And Properties Of Chitosan-anthocyanins Composite Films

Chitosan(CS)is the partially or completely deacetylated product of chitin by concentrated alkaline solution treatment.CS has the advantages of biocompatibility,biodegradability,non-toxicity,antioxidant,antimicrobial and anticancer properties.Anthocyanins are natural and water-soluble colorants with excellent antioxidant,antimicrobial and pH-sensitive properties.In this study,active and intelligent packaging films were prepared by incorporating chitosan with anthocyanin-rich purple-fleshed sweet potato extract(PSPE)and black soybean seed coat extract(BSSE),respectively.The effect of PSPE and BSSCE incorporation amounts on the physical,structural,antioxidant and pH-sensitive properties of the films was determined in detail.(1)Antioxidant and intelligent pH-sensing films were prepared by incorporating anthocyanin-rich PSPE into chitosan matrix.Effect of PSPE incorporation on physical,structural,antioxidant and pH-sensing properties of chitosan-PSPE films was determined.Eight principal compounds in PSPE were identified as anthocyanins based on mass spectroscopic analysis.Due to abundant anthocyanin content,PSPE could change its colors with changing pH.The incorporation of PSPE could significantly increase the thickness,water solubility,UV-vis light barrier property and thermal stability of chitosan film.However,the incorporation of PSPE could decrease the moisture content,elongation at break and crystalline character of chitosan film.Water vapor barrier property and tensile strength of chitosan film were almost unchanged by PSPE incorporation.Microstructure observation showed a homogeneous state of chitosan-PSPE films.The existence of intermolecular interactions between PSPE and chitosan matrix was confirmed by infrared spectroscopy.Antioxidant assays showed chitosan-PSPE films could scavenge free radicals in dose-and time-dependent manners.Moreover,chitosan-PSPE films exhibited visible color changes along with the pH change.(2)Antioxidant and pH-sensitive chitosan based films were developed by incorporating different amounts of BSSCE.Spectroscopic analysis showed the main anthocyanins in BSSCE were cyanidin-3-O-galactoside(21.38%),cyanidin-3-O-glucoside(63.30%)and peonidin-3-O-glucoside(11.92%).Incorporation of BSSCE could greatly alter the barrier,optical and mechanical properties of chitosan film.Notably,chitosan-BSSCE films presented better water vapor and UV-vis light barrier properties and higher mechanical strength than chitosan film.However,chitosan-BSSCE films exhibited lower moisture content and transparency than chitosan film.Among all films tested,chitosan-BSSCE film containing 15wt%of BSSCE on chitosan basis exhibited the best performance.Importantly,chitosan-BSSCE films showed dose-and time-dependent 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity.Moreover,color variations were observed in chitosan-BSSCE films by changing pH.