Integrated Valorization of Underutilized Tropical Fruit Seeds Within the Circular Bioeconomy: From Functional Ingredients to Biochar-Based Applications

Tropical fruit processing generates substantial quantities of seed-derived by-products that remain underutilized despite their potential as sources of bioactive compounds, proteins, lipids, dietary fiber, and polysaccharides. This critical narrative review evaluates their conversion into functional ingredients by integrating compositional variability, pretreatment and extraction, antinutritional-factor mitigation, structural characterization, food-system performance, storage stability, gastrointestinal behavior, safety, regulatory readiness, and scale-up feasibility. Direct evidence was distinguished from mechanistic support derived from non-target botanical matrices. An exploratory semantic clustering of 100 PubMed records published in 2024–2026 was conducted with Carrot2 to organize application-oriented themes and identify knowledge gaps; its output was interpreted as a thematic aid rather than a quantitative trend analysis. The review also examines biochar production from exhausted or non-food-grade seed biomass as a complementary cascading route, considering feedstock properties, thermochemical conditions, physicochemical quality, safety, application performance, and techno-economic constraints. The main contribution is an evidence-derived multi-stage decision framework linking ingredient validation with residual-biomass valorization. Current evidence supports promising nutritional and technological applications but remains heterogeneous and predominantly laboratory-based, with limited standardized comparisons, in vivo validation, regulatory assessment, and pilot-scale studies. Advancing these materials therefore requires application-specific, safety-oriented, and economically realistic validation within circular bioeconomy systems.