Anthocyanins/chitosan films doped by nano zinc oxide for active and intelligent packaging:comparison of anthocyanins source from purple tomato or black wolfberry

The multifunctional films was prepared by blending chitosan and nano-ZnO with purple tomato anthocyanins or black wolfberry anthocyanins.The properties of films functioned by anthocyanins source and nano-ZnO content were studied.It was found purple tomato anthocyanins showed more significant color change against pH than black wolfberry anthocyanins.The nano-ZnO were widely dispersed in matrix and enhanced the compatibility of anthocyanins with chitosan.However,the anthocyanins source influenced the properties of the films more slightly than nano-ZnO addition.The tensile strength,antioxidant and antibacterial effects of the chitosan films dramatically increased after cooperated by nano-ZnO and anthocyanins,which also enhanced with increase of nano-ZnO content,whereas the elongation at break of the composite films decreased.Especially,the anthocyanin and nano-ZnO promoted the antibacterial activity of films synergistically.Composite films made from black wolfberry anthocyanins exhibited higher mechanical performance than those made from purple tomato anthocyanins but weaker antibacterial effects.The purple tomato anthocyanins/chitosan and nano-ZnO/purple tomato anthocyanins/chitosan films effectively reflected pork spoilage,changing their colors from dark green to brown,indicating the potential for applications in active and intelligent food packaging.