Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Reexamination Certificate
2000-10-20
2002-07-09
Gitomer, Ralph (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
C536S123100, C536S123130, C536S124000
Reexamination Certificate
active
06417346
ABSTRACT:
TECHNICAL FIELD
The subject of the invention is a novel process for preparing a noncrystallizable polyol syrup which is stable to heat and to alkalis.
It relates more precisely to a novel process for preparing a polyol syrup which can be used in the manufacture of laundry soaps, detergents, in the formulation of pharmaceutical syrups, of toothpastes, that is to say in any application which requires resistance in alkaline medium and/or in the hot state against the formation of undesirable colours or of inappropriate compounds from the point of view of their taste.
BACKGROUND
Polyols are understood to mean the products obtained by catalytic hydrogenation of simple reducing sugars, of complex reducing sugars such as disaccharides, oligosaccharides and polysaccharides, as well as mixtures thereof, which will be designated in the text which follows by the term “sugar syrup”.
In general, the simple reducing sugars which are intended for catalytic hydrogenation according to the invention are glucose, xylose, fructose and mannose. The polyols obtained are then sorbitol, xylitol and mannitol.
The disaccharides are most often maltose, isomaltulose, maltulose, isomaltose and lactose, which lead, through catalytic hydrogenation, to maltitol, isomalt, isomaltitol and lactitol.
Noncrystallizable composition is understood to mean in the present invention the mixtures of polyols which form syrups which are not crystallizable at 20° C. and at a dry matter content of 70% when they are stored in an airtight container for one month. As a guide, the definition of a noncrystallizable sorbitol syrup for the purposes of the invention is in accordance with the European Pharmacopoeia 1997, paragraph 0437.
Sorbitol syrups are widely used in the food, pharmaceutical and chemical sectors. In the formulation of toothpastes and in particular in the manufacture of sodium bicarbonate toothpastes, the use of sorbitol syrups as humectant is only possible if the latter is stable in the presence of sodium bicarbonate, and does not generate a brown colour during storage. Indeed, this colour appears through a reaction of the bicarbonate with the reducing sugars: glucose, maltose, oligo- and polysaccharides. The intensity of the colour increases with the number of polysaccharide units; accordingly, a molecule of maltose generates more colour than a molecule of dextrose. The colour is also greatly accelerated by the temperature to which the syrup is exposed. It has indeed been observed that the same colour intensity is obtained during a storage of 10 days at 45° C. and during a storage of 15 months at 20° C. It is preferable, in addition, for these syrups to be noncrystallizable, so as to facilitate their handling and their transport regardless of the climatic conditions and to ensure the stability over time of the finished products prepared from such syrups.
Maltitol syrups also represent a major class, and are mainly used to prepare noncariogenic food and pharmaceutical products.
Xylitol syrups, although more expensive, have undergone major development because of their high sweetening power, their dental properties and their excellent humectant characteristics.
It is known that the colour of a polyol syrup in the presence of alkalis is linked to the presence of free, reducing sugars: glucose, maltose, oligo- and polysaccharides.
Improving the stability of such syrups therefore requires the elimination of these free sugars.
Several routes have already been envisaged on the laboratory scale.
Japanese patent JP 51 86406 offers perspectives for improving the purity of crystallizable sorbitol syrups using a reduction of crystallized glucose under alkalinity maintained during the entire reduction reaction, with the aim of obtaining sorbitol of high purity, low in nonreduced sugars.
However, this technique remains without practical interest on the industrial scale because it requires the installation of an expensive feeding, control and regulating device, and the constant addition of buffer and of alkaline solution during the reaction penalizes the subsequent purification step. This process is in addition relatively polluting taking into account the large quantities of reagents used. Furthermore, nothing is said on the stability of the sorbitol syrups resulting from the said process.
Japanese patent JP 41 12212 mentions a process for preparing sorbitol of maximum purity which is resistant to heat and to alkalis, which consists in a reduction by addition of hydrogen at high pressure, by envisaging either adjusting the solution to pH 8 to 10 just before the reduction reaction is complete, or heating to a temperature of 60 to 90° C. the sorbitol solution which has been reduced and set at pH 8 to 10 beforehand by means of an alkali, and then after decomposition of the directly residual reducing sugars, in a separation by filtration with or without neutralization with an acid and with or without decolorization on charcoal, and then in a purification on ion-exchange resin.
This process, which applies to a crystallizable sorbitol solution, gives rise to a substantial formation of impurities because of the fact that the reducing sugars are subjected to a relatively long treatment time, of the order of five hours, and does not therefore result in a stability which is judged to be sufficient.
Japanese patent JP 63 79844 and JP 7 145090 describe a process for preparing polyols stable to heat and to alkalis, which consists in treating for one to two hours in the hot state and in an alkaline medium a purified aqueous solution of polyols once by treatment with charcoal and then on ion-exchange resin, and then in purifying once again the solution obtained at 50° C. by passage over an ion-exchange resin. This process applies most particularly to crystallizable sorbitol syrups obtained from glucose syrups of high purity. However, such crystallizable syrups are not appropriate for use in particular in toothpastes because of the many disadvantages which they exhibit. Moreover, this process is found to be particularly complex because of the multiple operations of which it consists, and is therefore difficult to apply on an industrial scale.
Patent EP 0 711 743 (incorporated herein by reference), of which the applicant is the proprietor, describes polyol compositions having a high chemical stability in alkaline medium and a very low reactivity.
These compositions, which are particularly appropriate for use in basic medium requiring an absence of colour, are obtained by catalytic hydrogenation of simple or complex reducing sugars, followed by stabilization and purification of the stabilized syrup.
The stabilizing step consists in subjecting the sorbitol syrups obtained by hydrogenation to oxidation, caramelization or fermentation, so as to bring the syrups to an optical density of less than or equal to 0.100 in an S test.
The applicant had indeed demonstrated that a satisfactory stability could only be achieved at low values in this test, the latter reflecting the colouring capacity of the compositions in alkaline medium.
OBJECTS OF THE INVENTION
In an attempt to further improve the performance of such a process, and with the aim of limiting the inorganic and organic discharges so as to be able to preserve the environment, the applicant then developed, after lengthy research studies, a novel process which makes it possible both to obtain noncrystallizable polyol syrups which are sufficiently stable in alkaline medium, and to easily offer, by limiting the purification operations, a high yield and lesser pollution, which the conventional techniques known in the prior art did not make it possible to obtain.
SUMMARY OF THE INVENTION
Accordingly, the applicant has found that it was appropriate, in order to obtain noncrystallizable polyol syrups stable to heat and to alkalis, to subject a sugar syrup which has been subjected to a hydrogenation and caramelization step, to a purification step on at least one strong cationic resin at a temperature of less than 50° C., the said temperature being chosen according to the level of reducing sugars desired
Ferez Patrick
Lefevre Philippe
Salome Jean-Paul
Gitomer Ralph
Henderson & Sturm LLP
Khare Devesh
Roquette Freres
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