Chitosan‐based film incorporated with anthocyanins of red poppy (Papaver rhoeas L.) as a colorimetric sensor for the detection of shrimp freshness

Summary This study introduces a novel intelligent film based on chitosan (Ch) incorporated with a new natural dye of red poppy as a colorimetric sensor for the real‐time detection of shrimp freshness. The colour changeability of red poppy anthocyanins (RPAs) in a pH range of 2–12 was confirmed by the UV–vis spectra. The indicator film can respond to the ammonia vapour, with the colour changing of RPAs (brown/light yellow to dark brown) over time. The colorimetric films' light screening, tensile strength and antioxidant properties after the addition of RPAs show an increase. The anthocyanin‐loaded films produce a substantial colour change from brown to light yellow consistent with the shrimp spoilage at the pH threshold, which can inform the quality deterioration of the shrimp. Due to these benefits, the Ch‐RPAs indicator film can be used to visually and real‐timely monitor shrimp freshness in package.