Tactile Sensitivity and Capability of Soft-Solid Texture Discrimination

Abstract

The sensation and perception of food texture is regulated by tactile-dominated mechanisms and therefore, it is believed that one's capability in discriminating food textural properties could be related to one's tactile sensitivity. However, evidence to support this hypothesis is currently not available. This work aims to test this hypothesis by examining tactile sensitivity of individuals' (touch detection threshold and two-point discrimination threshold) and texture discrimination capability. A range of soft-solid food samples with controlled firmness and elastic moduli were designed for textural discrimination tests. A total of 32 healthy subjects threshold of touch detection was found to be 0.028 g for the fingertip and 0.013 g for the tongue. Similarly, the mean threshold of two-point discrimination was 1.42 mm and 0.62 mm for the fingertip and tongue, respectively. Threshold for firmness discrimination (compressing until yielding) of the gel samples was 13.3% for the fingertip and 11.1% for the tongue. However, the elasticity discrimination threshold (by gentle pressing) of the population was found to be much smaller at 2.3% and 1.2% for the fingertip and the tongue respectively. Results show that tongue is slightly more sensitive than the fingertip in discriminating food texture (P < 0.05). An expected correlation between individual's capability of texture discrimination and their tactile sensitivity was not observed. PRACTICAL APPLICATIONS Texture discrimination capability is a significant factor for food texture preference and appreciation. In order to understand texture perception, it is essential to identify the relevant factors and define characteristics that govern the processes involved. Having a meaningful and reliable texture discrimination indicator is critically important for the food industry in the development and optimization of new food products, and in particular for specific food design for individuals' with special needs, e.g., elderly, dysphagic patients, etc. With this study, we illustrate the differential threshold for soft-solid texture (firmness and elasticity) and also investigate the capabilities of tactile sensation (touch detection and two-point discrimination) and evaluate potential correlations. The results and correlations may provide information about texture sensitivity and also might provide useful information to R&D researchers. Methodologies could also be applied in general food sensory studies and also investigating relationships between sensory psychology and sensory physiology.