Kale fruit and vegetable composite juice and preparation method thereof

Abstract

The invention discloses kale fruit and vegetable composite juice and a preparation method thereof. The composite juice consists of the following components in percentage by weight: 23-27% of apple juice, 32-34% of celery juice, 7-9% of green cucumber juice, 7-9% of pineapple juice and 23-27% of kale juice. During preparation, the raw materials are pretreated, mixed and blended, and then are sequentially subjected to vacuum degassing, ultrahigh-pressure sterilization and refrigeration. According to the method, the taste is improved through composite enzymolysis and quick-freezing synergistic treatment, a nanoscale homogeneous stable system is adopted, the nutrition is reserved through stepped ultrahigh-pressure sterilization, and nutrition complementation is achieved through accurate compounding. The prepared compound juice is good in taste, rich in nutrition and high in stability, and has remarkable process advancement and product practicability.

Description

Technical field

[0001] The invention relates to the field of fruit and vegetable compound juice beverage production, in particular to kale fruit and vegetable compound juice and a preparation method thereof. [Background Technology]

[0002] As people's health awareness increases, the demand for natural, nutritious, and healthy beverages is increasing. Kale, as a nutritious vegetable, is rich in vitamins, minerals, dietary fiber, and various antioxidants. However, when squeezed alone, it tastes bitter and is difficult for consumers to accept. Currently, kale-related beverages on the market often have the following problems:

[0003] Existing kale juices often have a strong bitter taste, requiring the addition of large amounts of sugar or other additives to improve the taste. This not only increases calorie intake but also violates the concept of a healthy drink. For example, Chinese patent application CN118160883A describes a bitter melon composite fruit and vegetable juice that balances the bitterness by adding emblica oleracea juice and extract. However, there is still a lack of effective solutions for addressing the bitterness of kale.

[0004] Most single-vegetable juices lack comprehensive nutritional content and fail to meet the body's diverse nutritional needs. While kale juice alone is rich in vitamin K, it lacks other important nutrients like vitamin C and dietary fiber. While the composite fruit, vegetable, and grain juice disclosed in Chinese patent publication number CN119837200A incorporates multiple ingredients, it doesn't include kale in its proper formulation.

[0005] In traditional fruit and vegetable juice processing, heat sterilization can easily lead to the loss of heat-sensitive nutrients and affect the color and taste of the drink. For example, patent publication number CN119111708A mentions ultra-high pressure sterilization technology as a way to preserve nutrients, but its application in kale juice is still understudied.

[0006] Kale juice is prone to stratification and precipitation during storage, affecting product quality. Chunjian Fruit and Vegetable Composite Juice, published in CN119867231A, improves stability through homogenization, but the kale juice stabilization process still needs to be optimized.

[0007] To address these issues, those skilled in the art have attempted to improve taste and nutritional value by compounding other fruit and vegetable juices. However, existing compounding schemes suffer from issues such as irrational proportions and imperfect processes. For example, some studies have simply combined kale and apple juice without considering the synergistic effects of other vegetable juices, resulting in minimal taste improvement and insufficient nutritional balance. Therefore, developing a kale and vegetable juice with superior taste, rich nutrition, and advanced processing technology is of great practical significance.

[0008] The disclosure of the above background technology content is only used to assist in understanding the inventive concept and technical solution of the present invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above content has been disclosed on the filing date of this patent application, the above background technology should not be used to evaluate the novelty and creativity of this application. [Summary of the invention]

[0009] The purpose of the present invention is to provide a kale fruit and vegetable composite juice with excellent taste, rich nutrition and advanced technology and a preparation method thereof, so as to solve the technical problems of the above-mentioned prior art such as bitter taste, single nutrition, nutrient loss due to processing technology and poor stability.

[0010] To this end, the present invention adopts the following technical solutions:

[0011] A kale fruit and vegetable compound juice comprises the following raw materials in percentage by weight: 23%-27% apple juice, 32%-34% celery juice, 7%-9% cucumber juice, 7%-9% pineapple juice and 23%-27% kale juice.

[0012] Furthermore, the kale fruit-vegetable composite juice comprises the following raw materials in percentage by weight: 25% apple juice, 33.34% celery juice, 8.33% cucumber juice, 8.33% pineapple juice, and 25% kale juice.

[0013] Furthermore, the preparation method of the apple juice is as follows: after the apples are washed with clean water, peeled and cored manually, they are crushed and squeezed by a machine at high speed and the juice is filtered through a 400-mesh filter.

[0014] Furthermore, the preparation method of the celery juice is: removing the roots of the celery, washing with clean water, using a machine to crush and squeeze the juice at high speed, and filtering through a 400-mesh filter.

[0015] Furthermore, the preparation method of the cucumber juice and pineapple juice is as follows: the cucumber is washed with clean water, peeled and the head and tail are removed manually, and the pineapple is washed, peeled, eyes and cored. The two are mixed and crushed in a mass ratio of 1:1, the juice is squeezed using a high-speed crushing machine and filtered through a 400-mesh filter.

[0016] Furthermore, the kale juice is prepared by:

[0017] a. Wash the kale, remove the old leaves, and take the fresh and tender leaves;

[0018] b. Prepare an enzyme preparation at a ratio of 0.5wt‰ cellulase + 0.3wt‰ pectinase, with the enzyme preparation and leaf mass ratio being 1:100, and enzymatic hydrolysis of the leaves in a constant temperature water bath at 40-50℃ for 5.5-6.5h;

[0019] c. Immediately after enzymatic hydrolysis, freeze at -20℃ for 11-13 hours, then thaw at room temperature. After the leaves soften, use a high-speed crushing machine to extract the juice and filter twice through a 400-mesh filter.

[0020] The present invention also provides a method for preparing kale fruit and vegetable composite juice, comprising the following steps:

[0021] S1. Raw material pretreatment: After washing the kale, remove the old leaves and take the fresh leaves; prepare an enzyme preparation at a ratio of 0.5wt‰ cellulase + 0.3wt‰ pectinase, with an enzyme preparation to leaf mass ratio of 1:100, and enzymatically hydrolyze the leaves in a constant temperature water bath at 40-50°C for 5.5-6.5 hours; immediately after enzymatic hydrolysis, place them in a -20°C quick-freeze for 11-13 hours, then thaw at room temperature. After the leaves soften, use a high-speed crushing machine to extract the juice and filter it twice through a 400-mesh filter; wash the apples, peel and core them manually; remove the roots of the celery and wash them; peel and remove the head and tail of the cucumber; peel, remove the eyes and core of the pineapple, cut them into small pieces, crush them by machine to extract the juice, and filter them through a 400-mesh filter;

[0022] S2 mixing and blending: Mix the single fruit and vegetable juices by weight for 10-20 minutes until uniform; use a high-pressure microfluidizer to process the mixed fruit and vegetable compound juice and then fill it;

[0023] S3. Vacuum degassing: vacuum degassing of the fruit and vegetable compound juice filled in step S2; vacuum degree is -0.05 to -0.08MPa, time 10-15min;

[0024] S4. Ultra-high pressure sterilization: ultra-high pressure sterilization of the fruit and vegetable compound juice after degassing in step S3, and the pressure is released immediately after sterilization;

[0025] S5. Refrigeration: After sterilization in step S4, the fruit and vegetable composite juice product is obtained and stored in a cold storage.

[0026] Furthermore, in the raw material pretreatment in step S1, the crushing mass ratio of cucumber and pineapple is 1:1.

[0027] Furthermore, the sterilization conditions of the ultrahigh pressure sterilization in step S4 are: first maintain the pressure at 400 MPa for 2-4 minutes, then increase the pressure to 500 MPa for 1-3 minutes, and finally increase the pressure to 600 MPa for 1-2 minutes, and the sterilization temperature is controlled at 20-25°C.

[0028] Furthermore, the refrigeration temperature in step S5 is 0-4°C.

[0029] The technical principles and beneficial effects of the present invention are as follows:

[0030] 1. Combined enzymatic hydrolysis and quick freezing synergistic treatment improves taste and enhances nutrient release: A combined enzyme preparation of 0.5wt‰ cellulase and 0.3wt‰ pectinase is used to enzymatically hydrolyze kale leaves at 40-50°C. Cellulase specifically degrades the β-glucan structure in the cell wall, while pectinase breaks down the calcium pectinate between cells, disrupting cell integrity and releasing and degrading bitter substances such as glucosinolates. After enzymatic hydrolysis, the leaves are quickly frozen to -20°C. The expansion of ice crystals within the leaf tissue generates mechanical force, further breaking up incompletely hydrolyzed cells. After thawing, the cellular contents, such as polyphenols and vitamin C, are fully dissolved.

[0031] Compared with traditional juicing technology, this synergistic treatment destroys the release path of bitter substances in kale from the root, while avoiding masking the bitterness by adding sugar, which is in line with the concept of healthy drinks; after the cell walls are broken, nutrients are released from the cell constraints, providing richer basic ingredients for subsequent compounding.

[0032] 2. Nano-scale homogenization and stabilization solves the sedimentation problem after traditional filtration: After mixing, a high-pressure microfluidizer is used to force the composite juice through a narrow channel at a pressure of 200 MPa. The fluid is subjected to shear forces and cavitation effects, reducing the particle size to less than 50 nm. The nano-scale particles form a colloidal dispersion system, enhancing Brownian motion and reducing gravitational sedimentation. At the same time, fine fiber particles are evenly distributed, preventing aggregation and sedimentation.

[0033] Traditional 400-mesh filtration can only remove large particles of impurities but cannot solve the problem of colloidal particle aggregation. This solution achieves stabilization at the microscopic level through physical means, without the need to add thickeners, maintaining the natural properties of the beverage while improving the delicateness and smoothness of the taste.

[0034] 3. A stepped ultra-high pressure sterilization process balances sterilization efficiency and nutrient retention: The sterilization process involves increasing pressure in stages, from 400MPa to 500MPa to 600MPa. The low-pressure stage first disrupts the permeability of microbial cell membranes, the medium-pressure stage slightly denatures proteins, and the high-pressure stage completely inactivates enzyme activity. This stepped pressure system avoids the damage of heat-sensitive components such as vitamin C and chlorophyll caused by single high pressure, while also enhancing the sterilization effect through sudden changes in osmotic pressure.

[0035] Traditional thermal sterilization processes can cause degradation of heat-sensitive substances, and single ultra-high pressure sterilization may cause nutrient loss due to excessive pressure. This solution optimizes the pressure gradient to effectively inactivate microorganisms to meet commercial sterility requirements while retaining the natural color and nutrients to the greatest extent, resolving the "nutrient-sterilization" contradiction of existing sterilization technologies.

[0036] 4. Precise blending and synergistic cell wall breaking achieve complementary and synergistic nutrient composition: Using a blend of 23%-27% apple juice, 32%-34% celery juice, 7%-9% cucumber juice, 7%-9% pineapple juice, and 23%-27% kale juice, the sweet and sour flavors of apple and pineapple counteract the bitterness of kale, while celery and cucumber provide a refreshing taste and kale supplements vitamin K and dietary fiber. Furthermore, the ingredients undergo enzymatic hydrolysis, quick freezing, and homogenization to break down their cell walls, ensuring that nutrients from different sources, such as pectin from apple, potassium from celery, and polyphenols from kale, are evenly distributed in small molecules, enhancing absorption efficiency.

[0037] Existing single vegetable juices have single nutrition and are simply compounded without considering the synergy of ingredients. This solution uses scientific proportions and wall-breaking technology to form a complementary system of nutrients from multiple fruits and vegetables. For example, fat-soluble vitamins and water-soluble vitamins work together to resist oxidation, and dietary fiber and polyphenols jointly promote intestinal health.

[0038] 5. Full-process physical control ensures the product's natural properties and safety: From raw material pretreatment to sterilization, physical methods are used, without the addition of chemical preservatives, colorants, or sweeteners. Enzymatic hydrolysis utilizes food-grade complex enzymes, ultra-high pressure sterilization inactivates microorganisms through physical pressure, and vacuum degassing reduces oxidation reactions. The entire process is controllable and free of chemical residues.

[0039] Existing similar products often rely on additives to improve taste or extend shelf life. This solution replaces chemical additives through process innovation, meeting consumers' demand for "natural, zero-additive" beverages. At the same time, physical processes can accurately control quality and avoid potential health risks of chemical substances to the human body.

[0040] The process of the present invention systematically solves the pain points of existing kale drinks, such as "bitter taste, single nutrition, poor stability, and sterilization damage", through the technical chain of "biological enzymatic hydrolysis-physical wall breaking-gradient sterilization-precise compounding". Its core advantage lies in the synergistic effect of physical and biological means to achieve an all-round improvement in taste, nutrition, and stability without changing the natural properties of the raw materials. It has significantly more advanced technology and product practicality than traditional technologies.

Brief Description of the Drawings

[0041] Figure 1 This is a physical diagram of Example 1 of the present invention. [Specific implementation method]

[0042] It should be understood that the terms described in the present invention are only for describing specific embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the range are also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded within the scope. As used herein, "comprising", "including", "having", "containing" and the like are all open-ended terms, i.e., meaning including but not limited to.

[0043] Example 1

[0044] A method for preparing kale fruit and vegetable composite juice comprises the following steps:

[0045] S1. Raw material pretreatment: After washing the kale, remove the old leaves and select the fresh and tender leaves; prepare an enzyme preparation at a ratio of 0.5 wt‰ cellulase + 0.3 wt‰ pectinase, with an enzyme preparation to leaf mass ratio of 1:100. The leaves are enzymatically hydrolyzed in a constant temperature water bath at 45°C for 6 hours; immediately after enzymatic hydrolysis, they are quick-frozen at -20°C for 12 hours, then thawed at room temperature. After the leaves soften, they are crushed by a high-speed machine to extract the juice and filter through a 400-mesh filter twice; wash the apples, peel and core them manually; remove the roots of the celery and wash them; peel and remove the head and tail of the cucumber; peel, remove the eyes and core of the pineapple, cut them into small pieces, crush them by machine to extract the juice, and filter them through a 400-mesh filter; the crushing mass ratio of the cucumber to pineapple is 1:1;

[0046] S2. Mixing and blending: 25% apple juice, 33.34% celery juice, 8.33% cucumber juice, 8.33% pineapple juice, 25% kale juice by weight, and stir each single fruit and vegetable juice for 15 minutes until uniform; high-pressure microfluidizer was used to process the mixed fruit and vegetable compound juice and then fill it;

[0047] S3. Vacuum degassing: vacuum degassing of the fruit and vegetable composite juice filled in step S2; vacuum degree is -0.06MPa, time 12min;

[0048] S4. Ultrahigh pressure sterilization: The degassed fruit and vegetable composite juice from step S3 is subjected to ultrahigh pressure sterilization, first at 400 MPa for 3 minutes, then increased to 500 MPa for 2 minutes, and finally increased to 600 MPa for 1 minute. The sterilization temperature is controlled at 22°C; the pressure is immediately released after sterilization.

[0049] S5. Refrigeration: After the sterilization in step S4, the fruit and vegetable compound juice product is placed in a cold storage and stored at a refrigerated temperature of 0-4°C. Figure 1 .

[0050] Comparative Example 1

[0051] The weight percentages of the raw materials were changed to: 35% apple juice, 33.34% celery juice, 8.33% cucumber juice, 8.33% pineapple juice, and 15% kale juice. The other process steps were the same as those in Example 1.

[0052] Comparative Example 2

[0053] In step S1 of the preparation method, the kale is washed and then directly crushed and juiced, and then filtered through 400 mesh; the other steps are the same as those in Example 1.

[0054] Comparative Example 3

[0055] In the preparation method, in step S2, the mixture is mixed and prepared before direct filling without high-pressure microfluidization homogenization. The other steps are the same as those in Example 1.

[0056] Comparative Example 4

[0057] In step S3 of the preparation method, ultrahigh pressure sterilization is directly performed without vacuum degassing, and the other steps are the same as those in Example 1.

[0058] Comparative Example 5

[0059] The ultrahigh pressure sterilization conditions in step S4 of the preparation method are 500 MPa pressure maintained for 6 min and temperature 22° C., and the other steps are the same as those in Example 1.

[0060]

Performance test

[0061] The inspection of the product includes the following test indicators and methods:

[0062] 1. Sensory indicators: The fruit and vegetable juice beverages of Example 1 and Comparative Examples 1-5 were subjected to sensory evaluation based on Table 1. The average of all the scores was the final result. The overall color, aroma, taste, mouthfeel, and texture were evaluated by sensory assessors. Ten food professionals were selected as assessors. After sensory evaluation training, those with taste and smell disorders were excluded. The assessors were in good health, had no bad habits such as smoking and drinking, and had strong discrimination and high sensitivity to color, aroma, and taste. All samples were coded with three random numbers. The temperature of each sample group was uniformly 20°C and the samples were placed in white transparent glasses. Rinse your mouth with warm water before sensory evaluation to keep your mouth fresh. The evaluation results are shown in Table 2.

[0063] Table 1 Sensory evaluation scoring table

[0064]

[0065]

[0066] 2. The dietary fiber content and antioxidant activity of Example 1 and Comparative Example 1 were tested; the dietary fiber content was determined by enzymatic gravimetric analysis; the antioxidant activity was measured by DPPH free radical scavenging rate. The results are shown in Table 3.

[0067] 3. Juice yield and polyphenol content were measured for Example 1 and Comparative Example 2. Juice yield was calculated gravimetrically: juice weight after juicing / raw material weight × 100%. Polyphenol content was calculated using the Folin-phenol method, as mg / 100 mL gallic acid. The results are shown in Table 3.

[0068] 4. Test the centrifugal sedimentation rate for Example 1 and Comparative Example 3: Centrifuge at 3000 rpm for 15 min and calculate sedimentation weight / sample weight × 100%. See Table 3 for the results.

[0069] 5. Dissolved oxygen (DO) was measured for Example 1 and Comparative Example 4 using an electrochemical probe method (mg / L). The results are shown in Table 3.

[0070] 6. The total number of colonies (CFU / mL) was determined for Example 1 and Comparative Example 5 using the plate count method. The results are shown in Table 3.

[0071] Table 2 Sensory evaluation results

[0072]

[0073]

[0074] Table 3 Experimental results

[0075]

[0076] Note: × in the table means not tested.

[0077] The data in Table 2 show that Example 1 achieved a significantly higher total sensory score than the comparative examples. The color score for Example 1 was 18.5 ± 1.2, a result of the kale juice's combined enzymatic hydrolysis and quick-freezing process: after enzymatic hydrolysis with cellulase and pectinase at 45°C for 6 hours, the mechanical force of ice crystals during quick freezing at -20°C disrupted the cell structure, allowing the chlorophyll to fully dissolve and stabilize. Compared to Comparative Example 2 (unenzymatic hydrolysis, color score of 12.3 ± 1.8), this process effectively inhibited chlorophyll degradation and oxidative discoloration.

[0078] In the aroma and flavor dimensions, Example 1 scored 17.8±1.5 and 26.7±1.8, respectively, demonstrating the scientific validity of its precise blend: the sweet and sour components of 25% apple juice and 8.33% pineapple juice precisely counteract the bitterness of the kale, while the volatile aldehydes provided by 33.33% celery juice and the C6 alcohols of cucumber juice create a refreshing top note. In Comparative Example 1, the kale juice content was reduced to 15%, resulting in a reduced polyphenol content and a monotonous aroma profile, resulting in a flavor score of only 22.4±1.9.

[0079] In terms of taste and texture, Example 1 scored 18.3±1.0 and 9.2±0.8, respectively, directly reflecting the technical advantages of the homogenization process: 200MPa high-pressure microfluidization refined the particle size to below 50nm, forming a colloidal dispersion system. Compared with Comparative Example 3 (unhomogenized, centrifugal sedimentation rate 8%), it can be seen that the enhanced Brownian motion in the homogenization process improves the stability of the system, and the uniform distribution of fine fibers brings a silky taste.

[0080] The data in Table 3 show that Example 1 has a dietary fiber content of 2.3 g / 100 mL and a DPPH clearance rate of 68%, significantly higher than Comparative Example 1 (1.7 g / 100 mL, 55%). This is due to the enzymatic hydrolysis-quick freezing synergistic wall-breaking process: the combined system of 0.5 wt‰ cellulase and 0.3 wt‰ pectinase destroys the cell wall β-glucan and calcium pectate structure, increasing the dietary fiber exposure rate by 40%. Simultaneously, polyphenols are released from cell constraints, and their catechol structures undergo electron transfer reactions with DPPH free radicals. Comparative Example 2 (direct juicing) has a lower juice yield and polyphenol content than Example 1 due to its low cell wall breakage rate.

[0081] The stepped ultrahigh-pressure sterilization process achieves both sterilization efficacy and nutrient retention. Compared to Comparative Example 5 (single 500MPa sterilization for 6 minutes), the stepped pressure avoids the oxidative damage to vitamin C caused by high pressure, increasing DPPH clearance by 12%. This process achieves commercial sterility at 22°C by disrupting microbial cell membrane permeability at low pressure (400MPa), inducing mild protein denaturation at medium pressure (500MPa), and inactivating enzyme activity at high pressure (600MPa).

[0082] The necessity of the vacuum degassing process is reflected in the dissolved oxygen data: the DO value of Example 1 is less than 1 mg / L, while the DO value of Comparative Example 4 (non-degassed) reaches 5 mg / L. High dissolved oxygen accelerates the oxidative polymerization of polyphenols, resulting in a 42% decrease in color score, confirming the key role of -0.06 MPa vacuum and 12 min degassing treatment in inhibiting oxidation reactions.

[0083] This invention achieves a synergistic improvement in taste, nutrition, and stability through a technological chain of "biological enzymatic hydrolysis - physical cell wall breaking - gradient sterilization - precise compounding." Compared with traditional processes, the combined enzymatic hydrolysis-quick freezing process increases the degradation rate of bitter substances, and nano-scale homogenization reduces the precipitation rate by 81.2%. Data demonstrates significant synergistic effects across the various process steps: enzymatic cell wall breaking lays the foundation for nutrient release, homogenization enhances system stability, gradient sterilization balances safety and nutrition, and precise compounding optimizes the sensory experience, ultimately resulting in an innovative product that combines functionality with palatability.

[0084] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0085] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

Claims

1. A kale fruit and vegetable composite juice, characterized in that: The raw materials include the following weight percentages: 23%-27% of apple juice, 32%-34% of celery juice, 7%-9% of cucumber juice, 7%-9% of pineapple juice, and 23%-27% of kale juice.

2. The kale fruit and vegetable composite juice according to claim 1, characterized in that: The kale fruit-vegetable composite juice comprises the following raw materials in percentage by weight: 25% apple juice, 33.34% celery juice, 8.33% cucumber juice, 8.33% pineapple juice and 25% kale juice.

3. The kale fruit and vegetable composite juice according to claim 1, characterized in that The preparation method of the apple juice comprises the following steps: washing the apples with clean water, manually peeling and core-removing the apples, crushing the apples with a high-speed machine to extract the juice, and filtering the juice through a 400-mesh filter.

4. The kale fruit and vegetable composite juice according to claim 1, characterized in that The preparation method of the celery juice comprises the following steps: removing the roots of the celery, washing the celery with clean water, crushing the celery with a high-speed machine to extract the juice, and filtering the juice through a 400-mesh filter.

5. The kale fruit and vegetable composite juice according to claim 1, characterized in that: The preparation method of the cucumber juice and pineapple juice is as follows: the cucumbers are washed with clean water and manually peeled and the head and tail are removed; the pineapples are washed, peeled, eyes and cored; the two are mixed and crushed in a mass ratio of 1:1, the juice is squeezed out using a high-speed crushing machine and filtered through a 400-mesh filter.

6. The kale fruit and vegetable composite juice according to claim 1, characterized in that: The preparation method of the kale juice is: a. Wash the kale, remove the old leaves, and take the fresh and tender leaves; b. Prepare an enzyme preparation at a ratio of 0.5wt‰ cellulase + 0.3wt‰ pectinase, with the enzyme preparation and leaf mass ratio being 1:100, and enzymatically hydrolyze the leaves in a constant temperature water bath at 40-50℃ for 5.5-6.5h; c. Immediately after enzymatic hydrolysis, freeze at -20℃ for 11-13 hours, then thaw at room temperature. After the leaves soften, use a high-speed crushing machine to extract the juice and filter twice through a 400-mesh filter.

7. A method for preparing the kale fruit-vegetable composite juice according to any one of claims 1 to 6, comprising the following steps: S1. Raw material pretreatment: After washing the kale, remove the old leaves and take the fresh leaves; prepare an enzyme preparation at a ratio of 0.5wt‰ cellulase + 0.3wt‰ pectinase, with an enzyme preparation to leaf mass ratio of 1:100, and enzymatically hydrolyze the leaves in a constant temperature water bath at 40-50°C for 5.5-6.5 hours; immediately after enzymatic hydrolysis, place them in a -20°C quick-freeze for 11-13 hours, then thaw at room temperature. After the leaves soften, use a high-speed crushing machine to extract the juice and filter it twice through a 400-mesh filter; wash the apples, peel and core them manually; remove the roots of the celery and wash them; peel and remove the head and tail of the cucumber; peel, remove the eyes and core of the pineapple, cut them into small pieces, crush them by machine to extract the juice, and filter them through a 400-mesh filter; S2. Mixing and blending: Mix the single fruit and vegetable juices by weight for 10-20 minutes until uniform; use a high-pressure microfluidizer to process the mixed fruit and vegetable juice and then fill it; S3 vacuum degassing: vacuum degassing of the fruit and vegetable juice filled in step S2; The vacuum degree is -0.05 to -0.08 MPa, and the time is 10-15 minutes; S4. Ultra-high pressure sterilization: ultra-high pressure sterilization of the fruit and vegetable compound juice after degassing in step S3, and the pressure is released immediately after sterilization; S5. Refrigeration: After sterilization in step S4, the fruit and vegetable composite juice product is obtained and stored in a cold storage.

8. The method for preparing kale fruit-vegetable composite juice according to claim 7, characterized in that: In the raw material pretreatment of step S1, the crushing mass ratio of cucumber and pineapple is 1:

1.

9. The method for preparing kale fruit-vegetable composite juice according to claim 7, characterized in that: The sterilization conditions of the ultrahigh pressure sterilization in step S4 are: first maintain the pressure at 400 MPa for 2-4 minutes, then increase the pressure to 500 MPa for 1-3 minutes, and finally increase the pressure to 600 MPa for 1-2 minutes. The sterilization temperature is controlled at 20-25°C.

10. The method for preparing kale fruit-vegetable composite juice according to claim 7, characterized in that: The refrigeration temperature in step S5 is 0-4°C.

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