Engineering Starch for Sustainable Food Packaging: A Critical Review of Structural Limitations, Modification Techniques, and Emerging Active and Intelligent Applications

Conventional plastic food packaging, although cost-effective and durable, contributes significantly to greenhouse gas emissions, environmental pollution, and microplastic contamination. Starch represents a sustainable alternative due to its abundance, renewability, and biodegradability. However, native starch films exhibit several limitations, including hydrophilicity, poor moisture barrier performance, brittleness, retrogradation-induced storage instability, and the lack of intrinsic antimicrobial and antioxidant functionalities. This review examines recent advances in starch-based films, emphasizing the influence of molecular structure, granule morphology, and botanical source on functional performance. It evaluates physicochemical, enzymatic, and composite modification strategies incorporating biopolymers, nanofillers, lipids, and bioactive compounds, aimed at improving mechanical strength, barrier properties, and structural stability. Particular attention is given to starch-based materials that transition from passive barriers to active and intelligent systems, incorporating antimicrobial, antioxidant, and stimulus-responsive freshness monitoring capabilities. Furthermore, the review discusses food packaging applications and key challenges related to scale-up feasibility, cost-effectiveness, safety considerations, potential migration risks, and regulatory acceptance. Future perspectives are proposed to support the development of multifunctional, safe, and sustainable starch-based packaging systems, with an emphasis on waste valorization and life cycle assessment within circular economy frameworks.