Taste qualities of divalent salts
J. Lim*, H.T. Lawless
Cornell University, USA
The increasingly common practice of mineral fortification, including calcium, iron, magnesium and zinc, has drawn attention to the taste quality of divalent salts. In most studies, tastes of metallic compounds were profiled by four basic tastes, sometimes with a few more words such as astringent and metallic. However, it was not proved that those stimuli could be phenomenologically described in terms of primaries. The aim of this research was to explore the taste sensations associated with nine divalent salts by measuring the similarity of stimuli rather than using attribute ratings.
Nineteen subjects attended a two-part experiment: intensity matching, and judgments of similarity. In the first part, subjects were asked to rate the overall intensity of the nine test (calcium, iron, magnesium, and zinc salts) and five standard (citric acid, sodium chloride, sucrose, quinine, and alum) stimuli at various dilutions using an unstructured line scale. The concentrations of stimuli, which yielded geometric means between 4.6 and 5.6 were considered to be approximately equal and were used for the next experiment. For the second part of the experiment, a multidimensional similarity scaling (MDS) study was performed with all fifteen stimuli. The perceptual similarity map of divalent salts was obtained using a sorting task with and without nose plugs. Ferrous chloride, sulfate, and gluconate fell near one another and were located a little farther away from other stimuli, which possibly defines a metallic taste axis. Zinc chloride and sulfate fell close to alum and thus tasted most astringent. Ferrous salts appeared to shift toward alum and citric acid compared to the nose open condition. The results showed that the taste range of divalent salts extended beyond the four primary tastes. Furthermore, this study confirmed that retronasal cues are the main key for perceiving ferrous salts containing minor elements of astringency and sourness qualities.
Supported by NIH RO1-DC-006223
Key words: divalent salts, multidimensional scaling, sorting task, metallic taste