Foaming coffee composition

Abstract

The present invention provides a foaming instant coffee composition comprising particles having a bulk density of from 0.16 to 0.45 g/cm.sup.3, said particles comprising a continuous phase comprising an instant coffee matrix and a non-continuous phase comprising particles of a foamable component containing a gas.

Claims

1. A process for preparing a foaming instant coffee composition comprising the steps of: i. mixing particles of a foamable component with an aqueous coffee extract to form a coffee mixture; ii. before the particles of the foamable component have dissolved, freezing the coffee mixture; iii. granulating the frozen coffee mixture; and iv. forming the foaming instant coffee composition by removing water by sublimation, wherein the foaming instant coffee composition includes a continuous phase comprising an instant coffee matrix and a non-continuous phase comprising particles of the foamable component containing a gas, the non-continuous phase being entrapped within the instant coffee matrix.

2. The process according to claim 1 wherein the particles of the foamable component are cooled to 5 C. or less prior to mixing with the aqueous coffee extract.

3. The process according to claim 2 wherein the particles of the foamable component are cooled in liquid nitrogen.

4. The process according to claim 1 wherein the aqueous coffee extract has a coffee solids content of at least 40 wt %.

5. The process according to claim 1 wherein the aqueous coffee extract is cooled to 0 C. or less prior to mixing with the particles of the foamable component.

6. The process according to claim 1 wherein the particles of the foamable component are mixed with the aqueous coffee extract for 2 minutes or less prior to freezing.

7. The process according to claim 1 wherein the foaming instant coffee is freeze-dried.

8. The process according to claim 1 further comprising the step of injecting a gas into the aqueous coffee extract prior to mixing with the particles of the foamable component.

9. The process of claim 1 further comprising the step of slab freezing the coffee mixture prior to granulating.

10. A process for forming a foaming freeze-dried instant coffee composition comprising the steps of: cooling an aqueous coffee extract to a temperature of less than about 5 C.; cooling particles of a foamable component to a temperature of less than about 5 C.; mixing the particles of the foamable component with the aqueous coffee extract to form a coffee mixture; before the particles of the foamable component have dissolved, freezing the coffee mixture; removing water by sublimation from the coffee mixture to form the foaming freeze-dried instant coffee composition, wherein the foaming freeze-dried instant coffee composition includes a continuous phase comprising an instant coffee matrix and a non-continuous phase comprising particles of the foamable component containing a gas, the non-continuous phase being entrapped within the instant coffee matrix.

11. The process according to claim 10 wherein the aqueous coffee extract has a coffee solids content of at least 40 wt. %.

12. The process according to claim 10 wherein the particles of the foamable component are mixed with the aqueous coffee extract for 2 minutes or less prior to freezing.

13. The process according to claim 10 further comprising the step of injecting a gas into the aqueous coffee extract prior to mixing with the particles of the foamable component.

Description

EXAMPLES

Example 1

(1) This example demonstrates the benefits of the present invention in instant freeze-dried soluble coffee reconstituted with 200 cm.sup.3 of hot (85 C.) water in a 250 cm.sup.3 beaker having a 65 mm internal diameter.

(2) Instant freeze-dried soluble coffee was prepared according to the following procedures. First an aqueous coffee extract was produced by dissolving 240 g of instant freeze-dried coffee granules, of moisture content about 2% by weight, in an equal quantity of hot water. This aqueous coffee extract was then cooled to a temperature of about 5 C. The cooled aqueous coffee extract was then foamed to a density of about 0.8 g/cm.sup.3 by the introduction of nitrogen gas whilst being subjected to mixing at a high shear level in order to uniformly disperse the entrained gas bubbles within the cooled aqueous coffee extract. The foamed aqueous coffee extract was then further cooled to a temperature of about 10 C., and further mixed to ensure homogeneity.

(3) A foamable component was prepared according to the following procedures. First, a quantity of a porous spray-dried soluble coffee powder (having a mean particle size (D50) of about 200 m as measured by laser diffraction with 0%>500 m) containing a plurality of closed pores was loaded into a pressure vessel. This soluble coffee powder had a glass transition temperature (Tg) of about 60 C. and closed pore volume of about 0.75 cm.sup.3/g. The pressure vessel was pressurised with nitrogen to a pressure of about 40 bars gauge.

(4) The vessel was then heated by means of an external heating jacket to a temperature in excess of 90 C., above the glass transition temperature of the soluble coffee. The vessel and contents were held at this temperature for a period of about 10 minutes. The vessel was then cooled to a temperature of about 30 C., below the glass transition temperature of the soluble coffee, thus trapping a portion of nitrogen at superatmospheric pressure inside the closed pores of the spray-dried soluble coffee powder. The vessel was depressurised and the soluble coffee powder was unloaded. When 3 g of this soluble coffee powder containing entrapped nitrogen at superatmospheric pressure was reconstituted as described above, the height of the foam (measured between the surface of the liquid and the top of the foam) was in excess of 10 mm. In contrast, the height of the foam created without addition of the pressurized powder was about 1.5 mm. Knowledge of the foam density and incremental foam volume was used to estimate the amount (corrected to room temperature and pressure) of gas released by the foaming agent to at least about 15 cm.sup.3 per gram of powder at ambient temperature (25 C.)

(5) The foamable component was cooled to a temperature of about 65 C. and 160 g of the foamable component was mixed by hand (using a spoon) into the cooled foamed aqueous coffee extract. This mixing process took about 2 minutes. The resulting mixture was then further cooled to a temperature below about 30 C. in order to form a solid slab, by passing the solid slab through a CES linear freezing tunnel. The freezing tunnel uses the vaporisation of liquid nitrogen both to produce a flow of cooled air which is blasted at the slab by means of a series of fans, and to directly cool the product by vaporisation of liquid nitrogen on the product surface inside the freezing tunnel. The freezing tunnel was set to operate at an internal air temperature of 70 C., and the slab residence time in the tunnel was set to approximately 4 minutes. The slab was passed through the tunnel three times to ensure complete freezing. After freezing, the solid slab was stored overnight in a freezer at a temperature of about 65 C., before being granulated using a granulator located inside a cold-room at about 40 C. Water was then removed from the resulting granules by the sublimation of ice to water vapour through the standard process of freeze-drying under partial vacuum.

(6) The resulting freeze-dried coffee product was then sieved in order to separate any particles less than 500 m from the freeze-dried coffee granules, which closely resembled standard commercial freeze-dried coffee granules. The granules had a bulk density of 0.228 g/cm.sup.3, a tapped bulk density of 0.237 g/cm.sup.3, a skeletal density of 1.06 g/cm.sup.3 and a closed pore volume of 0.29 cm.sup.3/g. When 3 g of these coffee granules was re-constituted as described above, the amount of foam on the beverage surface was observed to be significantly greater than commercially available freeze-dried coffee granules, and the foam layer was observed to fully cover the beverage surface even after the beverage had been stirred. The foam volume upon re-constitution as measured by the quantitative in-cup foam test was 3 cm.sup.3 after 1 minute, and 1 cm.sup.3 after 10 minutes.

(7) It was noted that the freeze-dried particles of size less than 500 m generated a very large amount of foam when re-constituted as described above. It is contemplated that these fine particles, which were of similar appearance to a spray-dried coffee powder, consisted partly of particles of the foamable component that had not been sufficiently dispersed into the aqueous coffee extract so as to remain entrapped in the granules after granulation of the frozen slab. It is thought that these particles retained the majority of their entrapped gas at superatmospheric pressure, even after the freeze-drying process.

(8) Table 4 (below) summarises the results of additional experiments carried out to illustrate some of the features of the invention. All closed pore volumes in this Example were calculated relative to the true density of this soluble coffee which was measured to be 1.53 g/cm.sup.3.

(9) TABLE-US-00004 TABLE 4 Tapped Closed Bulk bulk Skeletal pore Foam volume density density density volume (cm.sup.3) Experimental details (g/cm.sup.3) (g/cm.sup.3) (g/cm.sup.3) (cm.sup.3/g) 1 minute 10 minutes Composition produced by 0.228 0.237 1.06 0.29 3 1 the method of Example 1 Composition produced by 0.269 0.284 1.4 0.07 0.5 0 the method of Example 1 but without the addition of foamable component Composition produced by 0.221 0.232 1.21 0.17 2 0.5 the method of Example 1 but with the addition of 120 g of foamable component to coffee extract cooled to +5 C. Composition produced by 0.223 0.235 1.16 0.21 3 0.5 the method of Example 1 but with the addition of 120 g of foamable component to coffee extract cooled to 5 C. Composition produced by 0.231 0.248 1.19 0.19 1.5 0 the method of Example 1 but with the addition of 60 g of foamable component Composition produced by 0.269 0.293 0.65 0.87 2 0 the method of Example 1 but with the addition of 120 g of non-pressure- treated foamable component* Composition produced by 0.275 0.284 1.23 0.15 5 1 the method of example 1 but using pressure- treated freeze-dried coffee granules as the foamable component *The granules were generally spheroid in appearance and did not resemble standard freeze-dried coffee granules

Example 2

(10) The following example demonstrates the benefits of the present invention in instant freeze-dried soluble coffee composition reconstituted with 200 cm.sup.3 of hot (85 C.) water in a 250 cm.sup.3 beaker having a 65 mm internal diameter.

(11) An instant freeze-dried soluble coffee composition was prepared following the method of Example 1, using a spray-dried maltodextrin-based foamable component in place of the spray-dried soluble coffee foamable component of example 1.

(12) This maltodextrin-based foamable component was prepared according to the following procedures. A quantity of porous spray-dried powder consisting of 92% maltodextrin and 8% modified food starch, (having a mean particle size (D50) of about 130 m as measured by laser diffraction with 0% of particles >500 m) containing a plurality of closed pores was loaded into a pressure vessel. This maltodextrin-based powder had a glass transition temperature (Tg) of about 100 C. and closed pore volume of about 0.9 cm.sup.3/g. The pressure vessel was pressurised with nitrogen to a pressure of about 40 bars gauge. The vessel was then heated by means of an external heating jacket to a temperature in excess of 145 C., above the glass transition temperature of the maltodextrin-based powder. The vessel and contents were held at this temperature for a period of about 10 minutes. The vessel was then cooled to a temperature of about 50 C., below the glass transition temperature of the maltodextrin-based powder, thus trapping a portion of nitrogen at superatmospheric pressure inside the closed pores of the maltodextrin-based powder. The vessel was de-pressurised and the maltodextrin-based powder was un-loaded. When 3 g of this maltodextrin-based powder containing entrapped nitrogen at superatmospheric pressure was added to 11.5 g of an instant cappuccino mix comprised of soluble coffee, conventional foaming creamer powder, and sugar, and reconstituted as described above, the height of the foam (measured between the surface of the liquid and the top of the foam) was in excess of 30 mm. In contrast, the height of the foam created without addition of the pressurized powder was about 10 mm. Knowledge of the foam density and incremental foam volume was used to estimate the amount (corrected to room temperature and pressure) of gas released by the foaming agent to at least about 15 cm.sup.3 per gram of powder at ambient temperature (25 C.).

(13) The maltodextrin-based foamable component was cooled and mixed into a coffee extract and frozen, granulated, freeze dried and sieved, by the method of example 1, to produce a granular foaming instant freeze-dried coffee composition. The granules were substantially brown in colour, with clearly visible particles of spray-dried powder of a lighter colour embedded within the granule matrix. Also visible were particles consisting of agglomerates of light-coloured spray-dried particles bound by the darker-coloured coffee matrix.

(14) The granules had a bulk density of 0,206 g/cm.sup.3, a tapped bulk density of 0.216 g/cm.sup.3, a skeletal density of 1.19 g/cm.sup.3 and a closed pore volume of 0.18 cm.sup.3/g.

(15) When 3 g of these granules was re-constituted as described above, the amount of foam on the beverage surface was observed to fully cover the beverage surface even after the beverage had been stirred, and indeed persisted to substantially cover the beverage surface 5 minutes after re-constitution. The foam volume upon re-constitution as measured by the quantitative in-cup foam test was 4 cm.sup.3 after 1 minute, and 1.75 cm.sup.3 after 10 minutes.

(16) A composition was also produced by the method of example 2 but with the foamable component at ambient temperature (approximately 20 C.) prior to addition to the coffee extract. The resulting foaming freeze-dried coffee composition had a bulk density of 0.233 g/cm.sup.3, a tapped bulk density of 0.245 g/cm.sup.3, a skeletal density of 1.17 g/cm.sup.3 and a closed pore volume of 0.19 cm.sup.3/g. When re-constituted as described above, a layer of foam was formed which fully covered the beverage surface even after the beverage had been stirred. The foam volume upon reconstitution as measured by the quantitative in-cup foam test was 4 cm.sup.3 after 1 minute and 1.5 cm.sup.3 after 10 minutes.

(17) All closed pore volumes in this example were calculated relative to the true density of this coffee composition which was measured to be 1.51 g/cm.sup.3.

Example 3

(18) The following Example illustrates the production of a granular foaming instant coffee composition by steam agglomeration of an instant soluble coffee powder and particles of a foamable component.

(19) A quantity of instant spray-dried soluble coffee powder was milled, thereby destroying all closed pores, and was then blended with the foamable component of Example 2, such that the foamable component constituted 25 wt % of the blended powder composition.

(20) This blended composition was formed into granules using a steam agglomeration device known as and hereinafter referred to as an instantiser, supplied by ICF INDUSTRIE CIBEC S.p.a., Maranello, Italy. The blended composition was made to fall through a grid of aperture size 2.5 cm and was impinged by a steam flow. A portion of this steam condensed on the particle surfaces, causing the particles to adhere to one another, thus forming agglomerated particles comprising an instant coffee matrix containing entrapped particles of the foamable component. These agglomerated particles were then passed to a rotating drum drying chamber where hot air at a temperature of about 110 C. was used to remove moisture from the agglomerated particles such that the moisture content of the final composition was lower than about 5 wt %.

(21) The final composition was then sieved to remove any fine or un-agglomerated particles with a particle size less than 500 m.

(22) The dimensions of the grid, the product and steam flow rate and the drying temperature can be readily adjusted by one skilled in the art in order to form granules of a desired shape and general appearance. It was found that by using the parameters shown below in Table 5 the agglomerated particles could beneficially be made to resemble the shape and general appearance of and have similar bulk density to a standard freeze-dried instant coffee, said agglomerated particles comprising an instant coffee matrix with particles of foamable component entrapped therein. In addition, it was found that the structure of the foamable component entrapped within said agglomerated particles was substantially retained, such that the agglomerated particles had a closed pore volume of 0.10 cm.sup.3/g, with the closed pores containing an entrapped gas.

(23) When 3 g of the final composition was reconstituted with 200 cm.sup.3 of hot (85 C.) water at in a 250 cm.sup.3 beaker having a 65 mm internal diameter, a layer of foam was observed to fully cover the beverage surface even after the beverage had been stirred, and indeed persisted to substantially cover the beverage surface 5 minutes after re-constitution

(24) TABLE-US-00005 TABLE 5 wt % Tapped foamable Steam Bulk bulk Skeletal True component flow rate density density density density Experimental details (%) (kg/hr) (g/cm.sup.3) (g/cm.sup.3) (g/cm.sup.3) (g/cm.sup.3) Composition produced by the 0 40 0.275 0.292 1.48 1.48 method of Example 3 but without the addition of foamable component Composition 1 produced by 25 40 0.269 0.298 1.31 1.51 the method of Example 3 Composition 2 produced by 25 40 0.252 0.271 1.31 1.51 the method of Example 3 Closed pore Foam volume volume (cm.sup.3) Experimental details (cm.sup.3/g) 1 minute 10 minutes Composition produced by the 0.00 0 0 method of example 3 but without the addition of foamable component Composition produced by the 0.10 4 1.75 method of example 3 Composition produced by the 0.10 4 1.5 method of example 3

Example 4

(25) Freeze-dried coffee granules were reconstituted with an equal amount of hot water to produce a coffee extract with a solids concentration of approximately 50%. This coffee extract was chilled to approximately 5 C. and foamed through the addition of nitrogen gas to give an extract with a foamed extract density of 810 g/l. The coffee extract was then further cooled to approximately 5 C.

(26) Into 40 g of the coffee extract were mixed 10 g of alpha-cyclodextrin-CO.sub.2 clathrate crystals. The resulting mixture was frozen to a temperature below 40 C. and freeze-dried. The freeze-dried product was manually granulated after drying and sieved to remove fines having a size of less than 500 m.

(27) A control sample was also produced by the same method but without the addition of the clathrate crystals.

(28) The sample containing the clathrates swelled slightly during drying compared with the control sample and had a bulk density of 0.18 g/cm.sup.3. The sample had a skeletal density of 1.29 g/cm.sup.3 and a true density of 1.49 g/cm.sup.3, giving a closed pore volume of 0.10 cm.sup.3/g. The sample had the general appearance of standard freeze-dried coffee granules but with some white crystals entrapped therein. It was found that the sample containing clathrate crystals provided significantly more foaming once re-constituted with hot water and stirred, both immediately after stirring and after 5 minutes. The foam volume upon reconstruction as measured by the quantitative in-cup foam test was 2.75 cm.sup.3 after 1 minutes and 1.5 cm.sup.3 after 10 minutes. The control sample (with no foamable component added prior to drying) had no foam.

Example 5

(29) This example relates to instant freeze-dried soluble coffee reconstituted with 200 cm.sup.3 of hot (85 C.) water in a 250 cm.sup.3 beaker having a 65 mm internal diameter.

(30) Instant freeze-dried soluble coffee was prepared according to the following procedures. First an aqueous coffee extract was produced by dissolving instant freeze-dried coffee granules, of moisture content about 2% by weight, in an equal quantity of hot water. This aqueous coffee extract was then cooled to a temperature of about 5 C. The cooled aqueous coffee extract was then foamed to a density of about 0.8 g/cm.sup.3 by the introduction of nitrogen gas whilst being subjected to mixing at a high shear level in order to uniformly disperse the entrained gas bubbles within the cooled aqueous coffee extract. The foamed aqueous coffee extract was then further cooled to a temperature of about 10 C., and further mixed to ensure homogeneity.

(31) A foamable component was prepared according to the following procedures. First, a quantity of freeze-dried soluble coffee granules comprising particles of between about 500 microns and about 3 mm in size were loaded into a pressure vessel. This soluble coffee had a glass transition temperature (Tg. measured by Differential Scan Calorimetry, DSC) of about 60 C., bulk density of about 0.24 g/cm.sup.3 and closed pore volume of about 0.02 cm.sup.3/g. The pressure vessel was pressurised with nitrogen to a pressure of about 40 bars gauge.

(32) The vessel was then heated by means of an external heating jacket to a temperature in excess of 90 C., above the glass transition temperature of the soluble coffee. The vessel and contents were held at this temperature for a period of about 10 minutes. The vessel was then cooled to a temperature of about 30 C., below the glass transition temperature of the soluble coffee. The vessel was depressurised and the soluble coffee was unloaded.

(33) The resulting soluble coffee granules had a bulk density of 0.62 g/cm.sup.3, a skeletal density of 1.17 g/cm.sup.3 and a closed pore volume of 0.20 cm.sup.3/g.

(34) The closed pore volume of the freeze-dried soluble coffee granules increased substantially as a result of the above-mentioned pressure treatment, which may result from closure of some open pores and/or from creation of some new closed pores between fused particles during heating.

(35) When 3 g of these soluble coffee granules containing entrapped nitrogen at superatmospheric pressure were reconstituted as described above, the height of the foam (measured between the surface of the liquid and the top of the foam) was in excess of 21 mm. In contrast, the height of the foam created when the granules prior to pressure treatment were reconstituted as described above was too small to be practicably measurable, i.e. <1 mm. Knowledge of the foam density and incremental foam volume was used to estimate the amount (corrected to room temperature and pressure) of gas released by the foamable component to at least about 15 cm.sup.3 per gram of powder at ambient temperature (25 C.).

(36) A quantity of the foamable component was mixed by hand (using a spoon) into the cooled foamed aqueous coffee extract. This mixing process took about 2 minutes. The foamable component was not cooled prior to mixing, and hence the temperature of the foamable component prior to mixing was about 20 C. The resulting mixture was then cooled to a temperature below about 30 C. in order to form a solid slab, by passing the solid slab through a CES linear freezing tunnel. The freezing tunnel uses the vaporisation of liquid nitrogen both to produce a flow of cooled air which is blasted at the slab by means of a series of fans, and to directly cool the product by vaporisation of liquid nitrogen on the product surface inside the freezing tunnel. The freezing tunnel was set to operate at an internal air temperature of 70 C., and the slab residence time in the tunnel was set to approximately 4 minutes. The slab was passed through the tunnel three times to ensure complete freezing. After freezing, the solid slab was stored overnight in a freezer at a temperature of about 65 C., before being granulated using a granulator located inside a cold-room at about 40 C. Water was then removed from the resulting granules by the sublimation of ice to water vapour through the standard process of freeze-drying under partial vacuum.

(37) The resulting freeze-dried coffee product was then sieved in order to separate any particles less than 500 m from the freeze-dried coffee granules, which closely resembled standard commercial freeze-dried coffee granules, although particles of the foamable component embedded into the coffee granules were visible upon close visual inspection. The granules had a bulk density, tapped bulk density, skeletal density and closed pore volume as indicated blow in TABLE 6. When 3 g of these coffee granules was re-constituted as described above, the amount of foam on the beverage surface was observed to be significantly greater than commercially available freeze-dried coffee granules, and the foam layer was observed to fully cover the beverage surface even after the beverage had been stirred. The foam volume upon re-constitution as measured by the quantitative in-cup foam test is shown below in TABLE 6.

(38) It was noted that the freeze-dried coffee particles produced by the method of EXAMPLE 5 produced a noticeable cracking sound upon re-constitution with hot water, indicating the presence of pressurised gas within the closed pores of the foamable component embedded within the freeze-dried granule matrix.

(39) The slightly greater foam volume produced when using a freeze-dried foamable component compared to using a spray-dried foamable component may be due to the reduced propensity of the freeze-dried foamable component to dissolve in the aqueous chilled coffee extract compared to the spray-dried foamable component.

(40) All closed pore volumes in this Example were calculated relative to the true density of this soluble coffee which was measured to be 1.53 g/cm.sup.3.

(41) TABLE-US-00006 TABLE 6 Quantity Product Product of Quantity Product tapped Product closed foamable of coffee bulk bulk skeletal pore Experimental component extract density density density volume details (g) (g) (g/cm.sup.3) (g/cm.sup.3) (g/cm.sup.3) (cm.sup.3/g) Composition 80 600 0.184 0.209 1.18 0.19 produced by the method of EXAMPLE 5 Composition 160 480 0.275 0.284 1.23 0.16 produced by the method of EXAMPLE 5 Quantity of Quantity of foamable coffee Foam volume Experimental component extract (cm.sup.3) details (g) (g) 1 minute 10 minutes Composition 80 600 3.0 1.0 produced by the method of EXAMPLE 5 Composition 160 480 5.0 1.0 produced by the method of EXAMPLE 5