Chem. Senses 24: 271-279,
1999
© Oxford University Press
Some Taste Molecules and their Solution Properties
Department of Food Science & Technology, University of Reading, Whiteknights, Reading RG6 6AP, UK
Correspondence to be sent to: Professor G.G. Birch, Department of Food Science & Technology, University of Reading, Whiteknights, PO Box 226, Reading RG6 6AP, UK
The solution properties of a variety of different sapid substances from all four basic
taste modalities, namely, sweet (n = 24), salty (n = 7), sour (n = 11)
and bitter (n = 2), have been investigated. Some multisapophoric molecules, i.e.
molecules exhibiting more than one taste, have also been included in the study in an attempt to
define their properties in relation to the tastes they exhibit; eight sweet–bitter and three
salty–bitter molecules were used. The density and sound velocity of their solutions in
water have been measured and their apparent volumes, apparent compressibilities and
compressibility hydration numbers calculated and compared. Apparent molar volumes (
v) and apparent specific volumes (ASV) reflect the state of hydration of the
molecules, and thus their extent of interaction with water structure. The range of ASVs reported
are 0.13–0.49 cm3/g for salty molecules, 0.55–0.68 cm3/g for sweet molecules, 0.53–0.88 cm3/g for sweet–bitter molecules
and a much wider range (0.16–0.85 cm3/g) for sour molecules. Isentropic
apparent specific compressibilities range from –2.33 x 10–5 to
–8.06 x 10–5 cm3/g.bar for salty molecules,
–3.38 x 10–7 to –2.34 x 10–5 cm3/g.bar for sweet molecules, +6.35 x 10–6 to
–2.22 x 10–5 cm3/g.bar for sweet–bitter
molecules and +6.131 x 10–6 to –2.99 x 10–5 cm3/g.bar for sour molecules. Compressibility hydration numbers
are also determinable from the measurements of isentropic compressibilities and these reflect the
number of water molecules that are disturbed by the presence of the solutes in solution. This
study also shows that it is possible to group isentropic apparent molar compressibility values by
the taste quality exhibited by the molecules in the same order as for ASV.