Tribology and rheology of bead-layered hydrogels: Influence of bead size on sensory perception

The aim of this study was to understand the influence of the size of soft beads embedded in layered hydrogels on mechanical performance as well as sensory discrimination and perception. Layered hydrogels were designed using a monolayer of calcium alginate (CaA) beads of small, medium and large size (diameter of 805, 1413 or 1725 μm, respectively) sandwiched in between layers of kappa-carrageenan (κC) gel matrix, with controls created using pure κC hydrogels and κC + sodium alginate (NaA) mixed gels. Large deformation rheology of the hydrogels followed by apparent viscosity as well as tribological properties of the hydrogel boli (after homogenising with simulated saliva) were analysed. Sensory discrimination tests (n = 113) and intensity ratings (n = 60) were conducted with untrained panellists. Bead size did not have an influence on the rheological properties of the layered hydrogels and hydrogel boli, respectively (p > 0.05). However, the lubrication behaviour of the layered hydrogel boli was influenced by bead size, with gels containing large-sized beads showing highest lubrication in both boundary and mixed regimes (p < 0.05). Although panellists were able to discriminate non-layered gels from bead-layered counterparts based on textural attributes, such as “hard”, “chewy” and “pasty”, they could not distinguish between small and large-sized bead-layered gels in contrast to the oral tribology results. The low modulus of the beads appeared to be the limiting factor to detect differences based on bead sizes in this study. Findings on instrumental characterization and consumer perception of bead-layered hydrogels can have important implications for development of novel food texture.