Development of Intelligent and Active Gelatin-Based Packaging Film Incorporating Red Onion Anthocyanins and Encapsulated Citronella Oil

With rising living standards, consumer demand for fresher food continues to increase. Consequently, the development of multifunctional packaging materials that enable real-time freshness monitoring, delay spoilage, and ensure environmental sustainability has become a central research focus. The present study developed an antibacterial and pH-responsive smart packaging film, formulated from a κ-carrageenan/gelatin (CG) matrix. This film incorporated anthocyanins extracted from red onion skin (ROSA) and citronella essential oil encapsulated in β-cyclodextrin (OBDs) as functional additives, herein referred to as the CGR/OBDs composite film. The composite films exhibited strong pH sensitivity, ammonia responsiveness, color stability, effective barrier properties, and notable antioxidant activity (96.4% ABTS and 79.3% DPPH radical scavenging rates). The sustained release of citronella essential oil over approximately 40 h conferred excellent antibacterial performance, with inhibition rates of 94.8% against Staphylococcus aureus (S. aureus) and 91.6% against Escherichia coli (E. coli). Application in shrimp preservation further demonstrated an extended shelf life and real-time freshness monitoring through distinct colorimetric shifts. The findings highlight the potential of CGR/OBDs films as visual indicators for food freshness in intelligent packaging, offering a promising strategy to enhance food safety and reduce waste.