Method for removing caffeine from unroasted coffee beans
By wetting unroasted coffee beans with controlled temperature water and using supercritical carbon dioxide, the method addresses sugar loss and flavor deterioration in decaffeination, resulting in high-quality decaffeinated coffee.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- TOHOKU UNIV
- Filing Date
- 2021-11-18
- Publication Date
- 2026-06-01
AI Technical Summary
Conventional decaffeination processes using supercritical carbon dioxide for unroasted coffee beans often result in the removal of sugars due to excessive use of room-temperature water, leading to flavor deterioration.
A method involving a pretreatment of wetting unroasted coffee beans with water at 30°C to 90°C, followed by decaffeination using supercritical carbon dioxide and a controlled post-treatment drying process to maintain flavor.
The method effectively suppresses sugar removal and preserves coffee flavor by optimizing moisture control during decaffeination, ensuring high-quality decaffeinated coffee.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to a method for removing caffeine from unroasted coffee beans.
Background Art
[0002] Coffee is a beverage obtained by extracting coffee bean-containing components with water at an appropriate temperature from coffee beans roasted and ground into a powder. Coffee contains components such as carbohydrates (sugars), proteins, vitamins, minerals, caffeine, and tannins.
[0003] Caffeine is a bioactive ingredient, and it is known to have effects on the central nervous system and blood pressure, and a diuretic effect. In recent years, the demand for coffee from which caffeine has been removed (decaffeinated coffee) has been increasing.
[0004] Coffee beans contain caffeine at a weight of about 1% based on the weight of the coffee beans when dry, depending on the type. Decaffeinated coffee, although it varies depending on the definition of countries and regions, for example, coffee in which the caffeine content in coffee beans when dry is 0.1% or less of the total weight, or coffee in which the caffeine content contained in coffee beans is less than 3% of the initially contained content (the content before decaffeination).
[0005] The above decaffeination is performed, for example, by extracting and removing caffeine from unroasted coffee beans. Methods for extracting caffeine from unroasted coffee beans are known, such as extraction with an organic solvent, extraction with water, and extraction using a supercritical fluid such as carbon dioxide.
[0006] Patent Document 1 describes a method for decaffeinating unroasted coffee beans (green coffee) using a supercritical fluid of carbon dioxide.
[0007] Patent Document 2 describes the use of crude caffeine produced by a decaffeination process of unroasted coffee beans using a supercritical fluid of carbon dioxide as an ingredient in food, pharmaceuticals, cosmetics, nutritional supplements, and biopharmaceuticals. [Prior art documents] [Patent Documents]
[0008] [Patent Document 1] Japanese Patent Application Publication No. 3-160949 [Patent Document 2] International Publication No. 2012 / 051287 [Overview of the Initiative] [Problems that the invention aims to solve]
[0009] However, in conventional decaffeination processes using supercritical carbon dioxide fluid for unroasted coffee, a large amount of room-temperature water is used to quickly wet the unroasted coffee beans as a pretreatment before decaffeination. This has the disadvantage of removing sugars from the unroasted coffee beans due to contact with a large amount of water, thus impairing the coffee's flavor.
[0010] Therefore, the present invention has been made in view of the above-mentioned problems, and aims to provide a method for removing caffeine from unroasted coffee beans that can perform decaffeination treatment on unroasted coffee beans while suppressing the deterioration of the coffee's flavor. [Means for solving the problem]
[0011] The present invention provides a method for removing caffeine from unroasted coffee beans, comprising a pretreatment of wetting the unroasted coffee beans with water, a decaffeination treatment of extracting and removing caffeine from the wet unroasted coffee beans using supercritical carbon dioxide, and a posttreatment of drying the wet unroasted coffee beans after the decaffeination treatment, wherein in the pretreatment, the unroasted coffee beans are wet by contacting them with water at a temperature of 30°C to 90°C. [Effects of the Invention]
[0012] According to the present invention, in the pretreatment before decaffeination, unroasted coffee beans are moistened by contacting them with water at a temperature of 30°C to 90°C. This allows for sufficient moistening without using a large amount of room temperature water, suppressing the removal of sugars from the unroasted coffee beans and preventing deterioration of the coffee's flavor even after decaffeination. [Brief explanation of the drawing]
[0013] [Figure 1] Figure 1 is a graph showing the Brix values of unroasted coffee beans (sample numbers 1-8) that underwent each treatment in Verification Experiment 1. [Figure 2] Figure 2 is a graph showing the cupping test scores of coffee obtained by roasting unroasted coffee beans (sample numbers 1, 6, and 8) that underwent each treatment in Verification Experiment 2. [Modes for carrying out the invention]
[0014] <Outline of the Invention> The inventors investigated the amount of sugars remaining in unroasted coffee beans and the quality of coffee obtained through a wet treatment process, which is a pretreatment for decaffeination of unroasted coffee beans, when wet treatment was performed under various conditions.
[0015] As a result, we discovered that by controlling the water temperature during the wetting process, sufficient wetting can be achieved without using large amounts of water, and conditions were found that suppressed the removal of sugars from unroasted coffee beans. This invention is based on this finding.
[0016] <Embodiment> The method for removing caffeine from green coffee beans according to an embodiment of the present invention first performs a pretreatment of wetting the green coffee beans with water, and then uses supercritical carbon dioxide to perform a decaffeination treatment of extracting and removing caffeine from the wet green coffee beans, and subsequently, after the decaffeination treatment, performs a post-treatment of drying the wet green coffee beans.
[0017] As the types of green coffee beans to be subjected to caffeine removal, it can be preferably applied to Arabica varieties such as Bourbon, Caturra, Mundo Novo, Catuaí, Typica, Sumatra, Mocha, Blue Mountain, etc., and can be preferably applied to Bourbon in particular. There is no particular limitation on the types of applicable green coffee beans, and it can also be applied to Arabica varieties other than those described above, as well as Robusta varieties and hybrids. There is no particular limitation on the origin of the coffee beans either, but for example, those produced in Rwanda can be preferably used.
[0018] <Pretreatment> The pretreatment of wetting the green coffee beans with water will be described. In this embodiment, in the pretreatment, the green coffee beans are brought into contact with water at 30°C or higher and 90°C or lower to be wetted. The temperature of the water brought into contact with the green coffee beans is preferably 40°C or higher and 80°C or lower.
[0019] In the pretreatment, the weight of water contained in the green coffee beans (water content) with respect to the dry weight of the green coffee beans is preferably 25% or more and 50% or less, and more preferably 35% or more and 40% or less.
[0020] In the pretreatment, the weight of water brought into contact with the green coffee beans with respect to the dry weight of the green coffee beans is preferably 30% or more and 100% or less, and more preferably 40% or more and 60% or less. If the amount of water brought into contact is too much, the amount of saccharides removed will increase. Also, if the amount of water brought into contact is too little, it may be difficult to control the above water content.
[0021] In the pretreatment, the time for contacting the green coffee beans with water to moisten them is preferably 3 hours or more and 24 hours or less. If the time is too long, too much saccharide will be removed. If the time is too short, the beans may not be sufficiently hydrated, making it difficult to control the above moisture content.
[0022] By contacting the green coffee beans with water at 30°C or higher and 90°C or lower as described above to moisten them, it becomes possible to sufficiently moisten the beans without using a large amount of water, and it is possible to suppress the removal of saccharides in the green coffee beans during the pretreatment.
[0023] <Decaffeination treatment> The decaffeination treatment using supercritical carbon dioxide will be described in more detail. In this embodiment, in the decaffeination treatment, supercritical carbon dioxide is used to extract and remove caffeine from the moistened green coffee beans. The critical point of carbon dioxide is 31.1°C and 7.38 MPa. Caffeine is extracted and removed from the moistened green coffee beans using supercritical carbon dioxide at 31.1°C or higher and 7.38 MPa or higher.
[0024] As the decaffeination treatment using supercritical carbon dioxide, the treatments under the conditions described in Patent Document 1 and Patent Document 2 can be preferably applied. For example, the temperature of the supercritical carbon dioxide used in the decaffeination treatment is 60°C or higher and 140°C or lower, and the pressure is 10 MPa or higher and 45 MPa or lower. Also, for example, the time during which the decaffeination treatment is performed is 2 hours or more and 12 hours or less. At this time, it is desirable that the weight of the carbon dioxide used with respect to the dry weight of the green beans is 20 to 500 times in terms of weight ratio.
[0025] By the above decaffeination treatment, the caffeine content in the coffee beans during drying is made 0.3% or less of the total weight, or the caffeine content contained in the coffee beans is made less than 30% of the initially contained content (the content before decaffeination) to remove caffeine.
[0026] <Post-treatment> This section describes the post-processing for drying unroasted coffee beans. In this embodiment, after decaffeination, the moist unroasted coffee beans are dried.
[0027] In post-processing, for example, moist unroasted coffee beans are dried in an oven. A preferred oven temperature is, for example, 40°C to 80°C. A preferred dew point temperature for oven drying is, for example, 35°C to 50°C.
[0028] Alternatively, for example, damp, unroasted coffee beans can be dried by blowing air on them. The air blown on the coffee beans could be hot air from a heater, for example.
[0029] Alternatively, moist, unroasted coffee beans can be dried in the sun.
[0030] There may be differences in the sugar content of unroasted coffee beans between hot air drying and wet drying methods such as oven drying, so it is preferable to select the appropriate drying method.
[0031] In the drying process described above, the drying is controlled so that the moisture content after the drying process is 6% to 18%, preferably 10% to 15%.
[0032] When water enters unroasted coffee beans, enzymes trigger a fermentation reaction, which can impair the flavor. As described above, drying the beans after decaffeination controls the moisture content, improving the quality of the coffee's flavor and extending its shelf life.
[0033] The decaffeinated, unroasted coffee beans obtained as described above are then roasted to the desired degree. The resulting roasted coffee beans are then ground in a coffee mill or similar device, and coffee can be brewed by dripping or other methods.
[0034] <Mechanism and Effects> As described above, in the decaffeination method for unroasted coffee beans, the beans are moistened by contacting them with water at a temperature of 30°C to 90°C as a pretreatment before the decaffeination process.
[0035] By performing the above pretreatment, sufficient wetting can be achieved without using large amounts of water, and the removal of sugars from unroasted coffee beans can be suppressed. Furthermore, the deterioration of coffee flavor can be suppressed even after decaffeination.
[0036] <Verification experiment> (Verification Experiment 1) Unroasted coffee beans (Rwandan Arabica variety (Bourbon)) were prepared as sample number 1. Sample number 1 consisted of unroasted coffee beans that had not undergone any pre-treatment, decaffeination treatment, or post-treatment for decaffeination.
[0037] Unroasted coffee beans for sample number 2 were prepared. Unlike the unroasted coffee beans for sample number 1, the unroasted coffee beans for sample number 2 were subjected only to a pretreatment for decaffeination. In this pretreatment, 35g of room temperature water was placed in contact with 70g of unroasted coffee beans (63g dry weight) overnight, and the unroasted coffee beans were moistened so that the weight of water contained in the unroasted coffee beans relative to their dry weight (moisture content) was 40%.
[0038] Unroasted coffee beans for sample number 3 were prepared. These unroasted coffee beans underwent pre-treatment and post-treatment compared to unroasted coffee beans for sample number 1. In the pre-treatment, 35g of room temperature water was placed in contact with 70g of unroasted coffee beans (63g dry weight) overnight to moisten the beans to a moisture content of 40%. In the post-treatment, the beans were dried using hot air from a heater under conditions of a dry-bulb temperature of 40°C and a dew point temperature of 35°C to achieve a moisture content of 8%. Note that the dew point temperature did not match the set value during this process.
[0039] Unroasted coffee beans for sample number 4 were prepared. Unlike unroasted coffee beans for sample number 1, unroasted coffee beans for sample number 4 were subjected only to a pretreatment for decaffeination. In this pretreatment, 105g of room temperature water was placed in contact with 30g of unroasted coffee beans (27g dry weight) overnight, moistening the beans to a moisture content of 80%.
[0040] Unroasted coffee beans for sample number 5 were prepared. These unroasted coffee beans underwent pre-treatment and post-treatment compared to unroasted coffee beans for sample number 1. In the pre-treatment, 40g of room temperature water was placed in contact with 80g of unroasted coffee beans (72g dry weight) overnight to moisten the beans to a moisture content of 40%. In the post-treatment, the beans were dried in an oven at 50°C to a moisture content of 6% to 18%. The dew point was not controlled during this process.
[0041] Unroasted coffee beans for sample number 6 were prepared. Unroasted coffee beans for sample number 6 were subjected to pre-treatment, decaffeination treatment, and post-treatment compared to unroasted coffee beans for sample number 1. In the pre-treatment, 40g of 80°C water was placed in contact with 80g of unroasted coffee beans (dry weight 72g) overnight to moisten the beans to a moisture content of 40%. In the decaffeination treatment, caffeine was extracted and removed using supercritical carbon dioxide at a temperature of 80°C and a pressure of 25MPa. In the post-treatment, the beans were dried to a moisture content of 14% under conditions of a dry-bulb temperature of 40°C and a dew point of 35°C.
[0042] Unroasted coffee beans for sample number 7 were prepared. Unlike unroasted coffee beans for sample number 1, unroasted coffee beans for sample number 7 were subjected only to a pretreatment for decaffeination. In this pretreatment, 40g of 40°C water was placed in contact with 80g of unroasted coffee beans (72g dry weight) overnight, moistening the beans to a moisture content of 40%.
[0043] Unroasted coffee beans for sample number 8 were prepared. Unroasted coffee beans for sample number 8 were subjected to pre-treatment and post-treatment for decaffeination compared to unroasted coffee beans for sample number 1. In the pre-treatment, 40g of 80°C water was placed in contact with 80g of unroasted coffee beans (dry weight 72g) overnight to moisten the beans to a moisture content of 40%. In the post-treatment, the beans were dried under conditions of a dry-bulb temperature of 40°C and a dew point temperature of 35°C to a moisture content of 13.5%.
[0044] The Brix values were examined for each of the unroasted coffee beans (sample numbers 1-8) that had undergone the treatments described above.
[0045] The Brix value corresponds to the amount of sugar contained in a sample and is also used as a measure of sugar content. For example, it can be obtained by measuring the refractive index of light, which changes depending on the sugar content.
[0046] Figure 1 is a graph showing the Brix values of unroasted coffee beans (sample numbers 1-8) subjected to each treatment in Verification Experiment 1. Sample number 2 had a Brix value equivalent to sample number 1. Compared to sample number 2, sample number 4 showed a significantly lower Brix value. Compared to sample number 2, samples number 7 and 8 had equivalent Brix values. Compared to sample number 2, sample number 3 had a high Brix value, and sample number 5 had a slightly lower Brix value. Compared to sample number 2, sample number 6 had an equivalent Brix value. When the Brix value falls below 3, it is thought that a large amount of carbohydrates are being removed. Except for sample numbers 4 and 5, it is thought that the removal of carbohydrates was suppressed.
[0047] Figure 1 shows that when unroasted coffee beans are moistened with excess water, the Brix value decreases due to the removal of sugars in the beans. However, when moistened with water at 40°C to 80°C, there was almost no decrease in the Brix value. Furthermore, no decrease in the Brix value was observed when decaffeination was performed using supercritical carbon dioxide.
[0048] Regarding the drying process, methods that controlled the dew point resulted in higher Brix values, while drying using an oven tended to decrease Brix values.
[0049] (Verification Experiment 2) The unroasted coffee beans (sample numbers 1, 6, and 8) that had undergone the above-mentioned treatments were then roasted and ground, extracted with water at an appropriate temperature to obtain coffee, and a cupping test was conducted.
[0050] A cupping test is a human-performed quality assessment, a sensory test in which coffee is tasted and scored. The test is conducted by qualified individuals called Q Graders or by people suitable for sensory testing (those who have been conducting sensory tests for many years). In the test, each item such as aroma, sweetness, acidity, body, balance, aftertaste, off-flavors, and texture is scored, and the evaluation is based on the total score of each item.
[0051] Figure 2 is a graph showing the cupping test scores (CT) of coffee obtained by roasting unroasted coffee beans (sample numbers 1, 6, and 8) that underwent each treatment in Verification Experiment 2. Sample number 6, which underwent pretreatment by wetting with 80°C water and decaffeination, scored at or above the cupping test score of sample number 1. Sample number 8, which was wetting with 80°C water but not decaffeined, scored slightly lower in the cupping test.
[0052] While the Brix value generally corresponds to sugar content, cupping test scores reflect the overall balance of the coffee, and a good balance can result in a high score. Results from samples 6 and 8 suggest that different tastes and aromas are produced by chemical reactions caused by heat during roasting, depending on the pre-treatment conditions and whether or not decaffeination was performed. Besides carbohydrates, other components that influence the balance of coffee include proteins (amino acids), lipids, and minerals.
[0053] As described above, sample number 6 showed suppressed removal of sugars from unroasted coffee beans, and even after decaffeination, the deterioration of the flavor of the coffee obtained after roasting was suppressed.
[0054] The present invention is not limited to the embodiments described above. For example, the decaffeination process is not limited to the conditions described above. Other conditions may be used as long as caffeine can be extracted and removed from unroasted coffee beans. Furthermore, although supercritical carbon dioxide is used for caffeine extraction, the invention is not limited to this, and other supercritical fluids can be used instead of supercritical carbon dioxide. In addition, drying methods other than those described above can be applied for post-treatment.
Claims
1. Pre-treatment involves wetting unroasted coffee beans with water, After the aforementioned pretreatment, a decaffeination process is performed in which caffeine is extracted and removed from the moistened unroasted coffee beans using supercritical carbon dioxide. After the decaffeination treatment, a post-treatment is performed in which the moistened unroasted coffee beans are dried. Equipped with, In the aforementioned pretreatment, the unroasted coffee beans are brought into contact with water at a temperature of 30°C to 90°C to moisten them. In the aforementioned pretreatment, the weight of the water to be contained in the unroasted coffee beans is 25% or more and 50% or less relative to the dry weight of the unroasted coffee beans. In the aforementioned pretreatment, the weight of the water that comes into contact with the unroasted coffee beans is 30% or more and 100% or less relative to the dry weight of the unroasted coffee beans. In the aforementioned post-treatment, the dew point temperature for drying is 35°C or higher and 50°C or lower. Methods for removing caffeine from unroasted coffee beans.
2. In the aforementioned pretreatment, the unroasted coffee beans are moistened by contacting them with water at a temperature of 40°C to 80°C. The method for removing caffeine from unroasted coffee beans according to claim 1.
3. In the aforementioned post-processing, the moistened unroasted coffee beans are dried in an oven. A method for removing caffeine from unroasted coffee beans according to claim 1 or 2.