IE83731B1 - A batch process for coffee production - Google Patents

Abstract

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Description

A batch process for coffee production Introduction The production of coffee is becoming more difficult due to the increasing sophistication of the consumer's taste and a need to thus control, more tightly, the production process and to ensure that there are less variations between the end products or batches produced. A further problem is that additionally the consumer is becoming more concerned about the appearance of, for example, unground coffee beans, rather than just s'mply the organoleptic properties of the coffee. Further, as the price of the raw material increases, it becomes more important for the manufacturer or blender of the coffee to ensure that the correct blends are achieved at minimal cost. It is becoming vtal to control production costs and to ensure adequate quality control so that the product is not rejected due to failing the stringent tests of both taste and appearance. Every batch of coffee that has to be discarded represents a direct loss, not alone of raw materials, but of the processing costs to the blender or manufacturer.

Our UK Patent No. 2282046B discloses a coffee production process and the present invention is directed towards improvements in this process.

One of the major problems is to ensure that there is adequate and uniform roasting of the coffee beans. This has been done generally by providing some device to ensure that the coffee beans are sufficiently agitated in the roasting drum to ensure that they are subjected to adequate heat. The problem is that with many conventional roasting drums, even with the coffee beans agitated considerably by agitating blades, adequate roasting has not been achieved.

The problem with excessive agitation of the coffee beans is that, while adequate heat distribution is achieved, the skin of the beans often splits and is removed, leaving a residue which in turn gets overheated This chaff then tends to remain in the heating drum where it is furtherbheated and roasted leading to an unpleasant taste when it is eventually discharged with another batch of the roasted coffee beans.

The provision of adequate and uniform roasting is very complex. It is not just simply a matter of agitating the beans as much as possible while applying heat It is necessary to ensure that while the beans are adequately agitated and uniform heat is supplied, the beans do not split There must not be excessive heating of the exterior of the beans which will cause the beans to split with consequent removal of the skins and the formation of chaff.

European Patent Specification No. O359515A (NGK Insulators Ltd.) describes in some detail, the various problems in relation to coffee bean roasting and further discloses a device to provide a uniform roasting of coffee beans. Again, itconsists of the two elements of trying to provide uniform heating of the beans while agitating the beans.

It is also known to spray the roasted coffee beans with water immediately after the roasting has been completed within the roasting drum. As a resut of the spray of water onto the coffee beans in the roasting drum, the temperature of the coffee beans falls sharply. This is generally done to ensure that the coffee beans are roasted to the correct temperature and not over-roasted. Essentially, this spraying with water is a pre-cooling, either carried out'immediately after the roasted beans leave the roasting drum or in the roasting drum prior to discharge therefrom. A typical system is that disclosed in German Patent Specification DE 4028111A1 (Tchibo Frisch-Rdst-Kaffee GmbH) where, after roasting but without moistening and cooling taking place in the roasting drum, the roasted coffee is treated in a separate moistening and cooling system.

Statements of Invention According to the invention, there is provided a batch process for the production of coffee comprising the steps of:- sampling supply batches of green coffee beans and delivering acceptable batches of green coffee beans to associated storage silos; selectively discharging pre-determined quantities of between two and five different types of green coffee beans from the storage silos into a cumulative weigher, weighing each quantity of green coffee beans delivered to the weigher in turn to produce a predesired batch of mixed green coffee beans; delivering the coffee beans into a roasting chamber, agitating the beans by continuously raising the beans from the bottom of the chamber to the top, delivering hot combustion gases into the chamber through separate inlets, one delivering the gases tangentially to the movement of the coffee beans in the chamber and the other at substantially right angles thereto , the combustion gases being maintained between 300°C and 650°C; after the coffee beans have been roasting for some time, delivering a continuous spray of water onto the roasting beans and continuing the roasting; stopping the roasting after a preset time; discharging the coffee beans; cooling the coffee beans by air; then testing the batch of roasted coffee beans for colourand taste and, if acceptable, delivering the coffee beans for one of a whole coffee bean blending operation and a coffee blending and grinding operation; packing the coffee by weighing, evacuating air and introducing nitrogen.

A major advantage of the present invention is that by directing the hot combustion gases into the chamber, through separate inlets which direct the gases both tangentially and orthogonally to the wall of the chamber, adequate mixing of the combustion gases is quickly achieved as the beans are being tossed and agitated within the roasting chamber. This substantially reduces the roasting time. Further, adding of water before roasting has completed ensures that the coffee beans are not split because the water, when added, will coat the exterior surface or skin of the coffee bean to ensure that they do not split as the skins will absorb some of this water. This further improves the organoleptic properties of the coffee beans. Effectively, what is done is to add back moisture to the coffee beans which is very advantageous.

Prior to discharging the roasted beans, further precooling by additional water spraying can be carried out.

In one embodiment of the invention, the continuous spraying of water is carried out for between 7.5 and 20% of the total roasting time and generally this is approximately %.

In one process according to the invention, the combustion gases are heated to one temperature, then the temperature is reduced, and finally, the temperature is increased again, in each case the temperature being with'n the range specified.

In a further embodiment, the final temperature is greater than the initial temperature.

Typically, roasting is carried out for between 300 and 475 seconds. However, more often, it is carried out for between 350 and 475 seconds.

Ideally, the pre-cooling of the coffee beans is carried out for between 200 and 350 seconds.

Preferably, the combustion gases are heated to between 325 and 675°C.

In one embodiment of the invention, the agitation of the coffee bean is carried out by rotating a paddle wheel vigorously in the combustion chamber so that the coffee beans are carried up the combustion chamber and then thrown down across the path of the incoming gases.

Detailed Description of the lnvattion The invention will be more clearly understood from the following description of an embodiment thereof, given by way of example only, with reference to the accompanying drawings, in which:- Fig. 1 is a diagrammatic view of the plant according to the invention, Figs. 2 to 7 are successive enlarged views of Fig. 1 from a left to right, and Fig. 8 is a perspective view of a roaster according to the invention.

Referring to the drawings, there is illustrated batch process machinery for the production of coffee, indicated generally by the reference numeral 1, comprising an infeed station 2, a roasting station 3, an intermediate storage station 4, a grinding and packing station 5, a coffee storage station 6 and a ground coffee packing station 7.

Referring now to Fig. 2, the infeed station 2 comprises an inlet hopper 10 for bags of coffee beans which is connected to an airlock 11 and is fed to a weigher 12 by means of a pneumatic conveyor 80. The weigher 12 delivers he beans to an intermediate storage bin 13 which feeds, by a bucket conveyor 81, twenty two storage silos 16, each of which is in turn connected to a cumulative weighs 17 feeding one of two roasters (illustrated in Fig. 3) by a pneumatic conveyor 82. A dust extraction unit 15 is connected to the intermediate storage bin 13. A roasted coffee bean storage silo 18 is also illustrated which is fed by conveyors 84 from the roasters. A return pneumatic conveyor 82(a) connects the silo 18 to the intermediate storage station 4 (Fig. 4).

Referring to Fig. 3, which shows the roasting station, the cumulative weigher 17 if Fig. 2 is illustrated feeding one of two roasters, indicated generally by the reference numerals 19 and 20 by means of the pneumatic conveyor 82. The roaster 19 is similar to the roaster described in UK Patent Specification No. 2282046 and requires no further description. The other roaster 20 comprises an infeed hopper 21 feeding a charging duct 22 which in turn feeds to an air extract duct 23 which is also fed by a catalyser 24. The roaster includes a roasting drum 25 in which is mounted an axially directed burner 26 and a tangentially directed burner 27. Mounted within the drum 25 is a mechanism of revolving paddles 37 mounted on radial arms 38 which are driven by a motor (not shown). A discharge door 28 connects the drum 25 to a cowlhg 33 above a cooling chamber 29. Means to deliver cooling air through the cooler 29 and also means to deliver water into the roasting drum 25 by a spray bar 30, mounted in it.

The cooling chamber 29 connects directly to a destoner bucker 32 via a vibrating tray 31 and hopper 32 which is connected via a pneumatic conveyor 85 to a collection hopper 35 which feeds directly a check weigher 36. The roasters 19 and 20 are either connected via the pneumatic conveyor 82a to the storage silo 18, illustrated in Fig. 2, or are delivered via a pneumatic conveyor 87 to the intermediate storage station, illustrated in Fig. 4.

Referring to Fig. 4, there is illustrated the intermediate storage station 4 for roasted coffee beans from the roasters 19 and 20 and even the silo 18. This comprises storage bins 40, for coffee beans delivered from the roaster 19 and20 for subsequent grinding and storage bins 41 for delivery of coffee beans again from the roasters 19 and 20 which are not for grinding The storage bins 40 feed a pneumatic conveyor and the storage bins 41 feed a pneumatic conveyor 89.

Referring now to Fig. 5, the storage bins 41 are connectedby the pneumatic conveyor 89 through a proportioning weigher 51 and a bucket elevator 52 to awhole bean packaging machine 53 feeding an outlet conveyor 54. The bins 40 are connected by the pneumatic conveyor 89 to grinders 55, each of which in turn feeds through screw augers 56, silos 61 and 62 (see Fig. 6). All of the screw augers 56 are not shown.

Referring to Fig. 6, the silos 61 and 62 each have degassing ducts 63 and in turn feed six packaging machines 71, shown in Fig. 7.

In operation, the production process comprises accepting batches of green coffee beans which are sampled and tested at the infeed station 2 and, if acceptable, are delivered to one of the storage silos 16 through the various weigher 12 and intermediate bin 13 after cleaning bythe dust extraction unit 15 The green beans are taken out of the storage silos 16 hrough the weigher 17 and by the pneumatic conveyor 82 to one of the two roasters 19 or 20. With the roaster 19, the green coffee beans are delivered through the infeed hopper 21 through the charging duct 22 in a batch, usually of 120 kilos, into he drum 25. The burner 26 delivers hot combustion gases and air axially into the drum 25, while the burner 27 delivers the hot combustion gases and air tangentially around the drum 25.

As the green beans are delivered through the charging duct 22, the paddles 37 are rotated causing the green beans to be delivered around the drum 25 and tossed up into the axial and tangentially charging hot combustion gases thus roasting the beans. When most of the roasting has taken place. namely, when most of tie moisture has been extracted from the coffee beans and the outer skin of the coffee beans is starting to change colour, usually somewhere between 20% and 7.5% from the end of the cycle and generally at about 10%, water is sprayed on the still roasting coffee beans. The beans thus absorb a certain amount of moisture and he skins of the beans will not crack. This effectively seals the outer layer of the beans. Further water may optionally be sprayed on the beans, while still in the roaster when the roasting has stopped. This provides further pre-cooling of the beans prior to discharge. Then, the roasted beans are delivered out the discharge door 28 into the cooling chamber 29 where ambient air is driven up through the cooling chamber 29 to further cool the beans which are delivered out the vibrating tray 31 through the de- stoner 32, collection hopper 35 and check weigher 36 to one or other of the sets of bins 40 or 41 for storage.

Generally, the batch of beans that is roasted will be predesired and determined quantities of between two and five different types of green bean from the storage silos 16. The cooled roasted coffee beans are retained in the storage bins 40 or 41, either for subsequent grinding and packaging or for packaging as whole beans. At various stages during the operation, particularly prior to accepting the green beans and also after roasting, the beans are tested for taste and colour since colour is very important in the final package of either ground or whole roasted coffee beans.

Generally, the batch of green beans is released into the roaster 20 in batches of 120 I Kg. They are generally roasted over three heating stages at preset temperatures fora desired period of time. It is these differences in parameters that determine the final colour and flavour of the roasted coffee.

The following table shows the loading of the various burners and the temperatures achieved for a typical batch. The percentage loading refers to the amount of additional air that is added to the burners to control the temperature.

Table 1 — Typical Burner Temperatures Axial Tangential Tangential Axial Heating Gas Heating Gas Full Load 068% 050% 467°C 342°C * Reduction 055% 035% 525°C 499°C 2"“ Reduction 040% 025% 505°C 469°C Nonnally, the roasting takes place at any time between 300 and 475 seconds. It has been found that with the increased temperature and changes in operation, this is sufficient. A typical roasting cycle is given in Table 2 below.

Table 2 — Typical Roasting Cycle Time Seconds Start Most of moisture drawn off 350 Water in Roasting ceases It will also be noted from the above that the combustion gases are heated. generally to between 300°C and 650°C but that the combustion gases are heated to one temperature within the range specified and then, in a three stage process, the temperature is then reduced and then the temperature is raised again. It has been found that this provides the best quality coffee.

It has also been found that delivering the combustion gases both axially and tangentially together with vigorous agitation of the green coffee beans within the roaster is vital to obtain the desired quality.

A particular advantage of the present invention is that oneis able to obtain the same quality of final roasted beans in a cycle of between 5.5 and 6 minutes, while with more conventional roasters, the cycle time is closer to 10 minutes. Further, the invention allows a broad range of roasts to be provided. Additionally, it should be noted that the axial heating produces the major amount of heat.

In the specification the terms “comprise, comprises, comprised and comprising” or any variation thereof and the terms ‘'include, includes, included and including" or any variation thereof are considered to be totally interchangeable and they should all be afforded the widest possible interpretation.

The invention is not limited to the embodiments hereinbefore described but may be varied in both construction and detail.

Claims (1)

1. A batch process for the production of coffee comprising the steps ofe sampling supply batches of green coffee beans and delivering acceptable batches of green coffee beans to associated storage silos; selectively discharging pre-determined quantities of between two and five different types of green coffee beans from the storage silos into a cumulative weigher, weighing each quantity of green coffee beans delivered to the weigher in turn to produce a predesired batch of mixed green coffee beans; delivering the coffee beans into a roasting chamber, agitating the beans by continuously raising the beans from the bottom of the chamber to the top, delivering hot combustion gases into the chamber through separate inlets, one delivering the gases tangentially to the movement of the coffee beans in the chamber and the other at substantially right angles thereto , the combustion gases being maintained between 300°C and 650°C; after the coffee beans have been roasting for some time, delivering a continuous spray of water onto the roasting beans and continuing the ‘ roasting; stopping the roasting after a preset time; discharging the coffee beans; cooling the coffee beans by air; then testing the batch of roasted coffee beans for colour and taste and, if acceptable, delivering the coffee beans for one of a whole coffee bean blending operation and a coffee blending and grinding operation; and packing the coffee by weighing, evacuating air and introducing nitrogen. A process as claimed in claim 1, in which the continuous spraying of water is carried out for between 7.5 and 20% of the total roasting time. A process as claimed in claim 1, in which the continuous spraying of water is carried out for approximately 10% of the total roasting time. A process as claimed in any preceding claim, comprising precooling the coffee beans by further spraying the coffee beans with water before the beans are discharged out of the roasting chamber. A process as claimed in any preceding claim, in which the combustion gases are heated to one temperature, then the temperature is reduced, and finally, the temperature is increased again, in each case the temperature being with the range specified. A process as claimed in claim 5, in which the final temperature is greater than the initial temperature. A process as claimed in any preceding claim, in_ which the roasting is carried out for between 300 and 475 seconds. A process as claimed in claim 7, in which the roasting is carried out for between 350 and 475 seconds. A process as claimed in any preceding claim, in which the precooling of the coffee beans is carried out for between 200 and 350 seconds. A process as claimed in any preceding claim, in which the combustion gases are heated to between 325°C and 675°C. A process as claimed in any preceding claim, in which the agitation of the coffee bean is carried out by rotating a paddle wheel vigorously in the combustion chamber so that the coffee beans are carried up the combustion chamber and then thrown down across the path of the incoming gases. A process substantially as described herein with reference to and as illustrated in the accompanying drawings. Coffee beans produced in accordance with the process of any preceding claim.