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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. [Display omitted] • Polysaccharide microgels were prepared and mixed with artificial saliva. • Elastic modulus of a microgel was measured using Hertz theory. • Storage modulus of microgels increased and decreased with increasing saliva. • Smaller alginate microgels showed a peak modulus at a lower saliva content. [ABSTRACT FROM AUTHOR]

This study investigates the nanomechanical properties of different oil bodies (OBs), including soybean, peanut, sesame, and rapeseed, coated with sodium alginate (ALG), and the interaction between ALG-coated OBs using atomic force microscopy (AFM). Hooke's law, Reissner theory, and the Membrane model were respectively applied to analyze the nanomechanical properties of the linear and non-linear mechanics of the ALG-coated OBs. It was found that stiffness K b and modulus E R from the linear deformation of ALG-coated OBs increased with the increase of the ALG layer thickness, while modulus E m from the non-linear deformation was larger than E R and correlated with the compression degree of the ALG layer. The interaction between pure OBs depended on the OB type. Electrostatic interaction which is related to the surface ζ -potential of the OBs occurs at a relatively long interaction distance, while at a relatively short distance, interfacial deformation of OBs occurs and the interaction force is affected by the structure and mechanics of OB interfacial membrane. After coating by ALGs, the electrostatic repulsion occurred from a longer distance than that between pure OBs, and both electrostatic repulsion and steric hindrance exist for a long interaction distance as the ALG-coated OBs continued to approach each other. ALG coating can also weaken the electrostatic screening effect of salt ions, avoiding aggregation of OBs and thus improving their stability. The present work demonstrates the feasibility of using AFM to study the mechanical properties and interaction of OB droplets at the molecular level, and reveals the mechanism of the influence of polysaccharide macromolecules on the stability of OB emulsions from the microscopic scale. [Display omitted] • Stiffness K b and modulus E R of ALG-coated OBs from linear deformation increased with increase of ALG layer thickness. • Modulus E m from non-linear deformation was larger than E R and decreased with increase of compressed ALG-layer thickness. • Electrostatic repulsion and steric hindrance occurred and existed for a long interaction distance between ALG-coated OBs. • Reveal mechanism of ALG stabilizing OBs at molecular level, and correlate it with the macroscale results. [ABSTRACT FROM AUTHOR]