WO2004035885A1

WO2004035885A1 - Wet spinning process

Info

Publication number: WO2004035885A1
Application number: PCT/EP2003/011340
Authority: WO
Inventors: Cornelis G. De Kruif; Frank Driehuis
Original assignee: Nizo Food Research B.V.
Priority date: 2002-10-13
Filing date: 2003-10-13
Publication date: 2004-04-29
Also published as: AU2003276099A1

Abstract

The invention relates to a process of producing a biopolymer fibre or biopolymer film loaded with one or more chemically or biologically sensitive materials which are encapsulated or immobilized in the biopolymer using a wet spinning technique in substantially aqueous media, to a biopolymer fibre or biopolymer film loaded with one or more chemically or biologically sensitive materials which is obtainable by such process, and to the use of such loaded biopolymer fibres or biopolymer films in the production of food, feed, nutritional supplement, home and personal care products, pharmaceutical and biomedical preparations.

Description

Wet spinning process

Field of the invention The present invention relates to a process of producing biopolymer fibres comprising bioactive materials, e.g. gelled polysaccharides or gelled proteins, to biopolymer fibres obtainable by such process and their use in the production of food, feed, pharmaceutical and biomedical preparations, home and care products, and the like.

Background of the invention

Many materials that are used as ingredients in food, feed, nutritional supplements, pharmaceutical preparations, home and care products (i.e., cosmetics, tooth pastes, shampoos, detergents, etc.), have a low stability. These materials may wholly or partially degrade, volatilize, change in conformation, lose activity, lose viability, etc., under conditions that are used for the production of these ingredients or during their storage, as well as during the production and storage of products containing such ingredients, or in the human or animal intestines. Stability of chemically or biologically sensitive materials, such as bacteria, yeasts, moulds, enzymes, proteins and peptides, vitamins, antioxidants, fats, fatty acids, carbohydrates, flavours, biologically active molecules, and the like, is dependent on physico-chemical factors such as temperature, water activity and acidity, and/or the presence of substances in the surrounding environment that may degrade, inactivate or react otherwise with the material, for example oxidizing agents, bile acids, enzymes and micro-organisms.

Modern technologies that aim to enhance the stability of such sensitive materials include dehydration techniques such as spray drying, fluidized bed drying, freeze drying and desiccation drying, freezing and refrigeration, vitrification, and encapsulation techniques.

In encapsulation techniques a chemically or biologically sensitive material is usually entrapped in or linked to a solid carrier particle. In human and animal nutrition food, feed and pharmaceutical and biomedical preparations, home and care products, the carrier particles are generally composed of proteins, carbohydrates, fats, or mixtures thereof. Encapsulated materials may be coated by one or more layers of coating materials which are generally composed of proteins, carbohydrates, fats, or mixtures thereof.

An advantage of encapsulation techniques in addition to enhancing stability of chemically or biologically sensitive materials is that release of the encapsulated material can be controlled in time and place. For example, encapsulated food flavour can be released in the mouth by elevating the temperature or pressure and encapsulated so- called probiotic bacteria can be released in the intestines.

Current encapsulation technologies usually involve encapsulation of chemically or biologically sensitive materials in particles or beads. Encapsulation methods include processes such as spray drying and spray chilling, controlled atmosphere spraying, complex coacervation, and the like. Alternatively, materials may be immobilised on or encapsulated in discrete particles or beads of biopolymer gels, such as alginate, carrageenan, gelatin, collagen, and the like Immobilisation of cells in biopolymer gel particles is a well-known technique.

Alginates are frequently used as biopolymer gels. Dimensions of discrete particles formed in these methods generally range between about 100 μm and about 5000 μm.

For example, U.S. Patent 4,352,883 discloses a method of encapsulating a chemically or biologically active core material in a semi-permeable membrane that is permeable to small molecules for contact with the core material but is impermeable to potentially deleterious large molecules. The method includes suspending the material in an aqueous solution containing a water-soluble substance capable of gelling, e.g. sodium alginate, forming this suspension into droplets and contacting the droplets with a solution of multivalent cations, e.g. Ca²⁺, to gel the droplets into discrete particulate capsules. The gelled substance may then be cross-linked to form an irreversible water-insoluble layer around the capsules.

U.S. Patent 4,647,536 discloses a method of encapsulating viable prokaryotic or eukaryotic cells in biopolymer beads with retained ability of growth, by suspending the cells in an aqueous solution of agar, agarose or fibrinogen, and dispersing the aqueous solution in soybean oil, paraffin oil or liquid silicone. Upon contact with said water-insoluble dispersion medium, the dispersed biopolymer is gelling to form polymer beads encapsulating said viable cells.

The stability of encapsulated particles produced according to the methods disclosed in these patents and similar methods appear to be limited due to the high water activity of the particles. Methods have been developed to increase the stability of encapsulated particles produced with gellable substances.

For example, U.S. Patent 4,443,538 discloses a method for stabilizing enzyme-containing cells immobilized in alginate gel by contacting the gel with glycerol in a ratio (cells to glycerol) of 2:1 to 1 :5, resulting in a partial dehydration of the gel. This lowers the water activity of the environment surrounding the cells immobilized in the gel, thus enhancing their stability.

Other methods to dehydrate biopolymer gel particles include conventional drying processes such as air drying, spray drying, fluidized bed drying, freeze drying and desiccation, as documented for example in U.S. Patents Nos. 5,389,532 and 4,755,468.

However, micro-organisms entrapped in biopolymer gels and dried using such drying methods have shown unsatisfactory viability or activity after rehydration.

Methods have been developed to enhance the viability or activity of microorganisms in dried biopolymer gel particles after rehydration. For example, U.S. Patent 5,389,532 discloses a method for the preparation of micro-organisms in at least partially hydrated gels, said micro-organisms exhibiting an improved viability after rehydration, in which the micro-organisms-containing polysaccharide gel particles are at least partially dehydrated prior to the drying process by soaking the particles in an aqueous solution containing a high concentration of a hydrophilic substance, such as a sugar or glycerol. The current methods for producing chemically or biologically sensitive materials in a biopolymer gel have in common that beads or particles are formed. A major drawback is that these materials are all produced by batch processes which are laborious and therefore expensive. For example, the particles have to be collected from the solution in which gelation takes place and are usually purified to remove substances originating from this solution.

Wet-spinning is one of the oldest known spinning processes in the field of manufacturing natural and, at a later stage, synthetic fibres. The wet-spinning technique is used for fibre-forming polymers that are dissolved in an aqueous or non-aqueous first solvent, which is pumped through the tiny holes of a device called spinneret into a coagulation bath, containing an aqueous or non-aqueous second coagulating solvent to coagulate the polymers from the first solvent. As the dissolved polymer emerge from the holes of the spinneret into the second solvent, the polymer precipitates to form a fibre. In a similar way but with a device with narrow slits instead of the spinneret polymer films are produced, for example as described by A. Frinault et al. in J Dairy Science 62, 744-747 (1997). The following applications which are believed to be relevant to the present invention are highlighted.

U.S. Patent No. 4,246,221 discloses a process for the preparation of cellulosic fibres (e.g. fibres currently known under the trade name Lyocell®) by injecting a solution of cellulose into a non-solvent for cellulose, which causes the cellulose to precipitate and form a fibre. U.S. patent 4,320,081 discloses a process for the preparation of polyamide fibres (e.g. aramide fibres known under the trade name Twaron®) by injecting a solution of polyamide in concentrated sulphuric acid into dilute sulphuric acid, which causes the polyamide to precipitate and form a fibre. For general references to wet spinning (also known as solvent spinning) reference is made inter alia to the Encyclopaedia of Polymer Science and Engineering, published by John Wiley and Sons, Inc.

EP-A-1 090 928 discloses a process for preparing a fibrous polymer loaded with one or more bioactive agents using a wet-spinning technique, wherein a solution of the polymer in a suitable first solvent is provided, an aqueous solution of the bioactive agent or agents is added to the polymer solution to obtain a water-in-oil emulsion, said water-in-oil emulsion is immersed in a suitable second solvent by injecting the emulsion through a nozzle into the second solvent, the first solvent is allowed to migrate into the second solvent to obtain a solid, fibrous polymer loaded with the bioactive agent or agents. According to the disclosure the polymer must be insoluble In the second solvent, the second solvent should be well-miscible with the first solvent and preferably be immiscible with water. Examples of polymers to be loaded with one or more bioactive agents are synthetic amphiphilic block copolymers, comprising hydrαphiUc and hydro- phobic blocks. Such copolymers are synthesized by forming covalent bonds between a hydrophilic and a hydrophobic polymer. The resulting copolymers loaded with bioactive agent(s) are said to be useful in pharmaceutical and biomedical applications, for instance as a carrier for controlled drug release or as scaffold in tissue engineering.

However, the method disclosed in EP-A-1 090 928 is not suitable or at least not desirable and certainly not preferred for the encapsulation or immobilisation of chemically or biologically sensitive materials that are to be used in food, feed and nutritional supplements in edible, food-grade polymers. Firstly, because of the organic (i.e. non-aqueous) solvents in the process which are not allowed in products intended for human or animal consumption (because of their toxicity or other adverse effects) and, secondly, because none of the solvents that are suitable to dissolve edible, food-grade polymers, such as alginate and casein, is immiscible with water. Therefore, an object of the present invention is to provide a method for the encapsulation or immobilisation of chemically or biologically or pharmaceutically active material, such as prokaryotic or eukaryotic cells, enzymes or other chemically or biologically sensitive materials, in biopolymer fibres in a continuous process which does not have the drawbacks, or to a substantially lesser extent, as the prior art methods described above. Summary of the invention

Surprisingly, it now has been found that the wet-spinning technique can be conveniently and effectively used for the encapsulation or immobilisation of cells, enzymes and other chemically or biologically sensitive materials in biopolymers. The present process uses wet-spinning technology employing aqueous solutions to provide long fibres of a biopolymer gel loaded with viable micro-organisms, enzymes, and other chemically or biologically sensitive materials.

Accordingly, the invention specifically relates to a process for preparing biopolymer fibres or biopolymer films, loaded with one or more chemically or biologically sensitive materials which are encapsulated or immobilized in the polymer which comprises the following steps: mixing an aqueous solution of said biopolymer and an aqueous suspension or solution of said one or more chemically or biologically sensitive materials to be encapsulated or immobilized to form a first aqueous biopolymer solution or suspension of the one or more chemically or biologically sensitive materials; injecting said first aqueous biopolymer solution or suspension of said one or more chemically or biologically sensitive materials into a second aqueous solution containing substances that cause coagulation or gelation of the polymer; allowing said substances that cause coagulation or gelation of said biopolymer which are present in said second aqueous solution to contact said biopolymer to form a biopolymer fibre or a biopolymer film loaded with said one or more chemically or biologically sensitive materials.

In a preferred embodiment of the invention said process further comprises optionally guiding said loaded biopolymer fibres or films through one or more subsequent liquid media (preferably aqueous but not excluding non-aqueous media) containing substances that are suitable to give said biopolymer fibres an additional treatment, such as coating, crosslinking, hardening, plasticizing, dying, dehydration or preservation treatments.

In another preferred embodiment of the process according to the invention said biopolymers and/or said one or more chemically or biologically sensitive materials are concentrated. Preferably, at least about 50% of the water is removed from the aqueous solution containing said biopolymer and said one or more chemically or biologically sensitive materials, more preferably about 85%, and most preferably about 96%.

In another preferred embodiment of the present invention a biopolymer fibre or biopolymer film is provided loaded with one or more chemically or biologically sensitive materials which is obtainable by a wet spinning process as herein described using substantially aqueous solutions or suspensions.

In a further preferred embodiment of the invention the use of a biopolymer fibre or a biopolymer film is provided as an ingredient in the preparation of a foodstuff, a feed, a nutritional supplement, a home and personal care composition, a pharmaceutical or biomedical composition.

These and other aspects of the present invention will be more fully outlined in the detailed description below.

Detailed description of the invention

As mentioned above, the main object of the present invention is to provide a method for the encapsulation or immobilisation of chemically or biologically active materials, such as prokaryotic or eukaryotic cells, enzymes or other chemically or biologically sensitive materials, in biopolymer fibres in a continuous process. The method accomplished by the present invention is based on a wet spinning technique which could be modified so as to use only aqueous solutions or suspensions, thus enabling this technique for encapsulation or immobilisation of chemically or biologically sensitive or biologically active materials in biopolymers.

As used herein, the term "chemically or biologically sensitive material", as well as the terms "chemically or biologically active material" and "biologically active sensitive material", are all meant to indicate biologically-active organisms or substances including prokaryotic cells such as bacteria for example lactic acid bacteria, eukaryotic cells, such as yeasts, moulds, cell lines, plant cells, enzymes, proteins, peptides, vitamins, antioxidants, fats, fatty acids, oils (preferably a vegetable or animal oil), carbohydrates, flavours, and the like. These terms also include pharmacologically active materials which can be used, e.g., in pharmaceutical or biomedical preparations.

The term "biopolymer", as used herein, includes water-soluble carbohydrates, such as alginates, for example sodium aliginate, xanthan, carrageenan, or other water- soluble polysaccharides, proteins or peptides (usually poly peptides), such as caseins, for example sodium caseinate, whey proteins, soy proteins or gelatin, and protein particles, such as casein micelles or whey protein aggregates, for example whey protein aggregates as described by R. Tuinier, J.K.G. Dhont and C.G. De Kruif in Langmuir 16, 1497-1507 (2000). A preferred group of biopolymers are edible food-grade biopolymers.

The process of the invention is suitably carried out by preparing an aqueous solution of a biopolymer, as defined above. The concentration of the biopolymer is not critical, but is preferably ranging between 1 and 500 g/l, most preferably between 10 and 200 g/l.

To promote dissolving the aqueous solution of the biopolymer may be made at elevated temperatures, for example up to about 80°C while agitating. Similarly, a second aqueous solution or suspension is made containing one or more chemically or biologically sensitive materials of choice, as defined above. Care has to be taken to avoid extreme heating or other conditions while dissolving or suspending the chemically or biologically sensitive material(s) in order to maintain their aimed properties.

The two solutions, or the solution and the suspension, as the case may be, are then mixed together, usually at a temperature ranging from room temperature and slightly elevated temperature to form a first aqueous biopolymer solution or suspension of the one or more sensitive materials.

It will be understood to those skilled in the art that an alternative way to prepare the first aqueous biopolymer solution or suspension of the one or more sensitive materials is to dissolve or suspend both agents in the same solution.

The next step in the present process is the immersion of the first aqueous biopolymer solution or suspension in a second aqueous solution by injection through a nozzle or slit (to produce a fibre or film, respectively). The diameter and shape of the nozzle or slit can be varied to obtain fibers or films of different thickness and shape. The injection itself will usually be driven by a pressure by virtue of which the the first aqueous biopolymer solution or suspension is transported through the nozzle or slit into the second aqueous solution. The injection may for instance be accomplished by use of a syringe or an extruder. The amount of the second aqueous solution is not critical. It should be at least sufficient for the first aqueous biopolymer solution or suspension to be completely immersed in it. The upper limit will generally be chosen on the basis of economic considerations.

The second aqueous solution is to be chosen such that it causes coagulation or gelation of the biopolymer of the first aqueous solution. Parameters that influence coagulation or gelation of biopolymers depend on the type of polymer and include for instance pH, salt content and temperature of the solution. For example, to prepare fibers of alginate according the present invention the second aqueous solution is made up of a solution of a salt of a polyvalent cation. Suitable salts include calcium chloride, especially a calcium chloride solution whose molality is from 0.1 to 1.0 M. In another example, to prepare fibers of caseinate the second aqueous solution is made of a solution with a pH of around the isoelectric point (pi) of casein. Suitable solutions include solutions containing acetic acid or lactic acid and sodium sulfate. An example of a suitable solution is a solution containing 50 g/l of lactic acid (a suitable range being from about 5 to about 250 g/l) and 0.25 M sodium sulfate (a suitable range being from about 0.05 to about 1.0 M), adjusted to pH 4.2 (a suitable range being from about 3 to about 5) with, for example, sodium hydroxide. Other methods suitable of causing coagulation or gelation of polymers include for instance gelation of gelatin at lower temperature, coagulation of whey protein aggregates at low pH conditions, and coagulation of polysaccharides by immersion in an aqueous solution of a lower alcohol.

Upon immersion of the biopolymer solution containing the chemically or biologically sensitive material into the second solution a fibre is formed. The fibre is removed from the second aqueous solution by any conventional manner. In a preferred embodiment of the invention, the fibre is passed through the second aqueous solution by guiding the fibre to driven rollers, which is a conventional method in wet spinning technique. Next, the fibre is guided in a similar way through a stream of air to remove adhering liquid and dry the fibre. The fibre can also be guided through additional solutions to give the fibre a desirable treatment. Such post-spinning treatments include treatments with crosslinking agents to strengthen the biopolymer fibre such as formaldehyde or transglutaminase, treatments with substances that are suitable for coating of the fibre, treatments with dye agents to dye the fiber, and treatments with agents that are capable of dehydration of biopolymers gels, for instance aqueous solutions of high osmolality or aqueous solutions of suitable organic solvents, such as glycerol and propylene glycol. The fibre is optionally subjected to methods known to preserve the activity of the biologically active materials, for example refrigeration or freezing, vitrification, or drying methods such as air drying, fluidized bed drying, freeze drying or desiccation. It will be understood to those skilled in the art that variations and modifications in the above-described process and procedures may be made without departing from the scope or nature of the present invention.

The objects and advantages of the encapsulation and/or immobilisation process ot the present invention (hereinafter also collectively referred to as "immobilisation process" or "immobilisation") are:

- to encapsulate or immobilize chemically or biologically sensitive materials of interest, in particular, but not exclusively, microorganisms;

- to partially remove water from an aqueous suspension or solution containing the chemically or biologically sensitive materials of interest; - to protect the chemically or biologically sensitive materials of interest against loss of biological activity (e.g., viability of living cells; activity of enzymes) during further processing and storage;

- using fibers to protect said chemically or biologically sensitive materials of interest - to prevent denaturation of proteins, in particular enzymes;

- to prevent chemical of physical deterioration of molecules or molecular clusters, aggregates or crystals;

- to increase shelf-life of the sensitive biological materials of interest;

- to allow targeted release of the sensitive materials of interest due to environmental triggers such as temperature, pH, salt, hydration, dehydration, solvent properties, enzymatic reaction, catalytic reaction light, radiation;

- applying other polymers than alginates as alternatives or more advantageous means (including having surprisingly better properties) for the immobilization of said chemically or biologicaslly sensitive materials using wet spinning techniques - to release sensitive materials of interest in the intestines.

Other features of the invention will become apparent in the course of the following descriptions of exemplary embodiments which are given for illustration to the invention and are not intended to be limiting thereof. Example 1 illustrates the preparation of a polysaccharide polymer fibre containing viable micro-organisms by using sodium alginate as the polysaccharide and a strain of the lactic acid bacterium Lactobacillus delbrueckii ssp. bulgaricus as the micro-organism. Example 2 illustrates the preparation of a protein polymer fibre containing viable microorganisms by using sodium caseinate as the protein and a strain of Lactobacillus delbrueckii ssp. bulgaricus as the micro-organism. Example 3 illustrates the preparation of a sodium alginate polymer fiber containing enzymes exemplified animal rennet containing calf chymosin and bovine pepsin. Example 4 illustrates the preparation of a sodium alginate polymer fibre containing the bitter tasting antioxidant naringin, as an example of encapsulation/immobilisation of a non-cellular, non- protein bioactive sensitive material. Example 5 illustrates the preparation of a sodium alginate polymer fibre containing oil droplets.

Examples Example 1 Encapsulation of bacteria in an alginate polymer

Prior to encapsulation, a strain of Lactobacillus delbrueckii ssp. bulgaricus isolated from a yoghurt sample was cultivated in 1 I of MRS broth (Merck, Darmstadt, Germany), incubated at 37°C for 24 hours. The bacteria were concentrated by centrifugation and suspended in a 25 ml of an aqueous solution containing peptone at a concentration of 1 g/l and sodium chloride at a concentration of 8.5 g/l (referred to as PS solution) to a final number of about 2.10¹⁰ colony forming units per ml. Viable lactic acid bacteria were enumerated with the standard plate count technique, using LBA medium. LBA medium contained tryptone (9.2 g/l), yeast extract (2.8 g/l), meat extract (4.6 g/l), tomato juice (37 ml/I), glucose (19 g/l), Tween 80 (0.9 ml/I), K₂HPO₄ (1.9 g/l), sodium acetate trihydrate (8.4 g/l), glacial acetic acid (0.7 g/l), and agar (14 g/l) and was adjusted to a pH of 6.1. Inoculated plates of LBA medium were incubated for 3 days at 37°C. The concentrated bacteria suspension was mixed with 125 ml of an aqueous solution containing 36 g/l of sodium alginate (Sigma, St. Louis MO, USA). This mixture was added to the feed vessel of a wet spinning apparatus and pumped through a spinneret into a tank with the coagulation solution. The coagulation solution was an aqueous solution of 20 g/l calcium chloride. The coagulated alginate fibre emerging from the spin orifice was passed through the calcium chloride solution and then passed over a guide to driven rollers. During the latter step the fibre was stretched and dried by a stream of air with a temperature of 30°C.

Using this wet-spinning and drying procedure about 85% of the water was removed from the sodium alginate solution with bacteria. Lactic acid bacteria immobilized in the alginate fibre were enumerated as described previously after dissolving the fibre in PS solution with 0.005 M sodium citrate. Comparison of the number of viable lactic acid bacteria in the fibre and the alginate solution prior to the wet-spinning process showed a survival of about 95% of the bacteria.

To increase the stability of the encapsulated bacteria further dehydration of the biopolymer gel may be conducted using known techniques, such as described in U.S. Patents Nos. 4,443,538; 4,755,468; 5,389,532; or conventional methods, for example freeze drying, dessication or air drying.

Example 2 Encapsulation of bacteria in a casein polymer

Two ml of a concentrated suspension of the lactic acid bacterium Lactobacillus delbrueckii ssp. bulgaricus, prepared as described in Example 1 , was mixed with 50 ml of an aqueous solution of 100 g/l of sodium caseinate (Sigma, St. Louis MO, USA). Two ml of this mixture was poured into a 2 ml syringe equipped with a 0.5 mm diameter needle (Becton Dickinson 25 GA) and injected into the coagulation solution. The coagulation solution was an aqueous solution containing 5% (w/v) lactic acid and 0.25 M sodium sulfate, adjusted to pH 4.2 with sodium hydroxide. A coagulated caseinate fibre was formed in the coagulation solution. After 2 min incubation, the fibre was transferred to a solution containing 0.25 M sodium sulfate to remove the lactic acid from the fibre. After 2 min incubation, the fibre was removed from the solution and placed on filtration paper (Whatman 40) to remove surplus liquid. Lactic acid bacteria immobilized in the caseinate fibre were enumerated as described previously after dissolving the fibre in a solution containing 0.025 M monosodium phosphate and 0.9% (w/v) sodium chloride, adjusted to pH 7.3 with sodium hydroxide. Comparison of the number of viable lactic acid bacteria in the fibre and the caseinate solution prior to the wet-spinning process showed a survival of the bacteria of more than 100%.

Example 3

Encapsulation of enzyme in an alginate polymer This example illustrates the encapsulation/immobilisation of a non-cellular, proteinaceous bioactive sensitive material according the present invention. Twenty ml of a calf rennet preparation containing chymosin and pepsin in an enzyme activity ratio of 80:20 (Kalase®; CSK Food Enrichment, Leeuwarden, The Netherlands) was mixed with 75 ml of an aqueous solution containing 40 g/l of sodium alginate (Sigma, St. Louis MO, USA). This mixture was added to the feed vessel of a wet spinning apparatus and pumped through the spin orifice into a tank with the coagulation solution, comprising an aqueous solution of 20 g/l calcium chloride, as described in Example 1. The coagulated alginate fiber emerging from the spin orifice was passed through the calcium chloride solution and then passed over a guide to driven rollers. During the latter step the fiber was stretched and dried by a stream of air with a temperature of 20°C.

The proteolytic activity immobilized in the alginate fibre was determined as described by S. Visser, et al., Neth. Milk Dairy J. (1988) 42:221-232, after dissolving the fibre in a solution containing 0.05 M sodium acetate, 1 M sodium chloride, 2.5 g/l polyethylene glycol 20000 and 0.05 M sodium citrate, adjusted to pH 5.2 with glacial acetic acid. Comparison of the proteolytic activity in the fibre and the alginate solution prior to the wet-spinning process showed that of 70% of the enzyme activity was recovered in the dried fibre.

Example 4 Encapsulation of naringin in an alginate polymer Naringin (Sigma, St. Louis MO, USA), which is poorly soluble in water, was added to water to a final concentration of 100 g/l. Five g of the naringin suspension was mixed with 25 ml of an aqueous solution containing 30 g/l of sodium alginate (Sigma, St. Louis MO, USA). Two ml of this mixture was poured into a 2 ml syringe equipped with a 0.5 mm diameter needle and injected into the coagulation solution, comprising an aqueous solution of 20 g/l calcium chloride, as described in Example 2. A coagulated alginate fibre was formed in the coagulation solution. Microscopic visualisation showed that naringin crystals were entrapped in the alginate fibre.

Example 5

Encapsulation of a liquid finely dispersed in an aqueous solution in an alginate polymer

A dispersion was prepared containing 5% vegetable oil, 1% whey proteins and

1% gum arabic. One ml of the dispersion was mixed with 20 ml of an aqueous solution containing 30 g/l of sodium alginate (Sigma, St. Louis MO, USA). A coagulated alginate fibre was formed as described in Example 4. Microscopic visualisation showed that oil droplets were entrapped in the alginate fibre.

Claims

Claims 1. A process for preparing a biopolymer fibre or biopolymer film, loaded with one or more chemically or biologically sensitive materials which are encapsulated or immobilized in said biopolymer which process comprises the following steps: mixing an aqueous solution of said biopolymer and an aqueous suspension or solution of said one or more sensitive materials to be encapsulated or immobilized to form a first aqueous polymer solution or suspension of said one or more chemically or biologically sensitive materials; injecting said first aqueous polymer solution or suspension of said one or more chemically or biologically sensitive materials into a second aqueous solution containing substances that cause coagulation or gelation of said biopolymer; allowing said substances that cause coagulation or gelation of said biopolymer which are present in said second aqueous solution to contact said polymer to form a biopolymer fibre or biopolymer film loaded with said one or more sensitive materials.

2. A process according to claim 1 , further comprising subjecting said loaded biopolymer at least one additional treatment selected from the group consisting of a coating, crosslinking, hardening, plasticizing, dying, dehydration and preservation treatment.

3. A process according to claim 2, which comprises guiding said loaded biopolymer fibre or bioplymer film through one or more subsequent liquid media containing substances that cause said at least one additional treatment.

4. A process according to claim 3, wherein said one or more subsequent liquid media are substantially aqueous media.

5. A process according to any one of claims 1 to 4, wherein said first aqueous biopolymer solution or suspension is concentrated prior to injecting into said second aqueous solution.

6. A process according to any one of claims 1 to 4, further comprising subjecting said biopolymer fibre or biopolymer film loaded with said one or more chemically or biologically sensitive materials to a water-removing step.

7. A process according to claim 5 or 6, wherein at least about 50% of the water is removed from said first aqueous polymer solution or suspension of the one or more sensitive materials or from said biopolymer fibre or biopolymer film loaded with said one or more chemically or biologically sensitive materials, more preferably at least about 85%, and most preferably about 96%.

8. A biopolymer fibre or biopolymer film loaded with one or more chemically or biologically sensitive materials which is obtainable by a process as claimed in any one of the preceding claims.

9. Use of a biopolymer fibre or a biopolymer film as claimed in claim 8, as an ingredient in the preparation of a foodstuff, a feed, a nutritional supplement, a home and personal care composition, a pharmaceutical or biomedical composition.