Encapsulated material with controlled release

Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Capsules

Reexamination Certificate

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Details

C424S463000, C424S476000, C424S484000

Reexamination Certificate

active

06290988

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to an encapsulated materiail, in which at least some of the material is released in a controlled manner during cooling aftcr a heat treatment, in particular for use in foodstuffs, cosmetic products, pharmaceuticals, animal feedstuffs, and hygiene products.
BACKGROUND
It is known from
Food Engineering
, 1983, page 59, to coat fortified rice grains with a layer consisting of methylcellulose (MC) and hydroxypropylcellulose (HPMC), with the object of preventing premature extraction of nutrients out of the rice grain during cooking. These cellulose derivatives arc soluble at low temperature (ambient temperature and body temperature) but are not soluble at high temperature. When the rice is introduced into boiling water, the cellulose derivatives ensure that escape of the nutrients is retarded during the cooking of the rice grain and less is therefore thrown away with an excess of cooking water, while the nutrients can still be released later, for example in the body. This reverse solubility behaviour in water, hereinafter referred to as LCST (LCST=lower critical solution temperature), is known for such cellulose derivatives and other polymers.
A disadvantage of this manner of encapsulating foodstuffs and other materials is that, on contact with water or another solvent at low temperature prior to the heat treatment, the materials can escape from the encasing, since the material having the LCST is soluble at low temperature.
It is also known to use polymers with LCST behaviour such as HPMC as a coating material. This polymer has been used widely because it is a food-grade film-forming polymer. HPMC is added to lipid materials in order to produce bilayer films which have a reduced water vapour permeability (see e.g. K; amper et al,
J. Food Sci
., 1984, 49, 1478-1481; Hagenmaier et al,
J. Agric. Food Chem
., 1990, 38, 17991803). Commonly two techniques are used to produce bilayer films. The first technique is by casting a lipid layer onto a preformed dry film of HPMC. The second technique is by emulsifying a melted lipid into a solution of HPMC and drying a thin layer of the emulsion. During drying, phase separation will occur, resulting in two different layers: HPMC on the product and the lipid on the outside.
All these systems have similar disadvantages as the method described in
Food Engineering
, 1983, 59. When heating the system, the lipid will melt and be lost in the product, leaving only a cellulosic derivative layer, which shows a release based on Fickian diffusion.
WO 89/05634 describes a sustained-release granular solid medicament form, consisting of a core granule of an excipient material such as lactose, coated with a layer of cellulose ether (HPMC), which is insoluble in hot water. The coating layer contains the active ingredient. The coating liquid, composed of the cellulose ether (5-30% by weight) and the effective ingredient, is applied at a temperature (80° C.) at which the cellulose ether is insoluble. The coated granules can be coated with a further outer layer of a wax-like material, such as paraffins, waxes, higher alcohols, etc. having a melting point between 40 and 90° C. In this method the LCST-behaviour of the cellulose ether is used in the production of the medicaments. A disadvantage of this method is that it is only applicable for heat-stable ingredients.
U.S. Pat. No. 5,310,558 discloses a programmed release oral solid pharmaceutical dosage form comprising a core, containing the active ingredient, optionally subcoated by a film-forming material (HPMC) with polyethylene glycol (PEG), subsequently coated with a layer comprising a mixture of a hydrophobic material (wax), 5-20% of a non-ionic surfactant and 5-30% of a water-soluble film-forming material such as HPMC. The main function of the water-soluble film-fonning material in the hydrophobic layer is to ensure the adhesion of the hydrophobic layer on the core. Heating the described system will result in melting of the hydrophobic layer, resulting in loss of the hydrophobic material of the dosage form. The system may have a further outer enteric coating consisting of methacrylic polymer and triacetin. The system will loose most of the water barrier and the active ingredients will be promptly released into the environment.
SUMMARY OF THE INVENTION
A method has now been found for encapsulating foodstuffs and other materials which does not have these disadvantages. In particular, this novel method of encapsulating is suitable for preparing products which should only release their ingredients after a heat treatment, such as sterilisation or pasteurisation, and a cooling period prior and/or subsequent to the heating treatment. The encapsulated material according to the invention is defined in the accompanying claims.
DETAILED DESCRIPTION OF THE INVENTION
According to the invention, the encapsulated material may first of all be coated with an inner layer of hydrophobic film-forming material which has the function of preventing diffusion of the encapsulated material through the layer having the LCST prior to termination of the heat treatment. This inner hydrophobic layer is primarily of benefit if the encapsulated material is a hydrophilic material. The hydrophobic material for this layer is chosen as a function of the conditions of use. It is preferably a material that is solid or semi-solid at ambient temperature, having a melting point between 30 and 50° C. Suitable materials are fats (semi-hard fats, cocoa butter and the like) and mono- and diglycerides, certain fatty acids such as lauric acid or mixtures of palmitic and stearic acid and the like, lecithins and derivatives and mixtures thereof. Said hydrophobic layer may be applied from the molten state or from a solution or dispersion to the material to be encapsulated, for example from a solution in an alcohol or an ether or from a dispersion in water. The thickness of said layer may be from a few &mgr;m to several mm, or, as a weight ratio, e.g. 10-10,000 ppm with respect to the encapsulated material.
Instead of encapsulating the material with an inner hydrophobic layer, the encapsulated material can also be mixed into said hydrophobic layer, for example as a granulated material or in dissolved form. The function of this material and the requirements imposed thereon are the same as stated above for the hydrophobic material. The mixture must have some non-deformability so that a layer containing LCST material can be applied to it. If the encapsulated material itself is hydrophobic (not soluble in water) the inner hydrophobic layer can be omitted.
Situated around this optional hydrophobic layer is the layer containing the material having low critical solution temperature (LCST). Said LCST material may be a material known for the purpose. Depending on the conditions of use, the LCST is between ambient temperature and the treatment temperature, for example between 30, preferably 40, and 100° C., in particular between 50 and 90° C. The separation or assembly of the polymer on increasing the temperature is a property of any polymer which contains polar or apolar residues in a suitable arrangement. Useful materials having an LCST are, for example, alkylated and/or hydroxvialkylated polysaccharides, such as hydroxypropylmethylcellulose (HPMC), for example Celacol®, ethyl(hydroxyethyl)cellulose (EHEC), hydroxypropylcellulose (HPC), methylcellulosc (MC) and mixtures thereof. Mixturcs of cellulose ethers with carboxymethylcellulose (CMC) also form suitable LCST polymers. Other polymers which exhibit LCST behaviour in water and which are suitable as coating material are: polymers of mono-or di-N-alkylated acrylamides, copolymers of mono- or di-N-substituted acryl-amides with acrylates and/or acrylic acids or mixtures of interpenetrating networks of the above-mentioned (co-)polymers. Suitable furthermore are polyethylene oxide or copolymers thereof, such as ethylene oxide/propylene oxide copolymers and graft copolymers of alkylated acrylamides with polyethylene oxide. Furthermore: poly-methacrylic acid, polyvinyl

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