Title of Invention

COFFEE AROMA RECOVERY PROCESS AND AROMA PRODUCT

Abstract

A process for the recovery of aroma components from coffee. A slurry of coffee grounds in an aqueous liquid is subjected to stripping for stripping aroma components from the slurry. The stripping is carried out using gas in a substantially counter-current manner to provide an aromatised gas containing aroma components. The aroma components are then collected from the aromatised gas. The aroma components may be added to concentrated coffee extract prior to drying of the extract. The coffee powder produced has much increased and improved aroma and flavour and contains higher levels of furans and diketones.

Full Text

COFFEE AROMA RECOVERY PROCESS AND AROMA PRODUCT This invention relates to a process for the recovery of coffee aroma prior of extraction and to the aroma so recovered. The recovered aroma is useful for aromatizing instant coffee. Aromas are an important part of many products since consumers associate certain aromas with certain products. If the product lacks the aroma associated with it, consumer perception of the product is adversely affected. This is particularly a problem in the field of instant coffees, although it also exists in other fields, Instant coffee powders which are obtained from commercial processes involving extraction, concentration and drying are usually substantially aroma-less. For this reason, it is conventional to recover coffee aromas which are given off during the processing of the instant coffee and to reincorporate these aromas into the concentrated coffee extract prior to drying or into the instant coffee powder. The coffee aromas are recovered at several points during processing of the instant coffee and most commonly during grinding of the roasted beans and by steam stripping of the coffee extract prior to concentration and drying of the coffee solids. The recovery of aroma from ground coffee is disclosed in US patent 3535118. This patent discloses a process in which roast and ground coffee is placed in column and maintained at about 40°C. The bed of coffee is then moistened by spraying water on it to assist in displacing aromas from the coffee particles. An inert gas, usually nitrogen, is heated to about 44°C and introduced into the column from beneath the bed. As the inert gas passes up through the bed, it strips the aromas from the coffee particles. The inert gas is then fed to a condenser which is operated at a temperature of about 5°C to condense water in the inert gas. The de-watered inert gas is ultimately fed to a cryogenic condenser to condense the aroma as a frost. The frost is then recovered. Another process for recovering aroma from roast and ground coffee is described in international patent application WO 97/10721. In this process, the ground coffee is transported through an elongated mixing zone while being agitated. At the same time, an aqueous fluid is sprayed into the elongated mixing zone to moisten the ground coffee as the ground coffee is being transported and agitated. Aroma gases released by the moistened ground coffee in the elongated mixing zone are drawn off and are collected. Similar processes are described in UK patent 1466884 and US patent 4092436. One of the problems perceived to arise with these processes is that they result in pre-wetting of the coffee grounds outside of the extraction cell or column. According to Civets, M and Defroster N. W.; 1979; Coffee Technology, AVI Publishing Company, Inc., page 334, this practice is bad because it "causes undesirable flavor and a loss in natural coffee grounds should occur in the extraction cell or column. Consequently recovery of aroma from ground coffee by pre-wetting it is not common practice; despite ground coffee being a good source of aroma. Further, not all components of the aroma obtained in a cup of freshly brewed coffee are captured during pre-wetting. Consequently, unless further aroma is captured later during the process, some aroma components are lost; components which would, if incorporated into instant coffee powder, improve the aroma of a beverage prepared from the instant coffee powder. Further, many of the conventional recovery techniques damages or alter the aroma components. The process parameters described in patent application No. GB 946346 is related to the vegetable extracts processing. The invention mentioned in GB946346 was not confined towards the coffee aroma processing in which a slurry was prepared. And extraction was done by using an inert gas and evaporation and condensed. Condensate then centrifuged to remove the solid part of the extract. Drying of liquid extract was done by spray or vacuum drying. The invention mentioned in patent No. EP0574034 is the aroma enrichment of coffee by diacetyl and acetaldehyde obtained from thermal hydrolysis of partially extracted roasted and ground coffee beans and by absorbing the aroma by microporous adsorbent, which is either a resin or activated carbon. Therefore, there is still a need for a process for coffee aroma recovery and aroma product from ground coffee. Accordingly, in one aspect, this invention provides a process for the recovery of aroma components from coffee, the process comprising: providing a slurry of coffee grounds in an aqueous liquid: stripping aroma components from the slurry using gas in a substantially counter-current manner for providing an aromatized gas containing aroma components: and collecting the aroma components from the aromatized gas. The process provides the advantages that significantly larger amounts of aroma components may be stripped from the coffee than is the case with conventional processes. Further, since the aroma components are stripped from the coffee prior extraction, thermal degradation of the aroma is reduced to a minimum. Also, these aroma components may be readily reincorporated to provide a soluble coffee product which has increased and improved aroma and flavors. The slurry of coffee grounds may be provided by slurring roasted and ground coffee with the aqueous liquid, or by slurring whole coffee beans with the aqueous liquid and then subjecting the coffee beans to grinding. The coffee grounds preferably have an average particle size in the range of about 1 mm to about 3 mm. The process preferably further comprises the step of adding the collected aroma components to a concentrated coffee extract and drying the coffee extract to powder for providing an aromatized soluble coffee powder. The process may further comprise the step of concentrating the collected aroma components. The aroma components may be collected by subjecting the aromatised gas to one or more condensation operation. Preferably, in a first operation, the 0°C to about 98°C and, in a second operation, the aromatized gas is subjected to cryogenic condensation at a temperature of less than about -80°C. The first operation may be carried out in one or more steps. For example, the aromatized gas may subjected to condensation at temperature in the range of about 80°C to about 95°C and, in a second step, at a temperature in the range of about 0°C to about 10°C. Altemative ly, the aromatised gas may be subjected to condensation at a temperature in the range of about 20°C to about 50°C. Preferably the aroma components are stripped from the slurry in a disc and donut stripping column. The gas used to strip aroma components is preferably low-pressure gas: for example steam at a gauge pressure of less than about 100 kPa. In another aspect, this invention provides an aromatised, spray-dried soluble coffee powder, which comprises least about 0.35 equivalent |ag/g furans and at least about 0.25 equivalent |ig/g diketones. In yet another aspect, this invention provides an aromatised, freeze-dried soluble coffee powder, which comprised least about 0.60 equivalent jig/g furans about 0.40 equivalent |ig/g diketones. The invention also provides aromatised soluble coffee powders produced by the processes defined above. Embodiments of the invention are now described, by way of example only, with reference to the drawing, which is a schematic flow diagram of an aroma recovery process. Referring to Figure 1, roasted coffee 10 is introduced into a mixing tank 12. The mixing to tank 12 is sealed to prevent aroma loss. Altemative ly, any aroma components escaping from the mixing tank 12 should be collected: for example by directing the aroma components to a condenser. The coffee 10 may be in the form of whole bean or may be ground. If ground coffee is used, the particle size of the coffee is preferably in the range of about 1 to about 3 mm. Roasted coffee surrogates, such as chicory may also be added to the mixing tank 12. An aqueous liquids 14 is also introduced into the mixing tank 12 in order to slurry the from a downstream extraction operation. The use of coffee extract is preferred. The temperature of the aqueous liquid 14 is preferably in the range of about 20°C to about 99°C: for example about 80°C to about 99°C. The amount of aqueous liquid used to slurry the coffee 10 is not critical but is suitably sufficient such that the solids content of the resulting slurry 16 is about 10% to about 305 by weight. A solid content of about 50% to about 155 by weight is preferred. The slurry 16 is transported to the top of a stripping column 18. If the coffee in the slurry 16 was not ground prior to forming of the slurry 16, the slurry column 18. The whole beans in the slurry 16 are then ground in the wet grinder to a suitable particle size; for example in the range of about 1 to about 3mm. Any suitable we grinder 20 may be used. Suitably slurry pumps (not shown) are used to transport the slurry 16 to the stripping column 18. The temperature of the slurry 16 prior to being introduced into the stripping column 18 is preferably above about 90°C. this may be achieved by using an aqueous liquid 14 at a temperature above about 90°C or by subjecting the slurry 16 heating; preferably indirect heating. The slurry 16 is introduced into the stripping column 18 through a suitable distributor 22 and flows downwardly through the stripping column 18. A stripping gas 24, conveniently steam but which may also be nitrogen, carbon dioxide or mixtures of steam, nitrogen, and carbon dioxide, is introduced into the stripping column 18 adjacent the bottom of the stripping column 18. The stripping gas 24 flows upwardly through the stripping column 18, substantially counter-current to the slurry. As the stripping gas 24 flows through the stripping column 18, it strips and transports aroma components from the coffee in the slurry. A gas stream 26 made up of the steam, gas liberated from the coffee, and a transported aroma component is removed form the top of the stripping column 18. A stripped slurry 28 is removed from the bottom of the stripping column 18. The amount of stripping gas 24 used to strip the aroma components from the slurry 16 may be selected as desired within the constraints of the type of stripping column 18 selected. Strip rates of about 5% to about 100% by weight of steam to dry coffee introduced may be suitable. For lower stripping rates, for example about 10% to about 20%, the total amount of aroma components removed from the slurry is less. However less moisture, which may dilute the coffee extract produced downstream when the aroma is recombined with 100 kPa (gauge); for example below about (20kPa gauge). The water used to generate the steam is preferably subjected to de-oxygenation prior to being formed into steam. If desired, inert carrier gases such as nitrogen may be introduced into the stripping column along with stripping gas 24. Any suitable stripping column 18 may be used; packed or plate. Suitable stripping columns are well known in the art and the skilled person may readily select a suitable column depending upon the process conditions and fluid characteristics. However, it is found that disc and donut columns operate reasonably well, particularly since they are less susceptible to plugging. The gas stream 26 leaving the top of the stripping column 18 is then processed to capture the aroma components. This may be carried out using conventional techniques. For example, the gas stream 26 may be led to a sufficiently low to condense most of the aroma from the gas stream 26. A temperature of below about 50°C is suitable although cooling to below 30°C is preferred. Preferably more than one condenser is used; each succeeding condenser being operated at al lower temperature than the previous condenser. Preferably the downstream most condenser is operated at a temperature of about 0°C to about 10°C. If it is desired to concentrate the aroma components using partial condensation, the gas stream may be subjected to a first condensation step at a high temperature; for example at about 80°C to about 95°C. This will result in the condensation of primarily water. The non-condensing and concentrated aroma components may then be subjected to a second condensation step at a lower temperature; for example at about 0°C to about 50'^C to provide the aroma liquid 30. The aroma liquid 30 removed from the condenser system 28 contains aroma components, which may be used to aromatize coffee as explained below. Aroma components 32 which do not condense in the condenser system 28 may be directed to a cryogenic aroma condenser (not shore) for collection. Many suitable cryogenic aroma condensers are known and have reported in the literature. However, a particularly suitable cryogenic aroma condenser is described in US patents 5182926 and 5323623; the disclosures of which are incorporated by reference. Further details of the operation pf this cryogenic aroma condenser may be obtained from the disclosures in the patents. Plainly other cryogenic aroma condensers may be used; for example that disclosed in US patent 5030473.. The aroma collected in the cryogenic aroma condenser is in the form of a frost. The frost may be used to aromatize coffee extract as explained below. Alternatively, the frost may be combined coffee oil. This aromatised carrier is conveniently added to the soluble coffee powder finally produced. The stripped slurry 28 leaving the bottom of the stripping column 18 is transported to an extraction system (not shown). The extraction system may be any suitable system include batteries of fixed bed cells, plug flow reactors, moving bed reactors and the like. During the extraction process, the coffee grounds may be subjected to one or more thermal solubilisation steps. The coffee extracts leaving the extraction system is then concentrated as is conventional. However, some of the coffee extract may be used as the aqueous liquid 14 instead of being concentrated. The aroma liquid 30 removed from the condenser system 28 may then be added to the concentrated extract. If desired, the aroma components in the aroma liquid 30 may be concentrated prior to being added to the concentrated extract. This may be necessary to avoid dilution of the concentrated extract if higher stripping rated were used in the stripping column. Concentration may be carried out using conventional procedures such as partial condensation, rectification, membrane concentration and freeze concentration. Also, the foots obtained from the cryogenic aroma collector may be added to the concentrated extract. The aromatised extract is then dried in the usual manner to provide an aromatised, soluble coffee powder; for example by spray or freeze-drying. Of course, the aroma liquid 30 and aroma frost may be used for other aromatization purpose. It is found that that the process results in an aromatised coffee powder which has much more aroma and flavour than produced by conventional techniques. When dissolved in hot water, the powder provides a product which has increased flavour and aroma strength; especially in coffins, body and rustiness. In particular, the coffee powder products contain higher amounts of furans and diketones than conventional coffee powder products. Furans and kiketones contributes to the aroma and flavour of beverages produced from the coffee powder products to improve the beverages. When produced by spray drying, the coffee powder products contain at least about 0.30 equivalent ^ig/g furans and at least about 0.25 equivalent diketones. Preferably, the coffee powder product further contains at least about 0.02 equivalent |ig/g of each of 5-methlfurfural and 2,3-hexanedione. More preferably, the coffee powder products at least about 0.04 equivalent jig/g of 2,3-hexanedione. When produced by freeze-drying, the coffee powder products contain at least 0.60 equivalent |ig/g furans and least 0.04 equivalent |ig/g diketone. Preferably, the coffee powder product further contains at least 0.02 equivalent jig/g of each of 5-methylfurfural and 2,3-hexanedione. More preferably, the coffee powder products contains at least about 0.65 equivalent |ig/g furans, at least about 0.04 equivalent |ig/g of each of 5-methylfurfural, 2-methyl-pyrazine and 2,3-hexanedione. In this specification, the term "Furans" means compounds of the furan class including furan, 2-methylfuran, 3-methylfuran, 2,5-dimethylfuran, 2-vinylfuran, dihydro-2-methyl-3(2H) furan one, 2-furancaboxaldehyde,2-vinyl- 5methylfuran,[(methylthio) methyl] furan,2-2'- methylenebisfuran, and, l-(2-furanylmethyl)-lH- pyrrole. The term "Diketones" means compounds of the diketone class including 2,3-butanedine, 2,3-pentanedione and 2,3-hexanedione. The term "equivalent ng/g" means equivalent |ig of methyl butyrate per g of roast and ground coffee. Specific examples of the invention are now described to further illustrate the invention. In the examples, aroma components are analysed using gas chromatography and mass spectrometry. The aroma components are introduced into the gas chromatography using a purge and trap method. The conditions of the gas chromatograph and mass spectrometer are as follows; Column Restock RTX-1 60m x 0.25mm x 1.0 um Flow rate 20 ml/minute in He carrier gas Split ratio 20:1 Initial temperature 35°C Initial hold time 1 minute Temperature increase rate 4°C per minute Final temperature 230°C Solvent delay 0 minutes Scan range 35 to 260 ami Electron energy 70 volts. All results are expressed in equivalent of methyl butyrate per g of roast and ground coffee. The detection limits of the analytical procedure for certain of the Of course it is possible that lower amounts of these compounds may be detected using other techniques. Example 1 Roast and ground coffee is fed into a slurry tank at a rate of about 2.7 kg/minute. The roast and ground coffee has an average particle size of about 1.4 mm. A coffee extract containing about 8 to 10% by weight of soluble coffee solids is also fed into the slurry tank at rate of about 27 kg/minute. The resulting slurry is fed to the top of a disc and donut stripping column using a slurry pump. The column has 12 stages. The intemal diameter of the column is 23 cm and the height of each stage is 20 cm. Steam at a low pressure of less than about 20 kPa (gauge) is fed into the bottom of the stripping column. The flow rate of the steam is varied to provide a range of stripping rates between 15% and 90% by weight of steam compared to roast and grooms coffee. The aromatised gas stream leaving the stripping column is condensed in a condenser operating at about 20^*0. The condensed liquid is collected and analyzed for aroma components. The uncondensed gas is transported to a cryogenic aroma collector operated as described in US patent 5,182,926. The aroma frost collected in the cryogenic aroma collector. The stripped slurry leaving the stripping column is then subjected to extraction in a continuous extraction system made up of three extraction reactors and two solubilisation reactors. The yield is about 50 to 53% by weight. The extract obtained is concentrated to provide a concentrated extract containing above about 40% by weight of soluble coffee solids. The condensed liquid from the condenser is added to the concentrated extract and the extract is dried to soluble powder in a spray-drying tower. The process is repeated except that the frost from the cryogenic aroma collector is also added to the concentrated extract. A teaspoon of each soluble powder is dissolved in 150 ml of hot water at 85*^0. All beverages produced have a brew-like flavour and aroma with good coffeeness, acidity, body and roastiness. The beverages produced from soluble powder produced at higher stripping rates have more flavour and aroma. The beverage produced from the soluble powder having the frost added to it has perceivably more above-the-cup aroma and roastiness. Example 2 The process of example 1 is repeated except that whole roasted beans are fed into the slurry tank. The resulting slurry is then fed to a wet, in-line grinder in which the beans are ground to an average particle size of about 2.4 mm. The slurry is then transported to the stripping column. The stripping rate in the column is 90% be weight of steam compared to roast and ground coffee. The aromatised gas stream leaving the stripping column is then subjected to concentration by rectification in a packed rectification column. The rectification section of the column is 1.5 long and the stripping section is 1.2 m long. The boil up rate is fixed at 720 ml/minutes. The condensing in the rectification condenser is collected and comprises about 10% by weight of the roast and ground coffee. A teaspoon of each soluble powder is dissolved in 150ml of hot water at SS^'C. All beverages produced have a brew-like flavour and aroma. Further, the beverages are perceived to have more roastiness, body and balance than the beverages produced in example 1. Example 3 Roast and ground coffee is extracted, without stripping of the aroma prior to extraction, in a continuous extraction system made up of three extraction reactors and two solubilisation reactors. The extraction conditions are substantially identical to those of example 1. The extract obtained is then subjected to steam stripping in a stripping column is conventional manner. The aromatised gas stream leaving the stripping column is condensed in a condenser operating under conditions substantially identical to those of the condenser of example 1 The extract leaving the stripping column is concentrated to provide a concentrated extract containing above about 40% by weight of soluble coffee solids. The condensed liquid from the condenser is added to the concentrated extract and the extract is dried to soluble powder in a spray-drying tower. A teaspoon of each soluble powder is dissolved in 150ml of hot water at 85°C and the beverage analysed for aroma components. The results are as follows: Sample Aroma Count (cumulative equivalent jig/g roast coffee) Example 1, 15% strip, without frost 3.6 Example 1, 15% strip, with frost 6 Example 1, 30% strip, without frost 6 Example 1, 30% strip, with frost 8.5 All soluble coffee beverages produced from the process of example 1 have higher aroma counts; even a low stripping rates. Further, the beverage produced from the powder of example 3 is perceived to have less flavour and aroma. Example 4 The process of example 1 is repeated at a stripping rate of 40% by weight of steam compared to roast and ground coffee. The aromatised gas stream leaving the stripping column is then subjected to concentration by partial condensation. Two condensers are used; a first condenser operating at about 5° to about 15°c, The liquid condensing in the first condenser contains primarily water and is disposed of The liquid condensing in the second condenser is collected and comprises about 15% by weight of the roast and ground coffee. The concentrated extract is freeze-dried instead of spray-dried to powder. The aroma strength of a beverage produced from the powder of this example is compared to that of a beverage produced from the powder of example 3: The beverage produced from the powder of this example has higher aroma counts. Further, the beverage produced from the powder of example 3 is perceived to have less flavour and aroma. Example 5 The process of example 1 is repeated at a stripping rate of 40% or 90% by weight of steam compared to roast and ground coffee. The aromatised gas stream leaving the stripping column is then subjected to concentration by rectification in a packed rectification column. The rectification section of the column is L5m long and the stripping section is 1.2 m long. The boil up rate is fixed at 720 ml/minute. The liquid condensing in the rectification condenser is collected and comprises about 10% by weight of the roast and ground coffee. The concentrated extract is either freeze-dried or spray-dried to powder. The aroma strength of a beverage produced from the powder of this example is compared to that of a beverage produced from the powder of example 3: The beverage produced from the powder of this example has much higher aroma counts. Further, the beverage produced from the powder of example 3 is perceived to have less flavour and aroma. Example 6 Four commercially available coffee products are used:- a NESCAFE product purchased in the UK, a MAXWELL HOUSE product, a FOLGERS products and a KROGERS products; a soluble powder produced according to example 1 at 15% strip without frost addition, and each of the spray dried soluble powders of example 5. All products have been spray-dried. A teaspoon of each soluble powder is dissolved in The beverages of examples 1 and 5 contain levels of total aroma and furans at least as high as beverages produced from the commercially available products. Further, the beverages of example 1 and 5 contain at least 100% more diketone than the commercially available beverage with the next highest levels. Diketones are responsible for providing coffee beverage with buttery notes and are desirable. The beverage of example 1 and 5 also contain detectable levels of 2, 3-hexanedione while the other beverage do not. Example 7 The process of example 1 is repeated at a stripping rate 90% by weight of steam compared to roast and ground coffee. The aromatised gas stream leaving the stripping column is then subjected to concentration by freeze concentration. The concentrated liquid leaving the freeze concentration system is collected and comprises about 10% by weight of the roast and ground coffee. The aroma strength of a beverage produced from the powder of this example is compared to that of a beverage produced from the powder of example 3: The beverage produced from the powder of this example has much higher aroma counts. Further, the beverage produced from the powder of example 3 is perceived to have less flavour and aroma. Example 8 Five commercially available coffee products are used:- a NESCAFE GOLD product purchased in the UK, a MAXUM product, an ALTA RICA product, and a CARTE NOIRE product; a soluble powder produced according to example 5 at 90% strip vetch frost addition, a soluble powder produced according to example 5 at 90% strip without frost addition, a soluble powder produced according to example 5 at 40% strip without frost addition, and a soluble powder produced according to example 4 at 40% strip without frost addition. All products are freeze-dried. A teaspoon of each soluble powder is dissolved in 150ml of hot water of 85°C and the beverage analysed for aroma components. Further, roasted coffee beans are brewed in a commercial brew device to provide a beverage of substantially the same strength as the beverages produced from the soluble powders. The results are as follows: The beverage produced by the powder of example 5 at 90% strip and with frost addition has an aroma compound profile, which is substantially identical to that of brew coffee. Further, the beverage has a brew-like flavour and aroma. All of the beverages produced from the powders of example 4 and 5 have much higher levels of furans, 5-methyl furfural, diketones, 2,3-hexanedione and 2-methyl-pyrazine. The furans are responsible for providing beverages with toasted notes and are highly desirable. The beverages produced from the powders of example 4 and 5 perceived to have more brew-like flavour and aroma, roastiness, body and balance than the beverages produced from commercially available powders. We Claim 1. A process for the recovery of aroma components from coffee, the process comprising: providing a slurry of coffee grounds in an aqueous liquid; stripping aroma components from the slurry prior to extraction by introducing gas into the slurry and using the gas in a substantially counter-current manner for providing an aromatised gas containing aroma components, and collecting the aroma components from the aromatised gas. 2. A process according to claim 1 in which the slurry of coffee grounds is provided by slurrying whole coffee beans with the aqueous liquid and then subjecting the coffee beans to wet grinding. 3. A process according to claim 1 in which the coffee grounds have an average particle size in the range of 1 mm to 3 mm. 4. A process according to claim 1 in which the aroma components are collected by subjecting the aromatised gas to, in a first operation, condensation at a temperature in the range of 0°C to 50°C and, in a second operation, to cryogenic condensation at a temperature of less than about - 80° 5. A process according to claim 1 in which the aroma components are stripped from the slurry in a disc and donut stripping column. 6. A process according to claim 5 in which the gas used to strip the aroma components is at a gauge pressure of less than 100 kPa. 7. A process for the recovery of aroma components arum coffee substantially as herein described with reference to the accompanying drawings.

Documents:

in-pct-2000-496-che claims duplicate.pdf

in-pct-2000-496-che description (complete) duplicate.pdf

in-pct-2000-496-che-abstract.pdf

in-pct-2000-496-che-assignement.pdf

in-pct-2000-496-che-claims.pdf

in-pct-2000-496-che-correspondnece-others.pdf

in-pct-2000-496-che-correspondnece-po.pdf

in-pct-2000-496-che-description(complete).pdf

in-pct-2000-496-che-drawings.pdf

in-pct-2000-496-che-form 1.pdf

in-pct-2000-496-che-form 13.pdf

in-pct-2000-496-che-form 26.pdf

in-pct-2000-496-che-form 3.pdf

in-pct-2000-496-che-form 5.pdf

in-pct-2000-496-che-pct.pdf