Method for producing allulose crystals
Allulose crystals are efficiently produced from an allulose syrup using seed crystals.
1. A method for producing allulose crystals, wherein the method comprises:
a) cooling and agitating a first admixture containing a first portion of allulose syrup and first allulose crystals and initiating crystallization of allulose dissolved in the first portion of allulose syrup, thereby forming a first massecuite comprising allulose crystals and a first mother liquor containing residual dissolved allulose, the cooling and agitating being continued until a first preselected target yield of allulose crystals is achieved;
b) separating the first massecuite into a first portion and a second portion;
c) combining a second portion of allulose syrup with the second portion of the first massecuite to form a second admixture; and
d) cooling and agitating the second admixture and initiating crystallization of allulose dissolved in the second portion of allulose syrup, thereby forming a second massecuite comprising allulose crystals and a second mother liquor containing residual dissolved allulose, the cooling and agitating being continued until a second preselected target yield of allulose crystals is achieved;
wherein the crystallization is performed in a continuous manner involving stages selected from a plurality of stages.
2. The method of claim 1 , wherein the first admixture is obtained by combining the first portion of allulose syrup and the first allulose crystals being dry allulose crystals.
3. The method of claim 1 , wherein the first admixture is obtained by combining the first portion of allulose syrup and the first allulose crystals being a heel containing allulose crystals and a third mother liquor.
4. The method of claim 1 , wherein the first admixture and second admixture are agitated in steps a) and d) respectively using an agitator having a tip speed of 0.02 to 2 m/sec.
5. The method of claim 1 , wherein step a) additionally comprises, following initiation of crystallization of allulose dissolved in the first portion of allulose syrup, combining at least one additional portion of allulose syrup with the first massecuite before the subsequent cooling and agitating step.
6. The method of claim 1 , wherein the cooling in step a) involves lowering the temperature of the first admixture from an initial temperature range to a second temperature range and holding the second temperature range for a period of time.
7. The method of claim 1 , wherein the cooling in step d) involves lowering the temperature of the second admixture from an initial temperature range to a second temperature range and holding the second temperature range for a period of time.
8. The method of claim 1 , wherein the first or the second portion of the allulose syrup has a dry solids content of 70% to 95% by weight.
9. The method of claim 1 , wherein the first or the second portion of the allulose syrup has an allulose purity of at least 70%, defined as the percent by weight of the allulose in the syrup, based on the total weight of dry solids in the syrup.
10. The method of claim 1 , further comprising an additional step of separating allulose crystals in the first portion of the first massecuite from the first mother liquor in the first portion of the first massecuite.
11. The method of claim 10 , wherein the separating is carried out at least in part by one or more physical separation methods selected from the group consisting of centrifugation, filtration, decantation, membrane separation, and combinations of distinct separation methods thereof.
12. The method of claim 10 , wherein allulose crystals in the first portion of the first massecuite separated from the first mother liquor are subjected to i) washing with at least one of water, an organic solvent, a blend of organic solvents, a blend of water and organic solvent(s) or an aqueous solution containing at least one carbohydrate; ii) drying; or a combination thereof.