Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Tablets – lozenges – or pills
Reexamination Certificate
2001-02-26
2003-11-18
Page, Thurman K. (Department: 1615)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Tablets, lozenges, or pills
C424S474000, C424S475000, C424S476000, C424S443000, C424S451000
Reexamination Certificate
active
06649188
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to starch compositions useful in forming flexible films. More particularly, it relates to film-forming compositions containing starch in combination with certain plasticizers.
Gelatin is a protein that forms thermo-reversible films. Gel masses composed of gelatin and a plasticizer such as glycerin are formulated to be liquid above room temperature, form a film when cast on a cooled surface, and re-melt when exposed to higher temperatures again. This ability to re-tackify enables encapsulation of liquid materials in gelatin soft capsules. Films formed from plasticized gelatin set very quickly and have high wet film strength. They are also very elastic with good clarity. Plasticized gelatin also has a relatively low viscosity, even when used at high solids concentrations. In addition, when gelatin is in the presence of water at room temperature, it swells but does not go into solution until heat is applied.
Although gelatin is useful in soft gel applications because of its rapid gelling ability, excellent film forming properties, and ability to impart oxygen impermeability, it has the disadvantages of high cost, limited availability, non-kosher status for food products and, at times, batch property variations. Because of these shortcomings, those industries where the need for gelatin is greatest have long sought means for replacing gelatin.
A number of food and industrial applications would benefit by an inexpensive and readily available structural material from a renewable resource, particularly one that is edible and/or biodegradable. Applications such as agricultural mulch, food packaging, and soft and hard gel capsules for cosmetics, pharmaceuticals and paintballs, need a material that is both strong and flexible under a range of use conditions. Applications such as adhesives, coatings, and caulkings do not have the rigorous strength requirements of free-standing films, but lack of brittleness can be just as important.
Starch meets many of the above requirements, and is an attractive raw material for these applications. Its tendency to brittleness, however, has generally blocked its use in these areas.
There have been some previous reports of plasticized starch films. Lourdin (D. Lourdin, G. D. Valle, P. Colonna, Carbohydrate Polymers 27 (1995) 261-270) incorporated up to 20% glycerol in starch films, but found that their mechanical properties were far inferior to those of synthetic film formers. They found that increasing the amylose content of the starch improved tensile strength. Arranitoyannis (Carbohydrate Polymers 36 (1998) 105-119) measured moderately high tensile values on starch films containing up to 25% polyhydric alcohols. When the plasticized films were oven dried to less than 6% moisture content, they became extremely brittle. Incorporating 15% hydroxypropyl units onto the starch molecules improved film flexibility. Shih (F. F. Shih, in “Chemistry of Novel Foods”, A. M. Spanier, M. Tamura, H. Okai, O. Mills, eds., Allured Pub. Corp., Carol Stream, Ill., Ch. 14, pp 179-186) reported tensile values on starch films containing up to 25% plasticizer, but reported that unplasticized films were too fragile for instrumental analysis. In general, increasing plasticizer increases film elongation while decreasing modulus and tensile strength. Other reports of starch-based films include J. D. Christen, U.S. Pat. No. 4,026,986, 1977; J. C. Rankin, I. A. Wolf, H. A. Davis, C. E. Rist,
Industr. Engr. Chem.
3 (1958), 120-123; I. A. Wolff, H. A. Davis, J. E. Cluskey, L. J. Gundrum, C. E. Rist,
Industr. Eng. Chem.
43 (1951) 915-919; A. M. Mark, W. B. Roth, C. L. Mehltretter, C. W. Rist,
Food Technol.
20 (1966), 75-77; W. B. Roth, C. L. Mehltretter,
Food Technol.
21, (1967), 72-74; L. Jokay, G. E. Nelson, E. L. Powell,
Food Technol.
21 (1967), 1064-1066; and J. L. Willet, B. K. Jasberg, C. L Swanson in “Polymers from Agricultural Coproducts, eds. M. L. Fishman, R. G. Friedman and S. J. Huange, pp 50-68, Amer. Chem. Soc., Washington D.C. These films are reported to be very sensitive to environmental humidity and tend to embrittle in low humidity environments.
Starch has also been included as a component in films containing proteins, such as gelatin, and carbohydrate-based hydrocolloids. Plasticizers are generally added to these systems as well. In most of these systems, starch is a secondary film former; the mechanical properties of the film reflect more strongly the properties of the other polymer(s) in the film. The following illustrates these types of systems. Laurent (L. Laurent, European Patent 0 547 551 A1, 1992), combines 5-40% starch with 5-40% gelatin and 10-40% plasticizer to make flexible, edible films. Arvanitoyannis (I. Arvanitoyannis, E. Psomiadou, A. Nakayama;
Carbohydrate Polymers
31, (1996) 179-192) developed edible films containing starch and sodium caseinate with up to 30% sugar or glycerol. Arvanitoyannis (I. Arvanitoyannis, A. Nakayama, S. Aiba,
Carbohydrate Polymers
36 (1998) 105-119) developed edible films composed of starch and gelatin with up to 25% polyol plasticizer. Psomiadou (E. Psomiadou, I. Arvanitoyannis, N. Yamamoto;
Carbohydrate Polymers
31 (1996) 193-204) studied films composed of starch, microcrystalline cellulose and methylcellulose containing up to 30% polyol plasticizers.
Certain films, such as coated paper or coated cardboard, are used in applications where resistance to penetration by water, oil or grease is important. Dog food bags are one example of such an application. Starch-based coatings have potential for such uses, but their tendency to be brittle has presented a major obstacle.
There is a long-standing need for improved film-forming compositions that do not have the shortcomings of prior art compositions.
SUMMARY OF THE INVENTION
One aspect of the present invention is a gelatin-free film-forming composition that comprises starch material and a primary external plasticizer. The starch material is selected from the group consisting of modified starch and waxy starch, and has a dextrose equivalent (DE) of less than about 1, and preferably has no measurable DE (using the Lane-Eynon method). The weight ratio of plasticizer to starch material in the composition preferably is at least 0.5: 1, more preferably is from about 0.5:1 to about 3:1, and most preferably is from about 1:1 to about 3:1. This composition optionally may include, in addition to starch and plasticizer, gums, hydrocolloids, synthetic polymers, and/or other additives, but is preferably free of protein. “Gelatin-free” and “protein-free” are used herein to mean that no more than trace amounts (e.g., no more than about 0.1 weight percent on a dry solids basis) of the listed material is present in the composition. Of course, there will often be protein present in the base starch itself. “Protein-free” and similar terms are used herein to mean that substantially no protein (e.g., no more than about 0.1 percent by weight of the total solids in the composition) is added to the composition beyond what that is inherently present in the starch.
The composition can be prepared with water, and preferably has a solids concentration of about 30-70%. (All composition percentages given herein are by weight unless otherwise stated.) In one preferred embodiment of the invention, the solids in the composition comprise 25-50% starch material and 50-75% plasticizer.
The starch material preferably comprises starch that has been chemically modified with a monoreactive moiety to a degree of substitution of at least about 0.015. In a particularly preferred embodiment, the starch material is selected from the group consisting of ether and ester derivatives of starch, such as hydroxypropyl, hydroxyethyl, succinate, and octenyl succinate starch. One specific embodiment of the invention comprises hydroxypropylated potato starch having a degree of substitution of about 0.015-0.30 and a molecular weight of about 200,000-2,000,000. Another specific embodiment of the invention comprises hydroxyethylated corn starch having a degree of sub
Gilleland Gregory M.
Harrison Michael D.
Patton Penelope A.
Turner Judy L.
A. E. Staley Manufacturing Co.
Baron L. Dinda
Page Thurman K.
Williams Morgan & Amerson P.C.
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