Oral sensations from iron and copper sulfate

In previous work, retronasal smell was an important cue for perceiving metallic sensations from ferrous sulfate (FeSO 4). The purpose of this study was to examine whether FeSO 4 produced oral sensations as well as retronasal cues and whether astringency contributed to the oral sensations. In the first study, discrimination of FeSO 4 from water was confirmed at concentrations at or above 5 mM without retronasal flow. A second study examined whether FeSO 4 and CuSO 4 could be detected on a non-gustatory region by tactile sensations. Astringency was perceived when the copper sulfate solution was applied to non-gustatory surfaces between the gum and the upper lip with or without retronasal cues. However, rated astringency for FeSO 4 was less than that for CuSO 4, and not significantly different from water. Other gustatory or tactile sensations from iron salts may contribute to their oral sensations and the possibility remains that at least one part of metallic sensation may be a metallic taste.