Agri-Food Byproducts as Food-Tech Material Resources: A Critical Review of Processing, Functionality, Matrix Validation, and Readiness

Agri-food byproducts are increasingly investigated as food-tech material resources, but compositional richness alone does not establish ingredient suitability. This critical narrative review evaluates plant-derived and processing residues across four representative material groups: fiber- and polysaccharide-rich powders and fractions, protein- and starch-rich materials, bioprocessed ingredients, and formulation-supporting composites. We examine how source identity, stabilization, drying, milling, fermentation, enzymatic modification, fractionation, and formulation influence hydration, interfacial behavior, gelation, rheology, texture, sensory compatibility, storage stability, and preservation-supporting performance. Evidence is interpreted across linked feedstock–processing–functionality–application–readiness gates, with separate consideration of safety, regulatory positioning, batch specifications, scale-up, techno-economic feasibility, life cycle assessment, and circularity boundaries. The practical output is a five-gate decision support and claim calibration framework that distinguishes four proposed evidence levels: Candidate, Functionality-supported, Formulation-validated, and Industry-ready potential. As a proposed non-numerical synthesis, the framework supports decision-making and claim calibration rather than ranking, certification, or regulatory approval; it identifies the evidence required before matrix-specific functional, safety, sustainability, or industry relevance claims are made.