Preparation method of low-factor coffee
By employing low-temperature pectinase hydrolysis, synergistic extraction with liquid CO2 and a composite buffer solution, and a three-stage roasting process, the contradiction between decaffeination rate and flavor retention in decaffeinated coffee preparation has been resolved, achieving efficient, safe, and economical decaffeinated coffee production.
Patent Information
- Application Number
- CN202511705296.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-20
- Publication Date
- 2026-01-27
AI Technical Summary
Existing decaffeinated coffee preparation technologies struggle to balance high decaffeination rates with flavor retention during the decaffeination process. They also suffer from complex processes, high energy consumption, and high production costs, making it difficult to meet the demands of large-scale, high-quality production.
Coffee beans are activated by low-temperature enzymatic hydrolysis using pectinase, and extracted and dedecenolated by the synergistic effect of liquid CO2 and complex buffer solution. The lost flavor substances are replenished by coffee peel flavor liquid, and the characteristic flavor is locked in by a three-stage roasting process.
It achieves a balance between efficient decaffeination and food safety, significantly improving the quality and drinking experience of decaffeinated coffee, and ensuring the rich taste and aroma of the coffee.
Smart Images
Figure SMS_1
Abstract
Description
Technical Field
[0001] This invention relates to the food industry, and more specifically to a method for preparing decaffeinated coffee. Background Technology
[0002] As a beverage with extremely high global consumption, coffee is seeing increasing market demand for decaffeinated coffee due to rising consumer health needs and a expanding consumer base. Decaffeinated coffee caters to the needs of caffeine-sensitive individuals, those suffering from insomnia, and those in specific physiological stages, avoiding discomfort caused by caffeine intake. It is gradually becoming an important segment of the coffee industry, and the sophistication of its preparation process directly impacts product quality and market acceptance.
[0003] Current decaffeinated coffee preparation technologies still have significant shortcomings in balancing decaffeination effectiveness, food safety, and flavor preservation. Most technologies, while removing caffeine, damage the original flavor compounds and nutrients of coffee beans to varying degrees, resulting in decaffeinated coffees generally having a weak aroma and bland taste. Some technologies also suffer from complex processes, high energy consumption, and high production costs, making it difficult to meet the demands of large-scale, high-quality production. Therefore, given the limitations of the aforementioned technologies, there is an urgent need to develop a new method for preparing decaffeinated coffee. Summary of the Invention
[0004] In view of this, the purpose of the present invention is to provide a method for preparing decaffeinated coffee that, while ensuring a high decaffeination rate, retains the original flavor compounds of coffee to the greatest extent, thereby improving the quality and industrial production efficiency of decaffeinated coffee.
[0005] The objective of this invention can be achieved through the following technical solutions: This invention provides a method for preparing decaffeinated coffee, comprising the following preparation steps: S1: After washing the coffee beans, mix them with purified water and add pectinase. Let them soak in the cool, dark place, stirring regularly during the process. After soaking, filter to remove excess water to obtain enzymatically activated wet coffee beans. S2: The enzymatically activated wet coffee beans are loaded into the extraction vessel, liquid CO2 is introduced and a compound buffer solution is injected, and the extraction and dedecenoting are carried out under controlled conditions. After the extraction and dedecenoting are completed, the pressure and temperature are reduced and the CO2 is recovered. The coffee beans are then removed to obtain decenoated wet coffee beans. S3: Add coffee pericarp flavor extract to purified water and stir evenly to obtain coffee pericarp flavor liquid. Spray the coffee pericarp flavor liquid onto the surface of decaffeinated coffee beans and then vacuum dry to obtain dried decaffeinated coffee beans. S4: The dried decaffeinated coffee beans are roasted in stages, cooled, ground, and finally packaged and sterilized to obtain decaffeinated coffee.
[0006] Furthermore, in S1, the weight parts of coffee beans, water, and pectinase are 100-120 parts coffee beans, 200-260 parts water, and 0.5-2 parts pectinase, respectively.
[0007] Furthermore, the coffee beans are Arabica standard beans.
[0008] Furthermore, in S1, the low-temperature soaking temperature is 4℃-6℃; the light-protected standing time is 12h-16h; the interval for regular stirring is once every 3h-4h, the stirring speed is 30rpm-50rpm, and the duration of each stirring is 5min-10min.
[0009] Further, the preparation steps of the composite buffer solution in S2 are as follows: citric acid and malic acid are added to purified water and stirred for 10-15 minutes at a stirring speed of 100-150 rpm to obtain a mixture; then γ-cyclodextrin and glycine are added to the mixture in sequence and stirred for another 8-12 minutes at a stirring speed of 100-150 rpm; finally, sodium citrate is slowly added while stirring at a speed of 60-100 rpm until the pH of the mixture stabilizes at 3.5-4.0, thus obtaining the composite buffer solution.
[0010] Further, in S2, the weight parts of citric acid, malic acid, purified water, γ-cyclodextrin, glycine, and sodium citrate are respectively 15-30 parts of citric acid, 10-20 parts of malic acid, 800-1000 parts of purified water, 0.3-0.7 parts of γ-cyclodextrin, 0.2-0.5 parts of glycine, and 3-8 parts of sodium citrate.
[0011] Furthermore, the mass ratio of liquid CO2 to complex buffer solution in S2 is 1:1-1.2, the extraction temperature for degeneracy is 35℃-40℃, the extraction pressure is 20MPa-25MPa, and the extraction degeneracy reaction time is 1.5h-2.5h.
[0012] Furthermore, the preparation method of the coffee pericarp flavor extract in S3 is as follows: Coffee husks are washed, dried, and then pulverized. The pulverized coffee husk powder, theaflavins, and ethanol are mixed evenly and extracted by reflux at 65℃-70℃ for 2-4 hours. After reflux extraction, the mixture is filtered, and the filtrate is concentrated at 50℃-60℃ under a vacuum of 0.08MPa-0.09MPa for 3-5 hours to obtain coffee husk flavor extract. The coffee husk powder, theaflavins, and ethanol are in the following weight proportions: 10-20 parts coffee husk powder, 0.1-0.3 parts theaflavins, and 80-120 parts ethanol.
[0013] Furthermore, in step S3, the mass ratio of coffee pericarp flavor extract to purified water is 1:5-7, and the spraying amount of coffee pericarp flavor liquid is 5%-8% of the weight of low-decyn moisture coffee beans. The spraying is carried out by a spray method with a nozzle orifice diameter of 0.5mm, a spray pressure of 0.2MPa-0.3MPa, a mist distance of 15cm-25cm, a coffee bean turning speed of 20rpm-35rpm during spraying, a vacuum drying temperature of 30℃-35℃, a vacuum degree of 0.08MPa-0.09MPa, and a drying time of 3h-5h.
[0014] Furthermore, in S4, the segmented baking adopts a three-stage process: the first stage baking temperature is 140℃-150℃, the baking time is 10min-15min, and the hot air velocity is 1.5m / s; the second stage baking temperature is 170℃-180℃, the baking time is 10min-15min, and the hot air velocity is 1.2m / s; the third stage baking temperature is 200℃-210℃, the baking time is 20min-30min, and the hot air velocity is 1.0m / s.
[0015] Furthermore, in S4, cooling is achieved by introducing clean cold air at a temperature of 20°C-25°C and a wind speed of 2m / s-4m / s, cooling the air to room temperature; the grinding fineness is 800-1500 mesh.
[0016] The beneficial effects of this invention are: This invention achieves a balance between efficient decaffeination and food safety. The method activates coffee beans through low-temperature enzymatic hydrolysis with pectinase, laying the foundation for subsequent decaffeination extraction. Combined with the synergistic effect of liquid CO2 and a complex buffer solution, it can specifically remove caffeine. Furthermore, liquid CO2, as a green extraction agent, avoids the risk of chemical solvent residue, ensuring the safety of the product for consumption. Simultaneously, the decaffeination endpoint is precisely controlled by online monitoring of caffeine concentration during the extraction process, ensuring stable and controllable decaffeination results and meeting the stringent requirements for decaffeinated coffee caffeine content in various scenarios.
[0017] This invention effectively solves the problem of bland flavor in traditional decaffeinated coffee, achieving efficient preservation and enhancement of flavor. During the decaffeination process, coffee pericarp flavor extract can specifically replenish lost volatile aroma substances, while theaflavins help promote the generation of characteristic flavor substances. Combined with a three-stage roasting process, it can slowly stimulate and lock in the original nutty and roasted aromas of coffee, avoiding the destruction of flavor components by high temperatures. Ultimately, this allows decaffeinated coffee to have a rich and harmonious taste and aroma, significantly improving the drinking experience. Detailed Implementation
[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0019] The γ-cyclodextrin used in the following examples was purchased from Zibo Qianhui Biotechnology Co., Ltd.
[0020] The pectinase used in the following examples had an enzyme activity of 30,000 and was purchased from Hebei Jiuyu Biotechnology Co., Ltd.
[0021] Example 1 A method for preparing decaffeinated coffee includes the following preparation steps: S1: Take 100 parts Arabica ungraded coffee beans as coffee beans, wash them 3 times with deionized water and mix them with 200 parts purified water. Then add 0.5 parts of pectinase with an enzyme activity of 30,000 to the mixture and place it in a low-temperature, light-proof environment at 4°C for soaking. Stir once every 3 hours during the soaking process, with the stirring speed controlled at 30 rpm and each stirring lasting 5 minutes. After soaking for 12 hours, remove excess water through conventional filtration to obtain enzymatically activated wet coffee beans.
[0022] S2: First, prepare a compound buffer solution. Take 15 parts of citric acid and 10 parts of malic acid and add them to 800 parts of purified water. Stir at 100 rpm for 10 min to obtain a mixture. Then, add 0.3 parts of γ-cyclodextrin and 0.2 parts of glycine to the mixture in sequence. Continue stirring at 100 rpm for 8 min. Finally, slowly add 3 parts of sodium citrate while stirring at 60 rpm until the pH of the mixture stabilizes at 3.5. The compound buffer solution is now ready. Put the enzymatically activated wet coffee beans obtained in S1 into a supercritical extraction vessel. Introduce liquid CO2 into the vessel and simultaneously inject the prepared compound buffer solution at a mass ratio of liquid CO2 to compound buffer solution of 1:1. Control the temperature in the extraction vessel to 35℃ and the pressure to 20 MPa for extraction and dedecanoation. The extraction and dedecanoation reaction lasts for 1.5 h. Then, gradually reduce the pressure in the extraction vessel to atmospheric pressure and the temperature to room temperature. After recovering CO2, take out the coffee beans to obtain decanoic wet coffee beans.
[0023] S3: First, prepare coffee pericarp flavor extract. Wash and dry fresh coffee pericarps, then pulverize them. Take 10 parts of the pulverized coffee pericarp powder and mix it evenly with 0.1 parts of theaflavins and 80 parts of ethanol. Reflux extraction is performed at 65℃ for 2 hours. After reflux extraction, filter to remove residue. Place the obtained filtrate in a rotary evaporator and concentrate at 50℃ and a vacuum of 0.08 MPa for 3 hours to obtain the coffee pericarp flavor extract. Take the prepared coffee pericarp flavor extract and mix it with purified water at a ratio of 1:5. The coffee cherries were mixed by mass ratio and stirred evenly to obtain a coffee cherry flavor liquid. The flavor liquid was sprayed onto the surface of the decaffeinated coffee beans obtained in S2 at a ratio of 5% of the weight of the decaffeinated coffee beans. The nozzle diameter was 0.5 mm, the spray pressure was 0.2 MPa, and the mist distance was 15 cm. The coffee beans were turned over at 20 rpm during the spraying. After spraying, the coffee beans were transferred to a vacuum drying oven and dried at 30°C and 0.08 MPa for 3 hours to obtain dried decaffeinated coffee beans.
[0024] S4: Transfer the dried decaffeinated coffee beans obtained in S3 into a hot air circulating roaster and use a three-stage roasting process. In the first stage, roast at 140℃ and 1.5m / s hot air velocity for 10 minutes. In the second stage, the temperature is increased to 170℃ and the hot air velocity is maintained at 1.2m / s for 10 minutes. In the third stage, the temperature is increased to 200℃ and the hot air velocity is maintained at 1.0m / s for 20 minutes. After roasting, transfer the coffee beans to a cooling chamber and introduce clean cold air at 20℃ with a cold air velocity of 2m / s. After cooling to room temperature, grind the coffee beans to a fineness of 800 mesh. Then, use a three-layer composite vacuum packaging with an inner layer of polyethylene, a middle layer of aluminum foil, and an outer layer of polyester film. After sealing, sterilize in a 100℃ hot water bath for 5 minutes to obtain decaffeinated coffee.
[0025] Example 2 A method for preparing decaffeinated coffee includes the following preparation steps: S1: Take 110 parts Arabica ungraded coffee beans as coffee beans, wash them 3 times with deionized water and mix them with 230 parts purified water. Then add 1.25 parts pectinase with an enzyme activity of 30,000 to the mixture and place it in a low-temperature, light-proof environment at 5°C for soaking. Stir once every 3.5 hours during the soaking process, with the stirring speed controlled at 40 rpm and each stirring lasting 7.5 minutes. After soaking for 14 hours, remove excess water through conventional filtration to obtain enzymatically activated wet coffee beans.
[0026] S2: First, prepare a compound buffer solution. Take 22.5 parts of citric acid and 15 parts of malic acid and add them to 900 parts of purified water. Stir at 125 rpm for 12.5 min to obtain a mixture. Then, add 0.5 parts of γ-cyclodextrin and 0.35 parts of glycine to the mixture in sequence. Continue stirring at 125 rpm for 10 min. Finally, slowly add 5.5 parts of sodium citrate while stirring at 80 rpm until the pH of the mixture stabilizes at 4.0. The compound buffer solution is now ready. The enzymatically activated wet coffee beans obtained in S1 are loaded into a supercritical extraction vessel. Liquid CO2 is introduced into the vessel, and the prepared compound buffer solution is injected at a mass ratio of liquid CO2 to compound buffer solution of 1:1.1. The temperature inside the extraction vessel is controlled at 37.5℃ and the pressure at 22.5 MPa for extraction and decaking. The extraction and decaking reaction lasts for 2 h. Then, the pressure inside the extraction vessel is gradually reduced to atmospheric pressure and the temperature is reduced to room temperature. After recovering CO2, the coffee beans are taken out to obtain decaffeinated wet coffee beans.
[0027] S3: First, prepare coffee pericarp flavor extract. Wash and dry fresh coffee pericarps, then pulverize them. Take 15 parts of the pulverized coffee pericarp powder and mix it evenly with 0.2 parts of theaflavins and 100 parts of ethanol. Reflux extraction is performed at 67.5℃ for 3 hours. After reflux extraction, filter to remove residue. Place the obtained filtrate in a rotary evaporator and concentrate it at 55℃ and a vacuum of 0.085 MPa for 4 hours to obtain the coffee pericarp flavor extract. Take the prepared coffee pericarp flavor extract and mix it with purified water at a ratio of 1:6. After mixing and stirring evenly, a coffee fruit peel flavor liquid was obtained. The flavor liquid was sprayed onto the surface of the decaffeinated coffee beans obtained in S2 at a ratio of 6.5% of the weight of the decaffeinated coffee beans. During spraying, the nozzle diameter was 0.5 mm, the spray pressure was 0.25 MPa, and the mist distance was 20 cm. The coffee beans were turned over at 27.5 rpm during spraying. After spraying, the coffee beans were transferred to a vacuum drying oven and dried at 32.5℃ and 0.085 MPa for 4 hours. The dried decaffeinated coffee beans were then obtained.
[0028] S4: Transfer the dried decaffeinated coffee beans obtained in S3 into a hot air circulating roaster and use a three-stage roasting process. In the first stage, roast at 145℃ and 1.5m / s hot air velocity for 12 minutes. In the second stage, the temperature is increased to 175℃ and the hot air velocity is maintained at 1.2m / s for 12 minutes. In the third stage, the temperature is increased to 205℃ and the hot air velocity is maintained at 1.0m / s for 25 minutes. After roasting, transfer the coffee beans to a cooling chamber and introduce clean cold air at 22.5℃ with a cold air velocity of 3m / s. After cooling to room temperature, grind the coffee beans to a fineness of 1150 mesh. Then, use a three-layer composite vacuum packaging with an inner layer of polyethylene, a middle layer of aluminum foil, and an outer layer of polyester film. After sealing, sterilize in a 100℃ hot water bath for 5 minutes to obtain decaffeinated coffee.
[0029] Example 3 A method for preparing decaffeinated coffee includes the following preparation steps: S1: Take 120 parts Arabica whole-grade coffee beans as coffee beans, wash them 3 times with deionized water and mix them with 260 parts purified water. Then add 2 parts pectinase with an enzyme activity of 30,000 to the mixture and place it in a low-temperature, light-proof environment at 6°C for soaking. Stir once every 4 hours during the soaking process, with the stirring speed controlled at 50 rpm and each stirring lasting 10 minutes. After soaking for 16 hours, remove excess water through conventional filtration to obtain enzymatically activated wet coffee beans.
[0030] S2: First, prepare a compound buffer solution. Take 30 parts of citric acid and 20 parts of malic acid and add them to 1000 parts of purified water. Stir at 150 rpm for 15 min to obtain a mixture. Then, add 0.7 parts of γ-cyclodextrin and 0.5 parts of glycine to the mixture in sequence. Continue stirring at 150 rpm for 12 min. Finally, slowly add 8 parts of sodium citrate while stirring at 100 rpm until the pH of the mixture stabilizes at 4.0. The compound buffer solution is now ready. The enzymatically activated wet coffee beans obtained in S1 are loaded into a supercritical extraction vessel. Liquid CO2 is introduced into the vessel, and the prepared compound buffer solution is injected at a mass ratio of liquid CO2 to compound buffer solution of 1:1.2. The temperature inside the extraction vessel is controlled at 40℃ and the pressure at 25 MPa for extraction and dedecyning. The extraction and dedecyning reaction lasts for 2.5 h. Then, the pressure inside the extraction vessel is gradually reduced to atmospheric pressure and the temperature is reduced to room temperature. After recovering CO2, the coffee beans are taken out to obtain decyned wet coffee beans.
[0031] S3: First, prepare coffee pericarp flavor extract. Wash and dry fresh coffee pericarps, then pulverize them. Take 20 parts of the pulverized coffee pericarp powder and mix it evenly with 0.3 parts of theaflavins and 120 parts of ethanol. Reflux extraction is performed at 70℃ for 4 hours. After reflux extraction, filter to remove residue. Place the obtained filtrate in a rotary evaporator and concentrate at 60℃ and a vacuum of 0.09 MPa for 5 hours to obtain the coffee pericarp flavor extract. Take the prepared coffee pericarp flavor extract and mix it with purified water at a ratio of 1:7. The coffee cherries were mixed by mass ratio and stirred evenly to obtain a coffee cherry flavor liquid. The flavor liquid was sprayed onto the surface of the decaffeinated coffee beans obtained in S2 at a ratio of 8% of the weight of the decaffeinated coffee beans. The nozzle diameter was 0.5 mm, the spray pressure was 0.3 MPa, and the mist distance was 25 cm. The coffee beans were turned over at 35 rpm during the spraying. After spraying, the coffee beans were transferred to a vacuum drying oven and dried at 35℃ and 0.09 MPa for 5 hours to obtain dried decaffeinated coffee beans.
[0032] S4: Transfer the dried decaffeinated coffee beans obtained in S3 to a hot air circulating roaster and use a three-stage roasting process. In the first stage, roast at 150℃ and 1.5m / s hot air velocity for 15 minutes. In the second stage, the temperature is increased to 180℃ and the hot air velocity is maintained at 1.2m / s for 15 minutes. In the third stage, the temperature is increased to 210℃ and the hot air velocity is maintained at 1.0m / s for 30 minutes. After roasting, transfer the coffee beans to a cooling chamber and introduce clean cold air at 25℃ with a cold air velocity of 4m / s. After cooling to room temperature, grind the coffee beans to a fineness of 1500 mesh. Then, use a three-layer composite vacuum packaging with an inner layer of polyethylene, a middle layer of aluminum foil, and an outer layer of polyester film. After sealing, sterilize in a 100℃ hot water bath for 5 minutes to obtain decaffeinated coffee.
[0033] Comparative Example 1 Compared with Example 1, this comparative example replaces the "complex buffer" with an equal mass of "liquid CO2". All other steps and parameters are the same, and will not be repeated here. The final result is decaffeinated coffee.
[0034] Comparative Example 2 Compared with Example 1, this comparative example replaces "liquid CO2" with an equal mass of "complex buffer solution". All other steps and parameters are the same, and will not be repeated here. The final result is decaffeinated coffee.
[0035] Comparative Example 3 Compared with Example 1, this comparative example does not add γ-cyclodextrin or glycine, but all other steps and parameters are the same. This comparative example will not be repeated here. Finally, decaffeinated coffee is obtained.
[0036] Comparative Example 4 Compared with Example 1, this comparative example replaces "glycine" with an equal mass of "γ-cyclodextrin". All other steps and parameters are the same, and will not be repeated here. The final result is decaffeinated coffee.
[0037] Comparative Example 5 Compared with Example 1, this comparative example replaces "15 parts citric acid + 10 parts malic acid" in the compound buffer solution with "25 parts citric acid" of equal mass. All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, decaffeinated coffee is obtained.
[0038] Comparative Example 6 Compared with Example 1, this comparative example replaces "theaflavins" with an equal mass of "ethanol". All other steps and parameters are the same, and will not be repeated here. The final result is decaffeinated coffee.
[0039] Comparative Example 7 Compared with Example 1, this comparative example replaces the "three-stage roasting" in the compound buffer solution with "one-stage roasting" (roasting at 170°C and a hot air velocity of 1.2 m / s for 40 min). All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, decaffeinated coffee is obtained.
[0040] The decaffeinated coffee prepared in Examples 1-3 and Comparative Examples 1-7 were tested, and the results are recorded in Table 1.
[0041] Caffeine concentration detection method: Take decaffeinated coffee (ground and brewed with 80℃ purified water at a ratio of 1:10, filtered, and collect the supernatant). Dilute 10 times with mobile phase A (water:trifluoroacetic acid = 1000:0.5), filter through a 0.45μm cellulose acetate membrane, and inject into HPLC. The chromatographic column was TSK-gel ODS-80TsQA (4.6mm × 150mm), the column temperature was 40℃, the flow rate was 1.0mL / min, and the detection wavelength was 280nm. The caffeine concentration (unit: mg / 100g) was quantified using a standard curve.
[0042] Acetic acid concentration detection method: Take the above-mentioned supernatant and mix it with 0.5% perchloric acid at a ratio of 1:1. Dilute it 5 times with deion-exchanged water, filter it through a 0.45 μm membrane, and inject it into HPLC. The chromatographic column is Shim-pack SCR-102H (8 mm × 300 mm), the mobile phase is 5 mmol / L p-toluenesulfonic acid aqueous solution, the reaction solution contains 20 mmol / L Bis-Tris and 0.1 mmol / L EDTA, the column temperature is 45℃, the flow rate is 0.8 mL / min, and the acetic acid concentration (unit: mg / 100 g) is quantified using a conductivity detector.
[0043] Determination of characteristic flavor compound (2,3,5-trimethylpyrazine): 5g of finished coffee powder was extracted with anhydrous ethanol using ultrasonic extraction for 30min (300W). The supernatant was centrifuged, filtered through a 0.22μm membrane, and injected into a GC-MS. The chromatographic column was a DB-5MS (30m × 0.25mm × 0.25μm). The temperature program was: 40℃ for 3min, then increased to 200℃ at 5℃ / min and held for 5min. The injection port temperature was 250℃, the ion source temperature was 230℃, and the ion monitoring mode (m / z 108) was selected. Quantification was performed using the external standard method (unit: μg / kg). This compound is a key component of the nutty flavor of coffee.
[0044] Sensory evaluation: Blind tasting was conducted by 10 trained professional judges (with over 5 years of experience and familiarity with decaffeinated coffee flavors). Scoring dimensions included body (0-10 points), bitterness (0-10 points), and aroma (0-10 points), with the average score used as the overall score (rounded to one decimal place). Scoring criteria: 9-10 points (rich and harmonious flavor, no off-flavors), 7-8.9 points (relatively harmonious flavor, minor defects), 5-6.9 points (bland flavor, obvious defects), <5 points (deteriorated flavor, off-flavors).
[0045] Table 1: Detection results of decaffeinated coffee According to the data in Table 1, the decaffeinated coffee prepared in Examples 1-3 has excellent overall performance, which stems from the synergistic optimization of each core process step: from the low-temperature enzymatic hydrolysis and activation of coffee beans by pectinase to improve the subsequent extraction efficiency, to the synergistic effect of liquid CO2 and compound buffer to achieve efficient decaffeination, to the coffee peel flavor liquid to replenish the flavor substances lost during the decaffeination process, and finally to the three-stage roasting to lock in the characteristic aroma. Each step is designed around "efficient decaffeination" and "flavor retention", ultimately achieving a balance between decaffeination effect and sensory quality.
[0046] Comparing Comparative Example 1 with Example 1, it can be seen that this comparative example uses liquid CO2 instead of the composite buffer solution. This comparative example was set up to verify the extraction optimization effect of the composite buffer solution. The composite buffer solution can stabilize the pH of the extraction system within a suitable range of 3.5-4.0. Simultaneously, through the synergistic effect of citric acid, malic acid, and γ-cyclodextrin, it improves the selective extraction efficiency of caffeine by liquid CO2 and protects the organic acids in coffee from damage. When using only liquid CO2, the pH of the extraction system is difficult to control, easily leading to a decrease in decaffeination efficiency or loss of flavor components. This comparison highlights the optimization value of the composite buffer solution for the extraction system and explains why it is a core component of the decaffeination process.
[0047] Comparing Comparative Example 2 with Example 1, it can be seen that this comparative example replaced liquid CO2 with an equal mass of composite buffer solution, relying solely on the composite buffer solution for decaffeination, lacking the selective extraction effect of liquid CO2. Liquid CO2 is the core medium for caffeine removal; without its participation, the composite buffer solution can only slightly adjust the system environment and cannot efficiently separate caffeine. Therefore, the caffeine concentration is significantly higher than in all examples and Comparative Example 1. At the same time, the single buffer solution system is difficult to stabilize organic acids; the acetic acid concentration is slightly higher than in Comparative Example 1 but lower than in Example 1. Flavor substances are largely lost due to the disordered decaffeination process, resulting in a significant decrease in sensory scores, highlighting the irreplaceable role of liquid CO2 in the decaffeination process.
[0048] Comparing Comparative Example 3 with Example 1, it can be seen that without the addition of γ-cyclodextrin and glycine, the complex buffer lost its key functional components. γ-cyclodextrin can encapsulate caffeine and protect flavor compounds, while glycine can stabilize the pH of the system. With both absent, the pH regulation ability of the complex buffer decreased, and the selective removal efficiency of caffeine decreased. Therefore, the caffeine concentration was higher than in Example 1 but lower than the previous two comparative examples. The acetic acid concentration decreased slightly due to insufficient system stability, resulting in reduced retention of flavor compounds and a lower sensory score than in Example 1. This clearly demonstrates the synergistic enhancing effect of γ-cyclodextrin and glycine on the buffer's function.
[0049] Comparing Comparative Example 4 with Example 1, it can be seen that although glycine was replaced with an equal mass of γ-cyclodextrin in this comparative example, the system stabilizing effect of glycine was lacking, despite the increased amount of γ-cyclodextrin. Excessive γ-cyclodextrin could not compensate for glycine's precise pH control, resulting in a slight decrease in decaffeination efficiency. The caffeine concentration was higher than in Example 1 but lower than in Comparative Example 3. The acetic acid concentration was slightly higher than in Comparative Example 3 due to smaller system fluctuations. The retention of flavor compounds was better than the previous three comparative examples, and the sensory score was relatively higher. This indicates that the stabilizing effect of glycine cannot be replaced by simply increasing the amount of γ-cyclodextrin; the ratio of the two needs to be precisely controlled.
[0050] Comparing Comparative Example 5 with Example 1, it can be seen that this comparative example replaces the "citric acid + malic acid" in the composite buffer solution with citric acid alone. The intention behind this is to verify the synergistic advantages of the mixed acids. The mixed system of citric acid and malic acid can precisely regulate the pH through synergistic effects, while simultaneously imparting a mild acidic base to the extraction system, avoiding pH fluctuations or overly acidic flavor issues caused by a single acid. The comparison demonstrates the importance of the mixed acid combination for system stability and flavor balance, indicating that the formulation design of the composite buffer solution is not a simple additive process, but rather an optimization result based on the synergistic effects of the components.
[0051] Comparing Comparative Example 6 with Example 1, it can be seen that theaflavin was replaced with ethanol in this comparative example. The comparison highlights the effect of theaflavin on enhancing the flavor richness of decaffeinated coffee, indicating that it is an important raw material to compensate for the bland flavor after decaffeination, thus proving the necessity of adding this raw material.
[0052] Comparing Comparative Example 7 with Example 1, it can be seen that this comparative example uses a single-stage high-temperature roasting process instead of a three-stage roasting process. This comparative example was set up to verify the impact of the roasting process on flavor preservation. The three-stage roasting process, through gradual temperature increases, can slowly activate the characteristic aroma compounds in coffee and reduce the loss of volatile components, while high-temperature roasting quickly destroys flavor precursors, leading to aroma deterioration. The comparison highlights the crucial role of low-temperature, segmented roasting in locking in characteristic flavors and preventing flavor deterioration, demonstrating that this process is an important step in ensuring the sensory quality of decaffeinated coffee, rather than a simple heating and drying process.
[0053] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.
Claims
1. A method for preparing decaffeinated coffee, characterized in that, The preparation steps include the following: S1: After washing the coffee beans, mix them with purified water and add pectinase. Let them soak in the cool, dark place, stirring regularly during the process. After soaking, filter to remove excess water to obtain enzymatically activated wet coffee beans. S2: The enzymatically activated wet coffee beans are loaded into the extraction vessel, liquid CO2 is introduced and a compound buffer solution is injected, and the extraction and dedecenoting are carried out under controlled conditions. After the extraction and dedecenoting are completed, the pressure and temperature are reduced and the CO2 is recovered. The coffee beans are then removed to obtain decenoated wet coffee beans. S3: Add coffee pericarp flavor extract to purified water and stir evenly to obtain coffee pericarp flavor liquid. Spray the coffee pericarp flavor liquid onto the surface of decaffeinated coffee beans and then vacuum dry to obtain dried decaffeinated coffee beans. S4: The dried decaffeinated coffee beans are roasted in stages, cooled, ground, and finally packaged and sterilized to obtain decaffeinated coffee.
2. The method for preparing decaffeinated coffee according to claim 1, characterized in that, In S1, the weight parts of coffee beans, water, and pectinase are 100-120 parts coffee beans, 200-260 parts water, and 0.5-2 parts pectinase, respectively.
3. The method for preparing decaffeinated coffee according to claim 1, characterized in that, The low-temperature immersion temperature in S1 is 4℃-6℃; the light-protected standing time is 12h-16h; the interval for regular stirring is once every 3h-4h, the stirring speed is 30rpm-50rpm, and the duration of each stirring is 5min-10min.
4. The method for preparing decaffeinated coffee according to claim 1, characterized in that, The preparation steps of the composite buffer solution in S2 are as follows: citric acid and malic acid are added to purified water and stirred for 10-15 minutes at a stirring speed of 100-150 rpm to obtain a mixture; then γ-cyclodextrin and glycine are added to the mixture in sequence and stirred for another 8-12 minutes at a stirring speed of 100-150 rpm; finally, sodium citrate is slowly added while stirring at a speed of 60-100 rpm until the pH of the mixture stabilizes at 3.5-4.0, thus obtaining the composite buffer solution.
5. The method for preparing decaffeinated coffee according to claim 4, characterized in that, The weight parts of citric acid, malic acid, purified water, γ-cyclodextrin, glycine, and sodium citrate in S2 are 15-30 parts of citric acid, 10-20 parts of malic acid, 800-1000 parts of purified water, 0.3-0.7 parts of γ-cyclodextrin, 0.2-0.5 parts of glycine, and 3-8 parts of sodium citrate, respectively.
6. The method for preparing decaffeinated coffee according to claim 1, characterized in that, The mass ratio of liquid CO2 to complex buffer solution in S2 is 1:1-1.
2. The extraction temperature for degeneracy is 35℃-40℃, the extraction pressure is 20MPa-25MPa, and the extraction reaction time is 1.5h-2.5h.
7. The method for preparing decaffeinated coffee according to claim 1, characterized in that, The preparation method of the coffee pericarp flavor extract in S3 is as follows: Coffee husks are washed, dried, and then pulverized. The pulverized coffee husk powder, theaflavins, and ethanol are mixed evenly and extracted by reflux at 65℃-70℃ for 2-4 hours. After reflux extraction, the mixture is filtered, and the filtrate is concentrated at 50℃-60℃ under a vacuum of 0.08MPa-0.09MPa for 3-5 hours to obtain coffee husk flavor extract. The coffee husk powder, theaflavins, and ethanol are in the following weight proportions: 10-20 parts coffee husk powder, 0.1-0.3 parts theaflavins, and 80-120 parts ethanol.
8. The method for preparing decaffeinated coffee according to claim 1, characterized in that, In step S3, the mass ratio of coffee pericarp flavor extract to purified water is 1:5-7, and the spraying amount of coffee pericarp flavor liquid is 5%-8% of the weight of low-decyn moisture coffee beans. Spraying is carried out by a spray method with a nozzle orifice diameter of 0.5mm, a spray pressure of 0.2MPa-0.3MPa, a mist distance of 15cm-25cm, a coffee bean turning speed of 20rpm-35rpm during spraying, a vacuum drying temperature of 30℃-35℃, a vacuum degree of 0.08MPa-0.09MPa, and a drying time of 3h-5h.
9. A method for preparing decaffeinated coffee according to claim 1, characterized in that, In S4, the segmented baking adopts a three-stage process. The first stage baking temperature is 140℃-150℃, the baking time is 10min-15min, and the hot air velocity is 1.5m / s; the second stage baking temperature is 170℃-180℃, the baking time is 10min-15min, and the hot air velocity is 1.2m / s; the third stage baking temperature is 200℃-210℃, the baking time is 20min-30min, and the hot air velocity is 1.0m / s.
10. A method for preparing decaffeinated coffee according to claim 1, characterized in that, In S4, cooling is achieved by introducing clean cold air at a temperature of 20℃-25℃ and a wind speed of 2m / s-4m / s, cooling the air to room temperature; the grinding fineness is 800-1500 mesh.