Protein-Polysaccharide Interactions during the Processing of Plant Raw Materials: Techno-Functional Properties and Protein Digestibility (A Critical Review)

Background: The growing use of cereals, pulses, oilseeds, and plant-processing by-products in protein-rich foods makes protein-polysaccharide interactions a central processing issue. These interactions affect solubility, water binding, rheology, gelation, texture, storage stability, and enzyme accessibility. 

Purpose: To critically synthesize evidence on how raw-material structure, protein fractionation, and subsequent processing reshape the protein-polysaccharide matrix and determine both techno-functional properties and protein digestibility. 

Materials and Methods: A critical narrative review was conducted using PubMed, Crossref, Google Scholar, and publisher platforms. Evidence was compared by raw material, fractionation route, processing parameters, matrix composition, structural methods, and endpoints. 

Results: Total protein and dietary-fibre contents are insufficient predictors of product performance. Dry and wet fractionation yield ingredients that differ in purity, retained native matrix, hydration, and aggregation. Milling and moderate heating may improve protein accessibility by disrupting cell walls and inactivating protease inhibitors, whereas intensive heating, extrusion, and drying may generate dense aggregates and limit proteolysis. Extrusion effects are not uniform and depend on moisture, temperature, shear, formulation, and sample preparation. Native cell walls and added hydrocolloids are not equivalent because they enter the system at different structural levels. 

Conclusion: Product quality is determined by the sequence of processing operations rather than composition alone. Process design should jointly assess microstructure, protein solubility and aggregation, polysaccharide hydration, rheology, texture, storage stability, and standardized protein digestibility.

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