From Food Waste to Phytochemicals: Green Recovery, Food‐Matrix Applications, and Metabolic‐Health Translation of Residue‐Derived Polyphenols

ABSTRACT Agri‐food residues are increasingly described as circular sources of natural antioxidants, colorants, antimicrobials, and nutraceutical ingredients, but many studies still focus mainly on total‐phenolic content or radical‐scavenging assays. This critical review reframes residue valorization as a translation pathway from food waste to chemically standardized phytochemical ingredients and then to food and health applications. This review focuses on polyphenol‐rich residues, including onion, pomegranate, and citrus peels; grape, berry, and apple pomaces; olive pomace; potato peel; mango peel; and peanut skin. It compares green recovery options such as ultrasound‐, microwave‐, enzyme‐, pulsed‐electric‐field‐, pressurized‐liquid‐, subcritical‐water‐, and natural‐deep‐eutectic‐solvent‐assisted extraction but evaluates them against food‐grade scalability, solvent safety, selectivity, sensory effects, and downstream stabilization rather than yield alone. A four‐gate framework is proposed: reproducible source chemistry, food‐grade extraction and cleanup, matrix‐specific functionality and stability, and endpoint‐specific biological evidence. Each gate is operationalized through measurable source, process, matrix, and exposure criteria, and overall readiness is determined by the lowest‐scoring gate rather than extraction performance alone. Current evidence supports the use of residue‐derived polyphenols in bakery, dairy, beverages, edible films, coatings, and active packaging, where they can improve antioxidant capacity, color, oxidation stability, microbial control, and shelf life. Health translation is more cautious: Quercetin, anthocyanins, curcuminoids, resveratrol, and polyphenol‐rich diets may influence glycemia, blood pressure, triglycerides, HDL cholesterol, inflammation, and the gut microbiota, but disease‐prevention claims require realistic dosing, bioaccessibility, metabolite exposure, and human endpoint validation. Standardization, safety, palatability, bioavailability, and regulatory claim substantiation remain decisive barriers to credible scientific evaluation and commercial translation.