TASTES, STRUCTURE AND SOLUTION PROPERTIES OF D-GLUCONO-1,5-LACTONE

D-glucono-1,5-lactone differs from D-glucopyranose only in that it has a C=O group instead of CHOH group at carbon atom number one. The mole cule therefore possesses an intact 3,4 alpha-glycol group and is' swee t. However, it autohydrolyses in water solution at room temperature, f orming D-gluconic acid and D-glucono-1,4-lactone. As the solution pH f alls it becomes sweet-sour and eventually almost completely-sour as th e generated hydronium ions dominate both the solution properties and t he taste perceptions elicited. It is shown that the ratio of generated hydronium ions to unchanged lactone accords with anticipated taste qu ality during the first 28 min of autohydrolysis. Changes in both appar ent specific volume and apparent isentropic compressibility illustrate increasing solute-solvent interaction and increasing disturbance of w ater structure during the course of autohydrolysis. These changes are consistent with the concurrent sweet to sour change, but do not explai n the weak bitterness which also accompanies them.