Method of producing D-psicose crystals

1. A method of producing D-psicose crystals, the method comprising:

removing impurities from a D-psicose solution to obtain a purified D-psicose solution;

concentrating the purified D-psicose solution; and

crystallizing D-psicose from the concentrated D-psicose solution in a supersaturated state under a metastable zone in the absence of organic solvent,

wherein the concentrating of the purified D-psicose solution is performed at a temperature of about 60° C. to about 70° C.

2. The method of claim 1 , wherein the obtaining of the purified D-psicose solution includes:

passing the D-psicose solution through a column filled with decolorants to decolor the D-psicose solution;

desalting the decolored D-psicose solution by ion exchange chromatography; and

passing the desalted D-psicose solution through a column filled with ion exchange resins to which a calcium active group is attached to obtain a purified D-psicose solution.

3. The method of claim 1 , wherein the crystallizing D-psicose from the concentrated D-psicose solution comprises adding D-psicose seeds to the concentrated D-psicose solution in an amount of about 0.01% to about 1% (g/g) based on a total amount of D-psicose in the concentrated D-psicose solution.

4. The method of claim 1 , wherein the concentrated D-psicose solution used in the crystallizing is a D-psicose solution of about 70% (g/g) or more.

5. The method of claim 1 , wherein the crystallizing D-psicose from the concentrated D-psicose solution comprises monitoring a progress of crystallization in the crystallizing to maintain the concentrated D-psicose solution in a supersaturated state under a metastable zone by decreasing the temperature of the solution when a crystal growth of D-psicose stops or a concentration of the D-psicose solution does not change any more.

6. The method of claim 1 , wherein the crystallizing D-psicose from the concentrated D-psicose solution comprises monitoring crystallization progress in the crystallizing to maintain the concentrated D-psicose solution in a supersaturated state under a metastable zone by adding a D-psicose solution of a concentration lower than that of the solution when D-psicose in the solution is concentrated to a level of supersaturation or higher.

7. The method of claim 1 , wherein a supersaturated state under a metastable zone in the crystallizing is present in a range from a saturation concentration to a concentration higher than the saturation concentration by about 6% (g/g solution).