Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
  • C08B37/00—Preparation of polysaccharides not provided for in groups C08B1/00 - C08B35/00; Derivatives thereof

Definitions

• This invention relates to a process for the crystallization of glucose, fructose, or a mixture of the two, from a solution of mixed sugar containing glucose and fructose.
• the invention relates to a process for the crystallisation of glucose, fructose, or a mixture of the two, employing as the crystallization medium, specific combination system, i.e., combination of a liquid polyhydric alcohol and liquid monohydric alcohol.
• US. Patent No. 2,357,838 discloses a process wherein a mixture of concentrated syrup of invert sugar and ethanol of at least 90% concentration is subjected to high velocity agitation of at least 200 r.p.m. to crystallize glucose, and the mother liquor thereof is concentrated to distill oif the ethanol and water content, followed by addition of fresh ethanol to the system and similar high velocity agitation, thereby crystallizing fructose within a very short time.
• sucrose is not completely inverted, according to the above-described process only low purity fructose syrup is obtained as admitted in the specification of such US. patent.
• French Pat. No. 1,563,168 teaches a process which comprises concentrating invert sugar in vacuum, dissolving the same in anhydrous methanol or monomethylether of ethylene glycol, adding thereto a crystal mother of glucose or fructose to successively crystallize glucose and fructose, or adding to the system a mixed crystal mother of glucose and fructose to crystallize a mixture of the two.
• This process may be advantageously carried out in that the crystalline glucose, fructose, or mixture of the two can be separated from mixed sugar solution by a simple crystallization procedure, but the quantity of crystallized sugar per single crystallization operation is generally low. Consequently, in order to raise the ultimate yield of crystalline sugar from the starting material, the crystallizing operation must be repeated many times.
• the process requires that the water content of the supersaturated 3,704,168 Patented Nov. 28, 1972 solution during the crystallization of fructose should be kept 1% or less.
• This requirement invites such inconveniences as, at the time of crystallization of fructose from the mother liquor from which glucose has been crystallized, a special water-eliminating device is required for removing the water content of the crystallization medium, and at the time of crystallizing sugars from a mother liquor, the mother liquor must invariably be concentrated.
• a process for crystallizing glucose, fructose, or a mixture of the two, from mixed sugar solution containing glucose and fructose is provided, which is characterized in that the crystallization of the sugars is performed in the presence of a combination medium of a liquid polyhydric alcohol and liquid monohydric alcohol, employed as the crystallization medium.
• aqueous solution such as invert sugar, isomerized sugar (mixed sugar obtained by isomerization of glucose), honey, etc.
• Those industrially available mixed sugars normally contain impurities other than the specified sugars, for example, other sugars, amino acids, organic acids, oxidized derivatives of sugars, inorganic matters, etc. Presence of such impurities is not particularly detrimental to the subject process.
• some of the mixed sugars may be specified as follows:
• such mixed sugar containing glucose and fructose is used in the form of a supersaturated solution in the mixed solvent of liquid polyhydric alcohol and liquid monohydric alcohol.
• liquid polyhydric alcohol dior tri-hydric aliphatic alcohols such as glycerin; glycerin monoalkylethers; or alkylene glycols or polyalkylene glycols of the general formula,
• R is an alkylene group of preferably 24 carbons
• n is an integer not less than 1, preferably 1-4, including, for example, propylene glycol, ethylene glycol, diethylene glycol, and triethylene glycol; can be used.
• Particularly preferred polyhydric alcohols for the invention are, by the order of their importance, propylene glycol, glycerin, and ethylene glycol.
• the type of the liquid monohydric alcohol is not criti cal, but normally those which have the boiling point at atmospheric pressure of not higher than 200 C. are preferred.
• monohydric alcohols aliphatic mono hydric alcohols represented by the formula R OH (in which R is an alkyl group), such as methanol, ethanol, propanol, etc.; and monoor poly-alkylene glycol monoalkylethers represented by the formula R"O(RO)nI-I (in which R" is an alkyl group, and R is an alkylene group), such as ethylene glycol monoethylether, diethylene glycol monomethylether, etc. can be used.
• Monohydric alcohols which assist easier crystallization operation and are therefore preferred, are those expressed by the general formula,
• n is an integer of 1 to 5, for example, methyl alcohol, ethyl alcohol, propyl alcohol, butanol, and amyl alcohol.
• denatured alcohols such as methanol-de natured ethanol, ethyl acetate-denatured ethanol, isopropanol-denatured ethanol, benzole-denatured ethanol, methyl ethyl ketone-denatured ethanol, and the like which have been known, are usable as the liquid monohydric alcohol.
• Particularly preferred combinations of the crystallization media for the invention are ethanol with propylene glycol or glycerin.
• the crystalline glucose, fructose, or mixed crystals thereof using either of the above combination media can be advantageously used for foods, quite differently from those obtained with methanol as the crystallization medium.
• the quantitative ratio of the mixed alcohol solvent to the mixed sugar varies, depending on such factors as the ratio of the polyhydric alcohol to monohydric alcohol in the mixed solvent, temperature conditions of the dissolving and crystallizing operations, and type of the sugar to be crystallized. Generally speaking, however, it is preferred to make the amount of mixed alcohol solvent at the crystallizing time 0.1-20 times by weight of the sugar. With fructose, that ranging from 0.1- times by weight is preferred, while 0.1-20 times by weight is suitable for crystallization of glucose. When a crystalline mixture of the two is desired, the suitable amount of mixed solvent ranges from 0.1 to 10 times by weight of the sugar. A particularly preferred ratio ranges from 0.3 to 2 times by weight of the sugar in any case.
• the quantity of polyhydric alcohol in the mixed alcohol solvent varies considerably, depending on the ratio of the entire solvent to sugar. That is, the quantity of polyhydric alcohol can be varied over a wide range without detrimental effect on the subject process.
• the polyhydric alcohol may occupy 180% by volume of the total mixed alcohol solvent.
• the supersaturated mixed sugar solution used in the invention may contain water to such an extent as will not interfere with crystallization of sugars, for example, not more than by weight based on the weight of the mixed sugar and not more than 5% by weight based on the weight of the entire solution.
• water content of the supersaturated mixed sugar solution is reduced to below 1.5% by weight, the mode of selective crystallization of sugar becomes unstable and controlling of the sugars crystallization rate within the predetermined range becomes difficult.
• the supersaturated mixed sugar solution preferably contains 1.5 to 5 wt. percent, of Water at the time of crystallization.
• the mixed sugar containing glucose and fructose is an aqueous solution
• This mode of practice is advantageous in that the water can be removed from the starting aqueous solution of mixed sugar, without deterioration of the sugars.
• the amount of liquid polyhydric alcohol to be added to the solution or syrup of mixed sugar may be all or a part of the polyhydric alcohol required for the crystallization of sugars. It is normally preferred to use at least 10 wt. percent of polyhydric alcohol to the starting mixed sugar.
• concentration temperature is variable depending on time, while normally those within the range of 30-120 C., preferably 40-l00 C., are employed.
• the mixed sugar When the mixed sugar is in the form of crystalline mixture or melted one, it may be directly dissolved in the mixed solvent under heating to form a supersaturated solution.
• the solution may be formed by the steps of adding the water within the specified quantitative range to solid mixed sugar, further adding polyhydric alcohol thereto, heating the system to form a homogeneous aqueous solution of the mixed sugar, and adding monohydric alcohol to the solution.
• crystalline glucose, crystalline fructose, or crystalline mixture of the two can be optionally crystallized from the supersaturated solution comprising the mixed sugar dissolved in the mixed solvent of monohydric alcohol and polyhydric alcohol.
• the crystallization temperature is subject to no particular limitation, as long as it is below the boiling point of the solvent and will allow the sugar in the solution to become supersaturated.
• a perferred crystallization temperature varies considerably, depending on the type of sugar to be crystallized. Generally speaking, however, the range of -20-70 C. is suitable.
• the pH of the supersaturated solution at the time of crystallization should be preferably in the vicinity of the neutral point. The solution should never be made acidic, because such invites objectionable side reaction.
• a crystalline mixture of glucose and fructose can be formed under the temperature and concentration conditions sufiicient to form a supersaturated solution of the mixed sugar, in the presence of crystal mother, or by suitable crystallization means such as stirring.
• the amount of mixed crystal mother of glucose and fructose to be added can be varied over a considerably wide range, depending on the crystallization rate and size of crystals formed, while a normally preferred range is 0.05 to 1 wt. percent based on the weight of the sugar.
• the crystallization temperature conveniently ranges from 0 to 50 C., particularly, l0-40 C. With such care, substantially all the sugar except the dissolved sugar at the selected temperature is crystallized within, for example, one to five days. Because the dissolved sugar is normally rather minor in quantity, the yield is almost quantitative.
• the crystalline mixture of glucose and fructose is separated from the mother liquor, by optional solid-liquid separation means such as a centrifuge, filtra tion, etc.
• solid-liquid separation means such as a centrifuge, filtra tion, etc.
• the mother liquor from which the crystalline mixture of glucose and fructose has been isolated and recovered may be discarded, or may be recycled to the preparation stage of the supersaturated mixed sugar solution, allowing continuous production of a crystalline mixture of glucose and fructose. With the latter practice, substantially all the sugar content of the starting mixed sugar can be ultimately recovered as the crystalline mixture of glucose and fructose.
• crystalline glucose and fructose can be separated, each in substantially pure form, from the solution formed by dissolving a mixed sugar containing fructose and glucose in a combination medium of liquid polyhydric alcohol and liquid monohydric alcohol, by the steps of (a) Adding crystalline glucose to the solution as the crystal mother under the temperature and concentration conditions sufficient for forming a supersaturated glucose solution, thereby crystallizing glucose from the solution, and
• the order of crystallization of each sugar from the supersaturated mixed sugar solution is not important. For example, if crystalline glucose is added as the crystal mother to the supersaturated mixed sugar solution, glucose will be crystallized, and if a crystal mother of fructose is added, fructose will be crystallized.
• a crystal mother of glucose is added to the supersaturated mixed sugar solution.
• the suitable amount of the crystal mother varies considerably, depending on the crystallization rate and size of crystals to be formed, while it is normally preferred to add 0.05 to 1 wt. percent of the crystal mother based on the sugar content.
• the maximum crystallization of glucose is achieved after 1-5 days from the time of addition.
• the formed glucose crystal is separated from the mother liquor by optional solid-liquid separation means, such as a centrifuge, filtration, etc.
• the crystallization of glucose is preferably performed at temperatures ranging from to 70 C.
• the mother liquor from which the crystallized glucose has been removed is a supersaturated fructose solution
• a crystal mother of fructose is added thereto to cause selective crystallization of fructose.
• the preferred quantity of the crystal mother of fructose is within the already specified range. Because the mother liquor from which the glucose has been removed occasionally still contains a minor amount of glucose remaining unseparated, it is desirable to eliminate or cause disappearance of such crystalline glucose by either heating the mother liquor to a temperature higher than the crystallization point of glucose, i.e., such a temperature at which the glucose concentration in the liquor is below the saturation point, or filtering the liquor.
• the crystallization of fructose is performed by addition of preferably 0.05-l wt. percent of crystal mother of fructose.
• the temperature of the system during the crystallization of fructose preferably ranges from -20 to 50 C. Under such conditions, the crystallization of fructose reaches the maximum quantity level within 1 to 2 days.
• fructose of at least to as high as 98% purity is isolated with high yield such as 40-85% based on the total fructose in the mixed sugar.
• the isolation yield of glucose and of fructose from a mixed sugar are obviously affected by the composition of the mixed sugar, but purity and yield of the glucose and fructose recovered in accordance with this invention far exceed those of conventional processes. This is persuasively demonstrated in the later given examples.
• the mother liquor from which glucose and fructose have been separated and recovered, can be continuously subjected to the crystallization treatments as described above, either as it is or as recycled to the preparation stage of supersaturated mixed sugar solution.
• a crystal mother of fructose is added to a supersaturated mixed sugar solution to cause crystallization of fructose.
• the crystallization is operated similarly to that of glucose, except that the composition of solution and temperature are suited to crystallization of fructose as above-described.
• fructose of 80-85% purity can be obtained with a yield of 10-35%.
• a crystal mother of glucose is added to cause crystallization of glucose, after optional heating to dissolve the remaining crystalline fructose or distill off a part of the monohydric alcohol, or of the monohydric alcohol and water.
• glucose of 80-95% purity is separated with a yield of 75-90%.
• the mother liquor remaining after the separation of fructose and glucose can be recycled into the preparation stage of the supersaturated mixed sugar solution.
• glucose and fructose can be selectively and alternately crystallized from a mixed sugar. Also a crystalline mixture of glucose and fructose can be recovered with high yield. Furthermore, the resulting glucose, fructose and crystalline mixture of the two have much higher purity than those obtained through conventional methods, and are obtained with much higher yields.
• the greatest advantage of the subject process resides in that, in the foregoing alternate crystallization operation, the mother liquor remaining after centrifugal or filtering separation of the crystals formed of the first stage crystallization can be used in the second stage crystallization as it is, without any intervening treatment.
• the conspicuous superiority of the subject process is apparent.
• fructoside as the solvent, even in the absence of any catalyst. Because The glucose, fructose and crystalline mixture of the two the solubility of fructose to fructoside is high, presence of obtained in accordance with the subject invention can be fructoside often invites reduction in fructose yield. 'Forused in the fields of foods, pharmaceuticals, and indusmation of such by-product can be readily confirmed by trial materials, after optional post treatment such as washmeans of thin layer chromatography. For example, when ing, drying, or recrystallization.
• the subject process is also highly valuable as a unit Into the remaining mother liquor (water content: process for making or refining particularly fructose. That 2.64% 500 g. of crystalline fructose were added as the is, as already explained, the fructose crystallization in crystal mother, and the system was allowed to stand for accordance with the invention is applicable to mixed 48 hours at 20 C. with stirring. Thus the optimum state sugar containing fructose and glucose at a ratio of 1:1. 40 for the fructose recovery with respect of both purity and This means that heretofore impossible refining of crude quantity was brought about. The formed crystals were fructose of low purity is rendered practicable. Convencentrifugally separated to provide 35 kg.
• crys- As the second advantage, the glucose crystallization step tals were centrifugally separated.
• Invert Invert Invert Invert Invert glucose Invert Invert Invert Starting material sugar sugar sugar sugar sugar 70 a sugar sugar Starting material as 50% aqueous soluticn (g. 1, 000 1, 000 1, 000 1, 000 1, 000 1, 000 1, 000 1, 000 Propylene glycol (above 98%) (g) 160 200 250 300 160 200 200 Weight of concentrated liquid (g 680 740 785 820 675 720 725 Ethanol (00.) 300 400 500 500 400 300 +28 +42 +32 +38 +39 +32 +39 84 93 86 91 91 81 91 200 165 180 160 265 290 275 Yield (percent) 80 66 73 64 76 83 83 crystallized fructose:
• EXAMPLE 3 (This example is to demonstrate the correlation between the yield and purity of the product glucose and fructose, with the quantitative ratio of ethanol to propylene glycol forming the combination medium, when an aqueous sugar solution composed of 30% of fructose and 70% of glutaining fructose and glucose, for example, invert sugar.)
• EXAMPLE 10 To 1 kg. of an aqueous solution of fructose (90% fructose and 10% glucose) of which the sugar content was 75 140 g. of propylene glycol were added. The system was concentrated in vacuum to provide 925 g. of concentrate containing 2% of water content. To the concentrate 460 cc. of anhydrous ethanol were added, followed by thorough mixing and cooling to room temperature. The system was then allowed to stand for 24 hours in the presence of a fructose crystal mother, whereupon the formation of pure fructose reached the maximum. The crystals were separated from the mother liquor by centrifuge, washed with approximately 200 cc. of anhydrous ethanol, and dried. Thus 572 g. of refined fructose of [m] 91 were obtained. The yield was 85% based on the fructose content of the starting material.
• EXAMPLE 11 (I) The 1st crystallization To 1 kg. of invert sugar containing 60% of water content, 80 g. of propylene glycol were added, and the system was concentrated in vacuum to provide 495 g. of the concentrated syrup containing 3% of moisture. To the syrup, 150 cc. of anhydrous alcohol were added, and the syrup was stirred to make a homogeneous solution with cooling. At the time, when the temperature of the mixed syrup was cooled to 40 C., 2 g. of glucose crystals and 2 g. of fructose crystals were added into the syrup as the crystal mother, and the syrup was stirred at a rate of 8 r.p.m. at room temperature. After 70 hours, the system was separated into the crystals and the liquid by a centrifuge. The separated crystals were washed with 200 cc. of anhydrous alcohol, and the crystallized mixture of glucose and fructose was obtained.
• EXAMPLE 12 (I) The 1st crystallization To 1 kg. of invert sugar containing 60% of water content (moisture), 70 g. of glycerin were added, and the system was concentrated by distillation in vacuum to maintain 3% moisture, and 492 g. of the concentrated syrup were obtained. To this syrup, 150 cc. of anhydrous alcohol were added, and the system was stirred to make a homogeneous solution which was allowed to stand for cooling. At the time, when the temperature of the mixed system was cooled to 40 C., 2 g. of glucose and 2 g. of fructose were added as the crystal mother and the system was stirred at a rate of 8 r.p.m. at room temperature. After 50 hours, the system was separated into the crystals and the liquid by centrifuge.
• the obtained crystals were washed with 200 cc. of anhydrous alcohol and the crystallized mixture of glucose and fructose was obtained.
• the mixture of the crystals of glucose-fructose obtained by the 2d crystallization showed the following yield and characteristics:
• EXAMPLE 13 To 1 kg. of invert sugar containing 60% of moisture, g. of propylene glycol were added, and the system was concentrated in vacuum to maintain 3% of moisture, yielding 540 g. of the concentrated syrup. To this syrup, cc. of anhydrous alcohol were added, and the system was stirred while allowing to stand for cooling to 40 C. To this system, 2 g. of glucose crystals and 2 g. of fructose crystals were added as the crystal mother and the system stirred at a rate of 8 r.p.m. After 90 hours, the system was separated by centrifuge into the crystals and the liquid. Then, the crystals separated were washed with 200 cc. of anhydrous alcohol and after drying, the mixture of the crystals of glucose-fructose was obtained.
• EXAMPLE 14 To 1 kg. of invert sugar containing 60% moisture, 40 g. of propyleneglycol were added, and the system was concentrated in vacuum to maintain 3% moisture, and 460 g. of the concentrated syrup were obtained. To this concentrated syrup, 150 cc. of anhydrous alcohol were added, and the system was homogeneously stirred at 6070 C. To this homogeneous mixture, 2 g. of glucose crystals and 2 g. of fructose crystals were added as the crystal mother at 40 C.
• the system was separated into the crystals and the liquid by a centrifuge.
• the separated crystals were washed with 200 cc. of anhydrous alcohol, and after drying, the mixture of the glucose-fructose crystals was obtained.
• EXAMPLE 15 To 1 kg. of an aqueous solution of mixed sugar (containing 12% of glucose and 28% of fructose), 80 g. of propyleneglycol were added. The system was concentrated by distillation in vacuum to maintain 2% of moisture, and 495 g. of the concentrated syrup were obtained. To the concentrated syrup, 200 cc. of anhydrous alcohol were added, and the system was cooled to 40 C. as it was allowed to stand with stirring. To the system, 2 g. of glucose crystals and 2 g. of fructose were added as the crystal mother, and the system was stirred at a rate of 8 r.p.m. After 70 hours, the system was separated into the crystals and the liquid by a centrifuge. The separated crystals were washed with 200 cc. of anhydrous alcohol and were dried.
• EXAMPLE 16 To 1 kg. of an aqueous solution of mixed sugar (containing 12% of glucose and 28% of fructose), 80 g. of propyleneglycol were added. The system was concentrated by distillation in vacuum to maintain 2% of moisture, and 495 g. of the concentrated syrup were obtained. To the concentrated syrup, 200 cc. of anhydrous alcohol were added, and the system was cooled to 40 C. with stirring as it was allowed to stand. To this system, 2 g. of glucose crystals and 2 g. of fructose crystals were added as the crystal mother, and the system was stirred at a rate of 8 r.p.m. After 80 hours, the system was sepa rated into the crystals and the liquid by a centrifuge. The separated crystals were washed with 200 cc. of anhydrous alcohol and were dried.
• EXAMPLE 17 To 1 kg. of an aqueous solution of mixed sugar (containing 12% of glucose and 12% of fructose), 70 g. of glycerin were added. The system was concentrated by distillation in vacuum to maintain 2% of moisture, and 495 g. of the concentrated syrup were obtained. To the concentrated syrup, 200 cc. of anhydrous alcohol were added, and the system was cooled to 40 C. with stirring as it was allowed to stand. To the system, 2 g. of glucose crystals and 2 g. of fructose crystals were added, and the mixture was stirred at a rate of 8 r.p.m. After 70 hours, the system was separated into the crystals and the liquid by a centrifuge. The separated crystals were washed with 200 cc. of anhydrous alcohol and were dried.
• mixed sugar containing 12% of glucose and 12% of fructose
• EXAMPLE 18 To 1 kg. of an aqueous solution of mixed sugar (con taining 12% of glucose and 28% of fructose), 70 g. of glycerin were added. The system was concentrated by distillation in vacuum, and 495 g. of the concentrated syrup were obtained. To the concentrated syrup, 200 cc. of anhydrous alcohol were added. The system was cooled to 40 C. with stirring as it was allowed to stand. To the system, 2 g. of glucose crystals and 2 g. of fructose crystals were added as the crystal mother, and the system was stirred at a rate of 8 r.p.m. After hours, the system was separated into the crystals and the liquid by a centrifuge. The separated crystals were washed with 200 cc. of anhydrous alcohol and were dried.
• mixed sugar con taining 12% of glucose and 28% of fructose
• EXAMPLE 19 To 1 kg. of invert sugar containing 50% of water content, 55% of ethylene glycolwere added, followed by concentration in vacuum to reduce the water content to 2.5%. Thus 565 g. of concentrate were obtained. The concentrate was thoroughly mixed with 280 cc. of anhydrous ethanol, and cooled to room temperature. Whereupon 3 g. of each of crystalline glucose and crystalline fructose were added as the crystal mother, and the system was allowed to stand for 72 hours, with stirring, until the crystallization reached the maximum. The system was then centrifuged to be separated into the crystals and mother liquor. The crystalline product having amounted to 480 g., the yield based on the starting material being 96%.
• the mother liquor from which the ethanol had been recovered was added to 1 kg. of invert sugar containing 5.0% of water content. 15 g. of ethylene glycol were added to the system to supplement the loss, again followed by concentration in vacuum. Repeating the foregoing procedures, a crystalline mixture of fructose and gluctose was recovered at a yield of more than 99% based on the starting invert sugar.
• the mother liquor from which ethanol had been recovered was added to 1 kg. of invert sugar containing 5 0% of water, and to which 18 g. of diethylene glycol were added to supplement the loss. Repeating the foregoing procedures, substantially more than 99% of a crystalline mixture of fructose and glucose was recovered.
• EXAMPLE 26 Examples 26, 27 and 28 demonstrate the experiments in which the significance of respective ratios of fructose and glucose source and polyhydric alcohol to the mixed solvent composed of monohydric alcohol, polyhydric alcohol and minor amount of water, were examined.
• EXAMPLE 28 To a homogeneous mixture of 125 g. of invert sugar (sugar content: 80%, water content: 20%) with 100 g. of propylene glycol, 5,000 cc. of anhydrous ethanol and 2 g. each of crystalline glucose and crystalline fructose were added by the order as mentioned before followed by stirring and standing at room temperature for approximately 24 hours. When the crystallization reached the maximum, the crystals were recovered by centrifuge with the following results:
• Amount of formed crystals 10 g.
• EXAMPLE 29 To 1 kg. of 50% aqueous solution of invert sugar, 200 g. of propylene glycol were added, followed by concentration in vacuum to reduce the water content to 3%. 730 g. of concentrate thus obtained were thoroughly mixed with 170 cc. of n-butyl alcohol, and cooled to room temperature. At such temperature, 6 g. each of anhydrous crystalline glucose and crystalline fructose were added into the system as crystal mothers, followed by standing with slow stirring. After 48 hours, the crystallization reached the maximum, and the crystals were centrifugally separated.
• EXAMPLE 30 To 1 kg. of 50% aqueous invert sugar solution, 250 g. of propylene glycol were added, followed by concentration in vacuum to reduce the water content to 3%. 800 g. of the resulting concentrate were thoroughly mixed with 200 cc. of iso-amyl alcohol and cooled to room temperature. Whereupon 3 g. each of anhydrous crystalline glucose and crystalline fructose were added into the system as crystal mothers, followed by standing with slow stirring. After 48 hours standing, the crystallization reached the maximum, and the crystals were centrifugally separated.
• the mother liquor from which the ethanol had been recovered was re-used in the repetitive practice of the above-described procedures.
• EXAMPLE 36 dates were used as the starting material of fructose and glucose.
• EXAMPLE 39 (This example explains the procedure wherein denatured-ethanols were used as the monohydric alcohol.)
• a process for preparing crystalline glucose, crystalline fructose or a mixture thereof which comprises form- 75 ing a solution in which a mixed sugar containing glucose and fructose is dissolved in a combination medium consisting essentially of:
• l 1 to 80% by volume of a liquid polyhydric alcohol selected from the group consisting of glycerin, glycerin monoalkylene ethers and glycols represented by the formula HO(RO) H wherein R is an alkylene group of 2 to 4 carbon atoms, and n is an integer of 1 to 4, and
• a liquid monohydric alcohol represented by the formula C H OH wherein n is an integer of 1 to 5, or a monoor polyalkylene glycol monoalkylether selected from ethylene glycol monoethylether and diethylene glycol monomethylether,
• said solution having a water content not exceeding 5% by weight and being supersaturated with glucose, fructose or both, and maintained at a temperature of from 20 C. to 70 C., the amount of said combination medium being from 0.1 to 20 times by weight of the weight of said mixed sugar at the time of crystallization; adding to said supersaturated solution a crystal mother selected from crystalline glucose, crystalline fructose and mixtures thereof, to thereby crystallize glucose, fructose or a mixture thereof; and recovering the crystallized product from said solution.
• liquid polyhydric alcohol is selected from the group consisting of glycerin, propylene glycol and ethylene glycol.
• liquid monohydric alcohol is an alcohol represented by the formula wherein n is an integer of 1 to 5.
• the process of claim 1 which comprises the steps of adding the liquid polyhydric alcohol to an aqueous solution of the mixed sugar containing glucose and fructose, concentrating the system at a temperature not higher than 100 C. until the water content of the solution is reduced to not more than 15% by weight, dissolving the resulting mixture in the liquid monohydric alcohol, and performing the crystallization from the resulting solution.
• a process for recovering a crystallized mixture of glucose and fructose from a mixed sugar containing glucose and fructose which comprises forming a solution by dissolving the mixed sugar containing glucose and fructose in a combination medium consisting essentially of 1 to 80% by volume of a liquid polyhydric alcohol selected from the group consisting of glycerin, propylene glycol and ethylene glycol and 99 to 20% by volume of a liquid monohydric alcohol represented by the formula wherein n is an integer of 1 to 5, the amount of said combination medium in the solution being 0.1 to 20 times by weight of the weight of said mixed sugar; adding to the solution a crystalline mixture of glucose and fructose as a crystal mother at a temperature ranging from 0 C. to 50 C. under the temperature and concentration conditions sufiicient for forming a supersaturated solution of the mixed sugar; and thereby forming a crystallized mixture of glucose and fructose from said supersaturated solution.
• a combination medium consisting essentially of 1 to
• a process for separating substantially pure crystals of glucose and fructose from a mixed sugar containing glucose and fructose which comprises forming a solution by dissolving the mixed sugar containing glucose and fructose in a combination medium consisting essentially of l to 80% by volume of a liquid polyhydric alcohol selected from the group consisting of glycerin, propylene glycol and ethylene glycol and 99 to 20% by volume of a liquid monohydric alcohol represented by the formula C H OH wherein n is an integer of 1 to 5, the amount of the combination medium in the solution being 0.1 to 20 times by weight of the weight of the weight of said mixed sugar; and separating glucose and fructose from said solution by conducting the following steps (a) and (b):
• liquid monohydric alcohol is denatured ethyl alcohol.

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• 1969
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