Nonlinear friction dynamics in the cognitive process of food textures: Thickness of polysaccharide solution

Abstract

"Thickness" is one of the descriptors of texture in liquid and semisolid foods. In this study, friction in thickener aqueous solutions was evaluated, using a biomimetic friction evaluation system, to show the correlation between friction data and sensory thickness and the recognition mechanism of this sensation during the process of eating. This system can measure friction forces under sinusoidal movement on fractal agar gel, which mimics the morphology and physical properties of the tongue. We found that an increase in the viscosity of the thickener aqueous solution was responsible for both the sensory score of thickness and the asymmetric profile of the friction coefficient in a reciprocating motion. In the case of low viscosity liquids such as water, many of the subjects did not feel thickness, and the friction profile "stable pattern I," that is, a static friction coefficient larger than kinetic friction and a similar profile in the outward and inward processes were observed. However, in the case of solutions containing 3 or 5 wt% of food thickener, the friction profile "unstable pattern I," that is, different friction behaviors in the outward and inward processes, was observed, and many of the subjects experienced strong thickness. In addition, the static friction coefficient at the first cycle was small, and the changes of friction coefficient by the reciprocating motion being repeated was large. These friction phenomena can occur in the mouth and are expected to induce sensory thickness.

Nonlinear Friction Dynamics of Oil-in-Water and Water-in-Oil Emulsions on Hydrogel Surfaces

“…Although the thickness of the upper agar gel does not significantly affect the friction force or profile, the normalized delay time (δ), which is the normalized time lag in the friction force response to the contact probe’s movement, increases linearly with the thickness of the gel . In addition, we showed the correlation between the friction data of thickener aqueous solutions and the sensory thickness and the recognition mechanism of this sensation during the process of eating, using a biomimetic friction evaluation system . “Thickness” is one of the descriptors of the texture in liquid and semisolid foods.…”

“…The friction force between two agar gel substrates in the emulsions was assessed using a sinusoidal motion friction evaluation system (Figure ). The sinusoidal motion was achieved through the Scotch yoke mechanism. − The adopted evaluation method is described elsewhere . The sliding velocity ( V ) under the sinusoidal movement was calculated using the stroke length ( A ), angular velocity (ω), and time ( T ), based on eq In the present investigation, the friction conditions were as follows: A = ±14.5 mm; ω = 2.1 rad s –1 ; sampling interval = 1 ms; and normal force ( W ) = 0.39 N. In addition, the maximum sliding velocity ( V max ) and the average sliding velocity ( V ave ) for the angular velocity were 30 and 20 mm s –1 (2.1 rad s –1 ), respectively.…”

“…Traditional systems are not suitable for mimicking the oral environment; therefore, we designed a friction evaluation system that combined a sinusoidal motion device with fractal agar gel substrates. − The developed system effectively mimicked the oral environment during eating. To evaluate the nonlinear mechanical response on a soft material surface, we created a unique device that can be used to evaluate friction under sinusoidal motion.…”

“…11 In addition, we showed the correlation between the friction data of thickener aqueous solutions and the sensory thickness and the recognition mechanism of this sensation during the process of eating, using a biomimetic friction evaluation system. 10 "Thickness" is one of the descriptors of the texture in liquid and semisolid foods. An increase in the viscosity of the thickener aqueous solution is responsible for both the sensory score of thickness and the asymmetric friction profile during a reciprocating motion.…”

Friction dynamics of moisturized human skin under non‐linear motion

“…We have found that the characteristic friction stimulus with high acceleration is one of the cues to distinguish water from thickener aqueous solution [9, 10]. We also evaluated the friction dynamics on fractal agar gels, which mimic the shape and wettability of the tongue surface, and found that the friction profiles vary with the surface shape, vertical load, friction velocity and substance [15–18]. Asanuma et al found that the cosmetic sponge feels highly slippery when the friction force is low [19].…”