Method for the embedding and encapsulation of components

Abstract

Controlled release, discrete, solid particles which contain an encapsulated and / or embedded component such as a heat sensitive or readily oxidizable pharmaceutically, biologically, or nutritionally active component are continuously produced without substantial destruction of the matrix material or encapsulant. A release-rate controlling component is incorporated into the matrix to control the rate of release of the encapsulant from the particles. The additional component may be a hydrophobic component or a high water binding capacity component for extending the release time. The plasticizable matrix material, such as starch, is admixed with at least one plasticizer, such as water, and at least one release-rate controlling component under low shear mixing conditions to plasticize the plasticizable material without substantially destroying the at least one plasticizable material and to obtain a substantially homogeneous plasticized mass. The plasticizer content is substantially reduced and the temperature of the plasticized mass are substantially reduced prior to admixing the plasticized mass with the encapsulant to avoid substantial destruction of the encapsulant and to obtain a formable, extrudable mixture. The mixture is extruded through a die without substantial or essentially no expansion and cut into discrete, relatively dense particles. Release properties may also be controlled by precoating the encapsulant and / or coating the extrudate particles with a film-forming component.

Description

FIELD OF THE INVENTION[0001]The present invention relates to a continuous process for producing controlled release, discrete, solid particles which contain an encapsulated and / or embedded component such as a heat sensitive or readily oxidizable pharmaceutically, biologically, or nutritionally active component.BACKGROUND OF THE INVENTION[0002]in encapsulating a component in a matrix, the matrix material is generally heated to a sufficiently high temperature to provide a plasticized mass which facilitates coating of the component. Upon cooling, the matrix material hardens or becomes solidified and protects the encapsulant from undesirable or premature reaction. However, heating of the matrix to plasticize it or to form a melt may deleteriously affect or decompose the encapsulant as well as the matrix material. Additionally, the mixing or high shear used to disperse the encapsulant uniformly throughout the plasticized matrix material may likewise adversely affect the matrix material or...

AI Technical Summary

Benefits of technology

[0013]The present invention provides a continuous process for producing controlled release, discrete, solid particles which contain an encapsulated and / or embedded component. The particles comprise a matrix material in which the active component is encapsulated or embedded. The matrix material is plasticized upon heating to form a melt. The active component is admixed with the melt without substantially deleteriously affecting or decomposing the encapsulant or the matrix material. The active component is admixed with the plasticized matrix material at low temperatures and under low shear mixing conditions to thereby avoid substantial destruction of or volatilization of active components. Additionally, high water contents may be employed so as to substantially reduce viscosity and facilitate substantial gelatinization of the starch without substantially destroying the starch molecules. Subsequent removal of at least part of the water prior to adding the encapsulant provides excessive drying or evaporation of the plasticizing liquid which may adversely affect the encapsulant content. The moisture reduction within the extruder also provides for the attainment of a formable composition capable of being formed into discrete, substantially uniform pieces. Extrusion of the matrix and active component blend may be performed without substantial expansion of the product thereby providing a high density product which is less susceptible to attack by aqueous or oxygen-containing mediums thereby providing a prolonged release time. The process of the present invention may be used to encapsulate heat sensitive components or readily oxidizable components, for example, pharmaceutically or biologically or nutritionally active components, without substantially destroying their activity. The products of the present invention may be edible for direct consumption or for incorporation into food products. In other embodiments of the invention, products, such as chemical or agricultural products such as pesticides, herbicides, fungicides, insecticides, rodenticides, or other products like detergents or flavorants, fragrances, and the like may be advantageously embedded or encapsulated to control or delay their release from their surrounding matrix.

[0014]In embodiments of the present invention, at least one additional ingredient or component may be used to control the release properties of the final product. The additional component may manage, control or affect the flow, diffusion or distribution of water or aqueous-based compositions into and within the final product particles. The additional ingredient or component for controlling the rate of release of the encapsulant may be a hydrophobic agent such as polyethylene, polyurethane, polypropylene, polyvinylchloride, polyvinylacetate, a fat, oil, wax, fatty acid, or emulsifier which increases the hydrophobicity of the matrix. The increased hydrophobicity helps to prevent or delays penetration of water or gastric juice into the matrix. Other ingredients which may be used to control the rate of the release are components which have a high water binding capacity which delay or prevent a fast dissolving of the matrix and thereby delay the release of the encapsulant into the matrix. Exemplary of high water binding capacity components which may be used are proteins, such as wheat gluten, gelatin, and casein, hydrocolloid gums, and the like.

[0015]In embodiments of the invention, matrix components may be added to increase the rate of release of the encapsulant. These rate increasing components may dissolve more readily in water than does another matrix material. Upon dissolution, permeability of the particles is increased, thereby increasing access to the encapsulant by the penetrating aqueous-based solvent.

[0016]In accordance with the method of the present invention, at least one plasticizable, matrix-forming material such as starch or polyvinylpyrrolidone may be admixed with a sufficient amount of a plasticizer such as water to reduce the melt or glass transition temperature of the plasticizable material, together with the additional release-rate controlling ingredient. The mix is heated above the melt or glass transition temperature of the plastifiable or matrix material, such as above the gelatinization temperature of a starch matrix ingredient, while conveying and mixing the ingredients within an extruder. The temperature is maintained sufficiently high for a sufficiently long period of time to at least partially gelatinize starch in the mixture. The additional ingredient which is used to control the rate of release of the encapsulant may be added before or after heating of the matrix material, such as starch.

[0017]After the matrix material is plasticized at a high moisture content to minimize molecular breakdown, at least some of the moisture may then be removed from the plasticized mass or cooked dough. The temperature of the plasticized mass may be reduced either by the moisture removal and / or by additional barrel cooling, the addition of inert gas, or by combinations of the above cooling methods. The plasticized or gelatinized mass having a reduced moisture content and lower temperature, is then conveyed toward a subsequent extruder barrel section while maintaining sufficiently low temperature to admix the encapsulant without thermally destroying the encapsulant. The encapsulant is admixed with the plasticized matrix under low temperature, low shear mixing conditions to distribute, coat, embed, or encapsulate the added active ingredient in the plasticized matrix material. Mixing is continued towards the extruder die while adjusting the product temperature for sufficient formability.

[0018]The admixture is extruded through the extrusion die and cut or otherwise formed into pieces or pellets with no or substantially no expansion of the extrudate. The extrudate or pieces may then be dried and then surface treated with a film-building substance to further encapsulate the extruded pellets or pieces. The film-building substance may also contain additional components that delay or prevent the access of light, oxygen, and / or water to the matrix. In embodiments of the invention, the one or more pharmaceutically, nutritionally, biologically or, chemically active ingredients may be precoated with a coating material such as shellac, zein, chitosan, chitin, an emulsifier or the like to further control the release properties of the encapsulant from the matrix material.

Problems solved by technology

Subsequent removal of at least part of the water prior to adding the encapsulant provides excessive drying or evaporation of the plasticizing liquid which may adversely affect the encapsulant content.

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