Found in significant amounts in fruits and honey, fructose is the sweetest f natural sugars. Its sweetness is known to vary depending on temperature. As shown in Figure 1, the C2 ketone group of chain-sturctured D-fructose readily forms intramolecular hemiacetals with C5 and C6 hydroxy groups to form cyclic structures. Four types of D-fructose cyclic structures, namely ɑ-D-frucfranose, Β-D-fructofranose, ɑ-D-fructopyranose and Β-D-fructopyranose, are formed depending on cyclization at C5 or C6 and ɑ-type or Β-type. Five structures, including a chain structure, occur in an equilibrium in aqueous solution. Fructose is said to be sweeter at low temperature because the ratio of the sweetest ß-D-fructofranose in equilibrium is higher at low temperatures and lower at high tempertures.
We applied the dynamic light scattering method to evaluate the temperature dependence of the diffussion coefficient of an aqueous fructose solution. We used fructose obtained from Wako Pure Chemicals and added water distilled through a filter with a pore size of 0.2 µm to prepare a 40 weight % solution. We used the ELSZ-2000 for dynamic light scattering measurements. Measurement temperatures were set from 25oC to 50oC at 5oC intervals. The retention time at each set temperature was 10 minutes; measurement were performed both the heating and cooling process.
