Patent Application
20130280396
The present invention relates to an instant beverage powder and, more particularly, to an instant soluble beverage powder which forms foam on its upper surface when reconstituted with water.
In general, instant beverages are used to describe products such as tea, coffee or the like which are sold in a form that is easily reconstitutable with water to form a drink. Such beverages are typically in solid form and are readily soluble in hot water.
Instant soluble coffee is a phrase used to describe coffee which has been prepared by extraction of roast and ground coffee followed typically by reconstitution of the extract into a powdered product by conventional means such as freeze-drying, spray-drying or the like.
In order to prepare a beverage, hot water is then simply added to the powder thus avoiding the complicated and time-consuming process which is involved when preparing a beverage from traditional roast and ground coffee.
However, unlike coffee beverages prepared from roast and ground coffee, those prepared from instant soluble coffee do not usually exhibit a fine foam on their upper surface when reconstituted with hot water.
The foamed upper surface in beverages prepared from roast and ground coffee are typically associated with and caused, at least in part, by the machines which brew with pressurised water and/or steam.
This foam is known to positively affect the mouthfeel of the product when consumed and so is highly desired by many consumers. Furthermore, the foam acts to keep more of the volatile aromas within the beverage so that they can be appreciated by the consumer rather than lost to the surrounding environment.
Nevertheless, instant beverages such as instant soluble coffee are not suited for use with roast and ground coffee brewing apparatus and so the solution for foaming the beverage derived from roast and ground coffee is not readily applicable to instant beverages.
Instead, the foam must be generated by simple admixing of the instant beverage product and a liquid.
U.S. Pat. No. 6,713,113 discloses a powdered soluble foaming ingredient which has a matrix containing a carbohydrate, a protein and entrapped pressurized gas. The gas is released upon addition of the dry powder to liquid.
U.S. Pat. No. 4,830,869 and U.S. Pat. No. 4,903,585, both to Wimmers, et al. disclose a method for making a coffee beverage having a thick layer of foamed coffee on its surface, similar in appearance to cappuccino coffee. A measured amount of spray-dried instant coffee and a small amount of cold water are combined with vigorous agitation to form a foamed coffee concentrate. Then, hot water is added to make a coffee beverage.
U.S. Pat. No. 4,618,500 to Forquer discloses a method for preparing a brewed espresso-type coffee beverage which has froth on the surface of the beverage. Steam is injected into the brewed coffee beverage to produce the froth.
U.S. Pat. No. 3,749,378 to Rhodes discloses an apparatus for foaming a coffee extract. Gas is introduced into the coffee extract and the foamed coffee is then spray-dried to make a soluble coffee product having a low bulk density.
A similar process is described in EP 0 839 457 B1 to Kraft Foods, whereby the soluble coffee powder is foamed by gas injection. The gas bubbles size is then reduced such that the final product will have gas bubbles of less than 10 micrometres.
Many instant foamed beverages are still lacking insofar as the foam initially produced is not conserved during consumption or the structure resembles a coarse foam rather than a fine and smooth (velvety) foam, ultimately desired by consumers. Alternatively or additionally, there may simply be insufficient foam produced.
It has now been found that powders, in particular granulated products, which resemble agglomerated, freeze-dried textures with a certain microstructure enable the production of an instant beverage product which provides excellent foam and dissolution upon reconstitution in a liquid.
It has also now been found that agglomeration of the precursor to form the powder of the invention under certain conditions enables the production of an instant beverage product which provides excellent foam upon reconstitution with water.
Agglomeration of food products by sintering is known. For instance, U.S. Pat. No. 6,497,911 to Niro, refers to a process of preparing a water soluble coffee or tea product using a non-rewetted particulate material obtained from an extract by drying. During the process, external compaction of the product is required resulting in a product which suffers from structural collapse of the internal pores.
U.S. Pat. No. 5,089,279 to Conopco relates to a sintering process which is performed in a closed container so as not to lose humidity during sintering. This is suitable for confectionary, for instance, as it results in a sintered mass.
U.S. Pat. No. 4,394,395 to Nestlé describes a process for manufacturing a food product where a powder is filled into moulds, lightly compressed and then heated to sinter the powder. This results in a moulded food product.
However, this does not give a product having the desired porosity characteristics required for foaming upon reconstitution with water.
Thus, agglomeration using a sintering process is known to cause the partial or complete collapse of the microstructure (pores) in the product within which gas would be held. This problem needs to be addressed in order to provide a beverage having a desirable foamed upper surface.
Therefore, the present invention thus seeks to provide a beverage powder, which upon reconstitution yields a beverage with a desirable foamed upper surface.
The object of the invention is solved by the independent claims. The dependent claims further develop the central idea of the invention.
Thus, according to the present invention there is provided an instant beverage powder having a foaming porosity of at least 35%, having an open pore volume of less than 3 mL/g and having an internal pore average diameter D50 of less than 80 micrometres.
According to another aspect of the invention, the use of a powder according to claims 1 to 11, for the preparation of an instant beverage is provided.
In a further aspect, the present invention relates to a method for the manufacture of an instant beverage powder comprising the steps of:
wherein the porous base powder is characterised in that it has a particle porosity of at least 35%, wherein the pores have a D50 diameter of less than 80 micrometres.
A product obtainable by the present method also falls under an aspect of the invention.
Additional features and advantages are described herein, and will be apparent from the following Detailed Description and the figures.
The present invention is further described hereinafter with reference to some of its embodiments shown in the accompanying drawings in which:
The present invention relates to instant beverage powders which deliver an excellent foamed upper surface (also called “crema”) upon reconstitution with a liquid.
In one embodiment of the invention, the instant beverage powder is a granulate. In the following the term “granulate” is used to describe a powder product which may be obtainable by agglomeration of smaller powder particles. The granulate particles thus comprise smaller constitutive powder particles. These smaller constitutive powder particles may be partially fused to form the bigger granulate particles.
In the following, the term “powder” is used interchangeably to define the powders of the present invention and the finer powders which are used in the production of the beverage powders of the invention. Which definition is to be understood is clear from the context.
In the following, the term “open pores” is used to define channels present in the powders of the present invention. The term “closed pores” is used to define completely closed voids. Thus liquids such as water may not penetrate in the closed pores.
Referring to
Upon reconstitution in a liquid, the powders of the invention produce foam. The powders of the invention may thus be further defined by their foaming porosity.
Foaming porosity is a measure of the porosity which contributes to foaming and characterises the potential foaming ability of the powder of the invention. Indeed, open pores (3) will not contribute to the foaming as much, or even in some cases not at all compared to closed pores (2). Pores with opening diameter of less than 2 micrometres (4) may also contribute to foam since the capillary pressure in these pores is greater than the ambient pressure and this may enable foam formation. In the present invention, the foaming porosity is obtained by including closed pores (2) and open pores having an opening diameter of less than 2 micrometres (4).
Thus, for the purpose of measuring the foaming porosity, only closed pores (2) as well as open pores (4) having an opening diameter of less than 2 micrometres are taken into account as these are considered to contribute to foaming. The foaming porosity is obtained by the ratio of the volume of pores contributing to foaming over the volume of the aggregate excluding the volume of open pores having an opening diameter above 2 micrometres. This can be measured by mercury porosimetry or X-ray tomography.
The foaming porosity of the present powder is at least 35%, such as at least 40% or at least 50%. Preferably, the foaming porosity is between 35 and 85%, more preferably between 40 and 80%, even more preferably between 40 and 75%, even more preferably between 45 and 70%, most preferably between 45 and 65%.
Another characteristic of the powders of the invention is their open pores (3). These open pores form the channels for liquid penetration into the powders of the invention. The larger the volume and size of the open pores, the higher the liquid penetration and the better the dissolution. Thus, the powders of the invention may be characterised by their “open pore volume” which provides an estimation of the ability to dissolve the powder of the invention. In order to measure the open pore volume per gram of powder, the volume of the interstices having an opening diameter between 1 and 500 micrometres is taken into account. This can be measured by mercury porosimetry.
The present powders are characterised by an open pore volume of less than 3 mL/g. Preferably, the open pore volume is between 0.4 and 3 mL/g, more preferably between 0.6 and 2.5 mL/g, even more preferably between 0.8 and 2.5 mL/g, most preferably between 0.8 and 2.0 mL/g.
It has also been found by the present invention that another factor influencing the dissolution and the foam volumes obtained upon reconstitution is the size distribution of the closed pores, i.e. of the internal voids (2) and the open pores having an opening of less than 2 micrometres (4). According to the invention, the powders have an average closed pore diameter D50 of less than 80 micrometres. Preferably the pores have an average diameter D50 of less than 60 micrometres, more preferably less than 50 micrometres, even more preferably less than 40 micrometres, most preferably less than 30 micrometres. The pore size distribution is based on the void space distribution.
The pore size distribution may be characterised by a distribution span factor of less than 4, preferably less than 3, most preferably less than 2. The distribution span factor is obtained by X-ray tomography. The span of the distribution is calculated by the following equation:
wherein D90, D10 and D50 represent respectively the equivalent pore size comprising 900, 10% and 50% of the above mentioned pore size distribution. Thus, the lower the span factor, the more narrow and homogeneous the distribution of the pores.
As a consequence, the quality, amount and stability of the crema of the powders of the invention (
Thus, the instant beverage powder of the present invention is characterised in that it has a foaming porosity of at least 35%, has an open pore volume of less than 3 mL/g and has a closed pore average diameter D50 of less than 80 micrometres.
The size of the granulate particles of the present invention is greater than 0.5 mm, preferably greater than 1 mm, more preferably greater than 1.5 mm.
The powder of the invention typically has a tapped density of 150-300 g/L, preferably 200-250 g/L.
Tapped density (g/mL) is determined by pouring a powder into a cylinder, tapping the cylinder in a specific manner to achieve more efficient particle packing, recording the volume, weighing the product, and dividing weight by volume. The apparatus used is a JEL jolting density metre STAV 2003.
The water content of a product of the invention is preferably between 2% and 4.5%, more preferably between 3% and 4%.
The product of the present invention dissolves in water to produce a stable froth without use of additives. This avoids the use of emulsifiers, for instance, traditionally used in the art to stabilise foams.
The powder according to the invention is preferably an instant coffee powder. Alternatively, the instant beverage may be coffee with chicory, cereal, dairy or non-dairy creamer, malted beverages. Alternatively still, the instant beverage may be made from chicory and/or cereals, cocoa, chocolate, malted beverages, dairy or non-dairy creamer.
Thus, the product of the invention can be used, for instance, as a foaming instant coffee product or can be blended with other dry food and beverage ingredients such as flavours, sweeteners, and creamers to formulate a wide variety of foaming instant beverage products.
The product of the invention contains gas (e.g. trapped air) for forming a foamed upper surface when reconstituted with water It has also been found to dissolve at a greater rate than traditionally associated with instant beverage products.
The powders of the invention may thus be used in the preparation of an instant beverage. Preferably, the instant beverage is coffee. Upon reconstitution, the instant beverage preferably has a crema of at least 3 mL when using 5 g of powder in 200 mL of deionised water at 85° C. The amount of crema produced can be measured with a simple device (
In a method of the invention, beverage powder particles may be obtained by heating a base powder above its glass transition temperature. Preferably, this is achieved by sintering as described in the following.
According to the process of the invention and referring to
Preferably the precursor powder is spray-dried. Typically, the precursor comprises instant coffee particles.
In a preferred embodiment, the porous base powder is characterised in that it has a particle porosity of at least 45%, wherein the pores have a D50 diameter of less than 80 micrometres. Such a powder may be obtained according to the method described in U.S. 60/976,229. This provides the advantage that the instant beverage powder produced provides, upon reconstitution, more crema.
The tappet density of the precursor is typically between 150 and 600 g/L.
The second step in the present method is the sintering of the particulate porous base powder to form an agglomerated cake. This is achieved by heating the base powder above its glass transition temperature and controlling the fusion time. It has been found that a particulate precursor can be sintered under specific conditions which enable the pore structure of the sintered particles to remain intact and thereby to retain a desired amount of gas therein.
The glass transition temperature of instant coffee granules can be higher or lower depending on the specific chemical composition and moisture level. The glass transition temperature can intentionally be raised or lowered by simply decreasing or increasing, respectively, the moisture content of the coffee product using any suitable method known to one skilled in the art.
The glass transition temperature can be measured using established Differential Scanning calorimetry or Thermal Mechanical Analysis techniques. The glass transition temperature marks a secondary phase change characterised by transformation of the powder product from a rigid glassy state to a softened rubbery state. In general, gas solubilities and diffusion rates are higher in materials at temperatures above their glass transition temperature.
In order to achieve controlled fusion of the particles, the temperature at which sintering is carried out is preferably at least 35° C. above the glass transition temperature of the agglomerated cake, more preferably at least 40° C. and even more preferably at least 45° C. above.
In the context of the present invention, the terms “wet”, “pre-wet” and the like are used interchangeably with and so have the same meaning as the terms “humidify, pre-humidify” and the like.
In the present method, it is preferable to pre-humidify or humidify the powder in a way that the internal structure remains intact.
In order to achieve controlled fusion of the particles, it is desirable that the precursor particles are firstly dried to the desired (internal) final water content before undergoing the humidification step. It has been found that this improves the foaming and dissolution characteristics of the sintered product. The particles, prior to humidification, are preferably dried to a moisture content of from 1 to 7% by weight, based on the total weight of the particles, more preferably from 2 to 6%, most preferably from 3 to 5%.
The pre-wetting or simultaneous wetting during sintering is achieved by exposing the particles to a gas, typically air, which has a specific humidity level, or by condensation or by contacting with an atomised liquid. The present method differs with regular agglomeration in that the particles in the sintering process stay in contact with each other during the entire humidification or wetting step.
Preferably the air which is used to wet the surface of the particles has a humidity level of from 20 to 80%, preferably 60%.
The sintering process conditions are chosen such that the desired end-product characteristics are obtained.
Sintering can be carried out according to any well known sintering process though belt sintering is preferred.
In a preferred process, the particles are distributed onto a preferably porous surface to form a bed. Preferably the bed has a thickness of from 1 to 50 mm, more preferably 2 to 35 mm, most preferably 5 to 25 mm.
Although not essential, the use of a porous bed is advantageous since it has been found that this enables a thicker bed to be sintered, and so gives a greater throughput of product. Furthermore, by allowing air to penetrate the bed from all sides, this results in an improved homogeneity in the degree of sintering across the bed.
The bed then undergoes the sintering step. Typically, the bed will be transported into a sintering zone for this step.
Preferably, the sintering is carried out under a humid atmosphere, said atmosphere having a moisture content of 20 to 80%, preferably 60%.
The temperature at which sintering is carried out is preferably within the range of from 40°-90° C., preferably about 70° C.
During the sintering, the heat is applied by convection. The gaseous heating media passes over and/or through the product. This way of heating allows a controlled and homogeneous sintering of the product.
The sintering must be carried out during a period of time which enables the correct degree of fusing of the particles without causing undesirable changes to the internal structure of the particles. As can be seen in
If, according to an embodiment of the invention, the precursor is pre-humidified prior to sintering, this will generally have the effect of reducing the sintering residence time.
During the sintering process, a slight and controlled compaction pressure may be applied. However, preferably no external compaction pressure is applied to the bed. This is important to get the desired porosity of the bed. The desired porosity is important for a fast dissolution and crema formation upon reconstitution.
Thus, the present method is unlike traditional sintering which uses a combination of heat and elevated pressures which typically causes a considerable reduction of interparticle porosity and a collapse of the internal particle structure.
During the sintering process, the product takes up moisture from the gaseous heating media. The resulting final moisture of the sintered product is from 4% to 12% by weight of water based on the total weight of the product. Following sintering, the ‘cake” obtained (cf
In a third step of the method, the agglomerated cake is then texturised to obtain the instant beverage powder. Typically, texturising involves cutting or grinding of the cake to form particles having a desired average diameter which resemble typically freeze-dried or agglomerated instant beverage products. In one embodiment of the invention, the product of the invention is not freeze-dried. Preferably, the texturising is carried out by forcing the agglomerated cake through a sieve having a mesh size between 1 and 5 mm, preferably about 2.5 mm
Sifting is then carried out in order to remove the “fines” or the oversized particles from the product.
Optionally and advantageously, a further drying step is carried out in order to provide the sintered product with a moisture content of about 2 to 8% by weight of water based on the total weight of the product. Preferably the final product has a moisture content between 2% and 4.5%, more preferably about 3.5%.
Typically, the manufactured instant beverage powder has a tapped density preferably between 150-300 g/L.
The present method offers advantages in terms of the final product structure in comparison to traditional manufacturing methods. This is illustrated in
For instance, in a traditional steam agglomeration process, the initial powder particles are usually exposed in an agglomeration nozzle to steam and specific pressure conditions for particles collision. The steam condensates partially on the particle surface, causes a state change from glassy into rubbery state and creates a sticky surface that allows the particles to agglomerate. This process typically takes place in a time range of less than 1 second. Therefore, the contact time between particles available for fusion is very short and demands a severe state change to make agglomeration happen. This severe state change concerns not only the particle surface but also affects the internal pore structure of the particles. In consequence, the particles lose their ability to generate foam.
By contrast, in the present invention, the product powder is preferably spread in a thin layer and is exposed to a controlled atmosphere with a specific temperature and humidity. The transfer of humidity and heat from the atmosphere to the product takes place slowly so that the state transformation at the particle surface can be better controlled. The long contact time leaves time for slow particle fusion. It allows to apply just the right degree of state change at the surface required for the desired fusion of particles at their point of contact in the powder layer but without affecting the internal structure, within which the gas is entrapped. In addition, because the powder layer maintains a desired level of interparticle porosity after fusion, this allows for improved water penetration into the final product upon reconstitution, which accelerates particle disintegration and dissolution in the cup. The rapid disintegration and dissolution ensures timely gas release which is essential for foam-formation.
A product obtainable by the process described above typically comprises granulated structures (cf.
The present invention is further illustrated by means of the following non-limiting examples.
In the following examples, all values are percentage by weight unless otherwise indicated.
Preparation of an Agglomerated Soluble Coffee Product by Sintering on a Tray.
A soluble coffee product was manufactured according to the flowsheet in
Preparation of a Granulated Soluble Coffee Product by Belt Sintering
A soluble coffee product was manufactured according to the flowsheet in
Mercury Porosimeter to Evaluate Foaming Porosity, Particule Porosity and Open Pore Volume
AutoPore IV 9520 was used for the structure evaluation (Micromeritics Inc. Norcrose, Ga., USA). The operation pressure for Hg intrusion was from 0.4 psia to 9000 psia (with low pressure from 0.4 psia to 40 psia and high pressure port from 20 to 9000 psia). The pore diameter under this pressure is ranged from 500 to 0.01 μm. The data reported was volume (ml/g) at different pore diameter (μm).
About 0.1 to 0.4 g of samples was precisely weighted and packed in a penetrometer (volume 3.5 ml, neck or capillary stem diameter 0.3 mm and stem volume of 0.5 ml).
After the penetrometer was inserted to the lower pressure port, sample was evacuated at 1.1 psia/min, then switch to a medium rate at 0.5 psia and a fast rate at 900 μm Hg. The evacuating target was 60 μm Hg. After reaching the target, the evacuation was continued for 5 min before Hg is filled in.
The measurement was conducted in set-time equilibration. That is, the pressure points at which data are to be taken and the elapsed time at that pressure in the set-time equilibration (10 sec) mode. Roughly 140 data points were collected at the pressure ranges.
The bulk volume of the granulate was obtained from the initial volume of mercury and the sample holder. The volume of the open pores with opening diameter greater than 2 micrometers (3) was obtained after intrusion with mercury up to a diameter of 2 micrometer. Subtraction of this volume from the bulk volume of the granulate gave the new volume of the granulate which comprises the closed pores (2), open pores with opening diameters less than 2 micrometers (4) and the volume of the coffee matrix. The volume of the closed pores, open pores with opening larger than 2 micrometers in the granulate was obtained by subtracting the volume of the coffee matrix from the new volume of the granulate. The volume of the coffee matrix was obtained from the weight of the sample and coffee matrix density. The foaming porosity is the ratio of the volume of closed pores and open pores having an opening diameter of less than 2 micrometer over the new volume of the granulate.
The particle porosity of the precursor powder may be measures using the method as described in U.S. 60/976,229.
The volume of open pores per gram of product in the diameter range 1 to 500 micrometres gives the “open pore volume”.
Determination of the Internal Structure of Coffee Particles by Microcomputed X-ray Tomography
X-ray tomography scans were performed with a 1172 Skyscan MCT (Antwerpen, Belgium) with a X-ray beam of 80 kV and 100 uA. Scans were performed with the Skyscan software (version 1.5 (build 0) A (Hamamatsu 10 Mp camera), reconstruction with the Skyscan recon software (version 1.4.4) and 3D image analysis with CTAn software (version 1.7.0.3, 64-bit).
To obtain a pixel size of 1 um, the camera was set up at 4000×2096 pixels and samples were placed in the Far position. Exposure time is 2356 ms. Scan was performed over 180°, the rotation step was 0.3° and the frame averaging was 4.
The reconstruction of the dataset was performed over 800 slices in average, with the settings contrast at 0-025. Smoothing and ring artefact reduction were set up at 1 and 10, respectively.
3D image analysis was performed on the 1 um per pixel datasets. The analysis was performed in two steps: (i) a first step to select the particle be analysed by excluding the inter particle voids, (ii) the second step to obtain the distribution of the porosity in the selected region of interest. The foaming porosity value obtained by this technique matched closely that obtained by mercury porosimetry.
Selection of the Particles, i.e. Volume of Interest
The images of 1 um per pixel resolution in grey levels were segmented at a grey level of 30 out of 255, cleaned by removing any single spots smaller than 16 pixels, and then dilated by mathematical morphology (radius of 3 pixels). The selection of the volume of interest was performed through the shrink-wrap function, and then this volume was eroded by mathematical morphology (radius of 3 pixels) to adjust to the surface of the particles.
Void Space Distribution in the Region of Interest:
The images were reloaded and segmented at a grey level of 40 out of 255. The foaming porosity was then calculated as the ratio of the volume of pores to the volume of the particles, the volume of the particles being equal to the volume of interest. The structure separation gave the pores size distribution.
It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.
The present application is a divisional application of U.S. patent application Ser. No. 12/741,739, filed on Sep. 15, 2010, which is the U.S. national stage designation of International Application No. PCT/EP08/064834, filed on Oct. 31, 2008, which claims priority to U.S. Provisional Application 60/986,503, filed on Nov. 8, 2007, the entire contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12741739 | Sep 2010 | US |
| Child | 13873996 | US |
