Mechanical, rheological and structural properties of fiber-containing microgels based on whey protein and alginate

Dietary fiber (DF) - inulin (IN), bacterial cellulose nanofibers (BC), crystalline cellulose (CC) and oat fiber (OF) - were added at a concentration of 5% (2.5% for OF) to a whey protein isolate (WPI)/sodium alginate (NaAlg) dispersion. Gel microparticles (GMP) were formed by cold gelation followed by mechanical shearing. Compression stress-strain curves of bulk gels were similar for GMP-CC and GMP-OF but different from GMP-IN and GMP-BC. The soluble fiber IN did not change the aggregated matrix of the parent WPI/NaAlg gel, while other sources of DF became incorporated into the microgel matrix. Rheological tests (20 °C) revealed that GMP with added DF had a predominantly elastic behavior. Texture profile analysis suggested that GMP and GMP-IN had advantages over a commercial thickener in terms of adhesiveness and cohesiveness. GMP with added DF may find applications in foods for the elderly as texturizer and/or a carrier of fiber.