WO2010139987A2

WO2010139987A2 - Mesoporous materials

Info

Publication number: WO2010139987A2
Application number: PCT/GB2010/050914
Authority: WO
Inventors: Leigh Trevor Canham; Joe Raguso
Original assignee: Intrinsiq Materials Global Limited
Priority date: 2009-06-02
Filing date: 2010-05-28
Publication date: 2010-12-09
Also published as: WO2010139987A3; GB0909460D0

Abstract

The use of a mesoporous material for modifying the flavour and/or texture of a foodstuff composition or an oral hygiene composition wherein at least some of the pores of the mesoporous material are loaded with at least one ingredient is described.

Description

MESOPQROUS MATERIALS

Field of the Invention

This invention relates to mesoporous materials and their use for modifying food and oral hygiene compositions, including their taste and/or texture.

Background of the invention

The flavour of foods is a combination of taste and smell and in many cases is closely associated with mouthfeel. The five main classes of taste are sweet, salt, sour, bitter and umami. The main classes of taste are detected on the tongue, the pharynx and soft palate of the human mouth. Other flavours are associated with odours. Odours are detected in the nose when volatile compounds in minute quantities come into contact with the olfactory nerve endings.

A sweet taste is typical of the low molecular weight carbohydrates such as fructose, glucose and sucrose. These have little "after-taste" but promote tooth decay and obesity when consumed in excess. Sugar substitutes range from potent sweeteners such as saccharin (up to 500 times the sweetness of sucrose) to low calorie polyols such as xylitol and sorbitol. Some combinations of amino acids are also very sweet, such as aspartame which is made from phenylalanine and aspartic acid.

The salt taste is a property of low molecular weight salts, particularly those comprising a halide such as sodium chloride. The order of decreasing saltiness is chlorides, bromides, iodides, sulphates and nitrates. Sodium salts are more salty than potassium salts which can be quite bitter.

The presence of acid in food or drink gives rise to a sour taste. Acids found in food tend to be weak. Examples of acids found in food include unionized organic acids.

A number of organic and inorganic compounds provide a bitter taste. Examples include the alkaloids such as quinone and caffeine, and some compounds comprising magnesium, calcium or ammonium ions. The umami taste is due to the carboxylate anion of glutamic acid, a naturally occurring amino acid present in meats, cheese and other protein-rich foods.

Food flavours are usually complex mixtures of hydrocarbons, alcohols, acids, aldehydes, ketones and esters. The most common types of volatile food flavours from fruit and vegetables are essential oils. Examples include oil of almond, clove, garlic, ginger, lemon, lime, mace, orange and thyme. Oleoresins are a class of less volatile flavour substances extracted from herbs and spices using solvents. Terpenoids are a very large group of odour compounds present in foods.

So-called mouthfeel is often used to indicate the texture of food during consumption, but it can also cover sensations such as "tingling", "hot" and "watery". The physical texture of food can influence its flavour. Flavour modifiers are agents used to enhance or reduce the level of a flavour. An official definition currently in use is "any substance which is capable of enhancing, reducing or otherwise modifying the taste or odour, or both, of a food but does not include water or enzymes or any substance primarily used to impart taste, or odour, or both, to a food."

Factors which influence taste perception include flavour molecule concentration, its rate and duration at receptor sites, the temperature, viscosity and area of application, the chemical state of the saliva and the presence of other flavours in the mouth.

The present invention is based on the surprising finding that mesoporous materials, preferably in microparticulate form, are suitable as flavour modifiers for use in foodstuff compositions and oral hygiene compositions.

Summary of the Invention

According to a first aspect of the present invention, there is provided the use of a mesoporous material for modifying the flavour and/or texture of a foodstuff composition or an oral hygiene composition wherein at least some of the pores of the mesoporous material are loaded with at least one ingredient.

According to a further aspect of the present invention there is provided a method for modifying the flavour of a foodstuff composition or an oral hygiene composition comprising blending a mesoporous material wherein at least some of the pores of the mesoporous material are loaded with at least one ingredient with other components of the foodstuff or oral hygiene composition. There is also provided a method of increasing the potency of a food ingredient, such as a flavouring agent, comprising blending a mesoporous material wherein at least some of the pores of the mesoporous material are loaded with at least one flavouring agent with other components of the foodstuff or oral hygiene composition. There is also provided a method of masking the taste of a food ingredient, such as a flavouring agent, comprising blending a mesoporous material wherein at least some of the pores of the mesoporous material are loaded with at least one flavouring agent with other components of the foodstuff or oral hygiene composition. An increase in the potency of a food ingredient may be measured relative to the potency of that food ingredient in the absence of the mesoporous material. Similarly, the ability of the mesoporous material to mask the taste of a food ingredient may be measured relative to when the mesoporous material is not present.

Advantageously, said ingredient may be retained in an amorphous state by the mesoporous material. The present invention extends to a method for retaining an ingredient in an amorphous state and/or converting an ingredient suitable for use in a foodstuff or oral hygiene composition to a different physical form. The present invention also extends to the use of a mesoporous material wherein at least some of the pores of the mesoporous material are loaded with at least one ingredient for delivering said at least one ingredient to the human or animal tongue, the pharynx or soft palate.

In the various aspects of the present invention, the at least one loaded ingredient is released on contact or shortly after contact with the human or animal tongue, the pharynx or soft palate.

According to a further aspect of the invention, there is provided a foodstuff composition or an oral hygiene composition suitable for delivering flavour to the human and/or animal tongue comprising a mesoporous material wherein at least some of the pores of the mesoporous material are loaded with at least one ingredient.

The loaded ingredient may be chosen from a range of flavour ingredients. For example the at least one ingredient may be selected from sugar and/or salt. Other suitable ingredients include water, polyol, an antiseptic agent, an antimicrobial agent, an essential oil.

Advantageously, for delivering effective quantities of salt and/or sugar to the human or animal tongue, the mesoporous materials may be selected from a preferred range of diameters. The present inventors have found that mesoporous materials possessing a particle size diameter of about 5 to 15μm are particularly effective at delivering flavour ingredients to the tongue, thus allowing appropriate reductions of the amounts of flavour agents such as salt and/or sugar in food.

In the various aspects of the invention, the mesoporous microparticulate material may be encapsulated by a capping layer. The mesoporous material may be a mesoporous microparticulate material.

The use of the mesoporous materials according to the present invention provides for a range of benefits, including avoidance of mouth cooling during food hydrolysis, increase in mouth warming during food ingestion ("melt in the mouth"), salt reduction in foods, sugar reduction in foods, calorie reduction in foods, improved targeting in the mouth, taste masking for bitter actives. For example, the present inventors have found that the potency of hydrophilic core flavourings such as salt and sugar can be increased by increasing their surface area and utilizing particle sizes tuned to taste bud morphology on the human or animal tongue. Advantageously, the present inventors have found that by carefully selecting the mesoporous particulate materials to lie within a certain size range, e.g. about 5 to 15μm then flavourings such as salt and sugar may be delivered to the human or animal mouth much more effectively such that the amount of sugar and/or salt may be reduced but without compromising the intensity of flavour. More specifically, such highly targeted delivery with rapid dissolution lowers the fraction of salt or sugar that is swallowed before it contributes to taste allowing either salt or sugar reduction in the corresponding foodstuff composition. By way of further example, the present inventors have also found that through careful selection of the degree of mesoporosity in combination with pore diameter then mouthfeel may be controlled. For example, the use of starch possessing a mesoporosity above about 70% in combination with all of or substantially all of the pores being less than 75nm in diameter and loaded with sweetener such as xylitol is beneficial in providing a so called melt in the mouth sensation in food compositions such as ice cream. The flavour and mouthfeel of loaded mesoporous materials may be assessed using analysis techniques such as the flavour profile method and the texture profile method. These methods are described in Chapter 10 of Sensory Evaluation Techniques, 4^th edition (CRC Press 2007), edited by M. C. Meilgaard et al.

Detailed Description of the Invention

Mesoporous material

Suitable mesoporous materials include organic and inorganic materials. More specifically, suitable mesoporous materials include mesoporous silicon, oxidised mesoporous silicon, mesoporous silica, mesoporous calcium phosphates (e.g. hydroxyapatite), mesoporous metal carbonates, mesoporous alumina, mesoporous carbon, mesoporous vegetable materials (e.g. cellulose), mesoporous starch, mesoporous titania, mesoporous silicates (e.g. calcium silicate), mesoporous polymers.

Mesoporous materials contain pores having a diameter in the range of 2 to 50nm. Advantageously, the mesoporous materials have a pore diameter of 5 to 50nm. The present inventors have found that pore diameters in the ranges specified can maintain high wt% of entrapped ingredients in an amorphous state that radically changes their behaviour when released in the human or animal mouth. The present inventors have also found that when sufficiently nanoentrapped many ingredients can be kept in an amorphous state that alters their heat of solution when dissolving in the mouth. This can make the dissolution process more exothermic or change an endothermic process to an exothermic one.

The average pore diameter is measured using a known technique. Mesopore diameters are measured by very high resolution electron microscopy. This technique and other suitable techniques which include gas-adsorption-desorption analysis, small angle x-ray scattering, NMR spectroscopy or thermoporometry, are described by R. Herino in "Properties of Porous Silicon", chapter 2.2, 1997.

The mesoporous material may have a BET surface area of 10m²/g to 700m²/g for example 100m²/g to 400m²/g. The BET surface area is determined by a BET nitrogen adsorption method as described in Brunauer et at., J. Am. Chem. Soc, 60, p309, 1938.

The BET measurement is performed using an Accelerated Surface Area and Porosimetry Analyser (ASAP 2400) available from Micromeritics Instrument Corporation, Norcross, Georgia 30093. The sample is outgassed under vacuum at 350⁰C for a minimum of 2 hours before measurement.

Microparticles are particles of about 1 to 1000μm in diameter. Methods for making microparticles are well known in the art. These include chemical or gas phase synthesis methods or electrochemical etching or comminution (e.g. milling as described in Kerkar et al. J. Am. Ceram. Soα, vol. 73, pages 2879-2885, 1990). The present inventors have found that advantageously the d₅₀ of the mesoporous material may be about 1 to 10μm, for example 1 to 5μm, for example about 2μm. In particular, these values of d₅₀ provide increased levels of salty taste without increasing the amount of salt ingested.

As used herein, and unless otherwise stated, the term "silicon" refers to solid elemental silicon. For the avoidance of doubt, and unless otherwise stated, it does not include silicon-containing chemical compounds such as silica, silicates or silicones, although it may be used in combination with these materials.

The silicon may be about 95 to 99.99999% pure, for example about 96 to 99.9% pure. So-called metallurgical silicon, which is suitable for use in foodstuffs according to the present invention, has a purity of about 98 to 99.5%.

The physical forms of silicon which are suitable for use according to the present invention may be chosen from or comprise one or more of amorphous silicon, single crystal silicon and polycrystalline silicon (including nanocrystalline silicon, the grain size of which is typically taken to be 1 to 100nm) and including combinations thereof. Any of the above-mentioned types of silicon may be porosified to form mesoporous silicon.

Methods for making silicon powders such as silicon microparticles are well known in the art. Methods for making silicon powders are often referred to as "bottom-up" methods, which include, for example, chemical synthesis or gas phase synthesis.

Alternatively, so-called "top-down" methods refer to such known methods as electrochemical etching or comminution (e.g. milling as described in Kerkar et al. J.

Am. Ceram. Soc, vol. 73, pages 2879-2885, 1990). PCT/GB02/03493 and PCT/GB01/03633, the contents of which are incorporated herein by reference in their entirety, describe methods for making particles of silicon, said methods being suitable for making silicon for use in the present invention. Such methods include subjecting silicon to centrifuge methods, or grinding methods.

Methods for making various forms of silicon which are suitable for use in the present invention are described below.

In PCT/GB96/01863, the contents of which are incorporated herein by reference in their entirety, it is described how bulk crystalline silicon can be rendered porous by partial electrochemical dissolution in hydrofluoric acid based solutions. This etching process generates a silicon structure that retains the crystallinity and the crystallographic orientation of the original bulk material. Hence, the porous silicon formed is a form of crystalline silicon. Broadly, the method involves anodising, for example, a heavily boron doped CZ silicon wafer in an electrochemical cell which contains an electrolyte comprising a 20% solution of hydrofluoric acid in an alcohol such as ethanol, methanol or isopropylalcohol (IPA). Following the passing of an anodisation current with a density of about 50mAcm^"2, a porous silicon layer is produced which may be separated from the wafer by increasing the current density for a short period of time. The effect of this is to dissolve the silicon at the interface between the porous and bulk crystalline regions. Porous silicon may also be made using the so-called stain-etching technique which is another conventional method for making porous silicon. This method involves the immersion of a silicon sample in a hydrofluoric acid solution containing a strong oxidising agent. No electrical contact is made with the silicon, and no potential is applied. The hydrofluoric acid etches the surface of the silicon to create pores.

The mesoporous silicon may be generated from a variety of non-porous silicon powders by so-called "electroless electrochemical etching techniques", as reviewed by K. Kolasinski in Current Opinions in Solid State & Materials Science 9, 73 (2005). These techniques include "stain-etching", "galvanic etching", "hydrothermal etching" and "chemical vapour etching" techniques. Stain etching results from a solution containing fluoride and an oxidant. In galvanic or metal-assisted etching, metal particles such as platinum are also involved. In hydrothermal etching, the temperature and pressure of the etching solution are raised in closed vessels. In chemical vapour etching, the vapour of such solutions, rather than the solution itself is in contact with the silicon. Mesoporous silicon can be made by techniques that do not involve etching with hydrofluoric acid. An example of such a technique is chemical reduction of various forms of porous silica as described by Z. Bao et al in Nature vol. 446 8th March 2007 p172-175 and by E. Richman et a!, in Nano Letters vol. 8(9) p3075-3079 (2008). If this reduction process does not proceed to completion then the mesoporous silicon contains varying residual amounts of silica.

Following its formation, the mesoporous silicon may be dried. For example, it may be supercritically dried as described by Canham in Nature, vol. 368, (1994), pp133-135. Alternatively, the mesoporous silicon may be freeze dried or air dried using liquids of lower surface tension than water, such as ethanol or pentane, as described by Bellet and Canham in Adv. Mater, 10, pp487-490, 1998.

Silicon hydride surfaces may, for example, be generated by stain etch or anodisation methods using hydrofluoric acid based solutions. When the silicon is prepared, for example, by electrochemical etching in HF based solutions, the surface of the mesoporous silicon may or may not be suitably modified in order, for example, to improve the stability of the mesoporous silicon in the composition. In particular, the surface of the mesoporous silicon may be modified to render the silicon more stable in alkaline conditions. The surface of the mesoporous silicon may include the external and/or internal surfaces formed by the pores of the mesoporous silicon.

In certain circumstances, the stain etching technique may result in partial oxidation of the mesoporous silicon surface. The surfaces of the mesoporous silicon may therefore be modified to provide: silicon hydride surfaces; silicon oxide surfaces wherein the mesoporous silicon may typically be described as being partially oxidised; or derivatised surfaces which may possess Si-O-C bonds and/or Si-C bonds. Silicon hydride surfaces may be produced by exposing the mesoporous silicon to HF.

Silicon oxide surfaces may be produced by subjecting the silicon to chemical oxidation, photochemical oxidation or thermal oxidation, as described for example in Chapter 5.3 of Properties of Porous Silicon (edited by LT. Canham, IEE 1997). PCT/GB02/03731 , the entire contents of which are incorporated herein by reference, describes how mesoporous silicon may be partially oxidised in such a manner that the sample of mesoporous silicon retains some elemental silicon. For example, PCT/GB02/03731 describes how, following anodisation in 20% ethanoic HF, the anodised sample was partially oxidised by thermal treatment in air at 500⁰C to yield a partially oxidised mesoporous silicon sample. The surface of the elemental mesoporous silicon may comprise one or more silicon compounds. For example, at least some of the mesoporous silicon surface may comprise silicon bonded to oxygen to form an oxide layer. The silicon particles may possess an oxide content corresponding to between about one monolayer of oxygen and a total oxide thickness of less than or equal to about 4.5nrm covering the entire silicon skeleton. The mesoporous silicon may have an oxygen to silicon atomic ratio between about 0.04 and 2.0, and preferably between 0.60 and 1.5. Oxidation may occur in the pores and/or on the external surface of the silicon.

The mesoporous silicon for use in the present invention may be derivatised. Derivatised porous silicon is porous silicon possessing a covalently bound monolayer on at least part of its surface. The monolayer typically comprises one or more organic groups that are bonded by hydrosilylation to at least part of the surface of the porous silicon. Derivatised porous silicon is described in PCT/GBOO/01450, the contents of which are incorporated herein by reference in their entirety. PCT/GBOO/01450 describes derivatisation of the surface of silicon using methods such as hydrosilyation in the presence of a Lewis acid. In that case, the derivatisation is effected in order to block oxidation of the silicon atoms at the surface and so stabilise the silicon. Methods of preparing derivatised porous silicon are known to the skilled person and are described, for example, by J. H. Song and M.J. Sailor in Inorg. Chem. 1999, vol 21 , No. 1-3, pp 69-84 (Chemical Modification of Crystalline Porous Silicon Surfaces). Derivitisation of the silicon may be desirable when it is required to increase the hydrophobicity of the silicon, thereby decreasing its wettability. Preferred derivatised surfaces are modified with one or more alkyne groups. Alkyne derivatised silicon may be derived from treatment with acetylene gas, for example, as described in "Studies of thermally carbonized porous silicon surfaces" by J. Salonen et al in Phys Stat. Solidi (a), 182, pp123-126, (2000) and "Stabilisation of porous silicon surface by low temperature photoassisted reaction with acetylene", by S. T. Lakshmikumar et al in Curr. Appl. Phys. 3, pp185-189 (2003). The mesoporous silicon may be derivatised during its formation in HF-based electrolytes, using the techniques described by G. Mattei and V. Valentin! in Journal American Chemical Society vol 125, p9608 (2003) and Valentini et al., Physica Status Solidi (c) 4 (6) p2044-2048 (2007).

Suitable other mesoporous materials are described below. Mesoporous silica may be made according to the methods described in US 5951962 and US 20070003492, the contents of which are hereby incorporated by reference in their entirety. For example, the mesoporous silica may be made by converting a silica precursor in a water containing reaction medium containing a polymer dispersion. Mesoporous calcium phosphates (e.g. mesoporous hydroxyapatites) may be made according to the methods described in US 6558703, the entire contents of which are hereby incorporated by reference in their entirety. Mesoporous metal carbonates may be made as described in US 6749825, the entire contents of which are hereby incorporated by reference in their entirety. Mesoporous alumina may be made as described in Chem. Commun., 1986-1987 (2005). Mesoporous vegetable materials, for example, cellulose may be made according to the methods described in US 5011701 the contents of which are hereby incorporated by reference in their entirety. Mesoporous starch may be made according to the methods described in US 5919486 and US 4985082 the contents of which are hereby incorporated by reference in their entirety. Mesoporous silicates (or bioactive glasses) such as calcium silicate may be made as described in J. Controlled Release 110, 522(2006). Mesoporous titania may be made as described in Mater. Lett 59, 3308 (2005). Mesoporous carbon materials may be made with reference to Angewandte Chemie 7, (20) 3696 (2008). The contents of all of these references are incorporated herein in their entirety by reference.

In the present invention, particle size distribution measurements, including the mean particle size (d₅₀/μm) of the particles are measured using a Malvern Particle Size

Analyzer, Model Mastersizer, from Malvern Instruments. A helium-neon gas laser beam is projected through a transparent cell which contains the particles suspended in an aqueous solution. Light rays which strike the particles are scattered through angles which are inversely proportional to the particle size. The photodetector array measures the quantity of light at several predetermined angles. Electrical signals proportional to the measured light flux values are then processed by a microcomputer system, against a scatter pattern predicted from theoretical particles as defined by the refractive indices of the sample and aqueous dispersant to determine the particle size distribution of the particles.

The loaded ingredient

The mesoporous material is loaded such that one or more ingredients are present in the pores of the material. The loaded ingredient or ingredients may be referred to as being entrapped. The loaded one or more ingredients may be selected from one or more of food ingredients or oral hygiene ingredients which modify the flavour and/or texture of the foodstuff composition and oral hygiene composition. For example, the loaded ingredient may be water or ice. For example, the loaded ingredient may be selected from one or more of a sweetener including aspartame, acesulfame K, sucralose, fructose, xylitol, sorbitol, mannitol, lactitol, isomalt, mannitol, trehalose. For example, the loaded ingredient may be a salt selected from sodium chloride, potassium chloride. For example, the loaded ingredient may be selected from one or more oral hygiene agents including sweeteners, flavours, breath freshening agents, anti-plaque agents, anti-gingivitis agents, anti-calculus agents, tooth whitening agents, herbal extracts, pain-relief agents, sensates, cooling agents, warming agents, colouring agents, stimulants, essential oils.

The ingredient to be loaded with the mesoporous material may be dissolved or suspended in a suitable solvent, and mesoporous particles may be incubated in the resulting solution for a suitable period of time. Both aqueous and non-aqueous slips have been produced from ground silicon powder and the processing and properties of silicon suspensions have been studied and reported by Sacks in Ceram. Eng. Sci. Proc, 6, 1985, pp1109-1 123 and Kerkar in J. Am. Chem. Soc. 73, 1990, pp2879-85. The removal of solvent will result in the ingredient penetrating into the pores of the mesoporous material by capillary action, and, following solvent removal, the ingredient will be present in the pores. Preferred solvents, at least for use in connection with mesoporous silicon, are water, ethanol, and isopropyl alcohol, GRAS solvents and volatile liquids amenable to freeze drying.

Typically, the one or more ingredients are present in the range, in relation to the loaded mesoporous particulate material, of 0.01 to 90wt%, for example 1 to 40wt%, for example 20 to 55wt%, for example 20 to 50wt% (optionally, in combination with about 70% porosity) and for example 2 to 10wt%.

Higher levels of loading, for example, at least about 15wt% of the loaded ingredient based on the loaded weight of the mesoporous material may be achieved by performing the impregnation at an elevated temperature. For example, loading may be carried out at a temperature which is at or above the melting point of the ingredient to be loaded. Quantification of gross loading may conveniently be achieved by a number of known analytical methods, including gravimetric, EDX (energy-dispersive analysis by x-rays), Fourier transform infra-red (FTIR), Raman spectroscopy, UV spectrophotometry, titrimetric analysis, HPLC or mass spectrometry. If required, quantification of the uniformity of loading may be achieved by techniques that are capable of spatial resolution such as cross-sectional EDX, Auger depth profiling, micro- Raman and micro-FTIR.

The loading levels can be determined by dividing the volume of the ingredient taken up during loading (equivalent to the mass of the ingredient taken up divided by its density) by the void volume of the mesoporous material prior to loading, multiplied by one hundred.

The capping layer

The optional capping layer serves to encapsulate the mesoporous particulate material. In encapsulating the mesoporous material, the openings to the pores are sealed. Typically, the whole of the particle, or substantially the entire particle, is coated with the capping layer and the capping layer may be referred to herein as a bead. The capping layer at least seals the openings to the pores at the surface of the mesoporous material, thus ensuring that the at least one loaded ingredient is retained. The capping layer, or bead, may encapsulate more than a single mesoporous microparticulate material. The thickness of the capping layer may be about 0.1 to 50μm in thickness, for example about 0.5 to 45μm for example about 1 to 10μm, for example about 1 to 5μm. The capping layer may provide retention of an ingredient over a period of a few months to many months, for example up to about 5 years, followed by triggered release through site specific degradation which occurs in the human or animal mouth. The capping layer may be an organic or an inorganic capping layer. The encapsulated particles may consist essentially of inorganic particles capped with an organic material or an organic particle capped with an inorganic material. Alternatively, the encapsulated particles may consist essentially of organic particles capped with an organic material or inorganic particles capped with an inorganic material. The use of a capping layer is particularly advantageous when used with wet products and when used with dry products where the loaded ingredient is volatile.

The thickness of the capping layer is measured by mechanically fracturing a number of the capped particles and examining their cross-sectional images in a high resolution scanning electron microscope, equipped with energy dispersive x-ray analysis (EDX analysis) of chemical composition. Alternatively, if the particle size distributions are measured accurately, before and after capping, then the average thickness of micron thick layer caps can be estimated. For relatively narrow particle size distributions and uniform coatings, if the density of the capping layer is known accurately, then accurate gravimetric measurements of weight increase that accompanies capping can also yield an average cap thickness.

Advantageously, the capping layer may comprise, consist of, or consist essentially of, a material which is present in the loaded ingredient. For example, when the loaded mesoporous material is for use in dentifrice compositions, such as toothpaste, then the capping layer may include one or more of: titanium dioxide, carageenan, xanthum gum, cellulose gum, tocopherol. Similarly, when the loaded mesoporous material is intended for use in chocolate then the capping layer may include one or more of: cocoa butter, vegetable fat, milk fat, lecithin. The functions of capping layer and loaded ingredient may be provided by the same material.

The capping layer may comprise one or more than one distinct layer. For example, the capping layer may comprise a hydrophilic layer and a hydrophobic layer. Where there are distinct layers present of different materials then one of the layers may overlie the other.

The capping layer or layers may be selected from one or more of the following: carbohydrates, gums, lipids, proteins, celluloses, polymers, elastomers, inorganic materials.

Suitable examples of carbohydrates include starch, dextran, sucrose, corn, syrup. Suitable examples of gums include carrageenan, alginate, e.g. sodium alginate, gum Arabic, agar. Suitable examples of lipids include fats, hardened oils, paraffin, stearic acid, wax, diglycerides, monoglycerides. Suitable examples of proteins include albumin, casein, gluten, gelatine. Suitable examples of celluloses include carbomethylcellulose, acetylcellulose, methylcellulose. Suitable examples of polymers include synthetic polymers such as polyacrylate, polyethylene, polystyrene, polyvinyl alcohol, polyurea. Suitable examples of elastomers include acrylonitrile, polybutadience. Suitable examples of inorganic materials include calcium sulphate, silicates, clays, silicon, silicon dioxide, calcium phosphate. The capping layer may comprise, consist of, or consist essentially of elemental silicon, for example, in the form of an amorphous silicon coating or a discontinuous layer of silicon nanoparticles.

Suitable methods for capping the mesoporous material include: spray drying, fluidised bed coating, pan coating, modified microemulsion techniques, melt extrusion, spray chilling, complex coacervation, vapour deposition, solution precipitation, emulsification, supercritical fluid techniques, physical sputtering, laser ablation, very low temperature sintering and thermal evaporation.

Spray drying techniques, especially in the food industry, are usually carried out from aqueous feed formulations, in which case the capping layer should be soluble in water at an acceptable level. Typical materials include gum acacia, maltodextrins, hydrophobically modified starch and mixtures thereof. Other polysaccharides such as alginate, carboxymethylcellulose, guar gum and proteins such as whey proteins, soy proteins, sodium caseinate are also suitable. Aqueous two phase systems (ATPs) which may result from the phase separation of a mixture of soluble polymers in a common solvent due to the low entropy of mixing of polymer mixtures can be used to design double encapsulated ingredients in a single spray drying step.

Spray chilling or cooling is generally considered one of the least expensive encapsulation technologies. This technique may also be referred to as matrix encapsulation, it is particularly suitable for encapsulating organic and inorganic materials as well as textural ingredients, enzymes, flavours and other ingredients to improve heat stability. Matrix encapsulation may lead to some of the loaded ingredient being incorporated in the capping layer.

Extrusion is suitable for the encapsulation of volatile and unstable flavours. This process is suitable for imparting long shelf life to normally oxidation prone flavour compounds such as citrus oils.

Coacervation is particularly useful in connection with the use of high levels of loaded ingredient and is typically used for encapsulating flavour oils, fish oils, nutrients, vitamins, preservatives, enzymes. Coacervation requires the phase separation of one or many hydrocolloids from solution and the subsequent deposition of the newly formed coacervate phase around the mesoporous material which is suspended or emulsified in the same reaction media. The hydrocolloid shell may then be crosslinked using an appropriate chemical or enzymatic crosslinker if required.

When the capping layer includes elemental silicon, the amorphous silicon coating may be deposited by physical sputtering and may have a thickness of 500nm to 5μm. The silicon nanoparticles are preferably bound to the microparticles (e.g. silicon microparticles) by solution based techniques. The silicon nanoparticles typically possess a particle size distribution comparable to that of the mesopore particle size distribution of the microparticles.

There are various mechanisms by which the release of the loaded ingredient may be triggered. These are set out in (a) to (d) below.

(a) biodegradation

The capping layer may be degraded by enzymes or bacteria present at the intended site of use (active release). An example is starch degraded by salivary amylase for oral hygiene products.

(b) mechanical

The capping layer and, optionally, the microparticle may be degraded by mechanical forces at the intended site of use, such as forces exerted when brushing teeth or biting and chewing food.

(c) thermal

The capping layer may be degraded by a sudden increase of temperature such as exposure to body temperature (37°C) or boiling water (100⁰C).

(d ) chemical environment

The capping layer may be degraded by a change in the chemical environment, such as a pH change or immersion in a liquid such as milk. Compositions

The loaded mesoporous materials are suitable for use in foodstuff compositions and oral hygiene compositions.

(1) Food

For use in foodstuff compositions, the loaded ingredients may be selected from one or more of: oxygen sensitive edible oils; minerals; oxygen sensitive fats including dairy fats; oil soluble ingredients; vitamins; fragrances or aromas; flavours including salt and sugar (including one or more of glucose, sucrose, fructose); enzymes; probiotic bacteria; prebiotics; nutraceuticals; amino acids; herbal extracts; herbs; plant extracts; edible acids; antioxidants; therapeutic agents. Typically, the one or more ingredients are present in the range, in relation to the loaded material, of 0.01 to 90wt%, for example 1 to 40wt%, for example 20 to 55wt%, for example 20 to 50wt% (optionally in combination with about 70% porosity) and for example 2 to 10wt%.

The food may be in the form of a beverage or non-beverage. The food may be a dry food or a non-dry food. The dry food may be a food that does or does not normally come into contact with a liquid prior to ingesting. For example, a breakfast cereal is typically a dry food which normally comes into contact with a liquid prior to ingestion. Suitable foods for use in the present invention may comprise one or more of the following: meat; poultry; fish; vegetables; fruit; chocolate and confectionary including chewing gum; cereals and baked products including bread, cakes, biscuits, nutrition or cereal bars; pastry; pasta; dairy products such as milk, cream, butter, margarine, eggs, ice cream, cheese. The food may be in the form of any of the following: convenience meals; frozen food; chilled food; dried food; freeze dried food; rehydrated food; pickles; soups; dips; sauces.

Suitable beverages include alcoholic and non-alcoholic beverages. Particular examples of suitable drinks include: water, for example bottled water; tea; coffee; cocoa; drinking chocolate; fruit juices and smoothies; wine; beer; ales; lager; spirits. The beverages may, for example, be in the form of granules, including those which have been freeze dried, which are suitable for making instant coffee and tea and the like. As such, the present invention extends to products suitable for making beverages, such as instant beverage powders and granules. These include coffee granules, coffee powder, coffee tablets, tea, cocoa powder, chocolate powder. Other suitable products include coffee oil and concentrates, for example, fruit juice concentrates.

The pH of the food is preferably such that the mesoporous material does not dissolve in the food over a significant period of time and will thus afford an acceptable shelf-life. For example, for mesoporous silicon, the pH of the food is typically 2 to 6.

Fragrances, Aromas and flavours

Suitable fragrances, aromas and flavours are non-toxic and suitable for inclusion in foodstuffs. Bauer et al, "Common Fragrances & Flavours", Wiley, 1997, pp278 describes a range of suitable fragrances, aromas and flavours. Preferred fragrances, aromas and flavours are "Generally Recognised As Safe" (GRAS) by the FDA. Alcohols, aldehydes, ketones, esters and lactones are classes of compounds most frequently used in natural and artificial fragrances.

More specifically, suitable flavours (or flavouring agents) include: one or more of spice oleoresins derived from allspice, basil, capsicum, cinnamon, cloves, cumin, dill, garlic, marjoram, nutmeg, paprika, black pepper, rosemary and tumeric; essential oils such as anise oil, caraway oil, clove oil, eucalyptus oil, fennel oil, garlic oil, ginger oil, peppermint oil, onion oil, pepper oil, rosemary oil, spearmint oil; citrus oils including orange oil, lemon oil, bitter orange oil and tangerine oil; alliaceous flavours which include garlic, leek, chive, and onion; botanical extracts such as arnica flower extract, chamomile flower extract, hops extract, and marigold extract; botanical flavour extracts such as blackberry, chicory root, cocoa, coffee, kola, liquorice root, rose hips, sarsaparilla root, sassafras bark, tamarind and vanilla extracts; protein hydrolysates such as hydrolyzed vegetable protein (HVP's), meat protein hydrolyzates, milk protein hydrolyzates; natural and artificial compounded flavours which include those disclosed in S. Heath, Source Book of Flavours, Avi Publishing Co., Westport, Conn., 1981 , pp. 149-277. Particular flavour compounds are, for example: benzaldehyde, diacetyl (2,3- butanedione), vanillin, ethyl vanillin and citral (3,7-dimethyl-2,6-octadienal). The flavouring agent may be in the form of an oil, aqueous solution, non-aqueous solution or an emulsion. Flavour essences, i.e. the water soluble fraction derived from fruit or citrus can be utilized, and typically at lower levels than the ingredients mentioned above. With regard to fragrant oils, sustained release may be carried out using mesoporous silicon possessing a pore diameter in the range of about 2-1 Onm. The small pore size suppresses the release of the fragrant volatiles.

Particularly suitable food aromas (or aromatising agents) include food aromas for liquid food products, particularly instant soups and beverages such as coffee. Other suitable food aromas include those used in desserts such as instant puddings, and frozen food products such as frozen pizza. The food aromas may also be those suitable for use in food which needs to be reconstituted with hot water or milk or heated by the consumer prior to consumption. Suitable food aromas include the following: cheese aroma; aromas for hot soluble coffee-based beverages such as coffee, hazelnut, amaretto, chocolate, cream and vanilla; aromas for hot soluble tea-based beverages such as raspberry, cream and vanilla; aromas for hot cocoa-based beverages such as raspberry, amaretto, cream, chocolate and vanilla; aromas for hot soups such as mushroom, tomato, beef and chicken; aromas for beverages such as coffee, tea, cherry, grape, and strawberry; aromas for dessert products such as raspberry, chocolate, butterscotch, cherry, grape, strawberry, banana, and vanilla; aromas for other products such as cream, seafood, meat, garlic and onion. The aroma flavour may be part of an aromatizing composition which may optionally also include one or more other constituents such as a non-volatile edible fat or oil, a surfactant, a wetting agent, a foaming agent, an extremely volatile solvent, a propellant, dissolved edible solids, an antioxidant, or an aroma precursor. The total amount of such additional constituents will preferably not usually be more than about 40% by weight, based on the total weight of the mesoporous material and aroma constituents. Suitable non- volatile edible fats or oils include coffee oil or triglyceride oils used as a source of flavour or as a flavour solvent. A surfactant may also be present which acts as a spreading agent or ernulsifier to control the droplet size of the aromatizing composition and its degree of spreading on the surface of a food product. Suitable highly volatile solvents such as acetone and acetaldehyde may be used as a co-solvent for the volatile food aroma and modify the rate of evaporation of the aroma delivery system. A dissolved or entrapped propellant gas such as air, nitrogen, carbon dioxide, nitrous oxide, or a gas generator such as a chemical carbonation reagent, may be included to increase buoyancy or to accelerate aroma release and evaporation. Dissolved edible solids increase the viscosity of the composition. Antioxidant additives such as butylated hydroxyanisole, butylated hydroxyl toluene, tertiary butylhydroquinone, vitamins A, C and E and derivatives, and various plant extracts such as those containing carotenoids, tocopherols or flavonoids having antioxidant properties, may be included to increase the shelf-life of the aromatized carrier. Aroma precursors that would not react during storage but would react to generate aroma during food preparation may also be included in the aromatizing composition.

The production of dehydrated food compositions often involves processing conditions such as elevated temperature, which often causes loss of desirable food aroma. One known technique of overcoming such loss is to add additional aroma and flavour to dehydrated foodstuffs and beverages. Such aromas and flavours are usually complex, comprising many organoleptically active compounds, which combine to create the characterizing aroma of the product. Since aromas and flavours are often extremely powerful and unstable in their undiluted state, they are combined with a carrier to render them more stable and easier to handle. The carriers are preferably neutral or complementary in organoleptic impact and do not contribute to the characterizing aroma of the product. Desirable characteristics of carriers for liquid systems include blandness and miscibility with other liquid carriers and with liquid aromas. Traditional carriers include ethanol, propylene glycol, glycerol, vegetable oil, benzyl alcohol, triacetin, thpropionin, triethyl citrate, and tributyrin.

Oxygen sensitive edible oils

Oxygen sensitive edible oils include polyunsaturated fatty acids which themselves include canola oil, borage oil, evening primrose oil, safflower oil, sunflower oil, pumpkinseed oil, rosemary oil, rice bran oil, flaxseed oil, wheatgerm oil, grapeseed oil, linseed oil. Some of these oils contribute linoleic acid, alpha-linoleic acid, oleic acid, palmitic acid, stearic acid. Also included are marine oils, for example, those derived from fish such as tuna, herring, mackerel, sardine, cod liver and shark.

Minerals and trace elements

Suitable minerals include: macrominerals comprising Ca, P, Mg, Na, K; microminerals comprising Fe, Zn, Cu, Se, Cr, I, Mn, Mo, F. Suitable trace elements include Ni, V, B, Co. Vitamins

Suitable vitamins include Ascorbic Acid, Beta-carotene, Biotin, Choline, Folic Acid, Niacin, Pantothenic Acid (Vitamin B5), Phylloquinone (Vitamin K), Pyridoxine (Vitamin B6), Riboflavin (Vitamin B2), Thiamin (Vitamin B1 ), Vitamin A, Vitamin B12, Vitamin D, Vitamin E and mixtures thereof. The vitamin and mesoporous material may be combined by allowing the vitamin to impregnate the mesoporous material, optionally in the presence of gentle heat, typically in the range of 4O⁰C and 200⁰C.

Enzymes

Suitable enzymes are selected from the classes of carbohyd rases, pectic enzymes, celluloses, proteases, oxidases, and lipases. Examples include amylase, bromelain, catalase, ficin, glucoamylase, glucose isomerase, glucose oxidase, invertase, lactase, lipase, papain, pepsin, pullulanase and rennet.

Prebiotics

A prebiotic is a natural or synthetic substance that supports the growth of and/or nurtures probiotics. More specifically the prebiotic is a nondigestible food ingredient that beneficially affects the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon. They are typically carbohydrates of relatively short length. Examples are the inulin-type fructans such as lactulose and inulin.

Nutraceuticals

A nutraceutical ingredient provides medical or health benefits, including the prevention and treatment of disease. In general, a nutraceutical is specifically adapted to confer a particular health benefit on the consumer. Suitable nutraceuticals for use in the present invention may be selected from Aloe Vera (Aloe ferox, A. barbadensis), Artichoke, Asian Ginseng (Panax ginseng), Astragalus, Bee Pollen, Bilberry (Vaccinium myrtillus), Black Cohosh, Capsicum-Cayenne, Hot Pepper (Capsicum species), Cascara Sagrada (Rhamnus purshiana), Cat's Claw (Uncaria tomentosa), Chamomile (Matricaria recutita), Cranberry, Dandelion (Taraxacum officinale), Donq Quai (Angelica sinensis), Echinacea (Echinacea purpurea and related species), Evening Primrose Oil (Oenothera biennis), Feverfew (Tanacetum parthenium), Fructo-oligosaccharides, Garlic (Allium sativum), Ginger (Zingiber officinale), Ginkgo (Ginkgo biloba), Ginseng, Glucarate, Glucosamine, Goldenseal (Hydrastis canadensis), Gotu Kola (Centella Asiatica), Grape Seed Extract, Green Tea, Guarana (Paullinacupana), Hawthorne (Crataegus oxyacantha), Inositol, Inulin, Isoflavones, Kava Kava (Piper methysticum), L-carnitine, Lecithin, Licorice (Glycyrrhiza glabra and G. uralensis), Lycopene, Milk Thistle (Silybum marianum), Mod. Citrus Peel, Nettles, Oligofructose, 0mega-3s, Passiflora, Passion Flower (Passiflora incarnata), Pau d'Arco, (Tabebuia impetiginosa), Peppermint (Mentha piperita), Phospholipids, Polyphenol, Psyllium (Plantago ovata and P. Major), Pycnogenol, Queroetin D-llmonene, Reishi, Ribonucleic Acid, Royal Jelly, St. John's Wort (Hypericum perforatum), Saw Palmetto (Serenoa repens; Sabal serrulata), Schisandra, Soybean Isoflavones, Tumeric Valerian (Valeriana officinalis) and mixtures thereof.

Amino acids

Suitable amino acids may be selected from Alanine, Arginine, Aspartic Acid,

Asparagine, Carnitine, Cysteine, Cystine, Glutamic Acid, Glutamine, Glutathione,

Glycine, Histidine, Isoleucine, Leucine, Lysine, Methionine, Ornithine, Phenylalanine, Proline, Serine, Taurine, Threonine, Tryptophan, Tyrosine, Valine and mixtures thereof.

Plant extracts and herbs

Suitable plant extracts include one or more plant sterols, these include beta-sitosterol, campesterol, stigmasterol. Suitable plant stands include sitostanol, octacosanol, policosanol.

Suitable herbs include black walnut, burdock, chamomile, comfrey, Echinacea, eucalyptus, hawthorn, hyssop, ginkgo, hyssop, lemon balm, milk thistle, mullein, peppermint, psyllium, sage, saw palmetto, sheep sorrel, slippery elm, St John's Wort, thyme, turkey rhubarb, valerian, vitex.

Herbs suitable for use for medicinal purposes are described in The Natural Pharmacy by M. Polunin & C. Robbins (Dorling Kindersley 1999), 144pp. In particular, pages 30 -131 list suitable herbs. Suitable culinary herbs are described in Food Commodities, 2nd Edition pp158-163 by B. Davis (Butterworth Heinemann 1994). Edible acids

Suitable edible acids for use in the present invention may be selected from citric acid, ascorbic acid, malonic acid, acetic acid, tartaric acid, sorbic acid, fumaric acid, malic acid, phosphoric acid, succinic acid and nicotinic acid.

Antioxidants

Suitable antioxidants for use in the present invention may be selected from sodium carbonate, calcium carbonate, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), lecithins, sodium lactate, calcium lactate, calcium malate and ammonium citrate.

Food preparation

Methods for incorporating the mesoporous material into food are numerous. Typically, the mesoporous material is loaded with the at least one ingredient prior to incorporating the mesoporous material into the food. Suitable mixing equipment for use in the present invention is diverse and includes, for example, screw mixers, ribbon mixers and pan mixers. Other examples include high speed propeller or paddle mixers for liquid food or beverages; tumble mixers for dry powders; Z-blade mixers for doughs and pastes. Suitable grinding machines include hammer, disc, pin and ball millers. Extrusion is an important very high throughput (about 300-9000kg/hr) technique for mixing and providing shape to foodstuffs and is suitable for use in the present invention. Cold and hot extruders may be used. These can be single or twin screw. Extruded foods include cereals, pasta, sausages, sugar or protein based products.

The loading levels can be determined by dividing the volume of the ingredient taken up during loading (equivalent to the mass of the ingredient taken up divided by its density) by the void volume of the mesoporous material prior to loading multiplied by one hundred.

The total quantity of mesoporous material present in the food, based on the weight of the composition according to the present invention, may be about 0.01 to 50wt%, for example about 0.01 to 20wt% and for example about 0.1 to 5wt%. (2) Oral Hygiene Compositions

The loaded mesoporous material may be used in an oral hygiene composition such as a mouthwash or a dentifrice composition such as a toothpaste, tooth powder, lozenge, or oral gel. It may be present as an abrasive in addition to delivering one or more ingredients. The dentifrice composition will comprise constituents well known to one of ordinary skill; these may broadly be characterised as active and inactive agents. Active agents include anticahes agents such as fluoride, antibacterial agents, desensitising agents, antitartar agents (or anticalculus agents) and whitening agents. Inactive ingredients are generally taken to include water (to enable the formation of a water phase), detergents, surfactants or foaming agents, thickening or gelling agents, binding agents, efficacy enhancing agents, humectants to retain moisture, flavouring, sweetening and colouring agents, preservatives and, optionally further abrasives for cleaning and polishing. The oral gel may be of the type suitable for use in multi-stage whitening systems.

Suitable mesoporous particulate materials for use in toothpaste include silicon and silica.

Water phase

The dentifrice composition typically comprises a water-phase which comprises an humectant. Water may be present in an amount of from about 1 to about 90wt%, preferably from about 10 to about 60wt%. Preferably, the water is deionised and free of organic impurities. Any of the known humectants for use in dentifrice compositions may be used. Suitable examples include sorbitol, glycerin, xylitol, propylene glycol. The humectant is typically present in an amount of about 5 to 85wt% of the dentifrice composition.

Anticaries agent

The dentifrice composition according to the present invention may comprise an anticaries agent, such as a source of fluoride ions. The source of fluoride ions should be sufficient to supply about 25ppm to 5000ppm of fluoride ions, for example about 525 to 1450ppm. Suitable examples of anticaries agents include one or more inorganic salts such as soluble alkali metal salts including sodium fluoride, potassium fluoride, ammonium fluorosilicate, sodium fiuorosilicate, sodium monofluorophosphate, and tin fluorides such as stannous fluoride.

Antitartar agents

Any of the known antitartar agents may be used in the dentifrice compositions according to the present invention. Suitable examples of antitartar agents include pyrophosphate salts, such as dialkali or tetraalkali metal pyrophosphate salts, long chain polyphosphates such as sodium hexametaphosphate and cyclic phosphates such as sodium trimetaphosphate. These antitartar agents are included in the dentifrice composition at a concentration of about 1 to about 5wt%.

Antibacterial agents

Any of the known antibacterial agents may be used in the compositions of the present invention. For example, these include non-cationic antibacterial agents such as halogenated diphenyl ethers, a preferred example being triclosan (2,4,4'-trichloro-2'- hydroxydiphenyi ether). The antibacterial agent(s) may be present in an amount of about 0.01 to 1.0wt% of the dentifrice composition, for example about 0.3wt%.

Other abrasive agents

The mesoporous material can be used as the sole abrasive in preparing the dentifrice composition according to the present invention or in combination with other known dentifrice abrasives or polishing agents. Commercially available abrasives may be used in combination with the mesoporous material and include silica, aluminium silicate, calcined alumina, sodium metaphosphate, potassium metaphosphate, calcium carbonate, calcium phosphates such as tricalcium phosphate and dehydrated dicalcium phosphate, aluminium silicate, bentonite or other siliceous materials, or combinations thereof.

Flavours

The dentifrice composition of the present invention may also contain a flavouring agent. Suitable examples include essential oils such as spearmint, peppermint, wintergreen, sassafras, clove, sage, eucalyptus, majoram, cinnamon, lemon, lime, grapefruit, and orange. Other examples include flavouring aldehydes, esters and alcohols. Further examples include menthol, carvone, and anethole. Advantageously, the flavour may be delivered over a prolonged period of time.

Thickening agents

The thickening agent may be present in the dentifrice composition in amounts of about 0.1 to about 10% by weight, preferably about 0.5 to about 4% by weight. Thickeners used in the compositions of the present invention include natural and synthetic gums and colloids, examples of which include xanthan gum, carrageenan, sodium carboxymethyl cellulose, starch, polyvinylpyrrolidone, hydroxyethylpropyl cellulose, hydroxybutyl methyl cellulose, hydroxypropylmethyl cellulose, and hydroxyethyl cellulose. Suitable thickeners also include inorganic thickeners such as amorphous silica compounds including colloidal silica compounds.

Surfactants

Surfactants may be used in the compositions of the present invention to achieve increased prophylactic action and render the dentifrice compositions more cosmetically acceptable. The surfactant is typically present in the dentifrice compositions according to the present invention in an amount of about 0.1 to about 5wt%, preferably about 0.5 to about 2wt%. The dentifrice compositions according to the present invention may comprise one or more surfactants, which may be selected from anionic, non-ionic, amphoteric and zwitterionic surfactants. The surfactant is preferably a detersive material, which imparts to the composition detersive and foaming properties. Suitable examples of surfactants are well known to an ordinary skilled person and include water-soluble salts of higher fatty acid monoglycehde monosulfates, such as the sodium salt of the monosulfated monoglyceride of hydgrogenated coconut oil fatty acids, higher alkyl sulfates such as sodium lauryl sulfate, alkyl aryl sulfonates such as sodium dodecyl benzene sulfonate, higher alkyl sulfoacetates, sodium lauryl sulfoacetate, higher fatty acid esters of 1 ,2-dihydroxy propane sulfonate, and the substantially saturated higher aliphatic acyl amides of lower aliphatic amino carboxylic acid compounds, such as those having 12 to 16 carbons in the fatty acid, alkyl or acyl radicals. Further examples include N-lauroyl sarcosine, and the sodium, potassium, and ethanolamine salts of N-lauroyl, N-myristoyl, or N-palmitoyl sarcosine. Efficacy enhancing agents

One or more efficacy enhancing agents for any antibacterial, antitartar or other active agent within the dentifrice composition may also be included in the dentifrice composition. Suitable examples of efficacy enhancing agents include synthetic anionic polycarboxylates. Such anionic polycarboxylates may be employed in the form of their free acids or partially, or more preferably, fully neutralized water soluble alkali metal

(e.g. potassium and preferably sodium) or ammonium salts. Preferred are 1 :4 to 4:1 copolymers of maleic anhydride or acid with another polymerizable ethylenically unsaturated monomer, preferably methylvinylether/maleic anhydride having a molecular weight (M.W.) of about 30,000 to about 1 ,800,000.

When present, the efficacy enhancing agent, for example the anionic polycarboxylate, is used in amounts effective to achieve the desired enhancement of the efficacy of any antibacterial, antitartar or other active agent within the dentifrice composition. Generally, the anionic polycarboxylate(s) are present within the dentifrice composition from about 0.05wt% to about 4wt%, preferably from about 0.5wt% to about 2.5wt%.

Other Ingredients

Various other materials may be incorporated in the dentifrice compositions of this invention, including: preservatives; silicones; desensitizers, such as potassium nitrate; whitening agents, such as hydrogen peroxide, calcium peroxide and urea peroxide; and chlorophyll compounds. Some toothpastes include bicarbonate in order to reduce the acidity of dental plaque. These additives, when present, are incorporated in the dentifrice composition in amounts which do not substantially adversely affect the desired properties and characteristics.

Preparation of the dentifrice composition

Suitable methods for making the dentifrice compositions according to the present invention include the use of high shear mixing systems under vacuum. In general, the preparation of dentifrices is well known in the art. US 3980767, US 3996863, US 4358437, and US 4328205, the contents of which are hereby incorporated by reference in their entirety, describe suitable methods for making dentifrice compositions. For example, in order to prepare a typical dentifrice composition according to the present invention, an humectant may be dispersed in water in a conventional mixer under agitation. Organic thickeners are combined with the dispersion of humectant along with: any efficacy enhancing agents; any salts, including anticaries agents such as sodium fluoride; and any sweeteners. The resultant mixture is agitated until a homogeneous gel phase is formed. One or more pigments such as titanium dioxide may be combined with the gel phase along with any acid or base required to adjust the pH. These ingredients are mixed until an homogenous phase is obtained. The mixture is then transferred to a high speed/vacuum mixer, wherein further thickener and surfactant ingredients may be combined with the mixture. Any abrasives may be combined with the mixture to be used in the composition. Any water insoluble antibacterial agents, such as triclosan, may be solubilized in the flavour oils to be included in the dentifrice composition and the resulting solution is combined along with the surfactants with the mixture, which is then mixed at high speed for about 5 to 30 minutes, under vacuum of from about 20 to 50mm of Hg. The resultant product is typically an homogeneous, semi-solid, extrudable paste or gel product.

The pH of the dentifrice composition is typically such that the mesoporous material will not dissolve in the composition over a significant period of time and will thus afford an acceptable shelf-life. The pH of the dentifrice composition is typically less than or equal to about 9 and preferably, particularly for compositions other than powders such as toothpastes, less than or equal to about 7. The lower limit of pH may typically be about 3.5 or about 4. In particular, the pH may be about 3.5 or about 4 when the dentifrice composition is a gel, such as those used in multi-stage whitening systems.

The abrasivity of the dentifrice compositions of the present invention can be determined by means of Radioactive Dentine Abrasion (RDA) values as determined according to the method recommended by the American Dental Association, as described by Hefferren, J. Dental Research, vol. 55 (4), pp 563-573, (1976) and described in US 4340583, US 4420312 and US 4421527, the contents of which are contained herein by reference in their entirety. In this procedure, extracted human teeth are irradiated with a neutron flux and subjected to a standard brushing regime. The radioactive phosphorus 32 removed from the dentin in the roots is used as the index of the abrasion of the dentifrice tested. A reference slurry containing 10g of calcium pyrophosphate in 15 ml of a 0.5% aqueous solution of sodium carboxymethyl cellulose is also measured and the RDA of this mixture is arbitrarily taken as 100. The dentifrice composition to be tested is prepared as a suspension at the same concentration as the pyrophosphate and submitted to the same brushing regime. The RDA of the dentifrice compositions according to the present invention may lie in the range of about 10 to 150, for example less than about 100, for example, less than about 70.

The pellicle cleaning ratio (PCR) of the dentifrice compositions of the present invention is a measurement of the cleaning characteristics of dentifrices and generally may range from about 20 to 150 and is preferably greater than about 50.

The PCR cleaning values can be determined by a test described by Stookey et al., J. Dental Research, vol. 61 (11 ), pp 1236-9, (1982). Cleaning is assessed in vitro by staining 10mm² bovine enamel specimens embedded in resin, which are acid etched to expedite stain accumulation and adherence. The staining is achieved with a broth prepared from tea, coffee and finely ground gastric mucin dissolved into a sterilized trypticase soy broth containing a 24-hour Sarcina lutea turtox culture. After staining, the specimens are mounted on a V-8 cross-brushing machine equipped with soft nylon toothbrushes adjusted to 15Og tension on the enamel surface. The specimens are then brushed with the dentifrice composition to be tested and a calcium pyrophosphate standard which comprises 10g of calcium pyrophosphate in 50 ml of 0.5% aqueous solution of sodium carboxymethyl cellulose. The specimens are brushed with dentifrice slurries consisting of 25g of toothpaste in 4Og of deionized water, for 400 strokes. The specimens are cleaned with Pennwalt pumice flour until the stain is removed. Reflectance measurements are taken using a Minolta Colorimeter using the standard Commission Internationale de I'Eclairage (CIE) L^* a^* b^* scale in order to measure the colour of the specimens before and after brushing.

The cleaning efficiency of the dentifrice compositions according to the present invention, which is a measure of the ratio of PCR/RDA, may lie in the range from about 0.5 to about 2.0, and may be greater than about 1.0 for example greater than about 1.5.

The use of the mesoporous microparticulate material in an oral hygiene composition provides increased efficacy (e.g. through increased antimicrobial activity). Exampies

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

Example 1.

Mesoporous calcium phosphate powder is loaded with a mixture of lemon and lime flavour oils by the "mop up" technique. Preferably, the calcium phosphate surfaces have known hydroxyapatite binding activity and remineralizing activity. The oil is gradually mixed into the powder with continuous stirring at room temperature and pressure in ambient air. Further oil addition is terminated before the "wet point" is reached where the mesopores are filled and residual oil adheres to the exterior surfaces of the microparticles. The flavoured particles are added to toothpaste formulations at the 1-10wt% level. During brushing a fraction of these particles adhere to the tooth enamel surfaces and all particles contribute to a burst release of flavour. During mouth rinsing the majority of the particles are removed but retained particles provide sustained release of flavour in the mouth.

Example 2.

Mesoporous starch particles are packed into glass columns through which aqueous solutions of xyϋtol are flowed. Preferably, the starch has a mesoporosity above 70% and all of the pores are less than 75nm in diameter. Solution transport is continued until excess xylitol is detectable at the exit point of the stacked column. The sweetened starch composition is then added to ice cream formulations at 5-25wt% and co-frozen. The xylitol remains in an amorphous form within the frozen ice cream. Upon ingestion and contact with saliva, the exothermic heat of solvation contributes to a melt in the mouth sensation.

Example 3.

Mesoporous silica is loaded with salt by heating appropriate mixtures to above the melting point (801 "C) in high temperature ovens. Preferably, the mesoporous silica particles have diameters, e.g. d₅₀ diameters, in the range 5-15μm, more preferably d₅₀ diameters in the range 1-1 Oμm and may have hydrophillic surfaces. The salt loaded microparticles are applied to the surfaces of dry snack products, such as Doritos™, at the 0.001 -0.1 wt% level. Upon ingestion and direct contact with the tongue, there is burst and sustained release of salt in the immediate vicinity of salt taste receptors.

Example 4.

Mesoporous silicon is loaded with a nutritional essential oil with a bitter taste by the mop up technique. Preferably, the mesoporous silicon is prepared by partial reduction of porous silica using magnesium vapour, has a pale brown colour, and takes up more than 30wt% oil. The oil loaded microparticles are then capped with a hydrophobic pigment such as turmeric by, for example, spray drying. The capped microparticles have an orange hue and disperse readily in orange juice. Upon ingestion of the beverage the bitter taste of the oil is completely masked. The nutritional oil is partly released in the stomach but the majority is released in the intestine as a result of the biodegradation of the carrier material.

Example 5.

Saturated solutions of salt were prepared with de-ionized water (15.7MΩcm) and a commercially available brand of table salt (containing sodium hexacyanoferrate Il anti- caking agent), equivalent to 3g/10ml at 21⁰C (3g of table salt was made up to 10ml of salt solution).

Mesoporous oxidized silicon powders with a porosity of 70%, a d₅₀ of 6μm and a d₉₀ of 19μm were prepared from anodized membranes by rotary-milling and then sedimentation filtration. The powders were oxidized for 3hrs at 800⁰C in air to render them hydrophilic and manipulate their colour to off-white.

Stain etched oxidized mesoporous silicon powders were prepared by an etching process. The powders had a d₅₀ of 2μm and a d₉₀ of 9μm. The porosified surface area was 381.3 m²/g and the pore volume was 0.496 ml/gm. The powders were oxidized for 0.5 hrs at 700⁰C and were dark brown in colour.

A "mop-up" technique was used to load salt into the oxidized porous silicon powders. The mop-up technique used repeated adsorption of volumes of liquid below the "wet point" where mesopores become full and microparticle "dumping" starts to occur. 900mg batches of oxidized mesoporous silicon powder were spread evenly over glass Petri plates. 0.5ml of salt solution (0.3g/ml) at a time was pipetted onto the powder and was mixed thoroughly at ambient temperature. The Petri dish was then transferred to a hot plate at 90⁰C to remove water. Salt solution addition and drying was repeated until the targeted wt% loading was achieved (the increasing weight of the powder was monitored). Both the anodized oxidized and stain etched oxidized silicon powders were loaded (54.5wt%) with salt.

A snack mix was manually coated with first a thin layer of oil and then either the salted mesoporous powders or micronized salt powder, using a simple spray bottle (oil), sprinkler (salt) and mixing bowl. The coated samples were stored at room temperature in plastic bags until use. After coating the snacks, the level of salt present on each snack was 0.4wt%.

Taste tests were run on the snacks which had been treated with the micronized salt and the loaded mesoporous silicon samples. The results indicated that there was an increased saltiness for both the anodized and the stain etched samples when compared to the micronized salt sample. When the anodized and stain etched samples were compared, the stain etched sample gave a saltier taste. These results indicate that the use of the mesoporous materials increased the perception of saltiness as did the use of the smaller mesoporous silicon microparticles when compared with the larger mesoporous silicon microparticles.

Example 6.

Saturated solutions of salt were prepared with de-ionised water (15.7MΩcm) and a commercially available brand of table salt (containing sodium hexacyanoferrate Il anti- caking agent), equivalent to 29.6g/100ml at 21⁰C (29.6g of table salt was made up to 100ml of salt solution).

Mesoporous silicon model structures (membranes) and mesoporous silicon powders were prepared with various porosities and pore volumes. The powders were prepared from the membranes by hand-milling with a mortar and pestle. The membranes and powders were oxidized (0.5hr at 600°C, in air) to render them hydrophilic, such that the aqueous salt solution rapidly and easily permeated the porous network. The oxidation process reduced the available porosity/pore volume and this was taken into account when calculating loading levels.

Loading of salt in oxidized porous silicon membranes was performed at ambient temperature and pressure by immersing each membrane completely in solution for

15min. On removal, the excess solution on the outer surface of each membrane was soaked up through contact with Whatman filter paper. Residual surface deposits were not visually apparent. Each membrane was then dried on a hotplate at 45⁰C (open air) to remove residual water from the pores and leaving only salt within the structure. Mass measurements were performed before, during, and after loading on a Mettler-

Toledo microbalance. These measurements were used to determine the percentage loading.

Experiments on membranes highlighted that the majority of water was dried off after 1 hr, although a further 1-2hrs was required for higher porosity structures, where the water payload is higher. Likewise, when water-release profiles were determined, the structures were completely dried before gravimetric analysis.

Loading of salt in the oxidized mesoporous silicon powders was carried out by charging individual Ultrafree-MC centrifugal filters (0.45μm pore diameter polyvinylidine fluoride -

PVDF membrane) with powder, mounting these in 1 ml polypropylene Eppendorf tubes and filling with 0.5ml salt solution. After 30min, the samples were centrifuged at

16,30OG (13,300rpm), twice over a 2min period, to spin-filter the solution. The powders were removed and further dried on a hotplate at 45⁰C for 4hr. The mass was measured before and after loading.

The release kinetics of salt into deionised water was evaluated for two model (membrane) oxidized porous silicon structures of different porosities. After loading, the membranes were immersed in the water for a set time, removed and dried as described previously. The weight loss, attributed to leaching of the salt, was monitored for different immersion times, to determine the release profiles (percentage loading versus time).

Tables 1 and 2 illustrate that the payload increased with increasing available porosity. Tabie 1 : Variation in NaCI payload with porosity of oxidised mesoporous silicon membranes (solution loading)

Table 2: Variation in NaCI payload with porosity of oxidised mesoporous silicon powders (solution loading)

It was noted that the very high surface area entrapped salt powder, once dried, was a free flowing powder with a pale brown colour. X-ray diffraction studies showed that very high surface area salt was present predominantly in nanocrystalline form and situated in pores of 5nm to 20nm in diameter.

The release profiles for NaCI-loaded oxidised (60% porosity) mesoporous silicon into de-ionised water indicated that the porous silicon retained NaCI up to about 4 minutes after immersion. This was higher than when compared to the 43% porosity mesoporous silicon. This release profile indicates the suitability of the material for use in foods which are exposed to liquids before they are ingested such as cereals to which a liquid such as milk may be added.

Example 7.

Taste tests were conducted on mesoporous silicon samples. These samples were prepared by preparing a 36μm thick mesoporous silicon film of 79% porosity which was oxidized for 1 hour at 500⁰C. The wafers were cleaved to yield a number of 1 cm x 1 cm squares. A control non-porous silicon wafer was cleaved to yield a number of 1 cm x 1cm squares. Salt solutions were prepared in deionized water and pipetted onto the silicon surfaces. The liquid was evaporated (few minutes on a hotplate at 60⁰C, followed by gentle heating).

In taste tests, a majority of the tasters could detect 1.25μg of salt loaded in mesoporous silicon. None of the tasters could detect a 2.5μg surface deposit of salt on non-porous silicon and only one taster could detect 12.5μg on non-porous silicon. All of the tasters were confirmed to fall within the normal population ranges for salt tasting ability.

Example 8.

The Maillard reaction of Alpha D glucose, when nanoentrapped within mesoporous silica, was compared with Alpha D Glucose in free powder form. Two 1 g batches of glucose were simultaneously heated to 200°C +/- 10°C for 10 minutes in air, one as a free flowing dry powder, prepared by mixing molten glucose with 1g Syloid 74FP mesoporous silica (WR Grace Davison GmbH) at 185⁰C, the other as molten glucose mass. Much more intense caramel aromas were evident from the dry powder during heating. After the heating period, the molten glucose mass was mixed with a similar 1g batch of Syloid. Both Syloid/glucose batches were then hand ground by a pestle and mortar. Samples were tasted by placing 50mg aliquots on the tongue. The sample with glucose that was heat treated whilst entrapped in mesoporous silica, had a light brown colouration and a pleasant caramel aroma and flavour. The sample with glucose that was heat treated prior to contact with mesoporous silica had a caramel flavour with bitter notes. The taste of the two batches was clearly distinguishable as a result of sugar nanoentrapment. The experiment was repeated, but for a common heat treatment of 75 minutes at 200⁰C. The sample with glucose that was heat treated whilst nanoentrapped in mesoporous silica, had a darker brown coloration, but did not have a significantly stronger caramel flavour. The sample with glucose that was heat treated prior to contact with mesoporous silica had a caramel flavour with stronger bitter notes. Example 9

Starch microparticles containing mesopores were prepared by a modification of the techniques described in "Carbonized starch microcellular foam-cellulose fiber composite structures" by Rutlidge et al in BioResources 3(4), 1063-1080, (2008).

The process involved the thermal treatment of an aqueous starch solution followed by dehydration with ethanol. The ethanol dehydration is carried out in successive water baths containing different v/v percentages of ethanol. The final dehydration step involved immersion of starch in absolute ethanol followed by vacuum drying at ambient temperature. This results in porous starch particles with an open-cell matrix with pore sizes in the sub-micrometer range. 5Og of cornstarch was mixed into one litre of deionized water and then heated to 12O⁰C for 45 minutes. The viscous solution was poured into moulds and then stored at 4°C for 12 hours. The aquagels were then bathed for 2 hours in 10% ethanol solution, 2 hours in 20% ethanol solution and 2 hours in 30% ethanol solution, followed by a final 10 hour soak in 100% ethanol.

Incorporation of flavour oil into a solid matrix is regarded as a means of formulating liquid compounds in a solid dosage form such as bouillon cubes. This can have an application in soup based products with extended aroma release. A model flavour compound, ginger oil, was incorporated at the 50wt% level using the mop up technique described in Example 1. At 8O⁰C, sufficient oil was retained within the mesopores of the starch for the aroma to persist for longer than 1 hour in the headspace above the powder.

Claims

CLAiMS

1. Use of a mesoporous material for modifying the flavour and/or texture of a foodstuff composition or an oral hygiene composition wherein at least some of the pores of the mesoporous material are loaded with at least one ingredient.

2. Use of a mesoporous material according to claim 1 , wherein the composition is a foodstuff composition.

3. Use of a mesoporous material according to claim 1 , wherein the composition is an oral hygiene composition.

4. Use according to any one of the previous claims, wherein the mesoporous material is selected from mesoporous silicon, mesoporous silica, mesoporous calcium phosphate, mesoporous metal carbonate, mesoporous alumina, mesoporous carbon, mesoporous vegetable material, mesoporous starch, mesoporous titania, mesoporous silicate, mesoporous polymer.

5. Use according to claim 4, wherein the mesoporous material is selected from elemental silicon.

6. Use according to claim 5, wherein the silicon comprises, consists of, or consists essentially of surface modified mesoporous silicon.

7. Use according to claim 6, wherein the surface modified silicon comprises, consists of, or consists essentially of, one or more of derivatised mesoporous silicon, partially oxidised mesoporous silicon, mesoporous silicon modified with silicon hydride surfaces.

8. Use according to any one of the previous claims wherein the at least one ingredient is present in an amount of 0.01 to 90wt% in relation to the weight of the loaded mesoporous material.

9. Use according to any one of the previous claims, wherein the at least one ingredient is retained in an amorphous state.

10. Use according to any one of the previous claims, wherein the material is a mesoporous microparticulate material.

11. Use according to any one of the previous claims, wherein the loaded ingredient is released on contact or shortly after contact with the human or animal tongue.

12. Use according to any one of the previous claims, wherein the mesoporous material consists of, consists essentially of, or comprises particles possessing a diameter of about 5 to 15μm.

13. Use according to the previous claim, wherein the at least one loaded ingredient is salt and/or sugar.

14. Use according to any one of the previous claims, wherein the mesoporous material is encapsulated by a capping layer.

15. Use according to the previous claim, wherein the capping layer is 0.1 to 50μm thick.

16. Use according to the previous claim, wherein the capping layer is 0.5 to 45μm thick.

17. Use according to any one of claims 14 to 16, wherein the capping layer is selected from one or more of titanium dioxide, carageenan, xanthum gum, cellulose gum, tocopherol, cocoa butter, vegetable fat, milk fat, lecithin, glyceryl oleate, seed oil, cyclopentasiloxane, paraffin.

18. Use according to any one of claims 14 to 16, wherein the capping layer comprises, or consists of, or consists essentially of one or more of a carbohydrate, gum, lipid, protein, cellulose, polymer, elastomer, inorganic material.

19. Use according to any one of the previous claims, wherein the potency of the at least one ingredient is increased.

20. Use according to any one of claims 1 to 18, wherein the taste of the at least one ingredient is masked.