Colloid systems and wetting agents; subcombinations thereof; pro – Continuous or semicontinuous solid phase – The solid phase contains organic material
Reexamination Certificate
2002-02-20
2003-12-16
Lovering, Richard D. (Department: 1712)
Colloid systems and wetting agents; subcombinations thereof; pro
Continuous or semicontinuous solid phase
The solid phase contains organic material
C106S205720, C514S780000, C514S944000, C516S106000, C516S107000
Reexamination Certificate
active
06664301
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates, generally, to a method for the use of glycol additives in natural gum hydrogels.
More particularly, the present invention concerns the inclusion of glycols in hydrogel formulations to enhance the strength of the gels and reduce the tendency for syneresis.
2. Description of the Prior Art
It is well known that while certain polysaccharide gums can be used to form gels, others will not form gels individually. However, certain combinations of polysaccharide gums have been found to form gels even though one or more of the gums will not form a gel on its own.
A synergistic effect has been found with certain polysaccharide gums, whereby the addition of a non-gelling gum to a gelling gum results in a significant increase in gel strength. Gels can also be produced from certain combinations of gums, even where none of the individual gums will form gels. In this manner, combinations of polysaccharide gums, or polysaccharide gums with other gelling agents, can produce gels with desirable textures and/or strength. Carob gum, will not gel on its own, but in combination with agar or carrageenin, will produce a much stronger and more elastic gel than is otherwise obtained from agar or carrageenan alone. Moreover, xanthan gum, which will not form a gel on its own, but in combination with certain galactomannan gums, such as carob, tara and cassia gums (which will also not form gels on their own), nevertheless produces useful gels. Glucomannan gums will produce thermo-irreversible gels under strongly alkaline conditions. In combination with xanthan gum, however, strong thermo-reversible gels can be produced under acid to neutral conditions.
It has also been observed in the literature that combinations of gellan with small amounts of other gums, such as xanthan, guar or carob gum, will reduce syneresis in a gel, but no marked improvement in the strength or texture of the gel is observed.
U.S. Pat. No. 4,517,216 (Shim), the disclosure of which is hereby incorporated by reference, discloses that the only gelling agent that produces any synergistic improvement in gel strength, when used in combination with gellan, is gelatin. This prior art patent discloses that many gelling agents were tested by the patentees, in combination with gellan, in an attempt to achieve a synergistic increase in gel strength, including carrageenan, carob gum, sodium alginate, corn starch and pectin. Of these only carrageenan provided a small increase in gel strength, but this was considered to be primarily because of the presence of various salts in the carrageenan affecting gelling of the gellan, rather than the carrageenan itself. All of the other agents tested reduced gel strength. Moreover, the effect with gelatin was only noticed with low acetyl gellan. Gums obtained from natural sources, be they botanical or bacterial in origin, are generally characterized as polymers of five- or six-carbon chain sugar monomers, linked to each other by oxygen bridges derived from alcohol oxygens on the respective monomeric sugars. The sugars themselves, be they glucose, mannose, xylose, galactose, or the like, are generically classified as polyols or polyhydric alcohols, which are multicarbon aliphatic molecules containing three or more alcohol (i.e. —OH) groups. When a molecule contains but two such —OH groupings, it is termed a glycol.
It is presumed that the ability of certain gums to form gels with other gums, while themselves being individually incapable of doing so, relates to the particular steric conformation of the monomeric sugar components of the chain, and their spacial contiguity with sugar moieties of adjacent sugar polymer chains. The close approach of the two units could lead to the formation of so-called “hydrogen bonds” between the —OH groups of these units, which would result in a stabilization of the hydrated gum mass into a solid or semi-solid structure, rather than the original freer-flowing liquid. Hydrogen bonds, by convention, are not actual chemical bonds within a single molecule but are electrostatic attractions between adjacent molecules, where one atom or functional group in one molecule, with a relative deficiency of electrical charge, is attracted to an atom or functional group with a high localization of electrical charge in another. Hydrogen bonding, for example, is responsible for the liquid structure of water, where the hydrogen, “H,” of an “O—H” (in H
2
O, or H—O—H) of one molecule is attracted to the negatively-rich oxygen, “O” of an adjacent H—O—H molecule. Without such intermolecular attractions, the small H
2
O molecule would certainly be a gas, rather than a liquid.
In contrast, a non-gelling gum, which may have more or less aligned chains in the aqueous solution, could not form such intermolecular bonding, and thus not orient itself into three-dimensional structures. However an aqueous combination of different sugar polymer structures could well allow for the interchain weaving, and attractions characteristic of the hydrogels.
In an effort to strengthen certain hydrogel combinations being investigated by prior art artisans, and to possibly reduce the syneresis common to many of the gels being investigated, it seemed to logically follow for the skilled artisan to consider the use of non-sugar glycols and polyols as additives to effect a strengthening of a weaker hydrogel structure. A molecule with at least two alcoholic groupings, i.e., two “—OH” groups, could theoretically simulate the action of sugars, where one of the OH's would be attracted to a potential hydrogen-bonding site on one sugar chain, while the other would be attracted to a similar site on an adjoining chain. Were this to happen, the entire gel structure might be firmed up.
In reviewing the prior art for such use of glycols and polyols in connection with hydrogels, mention has been made of the well-known use of glycerin, and related multi-hydroxy compounds, such as pre-“wetting” agents of gum powders, prior to exposure to water. Such use allows for a much easier dispersion of most solid gum powders in water, since the initial contact of a gum powder mass with water can often lead to a gummy surface on the mass through which additional water cannot easily penetrate, so as to hydrate the balance of the powder. Indeed the prior art has often taught the use of small quantities of simple alcohols (e.g. isopropanol) or glycerin as an initial dispersant of thickening agents or gums.
U.S. Pat. No. 4,457,908, for example, discloses the use of glycerin as an initial dispersant of the carrageenan gellant in formulating a toothpaste formulation, which is thereafter stabilized by exposure to microwave radiation.
U.S. Pat. No. 4,318,746 teaches the use of an electrolyte for increasing the rigidity or conductivity of mixed polymers, such as those of kappa carrageenan and hydroxy-propylmethylcellulose, and suggests that, if desired, glycerol (glycerin), propylene glycol or other polyhydric alcohols may be used to reduce the rate of evaporation (of water) from the gel. No teaching or suggestion, however, is made to the possible role of such alcohols as firming or strengthening agents.
U.S. Pat. No. 5,002,934, similarly, makes reference to a skin-moisturizing carrageenan gel containing 1% glycerol; a common use of this polyhydric alcohol in the cosmetic field. Glycerin is also recommended for use as a plasticizer for dried films created from two gums, konjac and agar, and gelatin, but, again, is not associated with strengthening effects. In a similar vein, The FMC BioPolymer Company recommends the use of glycerin as a 1%-component of water in which to dissolve its konjac flour, wherein the glycerin serves as a plasticizer.
A similar application, as a plasticizer, is referenced in U.S. Pat. No. 5,543,164, wherein glycerol, sorbitol or polyethylene glycol is included in a food product coating.
In all of these prior art teachings, no reference is made to the use of glycols or polyols with respect to their possible use for gel firming or strengthenin
Lovering Richard D.
Schindler Edwin D.
LandOfFree
Method for using glycol additives to texturally modify... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for using glycol additives to texturally modify..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for using glycol additives to texturally modify... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3179706