Fracture phenomena of soft gellan gum gels during compression with artificial tongues

Abstract

The objective of this study was to clarify the effects of mechanical properties of soft food gels on breakability with the human tongue. Models of nursing care foods were prepared using mixtures of high- and low-acylated-gellan gums to achieve high or low fracture deformation. Mixtures with different concentrations were set to prepare gels with high or low fracture force. Several model tongues with moduli and relative sizes-to-food similar to those of the human tongue were also prepared using transparent urethane gels. A compression test was conducted using a soft machine equipped with an artificial tongue coupled to a conventional texture analyzer to simulate fracture phenomena of soft food gels between the tongue and hard palate. The food gel and artificial tongue were both deformed, with the former being pushed into the latter. Gellan gels with higher fracture force exhibited greater force and work until the fracture observed was similar to that in a conventional test. Highly deformable gels were resistant to fracture with the softer artificial tongue as greater displacement in the combination of gel and artificial tongue was observed prior to being fractured during compression. The gels were encumbered by the surrounding soft artificial tongue. The food gels having high deformation ratio at fracture in the conventional test were difficult to fracture with the soft machine. The results suggest that fracture deformation of food gels alone is a more important factor for gel fracture during compression between the tongue and hard palate.