Edible Biopolymer Coatings for Postharvest Preservation in Warm‐Chain Horticultural Supply Chain: Mechanisms, Materials, Design Strategies, and Future Directions

Fresh fruit and vegetable postharvest losses reach 30%-50% between harvest and consumption, concentrated in low- and middle-income countries where warm-chain supply chains (20°C-35°C, 55%-85% relative humidity, intermittent handling) replace the refrigerated cold chains conventional technology assumes. Edible coatings from polysaccharides, proteins, and lipids offer a non-refrigeration postharvest intervention, with efficacy confirmed under controlled laboratory conditions, but commercial adoption remains marginal. This review argues that the gap between laboratory performance and field outcomes is primarily a systems-design failure, in which existing formulations optimized for stable, refrigerated conditions are not engineered to maintain function under warm-chain variability. Biopolymer materials face a three-axis trade-off, unable to simultaneously satisfy moisture barrier performance, gas exchange selectivity, and thermal-hygroscopic stability, and all three degrade predictably under warm-chain conditions through mechanisms current formulation design does not account for. Bioactive release kinetics compound this failure by depleting protection before supply chain completion, while the absence of a commodity classification framework makes the research literature noncumulative. This review makes three contributions. It provides, to the authors' knowledge, among the first integrated analyses of biopolymer coating performance failure under warm-chain conditions, distinguished by its deployment-focused approach rather than a materials-cataloging one. It formalizes this into a three-axis framework showing that composite design is physically necessary for warm-chain applications, and proposes a four-pillar warm-chain design framework comprising predictive formulation modeling, controlled-release calibration, commodity-specific coating architecture, and standardized warm-chain validation protocols. A six-phase implementation pipeline and a commodity-specific application matrix operationalize this framework into a demonstrable pathway from formulation to field deployment.