JPH0220249A - Method for decaffeinating raw coffee bean - Google Patents

Abstract

PURPOSE:To decaffeinate raw coffee beans by a method nontoxic to human bodies without losing active ingredients by pressurizing and heating the raw coffee beans in the presence of water, treating the coffee beans with specific combination of C2H5OH and CO2 and then drying the treated coffee beans. CONSTITUTION:Raw coffee beans are pressurized and heated in the presence of water and then dipped in an aqueous solution of ethyl alcohol in a concentration so as not to destroy cell tissues thereof to produce pretreated raw coffee beans (pretreating step). The pretreated raw coffee beans are subsequently brought into contact with a mixed solvent consisting of CO2 in a supercritical state and an aqueous solution of ethyl alcohol in a concentration so as not to destroy cell tissues thereof or CO2 in the supercritical state and water to extract caffeine (extracting step). The raw coffee beans after extracting the caffeine are then dried (drying step). Thereby, decaffeination of the raw coffee beans is carried out. Only the caffeine present on the peripheries of the cells in the coffee beans is relatively rapidly extracted to minimize elution of proteins, fats and saccharides which are active ingredients of the coffee according to the above-mentioned method.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a decaffeination method for removing caffeine from green coffee beans.

(Prior Art) Caffeine is contained in coffee, black tea, green tea, etc., and its physiological effects on the human body have been known for a long time, and is used as a stimulant, diuretic, or cardiotonic agent. However, these properties of caffeine interfered with sleep9.
, it can actually have a harmful effect on people with heart disease, so in recent years there has been a trend towards preferring decaffeinated coffee, in which all caffeine has been removed from coffee. Some are known.

Conventionally known decaffeination methods include (1) water extraction method, (2) organic solvent extraction method, and +31 supercritical gas method.

(1) Water extraction method This method is known, for example, from Japanese Patent Publication No. 59-41692, in which caffeine is extracted with boiling water at 70 to 120 C after green coffee beans have sufficiently absorbed water. Although it is the simplest and cheapest method, it loses not only caffeine but also a considerable amount of coffee's active ingredients such as protein, fat, and sugar, and the tannins change due to heat, resulting in a loss of taste and color. Therefore, an improved water extraction method has been proposed in which the extract obtained by this water extraction method is treated with a caffeine adsorbent such as activated carbon to adsorb and remove caffeine, and then the extract is absorbed into green coffee beans while drying. (For example, Japanese Patent Publication No. 59-46576). According to this improvement method, some of the active ingredients of coffee are returned to the green coffee beans, so the taste of coffee can be improved and the concentration can be increased.However, due to the severe deterioration of components such as tannins and polyphenols, the discoloration is severe and peculiar. A taste is produced.

(2) Organic solvent extraction method This method is known, for example, from Japanese Patent Publication No. 59-41578, in which green coffee beans are made to sufficiently absorb water, and then organic solvents (such as trichloroethylene, cyclomethane fr, This is a method to extract all of the caffeine by causing the action of

Organic solvents such as trichlorethylene have a high solubility for caffeine, so they can remove caffeine with an effective K (over 95X), but organic solvents not only remove caffeine but also remove the active ingredients of coffee, so deterioration can only be done by water extraction. It's not very good, but it's a problem in terms of taste. Further, since many of the organic solvents used in this method are harmful to the human body, even a small amount of residual organic solvents is not favorable for health. Therefore, an improved organic solvent extraction method has been proposed in which the extract obtained by this organic solvent method is treated with an adsorbent such as activated carbon to adsorb and remove caffeine, and then the remaining extract is reabsorbed into green coffee beans. (For example, Japanese Patent Publication No. 57-27103). According to this improved method, since the organic solvent is easily diffused, it is easy to treat after re-adsorption, and there is little deterioration of the components to be reabsorbed. Problems still exist.

(3) Supercritical gas extraction method This method is known, for example, from Japanese Patent Publication No. 59-41377, in which an inorganic compound (in most cases carbon dioxide) is brought to a critical state under high pressure, and coffee is extracted with sufficient water. This is a method of decaffeinating by contacting green beans in a heated state (around 100C), and since a compound that is harmless and does not change the taste can be used as an extraction solvent, it is possible to use the above-mentioned water extraction method, its improved method, or the above-mentioned water extraction method. The organic solvent extraction method and its improved methods are excellent, but since the water activity is increased under heating, there is a risk that the structure of the green coffee beans may be destroyed to some extent, and the ultra-high pressure removes chlorophyll and tannin-based substances. There is a problem in that it causes deterioration in quality and lowers the commercial value of green beans.

(Problems to be Solved by the Invention) In view of the above points, the present invention seeks to provide a method for decaffeinating green coffee beans in a manner that is harmless to the human body without losing the active ingredients of coffee. be.

(Means for Solving the Problems) The present invention involves pressurizing and heating green coffee beans in the presence of water,
Thereafter, there is a pre-treatment process in which pre-treated green coffee beans are produced by immersing the green coffee beans in an aqueous solution of ethyl alcohol at a concentration that does not destroy cell tissue; Ethyl alcohol aqueous solution at a concentration that does not destroy cell tissue or 002 in a supercritical state
This is a decaffeination method for green coffee beans, which is characterized by comprising an extraction step of extracting caffeine by contacting with a mixed solvent consisting of coffee beans and water, and a drying step of drying the green coffee beans from which the caffeine has been extracted.

The method of the present invention will be explained in detail below.

(Pretreatment Step) The internal state of green coffee beans as a result of observation by the present inventor using an electron microscope is shown in the first picture.

As shown in FIG. 1(a)K, it was confirmed that the caffeine 2 in the green coffee beans 1 was present attached to the periphery of the cells 3. Therefore, from 1 part of green coffee beans to 2 parts of this caffeine.
In order to remove this, as shown in Figure 1 (b), alcohol is applied from outside 1, and this alcohol does not penetrate into the cells 3, but only between the cells, thereby reducing the distance between the cells. It was confirmed that spreading was effective as a pretreatment for decaffeination using CO2 gas in a supercritical state. In addition, in the conventional water extraction method, organic solvent extraction method, and supercritical gas extraction method, water, organic solvent, or supercritical gas applied from the outside is permeated into the cells 3, as shown in Figure 1-1. This method is based on a method that swells cells.

FIG. 2 is a schematic diagram of a pretreatment apparatus for carrying out the decaffeination method according to the present invention. In the figure, person is a belt conveyor that transports green coffee beans, B is a packet elevator that transports green coffee beans upward, and C is a valve. 1 is a notch hopper into which the green coffee beans to be decaffeinated are placed; 2 is a receiving hopper; and 5 is a pressure vessel for decaffeinating the green coffee beans; Hot water, cold water tank 5
From the ethyl alcohol aqueous solution tank 6, a 2 to 60% ethyl alcohol aqueous solution is supplied through valves C and -, respectively.

In addition, at the top of the pressure vessel 6 there is an inlet 3a for green coffee beans.
A rotating blade 3b for stirring is provided inside, and a discharge valve 3C is provided at the bottom. Note that 7 is a weighing hopper.

Next, a process for decaffeinating green coffee beans using the above-mentioned pre-processing device will be explained.

The green coffee beans placed in the cutting hopper 1 are conveyed by a belt conveyor A, lifted by a packet elevator B, and placed in a receiving hopper 2.

After opening the input port 3a of the pressure vessel 5 and introducing green coffee beans from the receiving hopper 2 into the pressure vessel 3, the input port is opened! a', open the valve C'ft from the hot water tank 4, supply a predetermined amount of hot water (80 to 15 oc), and then supply the predetermined pressure (
Pressurized steam of 1.5 to 4 kt/cm') is supplied into the pressure vessel 3 and steamed for a predetermined time (5 to 30 minutes).

At this time, the rotary blade 5bK is used to stir the green coffee beans so that they are evenly steamed. During steaming, the internal pressure of the pressure vessel 3 (
The amount of steam is controlled so that the steaming temperature is always constant, and the temperature inside the container is also monitored.

If the temperature is low, the vapor pressure of water is low, and the diffusion of moisture into the green coffee beans is slow, so pretreatment takes a long time and the quality of the green coffee beans deteriorates. Therefore, it is preferable to raise the vapor pressure of the water at a relatively high temperature and to process the green coffee beans in a short period of time without deteriorating the quality, as this increases the processing speed of the equipment. The inventors of the present invention conducted various studies on this condition, and found that at temperatures above 150C, the vapor pressure becomes too high, making it necessary to take into account the pressure resistance of the device. Wheel wood, pressure 1.5-4 ky/tx2, temperature 80, with knowledge that deterioration of green beans is unavoidable.
A preferable tL is in the range of ~150C.

I discovered something.

After the completion of steaming for a predetermined period of time, the internal pressure of the pressure vessel 3 is lowered, and the hot water remaining in the vessel is discharged.

Next, an ethyl alcohol aqueous solution (2 to 30%) at a predetermined temperature is extracted from the ethyl alcohol aqueous solution tank 6 using Parv C.
is introduced into the pressure vessel 6 in a predetermined amount. The green coffee beans are immersed in the pressure vessel 3 for a predetermined time (60 to 200 minutes), and the interior of the container is maintained at a predetermined temperature (10 to 50 C), and the rotary blades 3b are rotated to gently stir the green coffee beans. During this time, some of the caffeine in the green coffee beans is eluted.

If the ethyl alcohol concentration is 30% or more, the ethyl alcohol remaining in the green coffee beans cannot be ignored, and when used as a coffee liquid, it will give off an unpleasant odor, which is undesirable. Since green coffee beans cannot be obtained in the state shown in the figure, the concentration of the aqueous ethyl alcohol solution in the pretreatment step is preferably in the range of 2 to 30%, as described above.

Further, a temperature of 10 to 50C during immersion in the aqueous ethyl alcohol solution having the above concentration in the pretreatment step was sufficiently effective. Of course, it can be carried out at other temperatures, but it does not require cooling or heating equipment or power.
In particular, if the temperature is higher than 50C, the vapor pressure of ethyl alcohol increases and a pressurized container is required9, which is not economical.

After soaking for a predetermined time, the ethyl alcohol aqueous solution is discharged from the pressure vessel 6, and the take-out valve 3c is opened to take out the green coffee beans inside. The rotary blade 3b is fully rotated to guide all green coffee beans to the take-out valve 3C so that no green coffee beans remain in the container.

The green coffee beans taken out from the pressure vessel 3 are conveyed by a vibrating conveyor A.

The pretreated green coffee beans conveyed by conveyor A are lifted by packet elevator B and sent to weighing hopper 7.
Here, it is weighed and supplied in predetermined amounts (for example, the total amount) to an extraction process using supercritical CO2 gas.

In the pre-treatment step of the present invention, the coffee beans are treated as shown in FIG.
This method facilitates the next extraction process by converting the coffee beans into the state shown in Figure 2.
This is essentially different from the known water extraction method, which requires a long treatment (several hours) to extract more than 90%;
This is a process in which green coffee beans are made into a state as shown in FIG. 1 (b) K by a short treatment of 30 minutes.

(Extraction Step) FIG. 5 is a schematic diagram of the extraction step for carrying out the decaffeination method according to the present invention.

The pretreated green coffee beans produced in the pretreatment step are filled into extraction towers 8a and 8b, and first, a mixed solvent of supercritical 002 gas and ethyl alcohol aqueous solution or supercritical CO is added to the lower part of the extraction tower 8a. A mixed solvent of □ and water is continuously supplied, and caffeine is selectively extracted with the mixed solvent. In this case, the former mixed solvent has a faster extraction rate than the latter, so the former is preferable. Co2 in a supercritical state means a temperature of 40 to 90°C and a pressure of 100 to 3
00 kg/'cIrL2G. In a supercritical state, the diffusion rate is approximately 100% higher than that of a liquid.
It is possible to increase the extraction speed of caffeine by a factor of two.

The present inventors have discovered the following relationship between CO2 in a supercritical state and caffeine in green coffee beans.

(1) The solubility of caffeine in supercritical 002 tends to increase as the density of CO2 gas increases, and the density of C02 increases as pressure increases and decreases as temperature increases.

(1)) The diffusion coefficient in green coffee beans increases as the temperature rises above the critical temperature of CO2, 31C.

(c) Green coffee beans may deteriorate if they are processed for a long time at temperatures above 90C.

(d) The pressure is 300k1. /cIL2 or more is not preferable because the equipment cost is too high.

The present invention provides the above (1), (bl, (℃), and (d
), the preferable ranges are 40 to 90°C for temperature and 100 to 300 kg/crn2 for pressure.

In addition, the ethyl alcohol aqueous solution has an ethyl alcohol concentration of 30% or less, and has a concentration of 0.1 to 3.0 vr with respect to the C02.
It is preferable to add within the range of tX. If more than this is added, useful components other than caffeine in the green coffee beans will also be extracted, leading to deterioration of flavor components, which is not preferable.

Next, the mixed solvent and caffeine gas coming out of the extraction tower 8a is introduced into the caffeine separation tower 10 through the line 9, and countercurrently contacts the water or alcohol aqueous solution supplied through the line 11. The mixed solvent substantially free of caffeine is recovered through line 12, while the water or alcohol aqueous solution from which all caffeine has been extracted is taken out of the system through line 13. The mixed solvent substantially free of caffeine is pressurized by the pressure drop in the circulation line in the circulation bonder 14, adjusted to a predetermined temperature in the heat exchanger 15, and then recirculated and supplied to the extraction column 8a through the line 16. In addition, in Figure 3, 17 is CO2
Make-up supply line.

After processing for a predetermined time, switch to extraction tower 8b, and then switch to extraction tower 8a.
Remove the green coffee beans inside.

The caffeine separation column 10 shown in FIG. 3 extracts caffeine from the mixed gas in the line 9 by countercurrent extraction with water or an aqueous ethyl alcohol solution, and the pressure is 100~
300ky/rent 2a1 temperature is 40~80C and extraction tower 8a
, 8b are preferred for reducing energy consumption.

As the caffeine separation column 10, an adsorption # (for example, a nine-filled horizontal column filled with active buttons) that selectively adsorbs caffeine can also be used.

(Drying Step) The decaffeinated green coffee beans taken out from the extraction tower 8a are put into a dryer 18 as shown in FIG. Warm water is circulated through the jacket 18a of the dryer 1B, and during drying, the green coffee beans are sampled at appropriate time intervals to check the degree of dryness, and after drying for a predetermined period of time (for example, 14 hours), they are taken out from the outlet 18b. Pay out.

Since green coffee beans have been processed by being heated and recycled, it is not preferable to use high temperatures in the drying process. Therefore, it is preferable to dry at a relatively low temperature of 70C or less over a long period of time.

Furthermore, the drying step is preferably carried out under reduced pressure conditions or at a low temperature.

The dried green coffee beans are conveyed by a conveyor A, lifted by a packet conveyor B, and transferred to an exhibit hopper 19. In this way, decaffeinated green coffee beans are produced.

(Example 1) An example is Toshite, 10k1. green coffee beans (Colombia)
together with 1 DJ of water in a pressure vessel 3 as shown in Figure 2.
and swelled at about 120C for 8 minutes. The swollen green coffee beans T-40C were immersed in a 5% ethyl alcohol aqueous solution 207 for 120 minutes to produce pretreated green coffee beans.

Next, 5 kg of pretreated green coffee beans were placed in an extraction column AALC as shown in Fig. 3, and the temperature was 80°C and the pressure was 200 kg.
A mixed solvent in which 2 x 10 parts by weight of a 15% ethyl alcohol aqueous solution was added to 0021 parts by weight was supplied at a rate of 2 DOk)/h for 5 hours under the condition of 0.0021 parts by weight, and then the decaffeinated coffee was poured into the extraction column 8a. After taking out a small amount of raw beans,
The pressure is 25011 in the vacuum dryer 18 as shown in Figure 4.
It was dried at a Hgs temperature of 70C.

As a result, the decaffeination rate was 90.2 as shown below.
Decaffeinated green coffee beans of X were obtained.

Decaffeination rate = (155-1115)/155 X
I GO = 9[12N Also, when the green coffee beans decaffeinated according to the present invention are compared with the green coffee beans decaffeinated according to the conventional method, the green coffee beans decaffeinated according to the present invention are close to the green beans before treatment. It had excellent properties, with little deformation in color, little shrinkage or discoloration, and even some gloss on the surface.

Next, regarding the green coffee beans obtained according to the present invention, [υ
Color difference between powder and extract, (2) Volume change due to roasting,
(3) Compare the turbidity of each extract with that of decaffeinated coffee produced by a conventional method.

(1) Color difference Powder color difference refers to the color difference in coffee powder obtained as a result of roasting and grinding green coffee beans, and coffee extract color difference refers to the total color difference in coffee extract obtained from coffee powder.
Generally speaking, high-quality coffee is said to have a deep red color.

The following table compares the color difference between green coffee beans decaffeinated according to the present invention and green coffee beans decaffeinated according to the conventional method.

Raw materials from Colombia were used for the coffee beans, and a colorimeter Z-100 manufactured by Nippon Denshoku Kogyo Co., Ltd. was used as a colorimeter.
All 1DP types were used.

Non-decaffeinated 73.25 8
3.92 By conventional method 71.33 8
4.51 Decaffeinated according to the present invention 7°, 24 84.91
As can be seen from the decaffeinated results, the roasting degree was adjusted to bring the powder color difference as close as possible between the green coffee bean powder obtained by the method of the present invention and the coffee green decaffeinated by the conventional method. Comparing the color difference between the coffee extract and the bean powder, the color difference value of the green coffee beans obtained by the method of the present invention is not much different from that of the conventional product, and exhibits a bright reddish color.

(2) Change in volume due to roasting It is known that green coffee beans absorb water and increase in volume when roasted, and this increase in volume has a large effect on the extraction rate of coffee liquid.

The following table shows the volume and volume of green coffee beans decaffeinated according to the present invention using raw materials produced in Colombia and the green coffee beans decaffeinated by the conventional method, which were roasted and had almost the same moisture content. Volume and volume increase rate are compared with almost the same volume content.

Non-decaffeinated 25.8 42.7
166 Decaffeination according to the present invention 28°8 41°2 1
43 By water extraction method 23.5 32.5
As can be seen from the results of 158 decaffeination, the volume increase rate of green coffee beans decaffeinated according to the present invention due to roasting is smaller than that of green coffee beans that are not decaffeinated.
The volume increase rate increases dramatically compared to green coffee beans that have been decaffeinated using the water extraction method. As a result, the coffee extraction rate is significantly improved, the green coffee beans become larger, and the product value increases due to the good appearance.

(31 TurbidityCoffee extract tends to become cloudy and oxidize over time after extraction, causing changes in color and taste.Therefore, many green coffee roasters generally ask coffee shops about the process after extraction. If more than 30 minutes have passed, instructions are given to discard the item.

Figure 5 is a graph showing a comparison of the temporal changes in brightness of green coffee beans decaffeinated by the method of the present invention and green coffee beans decaffeinated by the conventional method; (B) raw coffee beans, (B) decaffeinated by the method of the present invention, (C)
is green coffee beans decaffeinated by water extraction method, (D
) is coffee that has been decaffeinated using an organic solvent extraction method. The horizontal axis of the club is time, and the vertical axis is brightness.

From this graph, it can be seen that the green coffee beans according to the present invention have a high brightness even with the passage of time, in other words, the turbidity is extremely low.

In addition to the above results, we conducted a cup test on a large number of people to compare coffee extracted from green coffee beans using the decaffeinated method of the present invention with coffee extracted from green coffee beans using the conventional method. It received the highest ratings for both taste and quality.

The above-mentioned values or ranges for the temperature, pressure, and time in each treatment of the decaffeination method according to the present invention are preferred and are by no means limiting.

(Example 2) In Example 1, green coffee beans were decaffeinated by varying the ethyl alcohol concentration tm of the ethyl alcohol aqueous solution used in the extraction process, and the results shown in Table 1 were obtained.

From this, it can be seen that the ethyl alcohol concentration is preferably 30X or less, and most preferably in the range of 2 to 15%.

Comparative Example 1> In Example 1, the pretreatment step was carried out under conditions outside the present invention, and the following extraction step was carried out in the same manner as in Example 1. Table 2 shows the results obtained under the following conditions.

(Effects of the Invention) According to the present invention, only the caffeine present around the cells of coffee beans is extracted relatively quickly, and the elution of proteins, fats, and sugars, which are the active ingredients of coffee, is minimized.

For this reason, when extracted as coffee, there is almost no deterioration in taste or color change compared to coffee that is not decaffeinated, and as green coffee beans, there is no browning phenomenon or shrinkage of the outer skin of the beans. , the commercial value is higher than that of green coffee beans that have been decaffeinated using conventional methods. Alternatively, since the C02 and ethyl alcohol used in the decaffeination treatment are harmless to the human body, there is no health problem even if they remain in the coffee beans.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of green coffee beans to explain the basic concept of the decaffeination method according to the present invention in comparison with the conventional decaffeination method, and Figure 2 is the pretreatment process of the decaffeination method according to the present invention. FIG. 3 is a schematic diagram of an apparatus for carrying out the entire decaffeination extraction process according to the present invention. FIG. 4 is a schematic diagram of an apparatus for carrying out the entire drying process of the present invention. The figure is a graph showing the brightness of coffee extracted from green coffee beans decaffeinated according to the present invention in comparison with coffee produced by a conventional method.

Claims (7)

[Claims] (1) A pretreatment step in which green coffee beans are pressurized and heated in the presence of water, and then immersed in an aqueous ethyl alcohol solution at a concentration that does not destroy the cell tissue of the green coffee beans to produce pretreated green coffee beans; The pretreated green coffee beans are treated with supercritical CO_2 and an ethyl alcohol aqueous solution at a concentration that does not destroy the cell tissue of the green coffee beans, or with supercritical CO_2.
A method for decaffeinating green coffee beans, characterized by comprising an extraction step of extracting caffein by contacting with a mixed solvent consisting of coffee beans and water, and a drying step of drying the green coffee beans from which caffein has been extracted. (2) In the pretreatment process, green coffee beans are pressurized at 1.5 to 4 kg/cm^2 in the presence of water, and
The decaffeination method according to claim 1, wherein the method is heated at 50°C. (3) The decaffeination method according to claims 1 and 2, wherein the concentration of the ethyl alcohol aqueous solution in the pretreatment step is 2 to 30%. (4) Claims 1 to 3, wherein the temperature of the aqueous ethyl alcohol solution in the pretreatment step is 10 to 50°C.
Decaffeination method described in Section. (5) In the extraction process, the temperature of the mixed solvent is 40 to 90
C and a pressure of 100 to 300 kg/cm^2G. (6) The decaffeination method according to any one of claims 1 to 5, wherein in the extraction step, the concentration of ethyl alcohol in the aqueous ethyl alcohol solution is 30% or less. (7) The decaffeination method according to any one of claims 1 to 6, wherein the temperature of the drying step is 70°C or lower.