Method for improving layering resistance stability of kale-apple compound fruit and vegetable juice

Abstract

The invention discloses a method for improving anti-layering stability of kale-apple compound fruit and vegetable juice, and belongs to the technical field of food processing. The method mainly comprises the following steps: (1) preparing collard normal juice and apple normal juice; (2) preparing a kale crude polysaccharide solution; (3) purifying the kale crude polysaccharide; (4) preparing normal juice of kale-apple composite fruit and vegetable juice; (5) adding kale polysaccharide; and (6) sterilizing and storing. Compared with kale-apple compound fruit and vegetable juice prepared in an untreated or single treatment mode, the kale-apple compound fruit and vegetable juice disclosed by the invention has the advantages that the layering phenomenon of the product in the storage period can be delayed by about 21 days under the condition of maintaining the sensory and nutritional quality of the product, and the quality improvement and the market competitiveness enhancement of the product are facilitated.

Description

Technical Field

[0001] The present invention belongs to the technical field of food processing, and particularly relates to a method for improving the anti-stratification stability of kale-apple composite fruit and vegetable juice. Background Art

[0002] In the modern food industry, with the enhancement of people's health awareness, non-concentrated fruit and vegetable juices with characteristics such as freshness, health, naturalness, and retention of the original flavor of fruits and vegetables have attracted much attention, leading to an increasing market share. As a new type of beverage that responds to consumers' health needs, kale-apple composite fruit and vegetable juice can not only provide various nutrients such as vitamins, minerals, and dietary fiber, but also bring a unique drinking experience. However, due to poor system stability, kale-apple composite fruit and vegetable juice is extremely prone to stratification during storage and sales. This not only affects the overall quality of the product, but also directly reduces its market competitiveness and consumer experience.

[0003] At present, the stratification phenomenon existing in fruit and vegetable juices has become a key factor restricting the development of the fruit and vegetable juice beverage processing industry and has attracted wide attention. During the processing of fruit and vegetable juices, fruit and vegetable cells are broken under the action of external forces, and then the intracellular substances overflow and form a multi-component mixed system. The main components affecting the stability of fruit and vegetable juices are some suspended substances and precipitation-sensitive substances, including fine pulp particles, fibers, polyphenols, proteins, pectins, and starches, etc., which specifically involve the sedimentation of insoluble substances and the generation of new polymers due to intermolecular interactions. In the prior art, the anti-stratification stability of fruit and vegetable juices is mostly improved from three aspects: inhibiting enzyme activity, increasing the viscosity of the juice, and reducing the density difference within the juice system.

[0004] Shanchun Hui et al. (2021) disclosed "A method for improving the stability of red date beverage" (Publication No.: CN112841464A). The stabilizers described in this invention are xanthan gum, sodium alginate, and sodium carboxymethylcellulose, which are added singly or in combination. After enzymatic hydrolysis with pectinase and then adding stabilizers to improve the stability of red date juice, the stability of red date juice is increased by 24.00%. Although during a storage period of up to 25 days, the sensory evaluation score of the experimental group with the best stability is higher than that of the control group, its total soluble solid content is significantly lower than that of the control group, which may mean a reduction in the original flavor and nutritional value of the juice. In addition, the concentration of additives used in this method is relatively high, which will lead to an increase in production costs.

[0005] Xu Jinsong (2019) disclosed "A preparation method of original flavor fruit and vegetable juice preventing color change, flavor change and precipitation" (Publication No.: CN 110122710A). During the processing of fruit and vegetable juice, it successively adopts steaming at 65 - 80 °C, colloid mill treatment, high-pressure homogenization at 15 - 35 Mpa and enzymatic hydrolysis treatment with a complex enzyme preparation under the condition of pH 3.5 - 5.5, which increases the suspension stability of fruit and vegetable pulp particles from two aspects of inactivating enzyme activity and reducing the density of pulp particles. However, during steaming, enzymatic hydrolysis and homogenization operations, the adverse effects of the heat generation effect that may be brought by processing conditions on the sensory properties of the finished product (especially green fruit and vegetable juice) should be fully considered, and this invention does not explain the exact object of action, the working parameters of the colloid mill and the high-pressure homogenizer, so it does not have sufficient industrial feasibility.

[0006] Xu Guanming et al. (2022) disclosed "A preparation method of a mixed fruit and vegetable juice beverage formula" (Publication No.: CN113907226A). This method adds 0.25 - 0.55 parts by weight of Eupatorium adenophorum extract to the compound fruit and vegetable juice prepared from fermented carrot pulp, citrus fruit juice and other components, so that the suspension stability of the examples reaches 100%, and the absolute value of the Zeta potential exceeds 29 mV. The fruit juices used in this invention are all reconstituted fruit juices, rather than freshly squeezed fruit juices, which is contrary to today's consumer concept of pursuing natural, additive-free and healthy. In addition, the preparation process of Eupatorium adenophorum extract involves the use of n-butanol, which not only improves the protection requirements during the processing, but also increases the exposure risk of consumers.

[0007] Zhang Cuncun et al. (2022) disclosed "A preparation method of a fruit juice beverage rich in polyphenols and saponins" (Application Publication No.: CN 113875920A). By using the embedding effect of the natural surfactant saponin in asparagus on polyphenols in the fruit juice, adding asparagus concentrate to the concentrated grape juice at an addition amount of 2% and undergoing high-pressure homogenization treatment, it not only reduces the loss of polyphenol substances during high-temperature treatment and storage, but also improves the stability of the compound thick slurry. However, the preparation raw materials are all concentrated juices. Compared with the original juice with lower viscosity, it cannot explain the effect of this method on reducing the occurrence of juice layering in the case of non-concentration. And this invention proposes a scheme of introducing a metal ion chelating agent into the system to improve the palatability of the asparagus concentrate, and still needs to specifically consider the sensory acceptability of the test group.

[0008] Wen Xin et al. (2022) published "A Method for Extracting Linseed Gum and the Resulting Linseed Gum Fruit Juice Beverage" (Publication No.: CN 115057947 A). Using pure fruit juice as the extractant, ultrasonic extraction was used to extract linseed gum from flax seeds, flax seed hulls, and flax seed meal, and a linseed gum fruit juice beverage was prepared. This method utilizes the natural colloid in flax seeds to significantly increase the viscosity of the original fruit juice. However, the results of the experimental group showed that clarified juice is more suitable as an extractant, while turbid juice would result in an overly thick taste. Moreover, the composition of fruit juice is far more complex than that of water, and these components may have a certain impact on the dissolution of linseed gum. In addition, the ultrasonic temperature and time used in the extraction process are relatively high and long, which may cause damage to the temperature-sensitive substances originally present in the fruit juice, and the high material-liquid ratio used in the extraction may lead to an increase in processing costs.

[0009] Xiao Yi et al. (2024) published "A Red-Fleshed Apple Juice Beverage and Its Preparation Method" (Publication No.: CN118216630A). This method proposed the potential of using water chestnut fruit extract to improve the overall quality of compound apple juice beverages. After ultrasonic extraction of the supernatant and precipitate of water chestnut fruit, ethanol and dilute acid were used to extract the supernatant and precipitate respectively. The two extracts were mixed to obtain water chestnut extract, and then added to the compound apple juice at 0.1% - 0.5% (mass ratio), which can not only prevent the browning of the fruit juice but also delay the occurrence of delamination. The results of the experimental group showed that the main factor improving the anti-delamination stability of the fruit juice is the precipitate extract of water chestnut fruit. However, the obtaining of this extract requires the use of a large amount of hydrochloric acid, and the safety of implementing this method still needs to be considered. In addition, the precipitation raw material described in this method is the unrefined coarse fruit residue, and although ultrasonic-assisted extraction is used, it is still possible that the effective substances cannot be completely extracted due to insufficient contact area.

[0010] Liu Guanchen et al. (2024) published "A Compound Fruit Juice Beverage of Wampee Medicinal and Edible Resources Based on a Self-Suspending Stable System of Dried Tangerine Peel and Its Preparation Method" (Publication No.: CN 118370362A). The self-suspending stable system described in this method is the dried tangerine peel extract, and the mass percentage of the dried tangerine peel ultrafine powder used to prepare each experimental group is 2% - 4%. The dried tangerine peel extract is obtained by water bath extraction. After mixing it with the compound fruit juice and passing through homogenization and sterilization, the finished product can be obtained. Although this method reduces the precipitation rate of the compound fruit juice beverage by more than 65% using the natural pectin in the self-suspending stable system, it does not clearly state the addition amount of the self-suspending stable system in each experimental group, increasing the difficulty of industrializing this method. In addition, only using water bath extraction may not be able to completely extract the pectin substances in the dried tangerine peel raw material, and this method does not purify the extract, which will not only increase the production cost, but the residual impurities in the extract may also have an adverse impact on the color and texture of the finished product. Summary of the Invention

[0011] In view of the deficiencies in the prior art, the present invention proposes a method that can significantly improve the anti-stratification stability of kale-apple composite fruit and vegetable juice. First, the cavitation effect and mechanical effect of ultrasonic treatment are utilized to optimize the uniformity of the composite fruit and vegetable juice, and then the thickening and gelling effects of natural polysaccharides in the kale juice residue are used to further enhance the physical stability of the kale-apple composite fruit and vegetable juice, effectively preventing the occurrence of stratification.

[0012] The technical solution of the present invention is as follows:

[0013] A method for improving the anti-stratification stability of kale-apple composite fruit and vegetable juice mainly includes the following steps:

[0014] (1) Preparation of kale original juice and apple original juice: After the fresh kale and fresh apples are screened and washed, they are respectively juiced and filtered through a 200-mesh gauze, and finally kale original juice, apple original juice and the juice residues of the two fruits and vegetables are obtained;

[0015] (2) Preparation of kale crude polysaccharide solution: The kale juice residue obtained in step (1) is dried at 55°C and sieved through a 60-120 mesh sieve to obtain kale dry powder; at room temperature, the kale dry powder is soaked in 95% ethanol three times for 120 minutes each time (kale dry powder: 95% ethanol = 1:5, w / v), and dried at 55°C to obtain the preliminarily defatted kale dry powder; subsequently, a water bath combined with ultrasonic treatment technology is used to extract soluble polysaccharides from the preliminarily defatted kale dry powder to obtain a kale crude polysaccharide solution;

[0016] (3) Purification of kale crude polysaccharide: The kale crude polysaccharide solution obtained in step (2) is filtered through a 200-mesh gauze, and then under the condition of pH 6.2, papain with an enzyme activity ≥ 2000 units / mg is added to the filtered crude polysaccharide solution, the papain: filtered crude polysaccharide solution = 0.1 mg: 1 mL, and the reaction is carried out in a 55°C water bath for 1.5 h, and then the papain is inactivated at 90°C to remove the protein in the crude polysaccharide solution to obtain a kale polysaccharide solution; the kale polysaccharide solution is centrifuged and the supernatant is collected, the supernatant collected after centrifugation is concentrated, and ethanol is added to the concentrated supernatant, the concentrated supernatant: ethanol = 1:3, v / v, and left to stand at 4°C for 24 h to fully precipitate the kale polysaccharide in the solution to form a kale polysaccharide suspension system; finally, the kale polysaccharide suspension system is filtered and freeze-dried to obtain purified kale polysaccharide;

[0017] (4) Preparation of the original juice of kale - apple compound fruit and vegetable juice: Mix the kale original juice and apple original juice obtained in step (1) evenly, and perform ultrasonic treatment to obtain the original juice of kale - apple compound fruit and vegetable juice;

[0018] (5) Addition of kale polysaccharide: Add the kale polysaccharide described in step (3) to the original juice of kale - apple compound fruit and vegetable juice obtained in step (4), mix evenly and set aside;

[0019] (6) Sterilization and storage: Perform heat sterilization, cooling and filling on the original juice of kale - apple compound fruit and vegetable juice added with kale polysaccharide obtained in step (5) to obtain the finished product of kale - apple compound fruit and vegetable juice.

[0020] Further, in step (2), the water bath is to mix the preliminarily de - impurities kale dry powder with distilled water at a material - to - liquid ratio of 1:5 - 20 g / mL, and first treat it in a water bath at 80 °C for 1 h; the ultrasonic treatment conditions are: treat for 1 h under the ultrasonic condition of 300 - 750 W.

[0021] Further, in step (3), the filtration is to filter the crude kale polysaccharide solution with a 200 - mesh gauze; the centrifugation is to centrifuge the polysaccharide solution after removing protein at 5000 r / min for 15 min, and collect the supernatant.

[0022] Further, in step (3), the concentration is to reduce the volume of the supernatant collected after centrifugation to 1 / 3 of the initial volume under the conditions of a vacuum degree of - 0.09 MPa and a temperature of 45 °C.

[0023] Further, in step (4), the mixing ratio of the kale original juice and apple original juice is 4:6 by mass.

[0024] Further, in step (4), the ultrasonic treatment conditions are: the ultrasonic power is 600 - 900 W, the treatment duration is 25 min, and the whole process is carried out under the constant temperature condition of 25 °C.

[0025] Further, in step (5), when adding the kale polysaccharide described in step (3) to the kale - apple compound fruit and vegetable juice prepared in step (4), the addition amount is 0.4% - 0.8% of the total mass of the compound fruit and vegetable juice.

[0026] Further, in step (6), the set temperature of the heat sterilization process is 85 °C, the treatment duration is 10 min; the filling temperature is 40 °C.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] (1) In the extraction method of kale polysaccharide proposed by the present invention, screening the kale dry powder with a high-mesh sieve can obtain raw material powder with high fineness, large specific surface area and good dispersibility, which helps to improve the dissolution effect of the extractant on soluble polysaccharides; using water bath combined with ultrasonic treatment to extract soluble polysaccharides can promote the full dissolution of polysaccharides in a stable heating environment, and the cavitation effect generated by ultrasonic treatment can rupture the cell structure, further accelerating the dissolution of polysaccharides, so that while significantly shortening the extraction time, the reaction proceeds more fully; using ethanol to preliminarily remove impurities from the kale dry powder can quickly remove pigments and fats in the raw materials under economic and environmental conditions, reduce the formation of by-products, and maintain the purity of polysaccharides; using enzymatic method to remove proteins in polysaccharides can achieve a high protein removal rate under safe and mild conditions, and reduce the degradation of polysaccharides induced by chemical reagents; using freeze-drying to dry kale polysaccharide can make the polysaccharide have good rehydration and nutritional value.

[0029] (2) The present invention proposes the addition of kale polysaccharide. By using the suspension and thickening effects of kale polysaccharide, without introducing exogenous stabilizers, the dispersion degree of solid particles and droplets in the compound fruit and vegetable juice is effectively increased, and the particle sedimentation caused by gravity is reduced, thus effectively improving the anti-stratification stability of kale-apple compound fruit and vegetable juice. Moreover, polysaccharide molecules can form a three-dimensional network structure in the solution, which can wrap and fix fruit and vegetable juice components such as fiber and pectin, delaying their sedimentation speed and further preventing the compound fruit and vegetable juice from stratifying. In addition, as a natural functional polysaccharide, kale polysaccharide has certain rheological properties and nutritional value. The addition of an appropriate amount of kale polysaccharide can not only endow the kale-apple compound fruit and vegetable juice with a more plump and smooth taste, but also provide additional nutritional supplements for the compound fruit and vegetable juice.

[0030] (3) The present invention proposes to perform ultrasonic treatment on the mixed system of kale original juice and apple original juice. By using the cavitation effect and mechanical effect of ultrasonic waves, the density difference caused by different components in the mixed system is reduced, thereby improving the homogeneity of kale-apple compound fruit and vegetable juice. At the same time, the addition of kale polysaccharide can play the role of a stabilizer, increasing the viscosity of the mixed system, and further enhancing the anti-stratification stability of kale-apple compound fruit and vegetable juice during storage. In addition, ultrasonic treatment has a significant inhibitory effect on the growth of microorganisms and can extend the shelf life of the product.

[0031] (4) The present invention promotes the healthy concept of "clean label", and focuses on the key sustainable development issue of "reusing agricultural product processing waste resources". From the perspectives of reducing additives, improving safety, and simplifying production processes, it utilizes the beneficial components in raw material waste and overcomes the production problems caused by the characteristics of raw materials. The proposal of this invention not only provides a solution for effectively improving the anti-stratification stability of kale-apple composite fruit and vegetable juice, but also provides strong technical support for the production of other composite fruit and vegetable juice products in the market (especially those rich in leafy vegetables and prone to stratification). Description of the Drawings

[0032] Figure 1 is the process flow chart of the production of kale-apple composite fruit and vegetable juice in the present invention;

[0033] Figure 2It is a comparison chart of the anti-stratification stability of the examples and comparative examples in the present invention. Among them, different lowercase letters indicate significant differences (P < 0.05) between the data of each example and the comparative example. In the comparison of the cloud stability of the compound fruit and vegetable juice, the letter corresponding to Example 2 is c, the letter corresponding to Example 3 is b, the letter corresponding to Example 4 is a, the letter corresponding to Example 5 is c, and the letters corresponding to Comparative Examples 1 to 3 are d, e, and f respectively; among the letters corresponding to Example 2 and Example 5, the letter "c" is the same, indicating that there is no significant difference between Example 2 and Example 5. There is no same part in the letters corresponding to Example 2 and Example 3, Example 4, Comparative Example 1, Comparative Example 2, and Comparative Example 3, indicating that there are significant differences between Example 2 and Example 3, Example 4, Comparative Example 1, Comparative Example 2, and Comparative Example 3. There is no same part in the letters corresponding to Example 5 and Example 3, Example 4, Comparative Example 1, Comparative Example 2, and Comparative Example 3, indicating that there are significant differences between Example 5 and Example 3, Example 4, Comparative Example 1, Comparative Example 2, and Comparative Example 3. In the comparison of the centrifugal sedimentation rate of the compound fruit and vegetable juice, the letter corresponding to Example 2 is d, the letter corresponding to Example 3 is de, the letter corresponding to Example 4 is e, the letter corresponding to Example 5 is cd, and the letters corresponding to Comparative Examples 1 to 3 are c, b, and a respectively; among the letters corresponding to Example 3 and Example 2, the letter "d" is the same, indicating that there is no significant difference between Example 3 and Example 2; among the letters corresponding to Example 3 and Example 4, the letter "e" is the same, indicating that there is no significant difference between Example 3 and Example 4; among the letters corresponding to Example 3 and Example 5, the letter "d" is the same, indicating that there is no significant difference between Example 3 and Example 5; there is no same part in the letters corresponding to Example 3 and Comparative Examples 1 to 3, indicating that there are significant differences between Example 3 and the comparative examples; among the letters corresponding to Example 5 and Example 2, the letter "d" is the same, indicating that there is no significant difference between Example 5 and Example 2, and among the letters corresponding to Example 5 and Comparative Example 1, the letter "c" is the same, indicating that there is no significant difference between Example 5 and Comparative Example 1; there is no same part in the letters corresponding to Example 2 and Example 4, Comparative Example 1, Comparative Example 2, and Comparative Example 3, indicating that there are significant differences between Example 2 and Example 4, Comparative Example 1, Comparative Example 2, and Comparative Example 3; there is no same part in the letters corresponding to Example 3 and Comparative Examples 1, Comparative Example 2, and Comparative Example 3, indicating that there are significant differences between Example 3 and Comparative Examples 1, Comparative Example 2, and Comparative Example 3. There is no same part in the letters corresponding to Example 4 and Example 5, Comparative Example 2, and Comparative Example 3, indicating that there are significant differences between Example 4 and Example 5, Comparative Example 2, and Comparative Example 3.

[0034] Figure 3It is a comparison chart of the antioxidant capacities of the examples and comparative examples in the present invention. Among them, different lowercase letters indicate significant differences in the data between each example and the comparative example (P < 0.05). Figure 3 The principle of the letter explanation is the same as that of Figure 2 Therefore, by the same token, in the comparison of the DPPH free radical scavenging ability of the compound fruit and vegetable juice, there is no significant difference between Example 2 and Example 5, no significant difference between Example 3 and Example 4, and no significant difference between Example 5 and Comparative Example 1; there are significant differences between Example 2, Example 3, Comparative Example 2 and Comparative Example 3, between Example 2, Example 4, Comparative Example 1, Comparative Example 2 and Comparative Example 3, between Example 3, Example 5, Comparative Example 2 and Comparative Example 3, and between Example 4, Example 5, Comparative Example 2 and Comparative Example 3. In the comparison of the ABTS free radical scavenging ability of the compound fruit and vegetable juice, there is no significant difference between Example 2 and Example 5, no significant difference between Example 3 and Comparative Example 1, no significant difference between Example 4 and Comparative Example 2, and no significant difference between Example 4 and Comparative Example 1; there are significant differences between Example 2, Example 3, Example 4 and Comparative Example 3, between Example 2, Example 3, Comparative Example 2 and Comparative Example 3, between Example 3, Example 4, Example 5 and Comparative Example 3, and between Example 3, Example 5, Comparative Example 2 and Comparative Example 3. Specific embodiments

[0035] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the following will further illustrate the present invention in conjunction with examples, but not to limit the present invention.

[0036] Example 1

[0037] In the extraction experiment part of kale polysaccharide, mainly explore the three parts of the optimal screening mesh number, the optimal solid-liquid ratio and the optimal ultrasonic power, including the following content:

[0038] Example 1.1

[0039] Explore the influence of the screening mesh number on the yield of kale polysaccharide, including the following steps:

[0040] (1) Preparation of crude kale polysaccharide solution

[0041] After drying the kale juice residues obtained from squeezing kale raw juice at 55°C, the low-temperature dried kale dry powder was sieved through 60-mesh, 80-mesh, 100-mesh, and 120-mesh sieves respectively; at room temperature, the kale dry powder was pretreated by soaking with 95% ethanol three times for 120 minutes each time (kale dry powder: 95% ethanol = 1:5, w / v), and then dried at 55°C to obtain the kale dry powder after preliminary impurity removal; the kale dry powder after preliminary impurity removal was mixed with distilled water at a solid-liquid ratio of 1:20 g / mL, and treated in a water bath at 80°C for 1 h and ultrasonic treated at 450 W for 1 h to extract soluble polysaccharides from the kale dry powder, obtaining a crude kale polysaccharide solution.

[0042] (2) Purification of crude kale polysaccharide

[0043] Purification of crude kale polysaccharide: The crude kale polysaccharide solution obtained in step (1) was filtered through a 200-mesh gauze, and then, under the condition of pH 6.2, papain (≥2000 units / mg) was added to the filtered crude polysaccharide solution at a solid-liquid ratio of 0.1 mg / mL, and reacted in a water bath at 55°C for 1.5 h, and then the papain was inactivated at 90°C to remove the protein in the crude polysaccharide solution, obtaining a kale polysaccharide solution; after centrifuging the kale polysaccharide solution and collecting the supernatant, the collected supernatant after centrifugation was concentrated, and ethanol was added to the concentrated kale polysaccharide solution (kale polysaccharide solution: ethanol = 1:3, v / v), and allowed to stand at 4°C for 24 h to fully precipitate the kale polysaccharide in the solution, forming a kale polysaccharide suspension system; finally, the kale polysaccharide suspension system was filtered by suction and freeze-dried to obtain kale polysaccharide. Calculate the yield of kale polysaccharide, and comprehensively compare to select the best screening mesh number.

[0044] Table 1 Effect of screening mesh number on the yield of kale polysaccharide

[0045] Screening mesh number 60 mesh 80 mesh 100 mesh 120 mesh Yield of kale polysaccharide / % <![CDATA[8.52±0.13 c > <![CDATA[9.11±0.17 b > <![CDATA[9.86±0.09 a > <![CDATA[9.78±0.12 a >

[0046] Through the above experiments, the best screening mesh number was determined to be 100 mesh.

[0047] Example 1.2

[0048] To explore the effect of the solid-liquid ratio on the yield of kale polysaccharide, the following steps are included:

[0049] (1) Preparation of crude kale polysaccharide solution

[0050] After drying the kale juice residue obtained by squeezing kale raw juice at 55 °C, the low-temperature dried kale dry powder was sieved through a 100-mesh sieve; at room temperature, the kale dry powder was pretreated by soaking with 95% ethanol three times for 120 min each time (kale dry powder: 95% ethanol = 1:5, w / v), and dried at 55 °C to obtain the kale dry powder after preliminary impurity removal; the kale dry powder after preliminary impurity removal was mixed with distilled water at a solid-liquid ratio of 1:5, 1:10, 1:15, and 1:20 g / mL, respectively, and treated in a water bath at 80 °C for 1 h and ultrasonic treated at 450 W for 1 h to extract soluble polysaccharides from the kale dry powder to obtain a crude kale polysaccharide solution;

[0051] (2) Purification of crude kale polysaccharide

[0052] Purification of crude kale polysaccharide: The crude kale polysaccharide solution obtained in step (1) was filtered through a 200-mesh gauze, and then, under the condition of pH 6.2, papain (≥2000 units / mg) was added to the filtered crude polysaccharide solution at a solid-liquid ratio of 0.1 mg / mL, and reacted in a water bath at 55 °C for 1.5 h, and then papain was inactivated at 90 °C to remove proteins in the crude polysaccharide solution to obtain a kale polysaccharide solution; after centrifuging the kale polysaccharide solution and collecting the supernatant, the supernatant collected after centrifugation was concentrated, and ethanol was added to the concentrated kale polysaccharide solution (kale polysaccharide solution: ethanol = 1:3, v / v), and allowed to stand at 4 °C for 24 h to fully precipitate the kale polysaccharide in the solution to form a kale polysaccharide suspension system; finally, the kale polysaccharide suspension system was filtered by suction and freeze-dried to obtain kale polysaccharide. Calculate the yield of kale polysaccharide and comprehensively compare to select the optimal solid-liquid ratio.

[0053] Table 2 Effect of solid-liquid ratio on the yield of kale polysaccharide

[0054] Ratio of material to liquid / (g / ml) 1:5 1:10 1:15 1:20 Yield of kale polysaccharide / % <![CDATA[6.66±0.14 d > <![CDATA[7.43±0.05 c > <![CDATA[8.64±0.10 b > <![CDATA[9.86±0.08 a >

[0055] Through the above experiments, the optimal solid-liquid ratio was determined to be 1:20 g / ml.

[0056] Example 1.3

[0057] To explore the effect of ultrasonic power on the yield of kale polysaccharide, the following steps are included:

[0058] (1) Preparation of crude kale polysaccharide solution

[0059] After drying the kale juice residue obtained by extracting the original kale juice at 55°C, the dried kale powder after low-temperature drying is sieved through a 100-mesh sieve; at room temperature, the dried kale powder is pretreated by soaking with 95% ethanol three times for 120 minutes each time (dried kale powder: 95% ethanol = 1:5, w / v), and then dried at 55°C to obtain the preliminarily impurity-removed dried kale powder; the preliminarily impurity-removed dried kale powder is mixed with distilled water at a solid-liquid ratio of 1:20 g / mL, and after being treated in a water bath at 80°C for 1 h, ultrasonic treatments are carried out at 300 W, 450 W, 600 W, and 750 W for 1 h respectively to extract soluble polysaccharides from the dried kale powder, obtaining a crude kale polysaccharide solution;

[0060] (2) Purification of crude kale polysaccharide

[0061] Purification of crude kale polysaccharide: The crude kale polysaccharide solution obtained in step (1) is filtered through a 200-mesh gauze, and then under the condition of pH 6.2, papain (≥2000 units / mg) is added to the filtered crude polysaccharide solution at a solid-liquid ratio of 0.1 mg / mL, and the reaction is carried out in a water bath at 55°C for 1.5 h, and then the papain is inactivated at 90°C to remove the protein in the crude polysaccharide solution, obtaining a kale polysaccharide solution; after centrifuging the kale polysaccharide solution and collecting the supernatant, the collected supernatant after centrifugation is concentrated, and ethanol is added to the concentrated kale polysaccharide solution (kale polysaccharide solution: ethanol = 1:3, v / v), and it is left to stand at 4°C for 24 h to fully precipitate the kale polysaccharide in the solution, forming a kale polysaccharide suspension system; finally, the kale polysaccharide suspension system is filtered by suction and freeze-dried to obtain kale polysaccharide. Calculate the yield of kale polysaccharide, and comprehensively compare to select the optimal ultrasonic power.

[0062] Table 3 Effect of ultrasonic intensity on the yield of kale polysaccharide

[0063] Ultrasonic intensity 300W 450W 600W 750W Yield of kale polysaccharide / % <![CDATA[8.77±0.10 d > <![CDATA[9.86±0.08 c > <![CDATA[11.17±0.10 a > <![CDATA[10.75±0.16 b >

[0064] Through the above experiments, the optimal ultrasonic power is determined to be 600 W.

[0065] Example 2

[0066] A method for improving the anti-stratification stability of kale-apple compound fruit and vegetable juice, comprising the following steps:

[0067] (1) Preparation of original kale juice and original apple juice: After screening and washing fresh kale and fresh apples, they are respectively juiced and filtered, and finally the original kale juice, original apple juice and the juice residues of the two fruits and vegetables are obtained;

[0068] (2) Preparation of kale crude polysaccharide solution:

[0069] After drying the kale juice residue obtained by squeezing the original kale juice at 55 °C, the dried kale powder is sieved through a 100-mesh sieve; at room temperature, the kale powder is pretreated by soaking with 95% ethanol three times for 120 min each time (kale powder: 95% ethanol = 1:5, w / v), and then dried at 55 °C to obtain the preliminarily decontaminated kale powder; the preliminarily decontaminated kale powder is mixed with distilled water at a solid-liquid ratio of 1:20 g / mL, and soluble polysaccharides are extracted from the kale powder by water bath treatment at 80 °C for 1 h and ultrasonic treatment at 600 W for 1 h to obtain the kale crude polysaccharide solution;

[0070] (3) Purification of kale crude polysaccharide:

[0071] Purification of kale crude polysaccharide: The kale crude polysaccharide solution obtained in step (2) is filtered through a 200-mesh gauze, and then, under the condition of pH 6.2, papain (≥2000 units / mg) is added to the filtered crude polysaccharide solution at a solid-liquid ratio of 0.1 mg / mL, and the reaction is carried out in a water bath at 55 °C for 1.5 h, and then papain is inactivated at 90 °C to remove the protein in the crude polysaccharide solution, obtaining the kale polysaccharide solution; after the kale polysaccharide solution is centrifuged and the supernatant is collected, the collected supernatant after centrifugation is concentrated, and ethanol is added to the concentrated kale polysaccharide solution (kale polysaccharide solution: ethanol = 1:3, v / v), and it is left standing at 4 °C for 24 h to fully precipitate the kale polysaccharide in the solution, forming a kale polysaccharide suspension system; finally, the kale polysaccharide suspension system is filtered by suction and freeze-dried to obtain kale polysaccharide;

[0072] (4) Mixing and ultrasonic treatment of kale original juice and apple original juice: The kale original juice and apple original juice obtained in step (1) are mixed evenly at a volume ratio of 4:6, and then ultrasonic treatment is carried out at 25 °C and an ultrasonic power of 900 W for 25 min to obtain the kale-apple composite fruit and vegetable juice original juice;

[0073] (5) Addition of kale polysaccharide: The kale polysaccharide described in step (3) is added to the kale-apple composite fruit and vegetable juice original juice obtained in step (4) at a mass ratio of 0.4%, and after mixing evenly, it is reserved for use;

[0074] (6) Sterilization and storage: The kale-apple composite fruit and vegetable juice added with kale polysaccharide obtained in step (5) is treated at 85 °C for 10 min, and after it is cooled to 40 °C, it is filled into a sterile bottle to obtain the finished product of the kale-apple composite fruit and vegetable juice.

[0075] Example 3

[0076] A method for improving the anti - stratification stability of kale - apple compound fruit and vegetable juice, comprising the following steps:

[0077] (1) Preparation of kale original juice and apple original juice: After screening and washing fresh kale and fresh apples, they are respectively juiced and filtered, and finally kale original juice, apple original juice and the juice residues of the two fruits and vegetables are obtained;

[0078] (2) Preparation of crude kale polysaccharide solution:

[0079] The kale juice residues obtained by squeezing kale original juice are dried at 55°C, and then the low - temperature dried kale dry powder is sieved through a 100 - mesh sieve; at room temperature, the kale dry powder is pretreated by soaking in 95% ethanol three times for 120 min each time (kale dry powder: 95% ethanol = 1:5, w / v), and then dried at 55°C to obtain the preliminarily defatted kale dry powder; the preliminarily defatted kale dry powder is mixed with distilled water at a solid - liquid ratio of 1:20 g / mL, and soluble polysaccharides are extracted from the kale dry powder by water - bath treatment at 80°C for 1 h and ultrasonic treatment at 600 W for 1 h to obtain a crude kale polysaccharide solution;

[0080] (3) Purification of crude kale polysaccharide:

[0081] Purification of crude kale polysaccharide: The crude kale polysaccharide solution obtained in step (2) is filtered through a 200 - mesh gauze, and then under the condition of pH 6.2, papain (≥2000 units / mg) is added to the filtered crude polysaccharide solution at a solid - liquid ratio of 0.1 mg / mL, and the reaction is carried out in a water - bath at 55°C for 1.5 h, and then papain is inactivated at 90°C to remove proteins in the crude polysaccharide solution, obtaining a kale polysaccharide solution; after the kale polysaccharide solution is centrifuged and the supernatant is collected, the collected supernatant after centrifugation is concentrated, and ethanol is added to the concentrated kale polysaccharide solution (kale polysaccharide solution: ethanol = 1:3, v / v), and it is left to stand at 4°C for 24 h to fully precipitate the kale polysaccharide in the solution, forming a kale polysaccharide suspension system; finally, the kale polysaccharide suspension system is filtered by suction and freeze - dried to obtain kale polysaccharide;

[0082] (4) Mixing and ultrasonic treatment of kale original juice and apple original juice: The kale original juice and apple original juice obtained in step (1) are mixed evenly at a volume ratio of 4:6, and then ultrasonic treatment is carried out at 25°C and an ultrasonic power of 900 W for 25 min to obtain the original juice of kale - apple compound fruit and vegetable juice;

[0083] (5) Addition of kale polysaccharide: Add the kale polysaccharide described in step (3) to the original kale-apple compound fruit and vegetable juice obtained in step (4) at a mass ratio of 0.6%, mix evenly and set aside;

[0084] (6) Sterilization and storage: Treat the kale-apple compound fruit and vegetable juice added with kale polysaccharide obtained in step (5) at 85 °C for 10 min, and after it cools to 40 °C, fill it into a sterile bottle to obtain the finished kale-apple compound fruit and vegetable juice.

[0085] Example 4

[0086] A method for improving the anti-stratification stability of kale-apple compound fruit and vegetable juice, comprising the following steps:

[0087] (1) Preparation of original kale juice and original apple juice: After screening and washing fresh kale and fresh apples, they are respectively juiced and filtered to finally obtain original kale juice, original apple juice and the juice residues of the two fruits and vegetables;

[0088] (2) Preparation of crude kale polysaccharide solution:

[0089] The kale juice residues obtained by squeezing original kale juice are dried at 55 °C, and then the low-temperature dried kale dry powder is sieved through a 100-mesh sieve; at room temperature, the kale dry powder is pretreated by soaking in 95% ethanol for 3 times, 120 min each time (kale dry powder: 95% ethanol = 1:5, w / v), and dried at 55 °C to obtain the preliminarily defatted kale dry powder; the preliminarily defatted kale dry powder is mixed with distilled water at a solid-liquid ratio of 1:20 g / mL, and soluble polysaccharides are extracted from the kale dry powder by water bath treatment at 80 °C for 1 h and ultrasonic treatment at 600 W for 1 h to obtain a crude kale polysaccharide solution;

[0090] (3) Purification of crude kale polysaccharide:

[0091] Purification of kale crude polysaccharide: The kale crude polysaccharide solution obtained in step (2) is filtered through a 200-mesh gauze, and then, under the condition of pH 6.2, papain (≥2000 units / mg) is added to the filtered crude polysaccharide solution at a material-liquid ratio of 0.1 mg / mL. After reacting in a water bath at 55°C for 1.5 h, the papain is inactivated at 90°C to remove the protein in the crude polysaccharide solution, obtaining a kale polysaccharide solution. After centrifuging the kale polysaccharide solution and collecting the supernatant, the collected supernatant after centrifugation is concentrated, and ethanol (kale polysaccharide solution:ethanol = 1:3, v / v) is added to the concentrated kale polysaccharide solution. It is left to stand at 4°C for 24 h to fully precipitate the kale polysaccharide in the solution, forming a kale polysaccharide suspension system. Finally, the kale polysaccharide suspension system is subjected to suction filtration and freeze-drying to obtain kale polysaccharide;

[0092] (4) Mixing and ultrasonic treatment of kale original juice and apple original juice: The kale original juice and apple original juice obtained in step (1) are mixed evenly at a volume ratio of 4:6, and then ultrasonic treatment is carried out at 25°C and an ultrasonic power of 900 W for 25 min to obtain a kale-apple compound fruit and vegetable juice original juice;

[0093] (5) Addition of kale polysaccharide: The kale polysaccharide described in step (3) is added to the kale-apple compound fruit and vegetable juice original juice obtained in step (4) at a mass ratio of 0.8%, and after mixing evenly, it is reserved for use;

[0094] (6) Sterilization and storage: The kale-apple compound fruit and vegetable juice added with kale polysaccharide obtained in step (5) is treated at 85°C for 10 min. After it is cooled to 40°C, it is filled into a sterile bottle to obtain the finished kale-apple compound fruit and vegetable juice.

[0095] Example 5

[0096] A method for improving the anti-stratification stability of kale-apple compound fruit and vegetable juice, comprising the following steps:

[0097] (1) Preparation of kale original juice and apple original juice: After the fresh kale and fresh apples are screened and cleaned, they are respectively juiced and filtered, and finally kale original juice, apple original juice and the juice residues of the two fruits and vegetables are obtained;

[0098] (2) Preparation of kale crude polysaccharide solution:

[0099] After drying the kale juice residues obtained from squeezing fresh kale juice at 55°C, the low-temperature dried kale powder was sieved through a 100-mesh sieve; at room temperature, the kale powder was pretreated by soaking in 95% ethanol three times for 120 minutes each time (kale powder: 95% ethanol = 1:5, w / v), and then dried at 55°C to obtain the preliminarily impurity-removed kale powder; the preliminarily impurity-removed kale powder was mixed with distilled water at a solid-to-liquid ratio of 1:20 g / mL, and soluble polysaccharides were extracted from the kale powder by water bath treatment at 80°C for 1 h and ultrasonic treatment at 600 W for 1 h to obtain a crude kale polysaccharide solution;

[0100] (3) Purification of crude kale polysaccharide:

[0101] Purification of crude kale polysaccharide: The crude kale polysaccharide solution obtained in step (2) was filtered through a 200-mesh gauze, and then, under the condition of pH 6.2, papain (≥2000 units / mg) was added to the filtered crude polysaccharide solution at a solid-to-liquid ratio of 0.1 mg / mL, and the reaction was carried out in a water bath at 55°C for 1.5 h. Then, papain was inactivated at 90°C to remove proteins in the crude polysaccharide solution, obtaining a kale polysaccharide solution; after centrifuging the kale polysaccharide solution and collecting the supernatant, the collected supernatant after centrifugation was concentrated, and ethanol was added to the concentrated kale polysaccharide solution (kale polysaccharide solution: ethanol = 1:3, v / v), and it was left standing at 4°C for 24 h to fully precipitate the kale polysaccharide in the solution, forming a kale polysaccharide suspension system; finally, the kale polysaccharide suspension system was filtered by suction and freeze-dried to obtain kale polysaccharide;

[0102] (4) Mixing and ultrasonic treatment of fresh kale juice and fresh apple juice: The fresh kale juice and fresh apple juice obtained in step (1) were mixed evenly at a volume ratio of 4:6, and then ultrasonic treatment was carried out at 25°C and an ultrasonic power of 600 W for 25 min to obtain a fresh kale-apple composite fruit and vegetable juice;

[0103] (5) Addition of kale polysaccharide: The kale polysaccharide described in step (3) was added to the fresh kale-apple composite fruit and vegetable juice obtained in step (4) at a mass ratio of 0.6%, and after mixing evenly, it was reserved for use;

[0104] (6) Sterilization and storage: The kale-apple composite fruit and vegetable juice added with kale polysaccharide obtained in step (5) was treated at 85°C for 10 min. After it was cooled to 40°C, it was filled into a sterile bottle to obtain the finished product of the kale-apple composite fruit and vegetable juice.

[0105] Comparative Example 1

[0106] Operate according to the method of Example 3, except that the ultrasonic treatment of kale original juice and apple original juice in Example 2 is omitted, and finally a kale-apple compound fruit and vegetable juice containing only kale polysaccharide is obtained.

[0107] Comparative Example 2

[0108] Operate according to the method of Example 3, except that the addition of kale polysaccharide in Example 2 is omitted, and finally a kale-apple compound fruit and vegetable juice treated only by ultrasonic treatment is obtained.

[0109] Comparative Example 3

[0110] Operate according to the method of Example 3, except that the ultrasonic treatment of kale original juice and apple original juice and the addition of kale polysaccharide in Example 2 are omitted, and finally a kale-apple compound fruit and vegetable juice without ultrasonic treatment and addition of kale polysaccharide is obtained.

[0111] Test Example 1

[0112] Anti-stratification stability test of kale-apple compound fruit and vegetable juice

[0113] 1. Cloud stability: Take the kale-apple compound fruit and vegetable juices prepared in the examples and comparative examples as solution samples. Take 30 ml of each solution sample and centrifuge at 4 °C and 8000 r / min for 10 min, and measure the absorbance value of the supernatant at 660 nm using an ultraviolet spectrophotometer. At the same time, measure the absorbance value of each sample before centrifugation at the same wavelength. The cloud stability of the sample is calculated using formula (1), where A a is the absorbance before centrifugation of the sample, and A b is the absorbance after centrifugation of the sample.

[0114]

[0115] 2. Centrifugal sedimentation rate: Take the kale-apple compound fruit and vegetable juices prepared in the examples and comparative examples as solution samples. Take 30 ml of each solution sample and centrifuge at 25 °C and 8000 r / min for 10 min. Discard the supernatant and wash the obtained precipitate twice with distilled water; then centrifuge the washing solution at 25 °C and 10000 r / min for 10 min. Finally, dry the washed precipitate at 55 °C to constant weight. The centrifugal sedimentation rate is calculated using formula (2), where m a , m b and m c are the mass of the centrifuge tube, the mass of the centrifuge tube after loading the sample, and the mass of the centrifuge tube and the precipitate after drying, respectively.

[0116]

[0117] 3. Zeta potential: The kale-apple compound fruit and vegetable juice prepared in the examples and comparative examples was used as a solution sample. 1 ml of the static sample was taken and diluted 15 times, and then the Zeta potential of the solution sample was measured using a Zeta potential meter.

[0118] 4. Storage stability: The kale-apple compound fruit and vegetable juice prepared in the examples and comparative examples was used as a sample, which was stored in the dark at 4 °C for 21 days, and samples were taken regularly for observation.

[0119] Table 4 Test results of the anti-stratification stability of kale-apple compound fruit and vegetable juice in examples and comparative examples

[0120] Experimental group Cloud stability (%) Centrifugal sedimentation rate (%) Zeta potential (mV) Stratification situation Example 2 <![CDATA[60.22±1.07 c > <![CDATA[0.20±0.01 d > <![CDATA[-10.78±0.50 de > Stratification occurred after 7 days Example 3 <![CDATA[67.93±1.12 b > <![CDATA[0.18±0.02 de > <![CDATA[-11.20±0.21 e > No stratification Example 4 <![CDATA[76.31±1.40 a > <![CDATA[0.16±0.02 e > <![CDATA[-11.75±0.21 f > No stratification Example 5 <![CDATA[61.57±0.61 c > <![CDATA[0.21±0.03 cd > <![CDATA[-10.48±0.21 d > No stratification Comparative example 1 <![CDATA[44.38±0.80 d > <![CDATA[0.24±0.02 c > <![CDATA[-8.46±0.26 c > Stratification occurred after 10 days Comparative example 2 <![CDATA[28.73±0.78 e > <![CDATA[0.28±0.01 b > <![CDATA[-3.89±0.15 a > Stratification occurred after 1 day Comparative example 3 <![CDATA[21.37±0.83 f > <![CDATA[0.32±0.03 a > <![CDATA[-5.75±0.14 b > Stratification occurred after 1 day

[0121] In the verification experiment of the synergistic effect of ultrasonic treatment and the addition of kale polysaccharide, the cloud stability, centrifugal sedimentation rate and Zeta potential of Example 3 (ultrasonic treatment combined with the addition of kale polysaccharide), Comparative Example 1 (with the same steps as Example 3, only adding kale polysaccharide), Comparative Example 2 (with the same steps as Example 3, only performing ultrasonic treatment) and Comparative Example 3 (with the same steps as Example 3, but without ultrasonic treatment and the addition of kale polysaccharide) were measured 1 day after sample preparation. The test results are shown in Table 4. Both the ultrasonic treatment alone or the addition of kale can enhance the anti-stratification stability of kale-apple compound fruit and vegetable juice, and the enhancing effect of kale polysaccharide is better than that of ultrasonic treatment. However, when ultrasonic treatment and the addition of kale polysaccharide are applied simultaneously in the processing of kale-apple compound fruit and vegetable juice, compared with the comparative examples using only ultrasonic treatment or the addition of kale, the combined treatment improved the cloud stability (53.06 - 136.44%) and the absolute value of Zeta potential (32.39 - 187.92%) of the compound fruit and vegetable juice, reduced its centrifugal sedimentation rate (25.00 - 35.71%), and showed more excellent anti-stratification stability during the 21-day storage period.

[0122] By comparing the anti-stratification stability of Example 2 (the addition amount of kale polysaccharide is 0.4%), Example 3 (with the same steps as Example 2, the addition amount of kale polysaccharide is 0.6%) and Example 4 (with the same steps as Example 2, the addition amount of kale polysaccharide is 0.8%), it can be found that under the condition of constant ultrasonic intensity, the anti-stratification stability of the compound fruit and vegetable juice is positively correlated with the addition amount of kale polysaccharide. At the same time, by comparing the anti-stratification stability of Example 3 (ultrasonic treatment power is 900 W) and Example 5 (with the same steps as Example 3, ultrasonic treatment power is 600 W), it can be found that under the condition of adding the same concentration of kale polysaccharide, with the increase of ultrasonic intensity, the stratification phenomenon of the compound fruit and vegetable juice during storage was significantly delayed.

[0123] Test Example 2

[0124] Antioxidant Capacity Test of Kale-Apple Composite Fruit and Vegetable Juice

[0125] 1. DPPH Radical Scavenging Capacity: Take the kale-apple composite fruit and vegetable juice prepared in the examples and comparative examples as the solution sample. Take 0.1 ml of the sample supernatant after centrifuging at 8000 r / min for 10 min at 4 °C and diluting 10 times, and mix it with 0.1 ml of 0.5 mM DPPH solution. After incubating at room temperature for 30 min, use a microplate reader to measure the absorbance value at 517 nm. The DPPH radical scavenging capacity of the sample is calculated using formula (3). In the formula, where A x represents the absorbance after mixing the test solution and the DPPH solution, and A DPPH represents the absorbance of the solution without adding the test solution.

[0126]

[0127] 2. ABTS Radical Scavenging Capacity: Take the kale-apple composite fruit and vegetable juice prepared in the examples and comparative examples as the solution sample. Take 50 μl of the sample supernatant after centrifuging at 8000 r / min for 10 min at 4 °C and diluting 800 times, and mix it with 200 μl of ABTS reaction solution (the absorbance at 734 nm is 0.7 ± 0.002). After incubating at room temperature for 15 min, use a microplate reader to measure the absorbance value at 734 nm. The ABTS radical scavenging capacity is calculated using formula (5). Among them, A x represents the absorbance after mixing the test solution and the ABTS solution, and A ABTS represents the absorbance of the solution without adding the test solution.

[0128]

[0129] Figure 3 The test results are for the antioxidant capacity of the kale-apple composite fruit and vegetable juice prepared in the examples and comparative examples. By comparing the radical scavenging capacities of Example 3 (ultrasonic-assisted kale polysaccharide addition treatment example), Comparative Example 1 (the same steps as Example 3, only adding kale polysaccharide), Comparative Example 2 (the same steps as Example 3, only performing ultrasonic treatment), and Comparative Example 3 (the same steps as Example 3, but without ultrasonic treatment and kale polysaccharide addition), it can be found that whether used alone or in combination, ultrasonic treatment and kale polysaccharide addition both cause a certain degree of reduction in the antioxidant capacity of the composite fruit and vegetable juice. This may be attributed to the loss of antioxidant components (such as vitamin C, polyphenols, etc.) caused by physical and chemical reactions (such as oxidation reactions, interactions between components) in the mixed system after the two treatments.

[0130] However, by comparing the free radical scavenging ability of Example 3 (ultrasonic intensity 900 W) and Example 5 (with the same steps as Example 3, ultrasonic power 600 W), it can be found that when the addition amount of kale polysaccharide is the same, the weaker the ultrasonic intensity, the higher the antioxidant ability of the composite fruit and vegetable juice. This result indicates that while effectively suppressing the delamination phenomenon of kale-apple composite fruit and vegetable juice, the ultrasonic intensity can be reduced to maintain a relatively high antioxidant ability of the composite fruit and vegetable juice.

[0131] Test Example 3

[0132] Sensory quality test of kale-apple composite fruit and vegetable juice

[0133] The kale-apple composite fruit and vegetable juice prepared in the examples and comparative examples was stored in the dark at 4 °C for 21 days, and samples were taken regularly for sensory evaluation. Ten professional sensory evaluation personnel (5 males and 5 females) were invited to conduct sensory evaluation on the kale-apple composite fruit and vegetable juice, and the specific sensory evaluation criteria are shown in Table 5.

[0134] Table 5 Sensory evaluation criteria

[0135]

[0136] Table 6 Sensory evaluation results of kale-apple composite fruit and vegetable juice in examples and comparative examples

[0137] Experimental group Stored at 4°C for 0 days Stored at 4°C for 7 days Stored at 4°C for 14 days Stored at 4°C for 21 days Example 2 95 80 75 68 Example 3 95 86 79 73 Example 4 95 85 77 72 Example 5 95 85 77 67 Comparative example 1 94 80 68 62 Comparative example 2 82 70 60 55 Comparative example 3 81 69 60 54

[0138] Table 6 shows the sensory evaluation results of the kale-apple composite fruit and vegetable juice prepared in the examples and comparative examples during storage. From the data in Table 6, it can be seen that the sensory quality of the composite fruit and vegetable juice prepared in each experimental group decreased with the extension of storage time. Among them, the sensory scores of the composite fruit and vegetable juice prepared by ultrasonic treatment-assisted addition of kale polysaccharide were higher than those of the untreated group or the group treated only with a single method, and the increase in kale polysaccharide significantly slowed down the deterioration trend of the sensory quality of the composite fruit and vegetable juice during storage.

[0139] The above examples are only experimental illustrations of the technical solutions of the present invention and do not limit it; although the present invention has been described in detail with reference to the above examples, those of ordinary skill in the art should understand that they can adjust and improve the technical solutions, including but not limited to modifying individual technical elements or adopting functionally equivalent alternative solutions; and these modifications or substitutions should be included within the scope of the claims of the present invention.

Claims

1. A method for improving the anti-stratification stability of kale-apple compound fruit and vegetable juice, characterized in that, It mainly includes the following steps: (1) Preparation of kale original juice and apple original juice: After screening and washing fresh kale and fresh apples, they are respectively juiced and filtered through a 200-mesh gauze to obtain kale original juice, apple original juice and the residue of the two kinds of fruits and vegetables after juicing; (2) Preparation of crude kale polysaccharide solution: The kale residue obtained in step (1) is dried at 55°C and sieved through a 60-120 mesh sieve to obtain kale dry powder; at room temperature, the kale dry powder is soaked pretreated with 95% ethanol three times, each time for 120 min; the ratio of the kale dry powder to 95% ethanol is 1:5, w / v; the soaked kale powder is dried at 55°C to obtain the kale dry powder after preliminary impurity removal; subsequently, a water bath combined with ultrasonic treatment technology is used to extract soluble polysaccharides from the kale dry powder after preliminary impurity removal to obtain a crude kale polysaccharide solution; (3) Purification of crude kale polysaccharide: The crude kale polysaccharide solution obtained in step (2) is filtered through a 200-mesh gauze. Under the condition of pH 6.2, papain with an enzyme activity of ≥2000 units / mg is added to the filtered crude kale polysaccharide solution. The ratio of papain to the filtered crude kale polysaccharide solution is 0.1 mg:1 mL, and the crude kale polysaccharide solution added with papain is reacted in a 55°C water bath for 1.5 h and then the papain is inactivated at 90°C to remove the protein in the crude polysaccharide solution to obtain a kale polysaccharide solution; The kale polysaccharide solution is centrifuged and the supernatant is collected. The collected supernatant is concentrated, and ethanol is added to the concentrated supernatant. The ratio of the concentrated supernatant to ethanol is 1:3, v / v. It is left to stand at 4°C for 24 h to fully precipitate the kale polysaccharide in the concentrated supernatant to form a kale polysaccharide suspension system; the kale polysaccharide suspension system is filtered by suction and freeze-dried to obtain purified kale polysaccharide; (4) Preparation of kale-apple compound fruit and vegetable juice original juice: The kale original juice and apple original juice obtained in step (1) are mixed evenly and subjected to ultrasonic treatment to obtain kale-apple compound fruit and vegetable juice original juice; (5) Addition of kale polysaccharide: The purified kale polysaccharide prepared in step (3) is added to the kale-apple compound fruit and vegetable juice original juice obtained in step (4), and after mixing evenly, it is reserved for use; (6) Sterilization and storage: The kale-apple compound fruit and vegetable juice original juice added with kale polysaccharide obtained in step (5) is subjected to thermal sterilization, cooling and filling to obtain the finished kale-apple compound fruit and vegetable juice.

2. A method for improving the anti-stratification stability of kale-apple composite fruit and vegetable juice according to claim 1, characterized in that, In step (2), the water bath is to mix the kale dry powder after preliminary impurity removal with distilled water at a material-liquid ratio of 1:5-20 g / mL and treat it in an 80°C water bath for 1 h; the ultrasonic treatment conditions are: treatment for 1 h under an ultrasonic condition of 300-750 W.

3. A method for improving the anti-stratification stability of kale-apple composite fruit and vegetable juice according to claim 1, characterized in that, In step (3), the centrifugation is carried out on the polysaccharide solution from which the protein has been removed at 5000 r / min for 15 min.

4. A method for improving the anti-stratification stability of kale-apple composite fruit and vegetable juice according to claim 1, characterized in that, In step (3), the concentration is carried out under the conditions of a vacuum degree of -0.09 MPa and a temperature of 45 °C to reduce the volume of the supernatant collected after centrifugation to 1 / 3 of the initial volume.

5. A method for improving the anti-stratification stability of kale-apple composite fruit and vegetable juice according to claim 1, characterized in that, In step (4), the mixing ratio of kale original juice and apple original juice is 4:6 by mass.

6. The method for improving the anti-stratification stability of kale-apple compound fruit and vegetable juice according to claim 1, characterized in that, In step (4), the ultrasonic treatment conditions are: the ultrasonic power is 600 - 900 W, the treatment duration is 25 min, and the whole process is carried out under the constant temperature condition of 25 °C.

7. A method for improving the anti-stratification stability of kale-apple composite fruit and vegetable juice according to claim 1, characterized in that, In step (5), the kale polysaccharide described in step (3) is added to the kale-apple compound fruit and vegetable juice prepared in step (4), and the addition amount is 0.4% - 0.8% of the total mass of the compound fruit and vegetable juice.

8. A method for improving the anti-stratification stability of kale-apple compound fruit and vegetable juice according to claim 1, characterized in that, In step (6), the set temperature of the thermal sterilization process is 85 °C, and the treatment duration is 10 min; the filling temperature is 40 °C.

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