(1990) by employing intensity ratings, rather than frequency counts of qualitative reports. We extended the approach of Hettinger et al. Whether all metallic tastes are olfactory in nature remains an open question. Metallic taste has also been reported in response to the nonvolatile intensive sweetener, acesulfame-K ( Schiffman et al., 1985), further supporting the possibility of a gustatory rather than olfactory origin of some metallic taste reports. The possibility of a metallic taste or tactile sensation that is different for copper as opposed to iron salts is examined in this report. Both of these stimuli (a clean penny and FeSO 4 solutions) have been suggested as reference standards in applied sensory training of descriptive analysis panels. Anecdotal reports from applied sensory evaluation suggest that the effect of placing a copper penny in the mouth is a distinct tactile or taste (oral) sensation in contrast to the effect of rinsing with FeSO 4 solutions which is thought to be a retronasal smell (G. However, this pattern may not occur for other salts. (1990) implies a retronasal smell origin of the apparent metallic taste from FeSO 4. The reduction in metallic reports found by Hettinger et al. Murphy and Cain (1980) showed that nasal occlusion effectively eliminates the odor component of citral solutions placed in the mouth and thus nasal occlusion is generally taken as a method to eliminate stimulation from retronasal smells (see also Mozell et al., 1969). Frequency of reports of metallic sensations from ferrous sulfate solutions in the mouth decreased when the external nares were occluded. The nature of metallic taste was examined by Hettinger et al. For divalent salts such as calcium and magnesium, one adjective used to describe these compounds is ‘metallic ‘ ( Lawless et al., 2003). Metallic sensations are also reported from anodal electrical stimulation of the tongue along with sourness and salty tastes ( Frank et al., 1986 Frank and Smith, 1991). Grushka (1987) found metallic taste reports among a sample of BMS patients to be second only to bitterness in terms of phantom qualities reported (27% metallic, 33% bitter and 10% reporting a combination of bitter and metallic). Metallic taste is reported in burning mouth syndrome (BMS). Metallic tastes arise from contact with metal food packaging ( Zacharias and Tuorila, 1979) and processing equipment ( Hunzinger et al., 1929 Bodyfelt et al., 1988). Development of off-flavors presents a challenge to food scientists who attempt to fortify foods with iron compounds ( Hurrell, 2002). Metallic taste or flavor is commonly reported as a defect in many foods such as oils, cereal products, dairy foods and beer ( Borocz-Szabo, 1980). Metallic taste has occasionally been proposed as a basic taste, primary taste or an additional legitimate taste category, outside the widely accepted system of four (or five) basic tastes (see Bartoshuk, 1978). However, metallic taste reports may arise from different mechanisms with copper and zinc salts.įerrous sulfate, lipid oxidation, metallic taste, retronasal smell Introduction These results confirm that metallic taste reports following oral stimulation with FeSO 4 are likely due to development of a retronasal smell, possibly following a lipid oxidation reaction in the mouth. A discrimination test demonstrated that the headspace over solutions of FeSO 4 was not different from water, although some subjects could discriminate FeSO 4 solutions from water in the mouth when the nose was occluded, perhaps by tactile or astringent cues. A discrimination test based on weak but equi-intense levels of FeSO 4 and CuSO 4 showed that FeSO 4 could be discriminated from water with the nose open but not when occluded, but that discrimination of CuSO 4 from water was not impaired by nasal occlusion. No such reduction was seen for CuSO 4 or ZnSO 4, which were more bitter and astringent, respectively, and less metallic. Two studies showed that the metallic sensation reports following oral stimulation with solutions of FeSO 4 were reduced to baseline when the nose was occluded.
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METAL TASTE IN MOUTH SERIES
A series of experiments investigated the nature of metallic taste reports and whether they can be attributed to the development of a retronasal smell.