The present invention relates to a method for preparation of aerated anhydrous fat- based food product or a fat-continuous food product such as chocolate. The present invention further relates to aerated foods obtainable by such methods.

Fat-continuous products, such as chocolate, butter, margarine, ghee, oils, shortening, peanut butter, chocolate spreads and the like are generally unaerated. However, they may also be aerated for various purposes, for example to increase softness and / or spreadability, to alter texture or to change the visual appearance, e.g. by whitening or opacifying. A well-known example is aerated chocolate, such as Aero™. Unlike water- continuous products, such as mousse or ice cream, it is difficult to aerate a fat- continuous food product to high overruns by simply whipping in the presence of a surfactant because both fat and air are hydrophobic.

Chocolate is usually aerated by a process wherein pressurized gas, for example carbon dioxide, is mixed into the molten chocolate. The pressure is then released and the gas bubbles expand, thereby forming an aerated product. Finally, the aerated chocolate is cooled in order to solidify the fat and thereby retain the aerated structure. This process has been known for many years, for example from GB 459,583 and EP 322 952 A2.

Whipped butter is generally made by whipping air into softened butter at warm temperatures, and then cooling it. US 2,937,093 discloses a process for manufacturing whipped margarine. This process comprises combining liquid margarine with an inert gas (e.g. nitrogen), cooling the mixture, agitating the cooled mixture under pressure to produce a flowable mass, and then releasing the pressure.

EP 285 198 A2 discloses food products such as margarine or shortening comprising a continuous fat phase and a dispersed gas phase, which exhibit an improved spattering behaviour when used for frying. The product is produced on a votator line and the gas is incorporated in the composition near the beginning of the line, while the composition still comprises essentially no crystallized fat. 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 5,202,147 discloses a method of aerating peanut butter comprising subjecting a molten mass of peanut butter to pressures of from about 200 to about 500 psi, rapidly deep chilling the mass to a temperature of from about 35° to about 50° F, injecting inert gas into the molten mass, and then passing the chilled mass through a narrow orifice.

Non-prepublished patent application with application no. EP08167499 discloses aerated fat-continuous food products containing hydrophobins.

WO 2008/019865 A1 discloses aqueous foams and food products containing these. The gas bubbles in the foam are stabilised by interfacially-active particles, 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.

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. From a few graphs in this publication it can be derived that 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.

WO 2007/060462 A1 discloses dried 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. In a further step the latex particles may be sintered, in order to create a more stable foam composition. Such a sintering process is usually used to make dry bubbles, inside the foam fragments, fused together into a coherent mass. This may lead to difficulties when mixing the dried foam with a composition in order to create an aerated composition. The inventors of this patent application have published similar latex stabilized foams (Fujii et al., J. Am. Chem. Soc. 2006, 128, 7882-7886). These foams are also dried by a sintering process at 105 ⁰ C in an oven.

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.

WO 2007/038745 A1 discloses cream compositions containing hydroxypropyl methylcellulose (HPMC), hydroxypropyl cellulose (HPC), methyl hydroxyethyl cellulose (MHEC), methyl cellulose (MC) or ethyl cellulose (EC), at a concentration up to about 0.15%, and water-soluble or water-swel table 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.

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.

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. - A -

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 acetone 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 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. Moreover, some systems have the disadvantage that several compounds are required to stabilise the foams which do not provide nutritional value. Moreover such compounds may be expensive, or not compatible for food use.

Additionally for anhydrous fat-based food compositions or fat-continuous food compositions such processes are complex and inconvenient, and moreover often result in relatively low overruns and/or large air bubbles. Moreover, aeration of an anhydrous fat-based food composition or a fat-continuous food composition by a foam is difficult in that the foam is often based on an aqueous composition, which is difficult to mix with the fat-based food product. Thus there remains a need for a simple and improved method for producing aerated anhydrous fat-based food compositions or fat-continuous food compositions, and in particular processes which results in high overruns and uniformly sized, small gas bubbles.

Hence there is a need for a method for efficiently producing aerated anhydrous fat- based food composition or aerated fat-continuous food compositions by creation of a foam, where the foam remains stable, while the stabiliser preferably is a cheap and commonly available raw material. Preferably the foams have high overruns and relatively small, uniformely sized gas bubbles. Moreover the use of only a low concentration of stabiliser in the food product would be advantageous. Moreover 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 the high caloric value of food products which normally have a smooth and creamy mouthfeel. We have now found that stable aerated anhydrous fat-based foods or aerated fat- continuous foods can be produced containing colloidal solid particles having a diameter between 30 and 1000 nanometer as a foam stabiliser. These foams can be mixed with an anhydrous fat-based food composition or a fat-continuous food composition. Preferably the colloidal solid particles comprise ethylcellulose particles. Therewith stable aerated anhydrous fat-based foods or aerated fat-continuous foods can be made.

Accordingly in a first aspect the present invention provides a method for preparation of an aerated anhydrous fat-based food product or a fat-continuous food product, comprising the steps: a) dispersing water-insoluble solid particles having a volume weighted mean diameter between 30 and 1000 nanometer in an aqueous composition; b) introducing gas bubbles into the composition of step a) to create a foam having an overrun of at least 1%; c) mixing the foam from step b) into an anhydrous fat-based food composition or a fat-continuous food composition;

In a second aspect the present invention provides a method for preparation of an aerated anhydrous fat-based food product or a fat-continuous 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 an anhydrous fat-based food composition or a fat-continuous food composition. In a third aspect the present invention provides an aerated anhydrous fat-based food product or an aerated fat-continuous food product obtainable by a method according to the first or second aspect of the invention, wherein the food product has an overrun of at least 1 %.

In a fourth aspect the present invention provides an aerated anhydrous fat-based food product or an aerated fat-continuous food product comprising gas bubbles stabilised by solid particles having a volume weighted mean diameter between 30 and 1000 nanometer, wherein the food product has an overrun of at least 1%.

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. Definitions and descriptions of various terms and techniques used in fat-continuous food systems are given in Bailey's Industrial Oil and Fat Products, 6 ^th Edition, Shahidi and Fereidoon (eds.), vol. 1-6, 2005, John Wiley & Sons.

All percentages, unless otherwise stated, refer to the percentage by weight, with the exception of percentages cited in relation to the overrun. The term 'wt%' relates to percentage by weight of the total composition, unless stated otherwise.

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 same 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 product, 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 . _nnn . overrun = - x 100% 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.

Method for preparation of an aerated anhydrous fat-based food product or a fat- continuous food product The food product according to the invention is an anhydrous fat-based food composition or a fat-continuous food composition, i.e. the main component in the coating beside solid matter such as e.g. sugar and/or not-fat cocoa solids, is fat, not water. The food product preferably has a continuous fat phase. Preferably, the water content of the food product is less than 5 wt%. More preferably it is less than 3 wt%, especially less than 2 wt%. Preferably during manufacturing the food product contains less than about 0.5 wt% moisture but during storage of the product, some moisture may migrate e.g. from the gel part to the coating.

Edible fats and oils are generally triglycerides, i.e. triesters of glycerol and fatty acids. The term 'fat' includes oils that are liquid at room temperature, as well as fats that are solid.

The fat continuous product is preferably a food product, such as chocolate, chocolate analogues, chocolate spread, butter, ghee, margarines / spreads, cooking / frying oils, shortenings, peanut butter and the like. Fats typically used in food products include coconut oil, palm oil, palm kernel oil, cocoa butter, milk fat, sunflower oil, safflower oil, olive oil, linseed oil, soybean oil, rapeseed oil, canola oil, walnut oil, corn oil, grape seed oil, sesame oil, wheat germ oil, cottonseed oil, ground nut oil, fish oil, almond oil, perilla oil, water melon seed oil, rice oil, peanut oil, pistachio oil, hazelnut oil, maize oil and mixtures, fractions or hydrogenates thereof.

The food product preferably comprises chocolate or a chocolate analogue. The term 'chocolate' as used herein includes dark chocolate, white chocolate, and milk chocolate; the term 'chocolate analogue' means chocolate-like fat-based confectionery compositions made with fats other than cocoa butter (for example cocoa butter equivalents, coconut oil or other vegetable oils). Chocolate and chocolate analogues may contain cocoa powder, milk solids, sugar or other sweeteners and flavourings. The chocolate may also be flavoured chocolate, e.g. chocolate containing some strawberry or hazelnut flavour. Chocolate and materials similar to chocolate have a continuous fat phase. The food product may also be a chocolate analogue. Such compositions may include as a partial or complete replacer of cocoa butter, cocoa butter equivalent or lauric or non-lauric cocoa butter replacer. The food product may for example include pieces of nuts, raisins, biscuits and/or dried fruit or the like. However, any materials included in the coating should have a low moisture content because the anhydrous character of the food product should not be affected.

Food products as described above are well known in the confectionery industry and they can be applied in the present invention. Other anhydrous fat-based food product or fat-continuous food products may also be applied for the present invention. If the food product according to the invention comprises chocolate or a chocolate replacer composition, then preferably the food product has a fat content of 20-50 wt%. The fat contained in the food product preferably has a relatively high solid fat content at 15 ^° C. The solid fat content can suitably be measured by NMR as is commonly applied in the confectionery industry. The solid fat content at 15°C preferably is at least 50%, more preferably it is at least 60%.

Preferably, the food product comprises 25-40 wt% fat, 35-60 wt% sugar, optionally up to 25 wt% not-fat cocoa solids, optionally up to 25 wt% not-fat milk solids and optionally up to 5 wt% other ingredients e.g. lecithin, vanilla and/or hazelnut oil. Cocoa solids may be included in the coating in the form of e.g. cocoa powder or cocoa mass. Cocoa mass, or cocoa liquor, comprises cocoa butter and not-fat cocoa solids in a weight ratio of about 1 :1. An example of a composition that can be used as food product is plain chocolate consisting of about 40 wt% cocoa mass, 12 wt% cocoa butter, 48 wt% sugar and 0.4 wt% lecithin.

The terms 'margarine' and 'spread' refer to the numerous different types of butter substitutes consisting of water-in-oil emulsions made from vegetable and / or animal fats. These food products are fat-continuous food products, not anhydrous fat-based food products. In addition to the emulsion, margarines and spreads may contain milk protein, salt, emulsifiers, colours, flavourings, etc. These terms also cover blends of margarine and butter, and fat-continuous low fat spreads which typically contain less than 40 wt% fat.

Shortening is an edible fat product which typically contains close to 100% fat and is prepared from animal and/or vegetable oils. Shortening is used in frying, cooking, baking, and as an ingredient in fillings, icings, and other confectionery items.

In a first aspect the present invention provides a method for preparation of an aerated anhydrous fat-based food product or a fat-continuous food product, comprising the steps: a) dispersing water-insoluble solid particles having a volume weighted mean diameter between 30 and 1000 nanometer in an aqueous composition; b) introducing gas bubbles into the composition of step a) to create a foam having an overrun of at least 1%; c) mixing the foam from step b) into an anhydrous fat-based food composition or a fat-continuous food composition.

All preferred embodiments of the first aspect of the invention as disclosed below, may be combined to give preferred embodiments of the method for preparation of the aerated food products of the invention.

Two further optional steps may be performed subsequently to the steps indicated above: d) optionally mixing the composition from step c) with one or more other food ingredients; e) optionally cooling the mixed composition.

The fat-continuous composition in step c) must be sufficiently soft, or liquid, so that the gas can be mixed in to form a foam. Optional cooling then solidifies the fat-continuous composition.

The optional cooling step e) may be performed during step c), so mixing and cooling take place simultaneously in a single step.

In addition to the foam stabiliser and fat or oil, the aerated food products of the invention may contain other ingredients conventionally found in food products, such as sugars, salt, proteins, fruit and / or vegetable material, emulsifiers, stabilisers, preservatives, colours, flavours and acids.

The solid particles in step a) have a volume weighted mean diameter between 30 and 1000 nanometer, preferably between 30 and 500 nanometer, more preferred between 50 and 500 nanometer, more preferred between 30 and 300 nanometer, even more preferred between 50 and 300 nanometer, more preferred between 60 and 300 nanometer, and even more preferred between 70 and 300 nanometer. Alternatively, in another preferred embodiment the solid particles have a volume weighted mean diameter between 50 and 200 nanometer. In another alternative most preferred embodiment the solid 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 solid particles is between 100 and 200 nanometer, or even between 100 and 150 nanometer. Alternatively preferably the solid 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 solid 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 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.

The solid particles are water-insoluble, and the concentration of these particles in the dispersion in step a) is preferably between 0.1 and 20% by weight, more preferred between 0.5 and 10% by weight, most preferred between 0.5 and 5% by weight. Preferably the water-level of the foam composition created is at least 10% by weight of the foam composition.

The dispersion of particles is an aqueous dispersion, or a dispersion of particles in a mixture of water and organic solvents. Preferred organic solvents are for example ethanol, acetone, isopropanol, and tetrahydrofuran. For food use, the solvent has to be food-grade and compatible for food use. If an organic solvent is present in step a), after foaming removal of the organic solvent can be done by evaporation or any other suitable method. The term water-insoluble solid particles is understood to have its common meaning, such that the particles do not dissolve in water, or wherein at most 0.1 wt% of a compound dissolves in water when the compound is mixed with water at room temperature, atmospheric pressure and neutral pH. A preferred stabiliser for foams used in the first aspect of the present invention is ethylcellulose. The general structural formula of ethylcellulose is:

The degree of substitution of the ethylcellulose preferably 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 preferably 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.

Alternatively, the solid particles can be made of a lipid material, wherein the lipid material preferably is a wax. 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 another preferred embodiment the solid particles can be made of a lipid material, wherein the lipid material comprises plant sterols or fatty acids/fatty acid esters. Plant sterols (also called phytosterols) are a group of steroid alcohols, phytochemicals naturally occurring in plants. At room temperature they are white powders with mild, characteristic odor, insoluble in water and soluble in alcohols. Plant sterols can be transformed into microparticles by inducing the precipitation of a plant sterol solution containing via solvent change during stirring. Herein, the particles can be with various shapes such as spherical, rod-like shape and platelet shape.

Preferably in step a) the aqueous composition further comprises a mixture of more than two types of aforementioned particles, thus in step a) the solid particles may comprise ethylcellulose and/or a lipid material. For example, the foam could be stabilised by a mixture of ethylcellulose particles and shellac wax particles.

In a preferred embodiment, in step a) the aqueous composition 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 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 or platelet-like.

The concentration of the waxy material in step a), if present, preferably ranges from 0.01 % to 10% by weight.

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 another preferred embodiment, after step b), 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 in step a), if present, ranges from 0.001 wt% to 5.0 wt%, preferably from 0.05 wt% to 1.0 wt%.

In another preferred embodiment in step a) the aqueous composition further comprises a water-insoluble thickening agent. Or alternatively in another preferred embodiment, after step b) 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. Such fibres have the advantage that they are very biodegradable, which is favourable for the environment. 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 wt%, more preferred from 0.01 to 5% by weight, most preferred from 0.05 to 1.0 wt%.

The food product created in step b) has an overrun of at least 1 %. Preferably the food product has an overrun of at least 5%, more preferably at least 10%, most preferably at least 20%. Preferably the food product has an overrun of at most 200%, more preferred at most 150%, more preferably at most 120%, most preferably at most 100%.

In one preferred embodiment, the food product is an aerated butter, margarine or spread, in which case the overrun is preferably from 5 to 50%, more preferably from 10 to 20%, for example about 15%. In another embodiment the food product is a cooking oil which is aerated in order to reduce spattering, in which case the overrun is preferably less than 10%, typically about 5%.

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.

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 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.

The temperature at which step b) is performed usually is between 0 and 100 ⁰ C, more preferably between 15 and 80 ⁰ C, most preferred from 20 to 60°C. At relatively high temperatures (like for example 60 to 80 ⁰ C), bubbles may become bigger upon foaming than at relatively low temperatures. Upon a subsequent optional cooling step, bubbles shrink again, due to the shrinking gas volume with lower temperatures. This leads to more closely packed particles on the interface of the bubbles, ultimately leading to more robust foams. Moreover at higher temperature the particles tend to stick more to each other, leading to more robust foams.

In a preferred embodiment the foam from step b) is heated in a closed vessel to a temperature at which the particles partly or totally fuse prior to mixing the foam from step b) into the food composition in step c). It is important that the vessel is closed and that the pressure in the vessel can increase, as otherwise the bubbles will expand and ultimately collapse. Using a closed vessel also has the result that the foam remains aqueous and is not dried during the heating step. In the context of the present invention a closed vessel may also emcompass a continuous pasteurisation or sterilisation unit, which are commonly used for example in the dairy industry, and which act under a pressure higher than atmospheric pressure.

The temperature and time required will depend on the type of particle, and can be determined by the skilled person. Preferably the heating is done at a temperature between 40 and 160°C, more preferred between 80 and 16O ⁰ C, even more preferred between 90 and 15O ⁰ C, and most preferred between 100 and 140 ⁰ C. The heating time is dependent on the heating temperature and may range from 10 minutes to 4 hours, like for example 30 minutes, 1 hour, 2 hours, 3 hours. If the heating temperature is high, then the corresponding heating time is short and vice versa. If the foam is heated too long, the foam may collapse due to collapsing bubbles. The heating may lead to a more stable foam, because the particles partly or totally fuse forming a relatively robust shell around the gas bubbles. As an advantage, the foam remains aqueous, meaning that it is not dried during this heating step, and consequently remains soft and can easily be mixed with the fat continuous or anhydrous food product.

The optional heating step of the foams is performed, in order to obtain partly or totally fusing particles at the gas-water interface of single bubbles, rather than particles partly or totally fusing on the interface of multiple bubbles, which would lead to a solid foam as the bubbles will form a solid conglomerate. Alternatively, by the method according to the invention, single bubbles are created, having a robust shell that captures the gas bubbles, but wherein the foam is still flexible. During this heating step, and by the foam remaining aqueous, aggregation of bubbles can be avoided in order to keep the bubbles separated from each other during the optional heating. The foam remains an aqueous foam in this manner, and the bubbles can be redispersed and separated from each other after the optional heat treatment, for example when being mixed with one or more food ingredients. As opposed to sintering, the particles on the interfaces of different bubbles do not fuse, and remain single bubbles. During the heating step, particles are softened and partly or totally fuse, without collapse of bubbles.

If in a preferred embodiment a lipid material is present in step a) of the method according to the first aspect of the invention, this lipid material may melt in the optional heating step prior to step c) and be incorporated in the shell around the bubbles. The lipid material may be used to 'glue' the solid particles located at the interface when the wax melts at a lower temperature. Therewith the heating temperature can be reduced in the optional heating step before step c).

If in a preferred embodiment a water-soluble thickening agent or an aqueous solution or dispersion of a water-soluble thickening agent (such as xanthan gum or other thickening agents as indicated before) is mixed with the foam obtained in step b), then the viscosity of the continuous aqueous phase will increase. The addition of a water- soluble thickening agent may be used to prevent the particle stabilised bubbles from aggregation during the optional heating step. Consequently, it may prevent the bubbles from coalescing and agglomerating during the optional heating step, which could induce the loss of foam volume. This may lead to easier dispersion of the foam into a fat-continuous or fat-based anhydrous composition, therewith possibly creating homogeneously aerated food products having an attractive texture and appearance.

In a preferred embodiment a water-insoluble thickening agent (such as citrus fibres or other fibres) is present in step a). Without wishing to be limited by theory, it is believed that the water-insoluble thickening agent keeps the bubbles and the particles on the interfaces of separate bubbles separated by forming a barrier in between the interfaces of bubbles. Moreover it also increases the viscosity of the continuous phase. Therewith the addition of a water-soluble thickening agent may be used to prevent the particle stabilised bubbles from aggregation during the optional heating step prior to step c). Consequently, it may prevent the bubbles from coalescing and agglomerating during the optional heating step, which could induce the loss of foam volume. This may lead to easier dispersion of the foam into a composition, therewith possibly creating homogeneously aerated food products having an attractive texture and appearance.

In a variant of this aspect of the invention, the process for producing an aerated product according to the first aspect of the invention comprises: a) forming an oil-in-water emulsion; b) cooling the emulsion while applying shear so that phase inversion of the emulsion takes place; and c) aerating the emulsion during step a) and/or step b).

Preferred method for preparation of an aerated anhydrous fat-based food product or a fat-continuous food product, comprising ethylcellulose In a preferred embodiment of the first aspect of the invention, the invention provides in a second aspect a method for preparation of an aerated anhydrous fat-based food product or a fat-continuous 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 an anhydrous fat-based food composition or a fat-continuous food composition.

Optionally the previous steps may be followed by one or more of the following steps: g) optionally mixing the composition from step f) with one or more other food ingredients; h) optionally cooling the mixed composition.

In step a) of this preferred 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 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 second aspect of the invention, is based on the purity of the organic solvent. The temperature in step a) is preferably between 10 and 60°C, more preferably between 25 and 40 ⁰ C. 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 diameter between 50 and 500 nanometer, more preferred 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 solid particles have a volume weighted mean diameter between 50 and 200 nanometer. In another alternative most preferred embodiment the solid 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 is between 100 and 200 nanometer, or even between 100 and 150 nanometer. Alternatively preferably the solid 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 solid 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 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 6O ⁰ C, more preferably between 25 and 40 ⁰ C.

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, MgCI ₂ , or CaCI ₂ , 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 this preferred method, 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 below 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 a zeta-potential of the ethylcellulose particles below 25 millivolt, preferably below 20 millivolt, more preferred below 15 millivolt.

Preferably the zeta-potential of the ethylcellulose particles obtained from step d) has an absolute value below 25 millivolt, preferably below 20 millivolt, more preferred below 15 millivolt, leading to stable foams.

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 20%, preferably 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. The temperature at which step e) is performed usually is between 0 and 100 ⁰ C, more preferably between 15 and 80 ⁰ C, most preferred from 20 to 40°C.

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, N ₂ O), and carbon dioxide.

In step e) any stirrer or technique which produces small enough gas bubbles can be used (e.g. Silverson, Ultraturrax, Kenwood kitchen mixer, Ross Mill). Also the aeration methods indicated later herein may be suitable methods. 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.

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.

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 this preferred method suitably has a concentration of ethylcellulose of at least 0.01% by weight, and at most 20% by weight of the foam composition, more 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 of this preferred method according to the second aspect of the invention, in step e) 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 e), 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.

Preferred aspects of the wax in the context of this preferred method are also applicable to the second aspect of the invention.

Preferably the aerated food product prepared by the method according to 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, 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%.

Preferred aspects of the water-soluble thickening agent in the context of the first aspect of the invention are also applicable to the second aspect of the invention.

In a preferred embodiment, in step e) 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.

The concentration of the water-insoluble thickening agent in step e), if present, preferably ranges from 0.01 to 10 % by weight, more preferably 0.05 to 1.0 % by weight.

Preferred aspects of the water-insoluble thickening agent in the context of the first aspect of the invention are also applicable to the second aspect of the invention.

Preferably in this preferred method the foam from step e) is heated in a closed vessel at a temperature between 60 and 150°C during a period between 10 minutes and 5 hours, prior to mixing the foam from into a fat-continuous food composition in step f). Preferably the temperature in step f) is between 80 and 150 ⁰ C, or 100 and 150 ⁰ C, and most preferred between 120 and 140 ⁰ C. The heating time is dependent on the heating temperature and may range from 10 minutes to 4 hours, like for example 30 minutes, 1 hour, 2 hours, 3 hours. The time required is dependent on the temperature: at a high temperature, the required time is shorter than at a lower temperature, and can be determined by the skilled person. It is important that the vessel is closed and that the pressure in the vessel can increase, as otherwise the bubbles will expand and ultimately collapse.

If in a preferred embodiment a waxy material is present in the composition in step e) of the method according to the second aspect of the invention, this waxy material may melt in this optional heating step and be incorporated in the shell around the bubbles. The wax may be used to 'glue' the solid particles located at the interface when the wax melts at a lower temperature. Therewith the heating temperature can be reduced.

If in a preferred embodiment a water-soluble thickening agent or an aqueous solution or dispersion of a water-soluble thickening agent (such as xanthan gum .or other thickening agents as indicated before) is mixed with the foam obtained in step e) of the method according to the second aspect of the invention, then the viscosity of the continuous aqueous phase will increase. The addition of a water-soluble thickening agent may be used to prevent the particle stabilised bubbles from aggregation during the optional heating step. Consequently, it may prevent the bubbles from coalescing and agglomerating during the optional heating, which could induce the loss of foam volume. This may lead to easier dispersion of the foam into a composition, therewith possibly creating homogeneously aerated food products having an attractive texture and appearance.

In a preferred embodiment a water-insoluble thickening agent (such as citrus fibres or other fibres) is present in step a) of the method according to the second aspect of the invention. Without wishing to be limited by theory, it is believed that the water-insoluble thickening agent keeps the bubbles and the particles on the interfaces of separate bubbles separated by forming a barrier in between the interfaces of bubbles. Moreover it also increases the viscosity of the continuous phase. Therewith the addition of a water-soluble thickening agent may be used to prevent the particle stabilised bubbles from aggregation during the optional heating. Consequently, it may prevent the bubbles from coalescing and agglomerating during heating, which could induce the loss of foam volume. This may lead to easier dispersion of the foam into a composition, therewith possibly creating homogeneously aerated food products having an attractive texture and appearance.

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.

Preferred embodiments of the first and second aspects of the invention

The following preferred embodiments are applicable to both the first and second aspects of the invention. In the methods according to the first and second aspects of the invention, gas bubbles are introduced to the composition to create a foam, that preferably has an overrun of at least 20%. 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 are preferably gases which are suitable for use in foods, such as air, nitrogen, nitrous oxide (laughing gas, N ₂ O), and carbon dioxide. 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 particle 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 size 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 size (at a given total fixed foam volume).

At a given particle concentration (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 particle size and bubble size is preferably larger than 1 :5, more preferably larger than 1 :10.

Suitably the average size 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 size smaller than 200 micrometer, more preferably at least 50% of the number of gas bubbles in the foam has a size 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.

In general it holds that the smaller the particles in step a), 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 the methods according to the first and second aspects of the invention suitably has a concentration of particles of at least 0.01% by weight, and at most 20% by weight of the foam composition, more 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.

Aerated food products obtainable by the method of the first or second aspect of the invention

In a third aspect the invention provides an aerated anhydrous fat-based food product or an aerated fat-continuous food product obtainable by a method according to the first or second aspect of the invention, wherein the food product has an overrun of at least 1%.

The aerated food product preferably has an overrun of at least 5%, more preferably at least 10%, most preferably at least 20%. Preferably the food product has an overrun of at most 200%, more preferred 150%, even more preferably at most 120%, most preferably at most 100%. In one embodiment, the food product is an aerated butter, margarine or spread, in which case the overrun is preferably from 5 to 50%, more preferably from 10 to 20%, for example about 15%. In another embodiment the food product is a cooking oil which is aerated in order to reduce spattering, in which case the overrun is preferably less than 10%, typically about 5%.

Preferably the food product is selected from chocolate, chocolate analogue, butter, ghee, margarine, low fat spreads, cooking fats and oils, shortening, peanut butter, and chocolate spread. Most preferred the food product is chocolate or chocolate analogue. The preferred chocolate or chocolate analogue may be consumed as such, or may be used as an ingredient of another food product, such as chocolate chunks in ice cream or dessert, or similar product. It may also be used as a coating for ice cream. Preferably the food product comprises gas bubbles, wherein at least 50% of the number of gas bubbles has a size smaller than 200 micrometer. More preferred, at least 50% of the number of gas bubbles has a size smaller than 100 micrometer. Even more preferred at least 75% of the number of gas bubbles has a size smaller than 75 micrometer.

Preferably the food product according to the third aspect of the invention comprises ethylcellulose particles as solid particles. All preferred embodiments of the second aspect of the invention may be applicable here as well, mutatis mutandis. Preferably these ethylcellulose particles have a volume weighted mean diameter between 30 and 500 nanometer. More preferred the ethylcellulose particles have 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. Most preferred the volume weighted mean diameter of the precipitated ethylcellulose particles is between 100 and 200 nanometer, or even between 100 and 150 nanometer.

All preferred embodiments of the first and second aspect of the invention may be applicable to this third aspect of the invention, mutatis mutandis.

Aerated food products comprising gas bubbles stabilised by solid particles In a fourth aspect the invention provides an aerated anhydrous fat-based food product or an aerated fat-continuous food product comprising gas bubbles stabilised by solid particles having a volume weighted mean diameter between 30 and 1000 nanometer, wherein the food product has an overrun of at least 1% and a water content of less than 10% by weight.

Preferably the solid particles have a volume weighted mean diameter between 30 and 500 nanometer, more preferred between 50 and 500 nanometer, more preferred between 30 and 300 nanometer, even more preferred between 50 and 300 nanometer, more preferred between 60 and 300 nanometer, and even more preferred between 70 and 300 nanometer. Alternatively, in another preferred embodiment the solid particles have a volume weighted mean diameter between 50 and 200 nanometer. In another alternative most preferred embodiment the solid 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 solid particles is between 100 and 200 nanometer, or even between 100 and 150 nanometer. Alternatively preferably the solid 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 solid 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.

The aerated food product preferably has an overrun of at least 5%, more preferably at least 10%, most preferably at least 20%. Preferably the food product has an overrun of at most 200%, more preferred 150%, even more preferably at most 120%, most preferably at most 100%. In one embodiment, the food product is an aerated butter, margarine or spread, in which case the overrun is preferably from 5 to 50%, more preferably from 10 to 20%, for example about 15%. In another embodiment the food product is a cooking oil which is aerated in order to reduce spattering, in which case the overrun is preferably less than 10%, typically about 5%.

Preferably, the water content of the food product is less than 5 wt%. More preferably it is less than 3 wt%, especially less than 2 wt%. Preferably during manufacturing the food product contains less than about 0.5 wt% moisture but during storage of the product, some moisture may migrate to the product. Preferably the food product according the fourth aspect of the invention is an anhydrous food product.

Preferably the food product according the fourth aspect of the invention is selected from chocolate, chocolate analogue, butter, ghee, margarine, low fat spreads, cooking fats and oils, shortening, peanut butter, and chocolate spread. Most preferred the food product is chocolate or chocolate analogue. The preferred chocolate or chocolate analogue may be consumed as such, or may be used as an ingredient of another food product, such as chocolate chunks in ice cream or dessert, or similar product. It may also be used as a coating for ice cream.

Preferably the food product comprises gas bubbles, wherein at least 50% of the number of gas bubbles has a size smaller than 200 micrometer. More preferred, at least 50% of the number of gas bubbles has a size smaller than 100 micrometer. Even more preferred at least 75% of the number of gas bubbles has a size smaller than 75 micrometer.

Preferably the food product according to the fourth aspect of the invention comprises ethylcellulose particles as solid particles. All preferred embodiments of the second aspect of the invention may be applicable here as well, mutatis mutandis. Preferably these ethylcellulose particles have a volume weighted mean diameter between 30 and 500 nanometer. More preferred the ethylcellulose particles have a diameter between 50 and 500 nanometer, more preferred 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 solid particles have a volume weighted mean diameter between 50 and 200 nanometer. In another alternative most preferred embodiment the solid 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 is between 100 and 200 nanometer, or even between 100 and 150 nanometer. Alternatively preferably the solid 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 solid 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 has an absolute value below 25 millivolt, preferably below 20 millivolt, more preferred below 15 millivolt, leading to stable foams.

All preferred embodiments of the first, second and third aspects of the invention may be applicable to the fourth aspect of the invention, mutatis mutandis.

Preferred embodiments of the food products according to the third or fourth aspects of the invention The following preferred embodiments may be applicable to both the third and fourth aspects of the invention. Advantageously the food products according to the third or fourth aspects of the present invention remain stable for at least one month, more preferably more than two months.

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.

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. 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.

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%.

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.

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 following claims.

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 25°C in 80/20 toluene/ethanol). Acetone (analytical grade), ethanol (analytical grade) and tetrahydrofuran (analytical grade), were obtained from Sigma-Aldrich Chemicals (Schnelldorf, Germany) and used without further purification. Deionised water was obtained from a Millipore filter system. Citrus fibers were supplied by Herbafood GmbH (Germany), trade name Herbacel AQ Plus Citrus Fibre, type N. Xanthan gum was supplied by CP Kelco, trade name Keltrol xanthan gum, type RD.

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 size and volume weighted mean size (d _{4 3} ) is smaller than 10%. In the present case the z-average diameter is at maximum 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.

Bubble diameter

The bubble size 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 size. 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 - '

VI

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: 2d λ =

3Φ(1 - g)Q

Where g and Q are optical constants given by Mie theory. For foam dispersed in a transparent liquid, this method provides an estimate of the number average bubble size. Example 1 : Milk chocolate aerated by ethylcellulose foam

1 g ethyl cellulose (Hercules) powder was dissolved in 100 ml acetone (purity of >98%), at 35°C in a 500ml beaker until completely dissolved. An equal volume of distilled water was quickly added into the ethylcellulose solution under strong stirring to precipitate the ethylcellulose into particles. The solution was left to stir for another 10 minutes after which the acetone and some of the water were evaporated under low pressure until a final concentration of ethylcellulose in water of 2 wt% was obtained. The volume weighted mean diameter d _{4 3} of the ethylcellulose particles was between 100 and 500 micrometer.

200 ml of above-mentioned 2.0 wt% ethylcellulose dispersion was placed into a 400 ml beaker, and its pH was tuned to below 4 by adding a small amount of 10 vol% acetic acid aqueous solution. After stirring for 10 minutes, the dispersion was aerated by using an ultraturrax mixer (IKA, T-18) for 2 minutes at about 16,000 rpm. The foam volume was increased to about 400 ml (overrun 100%). Optical microscopical observation revealed that the bubbles were polydispersed, and the bubble size ranged from submicron to tens of microns. The ethylcellulose foam was left to drain for 4 hours, and the drained water was removed with a syringe or pipette in order to minimise the amount of water added to aerated chocolates. Most of the bubbles jad a diameter less than 30 microns.

30.0 g milk chocolate bar (Dove Chocolate, Mars) was melted at 60 ⁰ C in a 100 ml beaker. 30.0 g drained foam was mixed with the melting chocolate at 60 ⁰ C via hand- mixing, until a homogeneous product was obtained.

Finally, the total volume of the aerated chocolate was about 90 ml. Based on the resultant volume and total weight, the density of the aerated chocolate was about 0.67 g/ml, and the overrun reached 50%. The aerated chocolate was put into a refrigerator at 5 ⁰ C. Four days later, the total volume had decreased to about 80 ml with an overrun of 33% and a density of 0.75 g/ml, caused by shrinking bubbles when cooling down to room temperature, as well as the collapse of some bubbles. This means that the chocolate is stable, as only about 10% volume is lost. The bubbles were not visible to the naked eye. Example 2: Milk chocolate aerated by heated ethylcellulose foam with citrus fibres 0.4 g of citrus fibres and 200 ml of above-mentioned (example 1) 2.0 wt% ethylcellulose dispersion were placed into a 400 ml beaker, and stirred for 1 hour to make the citrus fibres well separated and hydrated. A small amount of 10 vol% acetic acid aqueous solution was used to tune the pH of the dispersion from neutral to below 4. After stirring for 10 minutes, the dispersion was aerated by using an ultraturrax mixer (IKA, T-18) for 2 minutes at about 16,000 rpm to a total volume of 400 ml (overrun 100%). The bubble size ranged from submicron to tens of microns.

The prepared ethylcellulose foam was moved to a 500 ml Schott-Duran premium bottle, and left to drain for 1 hour. And then the well sealed bottle was heated at 13O ⁰ C for 2 hours in an oven. After the bottle had cooled down, some drained water was removed with a syringe. Finally, about 50 gram of heated ethylcellulose foam with citrus fibres had been obtained.

30.0 g milk chocolate bar (Kraft Foods) was melted at 60 ⁰ C in a 100 ml beaker. 30.0 g of the heated ethylcellulose foam with citrus fibres was mixed with the melting chocolate at 60°C via hand-mixing, until a homogeneous product was obtained. The total volume of the aerated chocolate was 100 ml. The density of the aerated chocolate was about 0.60 g/ml, and the overrun reached 67%. The aerated chocolate was put into a refrigerator at 5°C.

About 2 months later, the total volume had decreased to about 83 ml with an overrun of 38% and a density of 0.73 g/ml. This is considered to be sufficiently stable. The aerated chocolate with heated foam was more stable than that with unheated foam (example 1).

Example 3: Pure chocolate aerated by heated ethylcellulose foam with citrus fibres 0.4 g of citrus fibres and 200 ml of above-mentioned (example 1) 2.0 wt% ethylcellulose dispersion were placed into a 400 ml beaker, and stirred for 1 hour to make the citrus fibres well separated and hydrated. A small amount of 10 vol% acetic acid aqueous solution was used to tune the pH of the dispersion from neutral to below 4. After stirring for 10 minutes, the dispersion was aerated by using an ultraturrax mixer (IKA, T-18) for 2 minutes at about 16,000 rpm to a total volume of 400 ml (overrun 100%). The bubble size ranged from submicron to tens of microns.

The prepared ethylcellulose foam was moved to a 500 ml Schott-Duran premium bottle, and left to drain for 1 hour. And then the well sealed bottle was heated at 130 ⁰ C for 2 hours in an oven. After the bottle had cooled down, some drained water was removed with a syringe. Finally, about 50 gram of heated ethylcellulose foam with citrus fibres had been obtained.

30.0 g extra pure chocolate bar (Fair Trade Original) was melted at 60 ⁰ C in a 100 ml beaker. 30.0 g of the heated ethylcellulose foam with citrus fibres was mixed with the melting chocolate at 60°C via hand-mixing, until a homogeneous product was obtained. Finally, the total volume of the aerated chocolate was about 85 ml. The density of the aerated chocolate was about 0.71 g/ml, and the overrun reached 41%. The aerated chocolate was put into a refrigerator at 5°C.

About 2 months later, the total volume had decreased to about 72 ml with an overrun of 20% and a density of 0.84 g/ml. This is good stability.

Comparative example 4: Milk chocolate aerated by SDS foam with xanthan

Preparation of 0.1 wt% sodium dodecyl sulfate (SDS) aqueous solution with 0.05 wt% xanthan gum: 200 ml of distilled water was placed into a 500 ml beaker, and then 0.10 gram of xanthan gum was dissolved in the water at 60 ⁰ C, until the solution become clear and homogeneous. After the xanthan solution had cooled down to room temperature (~25°C), 0.2 gram of SDS was dissolved in the solution during stirring.

The 200 ml of 0.1 wt% SDS solution containing 0.05 wt% xanthan gum was aerated by using an ultraturrax (IKA, T-18) at about 16,000 rpm for 5 minutes. The foam volume increased to about 500 ml, and the overrun reached 150%. The foam with xanthan gum showed better stability than a foam stabilised by SDS alone, although the bubbles also grow bigger along with time. So the foam with xanthan can be used to aerate chocolates via the post-addition. Observation by optical microscope indicated that the bubbles were polydispersed, ranging from tens of microns to several hundreds of microns. 30.0 g of milk chocolate bar (Dove Chocolate, Mars) was melted at 60 ⁰ C in a 100 ml beaker. 20.0 g of freshly prepared SDS foam containing xanthan was mixed with the melting chocolate at 60 ⁰ C via hand-mixing, until a homogeneous product was obtained. Finally, the total volume of the aerated chocolate was about 63 ml. The density of the aerated chocolate was about 0.80 g/ml, and the overrun reached 25%. The aerated chocolate was put in a refrigerator at 5°C. 30 minutes later, it was clearly observed that most bubbles floated up and grew bigger, and the continuous phase drained down. After 3 days, the total volume of aerated chocolate decreased to 55 ml with the overrun of 10 % and the density of 0.91 g/ml due to the collapse of bubbles. Furthermore, the aerated chocolate became phase separated clearly. Most of bubbles were enriched in the top layer with about 25 ml, at the same time the bottom layer was drained continuous phase with about 30 ml. The phase separation means that the air phase (or foam phase) is separated from the continuous phase, for most of bubbles float up to the top.