A highly stable gellan gum/potato starch/anthocyanin smart film with ferulic acid co-pigmentation for monitoring fish freshness.

A novel high stability pH-sensitive smart film (GGPS-R-FA) was prepared by using gellan gum (GG) and potato starch (PS) as the film-forming material, red cabbage anthocyanins extract (RCAE) as the indicator, and ferulic acid (FA) as the co-pigmentation agent. The enhancement effect of co-pigmentation on the stability of RCAE, as well as the performance and application of smart film were investigated. The RCAE co-pigmented with FA showed higher absorbance and greater thermal stability, as evidenced by the retention of anthocyanin content and thermodynamic parameters. The retention rates of anthocyanin content was increased from 24.59 % to 37.94 %. Structural characterization showed that molecular interactions protected the structure of anthocyanins and contributed to form a more stable film network. The EAB of the films was improved to 25.13 % and the opacity was increased to 5.02 A·mm. The co-pigmented films exhibited excellent color stability after co-pigmentation. The ∆E of GGPS-R-FA films was lower than 3 during 120 days of storage at 4 °C. The films exhibited a sensitive responsiveness to pH and ammonia. When the films were applied to monitor the fish's freshness, the color changes of GGPS-R-FA1 and GGPS-R-FA2 films represented a strong correlation with the spoilage indices of grass carp.