Interactions between food macromolecules and mucin: Relevance to oral processing and personalized nutrition, focused on xerostomia and dysphagia

Abstract

During the oral processing of foods, mixing occurs between food and saliva. The co-existence of the main food hydrocolloids with saliva components, such as mucin, leads to alterations in the food matrix. This paper is a critical assessment of data published over the last years on the phase stability of hydrocolloid – mucin systems, and on the interactions between the principal components of saliva and of soft foods. A prominent feature noticed in almost all cases is the strong impact of mucin in phase stability: In every studied system, substantial concentration and pH ranges are found where mucin aggregates otherwise stable food macromolecular systems, or reverses the aggregation of others.The origin of these phenomena is traced down to the molecular-level interactions between each macromolecule and mucin. They are discussed in terms of the nature of interactions (electrostatics, hydrogen bonds, hydrophobic interactions, steric interactions, etc) and their quantification in thermodynamic terms (enthalpic and entropic constituents of the macromolecule – mucin interactions). These phase behaviors strongly affect their flow, namely their shear and extensional rheologies. The different food hydrocolloids (caseinate, xanthan gum, guar gum, etc) are divided in three categories, based on their interaction with mucin and on the resulting rheology.Based on the differing stability patterns (which derive from different food hydrocolloid – mucin interactions, and lead to different rheological patterns), a working hypothesis can be brought forward: Food texture is based on the interplay between saliva (here mucin) and the food's hydrocolloidal components. Food macromolecule – saliva interactions and mucin's particular role on texture should be considered in view of the growing needs of vulnerable populations, especially regarding xerostomic and dysphagic conditions.