WO2011077073A1

WO2011077073A1 - Double emulsions

Info

Publication number: WO2011077073A1
Application number: PCT/GB2010/002276
Authority: WO
Inventors: Fotis Spyropoulis; Ian Timothy Norton; Sarah Frasch-Melnik
Original assignee: The University Of Birmingham
Priority date: 2009-12-24
Filing date: 2010-12-15
Publication date: 2011-06-30
Also published as: GB0922626D0

Abstract

The invention relates to comestible products comprising a substantially stable water-in-oil-in water double emulsion, the double emulsion comprising monoglycerides, triglycerides, water, oil and a further emulsifier. Typically the double emulsion does not contain polyglycerol polyricinoleate (PGPR). Methods of making such double emulsions are also provided.

Description

Double Emulsions

The invention relates to food-grade double emulsions for use in comestible products. In particular, the invention relates to comestible products comprising substantially stable water- in-oil-in-water double emulsions and to methods for producing such double emulsions.

Unhealthy processed foods contribute to the growing problem of obesity: oil-in-water food emulsions, such as salad dressings or mayonnaise are high in fat, but are nevertheless very popular with consumers. Current low fat alternatives rely on replacing some of the oil with water-soluble ingredients, such as modified starches, that increase the viscosity of the emulsion continuous phase. However, the incorporation of these into food emulsions can coat oil droplets with a starchy layer, which results in a "slimy" mouth-feel of the emulsion and thus, in the eye of the consumer, an inferior product.

One solution to this problem is to replace some of the oil with water, while keeping the overall volume of the oil phase the same. This eliminates the requirement for altering the aqueous phase composition of the low-fat alternative in order to replace the missing oil volume. A so-called water-in-oil-in-water, or double, emulsion would retain the properties of the original emulsion (e.g. mouthfeel, flavour) while effectively reducing the amount of fat ingested by the consumer.

Furthermore, by increasing the effective oil volume in the product, the concentrations of solutes, such as salt or sugar, in the external water phase can be increased without increasing their concentration in the overall product or the concentration of fat. This has been shown to enhance the perception of these solutes by the consumer in a paper by Malone et al (Oral Behaviour of Food Hydrocolloids and Emulsions. Part 2. Taste and Aroma Release. Food Hydrocolloids, 17(6), 775-784). Bioactives, which are beneficial to the consumer's health but may not have an agreeable flavour, could also be carried in an encapsulated aqueous phase to be released in the stomach whiles not being detected by the consumer.

Double emulsions, including food grade emulsions are known from papers such as Garti et al (Double emulsions of water-in-oil-in-water stabilized by alpha-form fat microcrystals. Part 1 : Selection of emulsifiers and fat microcrystalline particles. Journal of the American Oil Chemists Society, 76 (3), 383-389). However, it is difficult to make double emulsions stable over extended periods of time due to their inherent thermodynamic instability. The existence of two oppositely-curved interfaces in close proximity requires two different emulsifiers (one lipophilic, one hydrophilic) to stabilise a double emulsion. The two emulsifier species have a tendency to diffuse to the respective other interface, which subsequently destabilises the structure. This is especially so when small-molecule surfactants are used. All stable food grade emulsions that have so far been reported have used PGPR (polyglycerol polyricinoleates) to stabilise the primary w/o emulsion. PGPR has the ability to make very viscous and elastic interfaces, and is thus able to resist forces, such as osmotic pressure gradients, that usually contribute to double emulsion destabilisation. It is effective at making extremely stable food-grade w/o emulsions. However, PGPR is a tightly regulated food additive that does not have GRAS status and is disliked by the consumer. It is therefore highly desirable to replace it with more widely accepted emulsifiers.

The present invention takes a primary emulsion well-known for its stability - a margarine- style emulsion, stabilised by fat crystals at the interface - and incorporates this into a stable double emulsion. Crystalline mono- and triglycerides replace PGPR as emulsifiers for the primary emulsion. The fat crystals provide stabilisation to the primary emulsion by forming "shells" around individual water droplets, thus providing very good protection against coalescence (Pickering Stabilisation).

The primary emulsion aqueous phase could contain sugar, salt, or any other water-soluble ingredient, e.g. flavouring or micronutrients.

These margarine-style emulsions have been around for many years, and have therefore been studied in great detail, but have never been incorporated into a double emulsion. The inventors have shown that the fat crystal stabilised emulsions had a potential to remain stable even when incorporated into a double emulsion, as the "shells" surrounding the water droplets inhibit any transport of water between the two aqueous phases.

A major problem, however, is the "stickiness" of these margarine-style emulsions, which prevents easy dispersion of the primary emulsion into a double emulsion. Furthermore, it has been shown by Boode, K and Walstra, P (Partial Coalescence in Oil-in-Water Emulsions 1. Nature of the Aggregation. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 81, 121-137) that fat crystals in a dispersed oil phase are detrimental to o/w emulsion stability. These issues have been overcome in the present invention by using relatively low amounts of total crystallising material in the emulsion, and, at the same time, diluting the resulting primary emulsion with oil to further decrease the strength of crystal networks in the primary emulsion.

Secondary emulsifiers, i.e. the mostly hydrophilic substances that stabilise the double emulsion globules, are polymeric or particulate in nature - e.g. sodium caseinate or silica particles. Polymeric emulsifiers such as sodium caseinate create a thick film around double emulsion globules (steric stabilisation) which provides very good protection against coalescence. Furthermore, the large molecular size of any polymer greatly reduces the commonly experienced problem of emulsifiers diffusing across interfaces and destabilising these. The thick film surrounding the double emulsion globules is also important for preventing fat crystals that may be protruding from one emulsion globule from causing coalescence with neighbouring globules. Silica particles, on the other hand, are known to closely pack and irreversibly adsorb on oil/water interfaces, so providing superior stability to emulsions, through a mechanism known as Pickering stabilisation.

The resulting double emulsion, which does not contain any PGPR in line with present regulatory and consumer demand, is typically stable for at least 4 weeks, stable emulsions of 12 weeks have been observed.

The first aspect of the invention provides a method of making a water-in-oil-in-water double emulsion for a comestible product, comprising the steps of:

(a) making a primary emulsion, the primary emulsion comprising approximately 10-70% weight/weight of a first aqueous phase comprising water and approximately 90 to 30% weight/weight of a first oil phase, the oil phase comprising an oil, the oil comprising a mixture of mono- and tri- glycerides ( G and TG) and;

(b) mixing the primary emulsion with a second aqueous phase, further emulsifier and optionally a second oil phase to form the double emulsion. The further emulsifier may be premixed with the second aqueous phase. Water-in-oil-in-water double emulsion are also known as W/O/W or Wi/0/W₂, double emulsions.

Typically, PGPR is not used in the method.

Comestible products are products which are suitable to be eaten. Typically the comestible product is a low fat dressing, for example a salad dressing or a mayonnaise.

The first and/or second phase may comprise a vegetable oil. Typically the vegetable oils are liquid at approximately 30°C. They typically contain polyunsaturated fatty acids. Examples of suitable oils include soy bean oil, canola and sunflower oils. Such oils are readily commercially available.

Glycerides are esters formed from glycerol and fatty acids. Glycerol has three hydroxyl functional groups which can be esterified with one, two or three fatty acids to form monoglycerides, diglycerides and triglycerides.

The inventors have found that a mixture of MG and TG gives rise to stable emulsions. Monoglycerides have several functions: as it is located at the interphase between the different phases even in liquid form, it crystallises here as the temperature is reduced below its melting temperature. The crystals act as seeds for small triglyceride crystals to rapidly form around the water droplets. This improves the speed at which triglycerides crystallise at the interface, resulting in more stable primary emulsions. Primary emulsions made only with monoglycerides and without triglycerides on the other hand, show reduced stability over those where both species are present.

The monoglycerides may be any commercially available monoglycerides. For example, the monoglyceride may be based on palm oil, such as that available from Danisco A/S, Copenhagen, Denmark.

Typically the triglycerides used are crystallising at, for example, 5-40°C. Preferably tripalmitin in used. Alternatively, other triglycerides, such as those with saturated fatty acids may be used. An example of such an alternative is tfistearate. A mixture of different triglycerides may be used. For example, tristearate may be mixed with tripalmitin. As different triglycerides have different melting points, the stability of the double emulsion can be tailored to the desired application, by choosing triglycerides with a combination of fatty acids that have the desired melting point. This allows the melt-in-the-mouth melting point to be tailored for sudden flavour release or allow the product to be stable at in-mouth temperatures, in order to hide-off flavours that some micronutrients bring to food.

The oil used in the primary emulsion may be different to the oil optionally used as the second phase. Alternatively, the oil may be the same.

A mixture of oils may be used in the primary emulsion and/or as the second oil phase.

The primary emulsion may comprise 30% aqueous phase to 70% oil phase or 60% water phase to 40% oil phase.

The double emulsion may comprise approximately 10-50% weight/weight primary emulsion; approximately 90-50% second aqueous phase; and approximately 0-20% second oil phase. The double emulsion may comprise 20-70% weight/weight primary emulsion and 80-30% second aqueous phase, 40-60% weight/weight primary emulsion and 60-40% weight/weight second aqueous phase or approximately 50% weight/weight primary emulsion and 50% weight/weight second aqueous phase. The double emulsion may comprise 0, up to 10% or up to 20% second oil phase.

The primary emulsion may be made in a margarine line consisting of a scraped surface heat exchanger and a pin stirrer. The emulsion may be cooled during shearing to assist the development of small crystals at the oil/water interface. The cooling may be to approximately 5°C.

The second emulsion may be prepared by mixing together using a high shear mixer or by membrane emulsification. Both techniques are generally known in the art. Membrane emulsification is particularly advantageous.

With high shearing processes a short shearing time and relatively low shear is typically used in order to minimise damage inflicted on the primary emulsion droplets. With membrane emulsification, a minimum pore size of around 3-4 times the primary emulsion droplets size (for example approximately 15 πι) is used in order to make it possible for the primary emulsion to pass through the membranes. Furthermore, a volume-controlled feed system for the dispersed phase, may be used with a low volumetric flow-rate (for example 0.1-0.5 ml/min) in order to enable relatively small globules to be produced. Corresponding to the relatively large pore size, it is preferred that a high cross-flow speed (that is high shear) is applied to enable small globule sizes (typical cross-flow pressure is for example 30-50kPa) in the system exemplified. Alternatively, for rotating membrane is used a high rotational speed (such as 2000 rpm) combined with a relatively narrow vessel (such as approximately 2 times the diameter of the membrane shaft) is employed to create high shear.

The further emulsifier incorporated with the second aqueous phase (the aqueous phase surfactant) may be incorporated, for example, between 0.5 and 5% weight/weight of the second aqueous phase, 1-7% or 2-5% weight/weight of the second aqueous phase. The further emulsifier may be, for example, a polymeric surfactant or a surfactant comprising nanoparticles. The emulsifier may be sodium caseinate. Sodium caseinate is typically used at concentrations of 1-5% weight/weight of the second aqueous phase. Alternative polymeric emulsifiers include gelatin, BSA (bovine serum albumin), whey protein isolate (WPI), modified starch and lecithin. Any food grade particles with sizes in the nanometer range may be used. Such nanoparticles may for example be silica or fat crystals or hydrocolloid particles. The concentration of such nanoparticles depends on the primary emulsion concentration. For example, 1% is sufficient for a 20% primary emulsion in continuous aqueous phase. Higher concentrations may be required for more concentrated double emulsions in order to obtain good surface coverage with the particles.

The aqueous phase may be acidified to less than pH 4.0, less than pH 3.0, typically pH 2.0. Typically hydrochloric acid is used, however any food grade acid may be used.

In general, it is desirable that sufficient further emulsifier is used to cover oil/water interfaces, yet little enough so that no large excess further emulsifier exists in the system.

Any of the water, oil or water phases may comprise one or more solutes selected from salts, sugars and micronutrients, such as vitamins. Fat soluble vitamins may be incorporated, for example, into the oil phase. Salts such as sodium chloride or potassium chloride or sugars such as glucose or fructose may be incorporated into one or both of the first or second aqueous phase. Typically the second aqueous phase comprises one or more osmotic solutes to match the osmotic potential of solutes in the primary aqueous phase of the primary emulsion. Such solutes may be salts, sugars or micronutrients as discussed above. The inventors have found that substantially matching the osmotic pressure can be used to improve the stability of the emulsion, by improving the microstructure of the emulsions.

Typical concentrations of the solutes in the or each aqueous phase are 5-10% for sugars or 1- 6% for salts (weight/weight of the aqueous phase).

The first aqueous phase and/or second aqueous phase may comprise one or more solutes selected from salts, sugars and micronutrients.

A further aspect of the invention provides a comestible product comprising a substantially stable water-in-oil-in-water double emulsion. The double emulsion comprising monoglycerides, triglycerides, water, oil and at least one further emulsifier. Individual components are preferably as described above. By substantially stable it is meant that there is stability against any substantial release from the primary aqueous phase to the continuous secondary phase, as all surfactants used in the primary emulsion are anchored at the surface, and those in the aqueous continuous phase are either polymeric or particulate in nature. This prevents migration of surfactants between the two phases, which in mm is a commonly experienced problem for the destabilisation of double emulsions. Emulsions with stabilities of at least 6, 8 and 12 weeks have been produced.

The double emulsion may comprise one or more preservatives, such as potassium sorbate, to inhibit microbiological growth.

The double emulsion produced by the first method of the invention or used in the comestible product of the second aspect of the invention, preferably does not comprise PGPR.

Preferably the double emulsion in the comestible product is obtainable by the method of the first aspect of the invention. Typically, the double emulsion comprises 97-55% weight/weight of aqueous phase and 3- 45% weight/weight oil phase.

The comestible product is typically salad dressing or mayonnaise.

The invention will now be described by way of example only with reference to the following figures:

Figure 1: Double emulsion, containing primary emulsion and equal parts of sunflower oil, osmotic pressure matched with glucose, after production (a) and after 6 weeks (b): Droplets have coalesced because of their close proximity in the creamed layer, but retained the double emulsion structure.

Figure 2: SEM micrographs of a double emulsion where the osmotic pressure is matched with NaCl, after production (a) and after 1 week (b). Little change in droplet size and globule size is observed.

Figure 3: SEM micrograph showing a primary emulsion droplet stabilised by fat crystals (A) and surrounded by a continuous network of fat crystals (B). The primary emulsions have been shown to be extremely stable for more than 3 months.

Figure 4: Conductivity measurement tracing the release of ions from the primary aqueous phase in double emulsion stabilised by Na-caseinate. The continuous aqueous phase contains various concentrations of a sugar (glucose or fructose). Release is very slow (after 4 weeks, -20% of total ions are released). The strength of the osmotic pressure gradient does not seem to significantly influence release rates.

Figure 5: Examples of double emulsions after productions stabilised by Si-particles only: (a) after production and (b) after 1 week; and Si-particles and 1% Na-caseinate: (c) after production and (d) after 1 week Figure 6: Double emulsion, containing primary emulsion and equal parts of sunflower oil, osmotic pressure matched with glucose, at pH2, after production (a) and after 4 weeks (b): The acid causes network formation of double emulsion globules, the network subsequently prevents aggregation of globules.

Compositions:

The following nomenclature is observed: WyO/W], where W₂ is the primary emulsion aqueous phase and Wi is the continuous aqueous phase

- Example 1

W2/O Primary emulsion

W₂: Aqueous phase (30%wt/wt of total primary emulsion): KG (1.7% wt/wt in aq phase), distilled water

O: Oil Phase (70% wt/wt of total primary emulsion): 1.25% monoglyceride and 2.5% triglyceride (% wt/wt in the oil phase); Sunflower oil (commercially available)

W2/O/W1 Double emulsion

W₂/0 Primary emulsion (10% wt/wt of total double emulsion)

Sunflower oil (10% wt/wt of total double emulsion)

Wi: Aqueous phase (80% wt/wt of total double emulsion): Na-caseinate (1% wt wt in aqueous phase), distilled water, and either (wt/wt of aqueous phase):

- Example la: Wi also contains 10.3% glucose

- Example lb: Wi also contains 8% glucose

- Example lc: Wi also contains 5% glucose

- Example Id: Wi also contains 20% glucose

- Example le: Wi also contains 10.3%) fructose

- Example If: Wi also contains 2.6% NaCl

- Example lg: Wi also contains 1.3% NaCl

- Example lh: Wi also contains 5.2% NaCl

- Example 2

W2/O Primary emulsion

2: Aqueous phase (30%w/wt): KC1 (1.7% w/iwt in aq phase), distilled water 0: Oil Phase (70% w/wt): 1.25% monoglyceride and 2.5% triglyceride (%w/w in the oil phase); Sunflower oil (commercially available)

W2/O/W i Double emulsion

W₂/0 Primary emulsion (10% w/wt)

Sunflower oil (10% w/wt)

Wj: Aqueous phase (80% w/wt): Silica particles (1% w/wt in aqueous phase), distilled water, 8% glucose, pH adjusted to 2

- Example 3

W2/O Primary emulsion

W₂: Aqueous phase (30%w/wt): KC1 (1.7% w/wt in aq phase), distilled water O: Oil Phase (70% w/wt): 1.25% monoglyceride and 2.5% triglyceride (%w/w in the oil phase); Sunflower oil (commercially available)

W2/O/W1 Double emulsion

W₂/0 Primary emulsion (10% w/wt)

Sunflower oil (10% w/wt)

Wi: Aqueous phase (80% w/wt): Silica particles (1% w/wt in aqueous phase), Na-caseinate (1% w/wt in aqueous phase), distilled water and, 8% glucose, pH adjusted to 2 (with HCl)

- Example 4:

W2/0 Primary emulsion

W2: Aqueous phase (30%wt/wt): KC1 (1.7% wt wt in aq phase), distilled water O: Oil Phase (70% wt wt): 1.25% monoglyceride and 2.5% triglyceride (%wt wt in the oil phase); Sunflower oil (commercially available)

W2/0/W1 Double emulsion

W2/0 Primary emulsion (10% wt/wt)

Sunflower oil (10% wt/wt)

Wl : Aqueous phase (80% wt/wt): Na-caseinate (1% w/wt in aqueous phase), distilled water and, 8% glucose, pH adjusted to 2

Example 5: W2/0 Primary emulsion

W2: Aqueous phase (30%w/wt): KC1 (1.7% w/wt in aq phase), gelatin 160g bloom (1% w/w in aq phase), distilled water O: Oil Phase (70% w/wt): 1.25% monoglyceride and 2.5% triglyceride (%w/w in the oil phase); Sunflower oil (commercially available)

W2/0/W1 Double emulsion

W2/0 Primary emulsion (10% wt wt)

Sunflower oil (10% wt/wt)

Wl : Aqueous phase (80% wt/wt of total double emulsion): Na-caseinate (1% wt/wt in aqueous phase), distilled water, glucose (8% wt/wt in aq phase)

- Process parameters:

All examples:

Primary emulsion (W₂/O):

All oil-phase and water-phase ingredients were mixed and heated separately, and combined at ~70°C using a Silverson High Shear mixer. This pre-emulsion was then passed through a bench-scale scraped-surface heat exchanger ("A unit"), and a pin stirrer ("C unit"), both cooled with water at 5°C. The resulting emulsion was passed a second time through the "A" and "C" units, in order to further reduce droplet size. Final emulsion temperature at the outlet from the C-unit was measured as -1 1 °C for all experiments. Droplet size of the primary emulsion is ~4μηι.

Secondary Emulsion (W₂/O/W₁):

Aqueous phase (Wj) preparation:

Example 1 (Na-caseinate): Na-caseinate is dispersed in distilled water at ambient temperature. A sugar (e.g. glucose or fructose) or salt is added in order to match the osmotic pressure.

Example 2-3 (particles): Particles are dispersed in water at pH 2 using an ultrasonic probe for 3 minutes. A sugar (e.g. glucose or fructose) can subsequently be added in order to match the osmotic pressure. A low pH is required because Silica particles are charged at pH>4 (R. Pichot et al, J Coll. & Interface Sci 329, 2009), which increases inter-particle repulsion and thus decreases their ability to stabilise emulsions effectively.

The primary (W2/0) emulsion is mixed with sunflower oil, and slowly added to the aqueous phase. Subsequently, emulsification takes place in a Silverson High Shear Mixer, at 8000rpm for 3 minutes. Alternatively, membrane emulsification can be used for the second emulsification step. A 15um laser drilled stainless steel membrane can be used for this purpose, with appropriate settings to obtain the desired droplet size and size distribution.

- Results - Experiment 1

Table 1 shows globule sizes obtained for various formulations. Shear during the secondary emulsification step has been kept to a minimum, so as not to break the primary emulsion. Improved processing, e.g. membrane emulsification, is expected to decrease the average droplet size significantly, by applying much less shear during the secondary emulsification step, yet achieving better control over process parameters.

Because creaming has not been prevented in these emulsions, double emulsion globules are tightly packed within the cream layer. The globules are therefore constantly in extremely close contact, which explains the coalescence between globules. The primary emulsion droplet size, however, remains nearly unchanged over a period of at least 8 weeks (internal droplet size is 3-4μιη). A reduction of double emulsion globule size by improved processing, as well as addition of a hydrocolloid to increase viscosity and hence prevent creaming, is expected to reduce the rate of coalescence significantly.

50% diluted samples d3,2 (μπι)

with the following

added to the secondary

aqueous phase after production after 1 day after 1 week after 4 weeks

10% glucose 23.0 27.5 27.3 41.6

2.6% NaCl 25.1 25.2 35.3 30.1

10% fructose 20.2 24.9 29.9 50.7

5% glucose 27.1 37.9 48.8 »

20% glucose 25.0 23.8 25.7 32.4

1.3% NaCl 31.5 33.6 33.6 44.5

Table 1: Globule size of various double emulsion formulations of Experiment 1

Despite coalescence, the structure of the double emulsions is maintained for a period of at least 8 weeks, although after 4 weeks coalescence results in increasingly large globules. Osmotic pressure does not have to be exactly balanced for good stability. However, at least some water soluble solute, e.g. a sugar, should be present in the secondary aqueous phase, as the primary emulsion has a tendency to break out of the double emulsion structure when the aqueous phase comprises solely of emulsifier and distilled water. Although coalescence occurs between double emulsion globules, due to the close proximity between these globules in the cream layer of the emulsion, the emulsions retain primary emulsion droplets within the double emulsion globules (Figures 1 & 2).

A method to asses the stability of the double emulsion, especially with respect to the amount of primary emulsion retained within the double emulsion globules, is to measure the conductivity of the double emulsion over time. The release of ions present in W₂ to the continuous aqueous phase Wi results in an increase in the conductivity of the double emulsion. After one month, only 20% of total ions have been released (Figure 4), so most solutes remain entrapped within the primary aqueous phase.

A commonly encountered problem in double emulsions is the diffusion of small, water soluble molecules from one water phase to the other, which is aided the presence of small- molecule emulsifiers. The combination of fat crystal-stabilised primary emulsion and Na- caseinate used to stabilise the double emulsion eliminates the problem of diffusing emulsifiers, as both species are anchored at their respective interfaces. Most diffusion of water or solutes within the water between the two aqueous phases is thus prevented, although some release will invariably occur due to imperfections in the shells.

Results - Experiment 2 and 3

Pickering stabilised oil/water emulsions show reduced coalescence compared to protein- stabilised ones, as the particles irreversibly adsorb and closely pack at the interface. This is beneficial also to double emulsions containing fat crystals: by using Pickering stabilisation not only on the primary emulsion, but also on the double emulsion globules, stability of the double emulsion is increased compared to Na-caseinate stabilised samples. Stability is extremely good in light of the fact that in creamed samples, contact times between two double emulsion globules are infinite, which usually drives coalescence.

When Na-caseinate is added to the silica particles at pH 2, the protein structure is changed so that the viscosity of the emulsion increases to gel-like consistency, resulting in smaller double emulsion globule sizes as well as reducing creaming rates, which, in turn, reduce coalescence between globules further.

Again, at least some sugar will usually be present in the continuous aqueous phase, although exact matching of the osmotic pressure is not crucial. - Results - Experiment 4

By reducing the pH to 2, stability against coalescence of double emulsion globules stabilised by Na-caseinate in Wl is significantly increased. This is thought to be due to the influence of the acid on the protein, which causes the double emulsion globules to aggregate into a gel network, hence arresting globule movement and significantly increasing the viscosity of the double emulsion. As the globules are no longer free to move, coalescence events become less frequent, which explains the excellent stability these emulsions show: average droplet size after production is approximately 21μπι and after 1 month ~26 μηι (see Fig 6).

Claims

1. A comestible product comprising a substantially stable water-in-oil-water double emulsion, the double emulsion comprising monoglycerides, triglycerides, water, oil and a further emulsifier.

2. A comestible product according to claim 1, wherein the double emulsion does not comprise PGPR.

3. A comestible product according to claim 1 or claim 2, wherein the further emulsifier is selected from a polymeric surfactant and a surfactant comprising nanoparticles, or mixtures thereof.

4. A comestible product according to claim 3, wherein further emulsifier is selected from sodium caseinate, gelatin, BSA, lecithin and silica nanoparticles.

5. A comestible product according to any preceding claim, wherein the oil is selected from sunflower oil, soy bean oil, canola oil and mixtures thereof.

6. A comestible product according to any preceding claim, wherein the triglyceride is tripalmitin, tristearate or a mixture thereof.

7. A comestible product according to any preceding claim, wherein the double emulsion comprises 97% to 55% weight/weight of aqueous phase and 3% to 45% weight/weight oil phase.

8. A comestible product according to any preceding claims, wherein the first aqueous phase and/or second aqueous phase comprise hydrocolloids such as alginates, carrageenans, gelatin, cmc (carboxymethylcellulose), galactomannan etc.

9. A comestible product according to any preceding claim, which is a mayonnaise or salad dressing.

10. A method of making a water-in-oil-in-water double emulsion for a comestible product comprising the steps of:

(a) making a primary emulsion, the primary emulsion comprising approximately 10 to 70% weight/weight of a first aqueous phase comprising water and approximately 90 to 30% weight/weight of a first oil phase, the oil phase comprising an oil, the oil comprising a mixture of mono- and triglycerides (MG and TG);

(b) mixing the primary emulsion with a second aqueous phase, a further emulsifier and optionally a second oil phase to

1 1. A method according to claim 10, wherein the double emulsion comprises:

approximately 10 to 50% weight/weight primary emulsion;

approximately 90 to 50% second aqueous phase; and

approximately 0 to 20% second oil phase.

12. A method according to claim 9 or 10, wherein in step (b) the components are mixed using a high shear mixer or by membrane emulsification.

13. A method according to claim 12, wherein the membrane uses a pore size of approximately 15μπι.

14. A method according to claims 10 to 13, wherein the further emulsifier is selected in an amount of approximately 0.5 to 7% weight/weight of the aqueous phase.

15. A method according to claims 10 to 14, wherein the further emulsifier is selected from (i) polymeric surfactant and (ii) a surfactant comprising nanoparticles.

16. A method according to claims 10 to 15, wherein the further emulsifier is selected from sodium caseinate, lecithin, Bovine Serum Albumin (BSA), gelatin, whey protein isolate ( PI), modified starch and silica nanoparticles.

17. A method according to claims 10 to 16, wherein the first oil phase and/or second oil phase is selected from sunflower oil, soy bean oil and canola oil.

18. A method according to claims 10 to 16 wherein the first aqueous phase and/or second aqueous phase comprise one or more solutes selected from salts, sugars and micronutrients.

19. A method according to claims 10 to 18 wherein the first aqueous phase and/or second aqueous phase contain hydrocolloids such as alginates, karrageenans, gelatin, cmc (carboxymethylcellulose), galactomannans etc.

20. A method according to claims 10 to 19, wherein the second aqueous phase comprises one or more osmotically active solutes to match the osmotic potential of solutes in the primary aqueous phase of the primary emulsion.

21. A method according to any of claims 10 to 20, wherein the triglyceride is selected from tripalmitin, tristearate and mixtures thereof.