Development of a saltiness evaluation system for solid foods using a surface salinity meter: The impact of surface salt distribution and taste bud responses.

Accurately assessing saltiness perception in solid foods is essential for the development of low-sodium foods that maintain saltiness despite possessing a lower sodium content. This study aimed to develop a practical system for evaluating human-perceived saltiness during oral processing, particularly when food was initially placed on the tongue. As a basis for system design, sensory evaluations demonstrated that higher local salt concentrations (inhomogeneous distribution) on the tongue significantly enhanced perceived saltiness intensity compared to a homogeneous distribution, despite equal total salt content. These findings suggest that the saltiness intensity is determined by the strongest response from taste buds in fungiform papillae, which act as independent taste sensors on the tongue, rather than by overall or average response. Based on this understanding, a method was developed to evaluate saltiness intensity, in which the surface salt distribution of a food sample was first transferred onto moistened filter paper. The saltiness intensity was then estimated from the maximum salt concentration on the filter paper using a surface salinity meter containing multiple salt sensors. This approach also enabled qualitative assessment of the saltiness when food was compressed against the tongue by measuring the maximum surface salinity under applied pressure. Unlike conventional saltiness sensors, this system offers a practical method for evaluating solid food saltiness. It also contributes to the development of low-sodium foods by strategically altering surface salt distribution to enhance the perception of saltiness, making it an important tool for use in the food industry.