Color improvement and decolorization technologies for plant protein ingredients: Mechanisms, processing strategies, and impacts on functional and nutritional properties

Plant proteins are increasingly used in the food industry as techno-functional, nutritional, and bioactive ingredients. However, their application in many food matrices remains limited by undesirable coloration arising from endogenous pigments, phenolic compounds, and processing-induced browning products. This limitation is especially pronounced in leaf- and microalgae-derived proteins, where chlorophyll-rich fractions and chlorophyll derivatives can produce persistent green or dark hues. In seed-, cereal-, and legume-derived proteins, discoloration is commonly associated with phenolic oxidation, quinone formation, protein–phenolic interactions, and Maillard reaction products. Therefore, color management is not merely a sensory or aesthetic concern, but a critical processing factor that determines ingredient versatility, consumer acceptability, and suitability for light-colored or appearance-sensitive products. This review examines color improvement and decolorization technologies for plant protein ingredients, with emphasis on pigment chemistry, decolorization mechanisms, and consequences for protein recovery, structure, nutritional quality and functionality. Evidence from diverse plant protein sources is discussed to clarify the technological relevance, benefits, and limitations of current color-improvement and decolorization approaches. This review provides a mechanistic and practical basis for developing appearance-neutral plant protein ingredients using decolorization strategies that balance color improvement with protein integrity, techno-functional performance, processing efficiency, and sustainability.