Press "Enter" to skip to content


Sweetness is illustrated by this icon for taste sensations that are honey flavoured.

Any flavour or gustatory perception that could be vaguely described as something like tasting honey is called a sweet sensation. We use words like yummy, sugary, umami, caramelly, savory, candied, spicy, brothy, glazed, meaty, syrupy etc. to describe these flavours. We can make binary descriptions of sweet sensations by comparing them with other sensations, and historically the great pioneers of chemistry almost killed themselves by direct contact with their discoveries. But now testing supersedes tasting, so consider an experiment: Dissolve many similar test particles in water and pass a beam of polarized light through the solution. Check to see if the axis of polarization varies. If the angle does not change, then say that the particle is not sweet and write \delta_{\mathit{S}}=0. If the axis is rotated clockwise, then the particle is a dextrorotary isomer like most naturally occurring sugars. So say that the particle is sugary, and express this mathematically as \delta_{\mathit{S}}=+1. If the axis is rotated counterclockwise, then the particle is a levorotary isomer like most naturally occurring amino acids. So call the sensation savory and write \delta_{\mathit{S}}=-1. The number \delta_{\mathit{S}} is called the sweetness. It may, for example, be perceived directly in the flavour difference between spearmint leaves and caraway seeds. These relations can be mathematically stated as

\delta_{\mathit{S}} \equiv \begin{cases} +1 &{\text{if a sweet sensation is sugary }} \\ \; \; 0 &{\text{if a  sensation is not sweet}} \\ -1 &{\text{if a sweet sensation is savory }} \end{cases}

Reference Constant for Sweetness

The numerical constant associated with tasting a lemon has not yet been determined.