Tribology of o/w Emulsions Under Mouth-like Conditions: Determinants of Friction

Fat-perception is thought to be related to a complex interplay between fat-associated flavor release and mouth-feel. Friction sensed between the tongue and the palate seems to play a prominent role: in previous work, we have shown that emulsions that are more sensitive toward coalescence give rise t...

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Bibliographic Details
Published in:Food biophysics 2007-12, Vol.2 (4), p.158-171
Main Authors: Dresselhuis, Diane M, Klok, H. Jan, Stuart, Martien A. Cohen, de Vries, Renko J, van Aken, George A, de Hoog, Els H. A
Format: Article
Language:English
Subjects:
adhesion
behavior
Biophysics
boundary lubrication
chocolate
Coalescence
Emulsions
flocculation
Food science
Friction
in-water emulsions
lubrication mechanism
Oils & fats
Oral mucosa
perception
protein adsorption
Proteins
saliva
Sensory
surface modification
Tribology
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Summary:Fat-perception is thought to be related to a complex interplay between fat-associated flavor release and mouth-feel. Friction sensed between the tongue and the palate seems to play a prominent role: in previous work, we have shown that emulsions that are more sensitive toward coalescence give rise to a lowering of the orally perceived and experimentally measured friction and, probably as a consequence, to an enhanced fat-perception. In this paper, we study in detail the factors determining friction of protein-stabilized emulsions using a novel mouth-mimicking tribometer and model surfaces consisting of PDMS modified in various ways (hydrophobicity, deformability, roughness). We show that unlike in many technological applications where lubrication is essentially hydrodynamic, for physiologically relevant loads, the modified PDMS is boundary and/or mixed lubricated, which is like in-mouth lubrication. We find that an increased sensitivity of the emulsions toward coalescence results in a lower friction, confirming previous results obtained with pig's tongue. Surface-induced coalescence (or spreading of emulsion droplets) seems to be very important in this, surface hydrophobicity being the dominant trigger. Viscosity of the dispersed phase does not have such a strong influence on both the measured friction and the oral perceived friction. We do find a strong influence of the presence of bulk proteins and saliva on friction. Finally, hardly any dependence of measured friction on fat content of the emulsion was observed, indicating that only a small amount of fat is needed to alter the friction.
ISSN:1557-1858
1557-1866
DOI:10.1007/s11483-007-9040-9