The sense of smell: contributions of orthonasal and retronasal perception applied to metallic flavor of drinking water

The human senses are important assessment tools that assist the water industry with effective water quality and water security monitoring. Flavor perception is the combination of taste and odor; odor perception is a combination of orthonasal and retronasal perception. Orthonasal perception is associated with “the sniff” and describes the entry of odor molecules though the nostrils to the nasal cavity followed by interaction with odor receptor neurons. Retronasal perception describes the mechanism in which odor molecules present in the mouth are transported to the back of the nasopharynx and then to the odor receptor neurons. Although both pathways bring the odor molecules to the olfactory epithelium where they are perceived and processed by the brain, the retronasal route is more important for humans in terms of detecting ingested odors. For copper (II), the metallic flavour is a combination of a weak bitter taste and a strong metallic odor that is produced as a biochemical reaction in the mouth. Copper (II) in the presence of oxygen causes lipid oxidation of arachidonic, linoleic, and oleic acids in the mouth. A more thorough understanding of the sense of smell will greatly aid the water industry in its quest to produce a palatable product.