Sweet & Salty Tastes

Carmen Drahl's article on salt taste research was stimulating, particularly the section on the effects of NaCl crystal size (C&EN, June 1, page 29). Another physical aspect of human saltiness perception is that it depends on concentration. This observation may seem trite (I can hear C&EN readers chiding "Duuuuh"), but the surprise is that, at low concentrations, NaCl's saltiness is transformed into w`hat some might consider its opposite: sweetness.

For concentrations near 0.01 M, aqueous solutions of the salt are perceived by trained testers as having a sweet taste (Food Qual. Pref. 2004, 15, 83). The mechanism that underlies this reversal has not been unequivocally described, but a plausible explanation is that it arises from the interaction between the hydration shell of a sodium ion and the sweet receptor (T1R2-T1R3).

Dale E. Vitale
Union, N.J.