The preparation of protein stabilised emulsions at neutral pH is well documented but less is known of the properties of emulsions prepared at pH values at which the stabilising protein is in the cationic form i. e. with a net positive charge.

In the present application, references to APSET (acid- stable protein stabilised emulsion technology) refers to the process of emulsifying an edible plant in a solution of an edible protein or mixture of proteins, or a mixture of proteins, phospholipids and phosphoproteins, either in a converted cationic form (i. e. , with a net positive charge), as described in our earlier Application No PCT/GB01/01482. References to macroemulsions refer to

emulsions with a lipid core large enough to carry a useful concentration of bacteria, as opposed to more usual emulsion types where the particle diameter is less than 0.8 micron.

Emulsions prepared by the APSET route have unique and valuable properties in a wide range of applications. For example, they are inherently stable in simulated gastric fluid but destabilised in ileal fluid and the lipid core is accessible to enzyme degradation-with consequential release of biologically-active from the lipid core after coming into contact with bile secretions. These properties offer a potentially valuable method of protecting biologically active material during passage through the hostile, acid environment of the stomach.

Probiotic bacteria are a class of biologically active material that are of great interest. Such bacteria- usually lactic acid bacteria-are known to induce beneficial effects on the microflora of the lower gut by excluding pathogens. For example, bacteria such as Lactobacilli, Bifidobacteria and Acidophilus spp. are know to promote a healthy gut environment.

However, if probiotic bacteria are delivered to the gut by the oral route, survival is predicated by consumption of food at the same time sufficient to partially neutralise the stomach acid, which can otherwise destroy or damage the bacteria before the therapeutic benefits are obtained. Even then survival of the bacteria is limited and very high innocula are required to provide a dose sufficient to colonise the lower gut.

In principle, the target bacteria might be protected if they were incorporated as inclusions in emulsions of the APSET type.

However, bacteria are comparatively large in comparison to standard emulsions, and accordingly APSET methods are not effective. In addition creaming of such macro emulsions is rapid. This renders the emulsions of limited practical value.

For example, it is desirable to produce an emulsion with a lipid core of 5-25 micron diameter to ensure that a useful concentration of bacteria (of the order of 1-2 micron diameter) can be included in the protective core.

However at this size, emulsions cream particularly rapidly.

It is therefore an object of the present invention to provide a macroemulsion of a sufficient size to allow large inserts such as bacteria to be included.

It is a further object of the present invention to provide a macroemulsion with an improved stability, which is stable in acidic conditions and over time and which does not undergo creaming.

It is a further object of the present invention to provide a macroemulsion which can be used as a delivery system for probiotic bacteria or pharmaceutical agents.

According to a first aspect of the present invention, there is provide a method of producing protein stabilised macroemulsions, the method comprising the steps of

decreasing the pH of gelatin, to convert it to a cationic form, heating the gelatin until it is solubilised and then adding a lipid.

Preferably the gelatin is of fish origin.

The gelatin may alternatively be of animal origin.

The macroemulsions may be stabilised by a mixture of gelatins of different origins.

Preferably the fat to protein ratio of the final emulsions is greater than 10: 1.

Preferably in the step where the pH value is decreased, the pH value is decreased to between 1.5 and 3.5.

Preferably in the step where the protein solution is heating, the protein solution is heated to approximately 65°C.

Optionally, the lipid is of animal origin.

Alternatively, the lipid is of vegetable origin.

Alternatively, the lipid is of fish origin.

Preferably a pre-emulsion is made from the protein solution of a lipid for high speed mixing.

Preferably the pre-emulsion is treated with a high efficiency dispersion technique to prevent creaming.

Optionally, the high efficiency dispersion technique is a homogeniser.

Optionally, homogenisation is carried out at a low pressure.

Preferably, the pH of the solution is lowered by the addition of an acidic solution.

Optionally, the acidic solution is hydrochloric acid.

Alternatively, the acid solution is citric acid.

Preferably the pH for the final solution is increased by the addition of an alkaline solution.

A sugar may be added.

According to a second aspect of the present invention, there is provided oil in water macroemulsions which are stable at low pH and in ethanol, wherein the macroemulsions are comprised of a lipid stabilised by gelatin.

Preferably the macroemulsions have a lipid core in the order of 5-25 micron diameter.

Preferably the macroemulsions are suitable for carrying particles in the order of 1-2 micron diameter.

Preferably the gelatin is in cationic form.

The macroemulsions may contain probiotic bacteria.

Where the macroemulsions carry probiotic bacteria, the bacteria may be Lactobacilli spp.

Where the macroemulsions carry probiotic bacteria, the bacteria may be Bifidobacteria spp.

Where the macroemulsions carry probiotic bacteria, the bacteria may be Acidophilius spp.

The macroemulsions may contain a pharmaceutical agent.

The macroemulsions may contain neutraceuticals.

The macroemulsions may contain food additives.

The macroemulsions may contain prophylactic therapeutic agents.

The macroemulsions may contain a protein or peptide.

According to a third aspect of the present invention, there is provided water in oil and water macroemulsions which are stable at low pH and in ethanol, wherein the macroemulsions are comprised of a lipid stabilised by gelatin, wherein the lipid also comprises one or more aqueous inclusions stabilised at the water oil interface by a protein, and wherein the aqueous inclusions contain inserted material.

The inserted material may include probiotic bacteria.

Where the inserted material is bacteria preferably the lipid contains nutrients which promote bacterial growth.

The bacteria may be Lactobacilli, Bifidobacteria or Acidophilius spp.

The inserted material may include a pharmaceutical agent.

The inserted material may include neutraceuticals.

The inserted material may include food additives.

The inserted material may include prophylactic therapeutic agents.

The inserted material may include a protein or peptide.

According to a fourth aspect of the present invention, there is provided oil in water macroemulsions which are stable at low pH and in ethanol, wherein the macroemulsions are comprised of a lipid stabilised by a protein wherein a low molecular weight amphiphile is included in the lipid and aqueous phase.

The low molecular weight amphiphile may be soya bean lecithin.

According to a fifth aspect of the present invention, there is provided water in oil and water macroemulsions which are stable at low pH and in ethanol, wherein the macroemulsions are comprised of a lipid stabilised by a protein, wherein the lipid also comprises one or more aqueous inclusions stabilised at the water oil interface by a protein, wherein the macroemulsions contain a low

molecular weight amphiphile in both the lipid and aqueous phase.

The low molecular weight amphiphile may be soya bean lecithin.

Preferably the aqueous inclusions contain inserted material. The inserted material may be bacteria, a pharmaceutical agent, neutraceuticals, food additives, prophylactic therapeutic agents, or a protein or peptide.

According to a sixth aspect of the present invention there is provided a food or beverage comprising gelatin stabilised macroemulsions according to the second and third aspects.

According to a seventh aspect of the present invention there is provided a food or beverage comprising protein stabilised macroemulsions according to the fourth and fifth aspects.

According to an eighth aspect of the present invention there is provided a therapeutic agent comprising the gelatin stabilised macroemulsions according to the second and third aspects.

According to a ninth aspect of the present invention there is provided a therapeutic agent comprising protein stabilised macroemulsions according to the fouth and fifth aspects.

In the present invention, macroemulsions are produced which are inherently stable, are not subject to rapid

creaming and are large enough to carry probiotic bacteria. Whilst APSET technology has been shown to produce stable emulsions, the technology is ineffective in transporting bacteria which can be uni-cellular or multi-cellular organisms and which are generally large in size.

It is desirable to produce an emulsion with a lipid core of 5-25 micron diameter to ensure that a useful concentration of bacteria (of the order of 1-2 micron diameter) can be included in the protective core. Such emulsions may be described as Macroemulsions to differentiate them from the more usual emulsion type where the particle diameter is less than 0.8 micron and the natural dispersive forces (commonly referred to as Brownian motion) inhibit creaming.

A major impediment to manufacture of such emulsions is that creaming i. e. natural separation of the emulsion globules is rapid. Creaming can be inhibited by reduction in the particle size, by reduction of the density difference between the emulsion droplet and the suspending medium or by increasing the viscosity of the suspending medium. However, reduction of particle size is counter-productive in the present case because it reduces the potential of the droplet to include bacteria.

In addition, reduction of the density difference between the emulsion droplet and the suspension medium is difficult to achieve.

Increasing the viscosity of the suspending medium is more practical and several solutions have been successfully

applied to emulsions at neutral pH. For example, cocoa solids or microparticulate particles of calcium carbonate may be suspended in milk-based media by addition of polysaccharide. Carageenan, guar gum and modified starches have all found application. Nevertheless, when these principles were tested with acidic macroemulsions the resulting products were not stable.

It was postulated that a protein stabiliser that formed gels and that could be used as the emulsifier for fat droplets might provide the ideal product. In the present invention the type of protein derived from collagen and commonly referred to as gelatine or gelatine has been identified as an ideal material for stabilisation of Macroemulsions.

The macroemulsions of the present invention are suitable for protecting bioactive particles of the order of 1-2 micron diameter. In the present invention it has been discovered that gelatin, where converted in a cationic form allows stable macroemulsions to be produced. In particular, advantage in the use of gelatin lies in the fact that its inherent viscosity inhibits creaming.

To optimise the properties of these emulsions a higher ratio of protein to fat than is usual in APSET applications is used and it is important to limit the severity of homogenisation. Typically the ration of protein to fact will be greater than 1: 10. A ratio of 1: 2 may be optimal but it will be appreciated that the method of the present invention is not limited to this.

Contrary to expectation severe homogenisation results in emulsions with a mixture of very large and small globules. Therefore it is important in the method of the present invention to limit the severity of homogenisation. This may be done using a low pressure homogenisation technique, or carrying out less passes through a homogeniser as normal.

The use of a less severe homogenisation technique, together with an appropriate protein to fat ratio yields Macroemulsions that are stable at ambient temperature for several weeks. Importantly the macroemulsions are stable at acidic pH and can therefore be used as a pharmaceutical product to administer probiotic bacteria.

The gelatin stabilised macroemulsions will also have uses in administering proteins, peptides or drug molecules which are large in size.

In addition to gelatin, APSET-type macroemulsions may be prepared from other food protein provided a low molecular weight amphiphile is included in both the lipid phase and in the aqueous phase containing protein.

For example, soya bean lecithin (different fractions) may be used to provide either the lipid soluble component or the water-soluble component. Addition of this amphiphile reduces the energy required to produce the emulsion, but does not influence its stability in acidic conditions.

The typical emulsions prepared by this route are stable for extended periods at room temperature.

Example Method 1 A Hollandaise sauce stable to freezing and thawing has hitherto never been reported. However, by utilising the special features of APSET, a range of products with superior organoleptic properties can be made.

Water is heated (57% of weight of final mixture) to 40°C, then glucose syrup (10%) and lemon juice (2. 5%) are added, maintaining the temperature at 40°C. Egg protein (1%) is mixed into the solution and the pH of the mixture adjusted to 3.7 using citric acid. At this stage the mixture is heated to 55°C and molten butteroil (30%) added.

A coarse emulsion is produced (typically using a Silverson mixer for 5 minutes at 55°C). The mixture is then homogenised and starch (2%) is added, together with seasoning (salt and pepper to taste). This mixture is treated with a mixer (a Silverson is appropriate) for about 5 minutes. Finally, the product is pasteurised at 85°C for 10 minutes with stirring, and cooled rapidly with stirring, until the temperature is below 8°C.

This sauce may be used fresh (after heating) or may be frozen successfully and stored in a domestic freezer for extended periods with deterioration.

The advantage of the present invention lies in the fact that a new platform is opened from which to develop new products and processes. For example the macroemulsions described in the present invention can be used for the transport of living probiotic bacteria (which have application as food additives, nutraceuticals and

prophylactic therapeutic agents). Another potential application might be the transport of other bio-active entities such as drugs. In this case the invention would allow particles of a lipid-insoluble material to be suspended in the lipid phase which is then protected by the technology described here.

Further modifications and improvements may be added without departing from the scope of the invention herein described.