Preparation process for improving stability of coffee liquid

Abstract

The application discloses a preparation process for improving stability of coffee liquid and relates to the technical field of food processing. The preparation process comprises the following steps: (1) mixing tannin enzyme, cellulase, hemicellulase and complex protease with deionized water to form a primary enzyme liquid, adding the primary enzyme liquid into carrier beads, standing, rinsing, air-drying and obtaining immobilized enzyme; (2) filtering high-concentration coffee liquid by using a filter with a pore size of 1-5 microns, injecting the filtrate into an enzyme hydrolysis reaction bin, and then adding the immobilized enzyme into the enzyme hydrolysis reaction bin for enzyme hydrolysis, and obtaining an enzyme hydrolysis liquid; and (3) filtering the enzyme hydrolysis liquid, transferring the filtrate into a blending tank, adjusting the pH to 5-6, sterilizing and obtaining the coffee liquid. The preparation process can not only reduce the generation of precipitates in the coffee liquid and improve the stability, but also improve the antibacterial and antiseptic performance of the coffee liquid to a certain extent, prolong the shelf life, and reduce the deposition of coffee stains on teeth when the coffee liquid is drunk, thereby improving the consumption experience.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, and in particular to a preparation process for improving the stability of coffee liquid. Background Technology

[0002] Coffee concentrate is made by grinding roasted coffee beans into powder and extracting them with water, allowing the flavor compounds in the coffee to fully dissolve in the water before concentration. It appears as a brown liquid, has a rich and mellow coffee flavor, and is becoming increasingly popular, which has promoted the rapid development of coffee concentrate and coffee beverages. Coffee concentrate comes in low-concentration (≤6°Bx) and high-concentration (7–20°Bx) versions. Compared to low-concentration coffee, high-concentration coffee currently better meets the public's demand for personalized beverage blends with other ingredients. However, due to its high concentration, high-concentration coffee is not only high in caffeine but also in tannins, fats, proteins, sugars, and cellulose. This makes it unstable within its shelf life, particularly prone to sedimentation, leading to increased turbidity, decreased original coffee brightness and color, and uneven flavor due to the aggregation and precipitation of large molecules. This negatively impacts the overall sensory experience of the coffee or coffee beverage, negatively affecting consumers. Therefore, it is necessary to improve the stability of high-concentration coffee to prevent sedimentation within its shelf life and enhance the consumer experience. Furthermore, currently available coffee concentrates and beverages have poor antibacterial properties and short shelf lives. To extend shelf life, excessive amounts of preservatives are added, which is detrimental to health with long-term consumption.

[0003] CN 117678661 A discloses a method for improving the stability of coffee liquid by removing large, easily precipitated coffee molecules through staged filtration, resulting in a more stable coffee liquid. However, this method removes a significant amount of large molecules, which leads to a loss of some of the coffee liquid's flavor. Furthermore, it uses hollow fiber membrane columns with a pore size of 0.2–0.5 μm, placing high demands on the filter membrane and requiring frequent replacements, making it unsuitable for large-scale industrial continuous production.

[0004] CN 114287497 A discloses a method for preparing enzymatically hydrolyzed coffee beverages based on a buffer salt system. This method rapidly hydrolyzes, inactivates, and sterilizes the enzymes in a buffer salt system to obtain a coffee beverage with improved stability. However, in this method, the enzymes can only be used once, resulting in high enzyme consumption and increased production costs.

[0005] CN 117223782 A discloses a compound enzyme preparation for improving the stability of coffee liquid, which is prepared from α-amylase, β-glucanase, protein glutaminase, aminopeptidase, phytase, stabilizer and carrier. This compound enzyme preparation can not only improve the stability of concentrated coffee and reduce the precipitation generated during its storage, but also improve the taste of coffee liquid and reduce its bitterness. It has a good stabilizing effect, but it does not solve the problem of coffee beverage preservation, and the enzyme cannot be recycled after being added.

[0006] In summary, this application provides a preparation process for improving the stability of coffee liquid. Summary of the Invention

[0007] To address the above shortcomings, this invention provides a preparation process for improving the stability of coffee liquid, solving the problems of low stability, easy precipitation, and inability to recycle and reuse enzymes after addition in existing technologies. The specific technical solution is as follows:

[0008] A preparation process for improving the stability of coffee liquid includes the following steps:

[0009] (1) Preparation of immobilized enzyme: Mix 0.5-1 parts of tanninase, 1-3 parts of cellulase, 1-3 parts of hemicellulase and 2.5-4 parts of complex protease with 5-8 parts of deionized water to form the original enzyme solution. Add the original enzyme solution to the carrier microspheres and let it stand for 10-15 hours. Then rinse the carrier microspheres with water and air dry them naturally to obtain the immobilized enzyme.

[0010] (2) Enzymatic hydrolysis: First, filter the high-concentration coffee liquid using a filter, take the filtrate and inject it into the enzymatic hydrolysis reaction chamber, then put the immobilized enzyme into the enzymatic hydrolysis reaction chamber, stir and hydrolyze at 32-40℃ for 20-24 hours to obtain the enzymatic hydrolysate;

[0011] (3) Filtration, preparation and sterilization: The enzymatic hydrolysate is filtered using a filter, the filtrate is transferred to a preparation tank, the pH is adjusted to 5-6, and sterilization is performed to obtain the final product.

[0012] Further, in step (1), the complex protease is mainly composed of papain, pepsin, bromelain and serine protease, and the weight ratio of papain, pepsin, bromelain and serine protease is 1:(5-8):(0.2-0.7):(1-3).

[0013] Further, in step (1), the method for preparing the carrier microspheres is as follows: chitosan powder is added to a 2% acetic acid solution and stirred to obtain a chitosan gel solution; 0.5M sodium hydroxide solution and anhydrous ethanol are mixed in a ratio of 3 to 5:1 to obtain a molding agent; the chitosan gel solution is slowly added to the molding agent and stirred to form a shape, allowed to stand and harden, washed with pure water until neutral, a 5% glutaraldehyde solution is added, and the microspheres are left to stand overnight at room temperature. The microspheres are then rinsed several times to obtain the carrier microspheres.

[0014] Furthermore, the weight ratio of the chitosan powder to the acetic acid solution is 0.5 to 1:100.

[0015] Furthermore, the degree of deacetylation of the chitosan powder is >95%.

[0016] Further, in step (1), the weight ratio of the original enzyme solution to the carrier microspheres is 4 to 8:100.

[0017] Furthermore, in step (2), the soluble solids content of the high-concentration coffee liquid is 7°Bx to 20°Bx.

[0018] Further, in step (2), the amount of the immobilized enzyme added is 0.6% to 1% of the weight of the coffee liquid.

[0019] Further, in step (3), the sterilization equipment is a plate-type UHT sterilizer or a tubular UHT sterilizer, with sterilization parameters of 90℃~121℃ and sterilization time of 5s~30s.

[0020] Furthermore, the pore size of the filter is 1–5 μm.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] 1. The tanninase, cellulase, hemicellulase and complex protease in this invention can degrade macromolecules such as tannic acid, cellulose and protein in coffee liquid. The tanninase, cellulase, hemicellulase and complex protease have a synergistic effect. When used together, they can improve the enzymatic hydrolysis efficiency of macromolecules in coffee liquid, effectively reduce the formation of precipitates in coffee liquid and improve stability.

[0023] 2. The combined use of tanninase, cellulase, hemicellulase and complex protease in this invention can reduce the bitterness of coffee liquid, increase sweetness and aftertaste, improve taste, and minimize flavor loss, thereby enhancing the overall quality of coffee.

[0024] 3. The papain, pepsin, bromelain, and serine protease in the complex protease of this invention can degrade proteins in coffee liquid. The degradation products contain amino acids and active peptides with antibacterial effects, which can effectively inhibit the growth of putrefactive bacteria such as Staphylococcus aureus and Escherichia coli, and prevent coffee liquid from spoiling. At the same time, the enzymatic hydrolysis products of tannins contain gallic acid, which can inhibit bacteria, effectively improving the preservative performance and extending the shelf life.

[0025] 4. The immobilized enzyme of the present invention is immobilized on a carrier microsphere. After one batch of coffee liquid is enzymatically hydrolyzed, the next batch of coffee liquid can be injected. The carrier microsphere with the immobilized enzyme can be used for enzymatic hydrolysis again. The enzymatic hydrolysis effect remains unchanged after 10 consecutive uses. This scheme can make the enzyme reused, with low enzyme consumption and reduced production costs.

[0026] 5. The preparation process of this invention is simple to operate, does not require high-end production equipment, has low cost, and results in minimal flavor loss during the preparation process, making it suitable for large-scale industrial continuous production.

[0027] 6. The present invention uses tannin enzymes to reduce the deposition of tannin melanin, which to some extent slows down the formation of pigment deposits on the tooth surface after long-term coffee consumption and improves the consumer experience. Detailed Implementation

[0028] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0029] Example 1

[0030] The steps of a preparation process for improving the stability of coffee liquid in this embodiment are as follows:

[0031] (1) Preparation of carrier microspheres: Chitosan powder with a deacetylation degree >95% was added to a 2% acetic acid solution and stirred. The weight ratio of chitosan powder to acetic acid solution was 0.5:100 to obtain a chitosan gel solution. A 0.5M sodium hydroxide solution and anhydrous ethanol were mixed in a 3:1 ratio to obtain a molding agent. The chitosan gel solution was slowly added to the molding agent and stirred to form a solid. The solidified microspheres were allowed to stand and harden. The microspheres were washed with pure water until neutral. A 5% glutaraldehyde solution was added and the microspheres were allowed to stand overnight at room temperature. The microspheres were then rinsed several times to obtain the carrier microspheres.

[0032] (2) Preparation of immobilized enzyme: Mix 0.5 parts of tanninase, 1 part of cellulase, 1 part of hemicellulase and 2.5 parts of complex protease with 5 parts of deionized water to form the original enzyme solution. Add the original enzyme solution to the carrier microspheres and let it stand for 10 hours. Then rinse the carrier microspheres with water and let them air dry to obtain the immobilized enzyme. The weight ratio of the original enzyme solution to the carrier microspheres is 4:100.

[0033] The aforementioned complex protease is mainly composed of papain, pepsin, bromelain, and serine protease, with the weight ratio of papain, pepsin, bromelain, and serine protease being 1:5:0.2:1.

[0034] (3) Enzymatic hydrolysis: First, a high-concentration coffee liquid with a soluble solids content of 7°Bx is filtered using a filter with a pore size of 1μm to remove impurities such as particulate matter. The filtrate is then injected into the enzymatic hydrolysis reaction chamber. The amount of immobilized enzyme added to the enzymatic hydrolysis reaction chamber is 0.6% of the weight of the coffee liquid. The mixture is stirred and hydrolyzed at 32°C for 24 hours to obtain the enzymatic hydrolysate.

[0035] (4) Filtration, preparation and sterilization: The enzymatic hydrolysate is filtered using a filter with a pore size of 1μm. The filtrate is transferred to a preparation tank, the pH is adjusted to 5 with baking soda, and then sterilized at 90℃ for 30s using a plate UHT sterilizer.

[0036] Example 2

[0037] The steps of a preparation process for improving the stability of coffee liquid in this embodiment are as follows:

[0038] (1) Preparation of carrier microspheres: Chitosan powder with a deacetylation degree >95% was added to a 2% acetic acid solution and stirred. The weight ratio of chitosan powder to acetic acid solution was 1:100 to obtain a chitosan gel solution. A 0.5M sodium hydroxide solution and anhydrous ethanol were mixed in a 5:1 ratio to obtain a molding agent. The chitosan gel solution was slowly added to the molding agent and stirred to form a solid. The solidified microspheres were allowed to stand and harden. The microspheres were washed with pure water until neutral. A 5% glutaraldehyde solution was added and the microspheres were allowed to stand overnight at room temperature. The microspheres were then rinsed several times to obtain the carrier microspheres.

[0039] (2) Preparation of immobilized enzyme: Mix 1 part tanninase, 3 parts cellulase, 3 parts hemicellulase and 4 parts complex protease with 8 parts deionized water to form the original enzyme solution. Add the original enzyme solution to the carrier microspheres and let it stand for 15 hours. Then rinse the carrier microspheres with water and let them air dry to obtain the immobilized enzyme. The weight ratio of the original enzyme solution to the carrier microspheres is 8:100.

[0040] The aforementioned complex protease is mainly composed of papain, pepsin, bromelain, and serine protease, with the weight ratio of papain, pepsin, bromelain, and serine protease being 1:8:0.7:3.

[0041] (3) Enzymatic hydrolysis: First, a high-concentration coffee liquid with a soluble solids content of 15°Bx is filtered using a filter with a pore size of 5μm to remove impurities such as particulate matter. The filtrate is then injected into the enzymatic hydrolysis reaction chamber. The amount of immobilized enzyme added to the enzymatic hydrolysis reaction chamber is 1% of the weight of the coffee liquid. The mixture is stirred and hydrolyzed at 40°C for 20 hours to obtain the enzymatic hydrolysate.

[0042] (4) Filtration, preparation and sterilization: The enzymatic hydrolysate is filtered using a filter with a pore size of 5μm. The filtrate is transferred to a preparation tank, the pH is adjusted to 6 with baking soda, and then sterilized at 121℃ for 5s using a tubular UHT sterilizer.

[0043] Example 3

[0044] The steps of a preparation process for improving the stability of coffee liquid in this embodiment are as follows:

[0045] (1) Preparation of carrier microspheres: Chitosan powder with a deacetylation degree >95% was added to a 2% acetic acid solution and stirred. The weight ratio of chitosan powder to acetic acid solution was 0.8:100 to obtain a chitosan gel solution. A 0.5M sodium hydroxide solution and anhydrous ethanol were mixed in a 4:1 ratio to obtain a molding agent. The chitosan gel solution was slowly added to the molding agent and stirred to form a solid. The solidified microspheres were allowed to stand and harden. The microspheres were washed with pure water until neutral. A 5% glutaraldehyde solution was added and the microspheres were allowed to stand overnight at room temperature. The microspheres were then rinsed several times to obtain the carrier microspheres.

[0046] (2) Preparation of immobilized enzyme: Mix 0.6 parts of tanninase, 2 parts of cellulase, 2 parts of hemicellulase and 3 parts of complex protease with 7 parts of deionized water to form the original enzyme solution. Add the original enzyme solution to the carrier microspheres and let it stand for 12 hours. Then rinse the carrier microspheres with water and let them air dry to obtain the immobilized enzyme. The weight ratio of the original enzyme solution to the carrier microspheres is 6:100.

[0047] The aforementioned complex protease is mainly composed of papain, pepsin, bromelain, and serine protease, with the weight ratio of papain, pepsin, bromelain, and serine protease being 1:7:0.6:2.

[0048] (3) Enzymatic hydrolysis: First, a high-concentration coffee liquid with a soluble solids content of 20°Bx is filtered using a filter with a pore size of 4μm to remove impurities such as particulate matter. The filtrate is then injected into the enzymatic hydrolysis reaction chamber. The amount of immobilized enzyme added to the enzymatic hydrolysis reaction chamber is 0.7% of the weight of the coffee liquid. The mixture is stirred and hydrolyzed at 38°C for 22 hours to obtain the enzymatic hydrolysate.

[0049] (4) Filtration, preparation and sterilization: The enzymatic hydrolysate is filtered using a filter with a pore size of 4μm. The filtrate is transferred to a preparation tank, the pH is adjusted to 5.5 with baking soda, and then sterilized at 100℃ for 25s using a plate UHT sterilizer.

[0050] The coffee liquid sedimentation effect of this invention

[0051] Comparative Example 1: This comparative example does not add tanninase, but only uses cellulase, hemicellulase and complex protease. All other steps are the same as in Example 3.

[0052] Comparative Example 2: This comparative example does not add hemicellulase, but only tanninase, cellulase and complex protease are used. All other steps are the same as in Example 3.

[0053] Comparative Example 3: This comparative example does not add complex protease, but only tanninase, cellulase and hemicellulase are used. All other steps are the same as in Example 3.

[0054] Blank control 1: Untreated coffee liquid with the same concentration as in Example 1.

[0055] Blank control 2: Untreated coffee liquid with the same concentration as in Example 2.

[0056] Blank control 3: Untreated coffee liquid with the same concentration as in Example 3.

[0057] Coffee solutions from Examples 1-3, Comparative Examples 1-4, and Blank Controls 1-3 were incubated at 45℃ for 30 days, and precipitation was observed and recorded. Each coffee solution was centrifuged at 4000 rpm for 10 minutes, the supernatant was discarded, and the precipitate was dried at 105℃ to constant weight. The precipitation rate was calculated. Twenty professional coffee tasters evaluated the flavor and mouthfeel of each example and comparative example after diluting it with purified water to an instant drinking concentration (1.5°Bx). Flavor was graded from low to high as four levels: significant flavor loss / significant flavor loss / slight flavor loss / no significant flavor loss. Mouthfeel was graded from high to low as three levels: full-bodied with a sweet aftertaste / slightly bitter / significantly bitter. The evaluation result with the most votes for each sample was recorded as its flavor and mouthfeel evaluation. The results are shown in the table below:

[0058]

[0059] The comparison between the blank control and the examples shows that the preparation process of the present invention can reduce the formation of sediment in coffee liquid and improve stability and quality. The sedimentation data from Example 3 and Comparative Examples 1, 2, and 3 show that tanninase, cellulase, hemicellulase, and complex protease have a synergistic effect. Their combined use can improve the enzymatic hydrolysis efficiency of macromolecules in coffee liquid, effectively reducing sediment formation and improving stability. After incubation at 45℃ for 30 days, only a small amount of dark brown sediment remained at the bottom. The flavor and mouthfeel data from Example 3 and Comparative Examples 1, 2, and 3 show that the combined use of tanninase, cellulase, hemicellulase, and complex protease in this invention can reduce the bitterness of coffee liquid, increase sweetness and aftertaste, improve mouthfeel, and minimize flavor loss, thereby further enhancing the overall quality of coffee. Among these, tanninase has a significant impact on flavor and mouthfeel, possibly because tanninase itself hydrolyzes tannins, reducing the destructive effect of tannins on flavor substances. Furthermore, tanninase also promotes the hydrolysis of macromolecules (proteins, cellulose, hemicellulose) complexes by acting in conjunction with other enzymes, generating more oligosaccharides and increasing the concentration of oligosaccharides in the coffee extract, thereby increasing sweetness and reducing bitterness.

[0060] The coffee liquid preservative effect of this invention

[0061] Comparative Example 4: This comparative example does not contain tanninase, and all other steps are the same as in Example 3.

[0062] Comparative Example 5: No complex protease was added to this comparative example, and all other steps were the same as in Example 3.

[0063] Comparative Example 6: The complex protease in this comparative example does not contain papain and pepsin, and all other steps are the same as in Example 3.

[0064] Comparative Example 7: The complex protease in this comparative example does not contain bromelain and serine protease, and all other steps are the same as in Example 3.

[0065] Comparative Example 8: The complex protease in this comparative example does not contain pepsin and bromelain, and all other steps are the same as in Example 3.

[0066] Comparative Example 9: The complex protease in this comparative example does not contain papain and serine protease, and all other steps are the same as in Example 3.

[0067] Blank control 4: Untreated coffee liquid with the same concentration as in Example 3.

[0068] Preservative Control 1: Untreated coffee liquid with the same concentration as in Example 3, with 0.1% potassium sorbate (by weight of the coffee liquid) added as a preservative. This results in untreated coffee liquid + potassium sorbate preservative.

[0069] Preservative Control 2: The weight of potassium sorbate added to the coffee liquid in Example 3 was 1 / 4 of the weight of potassium sorbate in Preservative Control 1, that is, enzymatically hydrolyzed coffee liquid + 1 / 4 potassium sorbate preservative.

[0070] The applicant unexpectedly discovered during the above enzyme treatment that coffee liquid had good antibacterial and preservative effects and was not easily spoiled. Therefore, the above experiment was designed, and coffee liquids from Comparative Examples 4 to 9, Blank Control 4, Preservative Control 1, and Preservative Control 2 were stored at room temperature. The total bacterial count was detected at weeks 15, 25, and 38 (using the method in GB4789.2-2022). The results are shown in the table below:

[0071]

[0072]

[0073] The comparison between Example 3 and Preservative Control 1, Preservative Control 2, and Blank Control 4 in the table shows that the preparation process of the present invention can effectively inhibit the growth of spoilage bacteria and prevent coffee liquid from spoiling and deteriorating. The coffee liquid prepared by this application only needs to add a small amount of preservative to have a shelf life comparable to that of coffee liquid with conventional preservatives. Even if no preservatives are added, the coffee liquid prepared by this application can have a shelf life of 37 weeks at room temperature, which is not significantly different from the shelf life of conventional preservative-preserved coffee liquid.

[0074] The data from Example 3 and Comparative Examples 4 and 5 show that coffee liquid treated with tanninase and complex protease has antibacterial and preservative effects, which may be related to the presence of antibacterial amino acids, active peptides and gallic acid in the degradation products.

[0075] As can be seen from the data of Example 3 and Comparative Examples 6, 7, 8 and 9, the papain, pepsin, bromelain and serine protease in the complex protease of the present invention work together to decompose the macromolecules in coffee liquid into amino acids and active peptides with antibacterial effects, effectively inhibiting the growth of spoilage bacteria, preventing the coffee liquid from spoiling and deteriorating, and extending the shelf life.

[0076] The applicant selected 60 coffee enthusiasts with healthy teeth and no black stains as subjects, randomly dividing them into two groups (experimental group and control group), with 30 people in each group. The experimental group received coffee prepared in Example 2 diluted to a ready-to-drink concentration (1.5°Bx) and consumed 200 mL daily for 6 months. The control group received coffee prepared in blank control 4 diluted to a ready-to-drink concentration (1.5°Bx) and consumed 200 mL daily for 6 months. After 6 months of consumption, the degree of pigment deposition on the tooth surface was observed. It was found that no one in the experimental group developed coffee stains on their teeth, while 80% of the coffee enthusiasts in the control group developed varying degrees of coffee stains on their teeth. This indicates that the present invention uses tannin enzymes to reduce the deposition of tannin-based melanin, thus mitigating the formation of pigment deposits on the tooth surface after long-term coffee consumption and improving the consumer experience.

[0077] In summary, the preparation process for improving the stability of coffee liquid provided by this invention not only reduces the formation of sediment in coffee liquid and improves its stability, but also enhances the antibacterial and preservative properties of coffee liquid to a certain extent, extending its shelf life. Drinking the coffee liquid of this invention can also reduce the deposition of coffee stains on teeth, thus improving the consumer experience.

[0078] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A process for improving the stability of coffee liquor, characterized in that, Includes the following steps: (1) Preparation of immobilized enzyme: Mix 0.5-1 parts of tanninase, 1-3 parts of cellulase, 1-3 parts of hemicellulase and 2.5-4 parts of complex protease with 5-8 parts of deionized water to form the original enzyme solution. Add the original enzyme solution to the carrier microspheres and let it stand for 10-15 hours. Then rinse the carrier microspheres with water and air dry them naturally to obtain the immobilized enzyme. The complex protease is mainly composed of papain, pepsin, bromelain, and serine protease, and the weight ratio of papain, pepsin, bromelain, and serine protease is 1:(5~8):(0.2~0.7):(1~3). The method for preparing the carrier microspheres is as follows: chitosan powder with a deacetylation degree >95% is added to a 2% acetic acid solution, wherein the weight ratio of the chitosan powder to the acetic acid solution is 0.5~1:100, and the mixture is stirred to obtain a chitosan gel solution; a 0.5 M sodium hydroxide solution is mixed with anhydrous ethanol at a ratio of 3~5:1 to obtain a molding agent; the chitosan gel solution is slowly added to the molding agent and stirred to form the microspheres, which are then allowed to stand and harden. The microspheres are washed with pure water until neutral, and a 5% glutaraldehyde solution is added. After standing at room temperature overnight, the microspheres are rinsed several times to obtain the carrier microspheres. (2) Enzymatic hydrolysis: First, filter the high-concentration coffee liquid using a filter, and inject the filtrate into the enzymatic hydrolysis reaction chamber. Then, add the immobilized enzyme into the enzymatic hydrolysis reaction chamber and stir and hydrolyze at 32~40℃ for 20~24h to obtain the enzymatic hydrolysate. The soluble solids content of the high-concentration coffee liquid is 7°Bx~20°Bx. (3) Filtration, preparation and sterilization: The enzymatic hydrolysate is filtered using a filter, the filtrate is transferred to a preparation tank, the pH is adjusted to 5-6, and sterilization is performed to obtain the final product.

2. The preparation process for improving the stability of coffee liquid according to claim 1, characterized in that, In step (1), the weight ratio of the original enzyme solution to the carrier microspheres is 4~8:

100.

3. The preparation process for improving the stability of coffee liquid according to claim 1, characterized in that, In step (2), the amount of immobilized enzyme added is 0.6% to 1% of the weight of the coffee liquid.

4. The preparation process for improving the stability of coffee liquid according to claim 1, characterized in that, In step (3), the sterilization parameters are 90℃~121℃ and sterilization time is 5s~30s.

5. The preparation process for improving the stability of coffee liquid according to claim 1, characterized in that, The filter has a pore size of 1~5μm.

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