Off-flavor formation in legume protein ingredients: Linking molecular origins, processing-induced transformations,...

The growing demand for sustainable protein sources has accelerated the integration of legume proteins into plant-based foods; however, their widespread acceptance remains limited by undesirable off-flavors, which are characteristically described as beany, grassy, earthy, bitter, and astringent. These sensory defects result from complex interactions among intrinsic seed composition, enzymatic and non-enzymatic reactions, processing conditions, and flavor perception influenced by the food matrix. This review offers a comprehensive overview of the molecular origins, processing-induced transformations, and mitigation strategies related to off-flavor formation in legume protein ingredients. Specific attention is given to the role of lipid oxidation pathways, endogenous enzymes such as lipoxygenase, secondary metabolites, and thermal reactions in the development of volatile and non-volatile flavor compounds. The effects of extraction methods, thermal and non-thermal processing, fermentation, and storage on flavor development are critically examined, alongside the influence of matrix interactions, texture, and oral perception on sensory attributes. Various mitigation strategies, including breeding techniques, enzyme management, fermentation, physical and chemical treatments, and formulation strategies, are evaluated in terms of their effectiveness, functionality, and suitability for industrial application. Additionally, this review identifies significant knowledge gaps regarding analytical methodologies, structure-flavor relationships, scalability, and consumer acceptance. Overall, this review emphasizes that enhancing the sensory quality of legume protein systems necessitates multidisciplinary and consumer-centered approaches that integrate food chemistry, processing technologies, sensory science, and matrix engineering.