U.S. patent application number 09/993859 was filed with the patent office on 2002-05-09 for process for the preparation of a maltose-rich syrup.
Invention is credited to Caboche, Jean-Jacques.
Application Number | 20020055150 09/993859 |
Document ID | / |
Family ID | 9534591 |
Filed Date | 2002-05-09 |
United States Patent
Application |
20020055150 |
Kind Code |
A1 |
Caboche, Jean-Jacques |
May 9, 2002 |
Process for the preparation of a maltose-rich syrup
Abstract
The present invention relates to a process for the preparation
of a maltose-rich syrup comprising the steps of (a) carrying out
liquefaction of a starch milk; (b) carrying out saccharification of
the liquefied starch milk in the presence of a .beta.-amylase and
at least one debranching enzyme selected from the group comprising
pullulanases and isoamylases; (c) carrying out molecular sieving of
the liquefied and saccharified starch milk so as to collect a
fraction enriched with maltose and a fraction enriched with
glucose; and (d) bringing said fraction enriched with maltose into
contact with a maltogenic .alpha.-amylase with a view to obtaining
a maltose-rich syrup.
Inventors: |
Caboche, Jean-Jacques;
(Drouvin Le Marais, FR) |
Correspondence
Address: |
HENDERSON & STURM LLP
1213 MIDLAND BUILDING
206 SIXTH AVENUE
DES MOINES
IA
50309-4076
US
|
Family ID: |
9534591 |
Appl. No.: |
09/993859 |
Filed: |
November 14, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09993859 |
Nov 14, 2001 |
|
|
|
09473381 |
Dec 28, 1999 |
|
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Current U.S.
Class: |
435/95 ;
536/123.13 |
Current CPC
Class: |
C12P 7/18 20130101; C12P
19/22 20130101; C12P 19/14 20130101 |
Class at
Publication: |
435/95 ;
536/123.13 |
International
Class: |
C12P 019/22; C07H
003/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 29, 1998 |
FR |
98 16539 |
Claims
What is claimed is:
1. A process for the preparation of a maltose-rich syrup comprising
the successive steps of: (a) carrying out liquefaction of a starch
milk; (b) carrying out saccharification of the liquefied starch
milk in the presence of a .beta.-amylase and at least one
debranching enzyme selected from the group comprising pullulanases
and isoamylases; (c) carrying out molecular sieving of the
liquefied and saccharified starch milk so as to collect a fraction
enriched in maltose and a fraction enriched in glucose; (d)
bringing said fraction enriched with maltose into contact with a
maltogenic .alpha.-amylase in order to obtain a maltose-rich syrup;
and (e) crystallizing the maltose-rich syrup in order to obtain a
crystallized maltose.
2. The process of claim 1 further including the step of
hydrogenating the maltose-rich syrup in order to obtain a maltitol
rich syrup.
3. The process of claim 1 further including the step of
crystallizing the maltitol rich syrup in order to obtain a
crystallized maltitol.
4. The process of claim 1 further including the steps of: (a)
crystallizing the maltitol-rich syrup; (b) carrying out molecular
sieving of the crystallization mother liquors so as to obtain a
maltitol-rich fraction and a maltitol-poor fraction; (c) recycling
said maltitol-rich fraction upstream of the crystallization step;
(d) carrying out acid and/or enzymatic hydrolysis of said
maltitol-poor fraction; (e) carrying out hydrogenation of said
hydrolyzed maltitol-poor fraction.
5. Crystallized maltose obtained by crystallizing a maltose-rich
syrup as obtained according to claim 1.
6. Maltitol-rich syrup obtained by hydrogenating a maltose-rich
syrup as obtained according to claim 1.
7. Crystallized maltitol obtained by hydrogenating a maltose-rich
syrup as obtained according to claim 1 and then crystallizing the
thus obtained maltitol-rich syrup.
8. Crystallized maltitol obtained by hydrogenating a maltose-rich
syrup as obtained according to claim 1 and then crystallizing the
thus obtained maltitol-rich syrup.
9. A process for the preparation of a maltose-rich syrup comprising
the successive steps of: (a) carrying out liquefaction of a starch
milk; (b) carrying out saccharification of the liquefied starch
milk in the presence of a .beta.-amylase; (c) carrying out
molecular sieving of the liquefied and saccharified starch milk so
as to collect a fraction enriched in maltose and a fraction
enriched in glucose; (d) bringing said fraction enriched with
maltose into contact with a maltogenic .alpha.-amylase and at least
one debranching enzyme selected from the group comprising
pullulanases and isoamylases in order to obtain a maltose-rich
syrup; and (e) crystallizing the maltose-rich syrup in order to
obtain a crystallized maltose.
10. The process of claim 9 further including the step of
hydrogenating the maltose-rich syrup in order to obtain a maltitol
rich syrup.
11. The process of claim 9 further including the step of
crystallizing the maltitol rich syrup in order to obtain a
crystallized maltitol.
12. The process of claim 9 further including the steps of: (a)
crystallizing the maltitol-rich syrup; (b) carrying out molecular
sieving of the crystallization mother liquors so as to obtain a
maltitol-rich fraction and a maltitol-poor fraction; (c) recycling
said maltitol-rich fraction upstream of the crystallization step;
(d) carrying out acid and/or enzymatic hydrolysis of said
maltitol-poor fraction; and (e) carrying out hydrogenation of said
hydrolyzed maltitol-poor fraction.
13. Crystallized maltose obtained by crystallizing a maltose-rich
syrup as obtained according to claim 9.
14. Maltitol-rich syrup obtained by hydrogenating a maltose-rich
syrup as obtained according to claim 9.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Divisional patent application of U.S.
patent application Ser. No. 09/473,381 filed Dec. 28, 1999, the
disclosure of which is being incorporated herein by reference in
its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to a process for the preparation of a
maltose-rich syrup. It also relates to the use of a maltose-rich
syrup obtained by the process according to the present invention
for the preparation of a maltitol-rich syrup. It also relates to
the use of a maltose-rich syrup obtained by the process according
to the present invention for the preparation of crystallised
maltitol.
[0004] 2. Description of the Prior Art
[0005] Processes by which maltose-rich syrups can be obtained are
already well known. These processes include, in particular, the one
described by HODGE and co-workers in "Cereal Chemistry" no. 25,
pages 19-30, January 1948 and which comprises a step involving the
precipitation of limit dextrins by alcoholic solutions, and the one
described by WOLFROM and THOMPSON in "Methods in carbohydrate
chemistry", 1962, pages 334-335.
[0006] Other processes for the preparation of maltose-rich syrups
have also been proposed comprising a step involving adsorption of
dextrins over carbon (U.S. Pat. No. 4,194,623), a step involving
chromatography over zeolites or cationic or anionic resins
(FR-A-2.510.581), a step involving ultrafiltration of maltose
syrups (U.S. Pat. No. 4,429,122), the combined use of several
different enzymes namely an .alpha.-amylase, a .beta.-amylase and
an isoamylase or a pullulanase (FR-A-2.012.831).
[0007] This latter method has numerous advantages over the previous
ones. Nevertheless, it suffers from certain disadvantages
including, in particular, the fact that the saccharification
operations have to be carried out with very low dry matter contents
of the order of 20 g/l in order to obtain maximum effectiveness of
hydrolysis with enzymes.
[0008] The document FR-A-2.000.580 describes a process for the
preparation of a syrup with a high maltitol content by
hydrogenation of a syrup with a high maltose content which is
obtained by liquefaction of a starch milk with a low dry matter
content to a dextrose equivalent of less than 2, the product thus
obtained being saccharified under the action of specific
enzymes.
[0009] This process is expensive, has a mediocre yield and gives
rise to problems of bacterial contamination and phenomena of
retrogradation of the amylose. Moreover, the syrup obtained
contains proportions of polymers with degrees of polymerisation
(DP, in the description hereinafter) greater than or equal to 4,
which are troublesome.
[0010] More recently, the document U.S. Pat. No. 5,141,859 proposed
a process for the preparation of a syrup with a high maltose
content employing two successive saccharification steps. This
document advocates, in fact, a process comprising a first
saccharification step in the presence of a .beta.-amylase and a
subsequent saccharification step in the presence of a maltogenic
.alpha.-amylase. According to this document, the maltogenic
.alpha.-amylase is used after the first saccharification step to
.beta.-amylase to hydrolyse the oligosaccharides (from DP3 to DP7)
and essentially the maltotriose (trisaccharide) to maltose and
glucose.
[0011] Although the use of maltogenic .alpha.-amylase makes it
possible, effectively and advantageously, to lower the maltotriose
proportion by hydrolysis of the latter to maltose and glucose, it
nevertheless has the major disadvantage of generating large
quantities of glucose and possibly sorbitol in the event of
hydrogenation of the hydrolysates. In fact, a large proportion of
glucose originating from the hydrolysis of maltotriose by the
maltogenic .alpha.-amylase is added to the residual glucose
obtained after saccharification of the liquefied starch milk.
[0012] These large quantities of glucose, therefore of sorbitol
after hydrogenation, make the crystallisation of maltitol more
difficult and lead to a reduction in the crystal content, making
these crystals ill-suited to certain applications such as, for
example, chocolate production.
[0013] Moreover, the persistence of free glucose or sorbitol in the
maltose or maltitol syrups bring about other disadvantages such as
a reduction in the viscosity and equilibrium moisture content of
the products in which they are incorporated as sugar
substitutes.
[0014] Inasmuch as there is a growing interest in products with a
very high maltose content, there is a need for considerable
research with a view to developing an economic and extremely
reliable process for obtaining such products.
BRIEF SUMMARY OF THE INVENTION
[0015] In an extremely simple and particularly effective manner
with regard to all the proposals to date, the present invention
discloses that syrups with a very high maltose content could be
prepared by carrying out molecular sieving of a liquefied and
saccharified starch milk so as to collect a fraction enriched with
maltose and a fraction enriched with glucose, then bringing said
fraction enriched with maltose into contact with a maltogenic
.alpha.-amylase.
[0016] The invention proposes, therefore, a process for the
preparation of a maltose-rich syrup comprising the successive steps
consisting in:
[0017] (a) carrying out liquefaction of a starch milk;
[0018] (b) carrying out saccharification of the liquefied starch
milk in the presence of a .beta.-amylase and at least one
debranching enzyme selected from the group comprising pullulanases
and isoamylases;
[0019] (c) carrying out molecular sieving of the liquefied and
saccharified starch milk so as to collect a fraction enriched with
maltose and a fraction enriched with glucose;
[0020] (d) bringing said fraction enriched with maltose into
contact with a maltogenic .alpha.-amylase with a view to obtaining
a maltose-rich syrup.
[0021] The invention also proposes a process for the preparation of
a maltose-rich syrup comprising the successive steps consisting
in:
[0022] (a) carrying out liquefaction of a starch milk;
[0023] (b) carrying out saccharification of the liquefied starch
milk in the presence of a .beta.-amylase;
[0024] (c) carrying out molecular sieving of the liquefied and
saccharified starch milk so as to collect a fraction enriched with
maltose and a fraction enriched with glucose;
[0025] (d) bringing said fraction enriched with maltose into
contact with a maltogenic .alpha.-amylase and at least one
debranching enzyme selected from the group comprising pullulanases
and isoamylases with a view to obtaining a maltose-rich syrup.
[0026] The process for the preparation of a maltose syrup which is
the object of the present invention is based in fact on a simple
observation which has been neglected hitherto whereby the action of
a specific enzyme on a given substrate is effective only if the
characteristics as such of the substrate effectively permit the
action thereof.
[0027] In the present case, an effective action of maltogenic
.alpha.-amylase may be obtained only from a liquefied and
saccharified starch milk having a particular composition, having in
particular a bimodal carbohydrate spectrum, namely having, apart
from a high maltose and an appreciably high oligosaccharide
content, a high glucose content.
[0028] The present invention seeks therefore, to ensure that the
impurities are in the form of glucose rather than in the form of
oligosaccharides, and in particular maltotriose, with a molecular
mass close to that of maltose.
[0029] The particular bimodal carbohydrate spectrum of the
liquefied and saccharified starch milk is obtained according to the
process of the invention by carrying out a molecular sieving step
on the latter.
DETAILED DESCRIPTION OF THE INVENTION
[0030] The first step of the process according to the invention is
inherently known. It consists in liquefying a starch milk of any
botanical origin; it may originate from wheat, corn or potato, for
example.
[0031] Acid is added to this starch milk in the case of so-called
acid liquefaction, or an .alpha.-amylase is added in the case of
enzymatic liquefaction.
[0032] In the process according to the invention, it is preferable
to carry out controlled hydrolysis of the starch milk so as to
obtain a liquefied starch milk with a low degree of conversion.
Thus, the conditions of temperature, pH, enzyme and calcium level
known to the skilled person are determined in such a way that they
make it possible to obtain a DE (dextrose equivalent) of less than
10, preferably less than 6, and more particularly less than 4.
Preferably, the liquefaction step is carried out in two sub-steps,
the first consisting in heating the starch milk for a few minutes
and to a temperature in the range 105.degree. C. to 108.degree. C.
in the presence of an .alpha.-amylase (TERMAMYL.RTM. 120L type sold
by NOVO) and a calcium-based activator, the second consisting in
heating the starch milk thus treated to a temperature in the range
95.degree. C. to 100.degree. C. for one to two hours.
[0033] Once the liquefaction step has ended, under conditions of
dry matter content, pH, enzyme and calcium level that are well
known to the skilled person, inhibition of the .alpha.-amylase is
carried out. This .alpha.-amylase inhibition may take place
preferably by thermal means by carrying out a thermal shock of a
few seconds at a temperature greater than or equal to 130.degree.
C. at the outlet of liquefaction.
[0034] Saccharification of the liquefied starch milk is then
carried out by means of a .beta.-amylase such as that sold by
GENENCOR under the name SPEZYME.RTM. BBA 1500.
[0035] During this step, it is advisable to combine the
.beta.-amylase with an enzyme which specifically hydrolyses the
.alpha.-1,6 bonds of the starch. This addition of a debranching
enzyme makes it possible on the one hand to accelerate the
hydrolysis reactions without simultaneously accelerating the
reversion reactions and, on the other hand, to reduce the quantity
of highly branched oligosaccharides normally resistant to the
action of maltogenic enzymes.
[0036] This addition of debranching enzyme may take place at the
time of the addition of .beta.-amylase or at the time of the
addition of maltogenic .alpha.-amylase.
[0037] According to the invention, the debranching enzyme is
selected from the group comprising pullulanases and isoamylases. An
example of pullulanase is that sold by ABM under the name
PULLUZYME.RTM. 750L. An example of isoamylase is that sold by
HAYASHIBARA.
[0038] Advantageously, the process according to the invention is
carried out in the presence of isoamylase, the Applicant company
having observed that said isoamylase made it possible to obtain a
maltose syrup having a higher maltose content than when pullulanase
was used.
[0039] In a particular embodiment of the invention, the
saccharification step may also be carried out wholly or partially
in the presence of fungal .alpha.-amylase, for example,
SPEZYME.RTM. DBA 1500 (sold by GENENCOR) instead of SPEZYME.RTM.
BBA 1500 (sold by the same company).
[0040] At the end of saccharification, it is possible to add a
little .alpha.-amylase which generally improves the subsequent
filtration steps. The quantities and conditions of action of the
different enzymes used in the liquefaction and saccharification
steps of the starch milk are generally those which are recommended
for the hydrolysis of starch and are well known to the skilled
person.
[0041] Saccharification with .beta.-amylase optionally combined
with the debranching enzyme is carried out until the maltose
hydrolysate contains at least 75 wt. % of maltose and preferably
about 80 wt. % of maltose. It lasts at least 24 hours.
[0042] The hydrolysate thus saccharified is then filtered over a
precoat filter or by microfiltration over membranes, then
demineralised and concentrated.
[0043] At this stage of the process according to the invention, the
liquefied and saccharified starch milk undergoes molecular sieving
in order to collect a fraction enriched with maltose and a fraction
enriched with glucose. After this, the fraction enriched with
maltose is brought into contact with a maltogenic .alpha.-amylase.
This latter is advantageously that sold by NOVO under the names
Maltogenase.RTM. 4000L and NOVAMYL.RTM..
[0044] The molecular sieving step used in the process according to
the invention may consist, for example, in a chromatographic
separation step or a step involving separation over membranes.
[0045] The chromatographic fractionation step is carried out in an
inherently known way, batchwise or continuously (simulated mobile
bed) over adsorbents of the cationic resin type or over strongly
acid zeolites, loaded preferably using alkali or alkaline-earth
ions such as calcium or magnesium but more preferably using sodium
ions.
[0046] Instead of the chromatographic separation step, it is
possible, in the process according to the invention, to use a step
involving separation by nanofiltration over membranes. Membranes of
different pore diameters are produced from numerous polymers and
copolymers of the polysulfone, polyamide, polyacrylonitrate,
polycarbonate, polyfuran etc. type.
[0047] Examples of the use of such membranes are described in
particular in the documents U.S. Pat. No. 4,511,654, U.S. Pat. No.
4,429,122 and WO-A-95/10627.
[0048] According to an advantageous embodiment of the process
according to the invention, the non-maltose part derived from the
membranes or from chromatography, comprising the fraction enriched
with glucose, is recycled upstream of the saccharification
step.
[0049] By virtue of the process according to the invention which
benefits from the advantages obtained both from the hydrolysis
steps used and from the molecular sieving step, it is possible to
obtain, with yields greater than 90%, a starch hydrolysate whose
maltose content is greater than 95%, and even greater than 98% if
an isoamylase is used in the hydrolysis steps.
[0050] At this stage of the process according to the invention, it
is optionally possible to carry out a crystallisation of the
maltose or a catalytic hydrogenation on the hydrolysate (or maltose
syrup).
[0051] The hydrogenation of such a hydrolysate is carried out
according to the rules of the art which lead, for example, to the
production of sorbitol from glucose.
[0052] It is equally possible to use catalysts based on ruthenium
and Raney nickel catalysts for this step. It is preferable,
however, to use Raney nickel catalysts which are less
expensive.
[0053] In practice, 1 wt. % to 10 wt. % of catalyst is used based
on the dry matter of the hydrolysate undergoing hydrogenation.
Hydrogenation is carried out preferably on a hydrolysate whose dry
matter content is in the range 15% to 50%, in practice around 30%
to 45%, under a hydrogen pressure in the range 20 bars to 200 bars.
It may be carried out continuously or batchwise.
[0054] If operations are carried out batchwise, the hydrogen
pressure used is generally in the range 30 bars to 60 bars, and the
temperature at which hydrogenation takes place is in the range
100.degree. C. to 150.degree. C. It is also important to maintain
the pH of the hydrogenation medium by adding soda or sodium
carbonate, for example, but without exceeding a pH of 9.0. This
method of operating makes it possible to avoid the appearance of
cracking or isomerisation products.
[0055] The reaction is terminated when the reducing sugar content
of the reaction medium has become less than 1%, preferably less
than 0.5% and more particularly less than 0.1%.
[0056] After the reaction medium has been cooled, the catalyst is
removed by filtration and the maltitol syrup thus obtained is
demineralised over cationic and anionic resins. At this stage, the
syrups contain at least 93% maltitol.
[0057] The maltitol syrup obtained in the preceding hydrogenation
step may then undergo a crystallisation step in order to obtain
crystallised maltitol.
[0058] According to a preferred embodiment according to the
invention, the maltitol syrup obtained in the preceding
hydrogenation step is used, the succession of following steps
consisting in:
[0059] concentrating the maltitol syrup;
[0060] crystallising and separating the maltitol crystals
formed;
[0061] carrying out molecular sieving on the crystallisation mother
liquors and, in particular, chromatographic fractionation so as to
obtain a maltitol-rich fraction and a maltitol-poor fraction;
[0062] recycling the maltitol-rich fraction upstream of the
crystallisation step;
[0063] optionally carrying out acid hydrolysis and/or enzymatic
hydrolysis on the maltitol-poor fraction using, for example, an
immobilised or non-immobilised amyloglucosidase;
[0064] optionally carrying out hydrogenation of said hydrolysed
maltitol-poor fraction in order to obtain a sorbitol syrup.
[0065] Surprisingly and unexpectedly, the use according to the
invention of a maltose-rich syrup for the preparation of
crystallised maltitol makes it possible to reduce very
substantially (up to 80% compared with a conventional process) the
quantities of mother liquors (i.e. the maltitol-poor fraction)
produced during the molecular sieving step downstream of the
crystallisation step.
[0066] Other features and advantages of the invention will become
clear on reading the examples that follow. They are given here,
however, only by way of non-limiting example.
EXAMPLE 1
[0067] A starch milk with a dry matter content of 31% is liquefied
in the conventional way using 0.2% TERMAMYL.RTM. 120L
(.alpha.-amylase sold by NOVO) at a pH of 5.7 to 6.5 to a DE
slightly below 4.
[0068] The reaction medium is then heated for a few seconds to
140.degree. C. in order to inhibit the .alpha.-amylase, then the pH
is adjusted to between 5 and 5.5 and the temperature to 55.degree.
C.
[0069] Saccharification is carried out to a dry matter content of
25% or slightly below, in the presence of pullulanase
(PULLUZYME.RTM. 750L sold by ABM) and .beta.-amylase (SPEZYME.RTM.
BBA sold by GENENCOR) in respective amounts of 0.1% and 0.05% based
on dry matter.
[0070] Saccharification, which lasts about 48 hours, gives a
hydrolysate having the following composition. DP1: 1.4%, DP2:
82.4%, DP3: 13.2%, DP4 and above: 2.6%.
[0071] The hydrolysate then undergoes conventional purification by
filtration, bleaching and demineralisation and is then concentrated
to about 20% of dry matter and adjusted to a pH of 5.5.
[0072] A step involving the continuous chromatography of the
maltose hydrolysate thus obtained is carried out in the following
manner.
[0073] Four columns of a liter of resin PCR 732 in the sodium form
thermostated to 75.degree. C. are assembled in series and fed
continuously with the maltose hydrolysate brought to a dry matter
content of 60 wt. %, at a flow rate of 110 ml/h.
[0074] The fractions enriched with maltose having the following
composition are recovered at the outlet of the column:
[0075] DP1: 1.5%, DP2: 94%, DP3: 4.5%.
[0076] The chromatographic maltose yield is 91.5%.
[0077] These fractions are concentrated to about 20% of dry matter
and adjusted to a pH of 5.5 then brought into contact with a
maltogenic .alpha.-amylase (Maltogenase.RTM. 4000L sold by NOVO) in
a quantity of 0.3% based on dry matter. The composition of the
maltose syrup obtained is as follows: DP1: 4%, DP2: 95.5%, DP3:
0.5%.
EXAMPLE 2
[0078] The maltose syrup obtained in example 1 above undergoes a
maltose crystallisation step in the following manner. A maltose
solution with a dry matter content of 75 wt. % is prepared at a
temperature of 75.degree. C. The maltose solution is seeded with 5
wt. % of maltose crystal seeds and the solution is cooled from
75.degree. C. to 40.degree. C. at a rate of 0.5.degree. C. per hour
whilst agitating the solution at 50 rpm in a double-walled
crystalliser.
[0079] At the end of crystallisation, the crystals are separated
from the mother liquor using a conventional centrifuge.
[0080] The crystallisation yield is 50 wt. % expressed in weight of
crystallised maltose based on the starting weight of maltose.
[0081] The maltose purity of the crystals recovered is 97.5% based
on dry matter. The water content is 5%.
EXAMPLE 3
[0082] The maltose syrup obtained from example 1 is demineralised
then hydrogenated under the following conditions:
1 Dry matter: 40% Temperature: 115.degree. C. Amount of catalyst: 5
wt. %/dry matter H.sub.2 pressure: 50 bars
[0083] The reaction is terminated when the reducing sugars are less
than 0.3%. The medium is then filtered, demineralised and
concentrated to 85% of dry matter; its composition is:
2 Sorbitol: 5.5% Maltitol: 94.0% Higher hydrogenated products:
0.5%
[0084] The crystallisation step is then carried out by cooling from
75.degree. C. to 25.degree. C. at a rate of 0.5.degree. C./hour
under slow agitation, with inoculation with 6 wt. %/dry matter of
crystallised maltitol with a particle size in the range 200 .mu.m
to 250 .mu.m.
[0085] After centrifuging, the crystals are dried and have a
content of 99.7%; the mother liquors are adjusted to 60% dry matter
and chromatographed.
[0086] Four columns of one liter of resin PCR 732 in the calcium
form, thermostated to 85.degree. C. are assembled in series and fed
continuously at a rate of 120 ml/h. The maltitol yield is 90.7% and
the rich fraction (maltitol-rich fraction) has the following
composition: sorbitol 4.5%; maltitol 95%; higher hydrogenated
products: 0.5%.
[0087] The maltitol-poor fraction containing 53.5% of sorbitol,
42.5% of maltitol and 4% of higher hydrogenated products then
undergoes an acid hydrolysis step.
[0088] Hydrolysis of the maltitol-poor fraction is carried out
continuously over a cation exchange resin of the Purolite C145 type
in the H' form placed in a column thermostated to 115.degree. C.;
by feeding the column at 1 bv/h.sup.1 with the solution
concentrated to 40%, the following composition is obtained:
sorbitol: 70.5%; maltitol: 12.3%; higher products: 0.4%, glucose:
16.8%.
[0089] This solution is then demineralised and hydrogenated under
the following conditions:
3 dry matter: 40% temperature: 135.degree. C. amount of catalyst: 5
wt. %/dry matter hydrogen pressure: 50 bars.
[0090] until a free reducing sugar content of less than 0.1% is
obtained.
* * * * *