US3704168A - Process for the crystallization of glucose,fructose,or mixture of glucose and fructose - Google Patents

Abstract

A PROCESS FOR THE CRYSTALLIZATION OF GLUCOSE, FRUCTOSE, OR A MIXTURE OF THE TWO, WHICH IS CHARACTERIZED IN THAT THE CRYSTALLIZATION IS PERFORMED IN THE PRESENCE OF A COMBINATION MEDIUM OF A LIQUID POLYHYDRIC ALCOHOL AND LIQUID MONOHYDRIC ALCOHOL AS THE CRYSTALLIZATION MEDIUM.

Description

United States Patent Int. Cl. C13f 1/52, 1/06', 1/12 US. Cl. 127--58 11 Claims ABSTRACT OF THE DISCLOSURE A process for the crystallization of glucose, fructose, or a. mixture of the two, which is characterized in that the crystallization is performed in the presence of a combination medium of a liquid polyhydric alcohol and liquid monohydric alcohol as the crystallization medium.

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.

More particularly, 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.

Attempts to crystallize glucose, fructose, or mixture of the two, from mixed sugar containing glucose and fructose, such as invert sugar, using alcohols as the crystallization media, have been known.

For example, 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. However, in case 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. However, it is in practice difiicult to obtain completely inverted invert sugar, that is, invert sugar free of any impurities, on industrial scales. Furthermore, blending concentrated syrup of invert sugar with ethanol homogeneously and agitating the mixture at high speed is industrially very difficult, even though it is not impossible. The process, therefore, has not yet been successfully practiced on industrial scale.

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. Furthermore, 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.

We discovered that a combination medium of a liquid monohydric alcohol and liquid polyhydric alcohol is distinctly superior as the crystallization medium of glucose and fructose, in the attempt to separate such sugars in crystallized form from a mixed sugar containing the named two by simple crystallization means, and that, with the use of such combination medium, the sugars can be recovered in substantially pure form, without rigorous conditional limitations or the foregoing drawbacks, and at higher yield per one crystallization operation.

According to the invention, 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.

As the mixed sugar containing glucose and fructose, any of the mixed sugars which are generally present in the form of syrup i.e., aqueous solution, such as invert sugar, isomerized sugar (mixed sugar obtained by isomerization of glucose), honey, etc., can be used as the starting material. 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. By way of explanation, some of the mixed sugars may be specified as follows:

Percent by weight In the invention, 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. As the liquid polyhydric alcohol, dior tri-hydric aliphatic alcohols such as glycerin; glycerin monoalkylethers; or alkylene glycols or polyalkylene glycols of the general formula,

in which R is an alkylene group of preferably 24 carbons, and 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. As such 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,

in which n is an integer of 1 to 5, for example, methyl alcohol, ethyl alcohol, propyl alcohol, butanol, and amyl alcohol. Also 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. For example, the polyhydric alcohol may occupy 180% by volume of the total mixed alcohol solvent. For the purpose of this invention, it is particularly preferable to use 5-60% by volume of the polyhydric alcohol to the total alcohol solvent. In the presence of extremely minor amount of polyhydric alcohol in the solvent system, elution of the sugar to the alcoholic side is still remarkably increased, but the subsequent treatment of the system is unnecessarily complicated. In accordance with the present invention, it is suitable that at least 1% of the alcohol is the polyhydric alcohol. Whereas, if the polyhydric alcohol exceeds 80%, the solvent becomes viscous and ditficult to handle.

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. On the other hand, when the 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. Generally speak ing, therefore, the supersaturated mixed sugar solution preferably contains 1.5 to 5 wt. percent, of Water at the time of crystallization.

In case the mixed sugar containing glucose and fructose is an aqueous solution, it is also possible in accordance with the invention to reduce the water content to the above-specified range after addition of the liquid polyhydric alcohol thereto, by such means as distillation under atmospheric or reduced pressure, spray drying, etc., followed by dissolving of the resulting mixture in the liquid monohydric alcohol to form a supersaturated mixed sugar 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. This procedure is applied with particular advantage to isolation of glucose and fructose from a mixed syrup such as honey, date syrup, molasses, or invert sugar produced or obtained as a by-product in the sugar industry, and syrup such as isomerized sugar. In the practice, 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. The concentration temperature is variable depending on time, while normally those within the range of 30-120 C., preferably 40-l00 C., are employed.

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. Alternatively, 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.

According to the subject invention, 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.

According to one preferred mode of practicing the invention, from the solution formed by dissolving mixed sugar containing glucose and fructose in a combination medium of liquid polyhydric alcohol and liquid monohydric alcohol, 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. In the crystallization of a mixture of glucose and fructose, 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. Thereafter 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. Thus, by a single crystallization operation, a crystalline mixture of substantially pure glucose and fructose is isolated at a yield as high as -98% based on the sugar content of the starting mixed sugar.

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.

According to the optimum mode of practicing the invention, 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

(b) Adding crystalline fructose to the solution as the crystal mother, under the temperature and concentration conditions sufiicient for forming a supersaturated fructose solution, thereby precipitating crystallizing fructose from the solution, the order of performing the above steps (a) and (b) being optional.

In the above practice, 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.

According to one embodiment of the invention, first, 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. Then the formed glucose crystal is separated from the mother liquor by optional solid-liquid separation means, such as a centrifuge, filtration, etc. Thus glucose of at least 80% to as high as 95% purity is isolated at such excellent yield as 6085% based on the total glucose contained in the mixed sugar. The crystallization of glucose is preferably performed at temperatures ranging from to 70 C.

If 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.

Although it is possible to heat the mother liquor from which the glucose has been removed, to distill off a part of the monohydric alcohol, or of that and Water, thereby raising the degree of supersaturation of fructose in the liquor, such concentration procedure is normally not required in the present invention.

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. Thus 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.

For instance, taking the example of invert sugar in which the quantitative ratio of fructose to glucose is 1:1, the number of cycles necessary for completely crystallizing glucose and fructose therefrom by the above-mentioned continuous operation is conveniently expressed by the formula below:

Mixed sugar (Weight) Crystallized Orystallized glucose (weight) fructose (Weight) According to the subject process, substantially all the glucose and fructose can be ultimately effectively separated from the mixed sugar, with such few number of cycles as normally 1.2-1.9 when calculated by the above formula, i.e. with a very minor amount of recirculation.

According to another embodiment of the invention, first, 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. Thus fructose of 80-85% purity can be obtained with a yield of 10-35%.

To the mother liquor remaining after the separation of fructose, then 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. Thus 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.

The optimum conditions for the successive and alternate crystallization of glucose and fructose in accordance with the invention are, for example, as follows:

Number of cycles:

1 Degrees 0.

According to the present invention, with the use of a combination medium of polyhydric alcohol and monohydric alcohol, 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. In comparison with the conventional methods in which the mother liquor is invariably concentrated or subjected to cumbersome waterremoving step, the conspicuous superiority of the subject process is apparent.

Such successive, alternate crystallization without any been at best around 50% based on the total glucose content. With the subject process as much as 85% of the glucose present can be removed by one operation cycle. Thus the subject process is very elfective.

intervening treatment of mother liquor can be repeated This process therefore provides a very advantageous several times, as demonstrated in later given Example 1. method of fructose production, when practiced in combi- We further made an important technical discovery durnation with known methods of making fructose, for examing such repetitive crystallization from the same system ple, bromine oxidation method. over many cycles. That is, among the components of mixed As so far described, each unit process itself is valuable sugar, particularly fructose is highly reactive with alcohols, for the purpose of fructose preparation. The crystallization and tends to form fructosides during the above-described conditions of each unit process are entirely the same with operation, as the reaction product with the alcohols used those described as to the alternate crystallization process. 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. an ethanol fructose system is allowed to stand after addi- Hereinafter the invention will be explained with refertion of a mineral acid thereto, formation of ethyl fructoence to working examples, in which percentages are by side is observed as two spots having greater Rf value thail weight, unless otherwise specified. that of D-fructose in this layer chromatograph (silica ge solvent: ethylacetate:isopropyl alcohol:water=6:2:l). In EXAMPLE 1 some occasions, exactly the same substance is formed To 240 kg. of 50% aqueous invert sugar solution, 15 kg. under the crystallization conditions specified in the foreof p py glycol Wcfe added, followed y concmtlation i under reduced pressure. Thus obtained 137 kg. of the In order to inhibit such side reaction and increase the concentrate containing 2.2% of residual water were thoryield of each constituent sugar, the following care is Oug y ixed i h 50 ite s of anhy ro s lrecommended. Adjusting the water content of the system to 1.9%, to the (1) If an aqueous solution of mixed sugar added with homogeneous mixture 500 g. of crystalline glucose were polyhydric alcohol is to be concentrated, the concentra- 0 added as the crystal mother, and the mixture was allowed tion temperature should be selected at the lowest feasible to stand at 40 C. for 48 hours with stirring. In this way, level, and high temperature treatment at low water content the system assumed the state suitable for the crystal recovconditions should be given for the minimum feasible time. cry, from the standpoints of both purity and quantity. The

(2) Particularly in the glucose crystallization step, formed crystals were centrifugally separated, providing unnecessarily high temperatures should be avoided. 38 kg. of crystalline glucose of [a] ==|43.

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. of crystalline tionally, fructose has been refined by recrystallization from fructose of [a] =-88. ethanol, but unless the glucose content of the crude fruc- Further 200 g. of crystalline glucose were added into the rose to be refined is 10% or le in other word nle the mother liquor from which the crystalline fructose had been fructose purity is at least 90%, the glucose which is the recovered (water content: 3.15%), and the system was more difficulty soluble is first crystallized, and thus the allowed to stand at 30 C. for 48 hours with stirring, effective refining of fructose is impossible. Glucose is norbringing about the optimum state for crystalline glucose mally contained in fructose as an impurity component. recovery with respect to both purity and quantity. The Therefore, in the conventional preparation of fructose, 50 formed crystals were recovered by centrifuge, providing when fructose of the purity below 90% is obtained, it is 12 kg. of crystalline glucose of [a] =-|-47. recycled to the initial step of the production line. In con- 200 g. of crystalline fructose were again added to the trast thereto, according to the subject process substantially remained mother liquor (water content: 3.66%) as the pure fructose can be obtained even from invert sugar, i.e., crystal mother, and the system was allowed to stand for crude fructose of 50% purity, and extremely low purity 48 hours, at 20 C. with stirring. When the optimum fructose can also be refined as demonstrated in later given state for crystalline fructose recovery with respect to both examples. purity and quantity was brought about, the formed crys- As the second advantage, the glucose crystallization step tals were centrifugally separated. Thus 8.2 kg. of crysaccording to the invention serves as a more efficient, simtalline fructose of [a] =-90 were recovered. pler method for eliminating glucose and consequently (30 The mother liquor (water content: 4.16%) which reconcentrating the fructose component in the fructose promained was allowed to stand, forming a crystalline mixduction, compared with any of known methods. That is, ture of fructose and glucose. Centrifugally separating the with known methods of eliminating glucose by crystallizaformed crystals, 15 kg. of the mixed crystals of both tion, the removing efficiency per one operation cycle has glucose and fructose, [a] =--24 were obtained.

TABLE 1 Crystalline mixture of Crystalline glucose Crystalline fructose glucose and fructose Water Water Water content of content of content of crystallization crystallization crystallization system Yield system ld system Yield (P l rln (kg.) (percent) [czln (kg.) (percent) [a] (kg.) hiiifililifiifitlasi: 5:?2 it? i3 32% 33 8. 3 Third crystallization "4.16 51 "is 9 EXAMPLE 2 (This example is to demonstrate the preparation of glucose and fructose from invert sugar as the starting material, using as the polyhydric alcohol ethylene glycol, diethylene glycol, triethylene glycol, glycerol-ether and glycerin in each run, and first crystallizing glucose.) To each 1 kg. of aqueous invert sugar solution (concentration: 50%), 5085 g. of above-specified polyhydric alcohol were added. In all runs, the resulting solutions water content was reduced to 2% by concentration in vacuum, to which 270-290 cc. of anhydrous ethanol were added, followed by thoroughly stirring and cooling to room temperature. At room temperature, 6 g. of anhydrous crystalline glucose were added into the system as the crystal mother and the system was allowed to stand with slow stirring. After 48 hours, pure glucose crystals reached the maximum quantity, the system being then centrifuged to separate crude crystalline glucose from mother liquor. Into the liquor 1.2% based on the total sugar of crystalline fructose was added as the crystal mother, followed again by standing with slow stirring. After 48 hours standing highly pure fructose crystals reached the maximum, the crystals being centrifugally 10 accordance with the invention.) The results are shown as to Run Nos. 1 through 7.

To each 1 kg. of the above materials (concentration: 50%), 150800 g. of propylene glycol were added, and the water content of each system was reduced to 2% by concentration in vacuum. To the concentrate 200-500 cc. of anhydrous ethanol were added, thoroughly mixed, and cooled to room temperature. Then 6 g. of anhydrous crystalline glucose were added thereinto as the crystal mother, followed by standing with slow stirring. After 48 hours, the quantity of pure glucose crystals reached the maximum, then, the system was centrifugally separated into the crude crystalline glucose and mother liquor. To the liquor 1.2% based on the total sugar content of crystalline fructose was added as the crystal mother, followed again by standing with slow stirring. After 48 hours, the formation of pure fructose crystals reached the maximum. Then the system was centrifugally separated into crystalline fructose and mother liquor. Ethanol was recovered from the system, and the above operations were repeated. The cycles required for complete recovery of the sugars ranged from 1.5 to 1.9. The results were as given in Table 3 below.

TABLE 3 Run Number Fructose,

Invert Invert Invert Invert glucose Invert Invert Starting material 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 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:

--76 80 82 -78 -68 --70 70 Purity (percent) 89 92 98 91 84 85 85 158 130 125 150 78 60 70 Yield (percent) 63 62 50 60 52 16 46 Cycle number (approx.) 1. 6 l. 5 l. 9 1. 8 1. 6 1. 7 1. 6

separated from the mother liquor. Ethanol was recovered EXAMPLE 4 from the liquor, and the foregoing operations were repeated. The total cycles required for complete recovery of desried sugars were 1.7-2.2. The results are shown in Table 2 below.

TABLE 2 Polyhydric alcohol Glycerol- Dl- 'Iriether Ethylene ethylene ethylene (mono- Glycerin glycol glycol glycol methyl) (85%) Invert Invert Invert Invert Invert Starting material sugar sugar sugar sugar sugar Starting material as 50% aqueous solution (g.) 1, 000 1, 000 1, 000 1, 000 1, 000 Polyhydric alcohol (g.) 65 70 65 50 85 Weight of concentrated liquid (g.). 555 584 576 570 585 Ethanol (ec.) 270 290 290 285 290 Cr stallized lucose:

[u D g +32 +20 +39 Purity (percent) 85 87 86 76 91 G 154 182 176 152 156 Yzifilld (perceigt) 62 73 70 61 63 C st zed ruc ose:

ry 20 -7s -s0 7s -7s -s0 Purity (percent) 91 92 91 91 92 G 112 116 112 78 77 Yield (percent) 46 45 31 31 Cycle number (approximately)- 1. 8 1. 7 1. 7 2. 2 2. 1

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.)

To each 1 kg. of aqueous invert sugar solution (concentration: g. of propylene glycol were added, and the water content of each system was reduced to 3% by concentration in vacuum. To 575 g. of the concentrate, 290 cc. of anhydrous ethanol were added, mixed thoroughly, and cooled to room temperature. 6 g. of anhydrous crystalline glucose were added into the system as the cose, and an aqueous invert sugar solution are treated in crystal mother, and the system was allowed to stand with 1 1 slow stirring. After 48 hours when the formation of pure glucose crystals reached the maximum quantity, the crystalline glucose was recovered by centrifugal separation. 17 g. of glucose with [or] =-I-32 were recovered.

12 crystals were separated by centrifuge. 230 g. of the crystalline product, [a] =-82 were obtained.

The above procedures were repeated with the mixture of starting invert sugar with filtrate of recrystallization To the mother liquor which remained, 3 g. of crystalline 5 of previously obtained glucose and fructose. The average fructose were added as the crystal mother, and the system yields of crystalline fructose and glucose each became was allowed to stand with slow stirring. After 48 hours approximately 47-48% based on the starting material standing when pure fructose attained the maximum (total amount of mixed sugar). amount, the system was centrifugally separated into the EXAMPLE 6 crystalline fructose and mother liquor. The crystalline l product having 20 amounted to g. (In this example, three types of starting materials were anol was recovered f the mother liquor and the used for glucose preparation, 1.e., invert sugar, mixed concentrate was repeatedly subjected to the foregoing Sugar of 70% glucose and 30% fructose: and mlxed treatments. The cycles required for complete recovery of Sugar of 30% glucose and Q fructqse) the sugar were approximately 7 To each 1 kg. of the starting materials (solid content: 50% 150-300 g. of polyhydric alcohol specified 111 EXAMPLE 5 Table 3 were added. After each system was concentrated in vacuum (water content: 3%), to the concentrate 200- To 1 kg. of aqueous invert solution (concentration: 500 cc. of anhydrous ethanol were added, thoroughly 50%) 60 g. of propylene glycol were added, and the Water mixed and cooled to room temperature. Then 6 g. of content thereof was reduced to 2.5% by concentration in anhydrous crystalline glucose were added into the system, vacuum. To 570 g. of the concentrate, 280 cc. of anhyfollowed 'by standing with slow stirring. After 48 hours, drous ethanol were added, followed by thorough mixing the formation of pure glucose crystals reached the manand cooling to 40 0.:2 C. At that temperature 6 g. mum, and then the crystals were separated from the of anhydrous crystalline glucose were added to the system mother liquor by centrifuge. Thus 5 0-290 g. of crystalline as the crystal mother. After 72 hours standing with slow glucose having [a] =+32--|42 were obtained. The stirring, the formation of pure glucose crystals in the experimental data and results were as in Table 4.

TABLE 4 Polyhydrie alcohol Propyl- Propyl- Ethyi- Triethyl- Propyl- Propyl- Propyl- 6118 6B8 8118 8B9 0116 9119 8118 glycol glycol glycol glycol glycol glycol glycol Run number Frurgtgose, Fruezggse Fructose, Fruetose Invert glucose glucose glucos e glucose Invert Invert Starting material sugar 70% 70 0 70% sugar sugar Starting material as 50% aqueous solution (g.) 1, 000 1, 000 1, 000 1, 000 1, 000 1, 000 1, 000 Amount of polyhydric alcohol (g. 60 60 60 70 80 100 250 Weight of concentrated liquid 570 585 575 580 600 615 780 Ethanol (cc.) 290 290 290 290 300 310 390 Orystallized glucos [0:] +32 +32 +34" +30" +3s +41 Purity (percent) 95 81 81 86 84 90 93 192 290 285 285 188 160 Yield (percent) 77 83 81 81 33 75 64 system reached the maximum, the crystals being recovered EXAMPLE 7 by centrifuge. 215 g. of crystalline glucose having To the mother liquor which remained, 3 g. of crystalline fructose were added as the crystal mother, followed by standing with slow stirring. The formation of pure fructose crystals reached the maximum after 24 hours. Then the fructose was recovered by centrifuge, providing 183 g. of the crystals [a] "'=82.

Ethanol was recovered from the mother liquor which remained, and the concentrate was mixed with 1 kg. of aqueous invert sugar solution concentration: 50%), followed by addition of 25 g. of propylene glycol and concentration in vacuum (water content: 2%). To 660 g. of the concentration, 330 cc. of anhydrous ethanol were added and stirred thoroughly. To the system which was subsequently cooled to 40 C.i2 C., 6 g. of anhydrous crystalline glucose were added as the crystal mother. After 72 hours standing with slow stirring, the formation of pure glucose crystals reached the maximum, then the crystals were separated by centrifuge. The yield was 240 g., having [cc] =+38.

Into the mother liquor which remained, 3 g. of crystalline fructose were added, and the system was allowed to stand with slow stirring. After 24 hours, the formation of pure fructose crystals reached the maximum, then the (This example is to explain the embodiment wherein fructose is first crystallized from a starting material of mixed sugar.)

To 1 kg. of aqueous invert sugar solution (concentration: 50%) 60 g. of propylene glycol were added, and the water content of the system was reduced to 2% by concentration in vacuum. To 580 g. of the concentrate, 290 cc. of anhydrous ethanol were added, thoroughly mixed, and cooled to room temperature. Then 6 g. of crystalline fructose were added into the system as the crystal mother, followed by standing with slow stirring. After 48 hours standing, the formation of pure fructose crystals reached the maximum. Recovering the fructose crystals by centrifuge, g. of the product of [a] =7O were obtained. From the mother liquor which remained, ethanol was recovered, and the concentrate was concentrated in vacuum to 475 g. To that concentrate 240 cc. of anhydrous ethanol were added, followed by thorough mixing and cooling. Thereafter 3 g. of crystalline glucose were added into the system which subsequently was allowed to stand with slow stirring. After 48 hours standing the formation of glucose crystals reached the maximum, and the crystals were separated by centrifuge. Thus 185 g. of crystalline glucose of [a] =+39 were obtained. The mother liquor, from which ethanol had been recovered, was subjected to the foregoing procedures repetitively.

EXAMPLE 8 To 1,000 g. of an aqueous solution of crude fructose (60% fructose and 40% glucose) of which the sugar content was 75%, 150 g. of propylene glycol were added. Reducing the water content thereof to 2% by concentration in vacuum, 930 g. of concentrate were obtained. To the concentrate 65 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 the fructose crystal mother, whereupon the formation of fructose crystals reached the maximum. Thus 160 g. of crystalline fructose of [u] =-75 were obtained. The yield was 35% based on the fructose content of the starting material.

EXAMPLE 9 To 1 kg. of invert sugar (concentration: 50%), 60 g. of propylene glycol were added. Reducing the water content of the system to 3% by concentration in vacuum, 580 g. of concentrate were obtained. To the concentrate 290 cc. of anhydrous ethanol were added, followed by thorough mixingand cooling to room temperature. Then 6 g. of crystalline fructose were added into the system as the crystal mother, and the system was allowed to stand with slow stirring. After 48 hours standing, the formation of pure fructose crystals reached the maximum, and the crystals were separated from the mother liquor by centrifuge. Thus 85 g. of crystals of [u] =-70 were recovered. The yield was 34% based on the fructose content of the Starting material.

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.

Yield of the dried mixture (of the crystallized glucosefructose): 360 g.

Yield based on the starting material: 90%

Optical rotation of the crystallized mixture: [e]

(H) The 2d and successive crystallizations From the liquid obtained by the centrifuge, alcohol was recovered by distillation in vacuum. To 1 12 g. of the YIELD 2d 8d 4th 5th The dried mixture (of the crystallized glucose and fructos 396 394 395 Yield based on the material used (percent) .7 99.1 98.5 98. 7 Opticalrotation of the crystals [a]1 19.0 20.0 19.5 19.5

As shown in this experiment, the yield of the crystallized mixture of glucose and fructose based on the material used were almost quantitative.

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.

Yield of the dried mixture (of the crystallized glucosefructose): 340 g.

Yield based on the material used:

Optical rotation of the mixture: [oc] =8.0

(II) The 2d crystallization From the liquid separated by centrifuge in the 1st crystallization, alcohol was recovered by distillation in vacuum. To 132 g. of the mixture of glycerin and sugars (not formed into crystals, that is, dissolved sugar), which remained after distillation, 1 kg. of invert sugar containing 60% of moisture and 10 g. of glycerin were added, followed by repeating a crystallization similar to the 1st crystallization process.

The mixture of the crystals of glucose-fructose obtained by the 2d crystallization showed the following yield and characteristics:

Yield of the dried mixture (of the crystallized glucosefructose): 390 g.

Yield based on the material used: 97%

Optical rotation of the mixture: [a] =18.2

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.

Yield of the dried mixture (of the crystallized glucosefructose): 259 g. Yield based on the material used: 74% Optical rotation of the crystals: [a] =+4.2

As shown in this experiment, the crystallized amount of fructose was reduced by additional increase of propylene glycol, but the repetitive use of this mother liquor as mentioned in Example 11, resulted in the quantitative yield of the mixture of glucose-fructose crystals based on the material used.

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.

Then, after the mixture was sustained at 35 C., the system was stirred for 40 hours, and was successively stirred at a rate of 8 r.p.m. with cooling slowly to C.

After 70 hours from the addition of glucose and fructose, 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.

Yield of the dried mixture (of the crystallized glucosefructose): 378 g.

Yield based on the material used: 95%

Optical rotation of the mixture: [a] =--14.5

It was possible to use the above mother liquor repeatedly as performed in Example 11.

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.

Yield of the dried mixture (of the crystallized glucosefructose): 365 g. Optical rotation of the mixture: [a] =+13.0

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.

Yield of the dried mixture (of the crystallized glucosefructose): 320 g. Optical rotation of the mixture: [u] =44 1 6 The liquid separated by centrifuge could be used again as mentioned in Example ll.

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.

Yield of the dried mixture (of the crystallized glucosefructose: 350 g. Optical rotation of the mixture: [a] =+11 The liquid separated by centrifuge could be used repeatedly as mentioned in Example 11.

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.

Yield of the dried mixture (of the crystallized glucosefructose): 310 g. Optical rotation of the mixture: [u] --38 The liquid separated by centrifuge could be used repeatedly as mentioned in Example 11.

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.

EXAMPLE 20 To 1 kg. of invert sugar containing 50% of water, g. of propylene glycol were added, followed by concentration in vacuum to reduce the water content thereof to 3%. Thus 610 g. of concentrated liquid were obtained. The liquid was thoroughly mixed with 120 cc. of anhydrous propyl alcohol, and cooled to room temperature. Whereupon 3 g. each of crystalline glucose and fructose were added to the mixture as the crystal mothers, followed by standing for 72 hours with stirring, until the crystallization reached the maximum. The system was then centrifugally separated into the crystals and mother liquor. Thus 400 g. of crystalline product of [a] =+9 were obtained. The mother liquor from which propyl alcohol had been recovered was added to 1 kg. of invert sugar containing 50% of water, and to which further 10 g. of propylene glycol were added to supplement the loss. The water content of the system was again reduced by concentration in vacuum, and the system was subjected to the foregoing crystallization treatment. With such repetitive practice, substantially more than 99% based on the starting invert sugar material of a crystalline mixture of fructose and glucose was recovered.

EXAMPLE 21 To 1 kg. of invert sugar containing 50% of water, 100 g. of propylene glycol were added, followed by concentration in vacuum to reduce the water content to 3%. Thus 670 g. of concentrate were obtained, which was subsequently thoroughly mixed with 120 cc. of anhydrous n-butyl alcohol, and cooled to room temperature. Into the system, 3 g. each of crystalline glucose and crystalline fructose were added as crystal mothers, and the system was allowed to stand for 72 hours with stirring, until the crystallization reached the maximum. Thus 420 g. of crystals having [a] =+5 were recovered by centrifugal separation. The mother liquor from which butyl alcohol had been recovered were added to 1 kg. of invert sugar containing 50% of water, and further 10 g. of propylene glycol were added to supplement the loss, followed again by concentration in vacuum to reduce the water content.

By thus repeating the foregoing procedure, substantially more than 99% based on the starting invert sugar material of a crystalline mixture of fructose and glucose was recovered.

EXAMPLE 22 To 1 kg. of invert sugar containing 50% of water, 20 g. of propylene glycol were added, followed by concentration in vacuum to reduce the water content to 3%. 520 g. of concentrated liquid thus obtained were thoroughly mixed with 200 cc. of anhydrous methanol, cooled to room temperature, and 3 g. each of crystalline glucose and crystalline fructose as crystal mothers were added. The system was allowed to stand for 72 hours with stirring, until the crystallization reached the maximum. Then the system was centrifuged to provide 340 g. of crystalline product of [a] =-|15. The mother liquor which remained from which the methanol had been recovered was added to 1 kg. of invert sugar containing 50% of water. Further 5 g. of propylene glycol were added to supplement the loss, followed again by concentration in vacuum to reduce the water content to 3%. By thus repeating the foregoing procedure, substantially more than 99% based on the starting invert sugar material of a crystalline mixture of fructose and gluctose was obtained.

EXAMPIJE 23 To 1 kg. of invert sugar containing 50% of water, 70 g. of diethylene glycol were added, followed by concentration in vacuum to reduce the water content to 3% 584 g. of the concentrated liquid thus obtained were thoroughly mixed with 290 cc. of anhydrous ethanol, and cooled to room temperature. Then 3 g. each of crystalline glucose and crystalline fructose were added into the sys tem as crystal mothers, followed by 72 hours standing with stirring. The crystallization then attained the max imum and the crystals were centrifugally separated from the mother liquor. Thus 485 g. of the crystals [a] =-l7 were recovered, corresponding to a yield of 97% based on the starting material. 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 24 To 1 kg. of invert sugar containing 50% of water, 65 g. of triethylene glycol were added, followed by concentration in vacuum to reduce the water content to 3%. 570 g. of the concentrated liquid thus obtained were thoroughly mixed with 290 cc. of anhydrous ethanol, cooled to room temperature, and 3 g. each of crystalline glucose and crystalline fructose were added as crystal mothers. After subsequent standing of 72 hours with stirring, the amount of crystallization reached the maximum, the crystals being centrifugally separated from the mother liquor. Thus 455 g. of crystals of [a] =l5 were recovered, corresponding to a yield of 91% based on the starting material. The mother liquor from which the ethanol had been recovered was added to 1 kg. of invert sugar containing 50% of water, and to the system 15 g. of triethylene glycol were added, again followed by concentration in vacuum to reduce the water content. Then repeating the foregoing procedures, substantially more than 99% based on the starting material of a crystalline mixture of fructose and glucose was recovered.

EXAMPLE 25 To 1 kg. of invert sugar containing 50% of water, 50 g. of glycerin alpha-monomethylether were added, followed by concentration in vacuum to reduce the water content to 3%. 560 g. of concentrate thus obtained were thoroughly mixed with 280 cc. of anhydrous ethanol, and cooled to room temperature. Then 3 g. each of crystalline glucose and fructose were added into the system as crystal mothers, followed by 72 hours standing. When the crystallization reached the maximum, the crystals were centrifugally separated from the mother liquor. 452 g. of the cryals, [a] =15 were obtained, corresponding to a yield of based on the starting material. The mother liquor from which ethanol had been recovered was added to 1 kg. of invert sugar containing 50% of water, and to which 11 g. of glycerin alpha-monomethyl ether were added to supplement the loss, followed again by concentration in vacuum. Repeating the foregoing procedures, substantially more than 99% based on the starting invert sugar material of a crystalline mixture of fructose and glucose was obtained.

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.

To 110 g. of invert sugar (sugar content: 90%, water content: 10%), g. of propylene glycol were added, and thoroughly mixed. To the mixture 1,000 cc. of anhydrous ethanol were added, and thereafter 1 g. each of crystalline glucose and crystalline fructose was added into the system as the crystal mother. After stirring, the system was allowed to stand for 24 hours, when the crystallization reached the maximum. The crystals were recovered by a centrifuge, with the results as follows:

Amount of formed crystals: 74 g. Optical rotation of the crystals, [u] +20 Yield of crystals: 75%

1 9 EXAMPLE 27 To a homogeneous mixture of 110 g. of invert sugar (sugar content: 90%, water content: with 100 g. of propylene glycol, 2,000 cc. of anhydrous ethanol, and 1 g. each of crystalline glucose and crystalline fructose as crystal mother, were added by the order as stated before, followed by stirring and standing for 24 hours at room temperature. When the crystallization reached the maximum, the crystals were recovered by centrifugal separation with the following results:

Amount of formed crystals: 20 g. Optical rotation of the crystal, [a] +49 Yield of crystals: 20%

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. Optical rotation of the crystals, [a] +50 Yield of the crystals: 10%

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.

Amount of the crystals: 400 g. Optical rotation of the crystals, [a] -7 Yield of the crystals: 80%

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.

Amount of the crystals: 280 g. Optical rotation of the crystals, [u] +22 Yield of the crystals: 56%

EXAMPLE 31 Amount of the crystals: 300 g. Optical rotation of the crystals, [a] +25 Yield of the crystals: 60%

EXAMPLE 32 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%. 740 g. of the concentrate thus obtained were thoroughly mixed with cc. of n-amyl alcohol, and cooled to 40- 45 C. Whereupon 6 g. of anhydrous crystalline glucose was added into the system as crystal mother, followed by standing with mild stirring at such temperature. After 48 hours standing, the formation of pure glucose crystals reached the maximum, and the crystals were recovered by centrifugal separation. 170 g. of crystalline glucose [a] =+51 were obtained, corresponding to a yield of 64%.

EXAMPLE 33 .added as the crystal mother, followed by standing with mild stirring at the specified temperature. After 48 hours standing, the crystallization of pure glucose reached the maximum, and the crystals were recovered by centrifugal separation. 170 g. of glucose of crystals [u] =+5l were obtained, corresponding to the yield of 64%.

EXAMPLE 34 To 1 kg. of 50% aqueous invert sugar solution, 200 g. of propylene glycol were added, followed by concentration in vacuum to reduce the water content to 3%. 735 g. of the concentrate thus obtained were thoroughly mixed with 250 cc. of n-butyl alcohol, and cooled to 4045 C. Whereupon 6 g. of anhydrous crystalline glucose were added into the system as the crystal mother, followed by allowing the system to stand at the specified temperature with mild stirring. After 48 hours standing, the formation of pure glucose crystals reached the maximum, and the crystals were recovered by centrifugal separation. g. of crystalline glucose [u] =+35 were obtained. The mother liquor separated by the centrifuge was cooled to room temperature, into which 3 g. of crystalline fructose were added as the crystal mother. After subsequent standing of 48 hours with mild stirring, the formation of pure fructose crystals reached the maximum, and the crystals were centrifugally separated. 120 g. of crystalline fructose of [a] =80 were obtained. The mother liquor from which the n-butyl alcohol had been recovered was used in the repetitive practice of the foregoing procedures.

EXAMPLE 35 To 1 kg of 50% aqueous invert sugar solution 50 g. of propylene glycol were added, followed by concentration in vacuum to reduce the water content to 3%. 580 g. of the concentrate thus obtained were thoroughly mixed with 200 cc. of anhydrous methanol, and cooled to room temperature. Whereupon 6 g. of anhydrous crystalline glucose were added into the system as the crystal mother. After subsequent standing of 48 hours with mild stirring, the formation of pure glucose crystals reached the maximum, and the crystals were separated from the mother liquor by centrifuge. Thus 163 g. of crystalline glucose of [a]1 =+43 were obtained.

The mother liquor was cooled to room temperature, to which 3 g. of crystalline fructose were added as the crystal mother, followed by standing with mild stirring. After 48 hours, the formation of pure fructose crystals reached the maximum, and the crystals were centrifugally 21 separated. This 135 g. of crystalline fructose [a] =80 were obtained. The mother liquor from which the ethanol had been recovered was re-used in the repetitive practice of the above-described procedures.

EXAMPLE 36 In this example, dates were used as the starting material of fructose and glucose.

kg. of esculent dried dates from Iraq, together with 40 liters of water, were heated for 8 hours at 90 C., then cooled to room temperature, and centrifuged to remove insoluble matters. To the remaining system 200 g. of calcium hydroxide were added, followed by thorough stirring and standing for 3 hours. The system was again centrifuged to remove the insoluble matter. The mother liquor was neutralized with sulfuric acid, and further acidified to the pH in the vicinity of 2, followed again by standing for about hours. After another centrifugal separation, the mother liquor was deacidified and desalted with an ionexchange resin. Thus obtained date sugar solution was decolorized and deodorized with activated carbon and refined.

To the refined date sugar solution, 800 g. of propylene glycol were added, followed by concentration in vacuum to reduce the water content to 3%. 5 kg. of the resulting concentrate were mixed with 2,000 cc. of anhydrous ethanol homogeneously, and cooled to room temperature. Whereupon 30 g. each of anhydrous crystalline glucose and crystalline fructose were added into the system as crystal mothers, and the system was allowed to stand with mild stirring. After 72 hours standing, the crystallization reached the maximum, and the formed crystals were centrifugally separated.

Amount of the crystals: 2,100 g. Optical rotation of the crystals: [a] =+10 Yield of the crystals,

recovered crystals estimated amount of sugar contained in dates- EXAMPLE 37 In this example, honey was used as the starting material.

To a homogeneous mixture of 1 kg. of honey (clover) and 3 liters of water, sulfuric acid was added to adjust the pH between 1-2, and the system was allowed to stand at room temperature for 15 hours. Then the sulfuric acid was neutralized with calcium hydroxide and the pH was raised to about 10. Whereupon the system was centrifuged to remove the insoluble matter, and the mother liquor was dealkalized and desalted with an ion-exchange resin, followed by further refining by decolorizing and deodorizing with activated carbon.

To the refined honey, 140 g. of propylene glycol were added, followed by concentration in vacuum to reduce the water content to 3%. 800 g. of the concentrate thus obtained were homogeneously mixed with 400 cc. of anhydrous alcohol and cooled to room temperature. Where- The amount of crystals: 440 g. Optical rotation of the crystals: [u] =+8 Yield of the crystals,

5 recovered crystals estimated amount of used sugar 0 EXAMPLE 38 1 (This example demonstrates an experiment wherein the crystalline glucose and fructose crystals from the mixed solution of the starting material in a mixed solvent of polyhydric alcohol and monohydric alcohol was performed under low temperature conditions.)

To 500 g. of invert (sugar content: 50%, water content: 50%), 125 g. of propylene glycol were added, followed by concentration in vacuum to reduce the water content to 2.0%. 390 g. of the concentrate thus obtained were thoroughly mixed with 500 cc. of anhydrous ethanol and cooled to room temperature. Whereupon 6 g. of crystalline glucose were added as the crystal mother. While the system was allowed to stand with mild stirring for 60 hours, the temperature was lowered at a uniform rate, finally to 0 C. When the crystallization of glucose reached the maximum, the crystals were centrifugally recovered, providing 175 g. of the crystals [a] +40.

Into the mother liquor, 3 g. of crystalline fructose were added as the crystal mother, followed by standing for 60 hours, with lowering temperature at a uniform rate, starting from room temperature to ultimately -l0 C. When the crystallization of fructose reached the maximum, the system was centrifugally separated. Thus 150 g. of crystalline fructose [a] =75 were obtained.

EXAMPLE 39 (This example explains the procedure wherein denatured-ethanols were used as the monohydric alcohol.)

To 1 kg. of 50% aqueous invert sugar solution, 90 g. of propylene glycol were added, followed by concentration in vacuum to reduce the water content to 2%. 620 g. of the concentrate thus obtained were thoroughly mixed with 250 cc. of anhydrous alcohol containing a denaturant, and to the system 6 g. of anhydrous crystalline glucose were added as the crystal mother, followed by standing at -45 C. for 48 hours with mild stirring. When the formation of pure glucose crystals reached the maximum, the system was centrifuged. Thus 160-479 g. of crystals [a] =+37+45 were recovered.

The mother liquor which remained was cooled to about 30-10 C., to which system 3 g. of crystalline fructose were added as the crystal mother followed by 48 hours standing with mild stirring. When the formation of pure fructose crystals reached the maximum, the system was centrifuged. Thus 115-135 g. of crystalline fructose of [m] =-80- -88 were recovered. The denatured ethanol was recovered from the remaining mother liquor.

The above procedures were repeated, with due supplementing of propylene glycol loss. The results were as upon 6 g. each of anhydrous crystalline glucose and crysso given in Table 5.

TABLE 5 Eth 1 h i I yet y Eth l Modifier Methanol Benzole Toluol ether ketone Gasoline Kersene acetage Pyridine Amount of modifier (g.) 8.8 2. 5 2.5 8. 8 3. 8 8.0 2. 5 giihydrous ethanol (00.) 260 259 250 250 250 250 250 35( H0058: Yield (g.) 175 175 179 170 0 F (:ptical rotation [(21 +45 +40 +40 +42 +41 +37 +39 tis +11 Yield (g.) 115 135 130 130 137 Optical rotation [111D --8S s2 -s2 -sa -s4 s0 $2 $33 i? talline fructose were added to the system as crystal mothers, followed by standing with mild stirring, When We claim:

the crystallization reached the maximum after 72 hours standing, the crystals were recovered by centrifugal separation.

1. 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

(2) 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, 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.

2. The process of claim 1 wherein said liquid polyhydric alcohol is selected from the group consisting of glycerin, propylene glycol and ethylene glycol.

3. The process of claim 1 wherein said liquid monohydric alcohol is an alcohol represented by the formula wherein n is an integer of 1 to 5.

4. The process of claim 1 wherein said liquid polyhydric alcohol is present in an amount of 5 to 60% by volume based on the total alcohol.

5. The process of claim 1 wherein said combination medium is present in an amount of 0.3 to 2 times by weight of the mixed sugar.

6. 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.

7. The process of claim 1 wherein said liquid monohydric alcohol is denatured ethyl alcohol.

8. 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.

9. The process of claim 8 wherein said liquid monohydric alcohol is denatured ethyl alcohol.

10. 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):

(a) adding to the solution crystalline glucose as a crystal mother at a temperature ranging from 0 C. to C. under the temperature and concentration conditions sufficient for forming a supersaturated solution of glucose, thereby forming glucose crystals from the solution, and

(b) adding to the solution crystalline fructose as a crystal mother at a temperature ranging from 20" C. to 50 C. under the temperature and concentration conditions sufiicient for forming a supersaturated solution of fructose, thereby forming crystals of fructose,

the order of performing said steps (a) and (b) being optional.

11. The process of claim 10 wherein said liquid monohydric alcohol is denatured ethyl alcohol.

References Cited UNITED STATES PATENTS 3,219,484 11/1965 Smythe et al 127 ss 2,943,004 6/1960 Haury 127 5s 2,357,838 9/1944 Mahoney 12758 2,501,914 3/1950 Payne 127 5sx 3,401,059 9/1968 Casey 12761 JOSEPH SCOVRONEK, Primary Examiner U.S. Cl. X.R.