Chemistry: molecular biology and microbiology – Micro-organism – tissue cell culture or enzyme using process... – Preparing compound containing saccharide radical
Reexamination Certificate
1999-06-09
2001-02-06
Brunsman, David (Department: 1755)
Chemistry: molecular biology and microbiology
Micro-organism, tissue cell culture or enzyme using process...
Preparing compound containing saccharide radical
C435S095000, C435S099000, C127S040000, C127S055000
Reexamination Certificate
active
06184003
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for preparing crystalline &agr; anhydrous dextrose of high purity from a starch hydrolysate.
More particularly, the invention relates to a process for preparing a crystalline &agr; anhydrous dextrose which consists in subjecting a starch hydrolysate to a nanofiltration in order to prepare a syrup with a high glucose content, then performing an evaporative crystallisation of the glucose syrup thus obtained in order to obtain crystals of &agr; anhydrous dextrose of high purity.
BACKGROUND OF THE INVENTION
Dextrose may be produced in three crystalline forms, a hydrated form or &agr; monohydrate form, and two anhydrous forms, i.e. the &agr; anhydrous and &bgr; anhydrous forms.
Solid dextrose is produced classically by crystallising supersaturated syrups with a high glucose content, and the crystals obtained are crystals of &agr; monohydrate dextrose. Moreover, this process is described in the U.S. Pat. No. 3,039,935.
As for &agr; anhydrous dextrose itself, it is obtained classically by dissolving crystals of &agr; monohydrate dextrose in water, then performing crystallisation at temperatures in the range 60° C. to 65° C., under carefully controlled conditions of evaporative crystallisation under vacuum.
Furthermore, there are a number of processes for manufacturing anhydrous dextrose from starch hydrolysates, for example:
the process described in the U.S. Pat. No. 3,197,338, consisting in concentrating a starch hydrolysate to a dry matter content of dextrose of at least 95% on a dry basis, preferably at least 98% on a dry basis, crystallising this by a mixing process at a temperature in the range 75° C. to 110° C., and extruding it in the form of a ribbon in a zone which cools the product to a temperature of less than 65.5° C.,
the process described in the U.S. Pat. No. 3,236,687, consisting in concentrating a starch hydrolysate to a dry matter content of dextrose of a value in the range 93% to 96% on a dry basis and subjecting it to a strong shear force in the presence of gas in order to form very small crystals of dextrose,
the process described in the U.S. Pat. No. 4,059,460, consisting in preparing a concentrated melt of a glucose syrup with a concentration of 85% to 93% on a dry basis, at a temperature higher than 110° C. The concentrated glucose syrup is then mixed by shearing force and cooled to a temperature of less than 95° C. Finally, the glucose syrup is kept at a concentration of less then 93% and at a temperature higher than the temperature of crystallisation of &agr; monohydrate dextrose, then shaped and converted into a solid mass. This solid mass is then granulated and dehydrated to a water content of less than 2%.
However, all these processes have two major disadvantages:
that of directly using starch hydrolysates which contain, in addition to glucose, non-negligible proportions of other sugars with a higher degree of polymerisation (DP), for example DP2 (such as maltose) and DP3 (such as maltotriose). These sugars with a higher DP result in incomplete hydrolysis, whether it be chemical or enzymatic, of said starch hydrolysate.
that of leading to mixtures of the two anhydrous forms of dextrose, at best in equivalent proportions, or even favouring the &bgr; anhydrous form, and sometimes accompanied by &agr; monohydrate dextrose, resulting in the incorporation of residual moisture as water of crystallisation.
The crystalline dextroses obtained by these processes then have a strong tendency to agglomerate, which makes them difficult to handle. Furthermore, their flow characteristics are particularly poor.
In order to resolve the first and main disadvantage described above and to lead to the production of a dextrose with a more homogeneous crystalline structure, the patent FR 2.483.427 suggested concentrating a starch hydrolysate to a dry matter content of glucose of 92% to 99%, preferably about 95% to 99%, in a thin layer evaporator and at a temperature in the range 90° C. to 135° C.
However, the product obtained still contains more than 50% of the &bgr; anhydrous form together with the &agr; anhydrous form, and a non-negligible proportion of amorphous structure.
The anhydrous character is obtained in this process by using particularly high temperatures, but these operating conditions also have the direct consequence of increasing the proportion of the &bgr; anhydrous form, which crystallises naturally at said temperatures.
As for the problem associated with contamination by sugars with a higher DP of the starch hydrolysates, two solutions have been suggested.
The first consists in optimising the process for preparing said starch hydrolysate.
However, although this solution reduces significantly the proportion of sugars with DP2 and DP3, it is especially difficult to obtain residual concentrations of less than 5%.
The second solution consists in using a nanofiltration process which eliminates all traces of these higher DPs, as is described in patent application FR 2.762.616, the owner of which is the assignee, or U.S. Pat. No. 5,869,297.
From all the preceding, however, it can be seen that there is an unfulfilled need to provide a crystalline &agr; anhydrous dextrose of high purity.
In fact, all the processes of the prior art provide merely solid dextrose consisting of a mixture of the &agr; and &bgr; anhydrous forms, or even of the monohydrate forms, associated with relatively large amounts of DP2, DP3 or even higher DPs.
OBJECTS AND SUMMARY OF THE INVENTION
Thus, the invention has the object of remedying this situation and of providing a process which responds better than existing processes to the various constraints which are met in practice.
In fact, it is obvious from the prior art that the classical processes for preparing anhydrous dextrose which require, for example, the use of two crystallisation techniques in sequence, take place in high temperature ranges which invariably lead to mixtures of the &agr; and &bgr; crystalline forms.
The applicants have thus succeeded in refining a process producing a crystalline &agr; anhydrous dextrose of high purity from a syrup with a high glucose content prepared by nanofiltration of a starch hydrolysate.
In the context of the invention, “crystalline &agr; anhydrous dextrose of high purity” is understood to mean a concentration of &agr; anhydrous dextrose of about 100 wt. %.
The process for preparing a crystalline &agr; anhydrous dextrose according to the invention is thus characterised in that:
a) a starch hydrolysate is prepared;
b) said starch hydrolysate is nanofiltered over membranes in such a way as to obtain a nanofiltration permeate constituting a syrup with a high glucose content and a nanofiltration retentate;
c) said syrup with a high glucose content is concentrated to a dry matter content of at least 70 wt. % of glucose, at a temperature in the range 50° C. to 110° C.;
d) said concentrated syrup is crystallised by evaporation and agitation in such a manner as to obtain a crystalline mass containing at least 30 wt. % of the crystals;
e) the crystals of &agr; anhydrous dextrose thus obtained are separated, recovered and dried.
In accordance with a first embodiment of the process according to the invention, said starch hydrolysate is a crude starch hydrolysate obtained by:
liquefaction of a starch milk using an &agr;-amylase in such a way as to obtain a liquefied starch milk,
saccharification of said liquefied starch milk using a glucogenic enzyme in such a manner as to obtain a crude saccharified hydrolysate, and
optionally, microfiltration of said crude saccharified hydrolysate in such a manner as to recover a microfiltration permeate containing said crude starch hydrolysate and a microfiltration retentate.
In accordance with a second embodiment of the process according to the invention, said starch hydrolysate is a crude starch hydrolysate obtained by:
liquefaction of a starch milk using an &agr;-amylase in such a way as to obtain a liquefied starch milk,
saccharification of said liquefied starch milk using a glucogenic enzyme in such a manner
Brunsman David
Henderson & Sturm LLP
Roquette Freres
LandOfFree
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