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

Ecaterina Stribiţcaia,Emma M Krop,Rachel Lewin,Melvin Holmes,Anwesha Sarkar

doi:10.1016/j.foodhyd.2020.105692

Abstract

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.

Highlights

Foods in general are heterogeneous composite structures with par ticles of various sizes, shapes and viscoelastic moduli embedded in complex polysaccharide and protein networks
Instrumental methods were used to quantify differences in textural complexities of layered hydrogels for the first time by incorporating a monolayer of soft beads of different sizes in the gel network and we aimed to determine whether such instrumental differences could be sensorially perceived by untrained panellists
Neither fracture stress of the hydrogels nor apparent viscosity of the hydrogel boli at orally relevant shear rate could statistically distinguish the layered hydrogels based on bead size

Summary

Introduction

Foods in general are heterogeneous composite structures with par ticles of various sizes, shapes and viscoelastic moduli embedded in complex polysaccharide and protein networks Examples of such com posite foods may range from the conventional use of freeze-dried fruit pieces in porridge and yoghurt, and starch granules in custards to the more recent usage of flavoured gelatine pearls in confectionery, pieces of cookies in ice creams and seeds/nuts inclusion in cheese, etc. Research into model and real foods with textural complexity with embedded in clusions will increase the understanding of sensory and functional re lationships during oral processing and contribute toward the two key global challenges of obesity and healthy ageing

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