Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Reexamination Certificate
1997-09-12
2001-03-20
Lee, Howard C. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
C536S123000, C536S123130, C536S124000, C568S852000, C568S861000, C568S863000, C426S658000
Reexamination Certificate
active
06204378
ABSTRACT:
The present invention relates to a new process for producing palatinitol.
More particularly it relates to a production process for palatinitol starting from isomaltose or &agr;-D-glucopyranosyl-(1→6)-D-glucose.
Palatinitol is a sweetening agent of low caloric mass and low cariogenicity which up to now is obtained by catalytic hydrogenation at neutral pH of isomaltulose or &agr;-D-glucopyranosyl-(1→6)-D-fructose.
Isomaltulose is itself obtained by enzymatic isomerization, using a saccharose glysosyl transferase, saccharose or &agr;-D-glucopyranosyl-(1→2)-&bgr;-D-fructofuranoside.
Therefore, it is saccharose which constitutes the raw material for obtaining palatinitol, a mixture containing roughly equimolecular proportions of &agr;-D-glucopyranosyl-(1→6)-D-sorbitol (GPS or isomaltitol) and &agr;-D-glucopyranosyl-(1→6)-D-mannitol (GPM).
Palatinitol, which is also called isomalt, is in particular marketed by the Company Süddeutsche Zucker AG under the name Palatinit®.
Among other documents which concern the obtaining and properties of palatinitol the following work can be referred to: “Alternative Sweeteners” published in 1986 by LYN O'BRIEN NABORS, chapter 11, pages 217 to 244.
Concerned to develop a process which allows palatinitol to be obtained from a raw material other than saccharose, the Applicant Company has noticed that this goal could be achieved by a process using isomaltose or &agr;-D-glucopyranosyl-(1→6)-D-glucose.
In accordance with the present invention, palatinitol is obtained thanks to a process characterized in that
in a first stage, the epimerization of isomaltose is carried out under conditions which allow a mixture of &agr;-D-glucopyranosyl-(1→6)-D-mannose and isomaltose to be obtained,
in a second stage, catalytic hydrogenation is carried out on this mixture.
in a third stage, chromatographic depletion of the isomaltitol in this hydrogenated mixture is carried out so as to obtain a roughly equimolecular mixture of &agr;-D-glucopyranosyl-(1→6)-D-sorbitol and &agr;-D-glucopyranosyl-(1→6)-D-mannitol
If it is reasonable to imagine that palatinitol may be obtained from saccharose, the person skilled in the art could in no way expect that this same palatinitol might be obtained from isomaltose, which is obtained from glucose and thus from diverse and various starches.
In fact, in the first case, saccharose, the structural formula of which includes a fructose unit, will produce, in a known fashion by enzymatic isomerization, the corresponding ketose i.e. isomaltulose.
And it is known to the person skilled in the art that the hydrogenation of such a ketose leads to the formation of the two corresponding itols in approximately equimolecular proportions. Therefore, the fact that the formula of saccharose is related to that of palatinitol allows the result to be anticipated.
However, the process according to the invention does not implement a starting product whose formula is related to that of the sought palatinitol. In fact, isomaltose as well as glucose and starch, have a structure which does not contain a fructose unit and is therefore far from being related to that of palatinitol.
The process according to the invention therefore allows freedom from the requirement to use saccharose as raw material for the production of palatinitol since isomaltose can be easily obtained from glucose and therefore from diverse and varied starches, whether they originate from cereals or tubers.
A process for obtaining isomaltose from glucose or a corn syrup is described, for example, in the French Patent Application 2,515,186.
In the process according to the invention, it is preferred to use crystallized isomaltose, although syrups which are very rich in isomaltose are also suitable if one accepts that maltitol or isomaltotriitol may be present in the palatinitol. The two last-named compounds originate from the hydrogenation of maltose or isomaltotriose which represent the main impurities in syrups which are very rich in isomaltose.
In the process according to the invention, the epimerization of isomaltose can be carried out as described in the Japanese Patent Application 63-162698 using a metallic salt and an amine but it is preferably carried out in the manner described in the Japanese Patent Application 63-96195 and which consists of reacting an aqueous solution of isomaltose, at a pH comprised between 2.5 and 4, in the presence of molybdic anhydride or hexavalent molybdenum salts, at a temperature comprised between 90° C. and 140° C.
Preferably, ammonium molybdate is used in a proportion of approximately 0.1 to 1.5% by weight relative to the isomaltose.
More preferably, the epimerization of isomaltose is carried out in the form of an aqueous sweetened solution containing 10 to 70% isomaltose.
The epimerization conditions are adjusted (essentially the catalyst content, the duration of epimerization and the reaction temperature) so as to obtain a mixture of isomaltose and &agr;-D-glucopyranosyl-(1→6)-D-mannose, containing 10 to 40% of the latter compound. It is not economical to treat mixtures containing less than 10% of this compound, and mixtures containing more than 40% of it contain too many impurities which form under the extreme conditions of epimerization.
It is preferred to operate under conditions which allow 20 to 35% of &agr;-D-glucopyranosyl-(1→6)-D-mannose to be obtained and yet more preferably from 25 to 35% of this compound.
The mixture obtained in this way is then demineralized on ion exchange resins in order to remove the salts which have been used as the catalyst.
In the process according to the invention hydrogenation of the epimerized mixture is carried out in a manner known per se, continuous or discontinuous, under a hydrogen pressure of 30 to 200 bars, at a temperature of 80 to 150° C. in the presence of a nickel- or ruthenium-based catalyst and at a pH close to neutral. Hydrogenation carried out at a pH of less than 4.0 will result in partial hydrolysis of the isomaltose into glucose and the &agr;-D-glucopyranosyl-(1→6)-D-mannose into glucose and mannose with the appearance of sorbitol and mannitol. Hydrogenation at a pH higher than 9 will produce a result which is not desired, the formation of GPS and not GPM from the &agr;-D-glucopyranosyl-(1→6)-D-mannose. In a general fashion, the hydrogenation is carried out until the content of the reducing sugars, measured by the Bertrand method, becomes lower than 1% and preferably, lower than 0.5%.
After the hydrogenation stage, the syrups obtained are purified to remove the catalyst by filtration then demineralization on ion exchange resins and these syrups are concentrated to a dry matter content comprised between 10 and 70% with a view to their chromatography. These hydrogenated syrups thus show an average composition ranging from 10 to 40% of GPM and from 60 to 90% of GPS. Syrups are preferred which contain from 25 to 35% of GPM and from 65 to 75% of GPS.
In the process of the invention, depletion of the hydrogenated syrups in GPS by chromatographic route is then carried out.
As a rule, when a chromatographic stage is used to achieve the separation of two components from a binary mixture, the chromatography is carried out in such a way that the two components are separated in the most complete fashion possible, i.e. in order to obtain a fraction A which only contains very little of compund B and a fraction B which only contains very little of compound A.
In the process according to the invention, the depletion of the epimerized mixture in GPS is, on the contrary, carried out in such a manner as to obtain an excluded fraction containing a roughly equimolecular proportion of GPS and GPM, the other adsorbed fraction being constituted by very pure GPS. By roughly equimolecular is meant from 40 to 60% and more preferably from 45 to 55% of one of the two compounds relative to the total mass of the two compounds. This way of proceeding has the advantage of directly obtaining palatinitol without having to resort to remixing pure fractions of GPM and G
Duflot Pierrick
Fouache Catherine
Henderson & Sturm LLP
Lee Howard C.
Roquette Freres
LandOfFree
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