Effect of Black Rice Starch on Structure and Physical–Mechanical Properties of Carboxymethyl Chitosan/Gellan Gum-Based Intelligent Food Packaging Film and Application in Monitoring Shrimp Freshness

Visual freshness monitoring is challenging in intelligent seafood packaging. This study developed low-acyl gellan gum (LGG)-based intelligent films incorporating anthocyanin (BRE), carboxymethyl chitosan (CMCh), and black rice starch (BRS) and evaluated their effects on film structure, physical–mechanical properties, and shrimp freshness-monitoring performance. Films prepared via solution casting were evaluated using structural, mechanical, and barrier analyses, alongside shrimp spoilage trials at 25 °C. Structural analyses revealed an integrated polysaccharide network. CMCh reinforced the matrix and increased tensile strength, whereas partially retained BRS granules introduced microstructural heterogeneity, reducing strength and increasing water vapor permeability, highlighting a trade-off between mechanical performance and moisture transport. Consequently, BRS-containing films reduced BRE release, improved pigment retention, and resulted in less intense color changes associated with total volatile basic nitrogen (TVB-N) accumulation during shrimp spoilage. Overall, these results suggest that CMCh and BRS composition-dependently modulate the structure, water vapor transport, pigment retention, and colorimetric response of LGG-based films for visual monitoring of shrimp freshness under accelerated spoilage conditions.