GB2128068A - Process of and apparatus for conditioning freshly roasted coffee - Google Patents

Abstract

Coffee is conditioned by being fed into a container 1 the atmosphere of which is flushed by inert gas fed through inlet valve 2 to allow the carbon dioxide content of the atmosphere in the chamber to drop to a predetermined level e.g. six percent as measured by a monitor 6. At the same time, gas is evacuated through exhaust 18. When said level has been attained, the flushing and exhausting are discontinued until the proportion of carbon dioxide in the atmosphere has risen to a second predetermined level, e.g. eight percent. These operations are then repeated until the coffee has been maintained in the container for a sufficient length of time for a required proportion of carbon dioxide to occlude from the cells of the coffee, which can be discharged, with inert gas being fed into the chamber at the same volumetric rate as the rate of discharge. <IMAGE>

Description

SPECIFICATION Process of and apparatus for conditioning freshly roasted coffee This invention relates to the conditioning and packaging of freshly roasted coffee and, more especially, is a development of the process and apparatus disclosed in our earlier British Patent Specification No. 1200635.

When preparing roasted coffee for packing it is important to remove excess carbon dioxide generated in the cells of the coffee during roasting, especially if the coffee is to be packaged in a flexible package which is not to become inflated, or indeed so inflated as to burst, during storage. In our prior process, which has proved very successful and which we are still using, the coffee is treated under a reduced pressure in order to accelerate removal of carbon dioxide from the coffee cells but with the carbon dioxide being flushed out from the treatment container with nitrogen periodically during the conditioning period. In this prior process we take care to ensure, in order to preserve the full flavour of the coffee, that the vacuum applied does not drop too low so as to prevent loss of significant amounts of the odorous constituents of the coffee.

The present invention is directed at improving this prior process so that the conditioning can take place at atmospheric pressure without any excessive extension of the conditioning time required. Conditioning at atmospheric pressure has advantages both in the quality of the coffee product and in the practical application process. Thus as regards the coffee product there is even less risk of any desirable odorous constituents since the pressure is not even iowered to the preferred pressure of 500 Torr of the prior princess. A practical advantage which is achieved is that the container is not required to be a pressure vessel and withstand substantial differences in pressure between the interior and exterior thereof.This means that the container can be more lightly constructed and, furthermore, can readily be constructed to larger dimensions than the previous resistant container without there being the same restriction in shape, in that the container no longer needs to be specially designed so as to be resistant to substantial changes in pressure between the interior and exterior thereof.

According to the present invention there is provided a method of conditioning freshly roasted coffee which includes the steps of delivering freshly roasted coffee into a chamber, measuring the proportion of carbon dioxide in the atmosphere in the chamber, evacuating gas from the chamber while at the same time replenishing the evacuated gas with inert gas until the proportion of carbon dioxide in the chamber atmosphere has dropped to a first predetermined level, the pressure in the chamber being maintained substantially at ambient, discontinuing the evacuating and replenishing operation whilst maintaining the coffee in the chamber until the proportion of carbon dioxide has risen to a second predetermined level, recommencing the evacuation and replenishment operation until the proportion of carbon dioxide has again fallen to said first predetermined level, and repeating these operations as necessary to maintain the proportion of carbon dioxide in the chamber atmosphere between said first and second levels for a time sufficient for the evolution of the required proportion of occluded carbon dioxide from the cells of the coffee.

Conveniently the inert gas may be nitrogen which is flowed through the mass of coffee in the enclosed chamber to accelerate the rate of diffusion of the occluded gas from the cells of the roasted coffee by maintaining the atmosphere in the chamber to be predominantly of nitrogen at normal atmospheric pressure. This atmosphere is regulated during conditions of coffee so that the proportion of carbon dioxide gas in the atmosphere inside the chamber is not increased beyond predetermined limits.We have found that the high concentration of carbon dioxide which results with filling a chamber with freshly roasted coffee can be reduced to the first predetermined level, conveniently six percent, and thereafter being maintained between that level and an upper level of, for example, eight percent, by repeating the inflow of nitrogen gas and the simultaneous outflow of gases through an exhaust system when the carbon dioxide proportion has reached the upper limit of eight percent. By having the lower limit of six percent carbon dioxide at which the evacuation and nitrogen replenishment system is stopped, unnecessary use of nitrogen gas is avoided since we have found that there is no significant advantage to be obtained by reducing the proportion of carbon dioxide in the atmosphere any lower.We have found that the conditions which result in the most advantageous rate of diffusion of carbon dioxide from the cells of the freshly roasted coffee without significant loss of any of the more odorous constituents is more efficiently achieved by avoiding a high concentration of carbon dioxide outside the cells of the coffee than by providing a subatmospheric pressure of 500 Torr where the proportion of carbon dioxide may be higher. The maintenance of the predominantiy nitrogen atmosphere surrounding the coffee at normal atmospheric pressure has proved very efficient and effective in conditioning the coffee by removal of the carbon dioxide until such time as can be stored in an oxygen-free atmosphere, for example in a flexible plastics bag which would be extremely badly affected by a subsequent release of high pressure carbon dioxide.

The provision of the inert nitrogen gas atmosphere in the package is also extremely effective in preventing the rapid staling of the coffee which would otherwise take place were the roasted coffee to be exposed to an atmosphere containing a substantial proportion of oxygen.

Preferably, once the coffee has been conditioned, during discharge from the chamber the coffee is replaced with the insert gas at the same rate as the volumetric rate of discharge from the chamber. In order to ensure lack of contact of the conditioned coffee with oxygen it may conveniently be discharged into an enclosed conveyor, the interior of which is supplied with the inert gas, for conveyance to a packing station where the coffee can itself then be packaged in the inert gas atmosphere.

According to another aspect of the present invention there is provided apparatus for conditioning freshly roasted coffee and comprising a gas tight container, means for feeding coffee to be conditioned into said container, means for feeding inert gas at a controlled rate into the container, means for evacuating gas at a controlled rate from a container, means for measuring the proportion of carbon dioxide in the atmosphere in the container, and control means responsive to the measuring means for controlling operation of the gas feed means and the gas evacuation means whereby such gas feed and evacuation means are non-operative whenever the proportion of carbon dioxide drops to a first predetermined level and are reoperative when the proportion of carbon dioxide rises to a second predetermined level.

Conveniently the feed means may comprise a porous plastics tube extending across the interior of the container with the tube being received in a space defined by a grid or grill beneath the tube and a deflector above the tube.

The invention will be further described, by way of example, with reference to the accompanying drawing, in which: Figure 1 is a diagrammatic illustration of apparatus for carrying out the process of the invention; and Figure 2 is a detailed diagrammatic cross-sectional view of part of the gas infeed and evacuation means as received in the container of the apparatus shown in Figure 1.

In Figure 1 there is illustrated a container 1 defining a conditioning chamber into which coffee may be fed through an inlet provided with a substantially gastight slide valve 2. At the lower end of the container there is provided an outlet slide valve 3 above a rotary valve 16 which can be driven to rotate at a speed such as to permit discharge of the contents of the container at a controlled volumetric rate.

Extending across the interior of the container 1 there is a gas infeed structure 4 and a gas exhaust structure 5. As can be appreciated from Figure 2 each of these structures 4 and 5 comrise an elongated tube 21 of porous plastics material which is protected from above by an inverted V-section deflector shield 20. The shield 20 and the tube 21 are carried by a support grill or grid 22 secured to the interior walls of the container. The conduit 17 leads from a supply of nitrogen to the gas inlet 4. This conduit 17 leads via a pressure reducing valve 15, used to reduce the pressure of nitrogen gas in the supply conduit 17 to a conveniently low pressure of, for example, 1.5 or 1.7 bar absolute. Downstream of the valve 15 there is connected a conduit 19 for a purpose to be described.Downstream of the junction with the conduit 19 there is provided a solenoid control valve 11, a fine adjustment valve 10 to control the rate of low of nitrogen gas flowing into the container when the valve 11 is open, and a flow rate indicator 9 to show the volume rate of flow of inert gas, nitrogen, flowing into the container 1.

An exhaust conduit 18 leads from the exhaust structure 5 in the chamber to atmosphere. Located in the conduit 18 are a solenoid valve 7 for opening and closing the exhaust conduit and a flow rate indicator 8 to show the volume rate of flow of gas through the exhaust conduit 18. Connected to the exhaust conduit 18 so as to be in direct communication through the exhaust conduit with the interior of the container is a test capillary connection 6a and also a connection from the conduit 19, the conduit 19 containing a solenoid control valve 12, a fine control valve 13 and a rate of flow indicator 14. The capillary 6a connects via a carbon dioxide gas monitor 6 with an outlet capillary tube 6b leading to atmosphere.The gas monitor 6 incorporates a small pump constantly drawing about 1.5 litres per minute of gas from the exhaust conduit through the capillary tube 6a, the drawn-off gas passing through a thermal conductively gas detector and thence to the atmosphere via capillary tube 6b. The valves 7, 11 and 12 are connected to a control system 30 which operates each valve in accordance with the control signals received from the monitor 6 dependent upon the proportion of carbon dioxide in the container. As illustrated the control means 30 are shown connected to the solenoid valve 6, 7, 11 and 12 to the monitor 6 and to the rotary valve 16.The fine adjustment valves of 10 and 13 may also be connected to a more sophisticated form of the control system although in most cases these can be manually controllable to be set up using a flow meter 9 to compare with the flowmeter 8 and using a flowmeter 14 to set up the rate of flow known to be achieved by the rotary positive displacement valve 16. Conveniently the conditioning of the coffee can be monitored by the control system 30 being provided with a timer and chart whereby a record is kept of the elapsed time after commencement of a conditioning cycle during which the valves 7 and 11 are open to permit flushing out of the carbon dioxide and the elapsed time when these valves are closed following reduction of the carbon dioxide content to a first predetermined level of, conveniently, six percent.

During operation of the apparatus the slide valve 2 is opened and freshly roasted coffee discharged into the container 1. The valve 2 is then closed and with the high proportion of carbon dioxide in the atmosphere in the container being sensed by the monitor 6 the control system 30 operates to open valves 11 and 7. The carbon dioxide gas monitor 6 incorporates a small pump constantly drawing about 1.5 litres per minute of gas from the exhaust conduit 18 through the capillary tube 6a to pass it through a thermal conductivity gas detector and thence to atmosphere via the capillary tube 6b.

With valves 11 and 7 open nitrogen gas is fed through the conduit 17 into the container and flushes down through the container forcing the gas in the container out from the bottom through the exhaust conduit 18 to atmosphere. The rate of flow of the gas through the exhaust conduit 18 can readily be seen as being at the same rate as the flow of gas through the inlet conduit 17 by comparison of the neighbouring flow rate indicators 8 and 9, the direct comparison in fact not being essential at this time since the rate of flow of the exhaust is dependent upon the rate of flow of inlet gas.

Once the sensor 6 has noted that the proportion of carbon dioxide has dropped to a first predetermined level which may, for example, conveniently be six percent, the control system firstly closes the valves 7 and 11 so that the coffee in the container 1 lies dormant, exuding carbon dioxide until such time as the proportion of carbon dioxide in the atmosphere in the container as measured by the monitor 6 has reached a second, higher, predetermined level of, conveniently, eight percent. The valves 7 and 11 are then opened for recommencement of the flushing operation and this intermittent opening and closing of the valves 7 and 11 dependent upon the concentration of carbon dioxide in the container 1 continues until such time as conditioning of the coffee is complete.It will be appreciated that as an increasing amount of carbon dioxide is extracted from the container since the pressure of carbon dioxide in the cells of the coffee is progressively reduced, the time interval between the closing and subsequent opening of the valves 7 and 11 increases.

When conditioning of the coffee is compiete and it is required for packing the valve 3 is opened and the rotary positive displacement valve 16 is rotated with the solenoid valve 12 being opened. Under these conditions the fine adjustment valve 13 is so set up that nitrogen is supplied through a conduit 19 into the conduit 18 and then back into the container to replace the coffee removed through the rotary valve 16 at the same volumetric rate of flow as such coffee removal. With this arrangement the container 1 when empty of coffee is left with an atmosphere of inert gas and if, for any reason, packaging has to cease part way through discharge of the container 1 the coffee can reliably be left in the inert atmosphere in the container 1 until packaging can be commenced without there being any risk of deterioration since it is maintained out of contact with oxygen.

Conveniently, in order to maintain the condition of the coffee, it may be fed from the discharge valve 16 into a closed conveyor which itself is provided with an atmosphere of nitrogen or other inert gas for conveyance of the coffee to a packaging station where it will be packaged in an atmosphere of inert gas, for example, in flexible packages. The backflow of nitrogen during discharge of the coffee has a further benefit in that it helps to keep the filter provided by the porous tube 21 in the outlet 5 backflushed clear of any fine coffee dust which might otherwise clog it if allowed to build up over a number of operating cycles of the apparatus.

Claims (17)

1. A method of conditioning freshly roasted coffee which includes the steps of delivering freshly roasted coffee into a chamber, measuring the proportion of carbon dioxide in the atmosphere in the chamber, evacuating gas from the chamber while at the same time replenishing the evacuated gas with inert gas until the proportion of carbon dioxide in the chamber atmosphere has dropped to a first predetermined level, the pressure in the chamber being maintained substantially at ambient, discontinuing the evacuating and replenishing operation whilst maintaining the coffee in the chamber until the proportion of carbon dioxide has risen to a second predetermined level, recommencing the evacuation and replenishment operation until the proportion of carbon dioxide has again fallen to said first predetermined level, and repeating these operations as necessary to maintain the proportion of carbon dioxide in the chamber atmosphere between said first and second levels for a time sufficient for the evolution of the required proportion of occluded carbon dioxide from the cells of the coffee.

2. A method according to claim 1, wherein the inert gas is nitrogen.

3. A method according to claim 1 or 2, wherein the first predetermined level is six percent carbon dioxide.

4. A method according to claim 1, 2 or 3, wherein the second predetermined level is eight percent carbon dioxide.

5. A method according to any preceding claim wherein the conditioned coffee is discharged with the chamber being replenished with inert gas at the same rate as the volumetric rate of discharge from the chamber.

6. A method according to claim 5, wherein the coffee is discharged into an enclosed conveyor the interior of which is supplied with inert gas for conveyance to a packing station.

7. A method according to any preceding claim wherein the coffee is packaged in an atmosphere of inert gas.

8. Apparatus for conditioning freshly roasted coffee and comprising a gas tight container, means for feeding coffee to be conditioned into said container, means for feeding inert gas at a controlled rate into the container, means for evacuating gas at a controlled rate from a container, means for measuring the proportion of carbon dioxide in the atmosphere in the container, and control means responsive to the measuring means for controlling operation of the gas feed means and the gas evacuation means whereby such gas feed and evacuation means are non-operative whenever the proportion of carbon dioxide drops to a first predetermined level and are reoperative when the proportion of carbon dioxide rises to a second predetermined level.

9. Apparatus according to claim 8 wherein the first predetermined level is six percent and the second predetermined level is eight percent.

10. Apparatus according to claim 8 or 9, wherein the gas feed and/or evacuating means comprises a porous plastics tube extending across the interior of the container.

11. Apparatus according to claim 10, wherein the plastics tube is received in a space defined by a grill or grid beneath the tube and a deflector above the tube.

12. Apparatus according to any one of claims 8 to 11, wherein means are provided for feeding conditioned coffee from the container together with means for feeding replacement inert gas into the container at the same rate as the outlet feed of the conditioned coffee.

13. Apparatus according to claim 12, wherein the means for feeding replacement inert gas is arranged to feed the gas into the container through the outlet which in normal operation is connected to the gas evacuation means.

14. Apparatus according to any one of claims 8 to 13, wherein means are provided for ensuring that the feeding of the inert gas during use of the apparatus is at substantially the same rate as the rate of evacuation of gas from the container.

15. Apparatus according to any one of claims 8 to 14, wherein a timer is provided for noting the relative proportions of the elapsed time during which gas feeding and evacuation is taking place during operation of the apparatus.

16. Apparatus for conditioning coffee constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

17. Amethod of conditioning coffee substantially as hereinbefore described with reference to the accompanying drawings.