Developing a simultaneously antioxidant and pH-responsive κ-carrageenan/hydroxypropyl methylcellulose film blended with Prunus maackii extract.

к-Carrageenan and hydroxypropyl methylcellulose were used as matrix materials in which the extract of Prunus maackii pomace (EPm) was added to prepare a simultaneously antioxidant and pH-responsive film. EPm effectively increased the flexibility, barrier properties, antioxidant activity and pH-responsiveness of the film. When EPm content was increased to 8%, the elongation at break, heat-sealing strength and oxygen permeability of the film could reach 43.20 ± 2.07%, 1096.39 ± 51.29 N/m and 2.23 ± 0.02 cm³ mm m^-2 day^-1 atm^-1, respectively. Ultraviolet-visible spectra of EPm and the films color changed significantly in the range of pH 2.0-12.0. The κC/Hm/EPm_y film obviously slowed the oxidation of lard compared with commercial PE film, and exhibited visible changes from red to purple when TVB-N in the pork reached 13.18 mg/100 g which was close to the freshness limit of 15.00 mg/100 g. Therefore, the κC/Hm/EPm_y film can be promisingly used for extending oil shelf life and indicating the protein-rich food quality.