NL1028383C2 - Microcapsules. - Google Patents

Description

Title: Microcapsules

The invention relates to capsules, in particular to microcapsules which are suitable for use in foodstuffs, and to processes for the preparation of such capsules. The invention also relates to foodstuffs, in particular dairy products, such as cheese, in which such capsules are incorporated.

Use of (micro) capsules for pharmaceutical purposes, for example, is known per se. Microcapsules are also used in the food industry, for example for administering fragrances or flavors.

Encapsulation generally takes place by emulsifying the material to be encapsulated (in liquid or solid form) or dispersing it in an aqueous solution of the capsule material. By manipulating the solubility for the capsule material, for example by adding certain ions, such as calcium (WO-A-03/018186), or by adding materials that coacerve with the capsule material already dissolved (EP-A-0 856 355) deposits the capsule material on the core. Another method is to add a crosslinker to the core that cross-links dissolved capsule material onto the core and thereby precipitates it. Another possibility for forming a capsule is to evaporate the solvent for the capsule material (US-A-5 601 760). To obtain more control over the capsule size, an oil-in-water-in-oil emulsion (o / w / o emulsion) can also be made, the primary emulsion containing the substance to be encapsulated and the aqueous phase containing the capsule material. After cross-linking the capsule material, the capsule can be separated from the oil (WO-A-04/022 220). Said methods can only be used to encapsulate materials that are poorly or insoluble in water or aqueous solutions.

2

Aqueous solutions can also be encapsulated using a variant of the above method. The aqueous solution is emulsified in an apolar substance (the "oil" phase). In a number of cases, the oil phase contains the dissolved capsule material. A capsule can now be formed by evaporating the oil phase (CA-A-2 126 685), or for example by slowly dissolving water in the oil phase, whereby the oil-soluble capsule material precipitates (US-A-2002/0 160 109). Another possibility is to react / complex a water-soluble and an oil-soluble component in the water-oil interface, such as, for example, in CA-A-1 148 800.

Furthermore, haircuts based on proteins are known from for example US-A-4 147 767, US-A-4 349 530 and GB-A-2 224 258. In all these publications a protein solution (with the substance to be encapsulated added thereto) emulsified in oil (with an emulsifier dissolved or not dissolved therein), the proteins are cross-linked and the particles thus formed are separated from the oil, for example by centrifugation, filtering, washing or a combination of these operations. To effect cross-linking of the proteins, heated (US-A-4 147 767) or a cross-linking agent such as glutaraldehyde (US-A-4 349 530) or a carbodiimide (GB-A-2 224 258) 20 is added. These different ways of forming caps have some disadvantages for use in foodstuffs. For example, heating usually leads to protein denaturation, which usually results in undesirable taste deviations. Glutaraldehyde must not be used in the preparation of food.

The present invention has for its object to provide (micro) capsules which do not exhibit the disadvantages of the capsules from the prior art. It is a further object of the present invention to provide a product which can be added to foodstuffs without problems, for example in order to influence the structure, viscosity and / or texture of the foodstuff in a targeted manner.

3

It has been found that this can be achieved by making capsules from casein, which at least partially forms a network. Therefore, the present invention relates to at least one microcapsule, comprising a capsule, which capsule comprises gelled casein. By "gelled casein" 5 it is meant that the casein is allowed to form physical bonds and / or chemical bonds and thus form a network. Preferably colloidal casein (calcium caseinate) is used, as this is well learned through curdling. There is no mention in the literature of hairstyles that include gelled colloidal casein.

The formation of the casein network in the capsules according to the invention is preferably carried out enzymatically, in particular by means of curdling (i.e. the gelation of casein by the enzyme chymosin). However, the network can also be formed by acidifying the casein solution. A suitable method for forming the capsules according to the invention comprises the following steps: - forming a solution of casein in a suitable solvent, in most cases water. A suitable concentration for the casein is between 0.5 and 15% by weight. This solution is kept at a low temperature, preferably lower than 15 ° C, more preferably 10 ° C or less. Material to be encapsulated can be added to the water, - the gelling agent, preferably rennet, is then added to this solution at a low temperature; The solution thus obtained is emulsified in an apolar phase, in most cases in an oil, for example sunflower oil or olive oil. Preferably, edible oils are used, but non-edible oils may optionally also be used. In principle, however, any liquid in which water can be emulsified can be used. Preferably, an emulsifier, such as 4, is used to form the emulsion

Span ™ 85 or Span ™ 80. The HLB number ("Hydrophile-Lipophile Balance", as defined by W. C. Griffin in J. Soc. Cosmet. Chem., Vol. 1 (1949) 311) of the emulsifier used should preferably be less than 7.

The emulsion is subjected to conditions in which the network-forming reaction takes place, in most cases by heating, for example to a temperature of more than 25 ° C, more preferably to a temperature of 26-35 ° C, for example about 30 ° C; Subsequently, the casein capsules 10 thus formed in the oil phase and filled with water (possibly containing a substance to be encapsulated) can be transferred to an aqueous solution. This can be done by placing the oil containing the casein capsules on an aqueous solution. After a while, the capsules drop from the oil phase to the water phase under the influence of gravity. This process can be accelerated by centrifugation. The process can also be accelerated by choosing conditions under which the action of the emulsifier added to the oil phase diminishes or is canceled out. Examples of this are choosing the right temperature (usually the lowest possible temperature) or adding an emulsifier with a high HLB number (higher than 7), such as, for example, Tween ™ 20, to the water phase 20 on which the oil phase is located.

For some applications, it is not necessary to separate the capsules from the oil. For example, the oil containing the casein capsules can be added directly to oil-continuous systems, such as, for example, butter. Another option is the (mild) emulsification of the oil containing the casein capsules in an aqueous phase. In this way an emulsion of oil droplets in water is formed, the oil droplets being filled with the water trapped in the casein capsules.

Use of casein is very advantageous when using the capsules in cheese, because in this case use is made of a purely cheese-specific material.

5

In addition to the encapsulation application, the capsules can be added to foods to give this structure / viscosity.

The capsules according to the invention contain approximately 95% by weight or more of water, preferably approximately 97% by weight of water and approximately 3% by weight of casein.

The microcapsules according to the invention preferably have an average diameter of between 0.1 and 1000 µm, more preferably between 1 and 500 µm, typically between 10 and 100 µm.

Application of the casein capsules according to the invention in, for example, foodstuffs, in particular in dairy products, such as cheese, can yield a number of advantages, such as for instance a considerable saving of raw materials.

For example, cheese normally contains 40% by weight of water and 30% by weight of casein. By using the capsules according to the invention in cheese, on the plate where the capsule according to the invention ends up, the water / casein ratio is 33 instead of 1.3. In this way it is possible to reduce the protein content of the cheese, with an increase in the moisture content. Furthermore, it is possible to replace part of the amount of casein normally used in cheese with water, because the capsules, because of their structure, have a greater water-binding capacity than casein in conventional form. This allows the moisture content of the cheese to increase.

An important advantage of the capsules according to the invention as an additive to cheese over conventional additives, such as, for example, whey protein or starch-based additives, is that casein is a "cheese-specific" material. When adding the capsules to cheese, therefore, no ingredients are added to cheese that are not normally already present in cheese. This naturally also applies to the addition to other foods, in particular to dairy. This means that adding the capsules does not have to lead to differences in taste.

A further advantage of the capsules according to the invention is that the casein can be cross-linked or gelled by means of coagulation.

6

Coagulation is a natural and safe (food grade) method of processing, as opposed to adding glutaraldehyde-based cross-linking agents, or other cross-linking agents, as is proposed in the prior art, and in contrast to cross-linking of proteins by heating, which can lead to protein denaturation, which can lead to undesirable changes in taste.

Another advantage of the capsules according to the invention is that they can fall apart at a low pH, in particular at a very low pH as it prevails in the stomach. Use can be made of this fact, for example by encapsulating components with a bad taste, while these components can subsequently still be digested well. Many of the capsules from the aforementioned prior art do not have this property.

An interesting discovery was made when an attempt was made to make the capsules without using an oil phase emulsifier. It has been found that in that case aggregates of casein capsules arise in the oil. When the oil is subsequently emulsified in water, these aggregates transfer to the aqueous phase, taking into account the oil enclosed between the aggregated capsules. An oil-in-water emulsion is thus created in which the fat droplets are filled with aggregated casein capsules. These emulsions can be used for low fat applications. This emulsion is also eminently suitable for encapsulating water-soluble components in the casein capsules in the oil droplets. In fact, the emulsion described is a so-called double emulsion. Double water-in-oil * in-water emulsions are known in the literature and are more often used to encapsulate water-soluble components in the inner water phase. However, hitherto known double emulsions always use oil-soluble emulsifiers.

It is known that these can increase the solubility in the oil of non-encapsulated material. As a result, no encapsulated material usually escapes quickly from the inner water phase. The double emulsion described here will not have this disadvantage. In principle, the same double emulsion can be achieved with the aid of hairstyles formed by cross-linked proteins other than casein. The present invention therefore also relates to an oil-in-water emulsion, in which the oil droplets are filled with capsules according to the invention, the oil phase of which is preferably at least substantially free of emulsifier. More preferably, according to this embodiment, the oil phase is completely free of emulsifier.

The invention will now be explained with reference to examples.

Unless otherwise specified, all ratios are weight ratios.

Example 1

A solution of 1-5% casein (casein obtained from milk by microfiltration and spray drying of the retentate) in water with a temperature of 10 ° C was prepared. About 0.5 ml of rennet / liter of water was added to this. The obtained casein solution was then dispersed in a 1: 5 weight ratio in sunflower oil, to which 0.2% Admul WOL ™ emulsifier (HLB value of around 1) was added, using a stirrer (Kinematica Polytron PT3000,

Switzerland). The oil was then heated to 30 ° C and held at this temperature for 20 minutes. A portion of the o / w emulsion thus obtained was then poured onto a 1% aqueous solution of Tween ™ 20 in a tube and then centrifuged for 25 minutes at 5000 g.

The same treatment was carried out with pure water, i.e. water to which no Tween ™ 20 had been added.

In both cases, the centrifugation step resulted in the transfer of an important part of the water droplets surrounded by casein to the aqueous phase. The spheres thus obtained were stained using Rhodamine B. Subsequently, the samples were viewed with a confocal scanning laser microscope (CSLM). The results of the Tween-free sample are shown in Figure 1. The scale of Figs. 1 is the same as that of FIG. 2. Bottom right in Fig. 2 a marking 5 is shown which represents a length of 80 µm.

FIG. 1 it follows that the average diameter of the capsules was approximately 30 µm.

Example 2 Example 1 was repeated, but now Span ™ 85 was used as an emulsifier. Span ™ 85 is an oil-soluble emulsifier that is reasonably hydrophilic (the hydrophilic / lipophilic balance, HLB is 1.8). Because of the higher HLB, the capsules could be brought from the oil to the water phase even more easily than in Example 1 by placing the capsule-containing oil on water. Under the influence of gravity, the capsules moved largely from the oil to the water phase within an hour. A CSLM recording of the capsules thus obtained is shown in FIG. 2.

Example 3 Example 1 was repeated, but no emulsifier was added to the oil phase. After the heating step, the capsules were formed in the oil. The capsules now appeared to have formed aggregates in the oil. The (aggregates of) capsules were now not separated from the oil, but the oil was emulsified (in a weight ratio of 1 to 10) using an aqueous stirrer with 0.5% casein added thereto. A CSLM recording of the oil droplets thus formed in water is shown in FIG.

3. In this figure the oil phase turns green, the protein phase turns red and the water phase turns black. FIG. 3 it appears that oil droplets have been formed which are again filled with (aggregated) casein capsules.

j * A V «. «

Claims (15)

A microcapsule comprising a capsule, said capsule comprising gelled casein. A microcapsule according to claim 1, wherein the casein is gelled with the help of enzymes, preferably with the help of rennet. A microcapsule according to any one of the preceding claims, which is filled with a polar, preferably aqueous, liquid; or is filled with a gas, preferably air. 4. A microcapsule according to any one of the preceding claim, which is filled with a solution, a suspension or a dispersion of one or more components in a polar liquid. A microcapsule according to any one of the preceding claims, with a diameter of between 0.1 and 1000 μπι. 6. A microcapsule according to any one of the preceding claims, with a moisture content of 50% by weight or more, preferably 80% or more, in particular 97% or more. An oily phase containing capsules according to any one of the preceding claims. An aqueous phase containing capsules according to any one of the preceding claims 1-6. An oil-in-water emulsion in which the oil droplets are filled with capsules according to any one of the preceding claims 1-6. The emulsion according to claim 9, wherein the oil phase is at least substantially free of emulsifier. 11. An emulsion according to claim 10, wherein the caps comprise cross-linked proteins other than casein. A foodstuff, preferably dairy product, comprising microcapsules according to any of claims 1-6. A cheese according to claim 12. 14. A method for the preparation of microcapsules, comprising the steps of: emulsifying a casein solution at a temperature of <25 ° C with an enzymatic gelling agent, preferably rennet, added thereto, in an oil with an emulsifier added thereto; heating the emulsion thus obtained to a temperature at which the gelling agent becomes active; - keeping the emulsion at this temperature for a period of time sufficient to form a capsule; and - optionally separating the capsules from the oil phase. Microcapsules available according to the method of claim 14.