WO2010121490A1

WO2010121490A1 - Method for preparing foams and foams comprising ethylcellulose particles

Info

Publication number: WO2010121490A1
Application number: PCT/CN2010/000550
Authority: WO
Inventors: Theodorus Berend Jan Blijdenstein; Jian Cao; Petrus Wilhelmus Nicolaas De Groot; Weichang Liu; Simeon Dobrev Stoyanov; Weizheng Zhou
Original assignee: Unilever N.V.; Unilever Plc; Hindustan Unilever Limited
Priority date: 2009-04-24
Filing date: 2010-04-22
Publication date: 2010-10-28

Abstract

A method for preparation of an aqueous foam, a method for preparation of an aerated food product, an aqueous foam comprising ethylcellulose particles, food products comprising the aqueous foam, ethylcellulose particles and use of ethylcellulose particles are disclosed. The method for preparation of an aqueous foam comprises the steps: a) dissolving ethylcellulose in an organic solvent which is miscible in water; b) addition of water to the mixture of step a), wherein the amount of water is at a weight ratio between 10:1 and 1:2 based on the organic solvent; c) evaporating organic solvent and water to a concentration of ethylcellulose of at least 1% by weight; d) additon of an acid to a pH of 4 or lower, or addition of a water-soluble salt to an ionic strength of at least 20 millimolar; or addition of a combination of acid and water-soluble salt; e) introduction of gas bubbles to the composition of step d) to create a foam.

Description

METHOD FOR PREPARING FOAMS AND FOAMS COMPRISING ETHYLCELLULOSE PARTICLES

The present invention relates to a method for preparation of an aqueous foam, as well as to a method for preparation of an aerated food product. Moreover the present invention relates to foams comprising ethylcellulose particles, food products comprising such a foam, ethylcellulose particles, and use of ethylcellulose particles to stabilise foams and in aerated food products.

Aerated food products or foams are generally known, and such foods include frozen and chilled food products, such as ice cream, mousses, and whipped cream. Gases commonly used for 'aeration' include air, nitrogen and carbon dioxide.

Two factors are of importance in the development of aerated food products, and these are (i) the foamability of the product while introducing gas into the product during manufacture and (ii) the foam stability during storage, which is whether the gas bubbles tend to coalesce or collapse and whether the foam volume is retained during storage. Many additives are known to be included in the creation of stable foams, and these generally are compounds which are present on the gas bubble surface, which means on the gas-liquid interface during manufacturing of the foam. Known additives include proteins such as sodium caseinate and whey, which are highly foamable, and biopolymers, such as carrageenans, guar gum, locust bean gum, pectins, alginates, xanthan, gellan, gelatin and mixtures thereof, which are good stabilisers.

WO 2008/019865 A1 discloses aqueous foams and food products containing these. The gas bubbles in the foam are stabilised by interfacially-active particles (e.g. proteins), which are considered to be colloidal particles having a diameter between 0.5 nanometer up to several tens of a micrometer. Aerated food products are produced by mixing a preformed aqueous foam into a food product.

WO 2007/060462 A1 discloses foams which are stabilised by polystyrene latex particles which may have an average particle size between 0.05 and 10 micrometer. The latex particles are produced by a polymerisation reaction. The latex particles may be stabilised by water-soluble/hydrophilic polymers forming a shell on the latex particles, like water-soluble poly(meth)acrylates, and various cellulosic derivatives (e.g. e.g. methylcellulose, ethylcellulose, hydroxypropylcellulose or carboxymethylcellulose). Polymer latexes stabilized with a polyacid form stable foams below the pKa value, (e.g. for poly(acrylic acid), stable foams are formed at pH values at or below its pKa of approximately 4.5) and those stabilized with a polybase form stable foams at pH values at or above the pKa value. For example, the polymer latex dispersion stabilized with poly(acrylic acid) may have a pH of less than 4, e.g. a pH ranging from 1 to 3.5.

Plasari et al. (Trans IChemE, 1997, VoI 75, Part A, p. 237-244) disclose a process to precipitate ethylcellulose nanoparticles from a solution of ethanol, using water as non- solvent, under various process conditions. The average particle size of the nanoparticles was reported to be from about 35 to about 100 nanometer, which partly aggregated into agglomerates having a size between 300 and 600 nanometer. The size of the nanoparticles was strongly dependent on the initial concentration of ethylcellulose in the solvent. The zeta-potential of the ethylcellulose nanoparticles was not determined, and will be about -40 mV, as the dispersion containing the ethylcellulose nanoparticles is not acidified, nor contains salt ions.

EP 1 992 323 A1 discloses a foamed oil-in-water emulsion, wherein the emulsion is a Pickering-emulsion. The emulsion may be stabilised by ethylcellulose particles.

WO 2008/046699 A1 discloses aerated food products in the form of a stable foam, comprising 5-80 vol% gas bubbles, 15-90 wt% water and 0.001 to 10 wt% fibres, and further containing surface-active particles at the air-water interface. These aerated food products are very stable due to attractive interaction between the surface-active particles and the fibres. The fibers preferably have a length from 1 to 50 micrometer. These fibres may be made from materials like microcrystalline cellulose or citrus fibers, or waxy materials, like camauba wax, shellac wax, or bees wax. The surface-active particles are preferably made from modified celluloses, modified starches, and insoluble proteins. They are preferably present in an amount between 0.001 and 10 wt%, and preferably have a volume weighted mean diameter between 0.01 and 10 micrometer, more preferably between 0.1 and 1 micrometer. In the examples a combination of microcrystalline cellulose fibers and ethylcellulose particles is disclosed.

WO 2009/033592 A1 discloses foams used for foods, wherein the foam may comprise ethylcellulose and a hydrocolloid. WO 2006/067064 A1 discloses a shelf stable mousse, containing a hydrocolloid as foam stabiliser. The hydrocolloids are water-soluble and may be carboxymethyl cellulose or other cellulose derivatives like methyl cellulose, hydroxypropyl cellulose.

EP 1 668 992 A1 discloses foamable food compositions and food foams, in which the foam is stabilised by solid inert particles, preferably silicates.

US 4,346,120 discloses a frozen dessert product which is aerated. It comprises a water-soluble stabiliser and a so-called blocking agent which are for example microcrystalline cellulose and cellulose fibers.

WO 2007/038745 A1 discloses cream compositions containing hydroxypropyl methylcellulose (HPMC)₁ hydroxypropyl cellulose (HPC)₁ methyl hydroxyethyl cellulose (MHEC), methyl cellulose (MC) or ethyl cellulose (EC), at a concentration up to about 0.15%, and water-soluble or water-swellable hydrocolloids like microcrystalline cellulose, hydroxyethyl cellulose, pectin, gum arabic, and others at a concentration of preferably 0.02 and 0.05%. These compositions can be used in producing whipped food compositions.

Marsh et al. (Particuology, vol. 7, 2009, p. 121-128) measure the zeta-potential of microfibrous cellulose as function of pH. The potential is about -10 mV at pH 4-12, and increases from about -10 mV to about 0 mV when the pH is decreased from 4 to 2.

Similarly, WO 2008/046698 A1 discloses stable aerated food products containing between 0.5 and 20 wt% protein, as well as fibres and surface-active particles that assemble at the air-water interface. In the examples a combination of microcrystalline cellulose fibers and ethylcellulose particles is disclosed.

WO 2008/046742 A1 also discloses aerated food products containing at least 10 wt% of water and optionally fat, wherein the amount of fat and water taken together is at least 60 wt%, as well as surface active particles and surface active fibers. Moreover the volume weighted mean diameter of the particles is smaller than the length of the fibers. In the examples a combination of microcrystalline cellulose fibers and ethylcellulose particles is disclosed, as well as a combination of citrus fibers and ethylcellulose particles.

WO 2007/068344 A1 discloses surface-active fibres, wherein the fibres have an aspect ratio of more than 10 to 1 ,000, and a length of preferably 1 to 50 micrometer. The fibers may be organic, like cellulose fibers such as citrus fibers, or inorganic, like calcium carbonate. These fibers may be used to stabilise foams. Also disclosed are aerated food products containing these fibers. One of the examples discloses a mixture of the fibers and ethylcellulose particles for creating a foam.

WO 2008/006691 A1 discloses surface-active fibres that are made of a waxy material, such as camauba or shellac wax or bee wax. It may be used in aerated food products to stabilise foams.

WO 2008/046732 A1 discloses a frozen aerated food product (e.g. icecream) comprising 0.001 to 10 wt%, of surface-active fibres, which have an aspect ratio of 10 to 1 ,000. Preferably the fibers have a length from 1 to 50 micrometer. These fibres may be made from food-grade waxy materials, like carnauba wax, shellac wax, or bees wax, or from non-waxy materials like microcrystalline cellulose or calcium carbonate. Moreover the food product may contain surface active particles that modify the surface active fibers, for example ethylcellulose or hydroxypropylcellulose. Also a method for production of a frozen aerated product is disclosed wherein particles and fibers are mixed to form a self-assembled structure, followed by a freezing step.

WO 2008/046729 A1 discloses aerated liquid food products having an overrun of at least 100%, which are gastric stable and increase satiety. These products contain microcrystalline cellulose.

US 2007/0178209 A1 discloses aerated food products which are stabilised by hydrophobic denatured protein particles, preferably egg white and egg yolk proteins. The diameter of the protein particles are that at least 50% of the particles has a diameter of more than 3 micrometer, and less than 35 micrometer. The protein particles are prepared by acidifying an aqueous protein solution to a pH of preferably below 3.6, while being sheared, at a temperature below 70⁰C. The aerated food products may comprise water-soluble stabilisers like gelatin, gum arabic, cellulose derivatives such as sodium carboxymethyl cellulose, microcrystalline cellulose, methyl and methylethyl celluloses, or hydroxylpropyl and hydroxypropylmethyl celluloses.

Dickinson E. (Colloids and Surfaces A: Physicochemical and Engineering Aspects, vol. 288, 2006, p. 3-11) discloses caseinate-stabilized emulsions into which air bubbles are introduced via simultaneous whipping and slow acidification. Aerated emulsion gels of good foam stability can be formulated.

Shrestha L.K. et al. (Journal of Colloid and Interface Science, vol. 301 , 2006, p. 274- 281) disclose aqueous foams stabilized by dispersed surfactant solid particles and lamellar liquid crystalline phase. Stable foam in the C18G5/water system was mainly due to the finely dispersed small surfactant solid particles. The average particle diameter of α-solid phase and La dispersion, respectively, was found to be less than 1 μm, to be around 0.15 μm. Shreshta et al. indicate that with decreasing particle size, improved stability of foam can be obtained.

Murray B. S. et al. (Current Opinion in Colloid & Interface Science, vol. 9, 2004, p. 314- 320) indicate in a review that foams may be stabilised by nanoparticles. As an example particles having a primary particle size of 20 nm are mentioned, but these may also be aggregated into larger particles.

EP 1 048 690 A1 discloses a cellulose-containing composite that comprises a fine cellulose and a low-viscosity water-soluble dietary fiber, which may act as a foam stabilizer, and wherein the average particle size of the fine cellulose is 30 micrometer or less when the composite is dispersed in water.

US 6,372,280 discloses acidic (pH less than 4) whipped topping, which are stable foams in an acidic environment. The foam may contain a non-ionic stabilizer, which could be water-soluble stabiliser like guar gum or locust bean gum. Also non water- soluble compounds have been disclosed, like unmodified cellulose and ethylcellulose.

US 2005/0163904 A1 discloses the preparation of a cappuccino having a frothy surface. The foam should remain stable for at least 3 minutes, more preferably 5 minutes. The composition for making the foam may comprise a biopolymer, which may be water- soluble or not water-soluble, for example xanthan gum, gum Arabic, ethyl cellulose, starches.

Wege et al. (Langmuir 2008, 24, p. 9245-9253) disclose that foams and emulsions can be stabilised by in-situ formed microparticles from a hydrophobic cellulose derivative, hypromellose phthalate (HP). HP is dissolved in aceton or ethanol, and subsequently upon addition of water and application of shear, microparticles are formed. The particle size depends on the concentration of HP in the solvent, and is reported to range from about 7.6 to 226 micrometer average particle size. The bigger the particles, the better the foam stability.

Current methods for preparing aerated food products often have the disadvantage that the foams are not stable enough to be used in a food product which upon storage remains stable for at least a month, preferably several months. The total foam volume may decreases due to collapse of bubbles, or the gas bubble size increases due to processes like coalescence. Both processes lead to changing texture of the food product. Moreover, some systems have the disadvantage that several additives are required to stabilise the foams which do not provide nutritional value. Moreover such compounds may be expensive, or not compatible for food use. Further, many of the ingredients used to stabilise the gas phase in aerated food products need to be added at fairly high levels which can have deleterious textural and/or caloric consequences.

Hence there is a need for efficient stabilisation of foams that are suitable for use in food products, while the stabiliser preferably is a cheap and commonly available raw material. Preferably the foams have high overruns and relatively small, uniformly sized gas bubbles. Moreover the use of only a low concentration of stabiliser in the food product would be advantageous. Additionally it would be advantageous if the stabilising system does not require a multitude of stabilising compounds without nutritional value. Such foams can be used in food products to create a favourable mouthfeel, like a creamy mouthfeel, without having high caloric value of food products which normally have a smooth and creamy mouthfeel.

We have now found that stable foams can be produced containing ethylcellulose particles as a stabiliser, by a method comprising a step wherein acid or salt or a combination of these is added to suspended ethylcellulose particles, prior to creating a foam. This leads to the creation of very stable foams which can be used to produce stable aerated food products. Especially when the size of the ethylcellulose particles is in the tens of nanometers range, preferably less than 100 nanometer, then highly stable foams can be made having high overrun. Preferably fibres are substantially absent from the foams produced by the method according to the invention.

Accordingly in a first aspect the present invention provides a method for preparation of an aqueous foam, comprising the steps: a) dissolving ethylcellulose in an organic solvent which is miscible in water; b) addition of water to the mixture of step a), wherein the amount of water is at a weight ratio between 10:1 and 1:2 based on the organic solvent; c) evaporating organic solvent and water to a concentration of ethylcellulose of at least 1% by weight; d) addition of an acid to a pH of 4 or lower, or addition of a water-soluble salt to an ionic strength of at least 20 millimolar; or addition of a combination of acid and water-soluble salt; e) introduction of gas bubbles to the composition of step d) to create a foam.

In a second aspect the present invention provides a method for preparation of an aerated food product, comprising the steps: a) dissolving ethylcellulose in an organic solvent which is miscible in water; b) addition of water to the mixture of step a), wherein the amount of water is at a weight ratio between 10:1 and 1 :2 based on the organic solvent; c) evaporating organic solvent and water to a concentration of ethylcellulose of at least 1 % by weight; d) addition of an acid to a pH of 4 or lower, or addition of a water-soluble salt to an ionic strength of at least 20 millimolar; or addition of an acid and a water-soluble salt; e) introduction of gas bubbles to the composition of step d) to create a foam; f) mixing the foam from step e) with one or more food ingredients; g) optionally mixing the composition from step f) with one or more other food ingredients. In a third aspect the present invention provides an aqueous foam composition comprising ethylcellulose particles having an average diameter between 30 and 500 nanometer, wherein the foam has an overrun of at least 50%.

In a fourth aspect the present invention provides a food composition comprising an aqueous foam according to the third aspect of the invention, wherein the food composition has an overrun of at least 1%.

In a fifth aspect the present invention provides the use of ethylcellulose in the form of particles having a volume weighted mean diameter between 30 and 500 nanometer to stabilise foams.

In a sixth aspect the present invention provides the use of ethylcellulose in the form of particles having a volume weighted mean diameter between 30 and 500 nanometer in aerated food products.

DETAILED DESCRIPTION

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art.

All percentages, unless otherwise stated, refer to the percentage by weight, with the exception of percentages cited in relation to the overrun.

In the context of the present invention, the average particle diameter is expressed as the d_4>3 value, which is the volume weighted mean diameter, unless stated otherwise. The volume based particle size equals the diameter of a sphere that has the same volume as a given particle.

The ranges that are indicated include the endpoints, unless stated otherwise, and are understood by the skilled person to be values which may vary within limits which are acceptable to the skilled person. These variations within certain limits may for instance be determined by measurement uncertainties.

The term 'aerated' means that gas has been intentionally incorporated into a composition, for example by mechanical means. The gas can be any gas, but is preferably, in the context of food products, a food-grade gas such as air, nitrogen, nitrous oxide, or carbon dioxide. The extent of aeration is measured in terms of 'overrun', which is defined as:

weight of unaerated mix - weight of aerated product ..... ... overrun = - - - x 100% ( 1 ) weight of aerated product

where the weights refer to a fixed volume of aerated product and unaerated mix (from which the product is made). Overrun is measured at atmospheric pressure.

A stable foam or aerated food product in the context of the present invention is defined as being stable for at least 30 minutes, more preferred at least an hour, more preferred at least a day, even more preferred at least a week, and most preferred at least a month. A stable foam can be defined to be stable with regard to total foam volume, and/or gas bubble size, and looses maximally 20% of its volume during 1 month storage, more preferably maximally 10% of its volume during 1 month storage. On the other hand systems may exist which loose more than 20% of its volume during 1 month storage, which nevertheless are considered to have a good stability, as the stability of such foams is much better than comparative foams. Stability can be described as that the foam and gas bubbles are stable against Ostwald ripening, which leads on the one hand to relatively small bubbles decreasing in size and relatively large bubbles increasing in size. This is caused by diffusion of gas from small to large bubbles, due to a higher effective Laplace pressure in the small bubbles as compared to the larger bubbles. In foams as described by the present invention, Ostwald ripening can be considered to be most important mechanism responsible for instability of the gas bubbles. An alternative mechanism for instability is coalescence, wherein two or more gas bubbles merge due to the breakage of the liquid interface between the bubbles and form one larger bubble with a larger volume.

Ethylcellulose In the present invention ethylcellulose is used as stabiliser for foams. The general structural formula of ethylcellulose is:

The degree of substitution of the ethylcellulose used in the present invention is preferably between 2 and 3, more preferably about 2.5. The average number of hydroxyl groups substituted per anhydroglucose unit (the 'monomer') is known as the 'degree of substitution' (DS). If all three hydroxyls are replaced, the maximum theoretical DS of 3 results.

Suitable sources and types of the ethylcellulose used in the present invention are supplied by for example Hercules, Aldrich, and Dow Chemicals. Suitable ethylcellulose preferably has a viscosity between 5 and 300 cP at a concentration of 5 % in toluene/ethanol 80:20, more preferably between 100 and 300 cP at these conditions.

Method for preparation of an aqueous foam The present invention provides a method for preparation of an aqueous foam, comprising the steps: a) dissolving ethylcellulose in an organic solvent which is miscible in water; b) addition of water to the mixture of step a), wherein the amount of water is at a weight ratio between 10:1 and 1 :2 based on the organic solvent; c) evaporating organic solvent and water to a concentration of ethylcellulose of at least 1 % by weight; d) addition of an acid to a pH of 4 or lower, or addition of a water-soluble salt to an ionic strength of at least 20 millimolar; or addition of a combination of acid and water-soluble salt; e) introduction of gas bubbles to the composition of step d) to create a foam.

The preferred embodiments of this first aspect of the invention as disclosed below, may be combined to give preferred embodiments of the method according to the first aspect of the invention. In step a) of this method, the concentration of ethylcellulose in the solvent is preferably between 0.1 and 6% by weight, more preferably between 0.1 and 4% by weight, more preferably between 0.1 and 3% by weight, even more preferably between 0.1 and 2% by weight, and most preferably between 0.5 and 1 % by weight. The influence of the concentration of ethylcellulose in step a), is that a lower ethylcellulose concentration in solvent yields a smaller volume weighted average particle diameter. A smaller average particle size suitably leads to increased stability of the foams that can be created.

The solvent in step a) can be any polar solvent suitable for ethylcellulose. Preferably in step a) the organic solvent comprises acetone or ethanol or a combination of these solvents, preferably at a purity of at least 98%. The ratio of water to organic solvent in step b) of the method according to the first aspect of the invention, is based on the purity of the organic solvent. The temperature in step a) is preferably between 10 and 60⁰C, more preferably between 25 and 40⁰C. The temperature that will be applied is preferably dependent on the solvent that is used. If the solvent evaporates at a relatively low temperature, then the temperature in step a) will be lower than when a solvent is used with a higher boiling point.

In step b) water is added to the solution of ethylcellulose, which leads to a partial precipitation of ethylcellulose into particles. The water is preferably distilled or de- ionised water, more preferably it is double distilled water. Preferably these ethylcellulose particles that precipitate have a volume weighted mean diameter between 30 and 500 nanometer. More preferred the ethylcellulose particles have a volume weighted mean diameter between 30 and 300 nanometer, even more preferred between 50 and 300 nanometer, most preferred between 60 and 300 nanometer, and even more preferred between 70 and 300 nanometer. In another alternative most preferred embodiment the ethylcellulose particles have a volume weighted mean diameter between 30 and 100 nanometer, preferably between 30 and less than 100 nanometer, preferably between 30 and 95 nanometer, preferably between 30 and 90 nanometer, preferably between 30 and 80 nanometer, preferably between 30 and 70 nanometer, preferably between 30 and 60 nanometer, preferably between 30 and 50 nanometer, or alternatively preferably between 50 and 70 nanometer, preferably between 50 and 60 nanometer or between 60 and 70 nanometer. In another most preferred embodiment the volume weighted mean diameter of the precipitated ethylcellulose particles is between 100 and 200 nanometer, or even between 100 and 150 nanometer. Alternatively preferably the ethylcellulose particles have a volume weighted mean diameter between 150 and 500 nanometer, preferably between 150 and 400 nanometer, alternatively preferably between 150 and 300 nanometer, preferably between 150 and 200 nanometer. Alternatively preferably the ethylcellulose particles have a volume weighted mean diameter between 200 and 500 nanometer, preferably between 200 and 400 nanometer, preferably between 200 and 300 nanometer or between 300 and 400 nanometer.

In step b) preferably the weight ratio between the amount of water and the organic solvent is between 5:1 and 1 :2, more preferably between 2:1 and 1 :2. Most preferably the weight ratio between water and organic solvent in step b) is 1 :1 , or about 1 :1.

Preferably the water is added to the mixture while being stirred, preferably under high shear conditions. The temperature in step b) is preferably between 10 and 60⁰C, more preferably between 25 and 40⁰C.

The evaporation step c) is performed in such a way that the concentration of ethylcellulose becomes at least 1 % by weight. More preferably the concentration of ethylcellulose after step c) is at least 2% by weight.

In step d) the acid preferably is chosen from hydrochloric acid, tartaric acid, acetic acid, and citric acid, or any combination of these acids, which are acids compatible for use in foods. The salt preferably comprises NaCI, KCI, MgCI₂ or CaCI₂, or any combination of these salts, which are salts compatible for use in foods.

In step d) preferably the ionic strength that is obtained is maximally 200, more preferably maximally 150 millimolar. In case a combination of acid and salt is used in step d), then preferably the strength of the combination is similar to use of only an acid to a pH of 4 or lower, or to the use of only a water-soluble salt to an ionic strength of at least 20 millimolar.

Without wishing to be limited by theory, we have determined that by the addition of acid to lower the pH and/or the introduction of the water-soluble salt in step d) of the method according to the invention, the zeta-potential of the ethylcellulose particles is changed. The zeta-potential is a measure for the surface charge of a colloidal particle, and determines whether particle attract or repulse each other. At a relatively high absolute value of the zeta-potential the ethylcellulose particles are well dispersed, due to repulsion of the particles. This behaviour is observed at a zeta-potential of the particles having an absolute value above 25 millivolt. When the zeta-potential of the particles is decreased to an absolute value below 25 millivolt, the ethylcellulose particles aggregate, leading to the ethylcellulose particles being able to stabilise a foam.

Good foam stability is observed in the region where the ethylcellulose dispersion is colloidally unstable, i.e. electrostatic repulsion between the particle is screened the particles are weakly attractive due to van der Waals forces, i.e. when the absolute value of the zeta-potential of the particles is belpw 25 millivolt. Poorer foam stability is obtained when the dispersion is stable, i.e. the particles are electrostatically repulsive, i.e. when the absolute value of the zeta-potential is above 25 millivolt.

Upon addition of acid in step d) to reach a pH of 4 or lower, the surface charge of the ethylcellulose particles is modified, and the zeta-potential of the ethylcellulose particles is decreased to an absolute value below 25 millivolt. Similarly, upon addition of a water- soluble salt to reach an ionic strength of at least 20 millimolar, the zeta-potential of the ethylcellulose particles is decreased to an absolute value below 25 millivolt. Also a combination of an acid and a water-soluble salt may be added in step d), in order to reach a zeta-potential of the ethylcellulose particles lower than 25 millivolt. A lower zeta-potential means that the ethylcellulose particles become more hydrophobic.

Thus preferably the addition of a combination of acid and water-soluble salt in step d) leads to an absolute zeta-potential of the ethylcellulose particles below 25 millivolt.

In step e) gas bubbles are introduced to the composition of step d) to create a foam, that preferably has an overrun of at least 50%. The overrun may vary from at least 50% to at least 100% or even to 400% or to 600% to about 700% or even more.

Gasses which may be introduced in step e) are preferably gases which are suitable for use in foods, such as air, nitrogen, nitrous oxide (laughing gas, N₂O), and carbon dioxide.

The temperature at which step e) is performed usually is between 0 and 100⁰C, more preferably between 15 and 80⁰C, most preferred from 20 to 40°C. In step e) the aeration step can be performed by any suitable method which produces small enough gas bubbles. Methods of aeration include (but are not limited to):

- continuous whipping in a rotor-stator device such as an Oakes mixer (E. T. Oakes Corp), a Megatron mixer (Kinematica AG) or a Mondomix mixer (Haas-Mondomix BV);

- batch whipping in a device involving surface entrainment of gas, such as a Hobart whisk mixer or a hand whisk;

- gas injection, for example through a sparger or a venturi valve;

- gas injection followed by mixing and dispersion in a continuous flow device such as a scraped surface heat exchanger,

- elevated pressure gas injection, where a gas is solubilised under pressure and then forms a dispersed gas phase on reduction of the pressure. This could occur upon dispensing from an aerosol container.

Other suitable devices are for example Silverson, Ultraturrax, Kenwood kitchen mixer, and Ross Mill. The ethylcellulose dispersions as prepared can be also be whipped vigorously by shaking the dispersion. When the mixing shear that is applied is high, then in general the bubbles in the foam are small, while at lower shear the bubbles are bigger.

At a given ethylcellulose concentration, suitably when the overrun is relatively low, the bubbles are also relatively small (average 10 to 50 micrometer), while at the higher overruns, the bubbles may reach an average diameter of 200 micrometer or even higher. In order to stabilise small bubbles more particles are required, as the total bubble surface area increases with smaller bubble diameter (at a given total fixed foam volume).

At a given concentration of ethylcellulose particles (determined as weight percent of the foam), in general it holds that the smaller the bubbles, the smaller the overrun, and the more stable the foam. In order to obtain a stable foam, the ratio between ethylcellulose particle diameter and bubble diameter is preferably larger than 1 :5, more preferably larger than 1 :10, based on the volume weighted mean diameter of the particles as defined before. In a preferred embodiment the gas bubbles are sufficiently small that they are not visible to the naked eye. This has the advantage that a food product is not obviously aerated and has a similar appearance to unaerated food products, which may be preferred by consumers. The aerated products may nonetheless be somewhat lighter in colour or more opaque due to light scattering by the small bubbles. For example, an aerated food product has a significantly reduced calorie content per unit volume, whilst being similar in appearance to the unaerated food product, (determined from the normalised culmulative frequency as described in examples 1 and 2 below). Suitably the average diameter of the air bubbles in the foams ranges from about 1 to about 500 micrometer. Preferably at least 50% of the number of gas bubbles in the foam has a diameter smaller than 200 micrometer, more preferably at least 50% of the number of gas bubbles in the foam has a diameter smaller than 100 micrometer. Even more preferred at least 75% of the number of gas bubbles has a diameter smaller than 75 micrometer, more preferred at least 50% of the number of gas bubbles in the foam has a diameter smaller than 50 micrometer, and most preferred at least 50% of the number of gas bubbles in the foam has a diameter smaller than 30 micrometer.

Gas bubble size can be measured using a spectrophotometer that can be loaded with a glass tube containing a foam sample. Light transmitted at the tube and reflected is measured and this is translated into an average bubble diameter. Alternatively a foam can be frozen to lock the structure and subsequently cut in thin slices. The average bubble diameter in these slices can be determined by microscopy. Another method is to determine the bubble size in a sample using confocal microscopy.

In general it holds that the smaller the precipitated ethylcellulose particles, the larger the overrun, as with smaller particles a larger surface area can be stabilised, at a given amount of ethylcellulose.

The foam generated in step e) of the method according to the first aspect of the invention suitably has a concentration of ethylcellulose of at least 0.01% by weight, and at most 30% by weight of the foam composition, more preferably between 0.1 and 20% by weight of the foam composition, most preferably between 0.1 and 10% by weight of the foam composition. Preferably the water-level of the foam composition created in step e) is at least 10% by weight of the foam composition. In a preferred embodiment, in step a) the composition further comprises particles of a wax, wherein the particles have a volume weighted mean diameter between 30 nanometer and 2 micrometer. More preferably the particles have a volume weighted mean diameter between 30 nanometer and 1 micrometer, even more preferred between 30 nanometer and 500 nanometer. Preferred waxes according to the present invention are one or more waxes chosen from carnauba wax, shellac wax or beeswax. Preferably the wax is a food-grade waxy material. The particles may have any shape, like spherical or elongated or rod-like.

The concentration of the waxy material in step a), if present, preferably ranges from 0.01% to 10% by weight. The weight ratio of EC to wax in the aqueous dispersion ranges from 1000:1 to 1 :1 , preferably from 100:1 to 10:1.

A wax is a non-glyceride lipid substance having the following characteristic properties: plastic (malleable) at normal ambient temperatures; a melting point above approximately 45°C (which differentiates waxes from fats and oils); a relatively low viscosity when melted (unlike many plastics); insoluble in water but soluble in some organic solvents; hydrophobic. Preferred waxes are one or more waxes chosen from carnauba wax, shellac wax or beeswax. The particles may have any shape, like spherical or elongated or rod-like or platelet-like.

Waxes may be natural or artificial, but natural waxes, are preferred. Beeswax, carnauba (a vegetable wax) and paraffin (a mineral wax) are commonly encountered waxes which occur naturally. Some artificial materials that exhibit similar properties are also described as wax or waxy. Chemically speaking, a wax may be an ester of ethylene glycol (ethane-1 ,2-diol) and two fatty acids, as opposed to fats which are esters of glycerine (propane-1 ,2,3-triol) and three fatty acids. It may also be a combination of fatty alcohols with fatty acids.

In a preferred embodiment, after step e) the foam is mixed with a water-soluble thickening agent or an aqueous solution or dispersion of a water-soluble thickening agent. Preferred thickening agents are water-soluble polysaccharides such as xanthan gum, guar gum, agar, gellan gum, and gum arabic, or a combination of these. Other suitable compounds are a protein such as gelatine, or other polymers such as polyvinylpyrrolidone (PVP), polyvinylalcohol (PVA), polyethyleneglycol (PEG) or a combination of these. For food use these thickening agents have to be food grade. The concentration of the water-soluble thickening agent, if present, ranges from 0.001 wt% to 5.0 wt%, preferably from 0.05 wt% to 1.0 wt%.

Preferably fibres are substantially absent from the aerated composition prepared by the method according to the first aspect of the invention. This means that if present, then preferably at a maximum concentration of 0.001 % by weight of the aerated composition. By 'fibre' is meant a compound having an insoluble, particulate structure, and wherein the ratio between the length and diameter ranges from 5 to infinite. Examples of such fibres are microcrystalline cellulose, citrus fibres, onion fibres, fibre particles made of wheat bran, of lignin, and stearic acid fibres. Preferably the aqueous aerated composition prepared by the method according to the first aspect of the invention comprises maximally 0.001% by weight of microcrystalline cellulose, more preferably less than 0.001% by weight of microcrystalline cellulose.

Alternatively, in a preferred embodiment, in step a) the composition further comprises a water-insoluble thickening agent. Or alternatively in another preferred embodiment, after step e) the foam is mixed with an aqueous dispersion of a water-insoluble thickening agent. Preferred water-insoluble thickening agents are chosen from microcrystalline cellulose, bacterial cellulose, silica, clay, etc., or a combination of these. Preferably, thickening agents are fibre-like materials. Very often such fibres are also food-grade. Other preferred water-insoluble thickening agents are citrus fibres, onion fibres, tomato fibres, cotton fibres, silk, their derivatives and copolymers. The fibres preferably used in the present invention have a length of preferably 0.1 to 100 micrometer, more preferably from 1 to 50 micrometer. The diameter of the fibres is preferably in the range of 0.01 to 10 micrometer. The aspect ratio (length / diameter) is preferably more than 10, more preferably more than 20 up to 1 ,000.

Without wishing to be limited by theory, it is believed that the fibres keep the bubbles separated by forming a kind of layer or barrier in between the interfaces of several bubbles, and increase the viscosity of the continuous phase. Therewith the bubbles become more stable. The concentration of the water-insoluble thickening agent in step a), if present, preferably ranges from 0.01 to 10 % by weight, more preferably 0.05 to 1.0 % by weight. Method for preparation of an aerated food product

The foam prepared using the method according to the first aspect of the invention can be used to create an aerated food product, by mixing the foam into a food product or into one or more food ingredients which subsequently can be mixed with one or more other food ingredients to provide an aerated food composition.

Hence in a second aspect the invention provides a method for preparation of an aerated food product, comprising the steps: a) dissolving ethylcellulose in an organic solvent which is miscible in water; b) addition of water to the mixture of step a), wherein the amount of water is at a weight ratio between 10:1 and 1 :2 based on the organic solvent; c) evaporating organic solvent and water to a concentration of ethylcellulose of at least 1 % by weight; d) addition of an acid to a pH of 4 or lower, or addition of a water-soluble salt to an ionic strength of at least 20 millimolar; or addition of an acid and a water-soluble salt. e) introduction of gas bubbles to the composition of step d) to create a foam; f) mixing the foam from step e) with one or more food ingredients; g) optionally mixing the composition from step f) with one or more other food ingredients.

All preferred embodiments of the method according to the first aspect of the invention, may also be preferred embodiments of the method according to the second aspect of the invention, as applicable mutatis mutandis. The preferred embodiments of the first aspect of the invention, can also be combined with each other to give preferred embodiments of the second aspect of the invention, as applicable mutatis mutandis.

Preferably the foam that is created in step e) has an overrun of at least 50%. The overrun may vary from at least 50% to at least 100% or even to 400% or even to 600% to about 700% or even more.

If required the foam may be left to drain after step e), before being mixed with the food product or food ingredient. The aerated composition obtained in step f) preferably has an overrun of at least 5%. The one or more food ingredients disclosed in step f) can be in a Yaw' form, thus not yet formulated as a ready food product. They could also be in ready form, as a food product into which the foam from step e) is mixed. The product from step f) could be a ready food product as such, or otherwise can be further processed to be mixed with one or more other food products.

Alternatively food ingredients like for example sugars or polysaccharide stabilisers (preferably without affinity to a gas-liquid interface) may be mixed with the composition from step d) prior to the foaming step e). Optionally steps e) and f) could be performed simultaneously.

The aerated food product produced according to the second aspect of the invention suitably has a concentration of ethylcellulose of at least 0.01% by weight, and at most 20% by weight of the food composition, more preferred between 0.01 and 10% by weight of the aerated food composition.

Preferably the aerated food product produced according to the second aspect of the invention comprises maximally 0.001% by weight of microcrystalline cellulose, more preferably less than 0.001 % by weight of microcrystalline cellulose.

Aqueous foam composition and ethylcellulose particles

In a third aspect the invention provides an aqueous foam composition comprising ethylcellulose particles having a volume weighted mean diameter between 30 and 500 nanometer, wherein the foam has an overrun of at least 50%.

The aqueous foam according to the third aspect of the invention suitably has a concentration of ethylcellulose of at least 0.01% by weight, and at most 30% by weight of the foam composition, more preferably between 0.1 and 20% by weight of the foam composition, and most preferred between 0.1 and 10% by weight of the foam composition. Preferably the water-level of the foam composition created is at least 10% by weight of the foam composition.

In a preferred embodiment the aqueous foam composition according to the third aspect of the invention comprises ethylcellulose particles having a volume weighted mean diameter between 30 and 300 nanometer, even more preferred between 50 and 300 nanometer, most preferred betweeen 60 and 300 nanometer, and even more preferred between 70 and 300 nanometer. Alternatively, in another preferred embodiment the ethylcellulose particles have a volume weighted mean diameter between 50 and 200 nanometer. In another alternative most preferred embodiment the ethylcellulose particles have a volume weighted mean diameter between 30 and 100 nanometer, preferably between 30 and less than 100 nanometer, preferably between 30 and 95 nanometer, preferably between 30 and 90 nanometer, preferably between 30 and 80 nanometer, preferably between 30 and 70 nanometer, preferably between 30 and 60 nanometer, preferably between 30 and 50 nanometer, or alternatively preferably between 50 and 70 nanometer, preferably between 50 and 60 nanometer or between 60 and 70 nanometer. Most preferred the volume weighted mean diameter of the precipitated ethylcellulose particles in the aqueous foam composition is between 100 and 200 nanometer, or even between 100 and 150 nanometer. In another most preferred embodiment the volume weighted mean diameter of the ethylcellulose particles is between 100 and 200 nanometer, or even between 100 and 150 nanometer. Alternatively preferably the ethylcellulose particles have a volume weighted mean diameter between 150 and 500 nanometer, preferably between 150 and 400 nanometer, alternatively preferably between 150 and 300 nanometer, preferably between 150 and 200 nanometer. Alternatively preferably the ethylcellulose particles have a volume weighted mean diameter between 200 and 500 nanometer, preferably between 200 and 400 nanometer, preferably between 200 and 300 nanometer or between 300 and 400 nanometer.

One of the advantages of an average ethylcellulose particle size at the lower end of the indicated preferred ranges (at a mean particle size of less than about 100 nanometer), is that the overrun reached can be higher than with particles at the higher end of the preferred ranges.

Preferably the zeta-potential of the ethylcellulose particles has an absolute value below 25 millivolt, leading to stable foams. Consequently the third aspect of the invention also provides an ethylcellulose particle, having a diameter between 30 and 500 nanometer, wherein the absolute value of the zeta-potential of the particle is below 25 millivolt.

Preferably such particle having an absolute value of the zeta-potential of the particle of below 25 millivolt has a diameter between 30 and 300 nanometer, even more preferred between 50 and 300 nanometer, most preferred betweeen 60 and 300 nanometer, and even more preferred between 70 and 300 nanometer. Alternatively, in another preferred embodiment such ethylcellulose particles have a volume weighted mean diameter between 50 and 200 nanometer. In another alternative most preferred embodiment such ethylcellulose particles have a volume weighted mean diameter between 30 and 100 nanometer, preferably between 30 and less than 100 nanometer, preferably between 30 and 95 nanometer, preferably between 30 and 90 nanometer, preferably between 30 and 80 nanometer, preferably between 30 and 70 nanometer, preferably between 30 and 60 nanometer, preferably between 30 and 50 nanometer, or alternatively preferably between 50 and 70 nanometer, preferably between 50 and 60 nanometer or between 60 and 70 nanometer. Most preferred the volume weighted mean diameter of the ethylcellulose particles in the aqueous foam composition is between 100 and 200 nanometer, or even between 100 and 150 nanometer. In another most preferred embodiment the volume weighted mean diameter of the precipitated ethylcellulose particles is between 100 and 200 nanometer, or even between 100 and 150 nanometer. Alternatively preferably the ethylcellulose particles have a volume weighted mean diameter between 150 and 500 nanometer, preferably between 150 and 400 nanometer, alternatively preferably between 150 and 300 nanometer, preferably between 150 and 200 nanometer. Alternatively preferably the ethylcellulose particles have a volume weighted mean diameter between 200 and 500 nanometer, preferably between 200 and 400 nanometer, preferably between 200 and 300 nanometer or between 300 and 400 nanometer.

Preferably the absolute value of the zeta-potential of the ethylcellulose particles is below 20 millivolt, more preferred below 15 millivolt.

Preferably the aqueous foam composition comprises gas bubbles, wherein at least 50% of the number of gas bubbles has a diameter smaller than 200 micrometer. More preferred, at least 50% of the number of gas bubbles has a diameter smaller than 100 micrometer. Even more preferred at least 75% of the number of gas bubbles has a diameter smaller than 75 micrometer, more preferred at least 50% of the number of gas bubbles in the foam has a diameter smaller than 50 micrometer, and most preferred at least 50% of the number of gas bubbles in the foam has a diameter smaller than 30 micrometer. Preferably the aqueous foam composition according to the third aspect of the invention comprises maximally 0.001 % by weight of microcrystalline cellulose, more preferably less than 0.001% by weight of microcrystalline cellulose.

All preferred embodiments of the methods according to the first and second aspects of the invention, may also be preferred embodiments of the composition of the third aspect of the invention, as applicable mutatis mutandis. These preferred embodiments may also be combined to give preferred embodiments of the third aspect of the invention, as applicable mutatis mutandis.

Food products

Preferably the aqueous foam according to the third aspect of the invention is used to make a food composition comprising such an aqueous foam, wherein the food composition has an overrun of at least 1%. More preferred, such food composition has an overrun of at least 5%, even more preferred at least 10%, most preferred at least 20%. Preferably the food product has an overrun of at most 150%, more preferably at most 120%, most preferably at most 100%.

Preferably the food product according to the fourth aspect of the invention contains an ethylcellulose particle according to the third aspect of the invention. Hence the food product according to the invention preferably comprises an ethylcellulose particle, having a diameter between 30 and 500 nanometer, wherein the absolute value of the zeta-potential of the particle is below 25 millivolt. Preferred aspects of the ethylcellulose particles with regard to mean particle size and zeta-potential have been given in the context of the third aspect of the present invention. These preferred aspects are also applicable to the fourth aspect of the present invention, mutatis mutandis.

Preferably the food product comprises maximally 0.001% by weight of microcrystalline cellulose, more preferably less than 0.001 % by weight of microcrystalline cellulose.

Advantageously the food products comprising the foams according to the invention remain stable for at least a month, preferably several months. With stable is meant that the foam is stable, which means that gas bubbles in the foam do not coalescence to become larger gas bubbles. Moreover, and more importantly, ethylcellulose particles prevent shrinking of small bubbles and consequently formation of larger bubbles, hence the particles lead to reduced Ostwald ripening.

Suitable aerated food products are for example dressings like mayonnaise. Such dressings may have a total oil content ranging from 5% to 70% or 80% by weight. All such products are within the scope of the present invention.

The foams can also be used in food products to provide solid or semi-solid (e.g. spreadable) food products having a lower calorie content, while not being visible in the food product.

Further examples of preferred food products are cereal bars, chocolate bars, cookies and biscuits, confectionery products, condiments, confectionary, beverages, desserts, snacks, spreads like margarine or low fat margarines or dairy spreads, ice cream, dressings, mayonnaise, sauces, bakery products like bread, shortenings, cheese (soft cheese, hard cheese), soups, dairy drinks, fruit drinks or juices, vegetable drinks or juices, combinations of dairy, and/or fruit, and/or vegetable drinks, cocoa drinks, and especially dairy mini-drinks.

Other preferred food compositions are frozen foods, such as frozen confections like icecream, or other frozen desserts.

Also soups (both in dry form (which have to be reconstituted with water), as well as liquid soups) are within the scope of the present invention. By incorporation of the foam into such food products, a creamy soup can be obtained, which does not have the calories associated normally with creamy soups (to which generally cream is added).

In case the food product is a beverage, more specifically a fruit drink, or combination of fruit and dairy drink, it preferably comprises at least 10% by weight of the composition of a fruit component, wherein the fruit component is selected from fruit juice, fruit concentrate, fruit juice concentrate, fruit puree, fruit pulp, comminuted fruit, fruit puree concentrate, and combinations thereof. Examples of such fruit components are orange juice, apple juice, grape juice, peach pulp, banana pulp, apricot pulp, concentrated orange juice, mango pulp, concentrated peach juice, raspberry puree, strawberry puree, apple pulp, raspberry pulp, concentrated grape juice, concentrated aronia juice, and concentrated elderberry juice. Preferably such a beverage comprises at least 30% by weight of the beverage of said fruit component, more preferred at least 40% by weight of the beverage of said fruit component. These amounts are calculated as if undiluted, non-concentrated fruit juices and purees and the like are used. Thus, if 0.5% by weight of a 6-fold fruit concentrate is used, the actual amount of fruit component incorporated is 3% by weight of the beverage. Any commonly available fruit component might be used in the beverages according to the invention, and may be selected from one or more of the following fruit sources: citrus fruit (e.g. orange, tangerine, lemon or grapefruit); tropical fruit (e.g. banana, peach, mango, apricot or passion fruit); red fruit (e.g. strawberry, cherry, raspberry or blackberry), or any combination thereof.

In a further preferred embodiment the food product is a spread such as water-in-oil emulsions, for example a margarine or low fat margarine type food product. A spread may also be an oil-in-water emulsion, like dairy spreads or fresh soft cheeses. Suitably the total triglyceride level of such a spread may range from about 1% by weight to 90% by weight of the composition, preferably from 10% by weight to 85% by weight of the composition, more preferred from 20% to 70% by weight, most preferred from 30% to 60% by weight of the composition.

Especially preferred aerated food products according to the present invention are dairy drinks, which may for instance be used as a meal replacer.

The food product may be dried and contain less than 40% water by weight of the composition, preferably less than 25%, more preferably from 1 to 15%. Alternatively, the food may be substantially aqueous and contain at least 40% water by weight of the composition, preferably at least 50%, more preferably from 65 to 99.9%.

The food preferably comprises nutrients including carbohydrate (including sugars and/or starches), protein, fat, vitamins, minerals, phytonutrients (including terpenes, phenolic compounds, organosulfides or a mixture thereof) or mixtures thereof. The food may be low calorie (e.g. have an energy content of less than 100 kCal per 100 g of the composition) or may have a high calorie content (e.g. have an energy content of more than 100 kCal per 100 g of the composition, preferably between 150 and 1000 kCal). The food may also contain salt, flavours, colours, preservatives, antioxidants, non- nutritive sweetener or a mixture thereof. AII preferred embodiments of the methods according to the first and second aspects of the invention, and the composition of the third aspect of the invention, may also be preferred embodiments of the composition of the fourth aspect of the invention, as applicable mutatis mutandis. These preferred embodiments may also be combined to give preferred embodiments of the fourth aspect of the invention, as applicable mutatis mutandis.

Use of ethylcellulose particles In a fifth aspect the present invention provides the use of ethylcellulose in the form of particles having a volume weighted mean diameter between 30 and 500 nanometer to stabilise foams.

In preferred embodiments of both the fifth and sixth aspect of the invention, the ethylcellulose particles have a volume weighted mean diameter between 30 and 300 nanometer, even more preferred between 50 and 300 nanometer, most preferred betweeen 60 and 300 nanometer, and even more preferred between 70 and 300 nanometer. Alternatively, in another preferred embodiment the ethylcellulose particles have a volume weighted mean diameter between 50 and 200 nanometer. In another alternative most preferred embodiment such ethylcellulose particles have a volume weighted mean diameter between 30 and 100 nanometer, preferably between 30 and less than 100 nanometer, preferably between 30 and 95 nanometer, preferably between 30 and 90 nanometer, preferably between 30 and 80 nanometer, preferably between 30 and 70 nanometer, preferably between 30 and 60 nanometer, preferably between 30 and 50 nanometer, or alternatively preferably between 50 and 70 nanometer, preferably between 50 and 60 nanometer or between 60 and 70 nanometer. Most preferred the volume weighted mean diameter of the ethylcellulose particles is between 100 and 200 nanometer, or even between 100 and 150 nanometer. In another most preferred embodiment the volume weighted mean diameter of the precipitated ethylcellulose particles is between 100 and 200 nanometer, or even between 100 and 150 nanometer. Alternatively preferably the ethylcellulose particles have a volume weighted mean diameter between 150 and 500 nanometer, preferably between 150 and 400 nanometer, alternatively preferably between 150 and 300 nanometer, preferably between 150 and 200 nanometer. Alternatively preferably the ethylcellulose particles have a volume weighted mean diameter between 200 and 500 nanometer, preferably between 200 and 400 nanometer, preferably between 200 and 300 nanometer or between 300 and 400 nanometer.

Preferably the zeta-potential of the ethylcellulose particles in the fifth aspect and sixth aspect of the invention have an absolute value below 25 millivolt, preferably below 20 millivolt, more preferred below 15 millivolt, leading to stable foams and/or stable aerated food products.

Alternatively the fifth aspect of the present invention provides a method for the use of ethylcellulose in the form of particles having a volume weighted mean diameter between 30 and 500 nanometer to stabilise foams, comprising adding the particles to a fluid, and injecting a gas into the fluid to aerate it.

Alternatively the sixth aspect of the present invention provides a method for the use of ethylcellulose in the form of particles having a volume weighted mean diameter between 30 and 500 nanometer in aerated food products, comprising adding the particles to a fluid, injecting a gas into the fluid to aerate it, and adding the aerated fluid to a food ingredient or a food product.

Preferred embodiments related to the ethylcellulose particles in these alternative fifth and sixth aspects of the invention have been indicated herein before in relation to the fifth and sixth aspects of the invention.

Preferred aspects disclosed in connection with the first, second, third, and fourth aspects of the present invention, may also be applicable to the fifth and sixth aspects of the present invention, mutatis mutandis.

The various features and embodiments of the present invention, referred to in individual sections above apply, as appropriate, to other sections, mutatis mutandis. Consequently features specified in one section may be combined with features specified in other sections, as appropriate. All publications mentioned in the above specification are herein incorporated by reference. Various modifications and variations of the described methods and products of the invention will be apparent to those skilled in the art without departing from the scope of the invention. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention which are apparent to those skilled in the relevant fields are intended to be within the scope of the claims.

DESCRIPTION OF FIGURES

Figure 1 : Typical curve of zeta-potential of ethylcellulose particles as function of pH, showing increasing zeta-potential upon decreasing pH, from example 2.

Figure 2: Cryo-SEM-images of foams prepared from 2wt% ethylcellulose dispersions, from example 2:

A: sample 1 (pH6, no salt, comparative example), bar = 1 micrometer

B: sample 2, (pH 3, no salt), bar = 100 nanometer

C: sample 4 (pH 6, 20 mM MgCI₂), bar = 100 nanometer

Figure 3: Transport mean free path evolution λ(t)/ λ(0) of gas bubbles in mayonnaise aerated by whipping (open diamonds 0) and by aeration using ethylcellulose foam

(according to the invention) (closed diamonds ♦); from example 5.

Figure 4: SEM-images of frozen aerated compositions from example 7;

A: 1 wt% ethylcellulose; left fresh, right temperature abused;

B:, 2 wt% ethylcellulose; left fresh, right temperature abused;

C: 4 wt% ethylcellulose; left fresh, right temperature abused.

Figure 5: SEM-image of a temperature abused frozen aerated composition, product B from example 7. The arrows show a close up of small gas bubbles, covered by a corrugated layer of ethylcellulose particles.

Figure 6: SEM-images of frozen aerated composition product D from example 7; WPC 80; left fresh, right temperature abused Figure 7: SEM-image of frozen aerated compositions containing 4wt% ethylcellulose, product E from example 8.

EXAMPLES

The following non-limiting examples illustrate the present invention.

Materials

Aqualon^® Ethylcellulose (type N 100) was purchased from Hercules (Widnes, UK). Ethoxyl content was 48.0-49.5%, and degree of substitution was 2.46-2.57. Viscosity was 80-105 mPa.s (at 5% and 25⁰C in 80/20 toluene/ethanol).

Acetone, analytical grade, was obtained from Sigma Chemicals (Schnelldorf, Germany) and used without further purification. Deionised water was obtained from a Millipore filter system. Zein from corn was obtained from Sigma-Aldrich.

Particle sizing / electrophoresis

Dynamic light scattering measurements were carried out using a Zetasizer Nano ZS instrument (Malvern Instruments, Malvern, UK) to determine the average particle diameter. Samples were measured without any dilution at 25°C. The viscosity of water was assumed in all cases and a refractive index of 1.59 was used in the analysis. The results from the measurements are the z-average particle size and the standard deviation of the z-average particle size (which relates to the peak width of a distribution curve of the particle size). For monodisperse systems with a narrow distribution, which is the case for ethylcellulose particles of the present invention, the difference between the z-average particle diameter and volume weighted mean diameter (d₄,₃) is smaller than 10%. In the present case the z-average diameter is about 10% larger than d_{4 3}-

Zeta-potential The zeta-potential is determined by electrophoresis, also using the Metasizer Nano ZS instrument (Malvern Instruments, Malvern, UK). For this purpose, an electric field is applied to a dispersion containing colloidal particles. From the velocity of the particles in this electric field, i.e. their electrophoretic mobility, the zeta potential can be calculated by using the Henry equation with the Smoluchowski approach (P. C. Hiemenz, Principles of Colloid and Surface Chemistry, Second edition, Marcel Dekker Inc., New York, 1986, Chapter 13).

Bubble diameter The bubble diameter in the foams is estimated using a turbiscan turbidity measurement. In principle this is a spectrophotometer that can be loaded with a glass tube containing a foam sample. Light transmitted at the tube and reflected is measured. This is translated into average bubble diameter.

Detailed procedure: sample volumes of approximately 20 ml. were studied by turbidimetry using a Turbiscan Lab Expert (Formulaction, Toulouse, France). We interpret the average backscattering along the height of the foam sample with exclusion of the top and bottom parts where the backscattering is affected by edge effects. The backscattering (BS) is related to the transport mean free path (λ) of the light in the sample through:

BS = 4= (2)

In turn, the transport mean free path of light is related to the mean diameter (d) and the volume fraction (Φ) of the gas bubbles through:

3Φ(1 - sOQ ⁽³⁾

Where g and Q are optical constants given by Mie theory (G. F. Bohren and D.R.Huffman, Absorption and Scattering of Light by Small Particles. Wiley, New York, 1983). For foam dispersed in a transparent liquid, this method provides an estimate of the number average bubble size.

Example 1 : Food product stabilised by ethylcellulose particles

Foams stabilised by ethylcellulose particles were prepared, starting from several initial concentrations of ethylcellulose in organic solvent (see table 1), by the following method:

1. Ethylcellulose powder was dissolved in 100 ml acetone (purity >98%) at 35°C in a 500 mL beaker until completely dissolved; at the concentration of ethylcellulose in acetone as indicated in table 1. 2. An equal volume of distilled water (at room temperature, about 22°C) was quickly added into the ethylcellulose solution under strong stirring to precipitate the ethylcellulose into particles.

3. The solution was left to stir for another 10 minutes after which the acetone and some of the water were evaporated under low pressure in a rotary evaporator, until a final concentration of ethylcellulose in water of 2% was obtained.

4. The measured z-average diameter of the ethylcellulose was as indicated in table 1 ; the corresponding volume weighted mean diameter d_{4 3} of the precipitated ethylcellulose particles was consequently between about 0.09 and about

0.2 micrometer.

5. Tartaric acid was added to reach a pH of 3.

6. The dispersion was whipped with air, using a Kenwood Chef mixer for 10 minutes) at maximum speed.

7. The foam was left to drain for 2 hours.

Table 1 Concentration ethylcellulose in solvent and influence on volume weighted particle diameter and overrun of foam.

The stability of the foam was determined by measuring the average air bubble diameter as function of time, which is a measure for the stability of the foam. It was observed that all foams were stable, with best results for the smallest average particle diameter. With the smallest average ethylcellulose particle diameter, least bubble coalescence and coarsening occurred. The foam according to sample 2 was manually mixed with a commercially available mayonnaise (Calve) having an oil content of 70%, to create an aerated mayonnaise. The concentration of ethylcellulose based on the total product was 0.35% by weight. The amount of air in the aerated mayonnaise was 10% by volume, which amounts to an overrun of about 11 %. The aerated mayonnaise was stable for 9 months, which was visually checked by observation of bubble diameter in the product. Coalescence of air bubbles was not observed during storage of the aerated mayonnaise.

Example 2: Foams stabilised by ethylcellulose particles, comparison between non-activated and activated ethylcellulose

Foams stabilised by ethylcellulose particles were prepared, starting from 1% weight per volume of ethylcellulose in acetone (see table 2), by the following method:

1. Ethylcellulose powder was dissolved in 100 ml acetone (purity >98%) at 35°C in a 500 ml_ beaker until completely dissolved.

2. An equal volume of distilled water (at room temperature, about 22°C) was quickly added to the ethylcellulose solution under strong stirring to precipitate the ethylcellulose into particles.

3. The solution was left to stir for another 10 minutes after which the acetone and some of the water were evaporated under low pressure in a rotary evaporator, until a final concentration of ethylcellulose in water of 2% was obtained. The measured z- average diameter of the ethylcellulose was 130+/-20 nm.

4. The ethylcellulose disperson was divided in four parts, and four portions of 20 ml_ were added into four beakers of 60 ml_. Subsequently pH or salt concentration were changed by adding required amounts of tartaric acid, NaCI or MgCI₂, all in solid powder form, as indicated in table 2. The evolution of the zeta-potential of the ethylcellulose particles upon decrease of the pH is shown in Figure 1, for the particles which are acidified by adding tartaric acid. This shows that at a pH lower than 4, the absolute value of the ethylcellulose particles is lower than 25 mV. 5. The four dispersions of ethylcellulose particles were foamed with air for 4 minutes, using a handheld aerolatte mixer (Radlett, UK). Table 2 Overrun and lifetime of foams prepared from 2 wt% ethylcellulose dispersion

From the results indicated in table 2 it appeared that the foamability and stability of the foams prepared in acidic environment and those in the presence of salt is superior to when the foams are prepared at neutral pH, in the absence of salt.

Firstly, the overruns of samples 2, 3, and 4 directly after aeration are superior to the comparative sample 1 , illustrated by the high overruns achieved.

Secondly, after 24 hours storage the overrun of comparative sample 1 has decreased significantly from 100% to 25%.

Figure 2 illustrates this difference further. In these cryo-SEM images selected from some of the samples in table 2, films between air bubbles are highlighted, and areas where the bubbles and interfaces are present are indicated by the dashed lines. Picture A (sample 1 , pH 6, no salt, comparative example) shows a part of a gas bubble 11 at the left, a part of a gas bubble 12 at the right, and the interface 13 between the bubbles 11 and 12. The structures that can be seen in the volume of the interface 13 between the bubbles 11 and 12 are concentrations of ethylcellulose particles and these particles do not have a particular tendency to accumulate at the interfaces 14 and 15. The structure that is shown in gas bubble 11 within the dashed triangle, is the internal surface of the gas bubble 11 , which (if it would be in 3D) bends out of the picture downward left. It is shown that this surface is not complete covered by ethylcellulose particles, some empty holes can be seen. Picture B (sample 2, pH 3, no salt) shows a part of a gas bubble 21 at the left, a part of a gas bubble 22 at the right, and the interface 23 between the bubbles 21 and 22. It can be seen that the ethylcellulose particles have a strong tendency to accumulate at interfaces 24 and 25, which is different than in comparative sample 1. The structure that is shown in gas bubble 21 within the dashed triangle, is the internal surface of the gas bubble 21 , which (if it would be in 3D) bends out of the picture downward left. It is shown that this surface is more covered by ethylcellulose particles, than in sample 1.

Picture C (sample 4, pH 6, 20 mM MgCI₂) shows a part of a gas bubble 31 at the left, a part of a gas bubble 32 at the right, and the interface 33 between the bubbles 31 and 32. It can be seen that the ethylcellulose particles have a strong tendency to accumulate at interfaces 24 and 25, which is different than in comparative sample 1 and similar to sample 2.

The structure that is shown in gas bubble 32 within the dashed triangle, is the internal surface of the gas bubble 32, which (if it would be in 3D) bends out of the picture downward right. It is shown that this surface is more covered by ethylcellulose particles, than in sample 1.

Based on the data in table 2 and the pictures in Figure 2, this difference between the comparative sample 1 and the samples according to the invention, indicates that decreasing pH or having sufficient ionic strength allows ethylcellulose particles to accumulate at the air-water surface and be functional as foam stabiliser.

Example 3: Production of foams stabilised by ethylcellulose particles

Foams stabilised by ethylcellulose particles were prepared, starting from several initial concentrations of ethylcellulose in organic solvent (see table 3), by the following method:

1. Ethylcellulose powder was dissolved into acetone (purity >98%) at 35°C in a 500 mL beaker until completely dissolved; at various concentrations of ethylcellulose in acetone as indicated in table 3.

2. An equal volume of distilled water (water at room temperature, about 22°C) was quickly added into the ethylcellulose solution under strong stirring to precipitate the ethylcellulose into particles. 3. The solution was left to stir for another 10 minutes after which the acetone and some of the water were evaporated under low pressure in a rotary evaporator.

4. For all samples, a concentration of ethylcellulose in water of 0.5% (wt/wt) was obtained.

5. The measured z-average diameter of the ethylcellulose was as indicated in table 3; the corresponding volume weighted mean diameter d_4ι3 of the precipitated ethylcellulose particles was consequently between about 45 nanometer and about 200 nanometer.

6. Tartaric acid was added to the dispersion of ethylcellulose particles, to reach a pH of 3.

7. The dispersion of ethylcellulose particles was whipped with air, using a handheld aerolatte mixer (Radlett UK), for 4 minutes.

Table 3 Concentration ethylcellulose in solvent and influence on volume weighted particle diameter, zeta-potential and overrun of foam.

The average bubble diameter, determined by microscopy, was 400 micrometer for all examples. In all cases the stability of the foam was very good.

It is clearly shown in this example that samples 1 and 2, having z-average diameter of the ethylcellulose particles of 49 and 79 nanometer, and hence a volume weight average diameter (d_{4 3}) of about 44 nanometer and 71 nanometer, respectively, have the highest overruns. Example 4: Foamed food product stabilised by ethylcellulose particles

Hollandaise sauce stabilised by ethylcellulose particles was prepared by the following method:

1. Ethylcellulose powder was dissolved into acetone (purity >98%) at 35^CC in a 500 ml. beaker until completely dissolved; at a concentration of 1% by weight of ethylcellulose in acetone

2. An equal volume of distilled water (water at room temperature, about 22°C) was quickly added into the ethylcellulose solution under strong stirring to precipitate the ethylcellulose into particles, having a z-average particle size of about 130 nm. 3. The solution was left to stir for another 10 minutes after which the acetone and some of the water was evaporated under low pressure in a rotary evaporator

4. The concentration of ethylcellulose in water was set to 2% by weight.

5. 18 gram of the 2% ethylcellulose dispersion was added to 300 gram of a sauce Hollandaise (Knorr Garde d'Or Sauce Hollandaise, 1 L pack, Unilever Foodsolutions, Netherlands) with a pH of 4. The ethylcellulose concentration in the sauce was about 0.1 %.

6. The sauce with ethylcellulose particles was transferred into a standard stainless steel cream dispenser. The dispenser was fitted with a N₂O cream charger and the content was shaken for 10 seconds. The sauce was then sprayed onto a metal dish. 7. Foamability was compared to a system where 18 gram water (pH 4) was added to the sauce Hollandaise, in order to create the same dilution of the sauce Hollandaise. 8. The overrun of the sauce Hollandaise with ethylcellulose particles was 233% compared to 144% for the sauce Hollandaise with added water.

This experiment shows that sauce Hollandaise can be aerated, using ethylcellulose particles as stabiliser of the gas bubbles.

Example 5: Aerated full fat mayonnaise comprising ethylcellulose foam In this example, the bubble size evolution of a mayonnaise aerated with ethylcellulose foam will be compared to that of a mayonnaise which is aerated in the absence of ethylcellulose. An approximation of the bubble size evolution is probed by turbidimetry, using the method as described herein before. For an aerated mayonnaise the relative increase of the transport mean free path λ(t) at time t is plotted, as compared to the initial transport mean free path λ(0). The ratio λ(t)/ λ(0) is used as an approximation of the bubble size evolution, since mayonnaise contains a high concentration of oil droplets in addition to the air bubbles. Since the emulsion droplet size is known to constant over time, the increase in mean free path λ is considered to be caused by the bubble coarsening.

300 ml of above-mentioned 2.0 wt% ethylcellulose dispersion (similarly made as sample 2 of example 1) was placed into a 600 ml_ beaker. A small amount of solid tartaric acid powder was added to tune the pH of the dispersion from neutral to approximately 3. After stirring for 10 minutes, the dispersion was aerated by using a Silverson mixer for 2 minutes at about 9,000 rpm to a total volume of 500 mL (overrun 67%). The bubble diameter ranged from submicron to tens of microns as observed by optical microscopy. The prepared ethylcellulose foam was moved into a separation funnel to allow liquid drainage from the foam. After liquid drainage, 0.5 wt% xanthan solution was added, resulting into about 165 gram of ethylcellulose foam, which had a volume of 200 mL (Volume Percentage of air = 18%).

20 mL of the foam was mixed to 20 mL mayonnaise (Hellmans real ex Unilever, approximately 70% oil, density approximately 0.9 g/mL), which was degassed before the mixing. No volume decrease was observed during mixing and this resulted into an aerated mayonnaise comprising 9 vol% air. Approximately 20 mL of aerated mayonnaise was transferred into a glass tube for turbidimetry in order to probe the bubble size evolution over time.

Separately, approximately 500 mL of Hellmann's real mayonnaise was placed in the bowl of a Kenwood mixer, equipped with a whisk. The mayonnaise was whipped for 10 minutes, resulting into an air volume percentage of 15%. Approximately 20 mL of aerated mayonnaise was transferred into a glass tube for turbidimetry in order to probe the bubble size evolution over time. This aerated mayonnaise serves as a comparative example.

Figure 3 shows the relative increase in transport mean free path λ(t)/λ(O) of the invention product and the reference, measured over 9 days. Taking into account that much of the bubble size evolution is masked by the concentrated emulsion in the mayonnaise, still a significant difference in evolution can be observed between the two samples. The reference mayonnaise shows an increase in optical path length after about 0.1 day, whereas for the reference sample it takes at least 10 days to reach this bubble size increase. As from equation (2) follows that the bubble diameter d is proportional to the transport mean free path λ(t), this means that the the average bubble size increases fastest in the reference mayonnaise. The scattering of the values of mayonaise aerated with ethylcellulose foam is caused by disturbance by the oil droplets, nevertheless the trend can be clearly observed.

This result shows the superior stability to disproportionation of the aerated mayonnaise comprising ethylcellulose foam, when compared to the reference.

Example 6: Food product stabilised by ethylcellulose particles Whipped cream with half of its volume replaced by ethylcellulose dispersion was prepared by the following method:

1. Ethylcellulose powder was dissolved into acetone (purity >98%) at 35°C in a 500 mL beaker until completely dissolved; at a concentration of ethylcellulose in acetone of 1% by weight. 2. An equal volume of distilled water (water at room temperature, about 22°C) was quickly added into the ethylcellulose solution under strong stirring to precipitate the ethylcellulose into particles, having a z-average particle size of about 130 nm. 3. The solution was left to stir for another 10 minutes after which the acetone and some of the water was evaporated under low pressure in a rotary evaporator. 4. The concentration of ethylcellulose in water was set to 2%.

5. 50 gram of the 2% ethylcellulose dispersion from the previous step was added to 50 gram of a commercial liquid cream alternative (Solo Classique, 1 L pack, ex Unilever Foodsolutions Belgium, neutral pH, with a total (vegetable) fat level of about 33%). Subsequently 0.2g of MgCI₂ was then added to this mixture. 6. The mix was aerated in a standard kitchen mixer fitted with a whisk.

Overrun and stability were compared to systems consisting of 100 gram of whipped cream (same cream as in step 5) and of 50 gram liquid cream (same cream as in step 5) with 50 gram added water. Aeration conditions for these two systems were the same as in step 6. Results for overrun, yield stress and modulus of these systems are shown in table 4. The yield stress of a material is defined as the stress at which a material begins to flow. Prior to the yield point the material will deform elastically and will return to its original shape when the applied stress is removed. Once the yield point is passed some fraction of the deformation will be permanent and non-reversible. An elastic modulus (or storage modulus) is a measure of an object or substance's tendency to be deformed elastically when a force is applied to it. To determine these parameters, oscillation measurements were performed on a rheometer (TA Instruments AR1000, New Castle, DE, USA) fitted with a cone and 60 mm parallel plate geometry with a gap of 1000 micrometer. Measurements were done at 20⁰C with a frequency of 1 Hz between 0.1 to 100% strain.

Table 4 Overrun, yield stress and storage modulus of whipped cream, whipped cream with ethylcellulose and whipped cream with water

It is shown that the overrun that can be achieved by using ethylcellulose particles as stabiliser for gas bubbles is much higher than for the systems not containing these particles. The stability was also improved, as the cream sample with ethylcellulose showed the smallest increase of average bubble size diameter. The average bubble size evoluation was followed by determining the transport mean free path λ(t) in time, like in example 5. For the three samples, the average bubble size in the foams after a storage time of the whipped cream of about 2.8 hours (about 10,000 seconds) was:

^■ whipped cream 50 gram with ethylcellulose disperson 50 gram (according to the invention): 14.1%

■ whipped cream 50 gram with water 50 gram: 24.5% • standard whipped cream, 100 gram: 19.4%

Moreover, when comparing the yield stress and the modulus, the foam containing ethylcellulose particles has improved yield stress and modulus as compared to the standard whipped cream: in spite of dilution of the cream by a factor 2, the yield stress is the same as for the undiluted whipped cream. The modulus of the whipped cream with ethylcellulose is lower than the modulus of the standard whipped cream, nevertheless only about 38% lower, and not 50% as you would expect based on the two-fold dilution. Hence the conclusion can be made that the ethylcellulose particles lead to stabilisation of the foam.

Example 7: Frozen aerated products containing ethylcellulose particles at pH- neutral conditions

Three frozen aerated products (A, B, C) were produced where the surface active component principally used to stabilise the foam phase was ethylcellulose particles, produced in the same way as described in steps 1-3 of sample 2 in example 1 (1 wt% ethylcellulose in acetone). Two stock dispersions of ethylcellulose were used, one which was concentrated by evaporation to 2 wt% ethylcellulose and one where the water was evaporated to make a dispersion of 6 wt% ethylcellulose. The ethylcellulose was activated by adding MgCI₂ to a concentration of 50 mM in the premix. The air phase stability of the products was compared to that of a reference product produced with whey protein concentrate WPC80 as stabiliser (Product D). The formulations are given in table 5.

The general procedure for preparation of a frozen aerated product in a stirred pot apparatus is the following: a. add 80 mL premix, having a formulation as indicated in table 5; b. set the cooling bath to a temperature of -18⁰C; c. chill the stirred pot by circulating the cooling liquid for 10 seconds; d. stir 1 minute at 100 rpm; e. stir 1 minute at 1000 rpm; f. start cooling the vessel by circulating the cooling liquid; g. stir 3 minutes at 1000 rpm; h. stir at 300 rpm until the mix has obtained a temperature of -5°C; i. the aerated frozen product is then dosed into ca. 30 mL sample containers, overrun determined, and then cooled further on solid carbon dioxide before transferring to a -80⁰C freezer before further analysis. The stirred pot apparatus consisted of a cylindrical, vertically mounted, jacketed stainless steal vessel with internal proportions of height 105mm and diameter 72mm, which contained an agitator. The agitator consisted of a rectangular impeller (72mm x 41.5mm) which scrapes the edge of the vessel as it rotates and two semi-circular blades (60mm diameter) positioned at a 45° angle to the impeller.

Fresh samples of the frozen aerated products were stored at -80⁰C, at which temperature the texture of the frozen aerated products is stable, air bubbles do not change their average diameter.

The bubble stability of the samples was determined by storing the frozen aerated products at -10⁰C for 1 week, which is a test of product stability at an elevated storage temperature. This is called 'temperature abuse'. Subsequently the frozen aerated products were brought to -80⁰C again, in order to capture the structure. The average air bubble size can be determined by freeze fracturing samples of the frozen aerated products at -80⁰C, and observing the ice cream fractured surface by scanning electron microscopy, both before and after storage at -10⁰C for 1 week.

Product A, B and C (Figure 4): Aerated frozen products A, B, and C were prepared as explained above and this resulted into overruns indicated in table 5. The microstructure of products A, B, and C both fresh and after 1 week temperature abuse at -10°C are shown in Figure 4. The stabiliser in these products is ethylcellulose.

The fresh sample (stored at -80⁰C) shows an homogeneous dispersion of air bubbles of approximately 50 to 100 micrometer diameter (black and grey structures).

After keeping at -10⁰C for 1 week, a small number of large bubbles can be observed (which contain a larger volume of air), indicating a limited extent of coarsening. Also a population of small bubbles (<20 micrometer) still can be observed as well (black and grey structures), which have survived the temperature-abuse regime. These bubbles have been stable against Ostwald ripening.

Closer observation of these small bubbles in product B shows the presence of a structured air/water interface (see Figure 5) that consists of adsorbed ethylcellulose particles. This corrugated structure at the air-water interface is typical for particle-laden interfaces Product D (Figure 6): Aerated frozen product D was prepared in a similar manner as products A, B and C and with overrun stated in table 5. This product serves as reference example using a standard ingredient known in the art for stabilising air bubbles in aerated frozen products. At -8O⁰C (fresh), a homogeneous dispersion of air bubbles could be observed, having an average diameter of about 100 micrometer. The overrun is higher than in case of products A, B, C.

After keeping at -10⁰C during 1 week, the product showed strong coarsening of the microstructure. Air bubbles have grown much larger than 100 micrometer and the growth is accompanied by coalescence and channel formation. No population of small bubbles is remaining after temperature abuse, indicating inferior air stabilization functionality compared to products A, B and C, which contain ethylcellulose in the presence of 50 mM MgCI₂. This shows that Ostwald ripening has occurred, and that the small bubbles are not stabilised by the WPC80, like they are in products A, B, C by ethylcellulose.

In conclusion, the experiment illustrates that ethylcellulose offers improved air-phase stability upon temperature abuse, compared to the reference system of whey protein.

Example 8: Frozen aerated products containing ethylcellulose particles at acidic condition

In this example two frozen aerated products E and F were produced, where the surface active component principally used to stabilise the foam phase is ethylcellulose particles, produced as described in steps 1-3 of sample 2 in example 1 (1 wt% ethylcellulose in acetone). A stock dispersion of ethylcellulose was used which was concentrated by evaporation to 6 wt% ethylcellulose. The ethylcellulose is activated by adding tartaric acid to a pH of 3. The air phase stability of the product is compared to that of an acidified reference product produced with skim milk powder (SMP).

The general procedure for preparation of the frozen aerated product in a stirred pot apparatus is the same as indicated in example 7.

Two samples of frozen aerated product were produced, as indicated in table 6. Both products were acidified after all other ingredients were mixed by adding tartaric acid in the case of ethylcellulose or 1 N HCI in the case of SMP. Table 6 Compositions of frozen aerated products

Product E: This product was prepared as explained above and this resulted into an overrun stated in table 6. The microstructure of Product E, both fresh and after 1 week temperature abuse at -10⁰C, was observed by electron microscopy, and this showed a homogeneous dispersion of air bubbles can be observed, with an average diameter of about 25 to 100 micrometer.. The stabiliser in this product is ethylcellulose. At -8O⁰C (fresh),

After keeping at -10⁰C for 1 week, a smaller number of large bubbles (200- 300 micrometer diameter) can be observed, indicating a limited extent of coarsening. A population of small bubbles (<20 micrometer) can be observed as well, which have survived the temperature abuse regime, and which have not shrunk due to Ostwald ripening. Closer observation of these small bubbles shows the presence of a structured air/water interface (Figure 7), showing stabilisation of the bubbles by ethylcellulose.

Product F: This product was prepared as explained above and this resulted into an overrun stated in table 6. This product serves as comparative example using a standard ingredient known in the art for stabilising air bubbles in aerated frozen products. The microstructure of Product F, both fresh and after 1 week temperature abuse at -10⁰C, was observed by electron microscopy. At -80⁰C (fresh), a homogeneous dispersion of air bubbles could be observed, having an average diameter of about 50 to 100 micrometer. After keeping at -1O⁰C during 1 week, the product showed strong coarsening of the microstructure. Air bubbles have grown much larger than 100 micrometer and the growth is accompanied by coalescence and channel formation. The larger bubbles appear bigger than those in Product B. No population of small bubbles is remaining after temperature abuse, indicating inferior air stabilization compared to product A, which contains ethylcellulose particles at pH 3. In addition, the interfaces appeared much smoother than that of the ethylcellulose- bubbles. This shows that the SMP does not stabilise the bubbles to survive Ostwald ripening.

In conclusion, the experiment illustrates that ethylcellulose offers improved air-phase stability upon temperature abuse, compared to the reference system. The small bubbles can survive a temperature abuse regime and show only limited Ostwald ripening, as being stabilised by ethylcellulose.

Comparative example 9: Food product stabilised by zein particles

Foams stabilised by zein particles were created:

1. Zein powder was dissolved in 100 ml ethanol (with a purity of >99%), at 35°C in a 500 ml_ beaker until completely dissolved; at a concentration of zein in ethanol of 1 wt%. 2. An equal volume of distilled water was quickly added into the zein solution under strong stirring to precipitate the zein into particles.

3. The solution was left to stir for another 10 minutes after which the acetone and some of the water were evaporated under low pressure in a rotary evaporator, until a final concentration of zein in water of 2% was obtained; the dispersion was yellow coloured.

4. The z-average particle size of the zein particles was 426 nanometer.

5. The dispersion was diluted to a zein concentration of 1%.

6. Magnesium chloride (MgCI₂) was added to a concentration of 21 millimolar, and the zeta-potential of the zein colloidal particles was below 25 millivolt. 7. The dispersion was whipped with air, using a Kenwood Chef mixer for 10 minutes at maximum speed; 8. The foam was left to drain for 2 hours.

The foam obtained using zein particles as stabiliser was not stable, as bubbles collapsed already during the draining step. This bubble collapse was observed by listening to the created foam: small ticks could be heard, caused by expanding and breaking air bubbles. The foam was not stable enough to be mixed with a food product like mayonnaise.

Claims

1. A method for preparation of an aqueous foam, comprising the steps: a) dissolving ethylcellulose in an organic solvent which is miscible in water; b) addition of water to the mixture of step a), wherein the amount of water is at a weight ratio between 10:1 and 1 :2 based on the organic solvent; c) evaporating organic solvent and water to a concentration of ethylcellulose of at least 1 % by weight; d) addition of an acid to a pH of 4 or lower, or addition of a water-soluble salt to an ionic strength of at least 20 millimolar; or addition of a combination of acid and water-soluble salt; e) introduction of gas bubbles to the composition of step d) to create a foam.

2. A method according to claim 1 , wherein in step a) the concentration of ethylcellulose is between 0.1 and 6% by weight.

3. A method according to claim 1 or 2, wherein in step a) the organic solvent comprises acetone or ethanol or a combination of these.

4. A method according to any of claims 1 to 3, wherein in step b) ethylcellulose particles precipitate having a volume weighted mean diameter between 30 and 90 nanometer.

5. A method according to any of claims 1 to 4, wherein in step d) the acid comprises hydrochloric acid, tartaric acid, acetic acid, or citric acid, or any combination of these acids, and the salt comprises NaCI₁ KCI, MgCI₂ or CaCI₂ Or any combination of these salts.

6. A method according to any of claims 1 to 5, wherein at least 50% of the gas bubbles in the foam created in step e) has a diameter smaller than 200 micrometer.

7. A method for preparation of an aerated food product, comprising the steps: a) dissolving ethylcellulose in an organic solvent which is miscible in water; b) addition of water to the mixture of step a), wherein the amount of water is at a weight ratio between 10:1 and 1 :2 based on the organic solvent; c) evaporating organic solvent and water to a concentration of ethylcellulose of at least 1 % by weight; d) addition of an acid to a pH of 4 or lower, or addition of a water-soluble salt to an ionic strength of at least 20 millimolar; or addition of an acid and a water-soluble salt; e) introduction of gas bubbles to the composition of step d) to create a foam; f) mixing the foam from step e) with one or more food ingredients; g) optionally mixing the composition from step f) with one or more other food ingredients.

8. A method according to claim 7, wherein the composition from step f) has an overrun of at least 5%.

9. An aqueous foam composition comprising ethylcellulose particles having a volume weighted mean diameter between 30 and 90 nanometer, wherein the foam has an overrun of at least 50%.

10. An aqueous foam composition according to claim 9, wherein the ethylcellulose particles have a volume weighted mean diameter between 50 and 70 nanometer.

11. An aqueous foam composition according to claim 9 or 10, wherein the absolute value of the zeta-potential of the ethylcellulose particles is below 25 millivolt.

12. An aqueous foam composition according to any of claims 9 to 11 , wherein at least 50% of the number of gas bubbles has a diameter smaller than 200 micrometer.

13. An ethylcellulose particle, having a diameter between 30 and 90 nanometer, wherein the absolute, value of the zeta-potential of the particle is below 25 millivolt.

14. A food composition comprising an aqueous foam according to any of claims 9 to 12, wherein the food composition has an overrun of at least 1%.

15. Use of ethylcellulose in the form of particles having a volume weighted mean diameter between 30 and 90 nanometer to stabilise foams.

16. Use of ethylcellulose in the form of particles having a volume weighted mean diameter between 30 and 90 nanometer in aerated food products.