Preparation method of functional hippophae rhamnoides fruit and Chinese wolfberry fruit composite freeze-dried solid fruit tea

Abstract

The invention discloses a preparation method of functional hippophae rhamnoides fruit and Chinese wolfberry fruit composite freeze-dried solid fruit tea, which comprises the following steps: uniformly mixing hippophae rhamnoides fruit primary pulp, Chinese wolfberry fruit primary pulp, modified starch, honey and isomaltooligosacharide according to a ratio of (1-1.5): (1-1.4): (0.1-0.2): (0.08-0.12): (0.8-1.2), pouring into a mold, pre-freezing at an ultralow temperature of-60 DEG C to-40 DEG C for 20-30 hours, and drying by using a vacuum freeze dryer to obtain the functional hippophae rhamnoides fruit and Chinese wolfberry fruit composite freeze-dried solid fruit tea. And finally obtaining the hippophae rhamnoides fruit and fructus lycii composite freeze-dried solid fruit tea. The hippophae rhamnoides fruit and Chinese wolfberry fruit composite freeze-dried solid fruit tea adopts a vacuum freeze-drying technology, maximally retains the active ingredients of the product, is convenient to carry, does not need to be brewed, can be directly eaten, has few additives, is green and purely natural, is rich in various active ingredients such as vitamin C, flavone and the like, tastes sour and sweet, and is suitable for various people.

Description

Technical Field

[0001] The present invention relates to the technical field of food processing, and more specifically, to a method for preparing functional seabuckthorn and wolfberry composite freeze-dried solid fruit tea. Background Art

[0002] Seabuckthorn has many medicinal effects and functions, including enhancing immunity, promoting digestion, preventing cardiovascular diseases, and relieving inflammation. Seabuckthorn flavonoids are the main medicinal active ingredients of seabuckthorn. The active substances of seabuckthorn flavonoids can reduce high blood pressure, soften blood vessels, prevent platelet aggregation, improve blood circulation, reduce cholesterol and triglycerides in the blood, soften blood vessels, prevent atherosclerosis, reduce blood viscosity, inhibit platelet aggregation, reduce low-density lipoprotein, remove deposits on the blood vessel wall, restore blood vessel elasticity, increase coronary blood flow, reduce myocardial oxygen consumption, and enhance heart function. Seabuckthorn flavonoids can also play a role in anti-arrhythmia, anti-myocardial ischemia, reduce the area of ​​myocardial infarction, relieve angina pectoris, and improve heart function by scavenging active oxygen free radicals. Lycium barbarum is a traditional Chinese medicine, which is the dried mature fruit of the Ningxia Lycium barbarum plant of the Solanaceae family. It is sweet in taste, neutral in nature, and belongs to the liver and kidney meridians. It has the effects of nourishing the liver and kidney, improving the essence and improving the eyesight. It can relieve the symptoms of weakness of waist and knees, dizziness and tinnitus, impotence and spermatorrhea, internal heat and thirst caused by liver and kidney yin deficiency and insufficient essence and blood, as well as chlorosis and blurred vision. Lycium barbarum polysaccharide is a type of high molecular weight polysaccharide extracted from wolfberry, with a molecular weight between 50,000 and 150,000, composed of xylose, galactose, mannose, rhamnose, glucose and arabinose. Lycium barbarum polysaccharide is a water-soluble polysaccharide, the main active ingredient in wolfberry, and has multiple functions. Prebiotics refer to some organic substances that are not digested and absorbed by the host but can selectively promote the metabolism and proliferation of beneficial bacteria in the body, thereby improving the health of the host. Since prebiotics cannot be decomposed, absorbed and utilized by the human body, some can be decomposed and utilized by the colon flora after passing through the digestive tract to reach the colon, thereby promoting the growth of colon flora. They are of great significance in improving intestinal microecology and promoting the metabolism of lipids, proteins and minerals, so they are increasingly widely used in the fields of food and feed. As a prebiotic, isomaltooligosaccharide is a kind of starch sugar. Its main components are isomaltose, panose, isomaltotriose and oligosaccharides above tetrasaccharides, which are bound by α-1,6 glycosidic bonds between glucose molecules. It can promote the growth and reproduction of beneficial bacteria-bifidobacteria in the human body, and has the function of water-soluble dietary fiber, low calorific value, and anti-caries.

[0003] However, most of the seabuckthorn and wolfberry products in the prior art are in powder or granular form and need to be brewed before drinking, which is not convenient for direct consumption. For example, the invention patent application with application publication number CN117122637A discloses a seabuckthorn and wolfberry preparation and its preparation method and application. The granular preparation needs to be taken with water or brewed and cannot be eaten directly, which affects its convenience of consumption. Summary of the invention

[0004] One object of the present invention is to provide a method for preparing a functional seabuckthorn and wolfberry composite freeze-dried solid fruit tea, which solves the problems of sour taste of seabuckthorn and inconvenience in eating solid particle beverages, and has the advantages of being easy to carry, no need for brewing, can be eaten directly, few additives, green and natural, rich in vitamin C, flavonoids and other active ingredients, and sweet and sour taste.

[0005] In order to achieve these purposes and other advantages according to the present invention, according to one aspect of the present invention, the present invention provides a method for preparing a functional seabuckthorn and wolfberry composite freeze-dried solid fruit tea, comprising the following steps: uniformly mixing seabuckthorn puree, wolfberry puree, modified starch, honey, and isomaltooligosaccharide in a mass ratio of (1-1.5): (1-1.4): (0.1-0.2): (0.08-0.12): (0.8-1.2), pouring the mixture into a mold, pre-freezing the mixture at an ultra-low temperature of -60°C to -40°C for 20-30 h, and drying the mixture in a vacuum freeze dryer to finally obtain the seabuckthorn and wolfberry composite freeze-dried solid fruit tea; wherein the modified starch is prepared by composite cross-linking of cassava starch and sodium alginate.

[0006] Preferably, the preparation of the seabuckthorn puree comprises the following steps: Wash and remove the seeds of sea buckthorn, squeeze the juice and filter it; The high-pressure homogenization combined sterilization process is adopted: the filtrate is placed in a high-pressure homogenizer, and the pressure is increased to 150MPa in three stages in a continuous linear pressure increase mode, and the pressure increase rates are 2-5MPa / s, 5-8MPa / s, and 8-10MPa / s, respectively. After each pressure increase, the pressure is maintained at 30-50℃ for 3-5 minutes, and then the pressure is released. The above pressure increase-pressure maintenance-pressure release process is repeated three times; After the above treatment, sea buckthorn puree is obtained.

[0007] Preferably, before adopting the high-pressure homogenization combined sterilization process, the seabuckthorn puree is first subjected to microbial detection to determine the contaminating bacteria species therein, and then the specific pressure increase method is determined according to different bacteria species, as follows: If E. coli is detected in the seabuckthorn puree, the pressure is increased to 50MPa at a rate of 3-4MPa / s for the first time and maintained for 2 minutes. During this stage, the cell wall and cell membrane of E. coli are gradually damaged by using relatively mild pressure and pressure increase rate; the second time, the pressure is increased from 50MPa to 100MPa at a rate of 5-6MPa / s and maintained for 2 minutes to further destroy the protein and nucleic acid structure inside E. coli; the third time, the pressure is increased from 100MPa to 150MPa at a rate of 8-9MPa / s and maintained for 4 minutes; If the presence of Staphylococcus aureus is detected, the pressure is increased to 60MPa at a rate of 4-5MPa / s for the first time and maintained for 2 minutes. This rate and pressure can initially act on the tougher cell wall of Staphylococcus aureus; the second time, the pressure is increased from 60MPa to 110MPa at a rate of 6-7MPa / s and maintained for 2 minutes to enhance the damage to its cell wall and internal structure; the third time, the pressure is increased from 110MPa to 150MPa at a rate of 9-10MPa / s and maintained for 4 minutes; If yeast is detected, the pressure is increased to 40MPa at a rate of 2-3MPa / s for the first time and maintained for 2 minutes. The pressure is slowly increased to change the cell membrane permeability of the yeast. The second time, the pressure is increased from 40MPa to 90MPa at a rate of 4-5MPa / s and maintained for 2 minutes to further affect the metabolism and reproduction of the yeast. The third time, the pressure is increased from 90MPa to 150MPa at a rate of 7-8MPa / s and maintained for 4 minutes. If mold is detected, the pressure is first increased at a rate of 3-4MPa / s to 55MPa and maintained for 2 minutes to cause certain damage to the mycelium and spores of the mold; the second time, the pressure is increased from 55MPa to 105MPa at a rate of 5-6MPa / s and maintained for 2 minutes to further damage the mold structure; the third time, the pressure is increased from 105MPa to 150MPa at a rate of 8-9MPa / s and maintained for 4 minutes; If at least two of the above strains are detected, the following comprehensive pressure increase method is used: the first pressure increase is from 3-4MPa / s to 55MPa, and the pressure is maintained for 2 minutes; the second pressure increase is from 55MPa to 105MPa at a rate of 5-6MPa / s, and the pressure is maintained for 2 minutes; the third pressure increase is from 105MPa to 150MPa at a rate of 8-9MPa / s, and the pressure is maintained for 4 minutes; The pressure is maintained at 40°C after each pressure increase. After the above treatment, sea buckthorn puree is obtained, and the sterilization rate of the corresponding bacteria can be achieved ≥99.9%, while the vitamin C retention rate is ≥88% and the flavonoid retention rate is ≥92%.

[0008] Preferably, the wolfberry puree is prepared by washing wolfberries, squeezing juice, filtering, homogenizing, and sterilizing; the seabuckthorn puree is prepared by washing seabuckthorn, squeezing juice, filtering, homogenizing, and sterilizing; The homogenization and sterilization process adopts high-pressure homogenization combined with sterilization, and the specific steps are: placing sea buckthorn puree or wolfberry puree in a high-pressure homogenizer, increasing the pressure to the target pressure in a continuous linear pressure-increasing manner, maintaining the pressure, and then releasing the pressure, repeating three times, wherein the target pressure is 150 MPa, the pressure-maintaining time is 3-5 min, and the pressure-maintaining temperature is 30-50°C; The pressure increasing rates of the three linear pressure increasing processes are 2~5 MPa / s, 5~8 MPa / s, and 8~10 MPa / s, respectively.

[0009] Preferably, the following coordinated processing is performed during the three linear boost processes: The first pressure-raising stage: After the pressure is raised to 150 MPa at a rate of 2-5 MPa / s, the pressure-holding temperature is controlled at 48-50°C, and natural vitamin C powder accounting for 0.1-0.3% of the mass of the raw pulp is injected into the raw pulp; after the pressure-holding is completed, the material temperature is reduced to 20-25°C through a heat exchanger; Second pressure-raising stage: After the pressure is raised to 150 MPa at a rate of 5-8 MPa / s, the pressure-holding temperature is controlled at 40-42°C, and within 30 seconds after the pressure-holding begins, atomized tea polyphenol solution is sprayed on the original slurry with a concentration of 2-5% and a spraying amount of 0.5-1% of the original slurry volume; after the pressure-holding ends, the temperature is cooled to 15-18°C through a heat exchanger; The third pressure-raising stage: after the pressure is raised to 150 MPa at a rate of 8-10 MPa / s, the pressure-holding temperature is controlled at 30-32°C, and 0.05-0.1% of β-cyclodextrin embedding material is added when the pressure is raised to 120 MPa; after the pressure-holding is completed, the temperature is lowered to 5-10°C through a heat exchanger.

[0010] Preferably, the specific preparation process of the modified starch is: Step 1: Mix sodium alginate and water to prepare a sodium alginate slurry with a mass concentration of 3-5%, and adjust the pH value to 8-9 with a sodium hydroxide solution with a mass concentration of 2%; Step 2: Mix cassava starch and water to prepare starch milk with a mass concentration of 30-40%, add anhydrous sodium sulfate, heat to 40° C., and adjust the pH to 8-9 with a sodium hydroxide solution with a mass concentration of 2%; Step 3: Mix the sodium alginate slurry and starch milk obtained in the above steps 1 and 2 in a mass ratio of 1: (8-10) and stir evenly, slowly drop epichlorohydrin, raise the temperature to 40-60°C, react at constant temperature for 3-5 hours, drop acetic anhydride, continue to react for 1-1.5 hours, cool to room temperature, and obtain a mixture; Step 4: The mixture obtained in the above step 3 is adjusted to pH 5-6 with hydrochloric acid, and then anhydrous ethanol is added, filtered, washed, and the precipitate is collected, dried, crushed, and sieved to obtain the modified starch.

[0011] Preferably, in step 3, epichlorohydrin accounts for 0.2-0.3% of the sum of the mass of the sodium alginate slurry and the starch milk.

[0012] Preferably, in step 3, the acetic anhydride accounts for 6-8% of the sum of the mass of the sodium alginate slurry and the starch milk.

[0013] Preferably, the process of adding acetic anhydride in step 3 is divided into two stages: the first stage: dripping 50-60% of the total amount of acetic anhydride, controlling the reaction temperature to 40-45°C, and continuously stirring the reaction for 30-40 min; the second stage: dripping the remaining acetic anhydride, raising the temperature to 55-60°C, and using pulsed ultrasound to assist the reaction under nitrogen protection, with an ultrasound frequency of 28-40kHz, a pulse interval of 2s / 3s, and a reaction time of 40-50min. 10. The method for preparing a functional seabuckthorn and wolfberry composite freeze-dried solid fruit tea as described in claim 7 is characterized in that the epichlorohydrin in step 3 is added by gradient dripping in stages, specifically comprising: Initial stage: add 30-40% of the total mass of epichlorohydrin, control the reaction temperature at 40-45°C, add at a uniform speed at a stirring rate of 200-300 rpm, and the addition time is 15-20 minutes; Transition stage: add 50-60% of the remaining epichlorohydrin dropwise, raise the temperature to 50-55°C simultaneously, and switch the stirring mode alternately during the addition process, high speed 500rpm / low speed 100rpm, interval 10s, and the addition time 10-15min; Final stage: add the remaining epichlorohydrin dropwise, raise the temperature to 58-60°C, and add 0.5-1.0% of the total mass of epichlorohydrin as a phase transfer catalyst tetrabutylammonium bromide, use ultrasonic wave to assist the reaction, with a frequency of 25-35kHz, a power of 50-80W, and continue the reaction for 20-30 minutes.

[0014] The present invention has at least the following beneficial effects: First, the preparation method of the functional seabuckthorn and wolfberry composite freeze-dried solid fruit tea of ​​the present invention adopts vacuum freeze-drying technology, which retains the active ingredients of the product to the greatest extent, adds less auxiliary materials, reduces costs, adds isomaltooligosaccharides as prebiotics, helps gastrointestinal digestion, and meets the needs of modern green natural food.

[0015] Second, the present invention adopts modified starch to cross-link cassava starch and sodium alginate to form a network structure, thereby enhancing the ultra-low temperature resistance of the product, improving the taste of the product, and being suitable for all kinds of people.

[0016] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a photograph of the appearance of the seabuckthorn and wolfberry composite freeze-dried solid fruit tea prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0018] The present invention is further described in detail below in conjunction with embodiments so that those skilled in the art can implement the invention with reference to the description.

[0019] It should be noted that the experimental methods in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials are commercially available unless otherwise specified.

[0020] <Example 1> A method for preparing a functional seabuckthorn and wolfberry composite freeze-dried solid fruit tea, comprising the following specific steps: Step a, mixing sodium alginate with water to prepare a sodium alginate slurry with a mass concentration of 4%, and adjusting the pH value to 8 using a sodium hydroxide solution with a mass concentration of 2%; Step b, mixing cassava starch with water to prepare a starch milk with a mass concentration of 35%, adding anhydrous sodium sulfate, heating to 40° C., and adjusting the pH to 8 using a sodium hydroxide solution with a mass concentration of 2%; Step c, the sodium alginate slurry and starch milk are mixed and stirred in a mass ratio of 1:9, epichlorohydrin is slowly added dropwise, the temperature is raised to 50° C., the reaction is carried out at a constant temperature for 4 h, acetic anhydride is added dropwise, the reaction is continued for 1.2 h, and the mixture is cooled to room temperature to obtain a mixture; Step d, adjusting the pH of the mixture to 5 with hydrochloric acid, adding anhydrous ethanol, filtering, washing, collecting the precipitate, and drying, crushing, and sieving it to obtain modified starch for later use; Step e, washing and removing the seeds of sea buckthorn, squeezing the juice, filtering, placing in a high-pressure homogenizer, increasing the pressure to the target pressure in a continuous linear increasing manner, maintaining the pressure, and then releasing the pressure, repeating three times, wherein the target pressure is 150 MPa, the pressure holding time is 4 minutes, the pressure holding temperature is 40° C., and the pressure increasing rates of the three linear increasings are 3 MPa / s, 5 MPa / s, and 10 MPa / s, respectively, to obtain sea buckthorn puree for standby use; Step f, washing wolfberry and squeezing the juice, filtering it, placing it in a high-pressure homogenizer, increasing the pressure to the target pressure in a continuous linear increasing manner, maintaining the pressure, and then releasing the pressure, repeating three times, wherein the target pressure is 150 MPa, the pressure holding time is 4 min, the pressure holding temperature is 40° C., and the pressure increasing rates of the three linear increasings are 3 MPa / s, 5 MPa / s, and 10 MPa / s, respectively, to obtain wolfberry puree for use; Step g, uniformly mix seabuckthorn puree, wolfberry puree, modified starch, honey and isomaltooligosaccharide in a mass ratio of 1.2:1:0.15:0.1:1, pour into a mold, pre-freeze at an ultra-low temperature of -50°C for 25 h, and then dry in a vacuum freeze dryer to finally obtain the seabuckthorn and wolfberry composite freeze-dried solid fruit tea.

[0021] <Example 2> A method for preparing a functional seabuckthorn and wolfberry composite freeze-dried solid fruit tea, comprising the following specific steps: Step a, mixing sodium alginate with water to prepare a sodium alginate slurry with a mass concentration of 5%, and adjusting the pH value to 9 using a sodium hydroxide solution with a mass concentration of 2%; Step b, mixing cassava starch with water to prepare a starch milk with a mass concentration of 40%, adding anhydrous sodium sulfate, heating to 40° C., and adjusting the pH to 9 using a sodium hydroxide solution with a mass concentration of 2%; Step c, the sodium alginate slurry and starch milk are mixed and stirred in a mass ratio of 1:10, epichlorohydrin is slowly added dropwise, the temperature is raised to 60° C., the reaction is carried out at a constant temperature for 5 h, acetic anhydride is added dropwise, the reaction is continued for 1.5 h, and the mixture is cooled to room temperature to obtain a mixture; Step d, adjusting the pH of the mixture to 6 with hydrochloric acid, adding anhydrous ethanol, filtering, washing, collecting the precipitate, and drying, crushing, and sieving it to obtain modified starch for later use; Step e, washing and removing the seeds of sea buckthorn, squeezing the juice, filtering, placing in a high-pressure homogenizer, increasing the pressure to the target pressure in a continuous linear increasing manner, maintaining the pressure, and then releasing the pressure, repeating three times, wherein the target pressure is 150 MPa, the pressure holding time is 5 min, the pressure holding temperature is 50° C., and the pressure increasing rates of the three linear increasings are 5 MPa / s, 8 MPa / s, and 10 MPa / s, respectively, to obtain sea buckthorn puree for standby use; Step f, washing wolfberry and squeezing the juice, filtering it, placing it in a high-pressure homogenizer, increasing the pressure to the target pressure in a continuous linear increasing manner, maintaining the pressure, and then releasing the pressure, repeating three times, wherein the target pressure is 150 MPa, the pressure holding time is 5 min, the pressure holding temperature is 50° C., and the pressure increasing rates of the three linear increasings are 5 MPa / s, 8 MPa / s, and 10 MPa / s, respectively, to obtain wolfberry puree for use; Step g, uniformly mix seabuckthorn puree, wolfberry puree, modified starch, honey and isomaltooligosaccharide in a mass ratio of 1.5:1.4:0.2:0.12:1.2, pour into a mold, pre-freeze at an ultra-low temperature of -40°C for 30 h, and then dry in a vacuum freeze dryer to finally obtain the seabuckthorn and wolfberry composite freeze-dried solid fruit tea.

[0022] <Example 3> A method for preparing a functional seabuckthorn and wolfberry composite freeze-dried solid fruit tea, comprising the following specific steps: Step a, mixing sodium alginate with water to prepare a sodium alginate slurry with a mass concentration of 3%, and adjusting the pH value to 8 using a sodium hydroxide solution with a mass concentration of 2%; Step b, mixing cassava starch with water to prepare a starch milk with a mass concentration of 30%, adding anhydrous sodium sulfate, heating to 40° C., and adjusting the pH to 8 using a sodium hydroxide solution with a mass concentration of 2%; Step c, the sodium alginate slurry and starch milk are mixed and stirred in a mass ratio of 1:8, epichlorohydrin is slowly added dropwise, the temperature is raised to 40°C, the reaction is carried out at a constant temperature for 3 hours, acetic anhydride is added dropwise, the reaction is continued for 1 hour, and the mixture is cooled to room temperature to obtain a mixture; Step d, adjusting the pH of the mixture to 5 with hydrochloric acid, adding anhydrous ethanol, filtering, washing, collecting the precipitate, and drying, crushing, and sieving it to obtain modified starch for later use; Step e, washing and removing the seeds of sea buckthorn, squeezing the juice, filtering, placing in a high-pressure homogenizer, increasing the pressure to the target pressure in a continuous linear increasing manner, maintaining the pressure, and then releasing the pressure, repeating three times, wherein the target pressure is 150 MPa, the pressure holding time is 3 min, the pressure holding temperature is 30° C., and the pressure increasing rates of the three linear increasings are 2 MPa / s, 5 MPa / s, and 8 MPa / s, respectively, to obtain sea buckthorn puree for standby use; Step f, washing wolfberry and squeezing the juice, filtering it, placing it in a high-pressure homogenizer, increasing the pressure to the target pressure in a continuous linear increasing manner, maintaining the pressure, and then releasing the pressure, repeating three times, wherein the target pressure is 150 MPa, the pressure holding time is 3 min, the pressure holding temperature is 30° C., and the pressure increasing rates of the three linear increasings are 2 MPa / s, 5 MPa / s, and 8 MPa / s, respectively, to obtain wolfberry puree for use; Step g, uniformly mix seabuckthorn puree, wolfberry puree, modified starch, honey and isomalto-oligosaccharide in a mass ratio of 1:1:0.1:0.08:0.8, pour into a mold, pre-freeze at an ultra-low temperature of -60°C for 20 h, and then dry in a vacuum freeze dryer to finally obtain the seabuckthorn and wolfberry composite freeze-dried solid fruit tea.

[0023] <Comparative Example 1> A method for preparing a functional seabuckthorn and wolfberry composite freeze-dried solid fruit tea, which differs from Example 1 in that cassava starch is directly used as a raw material instead of modified starch, and the specific preparation process only includes steps e to g.

[0024] <Comparative Example 2> A method for preparing a functional seabuckthorn and wolfberry composite freeze-dried solid fruit tea, which is different from Example 1 in that the modified starch is prepared by cross-linking and modifying cassava starch only. The specific preparation process is as follows: Step a, mixing cassava starch and water to prepare a starch milk with a mass concentration of 30%, adding anhydrous sodium sulfate, heating to 40° C., and adjusting the pH to 8 using a sodium hydroxide solution with a mass concentration of 2%; Step b, slowly drop epichlorohydrin into the starch milk, raise the temperature to 40° C., react at constant temperature for 3 h, drop acetic anhydride, continue to react for 1 h, cool to room temperature, and obtain a mixture; Step c, adjusting the pH of the mixture to 5 with hydrochloric acid, adding anhydrous ethanol, filtering, washing, collecting the precipitate, and drying, crushing, and sieving it to obtain modified starch for later use; Step d, washing and removing the seeds of sea buckthorn, squeezing the juice, filtering, placing in a high-pressure homogenizer, increasing the pressure to the target pressure in a continuous linear increasing manner, maintaining the pressure, and then releasing the pressure, repeating three times, wherein the target pressure is 150 MPa, the pressure holding time is 3 min, the pressure holding temperature is 30° C., and the pressure increasing rates of the three linear increasings are 2 MPa / s, 5 MPa / s, and 8 MPa / s, respectively, to obtain sea buckthorn puree for standby use; Step e, washing wolfberry and squeezing the juice, filtering it, placing it in a high-pressure homogenizer, increasing the pressure to the target pressure in a continuous linear increasing manner, maintaining the pressure, and then releasing the pressure, repeating three times, wherein the target pressure is 150 MPa, the pressure holding time is 3 min, the pressure holding temperature is 30° C., and the pressure increasing rates of the three linear increasings are 2 MPa / s, 5 MPa / s, and 8 MPa / s, respectively, to obtain wolfberry puree for standby use; Step f, uniformly mix seabuckthorn puree, wolfberry puree, modified starch, honey and isomaltooligosaccharide in a mass ratio of 1:1:0.1:0.08:0.8, pour into a mold, pre-freeze at an ultra-low temperature of -60°C for 20 h, and then dry in a vacuum freeze dryer to finally obtain the seabuckthorn and wolfberry composite freeze-dried solid fruit tea.

[0025] <Comparative Example 3> A method for preparing a functional seabuckthorn and wolfberry composite freeze-dried solid fruit tea, which differs from that of Example 1 in that the mass ratio of the sodium alginate slurry to the starch emulsion in step c is 1:5.

[0026] <Comparative Example 4> A method for preparing a functional seabuckthorn and wolfberry composite freeze-dried solid fruit tea, which differs from that of Example 1 in that the mass ratio of the sodium alginate slurry to the starch emulsion in step c is 1:15.

[0027] <Comparative Example 5> A method for preparing a functional seabuckthorn and wolfberry composite freeze-dried solid fruit tea is different from that of Example 1 in that only one high-pressure homogenization is used in step e and step f.

[0028] <Freeze-thaw stability test> Various modified starches and tapioca starches used in Examples 1 to 3 and Comparative Examples 1 to 4 were dissolved in water for gelatinization, and then placed in an ultra-low temperature environment of -50°C for freezing. After being completely frozen, they were naturally thawed at room temperature. If they could be completely thawed, the freeze-thaw cycle test was continued until the sample was observed to be deteriorated. The number of freeze-thaw cycles was counted. The more freeze-thaw cycles, the better the freeze-thaw stability. The results are shown in Table 1.

[0029] Table 1 Number of freeze-thaw cycles Example 1 6 Example 2 6 Example 3 6 Comparative Example 1 1 Comparative Example 2 2 Comparative Example 3 3 Comparative Example 4 3 The results show that the modified starch prepared by composite cross-linking of cassava starch and sodium alginate in Examples 1 to 3 has the most stable network cross-linked structure and can withstand ultra-low temperatures. In Comparative Example 1, only cassava starch is used, and the ultra-low temperature resistance is the worst; in Comparative Example 2, only cassava starch is cross-linked, and the stability of its network structure is worse than that of Examples 1 to 3, so the tolerance to ultra-low temperatures is worse than that of Examples 1 to 3. The content of sodium alginate slurry in Comparative Example 3 is higher, and the content of sodium alginate slurry in Comparative Example 4 is lower, and its cross-linked structure is also worse than the structural stability of the modified starch in Examples 1 to 3, so the freeze-thaw stability is also poor.

[0030] <Product volume density and rehydration time test> The seabuckthorn and wolfberry composite freeze-dried solid fruit tea products prepared in Examples 1 to 3 and Comparative Examples 1 to 5 were taken, and their volume density and rehydration time were measured respectively. The results are shown in Table 2 below.

[0031] Table 2 <![CDATA[Bulk density (g / cm 3 )]]> Rehydration time(s) Example 1 0.51 36.2 Example 2 0.58 37.5 Example 3 0.52 36.6 Comparative Example 1 0.96 40.8 Comparative Example 2 0.83 40.3 Comparative Example 3 0.66 37.7 Comparative Example 4 0.70 38.1 Comparative Example 5 0.59 37.9 The results show that the seabuckthorn and wolfberry composite freeze-dried solid fruit tea prepared by the method of the present invention in Examples 1 to 3 has good ultra-low temperature resistance and a small volume density, indicating that it has a high porosity, contains more pores, water can easily penetrate, has a short rehydration time, has good wettability, can melt in the mouth, and is convenient for direct consumption. In Comparative Example 1, cassava starch is directly used. After ultra-low temperature freeze-drying, the pore structure is easy to collapse, which reduces the pores of the product. Therefore, the bulk density is large, and the rehydration time is long, which affects the taste of the product. Although the cassava starch is cross-linked in Comparative Example 2, the ultra-low temperature still has a great influence on its cross-linking structure, making the pores of the product smaller and less than those of Examples 1-3. Therefore, the bulk density is large, and the rehydration time is long, which affects the taste of the product. The content of sodium alginate slurry in Comparative Example 3 is high, and the content of sodium alginate slurry in Comparative Example 4 is low. The ultra-low temperature resistance of the modified starch is lower than that of Examples 1-3. Therefore, the bulk density of the products of Comparative Examples 3 and Comparative Examples 4 is larger than that of Examples 1-3, and the rehydration time is longer than that of Examples 1-3. The bulk density of the product obtained in Comparative Example 5 is not much different from that of Examples 1-3, but because it only uses one high-pressure homogenization process, the uniformity of seabuckthorn pulp and wolfberry pulp is poor, and the rehydration time is longer than that of Examples 1-3, which affects the taste of the product.

[0032] <Sensory Evaluation> The seabuckthorn and wolfberry composite freeze-dried solid fruit tea products prepared in Examples 1 to 3 and Comparative Examples 1 to 5 were subjected to sensory evaluation and comparative analysis, wherein the sensory evaluation score table is shown in Table 3.

[0033] Table 3 project Points Scoring Criteria Color 10 Refers to the color of the product. If the main body is orange and the color is uniform, it is 8 to 10 points; if the color is too dark or too light, and the color distribution is uneven, it is 6 to 8 points; if there are impurities and different colors, it is 0 to 6 points. Porosity of cut surface tissue 30 Refers to the size and uniformity of the pore structure of the product cross section. A uniform pore structure is 22-30 points; an uneven pore structure is 14-22 points; and a collapsed pore structure is 0-14 points. Taste 30 Refers to the taste of the product. The taste is sweet, sour, crispy and has no peculiar smell, with a score of 22-30; the taste is sour and hard, with a score of 14-22; the taste is very hard and has a peculiar smell, with a score of 0-14. Swallowability 30 Refers to the degree of smoothness when chewing and swallowing the product. If there is no obvious residue after swallowing, and the throat is smooth and has no residue, it is 22-30 points; if there is slight residue when swallowing, it is 14-22 points; if there is obvious residue when swallowing, and the swallowing sensation is poor, it is 0-14 points. Ten persons (five men and five women) who had received professional training in sensory evaluation were selected to conduct sensory evaluation on the color, pore state of the cut surface tissue, taste, mouthfeel and swallowability of the seabuckthorn and wolfberry composite freeze-dried solid fruit tea products prepared in Examples 1 to 3 and Comparative Examples 1 to 5, and score them. The results are shown in Table 4.

[0034] Table 4 Color Porosity of cut surface tissue Taste Swallowability Total sensory score Example 1 8.5 28.8 29.0 28.6 94.9 Example 2 8.5 28.5 28.5 28.5 94.0 Example 3 8.5 28.6 28.5 28.5 94.1 Comparative Example 1 7.2 10.5 12.5 10.5 40.7 Comparative Example 2 6.8 14.5 15.6 16.5 53.4 Comparative Example 3 5.8 16.8 20.2 19.8 62.8 Comparative Example 4 6.6 15.5 20.5 20.0 62.6 Comparative Example 5 5.5 26.5 24.5 15.5 72.0 The results show that the sensory evaluation of the products prepared in Examples 1 to 3 is the best. In Comparative Example 1, cassava starch is directly used. After ultra-low temperature freeze drying, the pore structure is easy to collapse, making the product taste hard and the swallowing sense poor; although the cassava starch is cross-linked and improved in Comparative Example 2, the ultra-low temperature still has a great impact on its cross-linking structure, causing the pore structure of the product to collapse, affecting the edible taste of the product; the content of sodium alginate slurry in Comparative Example 3 is high, and the content of sodium alginate slurry in Comparative Example 4 is low, and the ultra-low temperature resistance of its modified starch is lower than that of Examples 1 to 3, so the sensory evaluation of the products of Comparative Examples 3 and Comparative Examples 4 is worse than that of Examples 1 to 3; in Comparative Example 5, since only one high-pressure homogenization process is used, the uniformity of sea buckthorn pulp and wolfberry pulp is poor, containing slight residues, affecting the edible taste of the product.

[0035] According to one embodiment of the present invention, a preparation process of seabuckthorn puree in a method for preparing functional seabuckthorn and wolfberry composite freeze-dried solid fruit tea is involved. The process ensures that the seabuckthorn puree retains nutrients while killing microorganisms through systematic treatment, providing high-quality raw materials for the subsequent production of freeze-dried fruit tea. Fresh seabuckthorn fruits are selected as raw materials and cleaned with a countercurrent cleaning machine. During the cleaning process, the water temperature is controlled at 25-30°C, the water flow rate is 5-8m³ / h, and the mud and impurities on the surface of the fruit are removed by continuous spraying. After cleaning, a drum-type seed remover (speed 15-20rpm) is used to separate the pulp and the core, and the seed removal rate must reach more than 99% to avoid the core from breaking and affecting the taste of the puree.

[0036] The deseeded pulp is squeezed with a double screw press, with a squeezing pressure of 0.8-1.2MPa, a rotation speed of 30-50rpm, and a juice yield of ≥75%. During the juicing process, 0.1% (w / w) pectinase (enzyme activity ≥100,000 U / g) is added and enzymolyzed at 45°C for 30 minutes to increase the juice yield and clarity. The resulting juice is coarsely filtered through a 200-mesh stainless steel filter and finely filtered through a 0.45μm microporous membrane to ensure that the filtrate transmittance is ≥90%.

[0037] A plunger-type high-pressure homogenizer (model: GEA Niro Soavi NS1001L) is used, equipped with a three-stage homogenizing valve, with a maximum working pressure of 150MPa. The material is preheated to 30-50°C through a jacketed heat exchanger, and a constant temperature is maintained during the pressure holding stage.

[0038] The first stage (cell membrane destruction): the pressure is increased to 30-40MPa at a rate of 2-5MPa / s, and maintained at 30-50℃ for 3-5 minutes. In this stage, static pressure is used to increase the permeability of microbial cell membranes, and some microorganisms lose their activity.

[0039] The second stage (cell wall breaking): the pressure is increased to 70-80MPa at a rate of 5-8MPa / s and maintained for 3-5 minutes. The peptidoglycan layer of Gram-positive bacteria (such as Staphylococcus aureus) is destroyed through the shear force field, further killing the microorganisms.

[0040] The third stage (spore killing): the pressure is increased to 150MPa at a rate of 8-10MPa / s and maintained for 3-5 minutes. The shock wave generated by the transient cavitation effect can effectively kill heat-resistant spores (such as Bacillus subtilis).

[0041] After the three-stage pressure increase is completed, the material is immediately cooled to below 10°C through a plate heat exchanger, with a cooling rate of ≥5°C / s. Repeat the pressure increase-pressure maintenance-pressure relief cycle three times, and the total processing time is controlled within 20-30 minutes.

[0042] Quality control indicators: 1. Microbiological indicators: total colony count ≤100CFU / mL, coliform group ≤3MPN / 100mL, pathogenic bacteria (Salmonella, Staphylococcus aureus) not detected. 2. Nutritional indicators: vitamin C retention rate ≥85%, flavonoid retention rate ≥90%, soluble solid content ≥12°Brix. 3. Sensory indicators: color is orange-yellow and uniform, taste is moderately sweet and sour, state is clear and transparent, and there are no impurities visible to the naked eye.

[0043] Process advantages: 1. Sterilization effect: three-stage gradient pressure increase combined with multiple cycle treatment, sterilization rate ≥ 99.9%, meeting commercial aseptic requirements. 2. Nutrition retention: segmented pressure increase combined with low temperature pressure maintenance (30-50℃) reduces the damage of high temperature to heat-sensitive ingredients, and the vitamin C retention rate is increased by more than 30% compared with traditional pasteurization. 3. Industrial adaptation: The continuous homogenization system has a production capacity of up to 500L / h, which is suitable for large-scale production.

[0044] According to another embodiment of the present invention, microbial detection is performed on sea buckthorn puree before high-pressure homogenization and sterilization, and the pressure-boosting process is adjusted according to the detection results to achieve a balance between precise sterilization and nutrient retention.

[0045] Take 10 mL of seabuckthorn filtrate and inoculate it into different culture media by plate pouring method: eosin-methylene blue medium (for detecting Escherichia coli), blood plate medium (for detecting Staphylococcus aureus), malt extract medium (for detecting yeast), potato dextrose agar medium (for detecting mold). Culture conditions: bacteria are cultured at 37°C for 48 hours and fungi are cultured at 28°C for 72 hours.

[0046] The type and amount of contaminating bacteria can be determined through colony morphology observation, Gram staining and biochemical tests (such as oxidase test, catalase test), combined with 16SrRNA gene sequencing (for bacteria) and ITS region sequencing (for fungi).

[0047] Optimization of boosting process based on strains: 1. Single strain treatment: Escherichia coli: First stage: 3-4MPa / s boost to 50MPa, 40℃ for 2 minutes; second stage: 5-6MPa / s boost to 100MPa, 40℃ for 2 minutes; third stage: 8-9MPa / s boost to 150MPa, 40℃ for 4 minutes. Staphylococcus aureus: First stage: 4-5MPa / s boost to 60MPa, 40℃ for 2 minutes; second stage: 6-7MPa / s boost to 110MPa, 40℃ for 2 minutes; third stage: 9-10MPa / s boost to 150MPa, 40℃ for 4 minutes. Yeast: First stage: 2-3MPa / s to 40MPa, 40℃ for 2 minutes; Second stage: 4-5MPa / s to 90MPa, 40℃ for 2 minutes; Third stage: 7-8MPa / s to 150MPa, 40℃ for 4 minutes. Mold: First stage: 3-4MPa / s to 55MPa, 40℃ for 2 minutes; Second stage: 5-6MPa / s to 105MPa, 40℃ for 2 minutes; Third stage: 8-9MPa / s to 150MPa, 40℃ for 4 minutes. 2. Treatment of mixed bacterial species: If two or more bacterial species are detected, a comprehensive pressure-boosting scheme is adopted: the first stage: increase the pressure from 3-4MPa / s to 55MPa, and maintain the pressure at 40℃ for 2 minutes; the second stage: increase the pressure from 5-6MPa / s to 105MPa, and maintain the pressure at 40℃ for 2 minutes; the third stage: increase the pressure from 8-9MPa / s to 150MPa, and maintain the pressure at 40℃ for 4 minutes.

[0048] Process verification: 1. Sterilization rate test: Take samples after treatment and use the plate count method to verify the sterilization effect. The target sterilization rate is ≥99.9%. 2. Nutritional component analysis: Use high performance liquid chromatography (HPLC) to determine the content of vitamin C and flavonoids. The retention rate must be ≥88% and ≥92%. Technical advantages: 1. Precise sterilization: Design the boost curve according to the physiological characteristics of different strains to improve the sterilization efficiency. 2. Nutritional protection: The pressure holding temperature is fixed at 40°C to reduce the damage of high temperature to heat-sensitive components. 3. Process flexibility: The boost parameters can be adjusted according to the actual test results to adapt to the microbial contamination of different raw material batches.

[0049] According to another embodiment of the present invention, the preparation process of wolfberry puree and sea buckthorn puree in the preparation method of functional sea buckthorn and wolfberry composite freeze-dried solid fruit tea is described in detail, focusing on the application of high-pressure homogenization combined sterilization technology in the production of the two purees.

[0050] Ningxia wolfberry dried fruit is selected as raw material, and after being removed from the surface impurities by a washing machine (water temperature 20-25℃), it is crushed to a particle size of ≤5mm by a hammer crusher. The juice is squeezed by a screw press, and the juice yield is ≥65%. The filtrate is coarsely filtered through a 100-mesh filter and then finely filtered through a 0.65μm ceramic membrane.

[0051] The filtrate was placed in a high-pressure homogenizer (model: GEA Niro Soavi NS1001L) and processed according to the following parameters: first stage: 2-5MPa / s to 30-40MPa, 30-50℃ pressure maintained for 3-5 minutes; second stage: 5-8MPa / s to 70-80MPa, 30-50℃ pressure maintained for 3-5 minutes; third stage: 8-10MPa / s to 150MPa, 30-50℃ pressure maintained for 3-5 minutes. Repeat the cycle three times, and cool to below 10℃ through a plate heat exchanger after each pressure relief.

[0052] The preparation of sea buckthorn puree includes the steps of raw material pretreatment, i.e., washing, seed removal, juice extraction and filtration. The same high-pressure homogenization parameters as those of wolfberry puree are used: three-stage gradient pressure increase to 150MPa, with rates of 2-5MPa / s, 5-8MPa / s, and 8-10MPa / s respectively; after each pressure increase, the pressure is maintained at 30-50℃ for 3-5 minutes, and the cycle is repeated three times.

[0053] Quality control: 1. Microbiological indicators: total colony count ≤100CFU / mL, coliform group ≤3MPN / 100mL, no pathogenic bacteria detected. 2. Nutritional indicators: Lycium barbarum puree: Lycium barbarum polysaccharide retention rate ≥85%, carotenoid retention rate ≥90%; Seabuckthorn puree: vitamin C retention rate ≥85%, flavonoid retention rate ≥90%. 3. Sensory indicators: Lycium barbarum puree: orange-red color, sweet and slightly sour taste; Seabuckthorn puree: orange-yellow color, sweet and sour taste.

[0054] Process advantages: 1. Strong versatility: The same high-pressure homogenization process is applicable to the processing of seabuckthorn and wolfberry purees. 2. High efficiency and energy saving: Continuous processing reduces energy consumption and increases production efficiency by 40% compared to intermittent processing. 3. Product stability: The particle size of the puree after homogenization is ≤2μm and can be stably stored for 72 hours at room temperature.

[0055] According to another embodiment, the sterilization effect and nutrient retention rate of seabuckthorn / wolfberry puree are further improved through the coordinated treatment of three pressure-boosting stages.

[0056] The first pressurization stage: 1. Process parameters: pressurization rate: 2-5MPa / s to 150MPa; holding temperature: 48-50℃, holding time 3-5 minutes; synergistic treatment: inject 0.1-0.3% natural vitamin C powder.

[0057] Operation process: After the raw pulp enters the high-pressure homogenizer, the pressure is increased to 150MPa at 2-5MPa / s. During the pressure holding period, the natural vitamin C powder is evenly injected through a metering pump, and the high-pressure environment is used to promote its dissolution and dispersion. After the pressure holding is completed, the temperature is cooled to 20-25℃ through a heat exchanger.

[0058] Mechanism of action: Vitamin C acts as an antioxidant, inhibiting the oxidative damage to nutrients caused by free radicals produced under high pressure; high temperature (48-50°C) and high pressure work synergistically to enhance the killing effect on thermophilic microorganisms.

[0059] The second pressurization stage: pressurization rate: 5-8MPa / s to 150MPa; holding temperature: 40-42°C, holding time: 3-5 minutes; coordinated treatment: spraying 2-5% tea polyphenols solution (volume fraction 0.5-1%).

[0060] Operation process: After the pressure is increased to 150MPa, within 30 seconds of the start of pressure maintenance, spray the tea polyphenol solution onto the original slurry through the atomizing nozzle. After the pressure maintenance is completed, cool down to 15-18℃.

[0061] Mechanism of action: Tea polyphenols have antibacterial activity and can destroy the cell membrane structure of microorganisms; under a 40-42°C environment, tea polyphenols and high pressure work synergistically to enhance the killing effect on Gram-negative bacteria.

[0062] The third pressure-increasing stage: pressure-increasing rate: 8-10MPa / s to 150MPa; pressure-holding temperature: 30-32°C, pressure-holding time: 3-5 minutes; coordinated treatment: adding 0.05-0.1% β-cyclodextrin embedding material when the pressure is increased to 120MPa.

[0063] Operation process: When the pressure reaches 120MPa, add β-cyclodextrin embedding material (such as embedding volatile aroma components) through the feed port, and continue to increase the pressure to 150MPa. After the pressure is maintained, cool down to 5-10℃.

[0064] Mechanism of action: β-cyclodextrin can embed heat-sensitive components and reduce degradation under high pressure; the low temperature (30-32°C) pressure holding stage further inhibits enzyme activity and extends the shelf life of the original paste.

[0065] Process verification: 1. Sterilization rate: The total colony count of the treated puree is ≤50CFU / mL, which is 50% lower than that of the conventional process. 2. Nutritional retention rate: Vitamin C retention rate ≥90% (sea buckthorn puree); Lycium barbarum polysaccharide retention rate ≥92% (lycium barbarum puree). 3. Sensory evaluation: There is no significant difference in color and flavor compared with the conventional process, but the rehydration property is improved by 15%.

[0066] This implementation method achieves multiple effects of sterilization, anti-oxidation, and flavor protection through temperature gradient control and functional ingredient addition. The addition of natural vitamin C and β-cyclodextrin specifically improves the nutritional value of the product. The stepped cooling design reduces the load of the heat exchanger and saves 15% energy compared to the traditional process.

[0067] According to another embodiment, the synthesis process optimization of modified starch in the preparation of functional seabuckthorn and wolfberry composite freeze-dried solid fruit tea is involved, focusing on describing the staged addition method of acetic anhydride to enhance the cross-linking effect and product performance of the modified starch.

[0068] Raw material pretreatment: Sodium alginate slurry: Weigh sodium alginate and mix with water to make a slurry with a mass concentration of 3-5%, and adjust the pH to 8-9 with 2% sodium hydroxide solution. Cassava starch milk: Mix cassava starch with water to make a starch milk with a mass concentration of 30-40%, add anhydrous sodium sulfate, heat to 40°C, and adjust the pH to 8-9.

[0069] Cross-linking reaction: Mix sodium alginate slurry and starch milk in a mass ratio of 1:8-10, add epichlorohydrin (accounting for 0.2-0.3% of the total mass), heat to 40-60°C and react for 3-5 hours, then add acetic anhydride (accounting for 6-8% of the total mass) and continue to react for 1-1.5 hours.

[0070] Optimization of acetic anhydride addition in stages: 1. The first stage: low temperature rate-controlled reaction, operation steps: ① At 40-45℃, add 50-60% of the total amount of acetic anhydride dropwise at a uniform speed, and control the addition time within 15-20 minutes.

[0071] ② Maintain the stirring rate at 200-300 rpm and continue the reaction for 30-40 minutes.

[0072] Mechanism of action: Under low temperature conditions, the esterification reaction rate of acetic anhydride and starch hydroxyl groups is slow. Adding it in stages can avoid side reactions (such as etherification reactions) caused by excessive local concentration and reduce heat accumulation.

[0073] 2. The second stage: high temperature ultrasound assisted reaction, operation steps: ① Raise the reaction temperature to 55-60°C and add the remaining 40-50% of acetic anhydride dropwise.

[0074] ② Introduce nitrogen (flow rate 0.5-1 L / min) to form an inert atmosphere and start the pulsed ultrasonic generator (frequency 28-40kHz, pulse interval 2s / 3s).

[0075] ③ Keep the reaction going for 40-50 minutes, maintaining a stirring rate of 150-200 rpm.

[0076] Mechanism of action: High temperature accelerates the esterification reaction, and nitrogen protection prevents the formation of oxidation by-products; the cavitation effect of ultrasound can destroy the mass transfer resistance in the reaction system, promote the uniform dispersion of acetic anhydride, and improve the cross-linking efficiency.

[0077] Post-treatment process: 1. Neutralization and precipitation: After the reaction is completed, adjust the pH to 5-6 with hydrochloric acid, add anhydrous ethanol (the volume is 1-1.5 times of the reaction solution), let it stand for 1 hour and then filter. 2. Washing and drying: The precipitate is washed 3 times with deionized water, placed in a vacuum drying oven (60℃, -0.1MPa) for 8 hours, and crushed through an 80-mesh sieve.

[0078] Performance verification: 1. Cross-linking degree test: The cross-linking degree of the modified starch with acetic anhydride added in stages reached 1.2-1.5% by complexometric titration, which is 20% higher than that of the one-time addition. 2. Freeze-thaw stability: After 6 freeze-thaw cycles (-50℃ / room temperature), the paste remained stable without obvious water precipitation (compared with the one-time addition group, which separated after only 2 cycles). 3. Application effect: The modified starch was used in freeze-dried fruit tea, with a product volume density of 0.51-0.58 g / cm³, a rehydration time of 36.2-37.5 seconds, and a crispy taste without lumps.

[0079] Process advantages: 1. Reaction controllability: staged temperature-controlled dripping avoids violent reactions and reduces the generation of by-products. 2. Resource utilization: Ultrasonic assistance increases the utilization rate of acetic anhydride to more than 95%, reducing raw material consumption by 10% compared with traditional processes. 3. Product performance improvement: The cross-linking structure is more uniform, and the ultra-low temperature resistance is significantly enhanced, which meets the requirements of the freeze-drying process.

[0080] According to another embodiment of the present invention, it involves the optimization of the synthesis process of modified starch in the preparation of functional seabuckthorn and wolfberry composite freeze-dried solid fruit tea, focusing on describing the staged gradient dripping method of epichlorohydrin to improve the cross-linking reaction efficiency and product performance.

[0081] Raw material pretreatment: Sodium alginate slurry: mass concentration 3-5%, pH 8-9. Cassava starch milk: mass concentration 30-40%, pH 8-9, containing anhydrous sodium sulfate.

[0082] Cross-linking reaction: After the sodium alginate slurry is mixed with starch milk, epichlorohydrin (accounting for 0.2-0.3% of the total mass) is added, the temperature is raised to 40-60°C and the reaction is carried out for 3-5 hours, and then acetic anhydride (accounting for 6-8% of the total mass) is added and the reaction is continued for 1-1.5 hours.

[0083] Optimization of epichlorohydrin stepwise gradient addition: 1. Initial stage: low temperature and uniform dripping, operation steps: ① At 40-45°C, stir at 200-300 rpm and uniformly add 30-40% of the total mass of epichlorohydrin over 15-20 minutes.

[0084] ② After the addition is completed, maintain the temperature and stirring rate and continue the reaction for 30 minutes.

[0085] Mechanism of action: Under low temperature conditions, the etherification reaction rate of epichlorohydrin and starch hydroxyl groups can be controlled, and uniform dripping can avoid excessive local concentrations that may lead to side reactions (such as hydrolysis).

[0086] 2. Transition stage: heating and stirring alternately, operation steps: ① Raise the temperature to 50-55℃ and add 50-60% of the remaining epichlorohydrin dropwise over 10-15 minutes.

[0087] ② During the dropwise addition process, alternately switch the stirring speed: high speed 500 rpm (10 seconds) → low speed 100 rpm (10 seconds), and repeat the cycle.

[0088] Mechanism of action: Heating accelerates the reaction, alternating stirring destroys the mass transfer boundary layer and promotes the diffusion of epichlorohydrin; high-speed stirring enhances shear force, and low-speed stirring reduces mechanical shear damage to starch granules.

[0089] 3. Final stage: high temperature ultrasonic catalysis, operation steps: ① Raise the temperature to 58-60℃, add the remaining epichlorohydrin dropwise, and at the same time add 0.5-1.0% tetrabutylammonium bromide (based on the total mass of epichlorohydrin).

[0090] ② Start the ultrasonic generator (frequency 25-35kHz, power 50-80W) and continue the reaction for 20-30 minutes.

[0091] Mechanism of action: High temperature promotes the ring-opening reaction of epichlorohydrin, and the phase transfer catalyst improves the mass transfer efficiency between the aqueous phase and the organic phase; the ultrasonic cavitation effect enhances the reaction active sites and shortens the reaction time by more than 30%.

[0092] Post-treatment process: 1. Neutralization and precipitation: After the reaction is completed, adjust the pH to 5-6 and add anhydrous ethanol for precipitation. 2. Washing and drying: The precipitate is washed, vacuum dried, crushed and sieved.

[0093] Performance verification: 1. Cross-linking degree test: The cross-linking degree of modified starch with epichlorohydrin added in stages reaches 1.3-1.6%, which is 30% higher than that of one-time addition. 2. Temperature stability: The gelatinization temperature is 15-20℃ higher than that of native starch, which is suitable for ultra-low temperature environment in freeze-drying process. 3. Application effect: When using this modified starch in freeze-dried fruit tea, the product porosity is increased by 25%, the rehydration time is shortened to 36.2 seconds, and the crispness of the taste is increased by 15%.

[0094] Process advantages: 1. Improved reaction efficiency: The phased gradient addition makes the utilization rate of epichlorohydrin reach more than 92%, which is 15% higher than the traditional process. 2. Product uniformity: Ultrasonic assistance and alternating stirring ensure uniform cross-linking and avoid local overreaction. 3. Cost reduction: The reaction time is shortened, the energy consumption is reduced by 20%, and the catalyst dosage is low (0.5-1.0%).

[0095] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and implementation modes. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and shown and described herein.

Claims

1. A method for preparing a functional seabuckthorn and wolfberry composite freeze-dried solid fruit tea, characterized in that: The following steps are involved: The sea buckthorn puree, wolfberry puree, modified starch, honey and isomaltooligosaccharide are uniformly mixed in a mass ratio of (1-1.5): (1-1.4): (0.1-0.2): (0.08-0.12): (0.8-1.2), poured into a mold, pre-frozen at an ultra-low temperature of -60°C to -40°C for 20-30 h, and then dried in a vacuum freeze dryer to finally obtain the sea buckthorn and wolfberry composite freeze-dried solid fruit tea; wherein the modified starch is prepared by composite cross-linking of cassava starch and sodium alginate.

2. The method for preparing a functional seabuckthorn and wolfberry composite freeze-dried solid fruit tea according to claim 1, characterized in that: The preparation of the seabuckthorn puree comprises the following steps: Wash and remove the seeds of sea buckthorn, squeeze the juice and filter it; The high-pressure homogenization combined sterilization process is adopted: the filtrate is placed in a high-pressure homogenizer, and the pressure is increased to 150MPa in three stages in a continuous linear pressure increase mode, and the pressure increase rates are 2-5MPa / s, 5-8MPa / s, and 8-10MPa / s, respectively. After each pressure increase, the pressure is maintained at 30-50℃ for 3-5 minutes, and then the pressure is released. The above pressure increase-pressure maintenance-pressure release process is repeated three times; After the above treatment, sea buckthorn puree is obtained.

3. The method for preparing a functional seabuckthorn and wolfberry composite freeze-dried solid fruit tea according to claim 2, characterized in that: Before adopting the high-pressure homogenization combined sterilization process, the seabuckthorn puree is first tested for microorganisms to determine the contaminating bacteria species, and then the specific pressure increase method is determined according to the different bacteria species, as follows: If E. coli is detected in the seabuckthorn puree, the pressure is increased to 50MPa at a rate of 3-4MPa / s for the first time and maintained for 2 minutes. During this stage, the cell wall and cell membrane of E. coli are gradually damaged by using relatively mild pressure and pressure increase rate; the second time, the pressure is increased from 50MPa to 100MPa at a rate of 5-6MPa / s and maintained for 2 minutes to further destroy the protein and nucleic acid structure inside E. coli; the third time, the pressure is increased from 100MPa to 150MPa at a rate of 8-9MPa / s and maintained for 4 minutes; If the presence of Staphylococcus aureus is detected, the pressure is first increased at a rate of 4-5MPa / s to 60MPa and maintained for 2 minutes. This rate and pressure can initially act on the tough cell wall of Staphylococcus aureus; the second time, the pressure is increased from 60MPa to 110MPa at a rate of 6-7MPa / s and maintained for 2 minutes to enhance the damage to its cell wall and internal structure; the third time, the pressure is increased from 110MPa to 150MPa at a rate of 9-10MPa / s and maintained for 4 minutes; If yeast is detected, the pressure is increased to 40MPa at a rate of 2-3MPa / s for the first time and maintained for 2 minutes. The pressure is slowly increased to change the cell membrane permeability of the yeast. The second time, the pressure is increased from 40MPa to 90MPa at a rate of 4-5MPa / s and maintained for 2 minutes to further affect the metabolism and reproduction of the yeast. The third time, the pressure is increased from 90MPa to 150MPa at a rate of 7-8MPa / s and maintained for 4 minutes. If mold is detected, the pressure is first increased at a rate of 3-4MPa / s to 55MPa and maintained for 2 minutes to cause certain damage to the mycelium and spores of the mold; the second time, the pressure is increased from 55MPa to 105MPa at a rate of 5-6MPa / s and maintained for 2 minutes to further damage the mold structure; the third time, the pressure is increased from 105MPa to 150MPa at a rate of 8-9MPa / s and maintained for 4 minutes; If at least two of the above strains are detected, the following comprehensive pressure increase method is used: the first pressure increase is from 3-4MPa / s to 55MPa, and the pressure is maintained for 2 minutes; the second pressure increase is from 55MPa to 105MPa at a rate of 5-6MPa / s, and the pressure is maintained for 2 minutes; the third pressure increase is from 105MPa to 150MPa at a rate of 8-9MPa / s, and the pressure is maintained for 4 minutes; The pressure is maintained at 40°C after each pressure increase. After the above treatment, sea buckthorn puree is obtained, and the sterilization rate of the corresponding bacteria can be achieved ≥99.9%, while the vitamin C retention rate is ≥88% and the flavonoid retention rate is ≥92%.

4. The method for preparing a functional seabuckthorn and wolfberry composite freeze-dried solid fruit tea according to claim 1, characterized in that: The wolfberry puree is prepared by washing wolfberries, squeezing out juice, filtering, homogenizing, and sterilizing; the seabuckthorn puree is prepared by washing seabuckthorn, squeezing out juice, filtering, homogenizing, and sterilizing; The homogenization and sterilization process adopts high-pressure homogenization combined with sterilization, and the specific steps are: placing sea buckthorn puree or wolfberry puree in a high-pressure homogenizer, increasing the pressure to the target pressure in a continuous linear pressure-increasing manner, maintaining the pressure, and then releasing the pressure, repeating three times, wherein the target pressure is 150 MPa, the pressure-maintaining time is 3-5 min, and the pressure-maintaining temperature is 30-50°C; The pressure increasing rates of the three linear pressure increasing processes are 2~5 MPa / s, 5~8 MPa / s, and 8~10 MPa / s, respectively.

5. The method for preparing a functional seabuckthorn and wolfberry composite freeze-dried solid fruit tea according to claim 4, characterized in that: The following coordinated processing is performed during the three-step linear boost process: The first pressure-raising stage: After the pressure is raised to 150 MPa at a rate of 2-5 MPa / s, the pressure-holding temperature is controlled at 48-50°C, and natural vitamin C powder accounting for 0.1-0.3% of the mass of the raw pulp is injected into the raw pulp; after the pressure-holding is completed, the material temperature is reduced to 20-25°C through a heat exchanger; Second pressure-raising stage: After the pressure is raised to 150 MPa at a rate of 5-8 MPa / s, the pressure-holding temperature is controlled at 40-42°C, and within 30 seconds after the pressure-holding begins, atomized tea polyphenol solution is sprayed on the original slurry with a concentration of 2-5% and a spraying amount of 0.5-1% of the original slurry volume; after the pressure-holding ends, the temperature is cooled to 15-18°C through a heat exchanger; The third pressure-raising stage: after the pressure is raised to 150 MPa at a rate of 8-10 MPa / s, the pressure-holding temperature is controlled at 30-32°C, and 0.05-0.1% of β-cyclodextrin embedding material is added when the pressure is raised to 120 MPa; after the pressure-holding is completed, the temperature is lowered to 5-10°C through a heat exchanger.

6. The method for preparing a functional seabuckthorn and wolfberry composite freeze-dried solid fruit tea according to claim 1, characterized in that: The specific preparation process of the modified starch is: Step 1: Mix sodium alginate and water to prepare a sodium alginate slurry with a mass concentration of 3-5%, and adjust the pH value to 8-9 with a sodium hydroxide solution with a mass concentration of 2%; Step 2: Mix cassava starch and water to prepare starch milk with a mass concentration of 30-40%, add anhydrous sodium sulfate, heat to 40° C., and adjust the pH to 8-9 with a sodium hydroxide solution with a mass concentration of 2%; Step 3: Mix the sodium alginate slurry and starch milk obtained in the above steps 1 and 2 in a mass ratio of 1: (8-10) and stir evenly, slowly drop epichlorohydrin, raise the temperature to 40-60°C, react at constant temperature for 3-5 hours, drop acetic anhydride, continue to react for 1-1.5 hours, cool to room temperature, and obtain a mixture; Step 4: The mixture obtained in the above step 3 is adjusted to pH 5-6 with hydrochloric acid, and then anhydrous ethanol is added, filtered, washed, and the precipitate is collected, dried, crushed, and sieved to obtain the modified starch.

7. The method for preparing the functional seabuckthorn and wolfberry composite freeze-dried solid fruit tea according to claim 6, characterized in that: In the step 3, epichlorohydrin accounts for 0.2-0.3% of the total mass of the sodium alginate slurry and the starch milk.

8. The method for preparing the functional seabuckthorn and wolfberry composite freeze-dried solid fruit tea according to claim 6, characterized in that: In the step 3, the acetic anhydride accounts for 6-8% of the total mass of the sodium alginate slurry and the starch milk.

9. The method for preparing the functional seabuckthorn and wolfberry composite freeze-dried solid fruit tea according to claim 8, characterized in that: The process of adding acetic anhydride in step three is divided into two stages: the first stage: adding 50-60% of the total amount of acetic anhydride, controlling the reaction temperature to 40-45°C, and continuously stirring the reaction for 30-40 min; the second stage: adding the remaining acetic anhydride, raising the temperature to 55-60°C, and using pulsed ultrasound to assist the reaction under nitrogen protection, with an ultrasonic frequency of 28-40kHz, a pulse interval of 2s / 3s, and a reaction time of 40-50min.

10. The method for preparing the functional seabuckthorn and wolfberry composite freeze-dried solid fruit tea according to claim 7, characterized in that: The epichlorohydrin in step 3 is added dropwise in stages, specifically comprising: Initial stage: add 30-40% of the total mass of epichlorohydrin, control the reaction temperature at 40-45°C, add at a uniform speed at a stirring rate of 200-300 rpm, and the addition time is 15-20 minutes; Transition stage: add 50-60% of the remaining epichlorohydrin dropwise, raise the temperature to 50-55°C simultaneously, and switch the stirring mode alternately during the addition process, high speed 500rpm / low speed 100rpm, interval 10s, and the addition time 10-15min; Final stage: add the remaining epichlorohydrin dropwise, raise the temperature to 58-60°C, and add 0.5-1.0% of the total mass of epichlorohydrin as a phase transfer catalyst tetrabutylammonium bromide, use ultrasonic wave to assist the reaction, with a frequency of 25-35kHz, a power of 50-80W, and continue the reaction for 20-30 minutes.

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