Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Reexamination Certificate
1999-08-02
2003-09-02
Wilson, James O. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
C536S123100, C127S036000, C426S313000
Reexamination Certificate
active
06613898
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to reduced malto-oligosaccharide species and methods for the preparation thereof.
BACKGROUND OF THE INVENTION
Oligosaccharides are commonly prepared by the controlled hydrolytic cleavage of starches. In the production of such oligosaccharides, the glycosidic linkages of the starch molecules are partially hydrolyzed to yield at least one oligosaccharide species, and more typically, a mixture of oligosaccharide species. Each oligosaccharide species in the mixture may be characterized by its degree of polymerization (DP), which refers to the number of saccharide monomer units in the molecule. Each oligosaccharide species also may be characterized by its dextrose equivalent (DE), which generally indicates the proportion of aldehyde, hemiacetal or ketone terminal groups in the molecule, and which is a measure of the reducing sugar content of the oligosaccharide, expressed as a percentage of the total dry substance. The DE value and DP profile for a given oligosaccharide mixture can vary substantially, depending, for example, upon the type of starch precursor used to obtain the mixture and the conditions employed for hydrolysis of the base starch.
Oligosaccharide mixtures prepared by the hydrolytic cleavage of starch typically include at least one malto-oligosaccharide species. Malto-oligosaccharides are characterized as having a saccharide backbone that comprises predominantly 1-4 glycoside linkages. Malto-oligosaccharides having a DE less than 20 are known as maltodextrins, whereas malto-oligosaccharides having a DE of 20 or greater are known as syrup solids.
It is known in the art to reduce malto-oligosaccharides and other starch hydrolyzates by reducing the terminal groups in the malto-oligosaccharide or starch hydrolyzate molecule. Such reduced malto-oligosaccharides and other starch hydrolyzates are useful in a variety of applications, including, for example, sweetening agents and texturing agents in products intended for ingestion by animals or humans. Examples of such products include sweets, chewing gums, syrups, food additives, pharmaceutical agents, and so forth. Typically, starch hydrolyzates have been reduced via enzymatic, catalytic, or chemical methods. For example, U.S. Pat. No. 2,280,975 describes a process for the production of polyhydric alcohols via catalytic reduction of mono- and disaccharides. A more recent patent, U.S. Pat. No. 4,322,569, discloses the reduction of monosaccharides by contacting the monosaccharide with hydrogen in the presence of a nickel catalyst in a catalytic bed.
Known processes for the reduction of and starch hydrolyzates suffer from a number of drawbacks. For example, it is often desired to reduce a malto-oligosaccharide to a DE of zero or essentially zero. Typically, such would be accomplished by substantially completely catalytically hydrogenating the malto-oligosaccharide until the desired DE value is obtained. When malto-oligosaccharides are reduced in accordance with such methods, however, the polysaccharide backbones of the individual species in the mixture may become cleaved, as reported, for example in the aforementioned U.S. Pat. No. 2,280,975 with regard to the reduction reaction disclosed therein. Such cleavage of the polysaccharide backbone will cause the DP of the cleaved species in the malto-oligosaccharide to become lower, and will cause an alteration in the overall DP profile of the malto-oligosaccharide mixture. Such alteration of DP profile may cause certain physical properties of the mixture, such as viscosity, to change, thus potentially requiring alteration of processes in which the mixture is intended for use.
Another problem in the art pertains to the color-fastness of malto-oligosaccharides. Malto-oligosaccharides are typically characterized by having a non-zero DE value. One problem with known malto-oligosaccharides is that solutions thereof may tend to yellow under certain conditions, for example, under conditions of heat, alkaline pH, or traces of nitrogen-containing compounds, thus causing visual degradation of the product in which the malto-oligosaccharide is incorporated or other undesired effects. This tendency towards color formations is indicative of the chemical reactivity of the malto-oligosaccharides under the foregoing conditions, particularly towards nitrogen compounds.
In light of these shortcomings in the art, there exists a need for a method for reducing a malto-oligosaccharide to a DE of essentially zero without altering substantially the DP of the malto-oligosaccharide, and particularly for reducing a mixture of malto-oligosaccharides to a DE of essentially zero without altering substantially the DP profile of the mixture. A further need in the art exists for a malto-oligosaccharide product having an improved resistance to is color formation. The general objects of the present invention are to provide a method and a product that overcome the foregoing drawbacks of the prior art.
THE INVENTION
The foregoing general objects have been achieved by the present invention, which provides a method for the catalytic reduction of an oligosaccharide, and which further provides a reduced oligosaccharide prepared thereby. In accordance with the invention, a method for substantially reducing a mixture of a plurality of oligosaccharide species is provided. The oligosaccharide species may differ at least in DP value, thus defining a DP profile for the mixture. In the preferred embodiment of the invention, the method comprises the steps of providing the oligosaccharide mixture, and catalytically hydrogenating the mixture under hydrogenation conditions suitable to substantially preserve the DP profile of the mixture. Surprisingly, it has been found that catalytic hydrogenation of oligosaccharides such as maltodextrins in the presence of a metal catalyst, such as platinum, palladium, ruthenium, rhodium, or nickel, at temperatures ranging from about 50° C. to about 150° C. and pressures ranging up to about 1500 psi will be effective in substantially reducing the DE of the mixture to zero or essentially zero, without substantially altering the DP profile of the mixture. In another embodiment of the invention, the method comprises catalytically reducing an oligosaccharide or mixture of oligosaccharides at a pH ranging from about 3.5 to about 8.5. In either embodiment, the invention is more generally contemplated to be useful in connection with the catalytic reduction of polysaccharides.
In accordance with a preferred embodiment of the invention, a mixture of reduced malto-oligosaccharide species is catalytically reduced. The species differ in at least DP value thus defining a DP profile for the mixture. Surprisingly, it has been found that, when a starting malto-oligosaccharide mixture is catalytically hydrogenated in accordance with the invention, the reduced malto-oligosaccharide mixture thus formed will have a DP profile that is not substantially altered as compared with the DP profile of the starting malto-oligosaccharide mixture. It has further surprisingly been found that the resistance to color formation of the reduced malto-oligosaccharide, as measured by the light absorbance thereof, is improved relative to the starting mixture of unreduced malto-oligosaccharides. A liquid mixture of the reduced malto-oligosaccharides will be stable, and, it is believed, relatively more stable than a liquid mixture of unreduced malto-oligosaccharides.
Further features and objects of the invention will be apparent from the following description and appended claims.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The method of the invention is applicable to any oligosaccharide species or mixture of a plurality of oligosaccharide species, and more generally to polysaccharide species and mixtures thereof. By “polysaccharide” and “oligosaccharide” are is contemplated any species comprised of plural saccharide units, whether linked by 1-4 linkages, 1-6 linkages, or otherwise. For example, the invention is applicable in the reduction of malto-oligosaccharides and mi
Antrim Richard L.
Barresi Frank W.
Grain Processing Corporation
Leydig Voit & Mayer LTD
Owens, Jr. Howard V.
Wilson James O.
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