Method for the continuous manufacture of anhydrous crystalline maltitol and a manufacturing apparatus therefor

Disclosed herein is a continuous manufacturing method for anhydrous crystalline maltitol comprising the following steps: (i) a heating and concentrating step where an aqueous solution containing maltitol in which maltitol is a main ingredient is continuously heated and concentrated to give a concentrated solution having a high concentration; (ii) a seed crystal adding and mixing step where the seed crystals are added to and mixed with the above concentrated solution with heating to give a massceuite containing the seed crystals; and (iii) a crystal aging step where the massceuite is subjected to disintegration, mixing, stirring and transfer in an atmosphere in which temperature and moisture are adjusted to proceed the crystallization.

TECHNICAL FIELD OF THE INVENTION 
The present invention relates to a method and an apparatus for the 
manufacture of stable anhydrous crystalline maltitol on a total amount 
method (may be called a total sugar method as well) on a continuous basis. 
More particularly, the present invention relates to a method for the 
manufacture of stable anhydrous crystalline maltitol within short time 
wherein a step of heating and concentrating an aqueous solution containing 
maltitol, a step of producing a seed crystal-containing supersaturated 
substance (massceuite) by adding and mixing seed crystals to and with the 
concentrated maltitol solution, a step of aging the crystals for 
proceeding the crystallization at high temperature and increased humidity, 
etc. are continuously conducted and also to an apparatus used therefor. 
The anhydrous crystalline maltitol used in the present invention may be 
anything so far as it is a substantially non-hygroscopic or hardly 
hygroscopic crystalline maltitol and, in addition to such an anhydrous 
crystalline maltitol, it may also be molasses-containing crystals which 
contains a sugar alcohol such as sorbitol, maltotriitol and maltotetraitol 
or a saccharide such as glucose and fructose. 
PRIOR ART 
Maltitol crystals are inherently highly hygroscopic and there have been 
considerable investigations on a method for the manufacture of 
non-hygroscopic crystalline powder. For example, a method for the 
manufacture of anhydrous crystalline maltitol or anhydrous crystalline 
maltitol molasses-containing crystals is mentioned in the Japanese 
Examined Patent Publication Sho-63/2439B. Details of that method are as 
follows. Thus, a solution of maltitol for crystallization is made in a 
degree of supersaturation of about 1.05-1.5 and, to be more specific, 
maltitol having a purity of not less than 65% is made into an aqueous 
solution of about 65-95% concentration, such a supersaturated maltitol 
solution of a relatively high temperature of 45-95.degree. C. is charged 
in a crystallizing vessel, then 0.1-20% of seed crystals are added thereto 
and the mixture is slowly cooled with gentle stirring for promoting the 
crystallization whereupon massceuite is obtained. Known method such as 
molasses separation method, block disintegrating method, fluid granulating 
method and spray drying method may be utilized as a method for collecting 
anhydrous crystalline maltitol and molasses-containing crystals which 
contain the anhydrous crystalline maltitol from the crystallized 
massceuite. 
For example, a molasses separation method is usually a method in which a 
massceuite is charged in a centrifugal separator of a basket type to 
separate into anhydrous crystalline maltitol and molasses. If necessary, 
said crystals may be easily washed by means of spraying a small amount of 
cold water thereon and such a method is suitable for the manufacture of 
non-hygroscopic anhydrous crystalline maltitol having a high purity. In 
the case of a spray drying, a massceuite having a concentration of 70-85% 
and degree of crystallization of about 25-60% is sprayed from a nozzle 
using a high-pressure pump, dried with hot air of such a temperature that 
the crystal powder is not melted (for example, 60-100.degree. C.) and aged 
using warm air of 30-60.degree. C. for about 1-20 hours whereupon 
non-hygroscopic molasses-containing crystals can be easily manufactured. 
In a block disintegrating method, a massceuite containing 5-15% of water 
and having a degree of crystallization of about 10-60% is usually allowed 
to stand for 0.5-5 days so that the whole substance is crystallized out 
and solidified in blocks and the blocks are disintegrated by means of 
grinding or cutting and then dried whereupon the non-hygroscopic or hardly 
hygroscopic molasses-containing crystals can be easily manufactured. It is 
also possible that, in accordance with conventional method, an aqueous 
solution of maltitol is heated to concentrate to make the water content 
less than 5%, then seed crystals are kneaded with the resulting 
supersaturated maltitol solution in a melted state at the temperature of 
not higher than the melting point of maltitol and the kneaded mixture is 
made into various shapes to give non-hygroscopic or hardly hygroscopic 
molasses-containing crystals. 
The above-mentioned methods are described in the specification of the 
above-identified patent and, in its Examples, the following methods are 
specifically disclosed. Thus, a method in which a maltitol solution is 
concentrated to a 80% concentration and charged in an crystallizing 
vessel, 1% of powdery seed crystals of anhydrous crystalline maltitol are 
added, the mixture is made 50.degree. C. and allowed to cool with a slow 
stirring until 20.degree. C. during three days and molasses are separated 
by a centrifugal machine of a basket type to give anhydrous crystalline 
maltitol (Example 2); a method in which a maltitol solution is 
concentrated to a 88% concentration and charged in an crystallizing 
vessel, 2% of powdery crystals of anhydrous crystalline maltitol are 
added, the mixture is made at 50.degree. C., kept at that temperature for 
two hours with a slow stirring, taken out into a vat and allowed to stand 
at 20.degree. C. for four days and the crystallized and separated product 
is disintegrated by a grinder of a cutting type followed by drying to give 
molasses-containing crystal powder of anhydrous crystalline maltitol 
(Example 3); and a method in which a maltitol solution is concentrated to 
a 80% concentration, charged in a crystallizing vessel, and admixed with 
2% of molasses-containing crystal powder which contains anhydrous 
crystalline maltitol, the mixture is gradually cooled starting from 
50.degree. C. with a slow stirring, the resulting massceuite (degree of 
crystallization being 35%) is sprayed from a nozzle of 1.5 mm diameter on 
a drying tower with a pressure of 150 kg/cm.sup.2 using a high-pressure 
pump and, at the same time, hot air of 85.degree. C. is sent from the 
upper part of the drying tower to collect on a wire net conveyer placed at 
the bottom of the tower, then the crystalline powder collected on a wire 
net conveyer is gradually moved to outside of the drying tower together 
with sending hot air of 40.degree. C. from the bottom of the conveyer, the 
crystalline powder which is taken out during 40 minutes is filled in an 
aging tower and aged for ten hours to complete both crystallization and 
drying whereupon anhydrous crystalline maltitol molasses-containing 
crystalline powder is obtained (Example 4). However, all of those methods 
need long time for crystallization or for aging of maltitol crystals and, 
therefore, there is a disadvantage that it is difficult to make the 
apparatus simple and continuous. 
In the Japanese Examined Patent Publication Hei-07/14953B, there is a 
disclosure on a method for the manufacture of maltitol molasses-containing 
crystals as well. In said method, an aqueous solution of maltitol is 
continuously supplied to an extruder having a slender cooling and kneading 
zone and subjected to a continuous cooling and kneading in the presence of 
seed crystals to produce a maltitol magma and the magma is continuously 
extruded from an extruding nozzle to give maltitol molasses-containing 
crystals. Although this method is successful in terms of making the 
operations continuous but an extruder having a slender cooling zone is 
used and, in order to conduct a highly concentrating process, the 
temperature becomes inevitably high due to the viscosity. Thus, a crystal 
production is proceeded by cooling said concentrated solution for 
increasing the degree of supersaturation and the step is in such a manner 
that the seed crystals are added thereto and kneaded therewith under 
cooling and the a maltitol magma produced thereby is discharged from an 
extruding nozzle. 
However, when cooling is accompanied, a highly concentrated maltitol starch 
syrup becomes highly viscous due to a lowering of the temperature as a 
result of the cooling and, therefore, a big power is needed for conducting 
a kneading operation which results in a rise in a running cost. In 
addition, plural zones [i.e., a cooling/kneading zone for introduction of 
the material; a zone for adding and mixing the seed crystals; a zone for 
cooling and kneading after addition of the seed crystals (a maltitol magma 
producing zone); etc.] are necessary and, therefore, big equipment is 
required and, further, load of power becomes high because of an increase 
in viscosity due to cooling. Accordingly, it is predicted that making the 
size of the apparatus big for an industrial production will be difficult. 
Moreover, in the case of manufacture of a final product in a powdery 
state, steps of rough disintegration, aging, drying, etc. of the maltitol 
magma discharged from the extruding nozzle in various shapes are necessary 
and, in that case, further long time is needed for the manufacture which 
causes an increase in the manufacturing cost. 
Problems to be Solved by the Invention 
In an industrial production of sweet saccharides and the like, a reduction 
in the product cost has a very important meaning. For such a purpose, it 
is desired that all steps can be made continuously operated and the labor 
expenses can be reduced greatly and, in addition, there is a demand for a 
method wherein all of the product can be crystallized without giving 
by-products and the product is stable in terms of hygroscopicity, etc. 
In the crystallization of saccharides, it is desirable that all of the 
steps are to be made continuously operated. Such steps include a step 
where a supersaturated solution is obtained by means of concentration, a 
step where the temperature which is convenient for crystallization is 
maintained and crystallization is promoted by adding the seed crystals, an 
aging step for further growth of the crystals and, if necessary, a step 
where they are pulverized and sieved. For such a purpose, it is necessary 
to find a condition whereby each of the steps is completed within short 
time. 
The present inventors have previously developed a method for the 
manufacture of water-containing crystalline .beta.-maltose as disclosed in 
the Japanese Examined Patent Publication Hei-05/79316B, then developed a 
method for a continuous crystallization of whole of anhydrous crystalline 
.alpha.-maltose and succeeded in manufacturing it in an industrial scale 
as disclosed in the Japanese Laid-Open Patent Publication Hei-06/277100A 
and, after that, they have conducted in developing a continuous 
manufacturing method for anhydrous crystalline maltitol. 
The present inventors have had an idea that the continuous operation will 
be possible and the production cost can be significantly reduced if the 
problem that long time is needed in aging of crystals which is a 
disadvantage factor in the conventional method as disclosed in the 
Japanese Examined Patent Publication Sho-63/2439B can be solved and they 
have continued the invention on this respect. To be more specific, various 
investigations have been conducted with a target of conducting the 
following steps continuously. They are a step where a solution containing 
anhydrous maltitol is concentrated, a step where an appropriate amount of 
seed crystals is added thereto to give a supersaturated product containing 
the seed crystals (massceuite) and a step where aging is conducted for 
completing the crystallization in the massceuite. 
In a concentrating method where the material solution is made 
supersaturated in terms of anhydrous maltitol, it is possible to give a 
desired degree of concentration by the use of a concentrating apparatus of 
a thin film type and the problem is that how to complete the 
crystallization within short time. Under such a condition that long time 
is required for completing the crystallization, the volume of the 
apparatus becomes large even if making the steps continuous is successful 
and, therefore, such a method is not practical in terms of apparatus and 
economy as well. The present inventors have previously succeeded in 
continuously conducting the crystallization of the whole amount of 
anhydrous crystalline .alpha.-maltose and they have now found that 
anhydrous crystalline maltitol is crystallized more easily as compared 
with the above-mentioned one. 
Means for Solving the Problems 
The present inventors have investigated how the total steps for 
crystallization of maltitol can be reduced in terms of time and found 
that, with regard to the crystallization, it is necessary that the seed 
crystals are homogeneously mixed within short time. With this respect, 
there are many examples that, usually, an increase in the degree of 
supersaturation by cooling is adopted as the condition for crystallization 
while the present inventors have now found that it is advantageous that 
the viscosity is reduced by heating the solution of a high concentration 
at high temperature whereby the seed crystals are homogeneously dispersed 
within short time. The present inventors have further found that, when 
maltitol concentration in an aqueous solution of maltitol is concentrated 
to an extent of not lower than a certain concentration and when the 
environment for the step for aging the crystals after crystallization is 
controlled, it is now possible that time for crystallization can be 
greatly shortened and the steps can be easily made continuous. 
The present invention is characterized, based upon the above findings, in 
consisting of a heating and concentration step where a concentrating 
apparatus is used, a seed crystal adding and mixing step where the seed 
crystals are added and mixed at high temperature and a crystal aging step 
where the crystallization is completed and also in adopting specific 
operation conditions for each of those steps. 
Thus, the present invention relates to a continuous manufacturing method 
for anhydrous crystalline maltitol comprising the following steps: 
(i) a heating and concentrating step where an aqueous solution containing 
maltitol in which maltitol is a main ingredient is continuously heated and 
concentrated to give a concentrated solution having a high concentration; 
(ii) a seed crystal adding and mixing step where the seed crystals are 
added to and mixed with the above concentrated solution with heating to 
give a massceuite containing the seed crystals; and 
(iii) a crystal aging step where the massceuite is subjected to 
disintegration, mixing, stirring and transfer in an atmosphere in which 
temperature and moisture are adjusted to proceed the crystallization. 
The present invention also relates to a continuous manufacturing apparatus 
for anhydrous crystalline maltitol comprising the following means: 
(i) a heating and concentrating means where an aqueous solution containing 
maltitol is continuously heated and concentrated to give a concentrated 
solution having a high concentration; 
(ii) a seed crystal adding and mixing means where the seed crystals are 
added to the concentrated solution by keeping the temperature at not lower 
than 80.degree. C. to produce a seed crystal-containing massceuite in 
which the content of the crystals is not less than 40 w/w %; and 
(iii) a crystal aging means where the massceuite is subjected to 
disintegration, mixing, stirring and transfer in an atmosphere of 
temperature of 70-100.degree. C. and absolute humidity of 50-300 g H.sub.2 
O/kg dry air to proceed the crystallization.

BEST MODE FOR CARRYING OUT THE INVENTION 
There is no particular limitation for preparing an aqueous solution of 
maltitol used in the present invention and any of the conventionally known 
methods may be adopted. With regard to the aqueous solution of maltitol, 
it is preferred that purity of maltitol is not lower than 80 w/w % and the 
aqueous solutions of maltitol obtained by the following method may be 
used. Thus, hydrogenation is conducted by adding a Raney nickel catalyst 
to a highly pure maltose obtained by (1) a method where gelatinized or 
liquefied starch is treated with .beta.-amylase and the resulting maltose 
is separated from the high-molecular dextrin to collect a highly pure 
maltose (Japanese Examined Patent Publications Sho-56/11437B and 
Sho-56/17078B), (2) a method where gelatinized and liquefied starch is 
treated with starch debranching enzyme (such as isoamylase and 
pullulanase) and .beta.-amylase to give a highly pure maltose, or (3) a 
method where contaminating saccharides such as maltotriose contained in 
the highly pure maltose prepared by the above methods are removed by a 
column chromatography method using a strongly acidic cationic ion exchange 
resin of a salt type disclosed, for example, in the Japanese Laid-Open 
Patent Publication Sho-58/23799A whereby the purity of maltose is made 
higher. Alternatively, an aqueous solution of maltitol is subjected to 
various fractionating methods (Japanese Examined Patent Publication 
Hei-02/11599B) and the resulting highly pure maltitol may be used for this 
purpose. 
As hereunder, optimum conditions for each of the steps of the present 
invention will be illustrated in detail. 
Firstly, in a concentrating step, it is preferred to use a continuous 
concentrating machine of a thin film type such as a centrifugal thin-film 
concentrating apparatus and a vertical thin-film concentrating apparatus 
although the present invention is not limited thereto. Concentration of 
maltitol is adjusted using such a concentrating apparatus. The term 
"concentration of maltitol" used here means the percentage by weight of 
pure maltitol in the concentrated solution [i.e., (concentration of 
maltitol)=(concentration of the solid in the concentrated 
solution).times.(purity of maltitol); for example, when purity of maltitol 
in an aqueous solution of maltitol of 95 w/w % solid concentration is 96 
w/w %, then the concentration of maltitol is 95.times.0.96=91.2 w/w %] 
and, in the present invention, it is preferred to adjust this 
concentration to 78-98 w/w %. 
Thus, the concentration of maltitol means that, when purity of maltitol in 
the aqueous solution of maltitol is low, a highly concentrating operation 
is necessary while, in the case of a maltitol solution of a high purity, a 
lowly concentrating operation will do. Practically however, when purity of 
maltitol is as low as not higher than 80 w/w %, it is to be concentrated 
to an extent of degree of concentration of around 98 w/w % for making the 
concentration of maltitol 78 w/w % or more and, in that case, the process 
becomes very slow both in terms of manufacture and crystallizing speed due 
to its high viscosity and that is contrary to the object of the present 
invention. Measurement of a concentration of a solid at that time is 
conducted in such a manner that water content (w/w %) is measured by a 
Karl-Fischer method and said water content (w/w %) is deducted from 100 to 
give a concentration of the solid (w/w %). Incidentally, moisture content 
(based upon a dry substance) is calculated from the water content by a 
Karl-Fischer method. Purity of maltitol is analyzed by means of a high 
liquid chromatography by a conventional method. 
With regard to the next step of adding and mixing the seed crystals, it is 
necessary to maintain a high temperature in this step so that the seed 
crystals are well dispersed in a concentrated solution within short time 
with heating and further that an increase in viscosity during the mixing 
and dispersing step is suppressed. In addition, it is preferred that, 
during this step, there is substantially no evaporation of water. When 
concentration proceeds as a result of evaporation of water, the viscosity 
becomes high and a very big driving force is necessary for the apparatus 
and that is not recommended. Moreover, mixing and dispersing of the seed 
crystals are deteriorated and, as a result, the crystallizing time in the 
crystal aging step becomes long. Thus, in view of those, an excessive 
concentration is not preferred. Usually, the moisture content of the 
massceuite is preferably at least 3 w/w %. 
Further, in this step, a heating apparatus by means of a jacket is 
necessary for preventing the deterioration of a mixing and dispersing 
ability as a result of an increase in viscosity due to lowering of the 
temperature and it is important to keep the low viscosity for dispersing 
and mixing of the seed crystals within short time. The apparatus which is 
preferred for such a purpose is a vessel-fixing type or a horizontal axis 
or horizontal double axis type generally used for kneading a small amount 
of powder into a highly viscous substance or colloidal substance and is a 
continuous kneader of a tightly closed type equipped with a heating device 
in a ribbon system, a screw extrusion system, a self-cleaning system, a 
paddle system, etc. It is also possible to use by selecting such a one 
that is suitable for continuous operation from the apparatuses such as 
kneader or mixer used for mixing or kneading. 
Supplement of the seed crystals may be conducted by a method where crystal 
powder is quantitatively supplied either continuously or intermittently at 
the inlet of the seed crystal mixer or by a method where a part of the 
massceuite in which crystallization is proceeded is returned from the 
outlet of the seed crystal mixer to the inlet of the seed crystal mixer. 
In that case, it is of course necessary to pay due attention that the 
temperature does not lower. The seed crystals used are prepared from 
anhydrous crystalline maltitol and molasses-containing anhydrous 
crystalline maltitol. The content of the anhydrous crystalline maltitol in 
this molasses-containing crystals is important since it controls the 
crystallizing speed and it goes without saying that the higher the 
content, the higher the crystallizing speed. The amount of the seed 
crystals to be added may be 0.1 w/w % or more and, although an increase in 
the amount results in a proportional increase in volume affecting the 
productivity, that also somewhat relates to the speed of crystal 
separation and, accordingly, when it is desired to make the whole 
apparatus compact for a continuous operation for short time which is an 
object of the present invention, it is preferred to add 5-30 w/w % of the 
seed crystals to the solid in the concentration solution. 
During the course of passing of the seed crystals through the seed crystal 
mixer, it is the utmost factor that the seed crystals are homogeneously 
dispersed in the concentrated solution and, during the course of 
introducing the crystallization to the next crystal aging step, water in 
the massceuite should not be evaporated substantially. In the common 
methods (e.g., Japanese Examined Patent Publications Sho-63/2439B and 
Hei-07/14953B), a crystallizing step consists of separation of crystals by 
controlling the degree of supersaturation as a result of cooling the 
temperature for crystallization. However, in the present invention, degree 
of concentration is made high and the crystallizing temperature is made 
rather high to make the viscosity low so that the seed crystals are well 
dispersed by a mechanical stirring whereby this step is completed within 
very short time. It is particularly characteristic in the step of adding 
and mixing the seed crystals that the temperature is made high, preferably 
at 80.degree. C. or higher. Incidentally, when this seed crystal adding 
and mixing step is completed and is just coming to the next step, the 
content of the crystals in the massceuite should be at least 40 w/w %. 
The next step is an aging step for the crystals which is the most important 
point in the present invention. In the massceuite mixed with the seed 
crystals, crystallization starts at several minutes after the mixing to 
give white solid blocks (massceuite). In the crystal aging step, the 
blocks are subjected to disintegration, stirring, mixing and transfer 
(convey) in an atmosphere of a high temperature and a certain humidity 
whereby they arrives at the outlet of the crystal aging machine together 
with a progress of the crystallization. Convenient crystal aging machine 
used here is that which is a continuous kneader type and has an internal 
space and it is necessary to use an apparatus which is to be able to 
disintegrate, mix, stir and transfer the content therein. Preferred 
apparatus is in such a structure that the content therein is transferred 
forward and particularly preferred one is in such a structure that, when 
the content is blocked, it is disintegrated as fine as possible so that 
homogeneous mixing and stirring are possible. 
In this step, an apparatus which is a kind of a two-axial paddle type and 
in which the content can be disintegrated, mixed, stirred and transferred 
may be used. In the inner part of said apparatus, two rotating axes which 
rotate and engage each other to inner sides are equipped and, around said 
rotating axes, paddles are attached and located with a certain interval so 
that the paddles of the opposite axes bite each other. Function of the 
paddle is not only to transfer the content forward but also to play a role 
for disintegrating the solid massceuite, if any, to evaporate the water in 
the internal part of the block. 
In the present invention, it is preferred that the atmosphere in the 
crystal aging machine is controlled to such an extent of temperature of 
70-100.degree. C. and absolute humidity of 50-300 g H.sub.2 O/kg dry air. 
For such a purpose, it is necessary that heated and moistened air where 
temperature and humidity are adjusted as such is introduced into the 
crystal aging machine so that said machine can keep such an atmosphere. In 
this step, when crystallization in the massceuite proceeds, water is 
evaporated to some extent and the moisture content decreases to not more 
than 3 w/w %. When too quick drying is conducted at the initial stage of 
crystallization (for example, to an extent of moisture content of 1 w/w % 
or less), progress of the crystallization becomes significantly slow 
whereby an object of the present invention cannot be achieved. 
In addition, it is preferred that the atmosphere in the inner part of the 
above crystal aging machine is at a relatively high absolute humidity at 
high temperature while, at low temperature, it is at a relatively low 
absolute humidity. When coloring property and crystallizing rate are taken 
into consideration, it is most preferred that a moistened hot air which is 
adjusted to the temperature of 85-95.degree. C. and the absolute humidity 
of 100-200 g H.sub.2 O/kg dry air is supplied into the inner part of the 
crystal aging machine. Even when the absolute humidity is made 300 g 
H.sub.2 O/kg dry air, aging of the crystals proceeds but their surface 
seems to be wet partially and the moisture content of the product after 
completion of the crystal aging is high whereby drying is necessary. With 
regard to a method of adjusting the heated and moistened air, that which 
has been commonly used may be adopted and, for example, water in such 
amount that corresponds to said humidity is sprayed to a heated hot air 
from a two-fluid nozzle. 
Like in the preceding step where the crystallization is promoted by 
adjusting the crystallizing condition to within a maltitol concentration 
range of 78-98 w/w %, an object of adjustment of the atmosphere in the 
inner space of the crystal aging machine is that, during the progress of 
crystallization in this aging step, anhydrous crystals of maltitol are 
substantially separated out whereby, in other noncrystalline parts, water 
content becomes high and solid concentration lowers and, therefore, 
promotion of aging of the crystals is resulted if the maltitol 
concentration in the parts other than that where the crystal concentration 
lowers is maintained within a range of 78-98 w/w %. For increasing the 
maltitol concentration, further drying and concentration are necessary 
but, when only dry and hot air is supplied, water is quickly evaporated to 
result in a syrupy appearance whereupon the crystallization is 
significantly retarded. 
Thus, in the present invention, the atmosphere in the inner part of this 
crystal aging machine is made in a condition with suitable temperature and 
humidity by means of the above controlled humid and hot air whereby it is 
now possible that a drying speed meeting with the progress of 
crystallization during the crystal aging step is achieved and that 
anhydrous crystalline maltitol and molasses-containing anhydrous 
crystalline maltitol powder are obtained within very short time. That is 
greatly different from the conventional method where crystals are 
separated out by raising the degree of super-saturation by means of 
cooling which is a common method for promoting the crystallization of 
saccharides. 
Mixing, stirring and disintegration are essential in this aging step and, 
if humid and hot air is supplied under the condition of being allowed to 
stand, the surface becomes to a state of as if being melted and the 
progress of crystallization is slow whereby long time is needed. Even when 
the material is transferred using a belt conveyer or the like in an 
atmosphere of the above-mentioned temperature and humidity, the progress 
of crystallization is still slow and, accordingly, the necessity of 
mixing, stirring and disintegration has now been ascertained. If an 
additional drying step is necessary, hot and dry air is sent into the 
device used in this aging step to make the moisture content 1 w/w % or 
less whereby stable anhydrous crystalline maltitol and molasses-containing 
anhydrous crystalline maltitol are obtained. 
EXAMPLES 
The present invention will now be more specifically illustrated by way of 
the following examples although the present invention is not limited 
thereto. 
At first, the experimental examples concerning the decision of the 
conditions for the steps--heating and concentration, addition and mixing 
of seed crystals, and aging of crystals--which are the three important 
steps in the present invention will be mentioned as follows. 
From the experiences in the past for the industrial manufacture of 
anhydrous crystalline maltose, various conditions have chosen with an 
object of conducting the process within short time on a continuous basis 
and, taking the conditions, etc. of the machines and apparatuses, a target 
was set that a step of addition and mixing of the seed crystals, a step of 
aging the crystals and both steps are to be completed within about 15 
minutes, about 30 minutes and at least one hour, respectively. In order to 
obtain stable anhydrous crystalline maltitol, a target for the step of 
addition and mixing of the seed crystals was set so as to make the content 
of crystals after completion of the step not less than 40 w/w % while a 
target for the step of aging of the crystals was set so as to make the 
melting point of the product not lower than 120.degree. C. or, preferably, 
not lower than 130.degree. C. 
Experimental Example 1 
A seed crystal mixer which will be mentioned in the Examples later was used 
and 10 w/w % (to the solid in the concentrated solution) of seed crystals 
were continuously added to and mixed with the concentrated solution 
whereupon the content of massceuite after the step of addition and mixing 
of the seed crystals at 110.degree. C. for 15 minutes was measured. 
Table 1 shows the result of the massceuite crystal content discharged from 
the step of addition and mixing of the seed crystals where concentration 
of maltitol was changed by changing the concentration of the concentrated 
solution using the samples having varied maltitol purity. 
TABLE 1 
______________________________________ 
Relation between Purity/Concentration of Maltitol 
and Crystal Content of Massceuite 
after a Step of Addition/Mixing of Seed Crystals 
Concn of Concen- Crystal Content in 
Malti- Concen- 
tration 
the Substance Dis- 
tol trated 
of charged from a Seed 
Purity Solution 
Maltitol 
Crystal Addition/ 
(w/w %) (w/w %) 
(w/w %) 
Mixing Step (w/w %) 
______________________________________ 
94.1 80.0 75.3 30.2 
78.5 96.0 
75.4 
30.7 
84.0 90.1 
75.7 
31.5 
80.1 95.1 
76.2 
31.5 
90.1 85.0 
76.6 
32.2 
98.5 78.1 
76.9 
35.0 
78.5 98.0 
76.9 
36.0 
80.0 97.0 
77.6 
38.2 
94.1 83.0 
78.1 
39.5 
98.5 80.1 
78.9 
41.2 
90.1 88.1 
79.4 
42.5 
84.0 95.0 
79.8 
43.2 
84.0 97.1 
81.6 
43.7 
98.5 83.1 
81.9 
43.8 
94.1 88.0 
82.8 
44.2 
90.1 93.0 
83.8 
45.3 
98.5 88.0 
86.7 
46.6 
90.1 97.1 
87.5 
47.8 
94.1 93.0 
87.5 
48.2 
94.1 97.0 
91.3 
46.7 
98.5 93.0 
91.6 
50.5 
98.5 97.0 
95.5 
45.1 
______________________________________ 
It is apparent from the above result that, in the concentrated solution to 
be supplied in the step of mixing and crystallization of seed crystals, 
not less than 78 w/w % is necessary as the concentration of maltitol and 
not less than 80 w/w % is necessary as the purity of maltitol. When such a 
condition is satisfied, the crystal content in the discharged substance 
from the seed crystal mixer becomes not less than 40 w/w % and, as a 
result, the next crystal aging step can be completed within short time 
whereby an object of the present invention for making the steps short and 
continuous is possible. 
Experimental Example 2 
Then, the relation between the atmosphere (temperature and humidity) in the 
crystal aging machine and the melting point of the aged product in the 
crystal aging step was investigated. 
A maltitol solution having a maltitol purity of 93 w/w % was concentrated 
to an extent of a maltitol concentration of 87.4 w/w %, supplied to a seed 
crystal mixer mentioned in the Example at 120.degree. C. and maltitol 
crystals of 98 w/w % purity as the seed crystals were added thereto in an 
amount of 10 w/w % to the solid in the concentrated solution and the 
mixture was mixed by a seed crystal mixer for 15 minutes to give a 
massceuite containing 48 w/w % of crystals. Another massceuite containing 
38 w/w % of crystals was prepared by the same method as well. They were 
continuously supplied to a crystal aging machine, temperature and humidity 
of the atmosphere at that time were changed and the melting point of the 
substance discharged therefrom after aging for 30 minutes was measured. 
The result is given in Table 2. 
TABLE 2 
______________________________________ 
Relation between Atmosphere in Crystal Aging Machine 
and Melting Point of the Aged Product 
Crystal Humid- Moisture 
Melting 
Content Tem- 
ity Point ofof 
before per- 
(g H.sub.2 O/ 
Aged 
Aged 
Aging ature 
Product 
Product 
(w/w %) (.degree. C.) 
air) 
(w/w %) 
(.degree. C.) 
______________________________________ 
48 80 50 1.3 124 
48 100 
125 
48 150 
122 
48 1.0 
119 
48 100 
130 
48 150 
137 
48 200 
134 
48 100 
119 
48 150 
125 
48 200 
133 
48 250 
135 
48 300 
131 
48 400 
119 
48 500 
118 
38 150 
113 
38 200 
114 
38 200 
113 
38 250 
110 
______________________________________ 
Melting point of the product is one of the indexes for crystallization of 
anhydrous maltitol and, under the present condition where the maltitol 
purity was 93 w/w %, the product having a melting point of not lower than 
120.degree. C. showed low hygroscopicity and, therefore, "not lower than 
120.degree. C." was adopted for the completion of aging of the product as 
the criteria for passing the test. 
It is apparent from the above result that, when the crystal content of 
massceuite upon supplying to a crystal aging machine is 38 w/w %, a 
product having a melting point of not lower than 120.degree. C. is not 
obtained and that, with regard to the absolute humidity of the atmosphere, 
when that condition is 50-150 g H.sub.2 O/kg dry air, a product having a 
melting point of not lower than 120.degree. C. is obtained if the 
temperature is as relatively low as 80.degree. C. but the higher the 
humidity, the somewhat lower the melting point. It is also noted that a 
high-melting point product is obtained at 90.degree. C. if the humidity is 
100-200 g H.sub.2 O/kg dry air and at 95.degree. C. if the humidity is 
200-300 g H.sub.2 O/kg dry air. It is apparent that no desired product is 
obtained when the humidity is higher or lower than mentioned above. 
Accordingly, it is clear that the atmosphere in the inner area of the 
crystal aging machine is to be controlled at 70-100.degree. C. and 50-300 
g H.sub.2 O/kg dry air (absolute humidity) and, within such a range, it is 
necessary that the lower the temperature, the humidity is to be kept lower 
and also that the higher the temperature, the humidity is to be kept 
higher. 
Example 1 
A starch slurry prepared from corn starch was mixed with a bacterial 
.alpha.-amylase and gelatinized and liquefied by a conventional method and 
then saccharified by a soybean .beta.-amylase and pullulanase (both 
manufactured by Nagase Seikagaku), the resulting saccharified solution was 
concentrated using a vacuum concentrating machine to an extent of 60 w/w % 
and subjected to a chromatographic separation by Na type cation exchange 
resin (Japanese Examined Patent Publication Hei-05/2320B), the resulting 
eluate containing maltose (94.0 w/w % of maltose, 1.7 w/w % of glucose, 
2.2 w/w % of maltotriose and 2.1 w/w % of other oligosaccharides; 31 w/w % 
of solids) was hydrogenated using a Raney nickel catalyst by a 
conventional method and the resulting maltitol solution mainly comprising 
maltitol (93.0 w/w % of maltitol, 2.5 w/w % of sorbitol, 2.6 w/w % of 
maltotriitol and 1.9 w/w % of other sugar alcohols) was treated with a 
continuous concentrating apparatus of a thin film type as shown in FIG. 1 
to give a concentrated solution having a moisture content of 6.4 w/w % 
where the concentration of maltitol was 87.0 w/w %. Temperature of the 
concentrated solution and the viscosity at that time were 130.degree. C. 
and 0.25 Pa.s, respectively. This concentrated solution in a hot state was 
continuously supplied to a seed crystal mixer and, at the same time, 10 
w/w % (to the solid content in the concentrated solution) of anhydrous 
crystalline maltitol powder (purity: 95 w/w %) as seed crystals were added 
using a quantitative feeder. This seed crystal mixer was kept at high 
temperature by heating its jacket using a steam of about 110.degree. C. 
(142 kPa) . Retention time was 15 minutes and moisture content and crystal 
content in the discharged substance were 6.0 w/w % and 48 w/w %, 
respectively. Then this discharged substance from the seed crystal mixer 
was continuously supplied to a crystal aging machine and the atmosphere in 
the inner part of the crystal aging machine was made in an almost 
controlled humid and hot condition by supplying a moistened and heated air 
adjusted at the temperature of 90.+-.2.degree. C. and the humidity of 130 
g H.sub.2 O/kg dry air at a flow rate of 1500 liters per minute at a 
constant basis to 50 liters of inner space of the crystal aging machine. 
The crystal aging machine used is a two-axial paddle type, is capable of 
mixing, disintegrating and conveying and is equipped with a jacket of 1400 
mm length, 250 mm width and 100 liter inner volume. Its inner area is 
equipped with two rotating axes which rotate in such a manner that they 
engage each other to the inner side and, around the rotating axes, paddles 
are located with some intervals so that the paddles of the encountering 
axes are engaged each other. The function of the paddles is not only that 
the content therein is moved forward but also that the solidified 
massceuite, if any, is disintegrated whereby the paddles have a role of 
evaporating the water in the inner side of the blocks. The number of 
rotations of the paddle is 30 rpm. 
In the inner part of this crystal aging machine kept at the above-mentioned 
atmosphere condition, the massceuite discharged from the seed crystal 
mixer was disintegrated as it moved forward while water was appropriately 
evaporated depending upon crystallizing speed and, after the retention for 
about 30 minutes, the discharged substance became a crystalline one 
containing 1.6 w/w % of water. This was ground to give powder which passed 
a sieve of 10 mesh. Its melting point was as high as 130.degree. C. and 
the product was very stable powder having little hygroscopicity even when 
allowed to stand at ambient temperature. All of the above steps after the 
concentrating step were able to be conducted within as short as about one 
hour and are convenient for a continuous production. 
Example 2 
A maltitol solution (containing 92.0 w/w % of maltitol, 2.3 w/w % of 
sorbitol, 3.3 w/w % of maltotriitol and 2.4 w/w % of other sugar alcohols) 
obtained by the same method as mentioned in Example 1 was concentrated by 
a double effect boiler until the solid concentration became 50 w/w %, then 
supplied to a continuous concentrating apparatus of a thin film type and 
made into a concentrated solution containing 4.2 w/w % of water and 88.1 
w/w % of maltitol. Temperature and viscosity of the concentrated solution 
at that time were 139.degree. C. and 1.4 Pa.s, respectively. This 
concentrated solution in a hot state was continuously supplied to a seed 
crystal mixer and, at the same time, 20 w/w % (to the solid content in the 
concentrated solution) of molasses-containing anhydrous crystalline 
maltitol powder (purity: 93 w/w %) were added as seed crystals whereupon 
crystallization is conducted with a retention time of 15 minutes to give a 
product containing 4.0 w/w % and 45.3 w/w % of crystals. This was 
continuously supplied in a crystal aging step by the same manner as in 
Example 1 to conduct the aging. The aging condition was that a humid and 
hot air having a temperature of 90.degree. C. and an absolute humidity of 
180 g H.sub.2 O/kg dry air was supplied by the same flow rate condition as 
in Example 1. Aging was conducted where the inner area of the crystal 
aging machine was substantially under said atmospheric condition and the 
crystalline product obtained by a retention time of 45 minutes contained 
0.7 w/w % of water. This was further treated with a grinder to give powder 
passing through a sieve of 10 mesh. The product was in a powdery state 
which contained stable crystals having a melting point of 134.degree. C. 
All steps after the concentrating step were completed within as short as 
about 75 minutes whereby they can be predominantly applied in continuous 
production. 
Example 3 
A maltitol solution (containing 93.2 w/w % of maltitol, 2.2 w/w % of 
sorbitol, 3.0 w/w % of maltotriitol and 1.6 w/w % of other sugar alcohols; 
solid content: 30 w/w %) obtained by the same manner as in Example 1 was 
treated with a continuous concentrating apparatus of a thin film type to 
give a concentrated solution containing 5.2 w/w % of water and 88.4 w/w % 
of maltitol. This solution in a hot state was supplied to a seed crystal 
mixer where the jacket was kept at high temperature by circulating a hot 
water of 95.degree. C. therein together with continuous addition of 10 w/w 
% (to the solid content in the concentrated solution) of 
molasses-containing anhydrous crystalline maltitol powder as seed crystals 
and, after the retention for about 15 minutes, a massceuite containing 4.9 
w/w % of water and 46.5 w/w % of crystals was obtained. This was 
continuously supplied to a crystal aging machine which was same as that 
used in Example 1, a humid and hot air controlled at a temperature of 
98.degree. C. and an absolute humidity of 250 g H.sub.2 O/kg dry air was 
continuously supplied thereto, a crystal aging was conducted in an 
atmosphere kept at that condition and, after the retention for about 30 
minutes, a crystalline product containing 1.8 w/w % of water was obtained. 
This was treated with a grinder to give a powdery product passing through 
a sieve of 10 mesh and dried with a hot air drier at 80.degree. C. for 30 
minutes to give crystalline powder containing 0.6 w/w % of water. This was 
a very stable crystalline powder having a melting point of 137.degree. C. 
All steps after the concentrating step were completed within as short as 
about 90 minutes whereby they can be predominantly applied in a continuous 
production. 
Comparative Example 1 
A comparative experiment was conducted using the apparatus used in Example 
1 according to a method mentioned in the Japanese Examined Patent 
Publication Hei-07/14953B. Thus, the same aqueous solution of maltitol as 
in Example 1 was used, degree of concentration and temperature of the 
supplied solution in Example 1 (87.0 w/w % and 130.degree. C.) were 
changed to 93.8 w/w % and 98.degree. C., respectively, according to the 
description in the Example of said Japanese patent and, when the 
temperature of the substance was cooled down to 60.degree. C., about 26 
w/w % of seed crystals were added thereto and mixed therewith to give 
maltitol magma. However, during the process of cooling, viscosity became 
considerably high and mixing and conveying did not so smoothly take place 
as those in the examples of the present invention but the product was sent 
to the crystal aging machine in such a state that the mixing of the seed 
crystals was still non-homogeneous. Cooling was further conducted in the 
inner area of the crystal aging machine down to about 40.degree. C. but, 
as crystals were separated out and temperature was lowered, there was a 
further increase in the viscosity whereupon mixing, disintegration and 
transfer did not take place smoothly. Thus, the magma became a block, the 
transfer did no proceed smoothly, the load of the power for the mechanical 
stirring became large and, finally, operation of the machine stopped. The 
content was taken out, spread on a vat made of stainless steel with 
pulverizing by hand as fine as possible and allowed to stand in a 
thermostat of 60.degree. C. for about one hour to let it crystallize. 
Although anhydrous crystals were obtained, the melting point was 
118.degree. C. which was not so favorable and, in addition, there is no 
possibility at all for a continuous operation in an industrial scale. In 
view of the above, the conclusion is that a method where crystals are 
separated out by making the solution supersaturated by cooling results in 
a big load on the machines and apparatuses and that said method is not 
suitable for conducting it in an expanded scale.