Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Reexamination Certificate
1999-05-28
2002-02-19
Gitomer, Ralph (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
C536S123100, C536S124000, C536S127000, C536S128000
Reexamination Certificate
active
06348590
ABSTRACT:
The invention relates to a method for improving the exploitability and processability of guar endosperm and products obtained using said method in the form of ammonia-exploded guar endosperm halves (guar splits), guar flour and guaran powder.
Guar flour is used in the food industry as a stabilizer for ice cream and sherbet and some soft cheeses, as a binder and thickening agent for sauces and similar products as well as also in the cosmetic industry. In industry, guar flour is used for finishing and sizing textiles and as a thickening agent for textile printing pastes. A large amount of guar flour is also used in the paper industry as a beater additive for producing stronger papers.
The main constituent of guar flour is guaran. Guaran is a galactomannan, which consists of approximately 36% D-galactose and 64% mannose. The mannose units are linked together in pyranose form &bgr;-1,4 glycosidically into long main chains, to which the galactose units are fixed in pyranose form by &agr;-1,6 glycosidic bonds. In the case of guaran, each second mannose building block of the main chain carries a galactose side group. The average molecular weight of guaran is significantly greater than 200,000.
Guaran is contained in the endosperm of the seed of the guar bean, Cyamopsis tetragonoloba, which is widespread in India and has been cultivated since 1944 on a larger scale in the USA. The endosperm is a food store for the development of the embryo during germination. Because guar is a dicotyledonous plant, there are two endosperm halves in each seed. These endosperm halves surround the embryo and, in turn, are surrounded by a seed coat, which usually has a light brown color. The endosperm itself consists of a layer of cells, the aleuron, and of a nutrient and reservoir substance for the embryo, namely the guaran. The cells of the aleuronic layer contain many aleuron grains, that is, the thickened protein vacuoles. During the germination of the guar seeds, enzymes are synthesized in the aleuron cells and delivered to the endosperm, in order to mobilize reserve materials. The two predominant enzyme activities are &agr;-galactosidase and &bgr;-mannase activities.
The seed coat and the embryo are removed industrially by milling steps and mechanical sorting. The different hardness of the seed components is used for this purpose. The multi-step milling and screening steps are frequently combined with other mechanical treatments for breaking open the seeds and sorting the components. There are different types of mills, which can be used in conjunction with roasting processes or the treatment of the seed with water or acid. If used for foods, special attention must be paid to the thorough removal of the embryo. The purified endosperm is sold under the name of “guar splits”.
Guar splits usually are ground into a powder, which is called guar flour or guar gum powder. The protein-containing endosperm sheath of the guar splits usually is not removed during the milling. For certain applications, the protein portion in the guar flour, introduced by the protein-containing sheath, interferes. There is therefore a need for a simple and efficient method, with which guaran can be isolated in very pure form from the guar splits.
The milling of the guar splits is, moreover, associated with the expenditure of appreciable electrical energy. The milling conditions furthermore affect the viscosity of the aqueous solution of guaran or its derivatives. There is therefore a need for a method, for which milling of guar splits is not required.
Aqueous solutions of conventional commercial guar flour usually are cloudy. The cloudiness is caused mainly by the presence of insoluble portions of the endosperm. Derivatives, produced from guar flour, admittedly generally show an improved solubility and clarity of the solution. The improved clarity is due to the derivatization and solubilization of insoluble seed impurities. For certain applications, however, the properties of derivatized guar flour are also inadequate. For example, carboxymethylated guar has a relatively high intrinsic viscosity with only a weakly pronounced Newtonian range at low shear rates. When carboxymethylated guar is used as a thickening agent in textile printing, the removability by washing from conventional commercial products is poor. The cause presumably lies in an inhomogeneous distribution of substituents which, in turn, is due to the fact that the derivatizations were carried out on the milled guar splits in a heterogeneous reaction. This disadvantage cannot be eliminated completely even by milling to a very small particle size. There is therefore a need for a guar product, which is completely water soluble or can be derivatized in a homogeneous reaction.
It is therefore an object of the invention to submit proposals, with which the requirements, addressed above, can be satisfied. In particular, the exploitability and processability of guar endosperm halves (guar splits) shall be improved, as shall the millability to guar flour. Moreover, it shall be possible to isolate pure guaran easily and efficiently from guar splits, milling of the guar splits not being required and the guaran being completely water soluble. Moreover, it shall be possible to derivatize the guaran by means of a homogeneous reaction.
Pursuant to the invention, this objective is accomplished by a method for improving the exploitability and processability of guar endosperm, for which the guar endosperm halves (guar splits) are brought into contact with liquid ammonia at an initial pressure, which is higher than atmosphere pressure, and at a temperature of at least 25° C., the amount of liquid ammonia being sufficient at least to wet the surface of the guar endosperm halves and the capacity, available to the system comprising endosperm halves and liquid ammonia, being enlarged explosively with a reduction in pressure by at least about 5 bar and the sheath of the endosperm halves being torn open by these means.
The WO 96/30411 discloses a method for activating polysaccharides by an ammonia explosion. In one example, guar flour is treated with liquid ammonia and exploded. The use of guar endosperm halves instead of guar flour as a starting material is not made obvious by the WO 96/30411.
Preferably, the guar endosperm starting material consists of endosperm halves, which have not been significantly comminuted previously, that is, which essentially are intact guar splits.
During the treatment of the guar splits with liquid ammonia, the liquid ammonia can penetrate the sheath surrounding the guar splits and penetrate into the polysaccharide core. During the subsequent explosion, the volume of the penetrated ammonia increases suddenly. The gaseous ammonia can no longer escape quickly enough through the sheath and leads to a tearing open of the surface of the guar splits. The guaran, contained in the native guar splits, is microcrystalline and generally has a degree of crystallinity of about 20 to 30%. Under the action of the liquid ammonia, there is at least partial swelling of the polysaccharide substance. Intermolecular hydrogen bonds between the molecular chains are broken, since the ammonia molecule competes with the hydroxyl groups of the neighboring molecules. As a result of the explosion, there is evaporation of the ammonia between the chains of molecules. The chains of molecules, the intermolecular hydrogen bonds of which have previously been broken, are torn apart. This leads to an exposure of regions, which normally are not readily accessible to reagents. In particular, the polysaccharide portion becomes water soluble due to the ammonia explosion. The guaran in the exploded guar splits no longer is crystalline and, instead, has become amorphous.
When there is mention of “explosive” in connection with the inventive method, then this concept is to be interpreted narrowly. Preferably, the explosive increase in volume takes place within a period of less than 1 second and, in particular, of the less than 0.5 seconds. The ammonia explosion of the inventive method can take place batc
Karstens Ties
Stein Armin
Darby & Darby
Gitomer Ralph
Khare Devesh
Rhodia Acetow AG
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