GB2166336A

GB2166336A - Surface treatment of roasted coffee beans

Info

Publication number: GB2166336A
Application number: GB08524456A
Authority: GB
Inventors: Kenichi Toshikawa
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-10-09
Filing date: 1985-10-03
Publication date: 1986-05-08
Also published as: FR2571221A1; JPS6192534A; DE3535410A1; GB8524456D0

Abstract

A method of treating roasted coffee beans to keep such beans fresh included covering the surface of whole roasted coffee beans or of roughly ground roasted coffee beans with a shellac film which is insoluble in water and is impermeable to air. The shellac film is applied to the surface of the coffee beans using a solution of shellac in alcohol, the film being formed, for example, by soaking the beans in the solution, spraying the solution onto the beans or by placing the beans in a stream of the solution.

Description

SPECIFICATION Surface treatment of roasted coffee beans This invention relates to a method of treating roasted coffee beans to keep such beans fresh, and to roasted coffee beans which have thus been treated.

The particular color and flavour of coffee beans are realized only when the components are subjected to chemical change through a baking process called roasting. The flavour components of roasted coffee beans produced in this manner however, easily combine with moisture and oxygen in the air and are thus very unstable, and degeneration (oxidization) of the flavour begins immediately after roasting has been completed.

The speed of this flavour loss differs according to a number of factors, the weather conditions, the storage condition of the roasted coffee beans, the roasting conditions, the kind of coffee beans, etc., but the flavour is generally regarded to have been reduced by a half in a week.

Therefore, there is a great difference in the flavour, taste and body of coffee beans immediately after roasting and those roasted several days before, and accordingly the commercial value of coffee beans several days after roasting is substantially reduced.

To keep roasted coffee beans fresh, therefore, different kinds of methods have thus far been tried, and such methods as vacuum packing or gas sealed packing of roasted coffee beans have been studied and have been commercially adopted to some extent. All of these packing methods, however, involve quantities of the order of 200 gr. 500 gr. 1 kg. or 5 kg. and once the packs are opened carbon dioxide gas and component compounds of flavour generated by the roasting of the coffee beans immediately go out of the packs and outside air flows in. Thus, except for the coffee beans which are used immediately, degeneration of the flavour commences right after the packs have been opened. Accordingly, even using these methods of packing it is not possible to radically prevent the problem of flavour loss.Moreover, even using such vacuum packs or gas sealed packs, carbon dioxide is generated inside the packs by the roasted coffee beans at room temperature and the flavour component completely leaves the beans. Thus, while these methods can prevent the damaging influence of air-borne moisture and oxygen the fragrance cannot be maintained for a long time.

Since the packs are sometimes broken by the carbon dioxide generated within, special valves which discharge the gas from inside the packs but which prevent outside air from entering have been tried, or absorbent material is put in so as to absorb the carbon dioxide generated inside the packs.

These arrangements, however, do not prevent coffee beans from generating carbon dioxide, and therefore, do not serve as a solution to the problem of the degeneration of the flavour of coffee beans inside the sealed packs.

In view of the foregoing, it is object of this invention to provide treatment of coffee beans to prevent the flavour from leaving roasted coffee beans, so as to keep the beans fresh for a long time, and maintain the flavour for a long time when the beans are vacuum or gas sealed packed.

Accordingly, in one aspect, the invention provides a method of treating roasted coffee beans to keep such beans fresh, including covering the surface of whole roasted coffee beans or of roughly ground roasted coffee beans with a film which is insoluble in water and is inpermeable to air.

In another aspect, the invention provides surface treated coffee beans comprising whole roasted coffee beans or roughly ground coffee beans the surface of which is covered by a film which is insoluble in water and is impermeable to air.

In the foregoing arrangement, the surface of roasted coffee beans or of roughly ground beans is covered with a film which cuts off air permeation, especially oxygen, as described above, and carbon dioxide and flavour and taste components are prevented from leaving the coffee beans. Since oxidation by air-borne oxygen is also prevented, degeneration of the flavour and taste of coffee beans can be slowed down and the beans are kept fresh for a long time.

When packed by vacuum packing or gas sealed packing, the film prevents the coffee beans from generating carbon dioxide so that the fragrance does not leave the coffee beans inside the packs.

Moreover, the film is insoluble in both water and hot water and is not dissolved into extracted coffee, which prevents the film having an influence on the taste and flavour of the coffee.

In order that the invention may be readily understood, embodiments thereof will now be described with reference to the accompanying drawings and Examples. In the drawings: Figure 1 to Figure 6 show respective gas chromatography charts, in which Figure 1 corresponds to Example 2, Figure 2 to Example 3, Figure 3 to Example 4, Figure 4 to Comparison Example 1, Figure 5 to Comparison Example 2, and Figure 6 to a blank chart.

Coffee beans are roasted in the manner ordinarily used and then the surface of the individual beans is coated with film immediately after roasting is completed. The film must be of a nature to cut off air, oxygen in particular, other gases, moisture etc., so that air or moisture cannot affect the beans, must prevent carbon dioxide and other flavour components from leaving the beans, must be safe to the human body and yet must not act upon the coffee beans so as to affect the fragrance.

The film should also be insoluble in either water or hot water since the taste of coffee would be affected if the film melted upon extraction from the coffee beans.

Shellac is an example of a film which meets these conditions.

Shellac is a natural animal resin. Sticlac, the secretion of Laccifera (a homoptera) is used as the raw material. Shellac is transparent yellow-brown or light brown and is ordinarily available in granule or powder form. Its melting point is 70 to 80"C (though some forms melt at over 1000C). Although about 90% soluble in alcohol and 20 to 30% soluble in ether, the film is insoluble in both cold and hot water.

Refined shellac is dissolved into an alcohol, such as ethanol, and this is then applied to the surface of the coffee beans immediately after they have been roasted. When the alcohol evaporates, the shellac solidifies into a film which covers the surface of the coffee beans. When dissolving shellac into alcohol, the quantity of alcohol should be freely decided according to the kind of alcohol and other conditions.

Ordinarily, however, shellac is used at between 10 and 40% by weight, and alcohol at between 60 and 90% by weight.

In covering the surface of the coffee beans with shellac film, the thickness of the film is determined according to the desired air cut-off capacity and such a degree that the entire surface of the coffee beans is evenly covered. Ordinarily this is between 1 and 100 microns, and preferably between 10 and 50 microns.

Next, there follows a description of different methods of covering coffee beans with film. One method is to immerse the freshly roasted coffee beans immediately in film forming solution, such as an alcohol solution of shellac, so as to deposit the formed film solution onto the surface of the coffee beans.

It is preferable to put the coffee beans in a basket and to place the whole basket into a tank of film forming solution as this is an efficient way of properly soaking a large quantity of coffee beans. Soaking the coffee beans in the solution deposits a film on the surface of the beans and then when the beans dry a film is formed on the surface.

Another method is to spray an alcohol solution of shellac or other film forming solution onto the coffee beans immediately after they have been roasted, and in this way deposit the solution on the surface. In this case, it is advisable to stir or otherwise agitate the coffee beans while spraying to ensure that film forming solution is evenly deposited on the surface of the coffee beans. After spraying in this manner, the coffee beans are allowed to dry so as to form a film on the surface.

Still another method is applicable, besides the above-mentioned immersion and spray methods, in this method the coffee beans are placed in a steam of film forming solution immediately after they have been roasted. The steam of the solution deposits a film on surface of the coffee beans.

When the surface of the coffee beans is covered by a method, such as those described above, with an air cut-off film which is insoluble in both and hot water then carbon dioxide and flavour components produced by roasting are enclosed by the film. It is possible therefore to prevent oxygen in the air from acting upon the coffee beans and thus the degeneration of the fragrance can be delayed and the freshness can be maintained for a long time. When the coffee is then extracted from the coffee beans by hot water, the insoluble film on the surface of the coffee beans is not dissolved into the extracted solution of coffee and thus the taste and flavour of the coffee are not impaired. The coffee beans coated with film can be kept fresh for a long time by storing them in a cool, dark and dry place.

When the beans are to be kept for a still longer period, it is preferable to seal the filmed coffee beans in a bag or container which prevents air permeation, such as a vacuum pack or an inert gas sealed pack (nitrogen gas, for example) and then to keep the coffee beans sealed in a freezer. If packed in this manner, even after a sealed pack has been opened, if all the beans are not used immediately the remainder still retain their freshness because they are coated with film.

However, in the case of coffee beans with a surface which is not coated with film, even though such are packed and handled in the above manner carbon dioxide is generated inside the pack by the roasted beans and this and the fragrant components leave the beans if their surface is not coated with film. By the present invention, since the surface of the coffee beans is coated with film the generation of carbon dioxide is prevented, and the flavour is thus prevented from leaving the coffee beans.

Further, it is possible to impregnate a flavour into the film covering the coffee beans, for example cocoa powder can be used as a flavour. A flavour such as cocoa powder is mixed into the film forming solution and in this way it is possible to form a film containing a flavour on the surface of the coffee beans. Besides cocoa, other flavours such as vanilla essence or cinnamon may also be used. By impregnating, in this manner, a flavour into the film covering the coffee beans, it is possible to add another flavour to the original coffee flavour and enjoy coffee of a different fragrance.

In the same way, it is also possible to impregnate vitamins etc. into the film. It is also possible to cover the surface of roughly ground roasted coffee beans, after they have been ground to between two and ten pieces, with the film rather than whole roasted coffee beans Now, the present invention is described more specifically by referring to examples.

Example I One kilogram of coffee beans grown in Cuba was roasted for 8 minutes at 185"C. Immediately after cooling, the roasted coffee beans were immersed in a solution of 25% by weight of shellac and 75% by weight of ethanol. After being removed from the solution, the beans were dried and a shellac film was formed on the surface of each bean.

The coffee beans coated with shellac film prepared in this manner were ground using an ordinary cof fee mill and the coffee was extracted and then tested by ten inspectors. Meanwhile, coffee extracted from the coffee beans immediately after roasting but without being coated with shellac was also tested. The two kinds were compared but none of the ten inspectors could identify any differences in either taste or flavour between the two, and none of them felt that there was any impurity in the coffee extracted from the beans coated with shellac. From this test, it was confirmed that a shellac film covering coffee beans does not affect the taste of flavour of coffee at all.

Example 2 On July 18, 1984, roasted coffee beans were covered with shellac in the same manner as described in Example 1, and the coffee beans were vacuum packed the same day. After being kept unopened and at room temperature, the coffee beans were transferred to the Japan Foodstuff Analysis Center and were there kept at room temperature from September 11 to September 25, 1984 and were then tested by the Analysis Center.

Example 3 On September 8, 1984, roasted coffee beans were covered with shellac film in the same manner as described in Example 1, and were then packed the same day into a gas sealed pack. After being kept unopened and at room temperature, the coffee beans were transferred to the Japan Foodstuff Analysis Center and were there kept at 25 C, and at 80% relative humidity from September 22 to 25, 1984, and then tested by the Analysis Center.

Example 4 On July 18, 1984, roasted coffee beans were covered with shellac film in the same manner as described in Example 1, and were packed in a polyvinylchloride coffee bag the same day. After being kept unopened at room temperature, the coffee beans were transferred to the Japan Foodstuff Analysis Center and were kept at room temperature from September 22 to 25, 1984, and then tested by Analysis Center.

Comparison Example 1 On September 8, 1984, coffee beans roasted in the same manner as described in Example 1 were packed and sealed in a coffee bag without being in shellac film. The bag was then opened on September 10 and the coffee beans were spread out flat and kept by Japan Foodstuff Analysis Center from September 10 to 25, 1984, under constant temperature and humidity conditions of 25"C, 80% respectively. They were then tested by the Analysis Center.

Comparison Example 2 On September 19, 1984, coffee beans were roasted in the same manner as described in Example 1, and without being covered in shellac film the beans were sealed in a polyvinylchloride coffee bag the same day. After being kept unopened at room temperature, the beans were transferred to the Japan Foodstuffs Analysis Center and were kept at room temperature from September 22 to 25, 1984, and then were tested by the Analysis Center.

Coffee beans taken from before and after storage from the above Examples 2, 3, and 4, and the Comparison Examples 1, and 2, were compared and analyzed by the Japan Foodstuff Analysis Center. The results are shown in Table 1. For the test, pH was measured according to the fancy drinks inspection method "coffee type" based on the Foodstuff Hygiene Inspection Guide II, and carbon dioxide gas was measured by putting 10 gr. of ground coffee beans sample in a phial of 65 ml. capacity, which was then sealed and left to stand at room temperature for 24 hours.

The volatile component in coffee beans from Examples 2, 3, and 4, and Comparison Examples 1, and 2, was measured by gas chromatography after having been kept by the Japan Foodstuff Analysis Center.

Figure 1 to Figure 6 show respectively the gas chromatography charts of Example 2, Example 2, Example 3, Example 4, Comparison Example 1, Comparison Example 2, and a blank gas chromatography.

For gas chromatography, 10 gr. of ground sample was kept in a sealed phial of 65 ml. capacity, heated for 30 minutes at 50"C, then 2 ml. of head space gas was poured into a gas chromatography, which was operated under the following conditions.

Model: Shimazu DC-9A Detector: FID Column: 20% PEG 20M on choromosorb WHP 100-200 mesh glass tube, 3 mm x 2 mm Temperature: 250 C at sample inlet, 50 C at column (8mm)- 100 C (5 C/min) temperature rise, Detector 250 C Gas flow rate: Nitrogen 40 ml/min, Hydrogen 0.6 Kg/cm2, Air 0.5 Kg/cm2 Sensitivity: 0.16V - 102M# Recording paper feed speed: 5 mm/minute TABLE 1 Example 2 Example 3 Example 4 Comparison Comparison Example 1 Example 2 Roasting date Jul/18/84 Sep/08/84 Jul/18/84 Sep/08/84 Sep/19/84 Testing date Sep/25/84 Before Weight (g) 362 236 308 196 483 storage pH 5.6 5.1 5.1 5.2 5.1 Carbon dioxide (%) 13 After Weight (g) 362 236 308 216 483 storage Carbon dioxide (%) 6.8 4.4 5.3 0.2 10 Acid value of extracted 13.0 11.6 13.2 8.75 5.64 coffee oil Peroxide value of extracted 0.7 2.4 2.1 3.2 2.4 coffee oil (meg/Kg) Moisture content 3.8 4.3 3.9 13.0 2.1 (Normal pressure drying) (%) As shown in Table 1, the quantity of carbon dioxide after having been stored is greater in the case of Examples 2 to 4 than in that of Comparison Example 1, which indicates that carbon dioxide is prevented from leaving the coasted coffee beans.While the peroxide value indicates that coffee oil is combining with oxygen in the air and that putrefaction is advancing. The lower the value, that is the closer to zero, means that there is less deterioration of the coffee beans. In the case of Examples 2 to 4, the peroxide value is lower than that of Comparison Example 1.

In the gas chromatograph charts, Figure 1 to Figure 5, the greater number of peaks indicates a larger variety of volatile matter, while higher peaks mean a greater quantity of volatile matter. In other words, the greater number of higher peaks means that the coffee beans contain more volatile matter of different kinds that more flavour remains.

In Figure 1 to Figure 3 of Examples 2 to 4, where the beans are coated with shellac film, the results closely resemble each other in there being a greater number of peaks and those peaks are high. Whereas in Figure 4, the chart of Comparison Example 1, where the beans are not coated with shellac, the number of peaks is far less and their height is also very low. In Figure 5, the chart of Comparison Example 2 where coffee beans are not coated with shellac but are in a sealed coffee bag, the height of the peaks is lower than those of Figure 1 to Figure 3, though they are higher than those of Figure 4.

From the results, it is clear that the coffee beans coated with shellac film retain their flavour longer than unsealed coffee beans without a shellac coating, as in Comparison Example 1, and even with sealed coffee beans which have not been coated with shellac, as in Comparison Example 2, there is a significant difference in flavour preservation when compared with shellac coated beans.

40 gr. of freshly roasted coffee beans were roughly ground immediately after being roasted, and 40 gr.

of coffee beans from each of Examples 2 to 4, and Comparison Examples 1 and 2, were roughly ground after having been stored and then coffee was extracted from each, using the paper filter drip method.

With the freshly roasted coffee beans and those of Examples 2 to 4, there was quite a lot of foaming when the coffee was being extracted. With the coffee beans of Comparison Example 1, no foaming was seen at all, while with beans of Comparison Example 2, there was little foaming. When tested by ten inspectors, all of the inspectors replied that there was no difference in the taste or flavour as among the freshly roasted coffee beans and those of Examples 2 to 4.

With the coffee extracted from the beans of Comparison Example 1, all of the inspectors replied that there was no flavour at all that the taste was vomit inducing. With the coffee extracted from the beans of Comparison Example 2, five out of ten inspectors replied that the flavour was inferior to that of the freshly roasted coffee beans.

It should be understood that the foregoing descriptions are illustrative embodiments only, and therefore the scope of this invention should be determined by the appended claims.

Claims

1. A method of treating roasted coffee beans to keep such beans fresh, including covering the surface of whole roasted coffee beans or of roughly ground roasted coffee beans with a film which is insoluble in water and is inpermeable to air.

2. A method according to Claim 1, wherein the film is formed on the surface of the coffee beans by soaking the beans in a film-forming solution.

3. A method according to Claim 1, wherein a film is formed on the surface of the coffee beans by spraying a film-forming solution onto the coffee beans.

4. A method according to Claim 3, wherein the coffee beans are agitated during spraying with the film-forming solution.

5. A method according to Claim 1, wherein the film is formed on the surface of the coffee beans by placing the beans in a stream of film-forming solution.

6. A method according to any one of the preceding claims, wherein the film comprises shellac.

7. A method according to any one of claims 2 to 5, wherein the film-forming solution is a solution of shellac in alcohol.

8. A method according to Claim 7, wherein the film-forming solution contains between 10 and 40 per cent by weight of shellac and between and 90 and 60 per cent of alcohol by weight.

9. Surface treated coffee beans comprising whole roasted coffee beans or roughly ground coffee beans the surface of which is covered by a film which is insoluble in water and is impermeable to air.

10. Coffee beans according to Claim 9, in which the film is made of shellac.

11. Coffee beans according to Claim 9 or 10, in which the film is impregnated with a selected flavour.

12. Coffee beans according to Claim 9, 10 or 11, wherein the film is impregnated with a vitamin.

13. A method of treating roasted coffee beans, substantially as hereinbefore described with reference to the foregoing example 1.

14. Roasted coffee beans prepared in accordance with the foregoing example 1.

15. Any novel feature or combination of features herein described.