Development of a pH‐Sensitive Film Based on Starch and Calico Plant (Alternanthera bettzickiana) Extract for Monitoring Shrimp Quality

A pH‐sensitive film was developed to indicate signs of food spoilage of shrimp and certain other protein‐rich products. An extract of the calico plant ( Alternanthera bettzickiana ) (CP) was incorporated into starch film. The effects of different concentrations of CP extract (0%, 1%, 2%, 3% and 4% v/v) were investigated. The morphology, mechanical and thermal properties of the films were characterized. Colour parameters and water contact angles were determined, and antioxidant activity and pH sensitivity were investigated. The colour and radical scavenging activity of the starch films were affected by the content of CP extract. All the starch films containing CP extract were sensitive to buffer solutions at different pH and to volatile ammonia, and although a starch film containing 1% v/v of CP showed the highest water contact angle (124.37°), tensile strength (38.03 MPa) and T max (336°C), a starch film containing 4% v/v of CP most effectively indicated the spoilage of shrimp by showing the clearest changes in colour from light pink at 0 h to caramel at 16 h and finally to yellow at 24 h. The results indicated that starch film with 4% v/v of CP extract could be used as a novel antioxidant, pH‐sensitive film for food packaging.