A method for integrated micro-water peeling and degumming of fresh coffee cherries

Abstract

This invention discloses an integrated micro-aqueous degumming and peeling method for fresh coffee cherries, belonging to the field of fresh coffee cherry processing technology. The method includes: micro-aqueous degumming of fresh cherries using a pretreatment solution containing sodium citrate and sodium chloride; biological degumming using a specialized composite degumming enzyme composed of pectinase, cellulase, and calcium chloride; adding chitosan to the wastewater after rinsing for composite coagulation, followed by solid-liquid separation to obtain recycled water; and finally drying to obtain coffee beans in their shells. This invention utilizes sodium citrate to chelate calcium bridges to degrade the pectin cross-linking structure and sodium chloride to compress the double electric layer and reduce slurry viscosity, achieving efficient mass transfer and rapid degumming under micro-aqueous conditions. Furthermore, it utilizes residual salts to achieve pH anchoring and ionic strength regulation, promoting the formation of a dense aggregated phase between pectin degradation products and chitosan, solving the industry problems of difficult micro-aqueous system treatment and unstable recycled water reuse. This invention reduces water consumption by more than 90% compared to traditional washing methods, achieves thorough degumming, preserves the complete flavor of coffee beans, has low equipment costs, and enables sustainable closed-loop production, making it suitable for industrial application in small-scale coffee processing plants.

Description

Technical Field

[0001] This invention relates to the field of coffee fruit processing technology, specifically to an integrated method for micro-water peeling and degumming of coffee fruit. Background Technology

[0002] The peeling and degumming process in fresh coffee cherry processing separates the rind from the fruit and degrades the pectin layer on the surface of the beans. Traditional wet processing consumes a lot of water and produces high-concentration organic wastewater, posing a significant environmental challenge. While waterless mechanical processing saves water, it requires extremely high precision in equipment and a high degree of ripeness in the fresh coffee cherries. Mechanical friction can easily damage the beans and generate localized high temperatures, destroying the cell structure of the coffee beans and reducing the quality of the green beans and their flavor during cupping.

[0003] Micro-water processing combined with bio-enzymatic degumming has become a technological direction that balances water conservation and quality, but existing technologies have obvious drawbacks: 1. In a micro-aqueous environment, the pectin concentration is high, and the pectin forms a dense three-dimensional network with calcium ions. This results in high slurry viscosity, hindered enzyme mass transfer, incomplete degumming, and a long degumming time.

[0004] 2. There is a general technical bias in the industry, which believes that adding inorganic salts to micro-water systems will inhibit enzyme activity and damage the water treatment system, so the use of salt additives is avoided.

[0005] 3. Pectin fragments accumulate in circulating water, and conventional flocculation easily forms loose hydrogels with extremely high water retention and difficulty in centrifugation separation, leading to rapid deterioration of circulating water and making it impossible to achieve stable closed-loop reuse.

[0006] Currently, the industry lacks an integrated processing solution that can simultaneously achieve water conservation, thorough degumming, stable water circulation, low equipment cost, and good flavor preservation. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing technologies and provide an integrated processing method for peeling and degumming fresh coffee cherries using micro-water technology. This method solves problems such as high viscosity of micro-water systems, poor enzyme mass transfer, difficulty in water treatment, and insufficient circulation stability, while reducing equipment requirements and preserving coffee flavor.

[0008] This invention is achieved through the following technical solution: 1. Special compound degumming enzyme A compound degumming enzyme specifically for micro-hydronic peeling and degumming of fresh coffee cherries, comprising, by weight: 70-90 parts of pectinase dry powder; 5-25 parts of cellulase dry powder; 5 parts of calcium chloride powder.

[0009] The pectinase dry powder has an enzyme activity ≥50000U / g and a moisture content <8% by mass; the cellulase dry powder has an enzyme activity ≥10000U / g and a moisture content <8% by mass.

[0010] Calcium chloride provides Ca 2+ It is used to pre-activate the active center of pectinase, thereby improving catalytic efficiency and stability.

[0011] The preparation method of the special composite degumming enzyme is as follows: put pectinase dry powder, cellulase dry powder and calcium chloride powder into a three-dimensional mixer, mix them in a closed environment with a temperature of 20-25℃ and a relative humidity of <40% for 30-40 minutes at 30-40 rpm, and then discharge the product.

[0012] 2. Integrated processing method A method for integrated micro-moisture peeling and degumming of fresh coffee cherries includes the following steps: S1, Micro-water degumming The selected fresh coffee cherries are fed into a micro-water peeling machine, and a pretreatment solution consisting of water, sodium citrate, and sodium chloride is added for peeling to separate the coffee cherries skin and the coffee beans with husks containing mucilage. S2, Bio-enzymatic degumming Coffee beans in their shells are fed into a degumming tank, a special compound degumming enzyme is added, and the mixture is stirred at 30-50℃ to carry out biological degumming. S3, Rinse and Separate After degumming, rinse the coffee beans in their shells with clean water to separate the detached gum from the wastewater. S4. Wastewater coagulation and recycling Wastewater is collected and chitosan is added for a complex coagulation reaction. Sodium citrate remaining in the pretreatment liquid is used as a pH buffer system and sodium chloride is used as an ionic strength regulator. After solid-liquid separation, recycled water is obtained and reused in step S1. S5, Drying Dry the rinsed coffee beans in their husks until the moisture content is 10-11%.

[0013] Key Mechanism Explanation 1. Micro-water viscosity reduction mechanism Sodium citrate chelates calcium ions in the cross-linked structure of pectin, dissociating the calcium bridges; sodium chloride increases ionic strength and reduces the absolute value of the zeta potential. The synergistic effect of these two substances significantly reduces the viscosity of the slurry, achieving highly efficient degumming under micro-water conditions.

[0014] 2. Compound coagulation water purification mechanism Sodium citrate locks the pH of the system at 4.5-5.0, making the pectin degradation products positively charged and causing efficient electrostatic complexation; sodium chloride provides moderate electrostatic shielding, promoting the dehydration and shrinkage of the complex to form a dense condensed phase with high density and low water holding capacity, which can be separated by conventional centrifugation to achieve stable water recycling.

[0015] This invention overcomes the long-standing technical bias in the field of avoiding the addition of inorganic salts in micro-aqueous systems, and realizes the dual functions of the same reagent in front-end viscosity reduction and back-end water purification, forming a closed loop of the whole process. Water consumption is reduced by more than 90% compared with traditional water washing, degumming is thorough, flavor is well preserved, and it is suitable for industrial application in small and medium-sized processing plants. Attached Figure Description

[0016] Figure 1 This is a step diagram of the present invention. Detailed Implementation

[0017] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. 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.

[0018] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher quality products. The integrated processing method for micro-water degumming and peeling of fresh coffee cherries described in this invention can be adapted to different varieties of coffee raw materials by adjusting the process parameters. For medium-sized coffee cherries with a thicker pectin layer, the amount of the special compound degumming enzyme added in step S2 is adjusted to 0.06-0.08% of the weight of the coffee beans in their shells, and the degumming reaction time is extended to 55-60 minutes. For small-sized coffee cherries with a thinner pectin layer, the amount of the special compound degumming enzyme added is reduced to 0.02-0.04%, and the degumming reaction time is shortened to 40-45 minutes.

[0019] Mature coffee cherries are purplish-red or bright red in appearance, plump, free from mold and obvious mechanical damage. Pectinase, solid powder, with an enzyme activity of 50,000 U / g and a moisture content of less than 8% by mass; Cellulase, in solid powder form, with an enzyme activity of 10,000 U / g and a moisture content of less than 8% by mass. Anhydrous calcium chloride, white powder, with a purity greater than or equal to 96.0%.

[0020] Preparation Example 1 This preparation example provides a method for preparing a specific composite degumming enzyme, including the following steps: 80 parts by weight of pectinase dry powder, 15 parts by weight of cellulase dry powder and 5 parts by weight of calcium chloride powder were put into a three-dimensional mixer and mixed and stirred at 30 rpm for 40 minutes in a closed environment with a temperature of 25℃ and a relative humidity of 20%-40%. After discharge, a special composite degumming enzyme C1 was obtained.

[0021] Preparation Example 2 This preparation example provides a method for preparing a specific composite degumming enzyme, including the following steps: 70 parts by weight of pectinase dry powder, 25 parts by weight of cellulase dry powder and 5 parts by weight of calcium chloride powder were put into a three-dimensional mixer and mixed and stirred at 30 revolutions per minute for 40 minutes in a closed environment with a temperature of 25°C and a relative humidity of 20%-40%. After discharge, a special composite degumming enzyme C2 was obtained.

[0022] Preparation Example 3 This preparation example provides a method for preparing a specific composite degumming enzyme, including the following steps: 90 parts by weight of pectinase dry powder, 5 parts by weight of cellulase dry powder and 5 parts by weight of calcium chloride powder were put into a three-dimensional mixer and mixed and stirred at 30 revolutions per minute for 40 minutes in a closed environment with a temperature of 25°C and a relative humidity of 20%-40%. After discharge, a special composite degumming enzyme C3 was obtained.

[0023] Preparation Example 4 This preparation example provides a method for preparing a specific composite degumming enzyme, including the following steps: 80 parts by weight of pectinase dry powder, 15 parts by weight of cellulase dry powder and 5 parts by weight of calcium chloride powder were put into a three-dimensional mixer and mixed and stirred at a speed of 40 revolutions per minute for 30 minutes in a closed environment with a temperature of 20°C and a relative humidity of 20%-40%. After discharge, a special composite degumming enzyme C4 was obtained.

[0024] Example 1 This embodiment provides an integrated method for micro-hydration peeling and degumming of fresh coffee cherries, including the following steps: 1000 kg of ripe coffee cherries were water-sorted to remove impurities. The sorted coffee cherries were then fed into a micro-water peeling machine, where a solution of water, sodium citrate, and sodium chloride was added. The sodium citrate concentration was 0.5% and the sodium chloride concentration was 2.5%. Water was added at a ratio of 1:50 (water to coffee cherries by weight) to remove the cherries, separating the coffee cherries skin and the coffee beans with their husks coated with gum. The coffee beans were then directly fed into a degumming tank equipped with temperature control and stirring devices. A special compound degumming enzyme C1, at a weight equivalent to 0.05% of the coffee beans, was added to adjust the temperature of the tank. The internal temperature is raised to 40℃, and the mixture is stirred at 15 revolutions per minute for 60 minutes for biological degumming. After degumming, water is added to the coffee beans in a ratio of 1:20 (water to coffee beans by weight) for rapid rinsing to separate the detached gum and wastewater. The rinsing wastewater is collected and chitosan (0.1% by weight of wastewater) is added for a complex coagulation reaction. The resulting recycled water is centrifuged and reused for the next batch of pretreatment. Finally, the washed coffee beans are placed in a hot air circulating dryer and dried at 50℃ until the moisture content is 11%, yielding the processed coffee beans.

[0025] Example 2 This embodiment provides an integrated method for micro-hydration peeling and degumming of fresh coffee cherries, including the following steps: 1000 kg of ripe coffee cherries were water-sorted to remove impurities. The sorted coffee cherries were then fed into a micro-water desiccant, where a solution of water, sodium citrate, and sodium chloride was added. The sodium citrate concentration was 0.5% and the sodium chloride concentration was 2.5%. Water was added at a ratio of 1:50 (water to coffee cherries by weight) to separate the coffee cherries and the coffee beans with their outer shells and attached gum. The coffee beans were then directly fed into a degumming tank equipped with temperature control and stirring devices. A special compound degumming enzyme C1, at a weight equivalent to 0.02% of the coffee beans, was added to adjust the temperature of the tank. The internal temperature is raised to 30℃, and the mixture is stirred at 15 revolutions per minute for 60 minutes for biological degumming. After degumming, water is added to the coffee beans in a ratio of 1:20 (water to coffee beans by weight) for rapid rinsing to separate the detached gum and wastewater. The rinsing wastewater is collected and chitosan (0.1% by weight of wastewater) is added for a complex coagulation reaction. The resulting recycled water is centrifuged and reused for the next batch of pretreatment. Finally, the washed coffee beans are placed in a hot air circulating dryer and dried at 50℃ until the moisture content is 11%, yielding the processed coffee beans.

[0026] Example 3 This embodiment provides an integrated method for micro-hydration peeling and degumming of fresh coffee cherries, including the following steps: 1000 kg of ripe coffee cherries were water-sorted to remove impurities. The sorted coffee cherries were then fed into a micro-water peeling machine, where a solution of water, sodium citrate, and sodium chloride was added. The sodium citrate concentration was 0.5% and the sodium chloride concentration was 2.5%. Water was added at a ratio of 1:50 (water to coffee cherries by mass) to remove the cherries, separating the coffee cherries skin and the coffee beans with their husks coated with gum. The coffee beans were then directly fed into a degumming tank equipped with temperature control and stirring devices, and an amount equivalent to... The coffee beans were treated with 0.08% of a special compound degumming enzyme C1. The temperature inside the container was adjusted to 50°C, and the mixture was stirred at 15 rpm for 60 minutes for biological degumming. After degumming, the coffee beans were quickly rinsed with water at a ratio of 1:20 (water to coffee beans by weight) to separate the detached gum and wastewater. Finally, the washed coffee beans were placed in a hot air circulating dryer and dried at 50°C until the moisture content was 11%, resulting in processed coffee beans.

[0027] Example 4 This embodiment provides an integrated method for micro-hydration peeling and degumming of fresh coffee cherries, including the following steps: 1000 kg of ripe coffee cherries were water-sorted to remove impurities. The sorted coffee cherries were then fed into a micro-water peeling machine, where a solution of water, sodium citrate, and sodium chloride was added. The sodium citrate concentration was 0.5% and the sodium chloride concentration was 2.5%. Water was added at a ratio of 1:50 (water to coffee cherries by weight) to remove the cherries, separating the coffee cherries skin and the coffee beans with their husks coated with gum. The coffee beans were then directly fed into a degumming tank equipped with temperature control and stirring devices. A special compound degumming enzyme C2, equivalent to 0.05% of the weight of the coffee beans, was added to adjust the temperature of the tank. The internal temperature is raised to 40℃, and the mixture is stirred at 15 revolutions per minute for 60 minutes for biological degumming. After degumming, water is added to the coffee beans in a ratio of 1:20 (water to coffee beans by weight) for rapid rinsing to separate the detached gum and wastewater. The rinsing wastewater is collected and chitosan (0.1% by weight of wastewater) is added for a complex coagulation reaction. The resulting recycled water is centrifuged and reused for the next batch of pretreatment. Finally, the washed coffee beans are placed in a hot air circulating dryer and dried at 50℃ until the moisture content is 11%, yielding the processed coffee beans.

[0028] Example 5 This embodiment provides an integrated method for micro-hydration peeling and degumming of fresh coffee cherries, including the following steps: 1000 kg of ripe coffee cherries were water-sorted to remove impurities. The sorted coffee cherries were then fed into a micro-water desiccant, where a pretreatment solution consisting of water, sodium citrate, and sodium chloride was added. The sodium citrate concentration in the pretreatment solution was 0.5%, and the sodium chloride concentration was 2.5%. Water was added at a water-to-coffee-cherry mass ratio of 1:50 to perform the desiccant process, separating the coffee cherries skin and the coffee beans with the gum coating on their surface. The coffee beans with the gum coating were then directly fed into a degumming tank equipped with a temperature control and stirring device, and 0.05% of a special compound degumming enzyme C3 was added. The temperature inside the tank was adjusted to 40°C, and the mixture was stirred at 15 revolutions per minute for 60 minutes for biological degumming. After degumming, water was added to the coffee beans in a ratio of 1:20 (water to coffee beans by weight) for quick rinsing to separate the detached gum and wastewater. The rinsing wastewater was collected and chitosan (0.1% by weight of wastewater) was added for a complex coagulation reaction. The resulting recycled water was centrifuged and reused for the next batch of pretreatment. Finally, the washed coffee beans were placed in a hot air circulating dryer and dried at 50°C until the moisture content was 11%, yielding the processed coffee beans.

[0029] Example 6 This embodiment provides an integrated method for micro-hydration peeling and degumming of fresh coffee cherries, including the following steps: 1000 kg of ripe coffee cherries were water-sorted to remove impurities. The sorted coffee cherries were then fed into a micro-water desiccant, where a pretreatment solution consisting of water, sodium citrate, and sodium chloride was added. The sodium citrate concentration in the pretreatment solution was 0.5%, and the sodium chloride concentration was 2.5%. Water was added at a water-to-coffee-cherry mass ratio of 1:80 to perform the desiccant process, separating the coffee cherries skin and the coffee beans with the gum coating on their surface. The coffee beans with the gum coating were then directly fed into a degumming tank equipped with a temperature control and stirring device, and 0.05% of a special compound degumming enzyme C4 was added. The temperature inside the tank was adjusted to 45°C, and the mixture was stirred at 15 revolutions per minute for 45 minutes for biological degumming. After degumming, water was added to the coffee beans in a ratio of 1:15 (water to coffee beans by weight) for quick rinsing to separate the detached gum and wastewater. The rinsing wastewater was collected and chitosan (0.1% by weight of wastewater) was added for a complex coagulation reaction. The resulting recycled water was centrifuged and reused for the next batch of pretreatment. Finally, the washed coffee beans were placed in a hot air circulating dryer and dried at 55°C until the moisture content was 10%, yielding the processed coffee beans.

[0030] Example 7 A simplified method for degumming and peeling fresh coffee cherries using a micro-water process is provided, suitable for small-scale processing plants without closed-loop water treatment requirements. The method includes the following steps: The selected fresh coffee cherries are fed into a micro-water peeling machine, where a pretreatment solution is added for peeling, separating the coffee beans into whole-shell beans. The whole-shell beans are then fed into a degumming tank, where a special compound degumming enzyme is added, and the mixture is stirred at 30-50°C for biological degumming. After degumming, the beans are rinsed with clean water to separate the detached gum and wastewater. The wastewater is neutralized in a primary sedimentation tank and then discharged directly after meeting the standards. The washed whole-shell beans are then dried with hot air.

[0031] Comparative Example 1 Compared with Example 1, the difference is that sodium citrate was not added in the pretreatment step, but all other steps are the same.

[0032] Comparative Example 2 Compared with Example 1, the difference is that sodium chloride was not added in the pretreatment step, but all other steps are the same.

[0033] Comparative Example 3 Compared with Example 1, the difference is that sodium citrate in the pretreatment step is replaced with disodium ethylenediaminetetraacetate in equal molar amounts; all other steps are the same.

[0034] Comparative Example 4 Compared with Example 1, the difference is that the amount of sodium chloride added in the pretreatment step is significantly reduced, so that its mass concentration in the pretreatment solution is only 0.5%, while the rest are the same.

[0035] Comparative Example 5 Compared with Example 1, the difference is that the amount of sodium chloride added in the pretreatment step is significantly increased, so that its mass concentration in the pretreatment solution reaches 8%, while the rest are the same.

[0036] Comparative Example 6 Compared with Example 1, the difference is that before the composite coagulation and precipitation in step four, a strong alkali was artificially added to forcibly adjust the pH of the pretreatment solution to 7.5; all other aspects are the same.

[0037] Comparative Example 7 A conventional water washing and peeling machine is used, with a water-to-coffee ratio of 5:1. After peeling, the coffee is placed in a fermentation tank for natural fermentation and degumming, which takes 36 hours. After fermentation, the coffee is washed with plenty of clean water.

[0038] Comparative Example 8 The same micro-water peeling process as in Example 1 was used, but an equal amount of a single commercially available pectinase was added in step S2, while the rest of the steps were the same.

[0039] Performance testing and results data Test Example 1: Slurry Viscosity and Zeta Potential The slurries from Examples 1 to 6 and Comparative Examples 1 to 6, after peeling and corresponding pretreatment and stirring, were taken as test samples. The apparent viscosity of each sample was tested using a rotational rheometer. The test system temperature was set to 25℃, a coaxial cylindrical fixture was configured, and the shear rate scan range was set from 0.1 s⁻¹ to 100 s⁻¹. The apparent viscosity data was recorded when the shear rate stabilized at 10 s⁻¹. The Zeta potential of each sample was measured using a dynamic light scattering analyzer. Each sample was diluted 100-fold with deionized water. The diluted sample solution was injected into the U-shaped pleated capillary sample cell without air bubbles using a syringe. The test temperature was set to 25℃, and after equilibration for 120 seconds, electrophoretic mobility was measured. The instrument system automatically converted the mobility into a Zeta potential value according to the Smoluchovsky equation. Each sample underwent three independent parallel tests, and the average value was recorded.

[0040] Table 1. Apparent viscosity and Zeta potential test data of the slurries from each example and comparative example.

[0041] According to the data in Table 1, the apparent viscosity of the slurry in Examples 1 to 6 was controlled between 135 mPa·s and 155 mPa·s, and the Zeta potential was maintained in the low absolute value range of -11 mV to -14 mV. In Comparative Example 1, without the addition of sodium citrate, the apparent viscosity was as high as 2845.6 mPa·s. Due to the lack of the strong competitive polydentate ligand effect of citrate, the galacturonic acid residues in the pectin macromolecular chain maintained a dense three-dimensional network cross-linked structure through calcium ions, and the physical cross-linked network inside the fluid hindered the flow. After the addition of sodium citrate in the examples, the free and cross-linked calcium ions were effectively chelated, the physical cross-linking points of pectin broke, and the macromolecular chain transformed into a random coil conformation, thereby significantly reducing the apparent viscosity and weakening the steric hindrance of enzyme molecule diffusion into the substrate.

[0042] Comparative Example 2, without added sodium chloride, had an absolute Zeta potential of -31.2 mV and an apparent viscosity of 1560.3 mPa·s; Comparative Example 4, with extremely low sodium chloride addition, had an absolute Zeta potential of -22.6 mV and an apparent viscosity of 845.2 mPa·s. Comparing the data with Example 1, it is clear that the free sodium and chloride ions provided by medium to high concentrations of sodium chloride increase the ionic strength of the environment. According to the double-layer compression theory, high ionic strength effectively compresses the thickness of the diffused double layer on the surface of negatively charged pectin particles, partially shielding the negative charge on the particle surface, resulting in a decrease in the absolute Zeta potential. The reduction in electrostatic repulsion decreases the effective hydrodynamic radius of macromolecular chain segments in solution, reducing internal frictional resistance and further contributing to viscosity reduction under microaqueous conditions from a physicochemical perspective. In Comparative Example 6, after being forcibly adjusted to a slightly alkaline environment, the carboxyl groups on the pectin molecules completely dissociated, leading to a sharp increase in negative charge density and a Zeta potential of -35.8 mV. The enhanced electrostatic repulsion caused the viscosity to rebound. The above data confirm that the synergistic effect of chemical chelation and physical double-layer compression can effectively reduce the viscosity of high-concentration pectin slurry, ensuring the mass transfer efficiency of the subsequent biological degumming process.

[0043] Test Example 2: Coagulation Effect and Water Quality During the processing of each embodiment and comparative example, a calibrated portable pH meter was used to monitor and record the pH value in real time from the time the fresh fruit entered the peeling machine until the biological degumming was completed and chitosan was added. After each group completes the composite coagulation reaction in step four, weigh 100g of the mixed slurry and place it in a centrifuge tube, then centrifuge at 4000r / min for 10 minutes. After centrifugation, the supernatant was carefully removed and its transmittance was measured at a wavelength of 600 nm using a UV-Vis spectrophotometer to characterize the removal rate of residual pectin and impurities in the circulating water. Collect the bottom sediment after centrifugation, dry it to constant weight at 105℃ using a rapid moisture analyzer, and calculate the water holding capacity of the sediment by the mass difference method. Sample three times for each group, and take the arithmetic mean of the results.

[0044] Table 2 shows the test data for pH value, water retention rate of precipitate, and transmittance of supernatant for each example and comparative example.

[0045] According to the data in Table 2, the final reaction pH values ​​of Examples 1 to 6 were all stable between 4.65 and 4.92, which falls within the simultaneous dissociation window of pectin and chitosan. In Comparative Example 3, after replacing sodium citrate with an equimolar amount of EDTA-2Na, the final pH value dropped to 3.65, far from the sweet zone of efficient charge neutralization. The buffer formed by citric acid and sodium citrate played a crucial pH anchoring role in the microaqueous environment, offsetting the impact of endogenous acids in fresh fruit and the subsequent weakly acidic environment of chitosan. When the pH value deviated from this range, such as when the pH of Comparative Example 6 rose to 7.5 due to the influence of strong alkali, the amino groups of chitosan could not be protonated to generate a positive charge, resulting in the inability of it to electrostatically complex with the negatively charged pectin molecules. The transmittance of the supernatant was only 8.4%, proving that a large amount of pectin remained in the water.

[0046] Regarding the solid-liquid separation effect, the water holding capacity of the precipitate in Examples 1 to 6 remained at a low level of 65.9% to 71.2%, and the transmittance of the supernatant all exceeded 90%. Comparative Examples 2 and 4, lacking sufficient sodium chloride concentration, had precipitate water holding capacities as high as 94.5% and 89.6%, respectively. According to the electrostatic shielding theory, in a pure water environment with extremely low salt concentration, the strong electrostatic attraction between polyelectrolytes leads to rapid cross-linking of macromolecular chains, forming a loose three-dimensional hydrogel network that captures a large amount of free water. In the examples, the 2% to 3% mass concentration of sodium chloride produced a moderate electrostatic shielding effect, altering the thermodynamic path of complex formation, preventing the formation of an infinite network gel, and promoting chain segment folding and dehydration shrinkage of the polyelectrolyte complex, ultimately forming a high-density, dense condensed phase. In Comparative Example 5, due to excessively high salt concentration, the strong shielding effect completely blocked the electrostatic attraction between components, resulting in the inability to undergo phase separation and precipitation. These results confirm that the present invention successfully solves the technical challenges of efficient pectin removal and closed-loop treatment of circulating water under micro-water conditions through a citric acid buffer system and a salt-assisted composite coagulation mechanism.

[0047] Test Example 3: Degumming Rate and Water Consumption Washed coffee bean samples with shells obtained from Examples 1 to 6 and Comparative Examples 1 to 6 were collected and dried in an oven to constant weight. The residual pectin content on the surface of the final shelled bean was quantitatively determined by the carbazole-sulfuric acid colorimetric method. The dried shelled bean sample was weighed, and the residual pectin on the surface was extracted by adding 0.5 mol / L disodium ethylenediaminetetraacetate solution in a boiling water bath. The extract was then collected and concentrated sulfuric acid and carbazole ethanol solution were added in sequence to carry out the colorimetric reaction. The absorbance value was measured at a wavelength of 530 nm. The mass of residual pectin on the sample surface was calculated according to the standard curve. The degumming rate was calculated by the difference between the initial total amount of pectin in fresh coffee cherries before processing and the amount of residual pectin on the surface of the finished husk-in-beans. The total amount of clean water consumed throughout the entire processing process was statistically analyzed. The sum of the initial water replenishment and rinsing water consumption required for processing each ton of fresh fruit was recorded to obtain comprehensive water consumption data per ton of fruit. For the proportion of recycled water that cannot be reused, the actual discharge volume was recorded and the corresponding amount of fresh water was replenished. Each sample was measured in parallel five times, and the average value was taken after excluding outliers.

[0048] Table 3. Degumming rate, residual gum content, and comprehensive water consumption per ton of fruit for each example and comparative example.

[0049] According to the data in Table 3, the residual pectin content on the surface of the finished coffee beans in Examples 1 to 6 was controlled below 0.6 mg / g, the degumming rate was stable between 98.9% and 99.8%, and the comprehensive water consumption per ton of coffee was at an extremely low level of 53 L / t to 73 L / t. In contrast, Comparative Example 1, without the addition of sodium citrate, had a residual pectin content as high as 12.85 mg / g, and a degumming rate of only 81.35%. This confirms that the dissociation effect of citrate on the calcium bridges of the pectin Egg-box network is a prerequisite for achieving efficient biological degumming. Since the physical cross-linking network was not destroyed, the diffusion resistance inside the substrate greatly limited the mass transfer efficiency of enzyme molecules, making it difficult to achieve complete degumming even with extended reaction time.

[0050] Regarding water resource utilization, Comparative Example 2, which did not add sodium chloride, achieved a high initial degumming rate through enzymatic action, but its comprehensive water consumption per ton of fruit jumped to 425.6 L / t. Combined with Test Example 2, this is because the lack of ionic strength control in the downstream process prevented chitosan and pectin from forming a dense aggregate phase, resulting in a large-volume macroscopic hydrogel. This made mechanical centrifugation unable to achieve effective solid-liquid separation, and the recycled water lost its reuse value, requiring continuous replenishment of fresh water. Although Comparative Example 3 used EDTA-2Na to reduce viscosity, the lack of pH anchoring effect from the citric acid buffer system caused the pH to deviate from the optimal activity range of the biological enzymes and the charge neutralization window of the downstream complex coagulation, resulting in a simultaneous decrease in both the degumming rate and water recovery rate.

[0051] The data from Comparative Examples 4 and 5 further verified the thermodynamic boundary significance of sodium chloride concentration. When the salt concentration is too low or too high, the composite coagulation process will fail due to the electrostatic shielding effect being too weak or too strong, resulting in a large accumulation of polygalacturonic acid in the circulating water. This not only increases the water consumption per ton of fruit but also affects the front-end degumming efficiency due to water quality deterioration. In contrast, the example successfully integrated high-efficiency degumming with a closed-loop cycle of extremely low water consumption through the synergy of chemical chelation and physical double-layer compression in the pretreatment stage and salt-induced coagulation under pH anchoring in the back end. The data confirmed the industrial application value of the present invention in ensuring degumming quality and significantly reducing environmental impact under micro-water conditions.

[0052] Test Example 4 Cyclic Stability Examples 1 to 6 and Comparative Examples 2, 4 and 5 were selected as experimental groups. Under the continuous cycle processing mode, all the supernatant obtained after solid-liquid separation in step four of each group was reused for the pretreatment and peeling process of the next batch of fresh fruit. The continuous cyclic processing batch was set to 20 batches. After the 1st, 5th, 10th, 15th and 20th cyclic batches were completed and the composite coagulation solid-liquid separation was completed, samples of the supernatant of each group were collected. The chemical oxygen demand (COD) of the supernatant was determined using the potassium dichromate method. The total concentration of soluble sugars and polygalacturonic acid accumulated in the supernatant was determined by the phenol-sulfuric acid method to assess the accumulation trend of organic matter. The maximum number of cycles required for forced discharge and replacement of fresh water due to water quality deterioration was recorded for each group during continuous circulation. Three samples were taken and tested at each cycle node, and the average value was recorded.

[0053] Table 4. Water quality monitoring and cycle stability data for each embodiment and comparative example during continuous circulation.

[0054] According to the data in Table 4, after 20 consecutive cycles, the COD value of the circulating water in Examples 1 to 6 remained at a low level of 2950 mg / L to 3900 mg / L, and the cumulative concentration of pectin fragments also remained within a low range. None of them met the mandatory discharge standards, demonstrating extremely high process stability. Comparative Examples 2 and 4 showed explosive growth in COD value within a small number of cycles, with the maximum number of cycles that could be circulated in Comparative Example 2 being only 2.

[0055] Based on the innovative mechanism analysis of this solution, the core challenge of the micro-water process lies in the continuous accumulation of pectin degradation products in the circulating water. If these cannot be effectively removed, the viscosity will rapidly increase and enzyme activity will be inhibited. In this embodiment, sodium citrate and sodium chloride, which are added in step one, are used for multiple purposes in the downstream process through the conversion of their physicochemical properties. Under the action of the pH anchoring mechanism, the citric acid buffer system will be precisely locked at the electrostatic complexing window of 4.5 to 5.0, so that the positively charged chitosan and the negatively charged pectin fragments can undergo efficient charge neutralization. At the same time, the 2% to 3% concentration of sodium chloride acts as a coagulation morphology regulator, and the moderate electrostatic shielding effect changes the thermodynamic path of the complex, causing the polyelectrolyte complex to undergo chain segment folding and dehydration shrinkage, forming a dense condensed phase that is high-density and easy to separate by centrifugation. This ensures that the pectin contaminants generated in each batch can be removed from the circulation in a timely and thorough manner in the downstream process.

[0056] In contrast, in Comparative Example 4, the sodium chloride concentration was too low, resulting in insufficient ionic strength to generate effective electrostatic shielding. This led to the formation of a loose hydrogel with extremely high water content between chitosan and pectin. Under conventional centrifugation conditions, this gel was extremely difficult to separate into wet and dry phases, causing a large amount of organic matter to remain in the circulating liquid with the water. With each batch, organic pollutants accumulated exponentially. In Comparative Example 5, the excessive salt concentration caused over-shielding, inhibiting the electrostatic attraction and preventing the composite coagulation reaction from starting. In Comparative Example 6, the pH imbalance caused a lack of charge in chitosan, also preventing the formation of effective precipitation. The experimental results demonstrate that this invention, through precise control of ionic strength and pH environment, utilizes salt-assisted composite coagulation technology to completely open up the water circulation loop for continuous micro-water processing, achieving an extremely high removal rate of organic pollutants while ensuring processing quality.

[0057] Test Example 5: Enzyme Activity Maintenance Rate and Reagent Residue Circulating liquid samples were collected from each embodiment and comparative example during continuous processing, and the supernatant of the first, tenth, and twentieth batches after the degumming reaction was completed was extracted. The residual pectinase activity in the circulating solution was determined by the DNS method. Galacturonic acid was used as a standard. A certain amount of circulating solution was reacted with pectin substrate solution at 40℃ and pH 4.8 for 30 minutes. The reaction was terminated by adding DNS reagent and color development was performed. The absorbance value was measured at a wavelength of 540 nm, and the enzyme activity units contained in each milliliter of circulating solution were calculated. For finished coffee beans with shells after continuous processing, assess the content of residual chemical reagents on the surface, weigh the washed and dried beans with shells, add deionized water and perform ultrasonic extraction. The concentrations of citrate and sodium ions in the extract were determined by ion chromatography; the concentration of chloride ions was determined by silver nitrate titration, and the reagent residue on the surface of each kilogram of shelled beans was calculated based on the extraction ratio. The assay was repeated three times and the average value was recorded to analyze the correlation between the rate of enzyme activity decay during the cycle and the chemical environment.

[0058] Table 5. Enzyme activity maintenance rate and reagent residue on the surface of finished soybeans in each example and comparative example.

[0059] According to the data in Table 5, after 20 consecutive batches of processing in Examples 1 to 6, the pectinase activity retention rate in the circulating liquid remained between 79% and 87%, and the residual amounts of sodium citrate and sodium chloride on the surface of the finished coffee beans were extremely low, both within the range of 10 mg / kg to 22 mg / kg. In Comparative Example 3, after replacing sodium citrate with EDTA-2Na, the enzyme activity retention rate in the 20th batch was only 15.4%, which confirms the core value of the citrate buffer system in maintaining enzyme stability. Since EDTA causes a significant drop in pH that exceeds the enzyme's tolerance range while chelating calcium ions, it causes irreversible denaturation of protein molecules. In contrast, the sodium citrate of this invention not only reduces environmental viscosity through the calcium bridge dissociation mechanism, but the buffer pairs it forms also provide a stable catalytic microenvironment for pectinase through the pH anchoring mechanism.

[0060] In terms of reagent residue control, the examples showed significantly better characteristics than the comparative examples. In Comparative Example 2, due to the absence of sodium chloride, a dense aggregated phase could not be formed in the downstream complex coagulation stage. Pectin fragments and chemical reagents remained on the surface of the shelled beans with a large amount of water, and the sodium citrate residue was as high as 45.2 mg / kg. In the examples, the 2% to 3% concentration of sodium chloride played a role in regulating the thermodynamic orientation of complex coagulation. Under this ionic strength, the electrostatic shielding effect caused the complex formed by chitosan and pectin degradation products to undergo rapid dehydration and shrinkage. This densification physical phase transition process displaced the anhydrous salts and citrate ions dissolved in the free water into the precipitate phase and entered the next stage with the circulating water.

[0061] Comparative Example 5, due to its excessively high initial salt concentration, showed a dramatic increase in sodium chloride residue on the surface of the finished coffee beans, reaching 115.6 mg / kg. Furthermore, the strong electrostatic shielding effect generated by the high-salt environment not only disrupted the solid-liquid separation loop at the downstream end but also interfered with the electrostatic balance within the enzyme protein molecules, resulting in a decrease in enzyme activity maintenance rate to 32.8%. Comparative Example 6, processed under alkaline conditions, not only suffered complete enzyme inactivation but also failed to achieve any effective coagulation due to charge repulsion, with reagent residue increasing synchronously with water quality deterioration. The data further demonstrate that this invention, through a multi-purpose mechanism, utilizes a viscosity-reducing reagent added at the front end to transform into a coagulation regulator at the downstream end. This not only ensures the continuous and efficient biocatalytic process but also significantly reduces chemical residue on the surface of the finished coffee beans by inducing the formation of a hydrophobic, shrinking, dense coagulated phase, thus ensuring the maintenance of bioactivity and product cleanliness during coffee processing.

[0062] Test Example 6: Economic Benefits Evaluate the comprehensive economic benefits of the micro-water circulation system in a real industrial production environment; Using a single batch processing of 1 ton of fresh coffee cherries as the baseline scale, complete process verification was conducted under the processing conditions of Examples 1 to 6, Comparative Examples 7 and 8, respectively. Record the total chemical consumption of each group in the peeling, degumming and water treatment processes, and calculate the chemical cost per ton of fresh fruit processing based on the average market bulk purchase price of industrial-grade raw materials. By monitoring the fresh water replenishment and final wastewater discharge throughout the entire process using flow meters, and combining this with local industrial water prices and high-concentration organic wastewater discharge fees, the water and wastewater treatment costs per ton of fresh fruit processed are calculated. Connect a power quality analyzer to the power-consuming equipment such as peeling machine, mixing degumming tank, centrifuge and hot air dryer to record the total power consumption of a single processing cycle and convert it into energy cost; By summarizing the three core expenditures of pharmaceuticals, water, and energy, the overall operating cost is obtained. Based on the data of Comparative Example 7, the net cost reduction of each embodiment and the comparative example is calculated.

[0063] Table 6. Comprehensive economic evaluation data for processing 1 ton of fresh coffee cherries in each embodiment and comparative example.

[0064] According to the data in Table 6, the comprehensive operating costs of Examples 1 to 6 when processing one ton of fresh coffee fruit ranged from RMB 73.1 to RMB 78.9, achieving a net cost reduction of 29.3% to 34.5% compared to the traditional wet process of Comparative Example 7. Comparative Example 7 did not use chemical agents, so its agent cost was zero. However, the consumption of a large amount of clean water and the generation of high-concentration organic wastewater resulted in water and wastewater treatment costs as high as RMB 78.5, which became the main factor driving up the comprehensive operating costs. Comparative Example 8 introduced enzyme preparations and adopted a micro-water open-loop process, reducing its water and wastewater treatment costs to RMB 35.4. However, due to the lack of a closed-loop wastewater treatment mechanism, the overall cost reduction was only 19.6%, and the economic benefits were not as good as those of Examples 1 and 6.

[0065] Based on the analysis of the process mechanism, the reduction in overall operating cost in the embodiment directly stems from the multiple physicochemical effects of the pretreatment agents in the micro-water system and water treatment closed loop. The addition of sodium citrate and sodium chloride in the pretreatment stage increased the agent cost of the embodiment by RMB 28.7 to RMB 34.2, but this chemical input is converted into cost offsetting factors in subsequent processes. Citrate ions competitively chelate with calcium ions in the pectin network, destroying the three-dimensional cross-linked structure of pectin. Combined with the compression effect of high-concentration sodium chloride on the double electric layer, the processing system maintains a low viscosity state at an extremely low water-to-material ratio. This viscosity reduction effect ensures that the biological degumming reaction can be carried out efficiently in the micro-water environment, reducing the amount of clean water used from the source.

[0066] During the wastewater recycling stage, the chemical components originally added as viscosity reducers undergo functional transfer; the residual sodium citrate in the wastewater forms a buffer system, locking the pH in a charge-neutralization range suitable for complex coagulation; the residual sodium chloride alters the phase transition path of the polyelectrolyte complex through electrostatic shielding, promoting the formation of a dense aggregated phase from chitosan and pectin degradation products; the salt-induced dense coagulation mechanism solves the engineering obstacle of pectin wastewater easily forming loose hydrogels and being difficult to dehydrate, allowing solid-liquid separation to be completed using conventional centrifugation equipment; therefore, the example group can reduce water and wastewater treatment costs to an extremely low level of 1.8 to 2.6 yuan; the above data verify that this solution, through the cross-process reuse of materials, offsets the increased reagent and energy costs due to the introduction of chemical reagents and centrifugation equipment, achieving zero discharge of organic wastewater while possessing economic feasibility at the industrial application level.

[0067] Test Example 7: Flavor Testing Coffee beans with shells prepared in Example 1, coffee beans with shells prepared in Comparative Example 7 and the control group prepared by the traditional wet process were selected, and coffee beans with shells prepared in Comparative Example 9 were added as experimental samples. Each group of samples was dehulled under the same environmental conditions to obtain green coffee beans; The raw beans in each group were roasted to medium roast using a standard sample roaster; the roasted beans were then degassed and allowed to rest at room temperature for 24 hours, and then ground to the standard cupping diameter requirements. Three SCA-certified coffee quality assessors conducted blind taste tests and scored the coffees. The evaluation criteria included aroma, flavor, acidity, body, cleanliness, and total score. The average score of the three assessors was used as the final sensory quantitative data. The volatile components of each group of roasted coffee beans were quantitatively analyzed by headspace solid-phase microextraction combined with gas chromatography-mass spectrometry, and the total content of furan and pyrazine compounds that are highly correlated with the characteristic flavor of coffee was recorded.

[0068] Table 7. Sensory cupping scores and characteristic volatile compound content of coffee beans in each group

[0069] According to the data in Table 7, Example 1 achieved a final total score of 83.42 in the cupping test, which was better than the 81.75 score of Comparative Example 7 and the 78.58 score of Comparative Example 9. Among the individual indicators, the cleanliness score of Example 1 was 8.25, which was higher than that of the traditional water washing process and the anhydrous process. Its total content of furan and pyrazine reached 412.6 mg / kg, indicating that the aromatic precursor substances were well preserved.

[0070] Based on the analysis of the process mechanism, the traditional water washing process relies on natural fermentation to degrade pectin, with a fermentation cycle of up to 36 hours. During the biochemical process, free fatty acids such as acetic acid and butyric acid produced by microbial metabolism can easily penetrate into the soybean, resulting in a decrease in cleanliness. At the same time, some water-soluble aromatic precursors will be precipitated and lost during long-term soaking, resulting in a low content of volatile compounds. The waterless mechanical process, due to the lack of water for cleaning and buffering, relies solely on the local high temperature generated by mechanical friction, which can easily cause thermal damage to pectin residues, producing astringent and off-flavors, resulting in lower cleanliness and flavor scores.

[0071] Example 1 uses a pretreatment solution combined with a special compound degumming enzyme, which can sever the physical connection between pectin and bean shell in only 45 to 60 minutes under micro-aqueous conditions. The targeted enzymatic hydrolysis mechanism avoids the risk of uncontrolled microbial fermentation caused by prolonged soaking and fermentation, and prevents the generation of undesirable organic acids. The extremely short processing time maintains the compactness of the coffee bean cell structure, prevents the loss of internal free amino acids and reducing sugars, and ensures that the green beans can undergo sufficient Maillard reaction and caramelization reaction in the subsequent roasting stage. This explains the increase in furan and pyrazine content in Example 1 from a chemical composition perspective, demonstrating that this method effectively removes flavor defects while improving processing efficiency.

[0072] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A specialized compound degumming enzyme for micro-hydronic deskinning and degumming of fresh coffee cherries, characterized in that, It is made from the following raw materials in parts by weight: pectinase dry powder: 70-90 parts; cellulase dry powder: 5-25 parts; calcium chloride powder: 5 parts.

2. The special compound degumming enzyme for micro-hydraulic degumming of fresh coffee cherries according to claim 1, characterized in that, The specialized composite degumming enzyme is supplied with Ca by calcium chloride. 2+ Pre-activated pectinase active center.

3. The special compound degumming enzyme for micro-hydraulic degumming of fresh coffee cherries according to claim 1, characterized in that, The pectinase dry powder has an enzyme activity ≥50000U / g and a moisture content <8% by mass; the cellulase dry powder has an enzyme activity ≥10000U / g and a moisture content <8% by mass.

4. The special compound degumming enzyme for micro-hydraulic degumming of fresh coffee cherries according to claim 1, characterized in that, The preparation method of the special composite degumming enzyme includes the following steps: pectinase dry powder, cellulase dry powder and calcium chloride powder are put into a three-dimensional mixer and mixed and stirred at a speed of 30-40 revolutions per minute for 30-40 minutes in a closed environment with a temperature of 20-25℃ and a relative humidity of 20%-40%, and the special composite degumming enzyme is discharged.

5. An integrated processing method for micro-hydraulic degumming and degumming of fresh coffee cherries, comprising a special composite degumming enzyme for micro-hydraulic degumming and degumming of fresh coffee cherries according to any one of claims 1-4, characterized in that, Includes the following steps: S1. The selected fresh coffee cherries are sent into a micro-water peeling machine, and a pretreatment solution consisting of water, sodium citrate and sodium chloride is added for peeling to separate the coffee cherries skin and the coffee beans with husks containing gum. S2. Input the coffee beans with shells obtained in S1 into a degumming tank, add a special compound degumming enzyme for biological degumming, and stir the reaction at 30-50℃ to carry out biological degumming. S3. After degumming is completed, add water to rinse the coffee beans in their shells and separate the gum and wastewater. S4. Collect the wastewater obtained in S3 and add chitosan to carry out a complex coagulation reaction. After solid-liquid separation, obtain recycled water, which is recycled back to step S1. S5. Dry the coffee beans in their husks after rinsing in S3 until the moisture content is 10-11%.

6. The integrated processing method for micro-moisture peeling and degumming of fresh coffee cherries according to claim 5, characterized in that, In S1, the mass concentration of sodium citrate in the pretreatment solution is 0.5%, and the mass concentration of sodium chloride is 2.5%; the mass ratio of water to fresh coffee cherries is 1:50 to 80.

7. The integrated processing method for micro-hydration peeling and degumming of fresh coffee cherries according to claim 5, characterized in that, In S2, the amount of the special compound degumming enzyme added is 0.02-0.08% of the mass of the coffee beans in their shells; the degumming reaction time is 45-60 minutes, and the stirring speed is 15 revolutions per minute.

8. The integrated processing method for micro-moisture peeling and degumming of fresh coffee cherries according to claim 5, characterized in that, In S4, the amount of chitosan added is 0.1% of the wastewater mass; during the composite coagulation reaction, the pH value is anchored in the range of 4.5-5.0 by the buffering effect of sodium citrate.

9. The integrated processing method for micro-moisture peeling and degumming of fresh coffee cherries according to claim 5, characterized in that, In S4, the electrostatic shielding effect generated by the sodium chloride induces the polyelectrolyte complex to undergo dehydration and shrinkage, forming a high-density dense condensed phase; the solid-liquid separation is performed by centrifugation at a speed of 4000 r / min.

10. The integrated processing method for micro-moisture peeling and degumming of fresh coffee cherries according to claim 5, characterized in that, The specific implementation method of S5 is as follows: put the washed coffee beans in their shells into a hot air circulating dryer and dry them at 50-55℃ until the moisture content is 10.5±0.5%.

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