Biodegradable Smart Packaging Films for Food Safety: Emerging Materials, Embedded Sensing, and Sustainable Design Strategies

Biodegradable smart packaging films seek to reconcile three demands that are often treated separately: protection of food, in-package sensing of quality or safety changes, and lower end-of-life persistence. This critical narrative review evaluates how emerging biopolymer matrices, natural responsive compounds, active agents and embedded sensing technologies can be combined without allowing the word “biodegradable” to substitute for evidence of packaging performance or environmental benefit. Literature published from 1 January 2015 to 10 July 2026 was considered, with earlier foundational studies retained where they established concepts or sensing architectures. The strongest experimental evidence concerns colourimetric freshness indicators, particularly anthocyanin-containing polysaccharide films that respond to pH and volatile basic compounds generated during spoilage of protein-rich foods. Chitosan, starch, alginate, pectin, carrageenan, gelatin, cellulose-derived materials, poly(lactic acid) and polyhydroxyalkanoates provide complementary processing and barrier attributes, but hydrophilicity, pigment instability, migration, brittleness and process-temperature sensitivity remain recurrent constraints. Active–intelligent films can couple antimicrobial or antioxidant action with freshness reporting, yet these functions may interfere with one another and can decouple sensory spoilage from microbiological hazard. Electronic and wireless platforms provide richer and potentially quantitative information, but conventional conductors, chips and batteries undermine biodegradability unless the sensor is designed as a separable module or with transient materials. Across the evidence base, laboratory casting and short storage trials greatly outnumber pilot-scale converting studies, standardised migration assessments, pathogen-specific validations and life-cycle comparisons at equivalent food-protection performance. A defensible design strategy therefore begins with the food hazard and required shelf-life function, then selects a compatible matrix, sensing chemistry, active component, manufacturing route and verified end-of-life pathway. Progress towards safe and sustainable commercial systems will depend on calibration against food-specific reference methods, food-contact toxicology, scalable printing or extrusion, realistic life-cycle boundaries that include avoided food waste, and modular architectures that prevent sensing functionality from compromising circularity.