Intrinsic viscosities and apparent specific volumes of amino acids and sugars. ‘Effective size’ and taste of sapid molecules

Intrinsic viscosities ([η]) and apparent specijic volumes (V   0 2 ) are compared for a number of amino acids and simple sugars and their derivatives. While the sugars and their derivatives fit within a narrow range for both parametevs ([η])=2.27–2.61 cm 3 g −1 ; V   0 2 =0.60–4.69 cm 3 g −1 ), the amino acids cover a much wider band ([η]) = 1.29–4.20 cm 3 g −1 ; V   0 2 =0.562–0.712 cm 3 g −1 ). The intrinsic viscosity value of any particular amino acid is always greater than the corresponding apparent specijc volume, and ranges (at 10 mg g −1 ) between two and seven times the value of the apparent specific volume. For the sugars and sugar derivatives, on the other hand, the intrinsic viscosities are always three to four times greater than the values of the corresponding apparent specijic volumes. When concentration is increased, all apparent specific volumes increase but they remain relatively constant if they are expressed as parachors (V   0 2 γ 1/4 ). Differences between the sugars and amino acids originate in the greater structural diversification of the latter molecules which in turn accords with their greater range of taste qualities.