Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Reexamination Certificate
2003-06-16
2004-06-29
Wilson, James O. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
C536S018500, C536S124000, C536S127000, C127S061000
Reexamination Certificate
active
06756490
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a novel method of preparing anhydrous crystalline maltitol.
Maltitol (&agr;(1→4)glucosylsorbitol) is a sugar alcohol generally used as a sweetening agent in low-caloric, dietary and low-cariogenic foods, such as confectionary products and chewing gums. Maltitol has a sweet taste similar to that of sugar, and the sweetening power of crystalline maltitol with high purity has a sweetness of about 85 to 95% of that of sucrose, making it sweeter than all other polyols except xylitol.
Maltitol is produced from a starch solution, which is first enzymatically hydrolyzed into maltose syrup. After purification and concentration, the maltose syrup is catalytically hydrogenated to maltitol. Following additional purification steps to remove the starting materials and the catalyst, the solution is concentrated to a syrup and then the maltitol syrup (containing more than 50% maltitol) is crystallized. The maltitol syrup used as the starting material for crystallization also contains low levels of sorbitol, maltotritol and higher hydrogenated oligosaccharides.
Maltitol in dry form is extremely hygroscopic and deliquescent. As a rule, maltitol has been considered very difficult to prepare in anhydrous crystalline form, e.g. due to its viscosity and solubility characteristics.
A process for preparing anhydrous crystals of maltitol has been described for the first time in U.S. Pat. Nos. 4,408,041 and 4,717,765 (Hayashibara Co.). In this process, an aqueous maltitol solution having a maltitol content of at least 65% (supersaturation degree of about 1.05-1.50) is subjected to crystallization at a temperature in the range of 0-95° C. The supersaturation degree and viscosity of the solution can be regulated by adding a water-soluble organic solvent, e.g. methanol, ethanol and acetone. Crystallization of the solution is started at a temperature of about 40-95° C. and in a supersaturated concentration, and the content is simultaneously cooled gradually with gentle stirring to obtain a massecuite containing anhydrous crystals of maltitol. The presence of seed crystals in an amount of 0.1-20.00% can accelerate the crystallization. The massecuite thus obtained is then separated into anhydrous crystals of maltitol and mother liquor by conventional separation methods. The method produces anhydrous crystals of maltitol, having a melting point of 146.5-147.0° C.
U.S. Pat. No. 4,846,139 (Roquette Frères) discloses a first industrial process for preparing pure maltitol. In this process, the crystallization of maltitol is carried out by cooling crystallization.
U.S. Pat. No. 5,304,388 (Ueno Seiyaku Oyo Kenkyulo Co.) discloses a method of manufacturing powdery or granular crystalline maltitol. In this method, seed crystals of maltitol (e.g. at a temperature of 105° C.) are first added to an aqueous solution of maltitol having a moisture content of 1-15% by weight (temperature e.g. 90° C.). The mixture is subjected to kneading in the presence or absence of an additive selected from the group consisting of a fat, an oil and a surface-active agent, and a shearing force is continuously applied to the kneaded mass. By applying a shearing force to the kneaded mass, powdery crystalline maltitol can be obtained continuously and at a high yield. In this process, the crystals are not separated from the mother liquor. The product is impure and does not fulfill the requirements of a high quality crystalline product.
U.S. Pat. No. 4,849,023 (Roquette Frères) discloses a method where crystalline maltitol is manufactured from a concentrated maltitol syrup with a 90% dry matter content by maintaining the maltitol syrup four hours at a temperature of 75° C., after which spontaneous nucleation starts. The crystallization vessel is then cooled to a temperature of 25° C. The crystal mass is drained by centrifugation, and the crystals are dried on a fluidized bed. A crystalline maltitol product is obtained with a yield of 63% and a purity of 99.2% (by HPLC).
In accordance with U.S. Pat. No. 5,651,829 (Roquette Frères), crystalline maltitol can be obtained from a maltitol syrup which has a dry matter content of at least 50% and exhibits a maltitol concentration greater than or equal to 92% by finely atomizing this syrup on a moving pulverulent bed of particles of crystallized maltitol at a concentration which is at least equal to that of the syrup, the bed having a temperature of between 60 and 110° C.
European Patent Application EP 0 937 733 A2 (Hayashibara) discloses a continuous method of manufacturing anhydrous crystalline maltitol, where seed crystals are added by mixing to a concentrated solution of maltitol with heating to give a seed crystal-containing massecuite, and the massecuite thus obtained is subjected to disintegration, mixing, stirring and transfer in an atmosphere in which the temperature and moisture are adjusted to cause crystallization to proceed. The last step may be carried out e.g. with hot air having a temperature between 70 and 100° C.
In the known crystallization methods described above, the crystallization of maltitol is effected, for example, by cooling, applying shearing forces or drying the massecuite. The typical disadvantages of the cooling-crystallization methods relate to the unfavorable supersaturation gradient between the crystallization mass and heat transfer surfaces. The viscosity and supersaturation are high close to the heat transfer surfaces Heat transfer coefficient is reduced and harmful nucleation is easily generated if cooling is fast. As a result, the crystal mass thus obtained is very difficult to centrifuge. The method is uneconomical, because only a small amount of maltitol is recovered in one step due to the solubility limits. In addition, crystallization rate is low at low temperatures, and crystal size distribution cannot be controlled.
As regards other sugars and sugar alcohols, WO 98/50589 (Xyrofin Oy) discloses a boiling crystallization method of recovering xylose. This reference describes a method of crystallizing xylose where a xylose-containing solution is evaporated to supersaturation at a boiling point of 40 to 80° C. of the solution, the solution is seeded, and the evaporation is continued at the boiling point of the crystallization mass, until a crystallization mass with a crystal yield of 1 to 60% and a dry solids content over 70% is obtained.
WO 92/16542 (Xyrofin Oy) discloses a process for the preparation of crystalline anhydrous lactitol by bringing an aqueous lactitol solution to supersaturation in respect of lactitol, and subjecting the solution to crystallization conditions at a temperature above 70° C., by evaporating the solution or lowering the temperature under simultaneous stirring, whereupon crystalline anhydrous lactitol is formed. A boiling crystallization method has thus been proposed as one alternative for preparing crystalline lactitol.
Boiling crystallization methods for maltitol have not been suggested in the prior art, obviously because it was not expected that the boiling crystallization could be applied to the crystallization of maltitol, due to the very poor crystallization properties of maltitol. Only crystallization-by-cooling methods have been proposed for the separation of pure maltitol crystals from an impure mother liquid.
BRIEF DESCRIPTION OF THE INVENTION
The object of the present invention is to provide a method of manufacturing anhydrous crystalline maltitol by a simple procedure and with high efficiency.
In order to achieve the above-mentioned object, there is provided, according to the present invention, a method of manufacturing anhydrous maltitol using a boiling crystallization method. The method of the invention proved feasible for producing high purity crystals from maltitol syrups having varying purity and varying oligosaccharide contents.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a method of crystallizing maltitol from a maltitol solution by supersaturating the solution in respect of maltitol and crystallizing the maltitol from the solution.
T
Eroma Olli-Pekka
Heikkilä Heikki
Nurmi Juha
Nygren Johanna
Danisco Sweeteners Oy
Henry Michael C.
Scully Scott Murphy & Presser
Wilson James O.
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