RU2412607C2 - Mixed gel system and preparation method thereof - Google Patents

Abstract

FIELD: chemistry. ^ SUBSTANCE: present invention relates to preparation of a mixed gel system. The method relates to preparation of a mixed gel system containing at least one globular protein, at least one polysaccharide and at least 50 wt % water, and containing at least two separate aqueous phases which are in direct contact, including a protein gel phase and a non-protein aqueous phase. Said method involves preparation of a suspension of protein aggregates of globular protein capable of cold gel formation, aggregates of which have hydrodynamic radius in the range of 10-500 nm. Said suspension also contains one or more polysaccharides, and the mixed gel system is obtained via induced gelling of a suspension of protein aggregates containing one or more polysaccharides by lowering pH of the mixed suspension. The invention also relates to a hydration-restore mixed gel system, suspension of protein particles and free-flowing powder containing protein particles, where each of the listed systems contains a globular protein gel. ^ EFFECT: invention enables to obtain special useful mixed gel systems using a highly reproducible and controlled method. ^ 21 cl, 4 dwg, 9 ex

Description

FIELD OF THE INVENTION

The present invention relates to a method for producing a mixed gel system containing at least one globular protein, at least one polysaccharide and at least 50 wt.% Water, the mixed gel system containing at least two separate aqueous phases that are in direct contact, including a proteinaceous gelled phase and a non-proteinaceous aqueous phase. According to the present invention, the proteinaceous gelled phase is obtained by cold gelation of a globular protein such as whey protein, egg white or soy protein.

The present invention also relates to a rehydratable mixed gel system comprising a protein gelled phase and a non-protein phase, as well as the collection of protein particles containing a covalently crosslinked globular protein.

BACKGROUND OF THE INVENTION

Mixed gel systems containing two separate aqueous phases, including at least one gelled aqueous phase, are described in the prior art.

EP-A 0298561 (Unilever NV) describes edible plastic dispersions containing at least two condensed aqueous phases, at least one of which is continuous, the dispersion comprising an aggregating gelling agent and another gelling agent. Preferred combinations include a gelling agent (a) selected from gelatin, kappa-carrageenan, iota-carrageenan, alginate, agar, gellan, pectin or mixtures thereof, and a gelling agent (b) selected from gelling starch, denatured whey protein, denatured whey protein bovine serum protein, denatured soy protein, microcrystalline cellulose, and mixtures thereof.

EP-A 1466630 (Wisconsin Alumni Research Foundation) discloses a hybrid protein-polysaccharide superabsorbent hydrogel containing an acylated crosslinked protein matrix; and an anionic polysaccharide matrix interpenetrating with an acylated crosslinked protein matrix. This European patent shows the formation of a crosslinked protein matrix by adding carboxyl fragments to lysyl residues in the protein matrix to produce an acylated protein matrix and then crosslinking the acylated protein matrix using a bifunctional crosslinking reagent. Carboxylic moieties are preferably added to the lysyl residues by treating the protein matrix with ethylene diamine tetraacetic acid dianhydride (EDTAD). A preferred crosslinking agent is glutaraldehyde.

An article by Bryant et al. (Food Hydrocolloids 14 (2000) 383-390) reports the results of a study of the effect of xanthan gum on the physical properties of heat-denatured whey protein solutions and gels. Describes how to obtain a series of solutions of heat-denatured whey protein containing various concentrations of xanthan gum by adding varying proportions of a 2 wt.% Solution of xanthan gum and distilled water to 10 wt.% Solutions of heat-denatured whey protein. These solutions are stirred for 10 minutes to dissolve the xanthan gum, and then a salt solution (4M NaCl) is added. The addition of salt causes cold gelation of the denatured whey protein. The final composition of the solutions is as follows: 8.5 wt.% Protein, 0-02 wt.% Xanthan gum and 200 mm NaCl. The authors conclude that the thermodynamic incompatibility of xanthan gum and heat-denatured whey protein leads to phase separation and the formation of a water-in-water emulsion.

SUMMARY OF THE INVENTION

Applicants have found that particularly useful mixed gel systems can be obtained using a combination of a globular protein and one or more polysaccharides and inducing cold gelation of the globular protein using a lower pH. More specifically, the present method includes the following steps:

a. providing a suspension of protein aggregates of a globular protein that is capable of cold gelation, said suspension additionally containing one or more polysaccharides; and

b. obtaining a mixed gel system by inducing gelation of a suspension of protein aggregates by lowering the pH of the mixed suspension.

This method makes it possible to obtain mixed gel systems in a highly reproducible and controlled manner. In the present method, one or more polysaccharides can be dispersed and hydrated without significant influence of globular proteins. When one or more polysaccharides are fully dispersed and hydrated, gel formation of a globular protein can be induced. Thus, it is possible to very effectively control the complex dynamics of gelation / thickening of such a mixed protein / polysaccharide system.

The invention also relates to a hydrated mixed gel system comprising at least two separate aqueous phases, including a proteinaceous gelled phase and a non-protein phase, said mixed gel system comprising:

a. a gelled globular protein selected from the group consisting of whey proteins, egg whites, soy proteins and combinations thereof;

b. polysaccharide selected from the group consisting of galactomannans, carrageenans, agar, pectins, pectin derivatives, cellulose derivatives, dextran, dextran derivatives, gellan gum, xanthan gum, alginate, starch, starch derivatives, inulin, and inulin derivatives, their derivatives inulin, in which the pH of the mixed gel system is in the range of "1 unit higher and 1.5 units lower than the isoelectric point of the globular protein", and in which the mixed gel system has a rehydration rate of at least 2.

In addition, the present invention relates to an aqueous suspension of protein particles containing at least 50% globular protein by weight of solids, with at least 50 wt.% Of said globular protein being covalently crosslinked, said globular protein is selected from the group consisting of whey proteins , egg proteins, soy proteins, and combinations thereof, these particles have a diameter determined by the volumetric mass method in the range of 1-100 μm and are characterized in that particles with a diameter exceeding 1 μm have an average Howat surface of less than 1.2.

The present invention also relates to a free-flowing powder containing dry protein particles, which can be hydrated to produce a suspension of protein particles as previously defined herein.

DETAILED DESCRIPTION OF THE INVENTION

The first aspect of the present invention relates to a method for producing a mixed gel system containing at least one globular protein, at least one polysaccharide and at least 50 wt.% Water and containing at least two separate aqueous phases that are in direct contact, including including a proteinaceous gelled phase and a non-proteinaceous aqueous phase, said method comprising:

b. obtaining a suspension of protein aggregates of a globular protein that is capable of cold gelation, said aggregates having a hydrodynamic radius in the range of 10-500 nm, preferably 15-200 nm, and said suspension further comprises one or more polysaccharides; and

c. obtaining a mixed gel system by inducing gelation of a suspension of protein aggregates containing one or more polysaccharides by lowering the pH of the mixed suspension.

As used herein, the term “protein gelled phase” refers to an aqueous phase that is gelled through the formation of a three-dimensional protein scaffold.

As used herein, the term “non-protein aqueous phase” refers to an aqueous phase that does not contain a protein gel in the form of a three-dimensional protein skeleton. Preferably, said non-proteinaceous aqueous phase contains no more than a limited amount of protein, for example, less than 1 wt.%, More preferably less than 0.5 wt.%, Most preferably less than 0.2 wt.% Protein.

A globular protein aggregate suspension containing one or more polysaccharides can be obtained by appropriately performing the following steps:

i. obtaining an aqueous solution or dispersion containing at least 1% globular protein by weight of water;

ii. if necessary, adjusting the pH of the solution to a value of at least 1 unit above the isoelectric point of the globular protein;

iii. heating and / or increasing the pressure of said aqueous solution, so as to obtain a suspension of aggregates of a globular protein;

where one or more polysaccharides are mixed with an aqueous solution or dispersion and / or a suspension of protein aggregates.

Alternatively, a suspension of a globular protein can be obtained by dispersing a powder or a suspension of pre-prepared aggregates of a globular protein in water. One or more polysaccharides can be added simultaneously, before or after aggregates of a globular protein.

In the case where the present method involves preparing a suspension of globular protein aggregates by heating and / or increasing pressure, such a globular protein must be substantially undenatured before being subjected to heating and / or high pressure to obtain a suspension of protein aggregates. If a denatured globular protein is used in the present method, it is not possible to obtain a suspension of aggregated globular protein that can be crosslinked to form a gel by lowering the pH. Naturally, in the present method, you can use a mixture of native and denatured protein, provided that the amount of native protein is sufficient to make it possible to obtain a proteinaceous gelled phase.

In order to allow the conversion of the solution or dispersion of a substantially undenatured globular protein into a cold gelable suspension of protein aggregates, the aqueous solution or dispersion is heated to a temperature of at least 60 ° C and below 159 ° C. Typically, at least 70 wt.% Of the globular protein present in the aqueous solution or dispersion is aggregated after heat treatment and / or exposure to elevated pressure. Preferably, at least 90 wt.%, More preferably at least 95 wt.% Of the globular protein is aggregated after said treatment.

The mixed gel system of the present invention contains at least two separate aqueous phases that are in direct contact, including a proteinaceous gelled phase and a non-proteinaceous aqueous phase. Thus, a mixed gel system may, for example, consist essentially of a continuous proteinaceous gelled phase and a dispersed non-proteinaceous aqueous phase. The dispersed non-proteinaceous aqueous phase may be thickened or gelled with one or more polysaccharides, or it may actually contain no polysaccharides and globular protein. Alternatively, a mixed gel system may substantially consist of a dispersed protein gelled phase and a continuous non-protein aqueous phase, wherein the non-protein phase may be gelled or gelled with one or more polysaccharides, or it may actually contain no polysaccharides and globular protein. Another embodiment of the present mixed gel system substantially consists of a continuous proteinaceous gelled phase and a continuous non-proteinaceous aqueous phase, which may also be gelled or thickened with one or more polysaccharides, or which may actually contain no polysaccharides and globular protein.

Naturally, the mixed gel systems of the present invention may contain more than two separate phases. Thus, a mixed gel system may contain three or more separate aqueous phases. In addition, the mixed system may also contain a fat phase, wherein said phase is preferably a dispersed fat phase.

As used herein, the term “separate”, for example with respect to a proteinaceous gelled phase and a non-proteinaceous aqueous phase, means that the phases are distinctly separated so that it is possible to show the presence of an apparent interface between these phases. The existence of two separate phases is determined appropriately by means of confocal scanning laser microscopy, while the protein gel phase is tinted with a suitable dye, for example rhodamine B (see Example 9).

The expression “two separate aqueous phases that are in direct contact” is used to make it clear that these two separate aqueous phases are not separated from each other by an intermediate phase, as, for example, in the case of a water-oil-water emulsion.

The present invention provides the advantage that unmodified natural proteins can be used. Thus, in a preferred embodiment, the globular protein is not acylated or crosslinked with a chemical crosslinking agent, for example, a bifunctional crosslinking agent.

The gel-forming globular protein used in the present mixed gel system is preferably selected from the group consisting of whey proteins, egg proteins, soy proteins, and combinations thereof. A more preferred said globular protein is selected from whey proteins, egg proteins, and combinations thereof. The most preferred globular protein is whey protein. The expression “whey protein” encompasses individual whey proteins, for example (β-lactoglobulin and α-lactalbumin. Whey proteins can also be suitably used, for example, in the form of whey powder, whey protein concentrates or whey protein isolates.

One or more polysaccharides used in a mixed gel system are mainly selected from the group consisting of galactomannans, carrageenans, agar, pectins, pectin derivatives, cellulose derivatives, dextran, dextran derivatives, gellan gum, xanthan gum, alginate, starch, derivatives inulin, derivatives of inulin, exopolysaccharides and their combinations. Particularly preferred polysaccharides include galactomannans, carrageenans, gellan gum, xanthan gum, pectins, and combinations thereof. As used herein for polysaccharides, the term “derivatives” refers to polysaccharides that are chemically modified, for example, by esterification, carboxymethylation or hydrolysis.

One or more polysaccharides are usually used at a concentration of from 0.001 to 10 wt.%, Preferably from 0.005 to 8 wt.%, More preferably from 001 to 5 wt.%.

By lowering the pH of a suspension of aggregates containing one or more polysaccharides, crosslinking between the aggregates can be induced. First, mainly physical crosslinking occurs. However, in the next step, in particular in the case of whey protein, chemical covalent crosslinking may also occur. Typically, the pH of a suspension of aggregates containing one or more polysaccharides is lowered by at least 0.5 pH units, preferably at least 1.0 pH units, more preferably at least 1.5 pH units, to initiate crosslinking sufficient to obtain a protein gel. Crosslinking occurs when the pH is lowered to a level close to the isoelectric point of the globular protein. It is preferable to lower the pH to a value of "1 unit higher and 1.5 units lower than the isoelectric point of the globular protein." It is more preferable to lower the pH to a value of "0.8 units higher and 1 unit lower than the isoelectric point of the globular protein."

In a preferred embodiment, the largest amount of globular protein present is crosslinked as a protein gel. Thus, in the protein gelled phase, more than 50 wt.% Of the globular protein is covalently linked. Even more preferably, at least 70 wt.%, Most preferably at least 80 wt.% Of the globular protein are covalently bound in the proteinaceous gel phase.

One or more polysaccharides used in accordance with the present invention can be concentrated in a non-protein aqueous phase or in a protein gel phase, or, alternatively, these polysaccharides can be distributed in these two phases. It is possible to obtain a mixed gel system containing a non-protein aqueous phase that is practically free of polysaccharides using a negatively charged (anionic) polysaccharide in combination with a gelled protein phase at a pH below the protein’s isoelectric point.

If at the pH used to obtain the mixed gel system, there are no negatively charged polysaccharides, the non-protein aqueous phase of the mixed gel system usually contains a significant amount of one or more polysaccharides, for example at least 30 wt.%, More specifically at least 50 wt.% , more specifically at least 70 wt.%.

According to a particularly advantageous embodiment of the invention, the non-proteinaceous aqueous phase is thickened or gelled with one or more polysaccharides.

According to one preferred embodiment of the invention, the mixed gel system obtained after gelation of a globular protein comprises a dispersed proteinaceous gelled phase and a continuous non-proteinaceous aqueous phase. Even more preferably, said continuous non-protein aqueous phase is non-gelatinized.

By removing the continuous non-proteinaceous aqueous phase, it is possible to restore the dispersed protein phase in the form of gelled protein particles. These gelled protein particles can advantageously be used as a substitute for fat, flavoring agent, drug delivery systems, etc. Thus, in a preferred embodiment, the dispersed protein gelled phase is isolated from the mixed gel system, removing the non-proteinaceous aqueous phase and collecting the isolated protein gelled particles. Even more preferably, the dispersed proteinaceous gelled phase is isolated from the mixed gel system by removing the non-proteinaceous aqueous phase by hydrocyclone, filtration, centrifugation, sedimentation and / or washing. Even more preferably, the dispersed proteinaceous gelled phase is isolated from the mixed gel system by removing the non-proteinaceous aqueous phase by washing. The collected particles can be dried accordingly to obtain hydratable powder.

The mixed gel systems of the present invention may contain suitable additional components besides water, a globular protein, and polysaccharides. Examples of additives that can be suitably incorporated into the present mixed gel system include: colorants, flavoring agents, preservatives, vitamins, minerals, pharmaceutically active substances, non-gel forming proteins, sugars, fat, emulsifiers, etc. The above additives can be added at different stages of the present method, for example, during the preparation of an aqueous solution or dispersion containing a globular protein. Alternatively, additives can be added to the suspension of aggregates. In particular, if the additives are sensitive to the heating and / or pressure conditions used to prepare the suspension of protein aggregates, it may be useful to include the additives in the suspension of protein aggregates before gelation is induced.

The present mixed gel system may contain suitably dispersed lipid material, for example, fat. Typically, the present mixed gel system contains 60 to 98 wt.% Water and 0 to 38 wt.% Dispersed lipids, and water and optional lipids together comprise at least 90 wt.% Of the mixed gel system. Examples of dispersed lipids include fat, emulsifiers, flavonoids, sterols, etc.

Another advantageous embodiment of the present invention relates to a method in which a mixed gel system obtained after gelation of a globular protein comprises a continuous protein gelled phase and a non-protein aqueous phase. The non-proteinaceous aqueous phase may be a continuous phase, or it may be a dispersed phase, with the former being preferred. The mutually continuous mixed gel system offers the advantage that the non-protein phase can be relatively easily removed by compression, while the continuous protein phase provides a “sponge structure”. To facilitate removal of the non-proteinaceous aqueous phase, said phase is preferably non-gelatinized.

Applicants have found that these types of mixed gel systems can be dehydrated to provide a product that restores moisture extremely easily. Although the applicants decided not to be limited by theory, they believe that the above mixed gel systems act like sponges, this means that they can be compressed and dried to produce materials that can absorb large amounts of water relative to their own mass. Thus, this dehydrated product can advantageously be used as an absorbent tissue in packaging, as a waterproofing layer, etc. According to this advantageous embodiment, the method comprises the step of dehydrating the mixed gel system while removing at least 50 wt.% Of the water contained therein by pressing, centrifuging and / or drying. Even more preferably, at least 70 wt.%, Most preferably at least 80 wt.% Of the water contained in the mixed gel system is removed. In a preferred embodiment, the water is removed during the first pressing of the mixed gel system, removing at least 20 wt.% Water, followed by drying.

In the case where the present method involves the dehydration of a mixed gel system, said mixed gel system advantageously comprises two continuous phases, one being a proteinaceous gelled phase. This type of mixed gel can be suitably dehydrated to give a product that is very easily and efficiently restored by hydration. In a preferred embodiment, the non-proteinaceous aqueous phase is a thickened phase in which the viscosity is provided by one or more polysaccharides.

In a particularly preferred embodiment of the process comprising dehydration, one or more polysaccharides substantially consists of anionic polysaccharides such as alginates, pectins, carrageenans, gellan gum, xanthan gum and carboxymethyl cellulose. Even more preferably, if at least 60 wt.% Of the polysaccharides, more preferably at least 80 wt.% Of one or more polysaccharides are anionic polysaccharides. Anionic polysaccharides have the advantage that they can bind positively charged proteins, especially at pH values below the isoelectric pH of the globular protein. Thus, mixed gel systems can be obtained that contain anionic polysaccharides that form complexes with a positively charged gelled globular protein. The water content of these mixed gel systems can be reduced by compression without significant loss of the fraction of anionic polysaccharides, even if said polysaccharides are not present as a polysaccharide gel.

Another aspect of the invention relates to a hydrated mixed gel system comprising at least two separate phases, including a protein gel phase and a non-protein phase, said mixed gel system containing 0.01-40 wt.% Water and solids (% by weight indicated) dry matter):

a. 50-99.5 wt.% Gelled globular protein selected from the group comprising whey proteins, egg proteins, soy proteins and combinations thereof;

b. 0.1-50 wt.% Polysaccharide selected from the group consisting of galactomannans, carrageenans, agar, pectins, pectin derivatives, cellulose derivatives, dextran, dextran derivatives, gellan gum, xanthan gum, alginate, starch, starch derivatives, inulin, derivatives inulin, exopolysaccharides and combinations thereof;

where the pH of the mixed gel system is in the range of "1 unit higher and 1.5 units lower than the isoelectric point of the globular protein", and where the mixed gel system has a rehydration rate of at least 2. Even more preferably, the pH of the mixed gel system has a value in the range of "0.8 units higher and 1 unit lower than the isoelectric point of the globular protein."

The hydrated reconstituted gel system preferably has a water content of less than 30 wt.%, More preferably less than 20 wt.% And most preferably less than 15 wt.%. Typically, hydrated mixed gel systems contain at least 0.01% by weight of water.

The non-protein phase in the hydrated mixed gel system is preferably a continuous phase. In another preferred embodiment, the proteinaceous gelled phase is a continuous phase. Most preferably, if both phases, the non-protein phase and the proteinaceous gelled phase, are continuous.

As explained here previously, it is preferable to use anionic polysaccharides, since they make it possible to easily obtain hydrated mixed gel systems without significant loss of polysaccharides during compression. Therefore, the polysaccharide of a hydration-restored gel system is preferably selected from the group consisting of alginates, pectins, kaorragenes, gellan gum, xanthan gum, carboxymethyl cellulose, and combinations thereof.

According to a particularly preferred embodiment, the hydrated mixed gel system has a rehydration rate of at least 2.5, preferably at least 3, most preferably at least 3.5. The rehydration rate is an indicator of the amount of water that a given material can absorb. The rehydration rate is calculated from the mass of the starting material and the mass of wet material obtained in the presence of excess water after a period sufficient to achieve maximum absorption, using the following formula:

rehydration rate = (wet weight - dry weight) / dry weight.

The hydrated reconstituted gel system of the present invention can suitably take the form of a powder, agglomerate or film. A mixed gel system recovered by hydration can also take the form of a molded article, similar to pasta recovered by hydration (pasta, spaghetti, etc.). Most preferably, the hydrated mixed gel system is a free flowing powder.

The amount of globular protein contained in the hydrated mixed gel system is preferably in the range of 70-99% by weight of solids. Typically, at least 50% by weight of the globular protein is crosslinked. Preferably, if the crosslinked protein is at least 70 wt.%, More preferably at least 80 wt.% Of the globular protein contained in the mixed gel system.

As described above, mixed gel systems obtained by the present method and containing a dispersed proteinaceous gelled phase and a continuous non-proteinaceous aqueous phase can advantageously be used to produce gelled protein particles. Thus, an additional aspect of the invention relates to an aqueous suspension of protein particles containing at least 50% globular protein by weight of solids, with at least 50 wt.% Of said globular protein being covalently crosslinked, said globular protein selected from the group consisting of milk proteins whey, egg proteins, soy proteins and combinations thereof, these particles have a diameter determined by the volumetric mass method in the range of 1-100 μm and are characterized in that particles with a diameter exceeding 1 μm, they have an average surface roughness of less than 1.2, preferably less than 1.15.

The surface roughness is an indicator of the surface roughness of the protein particles. The surface roughness is calculated from images obtained using a microscope (confocal scanning laser microscope) using a program for quantitative analysis of images (see example 9). The surface roughness is determined by the following formula:

surface roughness = measured perimeter / perimeter of an ellipse with equal measurements.

The present suspension of protein particles typically contains 1-60 wt.% Of the globular protein, preferably 3-40 wt.% Of the globular protein. The water content of the specified suspension is usually in the range of 99-60 wt.%, Preferably 97-60 wt.%. The continuous aqueous phase of the present invention is preferably non-gelatinized.

As explained here previously, these gelled particles can advantageously be used as a substitute for fat, flavoring agent or drug delivery systems, etc. The present suspension exhibits a texture that can be described as oily or ointment-like. The pleasant texture of the suspension makes it suitable for use as the basis of products, for example, in dressings, mayonnaise, desserts, environments and ointments. Typically, in these applications, the present suspension can be used primarily as the basis of products at a concentration exceeding 70 wt.%, Preferably exceeding 80 wt.%.

Fat substitutes based on an aqueous suspension of protein particles, in particular whey protein particles, are commercially available under the trademark Simplesse®. Simplesse® protein particles differ from real particles in that they are composed of small agglomerated protein particles and are irregular in shape. Typically, Simplesse® agglomerates are composed of small particles with a diameter that is usually significantly less than 1 micron. In contrast, the present particles are spherical granules with a diameter that is usually significantly greater than 1 μm. In addition, the present gelled protein particles exhibit a very smooth surface, as illustrated by the CSLM images available in this document.

Applicants conducted experiments in which a 1 wt.% Aqueous suspension of a commercially available Simplesse® product (Simplesse® 100) was prepared by dispersing the product in reverse osmosis water. The particle size distribution in the suspension was determined using a Mastersizer® 2000 laser diffractometer. The suspension was then sonicated for 2 hours in an ultrasonic bath (Branson ™, Model 2510). Again, the particle size distribution was determined. It was found that as a result of sonication, the volume fraction of particles with a diameter of less than 1 μm increases from about 40 to 90 vol.%, This serves as a demonstration of the destruction of agglomerates during sonication. Carrying out a similar treatment of an aqueous suspension of gelled protein particles of the present invention does not produce a large volume fraction of particles with a diameter of less than 1 μm. Thus, the present invention also includes an aqueous suspension of protein particles containing at least 50% globular protein by weight of solids, wherein at least 50 wt.% Of said globular protein is covalently crosslinked, said globular protein is selected from the group consisting of milk proteins whey, egg proteins, soy proteins and combinations thereof, these particles have a bulk density in the range of 1-100 μm and are characterized in that after 2 hours of sonication at least 60 vol.%, preferably at least 80 vol.%, more preferably at least 90 vol.% of the gelled protein particles have a diameter greater than 1 μm. According to another preferred embodiment, after 2 hours of sonication, at least 60 vol.%, Preferably at least 80 vol.% Of the particles have a diameter greater than 3 microns, most preferably greater than 5 microns.

The aforementioned gelled protein particles can be suitably dried to obtain a free flowing powder with a water content of less than 40 wt.%. Thus, the present invention also relates to a free flowing powder with a water content of less than 40 wt.%, Preferably less than 30 wt.% And most preferably less than 20 wt.%, Which can be hydrated to produce a suspension of protein particles as previously defined here. In order for the free flowing powder to have good technological properties, it is preferable that the protein particles are present in the form of agglomerates. These agglomerates are composed of individual protein particles that are loosely bound together, so that they are easily separated when dispersed in water, especially with stirring. Agglomerates of gelled protein particles can be prepared by suitable agglomeration techniques known in the art. Preferably, if the free flowing powder has an average bulk density of at least 30 μm, more preferably at least 50 μm, and most preferably at least 200 μm. Typically, the free flowing powder has an average volumetric mass particle size of not more than 2000 μm, preferably not more than 1000 μm.

The amount of globular protein contained in the above protein particles in suspension or in a free flowing powder is preferably greater than 60%, more preferably greater than 75%, and most preferably greater than 90% by weight of solids. Typically, at least 50% by weight of the globular protein present in the protein particles is crosslinked. Preferably at least 70 wt.%, More preferably at least 80 wt.% Of the globular protein contained in the mixed gel system are crosslinked. The invention is further illustrated by the following examples.

EXAMPLES

Example 1

Whey protein isolate (WPI; Bipro ™ from Davisco Foots International Inc.; La Sueur, MN, USA) was dissolved in water with continuous stirring (2 hours at room temperature). Soluble WPI aggregates are obtained by incubating a WPI solution in 400 ml portions at an initial concentration of 9 wt.% And 68.5 ° C in a water bath for 2.5 hours. This heat treatment results in protein aggregation of more than 95%. Solutions of WPI aggregates were cooled to room temperature using running tap water (30 min). Solutions of WPI aggregates are diluted to a concentration of 3 wt.%, Adding a solution of locust bean gum. A carob stock resin solution (lbg; C-130 from CP Kelco Inc .; Lille Skensved, Denmark) is pre-prepared by hydrating the powder overnight at 4 ° C, followed by heating to 80 ° C for 30 minutes with continuous stirring. The final composition of the mixed suspension of protein aggregates and polysaccharides contains 3.0 wt.% WPI aggregates and 0.175 wt.% Locust bean gum.

Gelation is induced by the addition of glucono-5-lactone (GDL; Gluconal ™ from Purac Biochem; Gorinchem, The Netherlands). An amount of 0.25 wt.% Was added to achieve a pH of approximately 4.8 after 20 hours of incubation at 25 ° C. All analyzes are performed after incubation of the samples for 20 hours at 25 ° C.

Example 2

The mixed gel system obtained in Example 1 was pressed to 20% of its initial height using an Instron universal research system (model 5543, Instron Corp.) to remove part of the liquid from the gel. The compressed piece of gel (3.7 g) was dried at 60 ° C for 5 hours. The dehydrated piece of gel (03 g) was placed in excess water and allowed to rehydrate for at least 2 hours. The mass of rehydrated material is 1.5 g. Thus, the rehydration rate of a dry piece of gel is 4 ((1.5-03) / 03).

Example 3

Example 1 is repeated, except that the concentration of locust bean resin is set. The final composition of the mixed gel system contains 3.0 wt.% WPI and 0.40 wt.% Resin carob. The mixed gel system is diluted with an equal volume of water and centrifuged for 15 min at 4000g. The resulting precipitate was resuspended in water to give the initial volume and centrifuged a second time. Thus obtained protein precipitate is again suspended in water to the original volume. The size distribution of protein particles is determined using Malvern MasterSizer X (Malvern Instruments, Spring Lane South), and the average particle size is given as the diameter obtained by dividing the volume by the surface:

where n _i is equal to the number of particles with a diameter of d _j and N is equal to the total number of particles.

The average protein particle size (d _3.2 ) obtained from this mixed gel system is 6.8 μm.

Example 4

Example 3 is repeated, except that pectin is added as a polysaccharide in the dilution step, instead of locust bean gum. The final composition of the mixed gel system contains 3.0 wt.% WPI and 0.40 wt.% Pectin (HM Pectin, H-6 from CP Kelco Inc .; Lille Skensved, Denmark). The average protein particle size (d _3.2 ) obtained from this mixed gel system is 12.3 μm.

Example 5

Example 3 is repeated, except that in the dilution step, instead of carob resin, gellan resin is added as polysaccharide. The final composition of the mixed gel system contains 3.0 wt.% WPI and 0.10 wt.% Gellan gum (Kelcogel ™ F from CP Kelco Inc .; Lille Skensved, Denmark). The average particle size (d _3.2 ) obtained from this mixed gel system is 20.3 μm.

Example 6

Ovalbumin (albumin from protein of chicken eggs of category III from Sigma-Aldrich, Zwijndrecht, the Netherlands) is dissolved in water with continuous stirring (2 hours at room temperature). Soluble protein aggregates are obtained by incubating a solution of ovalbumin in 400 ml portions at an initial concentration of 5 wt% and 78 ° C in a water bath for 22 hours. The resulting solutions of ovalbumin aggregates are cooled to room temperature using running tap water (30 min). Solutions of protein aggregates are diluted by adding a solution of pectin. The final composition of the mixed protein aggregates and suspension of polysaccharides contains 2.0 wt.% Ovalbumin and 0.40 wt.% Pectin.

Gelation is induced by the addition of glucono-5-lactone (GDL). An amount of 0.16 wt.% Was added to achieve a pH of approximately 4.8 after 20 hours of incubation at 25 ° C. All studies are carried out after incubation of the samples for 20 hours. at 25 ° C.

The mixed gel system is diluted with an equal volume of water and centrifuged for 15 min at 4000g. The resulting precipitate was resuspended in water, obtaining the initial volume, and centrifuged a second time. This protein precipitate is again suspended in water to its original volume. The size distribution of protein particles is determined according to Example 3. The average size of protein particles (d _3.2 ) obtained from this mixed gel system is 25.3 μm.

Example 7

Example 6 is repeated, except that at the dilution stage, instead of pectin, kappa-carrageenan is added as the polysaccharide. The final composition of the mixed gel system contains 2.0 wt.% Ovalbumin and 0.20 wt.% Kappa-carrageenan (C-40 from CP Kelco Inc .; Lille Skensved, Denmark). The average protein particle size (d _3.2 ) obtained from this mixed gel system is 15.3 μm.

Example 8

Example 6 is repeated, except that at the dilution stage, instead of pectin, gellan gum is added as a polysaccharide. The final composition of the mixed gel system contains 2.0 wt.% Ovalbumin and 0.20 wt.% Gellan gum. The average protein particle size (d _3.2 ) obtained from this mixed gel system is 10.7 μm.

Example 9

The microstructures of the mixed gel systems obtained according to Example 1 are analyzed by confocal scanning laser microscopy (CSLM). The investigated mixed gel systems contain 3.0 wt.% WPI and 0.1 wt.% Gellan (sample A); 3.0 wt.% WPI and 0.2 wt.% Gellan (sample B) and 3.0 wt.% WPI and 0.3 wt.% Locust bean gum (sample C). Mixed gel systems are diluted with an equal volume of water and centrifuged for 15 min at 4000 g. The resulting precipitates are resuspended in water, obtaining the initial volume, and centrifuged a second time. The protein precipitates thus obtained are resuspended in water to the original volume. Aliquots of the final suspension of protein particles are mixed with a solution of rhodamine B (10 μl of a 0.2 wt.% Solution per ml of sample) and left to gel inside a special CSLM cell at 25 ° C.

In addition, a suspension is obtained containing 2.5% by weight of Simplesse® 100 by mixing powdered Simplesse® 100 with reverse osmosis water and mixing for at least 5 minutes using a magnetic stirrer. An aliquot of this sample is mixed with rhodamine B solution as described above (sample D).

CSLM images (160 μm × 160 μm) of the 4 samples mentioned above are recorded in NIZO food research B.V. (Ede, The Netherlands) with a LEICA TCS SP confocal scanning laser microscope (Leica Microsystems CMS GmbH., Manheim, Germany) equipped with an inverted microscope (model Leica DM IRBE) used with an Ar / Kr visible light laser in the detection of individual photons . Use Leica lenses (63x / UV / 1.25NA / waterproof / PL APO). The excitation wavelength is set at 568 nm for rhodamine B with a maximum emission at 625 nm. Files with a digital image are obtained by combining several images in tif format and a resolution of 1024 × 1024 pixels.

CSLM images of samples A, B and C, as well as sample D (Simplesse ®) are shown in FIG. 1 (sample A), FIG. 2 (sample B), FIG. 3 (sample C) and FIG. 4 (sample D )

The protein particles obtained according to the method of this invention have a spherical shape with a smooth surface. In contrast, the commercially available Simplesse® protein particles are irregular in shape with an uneven surface. Roughness of various protein particles is calculated using quantitative image analysis on images of samples A, B, C, and D. For these purposes, the Leica QWin Pro software package (Leica, Microsystems Imaging Systems Ltd., Cambridge, UK) is used. To create a binary image, the routine Detect detection methods are used using this software package. Then apply the routine methods for determining the “Measure Feature” features in order to calculate for each individual object in a binary image the following parameters (using a detection limit of 10 pixels): area (μm ² ), length (μm), width (μm), perimeter (μm) and frame format (-). The length and width are the long and short axes of the object, while the frame format is the ratio between the two axes. The length (L) and width (B) are used to calculate the perimeter of the corresponding ellipse according to the following formula:

P-ellipse = p * square root of (2 ((L / 2) ² + (B / 2) ² ) - ((L / 2) - (B / 2)) ² / 2,458338

Roughnesses of objects in the images are defined as the calculated perimeter divided by the perimeter of the corresponding ellipse. Absolutely smooth spheres have a roughness equal to 1. The average roughness is calculated for an object with a format smaller than or equal to 1.25 in order to avoid artifacts resulting from the contact of objects. The calculated roughness for various protein particles is 1.09, 1.06, 1.09 and 1.35, respectively, for sample A, sample B, sample C and sample D.

Claims (21)

1. A method of obtaining a mixed gel system containing at least one globular protein, at least one polysaccharide and at least 50 wt.% Water, and containing at least two separate aqueous phases that are in direct contact, including a proteinaceous gelled phase and a non-proteinaceous aqueous phase, said method comprising:
but. obtaining a suspension of protein aggregates of a globular protein capable of cold gelation, the aggregates of which have a hydrodynamic radius in the range of 10-500 nm, preferably 15-200 nm, wherein said suspension additionally contains one or more polysaccharides, and
b. obtaining a mixed gel system by inducing gelation of a suspension of protein aggregates containing one or more polysaccharides by lowering the pH of the mixed suspension. 2. The method according to claim 1, according to which a suspension of protein aggregates containing one or more polysaccharides is obtained by performing the following steps:
i. preparing an aqueous solution or dispersion containing at least 1% globular protein by weight of water,
ii. adjusting the pH of the solution to at least 1 unit higher than the isoelectric point of the globular protein,
iii. heating and / or increasing the pressure of said aqueous solution, so as to obtain a suspension of aggregates of a globular protein, and
in which one or more polysaccharides are mixed with an aqueous solution or dispersion and / or a suspension of protein aggregates. 3. The method according to claim 1 or 2, in which the gelling globular protein is selected from the group consisting of whey proteins, egg proteins, soy proteins, and combinations thereof. 4. The method according to claim 1 or 2, in which one or more polysaccharides are selected from the group consisting of galactomannans, carrageenans, agar, pectins, pectin derivatives, cellulose derivatives, dextran, dextran derivatives, gellan gum, xanthan gum, alginate, starch derivatives of starch, inulin, derivatives of inulin, exopolysaccharides and their combinations. 5. The method according to claim 1 or 2, according to which the aqueous solution is heated and / or the pressure is increased to at least 70 wt.% Aggregation of the globular protein. 6. The method according to claim 1 or 2, according to which the pH is lowered by at least 0.5 pH units, preferably at least 1.0 pH units. 7. The method according to claim 1 or 2, according to which the pH is lowered to a value in the range of 1 unit above and 1.5 units below the isoelectric point of the globular protein. 8. The method according to claim 1, according to which the mixed gel system obtained after gelation of a globular protein contains a dispersed protein gelatinized phase and a continuous non-protein aqueous phase. 9. The method of claim 8, wherein the dispersed proteinaceous gelled phase is isolated from the mixed gel system by removing the non-proteinaceous aqueous phase and collecting the isolated proteinaceous gelled particles. 10. The method according to claim 9, whereby the non-proteinaceous aqueous phase is removed by hydrocyclone, filtering, centrifugation, sedimentation and / or washing. 11. The method of claim 10, wherein the non-proteinaceous aqueous phase is removed by washing. 12. The method according to claim 1, whereby the mixed gel system obtained after gelation of a globular protein comprises a continuous proteinaceous gelled phase and a non-proteinaceous aqueous phase. 13. The method according to item 12, according to which the mixed gel system is dehydrated, removing at least 50 wt.% Of the water contained therein by pressing, centrifuging, drying, or combinations thereof. 14. An aqueous suspension of protein particles containing at least 50% globular protein by weight of solids, wherein at least 50 wt.% Of said globular protein is covalently crosslinked, wherein said globular protein is selected from the group consisting of whey proteins, egg proteins, soy proteins and combinations thereof, where particles with a diameter exceeding 1 μm have an average surface roughness of less than 1.2. 15. The aqueous suspension of claim 14, wherein after 2 hours of sonication, at least 60 vol.%, Preferably at least 80 vol.% Of the protein particles have a diameter of more than 1 μm. 16. Free flowing powder with a water content of less than 40 wt.%, Which can be hydrated, obtaining an aqueous suspension according to item 14 or 15. 17. Restored by hydration, a mixed gel system containing at least two separate phases, including a protein gelled phase and a non-protein phase, wherein said mixed gel system contains 0.01-40 wt.% Water and solids (% by weight indicated) solids):
but. 50-99.5% by weight of a gelled globular protein selected from the group consisting of whey proteins, egg proteins, soy proteins and combinations thereof,
b. 0.1-50 wt.% Polysaccharide selected from the group consisting of galactomannans, carrageenans, agar, pectins, pectin derivatives, cellulose derivatives, dextran, dextran derivatives, gellan gum, xanthan gum, alginate, starch, starch derivatives, inulin, derivatives of inulin, exopolysaccharides and their combinations,
where the pH of the mixed gel system has a value in the range of 1 unit above and 1.5 units below the isoelectric point of the globular protein, and where the mixed gel system has a rehydration rate of at least 2. 18. Restored by hydration, the mixed gel system according to 17, containing a continuous non-protein phase. 19. Restored by hydration, the mixed gel system according to claim 17 or 18, comprising a continuous proteinaceous gelled phase. 20. The hydrated hydrated gel system of claim 17 or 18, wherein the polysaccharide is an anionic polysaccharide selected from the group consisting of alginates, pectins, carrageenans, carboxymethyl cellulose, and combinations thereof. 21. The hydrated recovery gel system of claim 19, wherein the polysaccharide is an anionic polysaccharide selected from the group consisting of alginates, pectins, carrageenans, carboxymethyl cellulose, and combinations thereof.

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