A health-preserving tea rich in mulberry leaf stem cell active substances and a preparation method thereof

Abstract

The application discloses a health tea rich in mulberry leaf stem cell active substances and a preparation method thereof, and belongs to the technical field of health tea. The preparation method comprises the following steps: obtaining a mulberry leaf stem cell suspension culture by inducing and culturing an external explant of a mulberry tree; after the stem cells are broken at low temperature and high pressure, the active substance extract is obtained by ultrasonic-assisted extraction of a low-eutectic solvent under low-temperature conditions; the extract is concentrated, embedded with nanoliposomes, and freeze-dried to prepare the active substance nanoliposome freeze-dried powder; fresh mulberry leaves are subjected to deep freezing, thawing, cutting and low-temperature vacuum drying to prepare mulberry leaf base tea blanks; finally, the active substance freeze-dried powder is loaded on the surface of the tea blanks by fluidized bed coating, and the product is obtained after low-temperature drying. The preparation method significantly improves the content and stability of active ingredients such as DNJ, flavones and polysaccharides in the health tea, and the product has excellent antioxidant activity and good sensory quality.

Description

Technical Field

[0001] This invention belongs to the field of health tea technology, and in particular relates to a health tea rich in mulberry leaf stem cell active substances and its preparation method. Background Technology

[0002] Mulberry leaves (Morus alba L.) are the leaves of plants belonging to the genus Morus in the family Moraceae, and have a long history of medicinal and edible use. In the *Shennong Bencao Jing* (Shennong's Classic of Materia Medica), mulberry leaves are referred to as "immortal leaves," and are described as having a cold nature and a sweet and bitter taste, possessing the effects of dispersing wind-heat, clearing the lungs and moistening dryness, and clearing the liver and improving eyesight. Modern research shows that mulberry leaves contain abundant bioactive components, including flavonoids (such as rutin, luteolin, and myricetin), alkaloids (such as 1-deoxynojirimycin DNJ), polysaccharides, polyphenols, and γ-aminobutyric acid, which have various physiological effects such as lowering blood sugar, lowering blood lipids, antioxidation, and anti-inflammation. Among them, 1-deoxynojirimycin (DNJ) is a polyhydroxypiperidine small molecule alkaloid with good hypoglycemic and antiviral activities, and is an important quality indicator of mulberry leaves and their extracts.

[0003] However, traditional mulberry leaf tea processing faces numerous technical bottlenecks. First, the content of active ingredients in mulberry leaves is relatively low and significantly affected by factors such as variety, harvesting season, and planting location, leading to unstable product quality. Second, traditional mulberry leaf tea processing often employs high-temperature methods such as fixation, stir-frying, and drying, which result in a significant loss of heat-sensitive active ingredients, failing to fully realize the health benefits of mulberry leaves. Furthermore, existing mulberry leaf tea preparation methods primarily target mature mulberry leaves directly, failing to fully tap the enormous potential of stem cell-level active substances within the leaves.

[0004] Plant stem cells are characterized by multiple small vacuoles, high mitochondrial activity, and the absence of lignin deposition in their cell walls. During suspension culture, they mostly exist as single cells, maintaining a stable proliferation rate and long-term viability. Plant stem cell culture technology allows for the large-scale in vitro production of plant stem cells and their derivatives, reducing reliance on wild plants. However, research on processes combining the active substances of mulberry leaf stem cells with the preparation of health-promoting teas is currently lacking.

[0005] Therefore, developing a method for preparing health-preserving tea that can efficiently enrich the active substances of mulberry leaf stem cells while maximizing their biological activity has significant practical implications and market value. Summary of the Invention

[0006] This invention addresses the technical problems in existing mulberry leaf tea preparation methods, such as low content of active ingredients, severe loss of heat-sensitive components, and unstable product quality, by providing a health-preserving tea rich in mulberry leaf stem cell active substances and its preparation method.

[0007] To achieve the above objectives, the present invention provides a method for preparing a health-preserving tea rich in mulberry leaf stem cell active substances, comprising the following steps: S1: Mulberry leaf stem cell induction and suspension culture: S11. Select young leaves, petioles or stem segments of mulberry trees as explants. After disinfection, inoculate them onto callus induction medium and induce culture for 15-25 days at a temperature of 24-28℃ in the dark to obtain mulberry leaf callus. S12. Transfer the mulberry leaf callus tissue to a liquid suspension culture medium and culture it in suspension at a temperature of 25-27℃, a rotation speed of 100-140 rpm, a light intensity of 1500-2500 Lux, and a photoperiod of 12h light / 12h dark. Subculture every 7-10 days for 3-5 consecutive subcultures to obtain a stable mulberry leaf stem cell suspension culture. The liquid suspension culture medium consists of MS medium as the basal medium, supplemented with 20-40 g / L sucrose, 0.3-1.0 mg / L 6-benzylaminopurine, 0.5-1.5 mg / L 2,4-dichlorophenoxyacetic acid, 0.5-1.5 mg / L naphthaleneacetic acid, and 0.5-2.0 mg / L methyljasmonic acid ester, with the pH adjusted to 5.6-5.9.

[0008] S2: Low-temperature differential phase extraction of active substances from mulberry leaf stem cells: S21. Collect the mulberry leaf stem cell culture culture that has been cultured in suspension to the logarithmic growth phase in S1, and centrifuge it at 8000-12000 rpm for 10-20 min at 4℃ to collect the cell pellet. S22. Resuspend the cell pellet in pre-cooled phosphate buffer and perform low-temperature high-pressure microfluidic disruption at a pressure of 80-120 MPa. Repeat the disruption process 2-4 times to obtain cell lysate. S23. Add an ultrasonic-assisted eutectic solvent to the cell lysate for extraction. The eutectic solvent consists of choline chloride and fructose in a molar ratio of 1-2:1. The volume ratio of the eutectic solvent to the cell lysate is 1:2-5. Perform ultrasonic extraction at 0-4℃ for 20-40 min with an ultrasonic power of 200-400W. After extraction, centrifuge and collect the supernatant to obtain the extract of mulberry leaf stem cell active substances.

[0009] S3: Nanoparticle encapsulation and stabilization of active substances: S31. The mulberry leaf stem cell active substance extract obtained in S2 is concentrated to 1 / 5 to 1 / 3 of its original volume by ultrafiltration to obtain an active substance concentrate. S32. Preparation of nanoliposomes by thin film dispersion method: Soybean lecithin and cholesterol are dissolved in anhydrous ethanol at a mass ratio of 5-10:1, and after rotary evaporation to form a film, an active substance concentrate is added for hydration. The mixture is then subjected to high-pressure homogenization and extrusion molding to obtain active substance nanoliposomes with a particle size of 80-200 nm. S33. Mix the nanoliposome embedding material with a freeze-drying protectant at a mass ratio of 1:1-3. The freeze-drying protectant is a mixture of trehalose and mannitol at a mass ratio of 2-3:1. After freeze-drying, obtain the active substance nanoliposome freeze-dried powder.

[0010] S4: Low-temperature preparation of mulberry leaf-based tea base: S41. Select fresh mulberry leaves, rinse them with clean water, drain them, and then freeze them at -18 to -25℃ for 12-24 hours. S42. Thaw the deep-frozen mulberry leaves slowly at 4℃, and then cut them into shreds or strips. S43. Dry the chopped mulberry leaves at a low temperature of 40-60℃ under vacuum until the moisture content is 8%-12% to obtain mulberry leaf base tea.

[0011] S5. Active substance loading and finished product preparation: S51. Prepare a 1%-5% (w / w) complex solution of the lyophilized nanoliposome powder obtained in S3 with purified water. S52. Place the mulberry leaf-based tea blanks obtained in S4 into a fluidized bed coating equipment, and use the reconstituted solution in S51 as the coating liquid for bottom spray coating. The spraying rate of the coating liquid is 1-3 mL / min, the inlet air temperature is 30-40℃, and the coating is carried out until the weight gain of the mulberry leaf-based tea blanks is 5%~15%. S53. Dry the coated mulberry leaf tea leaves at a low temperature of 25-35℃ until the moisture content does not exceed 7%, and then package them with nitrogen to obtain a health tea product rich in mulberry leaf stem cell active substances.

[0012] Compared with the prior art, the present invention has the following advantages and technical effects: (1) This invention introduces mulberry leaf stem cell suspension culture technology into the field of health tea preparation for the first time. By culturing mulberry leaf stem cells on a large scale in vitro, sustainable and stable production of mulberry leaf active substances is achieved, effectively avoiding the problem of unstable quality caused by factors such as variety, season and place of origin of traditional mulberry leaf raw materials.

[0013] (2) This invention employs low-temperature, high-pressure microfluidic disruption combined with ultrasound-assisted eutectic solvent extraction technology to efficiently disrupt mulberry leaf stem cells and extract their active substances under low-temperature conditions. Eutectic solvents, as a novel green solvent, have advantages such as strong dissolving power and biodegradability. Combined with low-temperature operating conditions, they can maximize the protection of the bioactivity of heat-sensitive active ingredients such as DNJ, flavonoids, and polysaccharides.

[0014] (3) The present invention encapsulates the active substances of mulberry leaf stem cells with nanoliposome encapsulation technology to form nanoscale encapsulations of 80~200nm, which effectively solves the problem of easy oxidation and degradation of active substances during storage and brewing, and significantly improves the stability and bioavailability of active substances.

[0015] (4) The present invention adopts a process route of deep freezing-slow thawing-low temperature vacuum drying to process mulberry leaf base tea blanks, replacing the traditional high temperature fixation and drying process, avoiding the destruction of natural active ingredients in mulberry leaf base tea blanks by high temperature, and at the same time, the freeze-thaw treatment causes the cell walls of mulberry leaves to break, which is conducive to the loading and penetration of subsequent active substances.

[0016] (5) The present invention uses fluidized bed bottom spray coating technology to uniformly load the active substance nanoliposome freeze-dried powder onto the surface of mulberry leaf base tea blank. The coating layer is uniform and dense, and the active substance can be released quickly when brewing, ensuring the consistency of product efficacy. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 Comparison of DNJ content in health-preserving teas prepared by different methods; Figure 2 Comparison of total flavonoid content in health teas prepared by different methods; Figure 3 Comparison of total polysaccharide content in health teas prepared by different methods. Detailed Implementation

[0019] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0020] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0021] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0022] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0023] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0024] Unless otherwise specified, the term "parts" in this invention refers to parts by weight.

[0025] Example 1 A method for preparing a health-preserving tea rich in mulberry leaf stem cell active substances includes the following steps: S1: Mulberry leaf stem cell induction and suspension culture: Young mulberry leaves were selected as explants, disinfected with 75% ethanol for 30 seconds and 0.1% mercuric chloride for 8 minutes, rinsed 5 times with sterile water, and inoculated onto callus induction medium (MS medium + sucrose 30 g / L + agar 7 g / L + 6-benzylaminopurine 0.5 mg / L + 2,4-dichlorophenoxyacetic acid 1.0 mg / L). The callus tissue was obtained by dark culture at 26℃ for 20 days.

[0026] Callus tissue was transferred to liquid suspension medium (MS medium + 30 g / L sucrose + 0.5 mg / L 6-benzylaminopurine + 1.0 mg / L 2,4-dichlorophenoxyacetic acid + 1.0 mg / L naphthaleneacetic acid + 1.0 mg / L methyljasmonic acid ester, pH 5.8) and cultured in suspension at 26℃, 120 rpm, 2000 Lux, under 12h light / 12h dark conditions. Subculture was performed every 8 days for a total of 4 subcultures to obtain a stable mulberry leaf stem cell suspension culture.

[0027] S2: Low-temperature differential phase extraction of active substances from mulberry leaf stem cells: Collect mulberry leaf stem cell cultures cultured in suspension to the logarithmic growth phase, centrifuge at 10,000 rpm for 15 min at 4℃, and collect the cell pellet. Resuspend the cell pellet in pre-cooled PBS buffer and use a low-temperature high-pressure microfluidic disruptor to cycle and disrupt the cells three times at 100 MPa pressure to obtain the cell lysate.

[0028] A eutectic solvent consisting of choline chloride and fructose in a molar ratio of 1.5:1 was added to the cell lysate. The volume ratio of the eutectic solvent to the cell lysate was 1:3. The mixture was ultrasonically extracted at 2°C for 30 min with an ultrasonic power of 300 W. After extraction, the mixture was centrifuged at 4°C and 12,000 rpm for 15 min. The supernatant was collected to obtain the extract of active substances from mulberry leaf stem cells.

[0029] S3: Nanoparticle encapsulation and stabilization of active substances: The extract was concentrated to 1 / 4 of its original volume using an ultrafiltration membrane (with a molecular weight cutoff of 3 kDa) to obtain a concentrated solution of active substances.

[0030] Soybean lecithin and cholesterol were dissolved in anhydrous ethanol at a mass ratio of 8:1. After rotary evaporation to form a film, the active substance concentrate was added for hydration. The mixture was then subjected to high-pressure homogenization (80 MPa, 3 times) and extrusion through a 200 nm polycarbonate membrane to obtain nanoliposome embeddings.

[0031] The nanoliposome encapsulated material was mixed with a freeze-drying protectant (trehalose:mannitol = 2.5:1) at a mass ratio of 1:2, and then freeze-dried to obtain the active substance nanoliposome freeze-dried powder.

[0032] S4: Low-temperature preparation of mulberry leaf-based tea base: Fresh mulberry leaves are selected, rinsed with clean water, drained, and then deep-frozen at -22℃ for 18 hours. The deep-frozen mulberry leaves are then slowly thawed at 4℃ and shredded. The shredded mulberry leaves are then vacuum-dried at 50℃ until the moisture content is 10%, obtaining mulberry leaf base tea.

[0033] S5: Active substance loading and finished product preparation: The lyophilized nano-liposome powder containing active substances was prepared into a 3% (w / w) reconstituted solution with purified water. Mulberry leaf-based tea blanks were placed in a fluidized bed coating apparatus, and bottom-spray coating was performed using the reconstituted solution as the coating liquid. The spray rate of the coating liquid was 2 mL / min, and the inlet air temperature was 35℃. Coating was carried out until the weight gain of the mulberry leaf-based tea blanks reached 10%. The coated mulberry leaf tea blanks were then dried at 30℃ until the moisture content was 6%, and then packaged with nitrogen to obtain the finished health tea product rich in mulberry leaf stem cell active substances.

[0034] Example 2 A method for preparing a health-preserving tea rich in mulberry leaf stem cell active substances differs from Example 1 in that: the liquid suspension culture medium in S1 consists of MS medium + 25 g / L sucrose + 0.3 mg / L 6-benzylaminopurine + 0.5 mg / L 2,4-dichlorophenoxyacetic acid + 0.5 mg / L naphthaleneacetic acid + 0.5 mg / L methyljasmonic acid ester, pH 5.6. In S2, the eutectic solvent consists of choline chloride and fructose in a molar ratio of 1:1. In S3, the mass ratio of soybean lecithin to cholesterol is 5:1. The remaining steps are the same as in Example 1.

[0035] Example 3 A method for preparing a health-preserving tea rich in mulberry leaf stem cell active substances differs from Example 1 in that: the liquid suspension culture medium in S1 consists of MS medium + 40 g / L sucrose + 1.0 mg / L 6-benzylaminopurine + 1.5 mg / L 2,4-dichlorophenoxyacetic acid + 1.5 mg / L naphthaleneacetic acid + 2.0 mg / L methyljasmonic acid ester, pH 5.9. In S2, the eutectic solvent consists of choline chloride and fructose in a molar ratio of 2:1. In S3, the mass ratio of soybean lecithin to cholesterol is 10:1. The remaining steps are the same as in Example 1.

[0036] Comparative Example 1 The traditional mulberry leaf tea preparation method is adopted: fresh mulberry leaves are rinsed with clean water, dried and withered, then subjected to high temperature of 220℃ for 3 minutes to fix the greenness, kneaded and then dried at 120℃ to a moisture content of 8% to obtain traditional mulberry leaf tea.

[0037] Comparative Example 2 The mulberry leaf direct crushing and extraction process is adopted: fresh mulberry leaves are washed, dried at 60℃ and crushed to 200 mesh, pure water is added and pulped, the pH is adjusted to 4.0 with citric acid, and extracted at 4℃ for 3.5 hours. The supernatant is filtered and spray-dried and then mixed with ordinary mulberry leaf tea base.

[0038] Comparative Example 3 The direct drying process of mulberry leaf stem cell culture was adopted: mulberry leaf stem cell suspension culture was obtained according to the method of Example 1 S1, and then directly freeze-dried and mixed with ordinary mulberry leaf tea base.

[0039] Test Example 1 Take 5g of each of the health-preserving tea samples obtained in Examples 1-3 and Comparative Examples 1-3, steep them in 100mL of boiling water for 5 minutes, and then filter. The content of 1-deoxynojirimycin (DNJ) in the filtrate was determined by high-performance liquid chromatography (HPLC), and the contents of total flavonoids and total polysaccharides were determined by ultraviolet-visible spectrophotometry. The results are shown in Table 1 and... Figures 1-3 .

[0040] Table 1 Comparison of the content of main active ingredients in health teas prepared by different methods

[0041] As shown in Table 1, the contents of DNJ, total flavonoids, and total polysaccharides in the health teas obtained in Examples 1-3 were significantly higher than those in Comparative Examples 1-3. P <0.01). In Example 1, the DNJ content reached 2.86 mg / g, which was 6.8 times that of Comparative Example 1, 3.2 times that of Comparative Example 2, and 2.1 times that of Comparative Example 3; the total retention rate of active ingredients reached 94.2%, far exceeding the 12.7% of Comparative Example 1, 25.3% of Comparative Example 2, and 38.6% of Comparative Example 3. The results indicate that the preparation method of this invention can efficiently enrich and retain the active substances in mulberry leaf stem cells, overcoming the shortcomings of traditional processes that result in severe loss of active ingredients.

[0042] Test Example 2 Take 5g of each of the health-preserving tea samples obtained in Examples 1-3 and Comparative Examples 1-3, steep them in 100mL of boiling water for 5min, and then filter them. The antioxidant activity of each sample was evaluated by the DPPH free radical scavenging rate assay and the ABTS free radical scavenging rate assay. The results are shown in Table 2.

[0043] Table 2 Comparison of antioxidant activities of health teas prepared by different methods

[0044] As shown in Table 2, the scavenging rates of DPPH and ABTS free radicals and the FRAP reducing power of the health teas obtained in Examples 1-3 were significantly higher than those in Comparative Examples 1-3. P <0.01). Example 1 showed a DPPH scavenging rate of 87.6% and an ABTS scavenging rate of 92.4%, which were 2.8 times and 2.6 times that of Comparative Example 1, respectively. The results indicate that the health-preserving tea prepared by the method of this invention possesses excellent antioxidant activity, which is closely related to its rich content of mulberry leaf stem cell active substances.

[0045] Test Example 3 The health-preserving tea product obtained in Example 1 was sealed and stored in the dark at 25℃ and 40℃ for 0, 3, and 6 months, respectively. The changes in DNJ content in the samples were measured to examine the product's stability. The results are shown in Table 3.

[0046] Table 3. Changes in DNJ content (mg / g) of the health-preserving tea in Example 1 under different storage conditions.

[0047] As shown in Table 3, the DNJ retention rate of the health-preserving tea obtained in Example 1 remained at 96.2% after 6 months of storage at 25℃, and at 90.2% after 6 months of accelerated storage at 40℃. The results indicate that the present invention effectively stabilizes and protects the active substances of mulberry leaf stem cells through nanoliposome encapsulation technology, and the product exhibits excellent storage stability.

[0048] Test Example 4 Take 5g of each of the health-preserving tea samples obtained in Examples 1-3 and Comparative Examples 1-3, and steep them in 100mL of boiling water for 5 minutes. Ten trained tasters then conducted sensory evaluations based on four aspects: color, aroma, taste, and liquor color, using a 100-point scoring system. The results are shown in Table 4.

[0049] Table 4 Sensory evaluation results of health teas prepared by different methods

[0050] As shown in Table 4, the total sensory evaluation scores of the health teas obtained in Examples 1-3 were significantly higher than those of Comparative Examples 1-3. P <0.01). Example 1 achieved a total score of 92.0 points, with particularly outstanding scores in aroma and taste. The results show that the low-temperature preparation method of this invention effectively avoids the burnt and grassy smells produced by high-temperature processing. The product has a bright green color, elegant aroma, mellow taste, and clear and bright liquor, exhibiting excellent sensory qualities.

[0051] This invention provides a health-preserving tea rich in mulberry leaf stem cell active substances and its preparation method. The process is clear, controllable, and suitable for industrial production. Through large-scale in vitro culture of mulberry leaf stem cells, the limitations of the natural environment can be overcome, achieving a stable year-round supply of mulberry leaf active substances. Furthermore, this invention employs advanced technologies such as low-temperature differential phase extraction, nanoliposome encapsulation, and fluidized bed coating, resulting in a product with high active ingredient content, good stability, and uniform quality, possessing broad market application prospects.

[0052] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a health-preserving tea rich in mulberry leaf stem cell active substances, characterized in that, Includes the following steps: S1. Callus induction was performed on mulberry explants, followed by suspension culture in liquid suspension medium to obtain mulberry leaf stem cell suspension culture. S2. Collect mulberry leaf stem cell suspension culture, collect cell pellet after solid-liquid separation, and then perform low-temperature high-pressure disruption on the cell pellet to obtain cell lysate. A eutectic solvent was added to the cell lysate, and ultrasonic-assisted extraction was performed at low temperature. After solid-liquid separation, the supernatant was collected to obtain the extract of active substances from mulberry leaf stem cells. S3. The extract of active substances from mulberry leaf stem cells is concentrated. Phospholipids and cholesterol are used as membrane materials to encapsulate the concentrated active substances in nanoliposomes. Then, a freeze-drying protectant is added and the mixture is freeze-dried to obtain freeze-dried nanoliposome powder of active substances. S4. Deep freeze fresh mulberry leaves, then thaw them at low temperature. After thawing, cut them into pieces and dry them under low temperature vacuum to obtain mulberry leaf base tea. S5. The active substance nanoliposome freeze-dried powder is reconstituted and prepared into a coating solution. The coating solution is loaded onto the surface of mulberry leaf-based tea blanks using fluidized bed coating technology. After low-temperature drying, a health tea rich in mulberry leaf stem cell active substances is obtained.

2. The method for preparing a health-preserving tea rich in mulberry leaf stem cell active substances according to claim 1, characterized in that: In S1, the liquid suspension medium was based on MS medium, with the addition of 20-40 g / L sucrose, 0.3-1.0 mg / L 6-benzylaminopurine, 0.5-1.5 mg / L 2,4-dichlorophenoxyacetic acid, 0.5-1.5 mg / L naphthaleneacetic acid, and 0.5-2.0 mg / L methyljasmonic acid ester, and the pH was adjusted to 5.6-5.

9. The suspension culture conditions are: temperature 25-27℃, rotation speed 100-140rpm, light intensity 1500-2500Lux, photocycle 12h light / 12h dark, subculture every 7-10 days, and continuous subculture 3-5 times.

3. The method for preparing a health-preserving tea rich in mulberry leaf stem cell active substances according to claim 1, characterized in that: In S2, the eutectic solvent consists of choline chloride and fructose in a molar ratio of 1-2:1; the low-temperature condition is 0-4℃.

4. The method for preparing a health-preserving tea rich in mulberry leaf stem cell active substances according to claim 1, characterized in that: In S3, the phospholipid is soybean lecithin, and the mass ratio of soybean lecithin to cholesterol is 5-10:1; the particle size of the nanoliposomes is 80-200 nm.

5. The method for preparing a health-preserving tea rich in mulberry leaf stem cell active substances according to claim 1, characterized in that: In S2, low-temperature high-pressure crushing is carried out using low-temperature high-pressure micro-jet crushing with a crushing pressure of 80-120MPa and 2-4 cycles; ultrasonic-assisted extraction has a power of 200-400W and a time of 20-40min.

6. The method for preparing a health-preserving tea rich in mulberry leaf stem cell active substances according to claim 1, characterized in that: In S3, the freeze-drying protectant is a mixture of trehalose and mannitol, and the mass ratio of the nanoliposome encapsulation material to the freeze-drying protectant is 1:1-3.

7. The method for preparing a health-preserving tea rich in mulberry leaf stem cell active substances according to claim 1, characterized in that: In S3, the concentration is achieved by ultrafiltration to 1 / 5 to 1 / 3 of the original volume; the encapsulation is achieved by thin-film dispersion, followed by high-pressure homogenization and extrusion molding.

8. The method for preparing a health-preserving tea rich in mulberry leaf stem cell active substances according to claim 1, characterized in that: In S4, the temperature for deep freezing is -18 to -25℃, and the time is 12-24 hours; the temperature for low-temperature vacuum drying is 40-60℃, and the mulberry leaves are dried until the moisture content is 8%-12%.

9. The method for preparing a health-preserving tea rich in mulberry leaf stem cell active substances according to claim 1, characterized in that: In S5, the mass fraction of the coating solution is 1%-5%; the fluidized bed coating adopts the bottom spray method, the spraying speed of the coating solution is 1-3mL / min, the inlet air temperature is 30-40℃, and the weight gain of the mulberry leaf base tea is 5%-15% after coating.

10. A health-preserving tea prepared by the method for preparing a health-preserving tea rich in mulberry leaf stem cell active substances as described in any one of claims 1-9.

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