Conventional and Emerging Protein Ingredients in Farinaceous Products: Amino Acid Quality, Digestibility, Biological Value, and Functional Performance

The increasing demand for protein-enriched foods has renewed interest in farinaceous products as widely consumed and technologically adaptable matrices for nutritional improvement. However, protein enrichment cannot be evaluated solely by increases in crude protein content, as nutritional value depends on essential amino acid (EAA) balance, digestibility, biological quality, technofunctional performance, bioactive potential, and interactions within the food matrix. This review critically examines the incorporation of conventional and emerging protein ingredients from animal, plant, insect, microalgal, and macroalgal sources into farinaceous systems, including flours, powders, concentrates, isolates, and hydrolysates. This review synthesizes current evidence through comparative analyses of protein content, EAA profiles, digestibility, protein digestibility-corrected amino acid score (PDCAAS), digestible indispensable amino acid score (DIAAS), technological functionality, and bioactive properties. Particular attention is given to formulation and processing strategies that improve protein quality while preserving dough or batter performance and consumer-relevant attributes. In general, the literature indicates that effective protein enrichment requires an integrated approach that combines amino acid complementation, digestibility enhancement, reduction of antinutritional constraints, technological compatibility, and sensory feasibility. This review highlights the need to move beyond protein quantity as the primary benchmark and toward multidimensional quality frameworks for designing nutritionally improved, functional, and acceptable farinaceous foods.