Compression Test of Soft Food Gels Using a Soft Machine with an Artificial Tongue

Abstract

Care food is increasingly required in the advanced-aged society. Mechanical properties of such foods must be modified such that the foods are easily broken by the tongue without chewing. When foods are compressed between the tongue and the hard palate, the tongue deforms considerably, and only soft foods are broken. To simulate tongue compression of soft foods, artificial tongues with stiffness similar to that of the human tongue were created using clear soft materials. Model soft gels were prepared using gellan gums. A piece of gel on an artificial tongue was compressed using a texture analyzer. The deformation profile during the compression test was obtained using a video capture system. The soft machine equipped a soft artificial tongue sometimes fractured food gels unlike hard machine, which always fracture gels. The fracture properties measured using the soft machine were better than those obtained from a conventional test between hard plates to mimic natural oral processing in humans. The fracture force on foods measured using this soft machine may prove useful for the evaluation of food texture that can be mashed using the tongue.

Keywords: artificial tongue; care food; compression test; fracture; gellan gum gels; soft machine; texture.

Figure 1

Typical force–deformation curve of a gellan gel (a) and setting for compression test of soft foods between an artificial tongue and plate (b,c). (b) Whole setup and (c) enlarged view around the sample. A food gel (φ20 × 10 mm) on a transparent artificial tongue (50 × 50 × 10 mm) was placed on a glass plate of a TA.XTplus Texture Analyser. Upper plate connected to a load cell was moved downward at a constant speed, and sample deformation was observed from the bottom and/or from the right side by video cameras during the compression test.

Figure 2

Apparent modulus of urethane gel for artificial tongue. Error bars represent standard errors of 2–7 samples.

Figure 3

Examples of compression curves of food gel (BC20) on artificial tongues.

Figure 4

Examples of a food gel on soft material (i.e. as artificial tongue) observed from the side and bottom. Compression process of a BC gel specimen on (a) H15, (b) H7, and (c) H0 artificial tongue. Compression distance from the first contact to the food gel is shown over each snapshot. “Bottom” represents the moment that compression was stopped due to the limit force, “initial position” is the moment that the probe returned to 0 mm height, and “end” indicates the test completion. Black bars are 10 mm as original height of food and artificial tongue gels in the side views, and yellow bars are 20 mm as original diameter of food gels in the bottom views.