Fabrication of Pullulan‐Shikonin Colorimetric Indicator for Visual Monitoring Chicken Freshness

ABSTRACT Chicken spoilage caused by microbial contamination during storage and distribution not only leads to significant food waste but also poses serious food safety risks. To address this issue, a novel colorimetric film was developed using pullulan as the matrix incorporated with shikonin extracted from Arnebia euchroma root for real‐time monitoring of chicken breast freshness. Films were prepared by the casting method, where shikonin (3% or 10% w/w based on pullulan) was incorporated into a pullulan solution (4%, w/v) and dried to obtain pure pullulan and composite films. Increasing shikonin content enhanced the water barrier properties of the indicator while maintaining comparable mechanical properties of the films. Shikonin contains a pH‐sensitive naphthoquinone structure. During chicken spoilage, the accumulation of volatile alkaline substances increases the pH of the film environment, leading to the deprotonation of shikonin and resulting in a colour change of the film. The pullulan films incorporating 3% shikonin (pullulan‐shikonin3) shifted from pink to dusty rose at 4°C and changed from pink to greyish rose at 25°C. The developed pullulan‐shikonin films are anticipated to provide a convenient, non‐destructive and visually intuitive method for assessing chicken breast freshness during storage.