Lycium ruthenicum Murr. is a functional food with abundant anthocyanins. Since anthocyanins can change colors under different pH conditions, pH-sensitive packaging films were developed based on cassava starch and L. ruthenicum anthocyanins (LRA). Effect of LRA content on the physical, structural, antioxidant and pH-sensitive properties of starch-LRA films were evaluated. In addition, starch-LRA films were applied to monitor the freshness of pork. Spectroscopic analysis showed LRA contained six kinds of anthocyanins. The incorporation of LRA significantly enhanced the water vapor and ultraviolet-visible light barrier ability, tensile strength and antioxidant potential of starch film. Moreover, the barrier, antioxidant and pH-sensitive properties of starch-LRA films were closely related with LRA content. However, the thermal stability of starch film was not affected by LRA. Fourier transform infrared and X-ray diffraction analyses revealed intermolecular interactions (hydrogen bonds) formed between starch and LRA in the films. Starch-LRA films are pH-sensitive and could change their colors in different buffer solutions (pH 2-13). When applied to monitor the freshness of pork, starch-LRA films exhibited remarkable color variations with the quality change of pork. Our results suggested starch-LRA films could be used as active and intelligent packaging films in food industry.
