Rheology of bolus as a wet granular matter – Influence of saliva on rheology of polysaccharide gel beads

In the present work, the rheological properties of model boli were analysed based on the granular matter physics. Polysaccharide microgels mixed with artificial saliva were prepared as model boli. The storage modulus G′ of alginate gel beads increased and then decreased with increasing content of artificial saliva. Surface of alginate gel beads prepared by dripping into calcium chloride solution were wiped to remove the moisture to mimic the oral condition of the Sjögren's syndrome. G′ decreased monotonically with increasing artificial saliva beyond a certain amount of the added saliva, which is similar to the widely observed characteristic of wet granular materials. Although the analysis is limited to a model bolus at a certain stage of oral processing mimicked by instrumentally prepared microgels of uniform size and shape, it revealed some fundamental aspects highlighting the implication of a wet granular matter as a useful concept for further understanding of the bolus rheology.