Abstract
Extensional and shear viscosities were studied for mixtures comprising artificial saliva and okra mucilage, the latter acting as a model thick-liquid food. These experiments aimed to obtain information on the flow-behavior information of the systems, underpinning the texture sensation of foods as perceived by dysphagic and xerostomic populations. Mixing okra mucilage with artificial saliva dramatically increases the shear viscosity of artificial saliva throughout the studied ranges of concentrations and deformation rates. Particle tracking does not suggest direct interactions between the components of artificial saliva and of okra mucilage. The rheology of the okra polymer (OP)–artificial saliva (AS) mixture is dominated by its extensional viscosity: Trouton ratios are in the order of tens to hundreds, while they decrease with increasing okra-mucilage concentration; this highlighs the dominance of the extensional rheology and the increasing importance of the shear mechanics with increasing okra content. The relaxation times and extensional moduli are also reported for the systems under study. Extensional and shear flows are of equal importance concerning the elastic behavior.
Highlights
In the oral cavity, saliva, produced by the salivary glands, aids mastication by means of helping the transportation of food, while it provides the necessary lubrication between the hard and soft tooth tissues
Commercial artificial saliva was mixed with an equal volume of buffers containing different amounts of aqueous okra polymer (OP) solution, were studied as to provide an impression of the fate of liquid food in the oral cavity in the presence of salivary substitutes
Increase in okra mucilage up to a final content of 0.25% results in viscosity increase (0.01 Pa s at 1000 s−1). This is in line with what is expected from a polymer network consisting of non-interacting units
Summary
Saliva, produced by the salivary glands, aids mastication by means of helping the transportation of food, while it provides the necessary lubrication between the hard and soft tooth tissues. Saliva has a number of essential functions in food oral processing.[1] Changes in viscosity, lubrication and friction, formation of aggregates and precipitates, enzymatic breakdown, destabilization of colloidal systems, and/or release of flavor compounds, will all contribute towards overall food perception.[2,3] Salivary pH can range from 5.3 to 7.8, with a daily flow in healthy individuals between approximately 1 and 1.5 L.4 It consists of about 99.5% water and 0.5% solids, its main components are the mucins.[5] Chemical composition of natural saliva is very complex and is influenced by a number of factors such as age, health status, or diet.[4] There are many components of real saliva that serve various complex biological processes, it is difficult to produce artificial saliva that fully matches the composition of natural saliva
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