Method for preparing instant freeze-dried dendrobium huoshanense by calcium salt dipping in cooperation with vacuum freeze-drying

Abstract

The invention discloses a method for preparing instant freeze-dried dendrobium huoshanense by calcium salt dipping and vacuum freeze-drying. The method comprises the following steps: sorting fresh stems of dendrobium huoshanense, cleaning, airing, pre-cutting, calcium salt dipping, vacuum freeze-drying, vacuum nitrogen-filled packaging and the like. The freeze-dried dendrobium (strips) obtained by the method are ready-to-eat, bright green in color, crisp and delicious, rich in active substance retention, and convenient to store and carry. In addition, the freeze-dried dendrobium nobile strips can also be ground into powder and brewed or rehydrated and juiced for eating. The freeze-dried powder is brewed by adding water, has no caking, fresh taste and rich colloid, and the digestion, absorption and utilization rate of active polysaccharides is high; the freeze-dried dendrobium huoshanense strips are high in rehydration property and can be squeezed by adding water to form dendrobium juice which is fragrant, natural and smooth in taste, the polysaccharide dissolution rate of the freeze-dried dendrobium huoshanense strips is remarkably increased compared with that of fresh strips which are directly squeezed, and the freeze-dried dendrobium huoshanense strips have important significance in development of instant dendrobium huoshanense health preserving products.

Description

Technical Field

[0001] The present invention relates to a method for preparing instant freeze-dried Huoshan Dendrobium by calcium salt impregnation combined with vacuum freeze-drying, belonging to the field of deep processing of agricultural and forestry products or health food processing. Background Art

[0002] Huoshan Dendrobium (scientific name: Dendrobium huoshanense), commonly known as rice Dendrobium, is mainly produced in Huoshan County, Anhui Province in the Dabie Mountain area and ranks first among the top ten famous traditional Chinese medicines in Anhui. In 2019, the local food safety standard of Anhui Province, "Huoshan Dendrobium Stem (Artificially Cultivated)", was issued, establishing the identity of Huoshan Dendrobium as a food ingredient; in April 2020, Huoshan Dendrobium was officially included in the 2020 edition of the "Chinese Pharmacopoeia" and officially obtained the national drug standard. The main active ingredients of Huoshan Dendrobium are polysaccharides, total alkaloids, etc., which have the effects of nourishing yin, anti-fatigue, anti-hypoxia, improving human immunity, delaying aging, etc.

[0003] Since ancient times, Dendrobium has emphasized "fresh products are superior". Modern pharmacological analysis has also confirmed that the contents of total alkaloids and polysaccharides in fresh Dendrobium are higher than those in dried (processed) products. Fresh Dendrobium is mainly consumed by juicing, stewing, chewing, etc., but it is also troubled by factors such as the short storage period of fresh juice and the unsatisfactory utilization rate of active ingredients. The fresh consumption of Dendrobium has not yet formed a market scale. Freeze-dried Dendrobium powder (section) is a new and healthy usage that has emerged in recent years, and it is also a processing method with good utilization effect for fresh Dendrobium. However, freeze-dried Dendrobium (section) generally needs to be rehydrated, juiced or powdered before consumption, which does not meet the demands of modern people with a fast-paced life for instant and portable food. In addition, from the appearance of the powder, it is difficult to distinguish whether it is freeze-dried powder or dried powder with a color protection (green) agent added; and it is even more impossible to distinguish the variety and grade of the freeze-dried (short) section from Dendrobium officinale, Huoshan Dendrobium, etc., which also brings safety hazards such as passing off inferior goods as superior ones, discouraging consumers. Therefore, there is an urgent need to develop a freeze-dried Dendrobium health product that is convenient for instant consumption, retains its appearance, and has a high bioavailability.

[0004] Through the retrieval on the website of the National Intellectual Property Administration, as of March 24, 2025, the invention patents directly related to the freeze-drying processing of Dendrobium mainly include:

[0005] 1. Application No.: 200810058212.X, titled "Freeze-dried Dendrobium", provides a method for freeze-drying Dendrobium, including shaping and grading → disinfection with sodium hypochlorite → cleaning → color protection with vitamin C solution → quick-freezing at (-30 to -40°C) for 20 h → vacuum drying for 20 h, and then obtaining the product.

[0006] 2. Application No.: 201110114094.1, titled "A Processing Method for Vacuum Freeze-Drying of Dendrobium officinale", including: washing the stem strips → draining → cutting into sections → pre-freezing (from room temperature to -30 to -35°C, for 2 h, maintaining at -35°C for 3 h) → sublimation drying (at 20°C, for 1 h; at 35°C, for 7 h, vacuum degree 30 Pa) → heating and evaporation (at 20 - 46°C, for 3 h; maintaining at 46°C for 7 h, vacuum degree 20 Pa) → aluminum foil bag, sealing, then it is completed.

[0007] 3. Application No.: 201110207691.9, titled "A Processing Method for Dried Products of Dendrobium huoshanense", including: harvesting → removing impurities, washing, and draining → placing in a specific mold for shaping (the whole plant with roots, stems, leaves, and flowers) → ultra-low temperature quick-freezing (-80°C, for 25 - 35 min) → vacuum dehydration drying (-45°C to 25°C, for 34 - 35 h) → opening the mold, weighing, and vacuum packaging.

[0008] 4. Application No.: 201310006916.3, titled "A New Method for Drying Fresh Dendrobium officinale", including: raw material cleaning → cutting into sections of 1 cm → blanching with (70 to 100°C hot water), cooling → draining water, loading onto trays → pre-freezing (-20 to -25°C, for 2 h) → vacuum freeze-drying (the material is frozen at -20 to -60°C, the sublimation stage is at -15 to -30°C, the desorption stage is at 30 to 60°C, pressure 100 - 150 Pa, drying for 30 h) or microwave vacuum freeze-drying (pressure 80 - 150 Pa, microwave power 450 - 800 W, for 5 - 6.5 h).

[0009] 5. Application No.: 201310424202.4, titled "A Processing Method for Freeze-Dried Strips of Dendrobium officinale", including fresh strips → selecting → soaking in (alkaline water) → peeling → washing → draining → cutting into sections (3 - 8 cm) → punching holes → freezing (-30°C, for 2 - 5 h) → vacuum freeze-drying (-40 to -75°C, for 1 - 15 h; -30°C to 30°C, for 1 - 15 h) → vacuum packaging, then it is obtained.

[0010] 6. Application No.: 201310249366.8, titled "A Quick-Freezing and Drying Processing Technology for Fresh Dendrobium officinale", including sorting fresh Dendrobium officinale → washing, draining, and cutting into sections → vacuum drying oven (+ silica gel), at the same time, adding liquid nitrogen to cool the oven to below -55°C, vacuum degree below 45 Pa, drying for more than 20 h → venting → heating to 25 - 35°C, maintaining vacuum at 35 ± 5 Pa, preserving vacuum for 3 - 5 h → venting, collecting the material, then it is obtained.

[0011] 7. Application No.: 201310218060.6, titled "Processing Method of Dendrobium huoshanense Dry Products", including fresh stem harvesting → cleaning (+ puncturing) → pre-color protection + color protection (treated with vitamin C and sodium citrate solution, 0.1 - 0.3 g / L) → ultra-low temperature quick-freezing (-60°C, 25 min) → vacuum dehydration drying (-45°C, 12.5 h; -35°C, 12.5 h; -25°C, 4.5 h; -15°C, 4.5 h; -10°C, 0.5 h; room temperature, 10 Pa, 10 h) → packaging.

[0012] 8. Application No.: 201310215670.0, titled "Processing Method of Enhanced Health Care Dendrobium huoshanense Dry Products", including harvesting → impurity removal and cleaning → plant puncturing (puncturing the stem and leaf parts, with the hole density increasing from the stem tip to the stem base) → Chinese herbal medicine infiltration (40 to 45°C, 2 - 3 min) → pre-freezing (-20°C to -25°C, 18 - 20 h) → ultra-low temperature quick-freezing (-65°C, 25 - 30 min) → vacuum drying (-35°C to 25°C, 18 - 20 h) → vacuum packaging.

[0013] 9. Application No.: 201410840969.X, titled "Vacuum Drying and Freezing Processing Method of Dendrobium officinale", including fresh stem collection → cleaning and air drying → sheath removal → uniform scoring → cutting (fixed at 10 - 11 cm) → vacuum drying (primary freeze-drying: vacuum degree 79 Pa, 55°C, 9 h; secondary freeze-drying: vacuum 79 Pa, 25°C, 2 h) → freezing treatment (-31°C to -40°C, 4 - 5 h) → packaging.

[0014] 10. Application No.: 201510566738.9, titled "Dendrobium Freeze-dried Products and Their Preparation Method", including fresh stem disinfection (sodium hypochlorite solution) → color protection (vitamin C and trehalose aqueous solution) → repeated freezing (-150°C, 60 s) - melting (blown with air at 0 to 50°C and a speed of 0.01 - 10 m / s for about 15 min) 2 - 7 times → freezing (-150°C, 60 s) → freeze-drying dehydration (-20 to -80°C for 1 - 5 h, -20 to -40°C for 1 - 5 h, 0 to 10°C for 1 - 5 h, 10 to 20°C for 1 - 5 h, 20 to 40°C for 2 - 15 h, 40 to 60°C for 4 - 20 h), thus obtained.

[0015] 11. Application No.: 201610231369.2, titled "Processing Method of Fresh Dendrobium officinale Freeze-dried Products", including fresh strips → cold water washing → placing in high-pressure resistant polyethylene bags and sealing → ultra-high pressure treatment at 300 - 500 MPa for 20 s - 1 min → pressure relief and taking out, removing surface moisture → quick freezing → vacuum freeze-drying (drying at -10 to -5°C for more than 2 h; drying at 10 to 15°C for more than 2 h, drying at 30 to 35°C for more than 2 h), sealing and storing, then obtaining.

[0016] 12. Application No.: 201710151537.1, titled "Freeze-drying Processing Method of Fresh Dendrobium officinale", including selection and treatment of raw materials → cutting into sections (2 - 3 cm) → laying on trays and loading amount → quick freezing (-40°C, 1 h) → primary freeze-drying for about 8 h (heating to 80°C within 15 min; maintaining at 80°C for 3 h, cooling to 50°C within 45 min; maintaining at 50°C for 1.5 h, cooling to 30°C within 1 h; maintaining at 30°C for 1.5 h) → adding and enriching hydrolase (2 - 3% compound enzyme (cellulase and pectinase mixed in equal amounts of 1:1)) and soaking in ice bath for 1 h → secondary freeze-drying → unloading → vacuum packaging or nitrogen filling packaging.

[0017] 13. Application No.: 201810815266.X, titled "Production Process of a Dendrobium officinale Freeze-dried Product", including washing and draining fresh Dendrobium officinale strips → selection → slicing with a slicing machine (5 - 12 mm small sections) → pulping Dendrobium officinale slices (<50°C), filtering (100-mesh sieve), homogenizing → vacuum freeze-drying Dendrobium officinale pulp (or compounding with fruit pulp);

[0018] Washing fruits → removing cores → pulping → filtering → homogenizing → pulp production → (compounding with Dendrobium officinale pulp) → vacuum freeze-drying, then obtaining.

[0019] 14. Application No.: 202210909732.7, titled "A Method for Freeze-drying Dendrobium officinale", including cleaning and preparing raw materials → cutting (2 - 4 mm thick slices) → freeze-drying.

[0020] 15. Application No.: 202310866640.X, titled "A Freeze-dried Huoshan Dendrobium and Its Preparation Method", including cutting Huoshan Dendrobium into sections → adding water to extract juice and filtering → blending with maltodextrin → filling into molds and pre-freezing → stepped multi-stage vacuum sublimation.

[0021] 16. Application No.: 202411641037.2, titled "A Freeze-dried Fresh Powder of Huoshan Dendrobium and Its Preparation Process", including Huoshan Dendrobium raw materials → cleaning → cutting → crushing and pulping → stirring and mixing → freeze-drying and pulverizing.

[0022] From the above patent analysis related to freeze-dried Dendrobium officinale, it can be seen that: currently, for the processing of freeze-dried Dendrobium products (or powders), most often the fresh stems are cut into short sections and then freeze-dried. There are few reports on freeze-drying the whole plant of Dendrobium, and most of them are freeze-dried Dendrobium officinale, while Dendrobium huoshanense is relatively less. For example: Application No. 201110114094.1 (Dendrobium officinale, cut into sections 2 - 4 cm long → freeze-dried); Application No. 201310006916.3 (Dendrobium officinale, cut into 1 cm sections → blanched and cooled → freeze-dried); Application No. 201310424202.4 (fresh Dendrobium stems, cut into sections 3 - 8 cm long → evenly punched on the surface → freeze-dried); Application No. 201310249366.8 (Dendrobium officinale, cut into sections 1 - 5 cm long → assisted by liquid nitrogen → freeze-dried); Application No. 201410840969.X (Dendrobium officinale, evenly scored → cut into sections 10 - 11 cm long → freeze-dried); Application No. 201710151537.1 (Dendrobium officinale, cut into small sections 2 - 3 cm long → quick-frozen, freeze-dried); Application No. 201810815266.X (Dendrobium officinale, cut into small sections 5 - 12 mm long → pulped → freeze-dried); Application No. 202210909732.7 (Dendrobium officinale, cut into slices 2 - 4 mm thick → freeze-dried); Application No. 202310866640.X (Dendrobium huoshanense, cut into sections 2 - 3 cm long → juiced, blended → freeze-dried), etc. In addition to the pre-treatment of cutting into sections, there are also reports on freeze-drying the fresh stems with holes pricked (Application No. 201310218060.6; Application No. 201310215670.0), freeze-drying assisted by repeated freezing-thawing (Application No. 201510566738.9), freeze-drying assisted by ultra-high pressure (Application No. 201610231369.2), enzyme-assisted freeze-drying (Application No. 201710151537.1), etc. Obviously, no matter which method of freeze-drying assisted by cutting into short sections, repeated freezing-thawing, ultra-high pressure, etc. is adopted, it is beneficial to improve the freeze-drying efficiency. However, multiple cuttings (or sectioning) will cause the loss of Dendrobium juice, and there will also be losses of nutritional components and active components; the actual implementation of other methods such as ultra-high pressure assistance or enzyme assistance is not easy. In addition, the surface of the Dendrobium (sections) obtained by the above freeze-drying methods is shrunk, resulting in damaged appearance quality, and the taste is either hard or soft, and it is not suitable as an instant food.

[0023] Regarding the freeze-drying of the whole plant of Dendrobium, Application No. 201110207691.9 discloses a method for freeze-drying the whole plant with roots, stems, leaves, and flowers intact. This method can distinguish the species of Dendrobium and its freeze-dried quality from the appearance characteristics. However, the texture properties and water content of the four parts of roots, stems, leaves, and flowers vary greatly. If the same freeze-drying conditions are adopted, it is difficult to guarantee the comprehensive quality such as appearance characteristics (such as color, plumpness), crispy and hard taste, rehydration property, and health care activity. Therefore, the present invention provides a method for preparing instant freeze-dried Dendrobium huoshanense by calcium salt impregnation in combination with vacuum freeze-drying.

[0024] The application of calcium salts (such as calcium chloride, calcium nitrate, etc.) in Dendrobium has been reported. It is often used as one of the tissue culture media or seed culture medium materials for the propagation of Dendrobium corms. For example:

[0025] Application No.: 201410850280.5, "A nutrient solution for promoting the rooting of Dendrobium officinale", each liter of rooting solution contains: 3.5 - 4.6 g of agar, 65 - 75 g of banana puree, 35 - 45 g of white sugar, 0.005 - 0.02 g of manganese sulfate, 6 - 6.5×10 -3 g of zinc sulfate, 5 - 5.5×10 -5 g of copper sulfate, 0.01 - 0.03 g of ferrous sulfate, 0.1 - 0.3 g of magnesium sulfate, 0.7 - 0.9 g of ammonium nitrate, 0.8 - 1.2 g of potassium nitrate, 0.15 - 0.25 g of calcium chloride, 6 - 7×10 -5 g of cobalt chloride, 4 - 4.5×10 -4 g of sodium molybdate, 0.08 - 0.1 g of calcium dihydrogen phosphate, 6 - 6.6×10 -4 g of potassium iodide, 7.2 - 7.6×10 -3 g of disodium ethylenediaminetetraacetate, 0.1 - 0.2 g of inositol, 1 - 1.5×10 -3 g, and also contains substances such as vitamins.

[0026] Application No.: 201510112446.8, "A nutrient solution and its application method in tissue culture seedling of Dendrobium officinale stem segments", its nutrient solution is composed of the following components: 500 mg / L of urea, 650 mg / L of potassium nitrate, 370 mg / L of calcium nitrate, 590 mg / L of potassium dihydrogen phosphate, 320 mg / L of magnesium sulfate, 85 mg / L of disodium ethylenediaminetetraacetate, 60 mg / L of ferrous sulfate, 35 mg / L of manganese sulfate, 20 mg / L of boric acid, 8 mg / L of zinc sulfate, 3.6 mg / L of copper sulfate, 1.9 mg / L of sodium molybdate, 166 mg / L of triacontanol, 26 mg / L of naphthaleneacetic acid, 42 g / L of chitosan oligosaccharide, 50 g / L of azoxystrobin, leaf ultrasonic solution and 1 L of pure water, the EC value is controlled at about 0.6, and the pH value of the acidity and alkalinity is adjusted to 6.0.

[0027] Application No.: 201610980209.8, "A tissue culture seedling medium for Dendrobium officinale with improved amino acids and its preparation method", its tissue culture seedling medium includes the following raw materials: melon juice, malic acid, aspartame, tea polyphenols, potassium salt, phosphate salt, nitrogen salt, calcium salt (calcium chloride), magnesium salt, iodine salt, boron salt, molybdenum salt, zinc salt, manganese salt, copper salt, iron salt, vitamin, amino acid, indolebutyric acid, gibberellin, 6-benzyladenine, naphthaleneacetic acid, kinetin, asparagine, conditioner, cosolvent, dispersant, compatibilizer, stabilizer, antibacterial agent, water.

[0028] Application No.: 201711112797.4, "A tissue culture method for Dendrobium officinale var. purpureum", the seed culture medium used for the germination of Dendrobium officinale var. purpureum seeds into globular bulbs contains the following components: potassium nitrate 1200 mg / L, ammonium nitrate 1050 mg / L, magnesium sulfate 370 mg / L, potassium dihydrogen phosphate 170 mg / L, calcium chloride 440 mg / L, copper sulfate 0.025 mg / L, cobalt chloride 0.025 mg / L, manganese sulfate 16.9 mg / L, zinc sulfate 8.6 mg / L, boric acid 6.2 mg / L, potassium iodide 0.83 mg / L, sodium molybdate 0.25 mg / L, Na2EDTA 37.3 mg / L, ferrous sulfate 21.8 mg / L, glycine 2.0 mg / L, thiamine hydrochloride 0.1 mg / L, pyridoxine hydrochloride 0.5 mg / L, nicotinic acid 0.5 mg / L, inositol 100 mg / L, NAA 1 - 10 mg / L, 6 - BA 5 - 10 mg / L, potato 100000 mg / L, carbon powder 250 mg / L, sucrose 30000 mg / L - hydrolyzed milk protein 700 mg / L.

[0029] Application No.: 201911406630.8, "A nutrient solution for Dendrobium officinale planting seedlings and its preparation method", the nutrient solution is prepared by mixing the macro - element mother liquor and the micro - element mother liquor with water respectively; the components of the macro - element mother liquor are: potassium nitrate, ammonium sulfate, ammonium nitrate, magnesium sulfate, potassium dihydrogen phosphate, sodium dihydrogen phosphate, calcium chloride dihydrate, iron salt, sodium salt; the components of the micro - element mother liquor are: copper sulfate, cobalt chloride, zinc sulfate, manganese sulfate, boric acid, potassium iodide.

[0030] In addition, calcium chloride combined with other substances is also applied in the Dendrobium processing process, mainly used as cleaning solution, enzyme inactivation solution, color protection solution, etc.

[0031] Application No.: 201711380066.8, Claim 3 of "A processing method for Dendrobium officinale fine tablets", "... the cleaning solution is composed of the following raw materials in parts by weight: 2 - 5 parts of table salt, 1 - 2 parts of citric acid, 1 - 2 parts of calcium chloride, 1 - 3 parts of chitosan, 100 parts of water".

[0032] Application No.: 201710558680.2, Claim 1 of "A method for making Dendrobium officinale and rosemary nutritional chewable tablets", "... immediately put it into a 15% calcium chloride solution and soak for 20 min, then take it out and immediately put it into 80°C warm water for blanching for 30 s...", the 5th line of paragraph

[0007] of the specific embodiment points out that "... through the soaking of the calcium chloride solution, the Dendrobium officinale and rosemary nutritional chewable tablets can retain the color and taste of Dendrobium officinale, and through warm water blanching, it can not only kill the bacteria on the surface of Dendrobium officinale, but also improve the taste of the finished Dendrobium officinale and rosemary nutritional chewable tablets".

[0033] Application No.: 201910739022.2, Claim 4 of "A Dendrobium officinale leaf effervescent tablet and its preparation method", "... the blanching liquid contains: 0.5 - 4.9 parts of Vc, 0.01 - 0.05 parts of calcium chloride, 0.001 - 0.008 parts of zinc gluconate, 100 parts of distilled water...".

[0034] Application No.: 201911295287.4, Claim 2 of "A fresh-keeping method for Dendrobium officinale", "... the enzyme inactivator contains 1 - 2 w% of quercetin, 4 - 5 w% of citric acid, 0.5 - 1 w% of L-cysteine, 0.01 - 0.02 w% of calcium chloride, and the rest is water".

[0035] In summary, in view of the deficiencies of the existing freeze-dried Dendrobium officinale (segments) such as surface collapse, uneven taste (soft or hard), etc., a method and process for preparing ready-to-eat freeze-dried Dendrobium officinale (strips) with relatively complete appearance by calcium salt impregnation combined with vacuum freeze-drying are urgently needed to be developed. This not only promotes the innovation of Dendrobium officinale health products and gives birth to the market competitiveness of ready-to-eat freeze-dried Dendrobium officinale products, but also provides a broader application prospect for the deep processing and industrial development of Huoshan Dendrobium officinale. Summary of the Invention

[0036] The purpose of the present invention is to provide a method for preparing ready-to-eat freeze-dried Huoshan Dendrobium officinale by calcium salt impregnation combined with vacuum freeze-drying. This method aims to react calcium salt with the abundant pectin (acidic heteropolysaccharide) in fresh Dendrobium officinale to construct a calcium pectate three-dimensional network structure, thereby reducing the mechanical damage of ice crystals to cell walls, maintaining a uniform void structure during the subsequent vacuum sublimation process, which helps the loss of water during the freeze-drying cycle; at the same time, the network structure of calcium pectate forms a rigid support framework after drying, which can effectively resist external forces and avoid uneven crispness caused by local collapse, and finally prepare ready-to-eat freeze-dried Huoshan Dendrobium officinale (strips) with relatively plump appearance and crispy taste. Of course, this kind of freeze-dried (strips) can also be further ground into freeze-dried powder or rehydrated and juiced for consumption, with high retention of active ingredients and high bioavailability.

[0037] The method for preparing ready-to-eat freeze-dried Huoshan Dendrobium officinale by calcium salt impregnation combined with vacuum freeze-drying according to the present invention comprises the following steps:

[0038] Step 1: Harvest fresh Huoshan Dendrobium officinale stems, select plump, thick and mold-free stems, remove leaves, fibrous roots, dry top joints and sheath membranes, and wash and drain the surface water.

[0039] Step 2: Pre-cut the Dendrobium officinale processed in Step 1 and immerse it in the calcium salt fixing solution for 2 h, then take it out and drain.

[0040] Step 3: Place the impregnated and drained Dendrobium stems in a vacuum freeze dryer, and successively pre-freeze at -20°C for 2 h, perform sublimation drying at a vacuum degree of 70 Pa and -40°C for 12 - 24 h, and perform desorption drying at 40 - 45°C for 1.5 - 2 h;

[0041] Step 4: Package the Dendrobium huoshanense strips freeze-dried in Step 3 to obtain the finished product.

[0042] In Step 2, the pre-cutting can be carried out by splitting (dividing into two), or by making incisions along the radial direction without cutting (generally four times on average). Try to retain the external shape characteristics of Dendrobium huoshanense and facilitate the penetration of the fixing solution. When making the incisions, only make a slit on the surface up and down to promote the penetration of the calcium salt solution and ensure that the integrity of the Dendrobium is not damaged. It can still be clearly judged from the appearance that it is spindle-shaped Dendrobium officinale

[0043] In Step 2, the fixing solution is a mixed solution composed of one or two of calcium chloride, calcium lactate, and calcium ascorbate, with a concentration of 0.8 - 2.5% (w / v), and the usage volume is 2.5 - 4 L / kg (calculated based on fresh weight) and it is appropriate to completely submerge the fresh strips.

[0044] Furthermore, the fixing solution is a mixed solution composed of calcium chloride, calcium lactate or a compound of calcium chloride - calcium ascorbate, calcium lactate - calcium ascorbate, with a concentration of 1.5 - 2.0%, a pH of 3.5 - 4.5, and a temperature of 35 - 45°C.

[0045] Furthermore, when compounding calcium chloride and calcium ascorbate, or compounding calcium lactate and calcium ascorbate, the mass ratio of the two compounds is 1:1 to 1:2.

[0046] The packaging method of the Dendrobium huoshanense freeze-dried strips is a double-layer packaging of an independent nitrogen-filled inner bag (box) and a sealed outer box. An independent desiccant is placed in the sealed box, and a transparent observation window is left on the inner and outer packaging bags (boxes), and the window size is appropriate to be able to see the complete external shape characteristics of the Dendrobium strips.

[0047] Furthermore, put the Dendrobium freeze-dried strips obtained in Step 4 into a low-temperature (≤40°C) grinding machine and process for about 100 seconds, and pass through an 80-mesh sieve to remove the Dendrobium stem bark and debris to obtain Dendrobium freeze-dried powder.

[0048] Compared with the prior art, the advantages of the present invention are as follows:

[0049] 1. Conventional freeze-dried Dendrobium sections have discomforts such as wrinkled outer skin, a taste that is either too hard or too soft, and a residue feeling. The present invention prepares instant freeze-dried Huoshan Dendrobium (sticks) through calcium salt impregnation combined with vacuum freeze-drying. The calcium salt penetrates into the Dendrobium tissue through pre-cut openings (preferably cross-cutting or scoring). Under suitable conditions, it reacts with the abundant pectic acid in the fresh sticks to form a three-dimensional network structure of calcium pectate, the "calcium bridge". This uniform void structure is conducive to the loss of moisture during the subsequent vacuum freeze-drying process. At the same time, the rigid support framework structure can also resist external forces, avoiding local shriveling and collapse, thus maintaining the crispness and hardness during the freeze-drying process of Dendrobium.

[0050] The calcium salt impregnation in this method is different from the calcium salt used as a mineral in tissue culture media or culture media that has been reported, nor is it used as an auxiliary treatment for oxidase, fungi, molds, etc. on the surface of Dendrobium stems as a blunt enzyme solution, color protection solution, cleaning solution, etc. The present invention constructs a "calcium bridge" through the solidification and cross-linking of calcium salt impregnation and pectic acid in plant cells under certain conditions (calcium salt source, concentration, temperature, pH, etc.). Only the freeze-drying assisted by the calcium bridge can achieve the improvement of the quality of Dendrobium. The freeze-dried Huoshan Dendrobium (sticks) prepared by the process of the present invention has a fresh green color, is crispy and delicious, and at the same time retains a large amount of active Dendrobium polysaccharide components, which greatly improves the instant eating experience and the value of health preservation.

[0051] 2. The use scenarios of the freeze-dried Huoshan Dendrobium (sticks) prepared by the present invention are not limited to the eating method of opening the bag and eating immediately. It can also be further ground into freeze-dried powder for brewing and eating, or rehydrated for juicing or chewing. When the freeze-dried Dendrobium sticks are ground into powder, the powder yield is high. When brewed with warm water, there is no caking, the taste is smooth and rich in gum, and the utilization rate of effective components for digestion and absorption is high; when rehydrated and juiced, it immediately restores the taste and flavor of fresh juice, and the dissolution rate of effective components is still greatly improved compared with directly adding water to juice the fresh sticks after harvesting.

[0052] 3. The present invention adopts a double packaging design of an independent nitrogen-filled inner bag, a desiccant, and an outer packaging of a sealed box. It can not only allow consumers to directly see the external quality of Dendrobium through the transparent window on the packaging, but also prevent factors such as oxidation and moisture absorption from causing a decrease in the crispy taste, effectively extending the shelf life and facilitating consumers to carry, and can be enjoyed at any time and anywhere. Description of the Drawings

[0053] Figure 1 Product pictures of freeze-dried Dendrobium sticks, where (a), (b), (c), and (d) are the freeze-dried products of Example 2, the conventional freeze-dried control 1, the freeze-dried products of Example 4, and the conventional freeze-dried control 2 in sequence.

[0054] Figure 2 Internal microstructures of pectin extracted from freeze-dried Dendrobium products, where (1) and (2) are scanning electron micrographs of the control 1 and the freeze-dried sample of Example 2 at about 60 times magnification; (3) and (4) are scanning electron micrographs of the control 1 and the freeze-dried sample of Example 2 at 500 times magnification.

[0055] Figure 3 It is the infrared spectrogram of extracting pectin from freeze-dried Dendrobium officinale products, where (a), (b), (c), and (d) are Reference 1, Control 1, Reference 2, and Example 2 respectively.

[0056] Figure 4 It is the HPLC chromatogram of the sample prepared by brewing the freeze-dried powder of Example 4 and 4 kinds of monosaccharide reference substances during gastrointestinal digestion, where 1 is mannose, 2 is 1-phenyl-3-methyl-5-pyrazolone (PMP), 3 is glucose, 4 is galactose, and 5 is arabinose. Detailed implementation manners

[0057] The following examples further illustrate the technical content of the present invention, aiming to elaborate the specific implementation manners of the present invention. However, these examples are only exemplary descriptions and do not constitute a limitation to the protection scope of the present invention.

[0058] Example 1: Freeze-dried strips of cut Huoshan Dendrobium officinale 1

[0059] 1. Select fresh Huoshan Dendrobium officinale stems with intact epidermis, plump shape, no mildew spots, and uniform size. Rinse the soil on the surface of the stems, and remove the leaves, fibrous roots, slightly dried finger joints at the top, and sheath membranes. After washing, air-dry naturally to ensure the effects of subsequent pre-freezing and vacuum freeze-drying.

[0060] 2. Take 300 g of fresh Huoshan Dendrobium officinale stems with surface moisture drained, cut them in half longitudinally from the root with scissors or a blade to form two pieces of similar size. Put the cut fresh stems into a 1.0% CaCl2 and 1.0% calcium lactate solution (pH adjusted to about 4.0) with a volume of about 1.1 L, so that all the fresh Dendrobium officinale stems (pieces) are completely submerged in the fixing solution. After soaking at 40 °C for 2 hours, take them out, and blot or air-dry the small amount of impregnating solution remaining on the surface with absorbent paper.

[0061] 3. Lay the impregnated Huoshan Dendrobium officinale flat on the material tray, ensuring there is a gap between the fresh stems (pieces) and no overlapping or stacking phenomenon. Set the pre-freezing temperature to -20 °C and the pre-freezing time to 2 hours; set the sublimation drying temperature to -40 °C, the sublimation drying time to 18 hours, and the vacuum degree to 70 Pa; set the desorption drying temperature to 45 °C and the desorption drying time to 2 hours.

[0062] 4. Place the freeze-dried Huoshan Dendrobium officinale into the inner PA / PE packaging bag, with about 6 - 8 strips (pieces) in each inner bag. After vacuumizing and filling with nitrogen for independent packaging, then put it into a sealed outer box with a desiccant for packaging. Among them, both the inner bag and the outer box are provided with transparent observation windows, which are convenient for consumers to directly observe the Dendrobium officinale variety and the quality of its freeze-dried strips.

[0063] Similarly, in step 2, except that water is used instead of the impregnating solution for treatment, the remaining treatment methods are the same as those in the steps. The conventional freeze-dried Dendrobium officinale strips (pieces) obtained by this method are used as Control 1.

[0064] Similarly, the fresh Dendrobium officinale stems are cut in half through the process of Step 2, then treated with water instead of the impregnating solution, and the freeze-drying process of Step 3 is cancelled. The fresh Dendrobium officinale stems (slices) obtained by this method are used as Reference Sample 1.

[0065] Example 2: Freeze-dried Dendrobium huoshanense (cut in half) Strip 2

[0066] 1. Select fresh Dendrobium huoshanense stems with intact epidermis, plump shape and uniform size, rinse the soil on the surface of the stems, and remove the leaves, fibrous roots, slightly withered finger joints at the top and the sheath membrane. After washing, air-dry naturally to ensure the effects of subsequent freezing and vacuum drying.

[0067] 2. Take 500 g of fresh Dendrobium huoshanense stems with surface moisture drained, cut them in half longitudinally from the root of the whole plant of Dendrobium using scissors or a blade to form two pieces, and put the cut fresh stems into 2.0% CaCl2 (pH adjusted to 4.0 - 4.5) with a volume of about 1.5 L, ensuring that all the fresh Dendrobium huoshanense stems (slices) are completely submerged in the impregnating solution. After impregnating at 35˚C for 2 hours, take them out and blot the small amount of remaining impregnating solution on the surface with absorbent paper or air-dry naturally.

[0068] 3. Lay the impregnated Dendrobium huoshanense flat on the material tray, ensuring there is a gap between the fresh stems (slices) and no overlapping or stacking. Set the pre-freezing temperature at -20˚C and the pre-freezing time at 2 hours; set the sublimation drying temperature at -40˚C, the sublimation drying time at 16 hours, and the vacuum degree at 70 Pa; set the desorption drying temperature at 45˚C and the desorption drying time at 1.5 hours.

[0069] 4. Place the freeze-dried Dendrobium huoshanense into an inner bag with independent air inflation packaging, and then put it into a sealed outer box with a desiccant for packaging. Among them, both the inner bag and the outer box are provided with transparent observation windows to facilitate consumers to directly observe the Dendrobium variety and the quality of its freeze-dried strips.

[0070] Similarly, the fresh Dendrobium officinale stems are processed through Step 1 and Step 2, and the freeze-drying process of Step 3 is cancelled. The Dendrobium officinale stems (slices) impregnated with calcium solution obtained by this method are used as Reference Sample 2.

[0071] Example 3: Freeze-dried Dendrobium huoshanense (whole plant) Strip 1

[0072] 1. Select fresh Dendrobium huoshanense stems with intact epidermis, plump shape and uniform size, rinse the soil on the surface of the stems, and remove the leaves, fibrous roots, and slightly withered finger joints at the top. After washing, air-dry naturally to ensure the effects of subsequent freezing and vacuum drying.

[0073] 2. Take 400 g of fresh Dendrobium huoshanense strips with surface moisture drained, remove the sheath membrane, and use a sharp tool such as a small knife to cut 3 - 4 times along the surface texture of the Dendrobium, without cutting through, and try to preserve the complete appearance of the Dendrobium. Put the cut fresh Dendrobium huoshanense strips into a mixed solution of 0.8% calcium lactate and 1.5% calcium ascorbate (pH about 4.0), with a volume of about 1.5 L, ensure that all the fresh Dendrobium strips are completely submerged in the impregnating solution, soak at 45°C for 2 hours and then take out, and dry the small amount of remaining impregnating solution on the surface with absorbent paper or air-dry naturally.

[0074] 3. Lay the impregnated fresh Dendrobium huoshanense strips flat on the material tray, ensure there is a certain interval between the Dendrobium strips without overlapping and piling up, set the pre-freezing temperature at -20°C and the pre-freezing time at 2 hours; set the sublimation drying temperature at -35°C, the sublimation drying time at 16 hours, and the vacuum degree at 70 Pa; set the desorption drying temperature at 45°C and the desorption drying time at 2 hours.

[0075] 4. Place the freeze-dried Dendrobium huoshanense strips in an inner box with independent inflatable packaging, and then put it into a sealed outer box with a desiccant for packaging. Among them, both the inner bag and the outer box have transparent observation windows, which are convenient for consumers to directly observe the type of Dendrobium and the quality of the freeze-dried strips.

[0076] Similarly, in step 2, except for treating with water instead of the impregnating solution, the remaining treatment methods are the same as the steps, and the conventionally freeze-dried Dendrobium strips obtained by this method are used as control 2.

[0077] Example 4: Freeze-dried Dendrobium huoshanense (whole plant) strip 2

[0078] 1. Select fresh Dendrobium huoshanense strips with intact epidermis, plump shape, and uniform size, rinse the soil on the surface of the stem strips, and remove the leaves, fibrous roots, slightly dry finger joints at the top, and sheath membrane. After washing, air-dry naturally to ensure the subsequent freezing and vacuum drying effects.

[0079] 2. Take 500 g of fresh Dendrobium huoshanense strips with surface moisture drained, use a sharp tool such as a small knife to cut 3 - 4 times along the surface texture of the Dendrobium, without cutting through, and try to preserve the complete appearance of the Dendrobium. Put the cut fresh Dendrobium huoshanense strips into a solution of 1.0% calcium chloride and 1.0% calcium ascorbate (pH about 4.0), with a volume of about 2.0 L, ensure that all the fresh Dendrobium strips are completely submerged in the impregnating solution, soak at 45°C for 2 hours and then take out, and dry the small amount of remaining impregnating solution on the surface with absorbent paper or air-dry naturally.

[0080] 3. Lay the impregnated fresh Dendrobium huoshanense strips flat on the material tray, ensure there is an interval between the Dendrobium strips without overlapping and piling up, set the pre-freezing temperature at -20°C and the pre-freezing time at 2 hours; set the sublimation drying temperature at -35°C, the sublimation drying time at 18 hours, and the vacuum degree at 70 Pa; set the desorption drying temperature at 45°C and the desorption drying time at 2 hours.

[0081] 4. Place the freeze-dried Dendrobium huoshanense strips into an inner box with independent inflatable packaging, and then put it into a sealed outer box with desiccant for packaging. Among them, there is a transparent observation window on both the inner bag and the outer box, which is convenient for consumers to directly observe the variety of Dendrobium and the quality of its freeze-dried strips.

[0082] Example 5: Sensory evaluation of freeze-dried Dendrobium huoshanense strips

[0083] Select 10 sensory evaluation personnel to evaluate the color, shape, flavor and taste of four groups of Dendrobium strips. The evaluation criteria are shown in Table 1.

[0084]

[0085] Combined with the evaluation criteria in Table 1, conduct sensory evaluations on the four groups of freeze-dried Dendrobium products obtained in Example 1 (cut in half, calcium chloride and calcium lactate solution), Example 2 (cut in half, calcium chloride), Example 3 (scored, calcium lactate + calcium ascorbate), Example 4 (scored, calcium chloride + calcium ascorbate solution) and their control products 1 and 2. The results are listed in Table 2.

[0086]

[0087] Judging from the scoring results in Table 2, after the fresh strips are cut in half or scored as a whole plant and then impregnated with the fixing solution, the shape, taste and texture of the freeze-dried Dendrobium strips are significantly improved. The more prominent feature in terms of sensory evaluation is that the shape is more plump, there is no obvious collapse, and the crispness is greatly improved. Finally, the comprehensive score value is generally about 60% higher than that of the non-impregnated treatment.

[0088] Figure 1 Pictures of the samples of Example 2, Conventional freeze-drying control 1, Example 4 and Conventional freeze-drying control 2 are listed. It can also be directly seen from the pictures that the appearance of the Dendrobium strips treated by calcium impregnation combined with freeze-drying is more plump and the collapse phenomenon is improved.

[0089] In addition, powder the freeze-dried products of Control 1 and Example 2, and homogenize the reference products 1 and 2. The solids obtained after treatment with 80% ethanol, dimethyl sulfoxide-water (9:1, V / V), chloroform-ethanol (2:1, V / V) are the cell walls of Dendrobium; these cell wall materials are extracted with water, and the precipitate obtained after extraction is extracted with 1,2-cyclohexanediaminetetraacetic acid (CDTA) at room temperature for 4 h, and the precipitation is extracted twice again. The supernatant liquids obtained three times are combined, concentrated and freeze-dried to obtain the corresponding chelated pectin, and scanning electron microscopy and infrared spectroscopy are respectively performed for detection.

[0090] Electron microscopy analysis: The chelated pectin extracted from Control 1 and Example 2 above is treated by sputtering with gold for 2 minutes, then placed under a scanning electron microscope for magnified observation and photography. The microscopic morphology is as shown in the appendix Figure 2As shown in the figure. The cross-section of the conventional freeze-dried product without impregnation treatment is uneven, the void distribution is extremely uneven, and there are many fractures; the cross-section of the freeze-dried Dendrobium officinale product with impregnation treatment in Example 2 is arranged loosely and in a network shape, and the pore distribution is obvious and relatively uniform.

[0091] Infrared spectroscopy analysis: The ATR infrared spectra superposition diagram of the chelated pectin extracted from the above-mentioned reference 1, control 1, Example 2 and reference 2 is as attached Figure 3 As shown. Among them, the absorption peak near 1408 cm -1 is the symmetric stretching vibration of the carboxylate ion (COO - ); the absorption peak near 1592 cm -1 is the asymmetric stretching vibration of the carboxylate ion (COO - ); the absorption peak near 1727 cm -1 is the stretching vibration of the carbonyl group (C=O) in the carboxylic acid methyl ester group; the absorption peak near 2930 cm -1 is the stretching vibration of the methyl group (CH3) in the carboxylic acid methyl ester group. Compared with the conventional freeze-dried product without impregnation treatment of control 1, the symmetric stretching vibration of the carboxylate ion (COO - ) and the asymmetric stretching vibration of the carboxylate ion (COO - ) of the freeze-dried Dendrobium officinale product with impregnation treatment in Example 2 have relatively significant changes in wave numbers. This is because there is an electrostatic interaction between Ca 2+ and COO - . As an electron-withdrawing ion, calcium causes a charge deviation, thus realizing the combination of calcium and pectin to form a "calcium bridge" structure, thereby constructing a stable three-dimensional network, so that it is easy for water to escape during the subsequent freeze-drying sublimation cycle and can resist external force impact, ultimately improving the uneven problems such as surface collapse, hard or soft taste of the freeze-dried Dendrobium officinale product. The wave numbers of the carboxylate ion (COO - ) of the conventional Dendrobium officinale without impregnation treatment of reference 1 and the conventional freeze-dried product without impregnation treatment of control 1 did not change significantly and the overall spectrogram was relatively consistent, while there were significant changes in the wave numbers of the calcium pectate of the Dendrobium officinale with impregnation treatment of reference 2. In addition, the ester group usually does not allow ion binding, and the addition of calcium causes a slight wave number shift in the wave numbers of the carbonyl group (C=O) and the methyl group (CH3) in the carboxylic acid methyl ester group, which is caused by the interaction between calcium ions and the hydrogen bonds or van der Waals forces around the ester group, resulting in changes in the local microenvironment.

[0092] Example 6: Determination of water loss rate, moisture content and rehydration ratio of freeze-dried Dendrobium huoshanense

[0093] The water loss rate (%) can evaluate the water loss or removal situation of fresh Dendrobium officinale during the drying process. The fresh Dendrobium officinale is weighed (g) before and after freeze-drying respectively, and the water loss rate (%) can be calculated through the weight loss (g):

[0094]

[0095] The moisture content has an important impact on the quality difference of freeze-dried products. If the moisture content is too high, the product is not crispy enough; if the moisture content is too low, the product tastes too hard. Refer to the national standard GB 5009.3-2016 to determine the moisture content of freeze-dried Dendrobium officinale strips.

[0096] The rehydration ratio can evaluate the ability of freeze-dried Dendrobium officinale to return to its original state after absorbing water, and it is an important indicator to measure the impact of the drying process on its quality. Immerse a certain amount of freeze-dried Dendrobium officinale in water at 30 °C for 40 minutes. After draining and removing the surface moisture, calculate the rehydration ratio according to the initial and rehydrated masses through the following formula:

[0097]

[0098] Measure the moisture content, rehydration ratio, etc. of the freeze-dried Dendrobium officinale products obtained in Examples 1, 2, 3, 4 and their control products 1 and 2, and the results are listed in Table 3.

[0099]

[0100] As can be seen from Table 3, the moisture content of freeze-dried Huoshan Dendrobium officinale strips reaches about 7.0 - 7.5%, meeting the requirement of the Chinese Pharmacopoeia that the moisture content of Huoshan Dendrobium officinale is less than 10%; compared with conventional freeze-dried products, the rehydration ratio of freeze-dried products treated by impregnation increases by 14 - 27%, generally reaching more than 2.5.

[0101] Table 3 shows that the rehydration ratio of freeze-dried products treated by calcium impregnation increases. Combining with the Figure 1 attached appearance pictures, the Figure 2 , 3 morphology and structure analysis of Dendrobium officinale pectin shows that: (1) Calcium salt impregnation and its conditions are the key factors for forming the "calcium bridge" structure; (2) Subsequent freeze-drying treatment has no significant impact on the calcium-impregnated calcium pectate structure of Dendrobium officinale or the structure of non-impregnated Dendrobium officinale pectin. However, without the "calcium bridge" formed by calcium impregnation as a prerequisite, it is not easy to achieve effective freeze-drying of the whole plant (or cut in half) of Dendrobium officinale, and the quality problems such as appearance collapse and uneven crispness of the freeze-dried products cannot be significantly improved. Therefore, "calcium salt impregnation-assisted vacuum freeze-drying" in the present invention is not a simple addition of two treatment methods of calcium impregnation and freeze-drying, but the beneficial results can be achieved only when the calcium salt impregnation forms a calcium bridge and then acts synergistically on the freeze-drying process.

[0102] Example 7: Texture and color measurement of freeze-dried Huoshan Dendrobium officinale strips

[0103] The brittleness and hardness tests can evaluate the physical properties of freeze-dried Dendrobium products, and these indicators are related to the taste of the products. Use a texture analyzer to test the brittleness and hardness of Dendrobium. During the test, use a MORS probe with a diameter of 20 mm, select the Compression program, and set the parameters as follows: the pre-test rate is 1 mm / s, the in-test rate is 0.5 mm / s, the post-test rate is 10 mm / s, the compression ratio is 95%, and the initial force is 10 g. Each sample is tested 3 times, and the average value is taken to obtain the brittleness and hardness results. A smaller brittleness value indicates that it is more crispy, and the hardness value should be moderate.

[0104] The chromaticity value test can indicate the influence on the color of fresh Dendrobium stems after freeze-drying through impregnation pretreatment, and it is tested with a color difference meter. Take a certain amount of the powder of the freeze-dried product. After calibrating with a white board, place the powder under a unified background, align the lens opening with the surface of the sample, and press the test button to conduct the test. Each powder of the freeze-dried Dendrobium product is tested three times at different positions, and the average value is taken to obtain its chromaticity value. Among them, the chromaticity value includes the following three parameters:

[0105] L value (Lightness): Represents brightness, and the value range is from 0 to 100, where 0 represents pure black and 100 represents pure white.

[0106] a value (Green-Red Axis): Represents red-green chromaticity, and the value range is from -128 to +127, where -128 represents green and +127 represents red.

[0107] b value (Blue-Yellow Axis): Represents blue-yellow chromaticity, and the value range is from -128 to +127, where -128 represents blue and +127 represents yellow.

[0108] The brittleness, hardness, and chromaticity of the freeze-dried samples of Example 1 (cut in half, calcium chloride solution), Example 2 (cut in half, calcium chloride + calcium ascorbate solution), Example 3 (scored, calcium lactate + calcium ascorbate), and Example 4 (scored, calcium citrate + calcium ascorbate) were tested respectively, and the results are shown in Table 4.

[0109]

[0110] As can be seen from Table 4, compared with the conventional freeze-drying of Control 1 and 2, the calcium salt impregnation treatment has a better promoting effect on the brittleness and hardness of the freeze-dried Dendrobium strips, manifested as a decrease in hardness and an increase in crispness, while there is no significant difference in the brittleness and hardness test results of the freeze-dried products treated with the four solutions. Similarly, the chromaticity values of the freeze-dried products obtained with the four impregnating solutions are not very different.

[0111] Example 8: Determination of the contents and dissolution rates of active polysaccharides and total alkaloids in freeze-dried Dendrobium strips and freeze-dried powders

[0112] The contents of active polysaccharides and total alkaloids in freeze-dried Dendrobium strips are used to evaluate the retention of active ingredients when fresh Dendrobium stems (strips) are transformed into freeze-dried Dendrobium strips. In addition, to evaluate the effective release of active polysaccharides and alkaloids in freeze-dried Dendrobium powder during actual use, taking the scenario of adding water to brew the powder of freeze-dried Dendrobium strips as an example, the contents of polysaccharides and alkaloids in the brewing solution are measured and compared with the contents in the freeze-dried powder, and the dissolution rate (%) of the active ingredients is calculated accordingly. This provides a reference for measuring the quality and efficacy of freeze-dried Dendrobium.

[0113] Put the freeze-dried Dendrobium product of Example 4 into a low-temperature (≤40°C) grinder and process for about 100 seconds, then pass through an 80-mesh sieve to remove the Dendrobium stem bark and debris, and the freeze-dried Dendrobium powder is obtained. The powder yield is generally over 60%.

[0114] Brewing of Dendrobium powder: 1.0 g of fine Dendrobium powder after sieving is slowly added to 50 mL of pure water at 75 - 80°C, and stirred with an electric stirrer at 50 rpm. The Dendrobium powder can be completely dispersed within basically 5 s, kept warm for 20 min, and centrifuged at 3000 rpm. Measure the contents of polysaccharides and alkaloids in the clear Dendrobium solution, and then calculate the dissolution rate (%).

[0115] The phenol-sulfuric acid method is used to determine the polysaccharide content in the freeze-dried Dendrobium powder and the brewing solution, and then calculate the polysaccharide dissolution rate (%); similarly, the bromocresol green acid staining method is used to determine the total alkaloid content, and calculate the alkaloid dissolution rate (%) accordingly.

[0116]

[0117] As can be seen from Table 5, the polysaccharide content of the freeze-dried Dendrobium strips assisted by calcium salt impregnation is about 25%, which is almost equivalent to the polysaccharide content of fresh Dendrobium (estimated by losing 75% of the water in the fresh strips, that is, 6.51×4 = 26.04 of the fresh strip weight, which is the polysaccharide content of the dried Dendrobium); the polysaccharide dissolution rate of the calcium salt impregnation treatment is generally 30 - 40% higher than that of the conventional freeze-drying of Control 1 and 2, while the change in the total alkaloids is relatively small, basically around 10%. As attached Figure 2 shown, the pore distribution of the three-dimensional network structure of calcium pectate is obvious and uniform. When adding water to brew, it is more likely to promote the dissolution of water-soluble active ingredients such as polysaccharides, while the change in components mainly composed of fat-soluble substances such as total alkaloids is relatively small.

[0118] Example 9: Determination of the digestion and absorption of polysaccharides in the brewing solution of freeze-dried Dendrobium powder

[0119] Taking the brewing solution of the freeze-dried powder obtained in Example 4 above as an example. Regarding the gastrointestinal digestion, the stomach and small intestine are regarded as a whole digestive system. During the reaction process, it first reacts in gastric juice for 6 h, and then undergoes simulated intestinal juice digestion.

[0120] Artificial gastric juice digestion: Prepare a 2.0 mg / mL infusion of freeze-dried Dendrobium officinale powder with pure water at 75 - 85 °C, filter it, take 100.0 mL of the above solution and mix it with an equal volume of artificial gastric juice. Place the mixture in a shaker and oscillate it for 2 h, 4 h, and 6 h under the conditions of a constant temperature of 37 °C, 100 r / min, and a swing amplitude of 5 mm. After each time point is reached, remove 10.0 mL of the reaction solution from the solution and quickly place it in a boiling water bath to terminate the reaction.

[0121] Artificial intestinal juice digestion: Take out the sample digested by simulated gastric juice from the shaker, mix 50.0 mL of the above sample with 50.0 mL of artificial intestinal juice, and finally adjust the pH value to 7.0 with 1.0 mol / L NaOH solution. Put it into the shaker and continue to oscillate it for 2 h, 4 h, and 6 h under the conditions of 37 °C, 100 r / min, and a swing amplitude of 5 mm. After each set time point ends, remove 10.0 mL of the reaction solution respectively and place it in a boiling water bath to terminate the reaction.

[0122] After the above steps, centrifuge the digestive fluid mixture (5000 r / min) for 5 min and take the supernatant. Precisely measure 1.0 mL from each group and make it up to 10.0 mL to obtain the test solution.

[0123] Detection of reducing sugar: Precisely measure 2.0 mL of each test solution and place it in a 10 mL weighing bottle. Add 5.0 mL of 3,5-dinitrosalicylic acid test solution (DNS), shake well, heat it in a boiling water bath for 5 min, quickly cool it with cold water, add water to the scale, shake well, and measure the absorbance at a wavelength of 540 nm. Prepare a blank solution with 2.0 mL of water in the same way and perform the same operation according to the above steps. Substitute it into the standard curve to calculate the concentration.

[0124] After filling all the remaining supernatant into a 500 - 1000 Da dialysis bag, place the dialysis bag in a beaker containing 50.0 mL of normal saline so that the dialysis time is the same as the simulated digestion time. Due to the selective permeability of the dialysis bag, monosaccharides can pass through the membrane of the dialysis bag, while other components are retained inside the bag. Take the liquid outside the dialysis bag, filter it through a 0.22 μm aqueous membrane, and detect the monosaccharide composition. Use normal saline as a blank control. Perform chromatographic analysis to obtain its peak area and elution time, etc., and calculate the monosaccharide content by the external standard method.

[0125]

[0126] Dendrobium officinale polysaccharide undergoes hydrolysis in gastric and intestinal juices to produce reducing sugars. As can be seen from Table 6, in simulated gastric juice, the content of reducing sugar gradually increases, indicating that the digestion reaction is continuously proceeding. As a continuous digestion process, at 4 h and 6 h in intestinal juice, its content no longer changes, indicating that the digestion reaction has reached the end point.

[0127] After the freeze-dried powder infusion of Dendrobium huoshanense is subjected to simulated gastrointestinal digestion, monosaccharides are produced. By comparing the standard product spectrum, it can be determined that the monosaccharide composition is mannose, glucose, galactose, and arabinose, as shown in Figure 3 . Table 7 lists the contents of different monosaccharides. Among them, the glucose content is the highest, accounting for most of the reducing sugars, reaching 0.1369 mg / mL at 6 h in intestinal fluid. The contents of the other three monosaccharides are relatively low. After the reaction with the digestive fluid, as the reaction time continues, the contents of each monosaccharide increase. After 4 h of digestion in intestinal fluid, the increase amplitude of the content is significantly reduced, indicating that the reaction basically terminates.

[0128]

[0129] Example 10: Determination of the viscosity and polysaccharide dissolution rate of the rehydrated juice of freeze-dried Dendrobium

[0130] Taking the rehydrated juice of the freeze-dried strips obtained in Examples 2 and 4 as an example, the fresh strip weights are calculated according to the water loss rates (76.03%, 73.89%) of the freeze-dried strips in Examples 2 and 4, that is, 1 g of freeze-dried strip can be obtained from 4.2 g and 3.8 g of fresh strips. When juicing the fresh Dendrobium huoshanense and water in the same batch, the ratio is 1 g: 25 mL of pure water. The freeze-dried strips and water are soaked and rehydrated according to the ratio of 1 g: 105 mL (Example 2) or 95 mL (Example 4) of water, and then directly juiced after rehydration. The viscosity and polysaccharide dissolution rate (%) of the rehydrated juice of the freeze-dried strips and the fresh strip juice are compared.

[0131]

[0132] It can be seen from the data in Table 8 that the viscosity of the rehydrated juice of the freeze-dried strips is slightly lower than that of the fresh strip juice, while the polysaccharide dissolution rate is increased by about 1 time. This also shows that the pore distribution of calcium pectate in the Dendrobium treated by calcium impregnation freeze-drying helps the dissolution of active polysaccharides, indirectly enhancing the health care activity.

Claims

1. A method for preparing instant freeze-dried Huoshan Dendrobium by calcium salt impregnation and vacuum freeze drying, characterized in that The steps include: Step 1: Harvest fresh stems of Huoshan Dendrobium, select plump, thick and mold-free stems, remove leaves, fibrous roots, dry knuckles at the top and sheath, wash and drain the surface moisture; Step 2: pre-cut the dendrobium treated in step 1 and immerse it in calcium salt fixative for 2 h, then take it out and drain it; Step 3: Place the soaked and drained Dendrobium stems in a vacuum freeze dryer, pre-freeze at -20°C for 2 h, vacuum 70Pa, sublimation drying at -40°C for 12-24 h, and desorption drying at 40-45°C for 1.5-2 h; Step 4: After freeze-dried in step 3, the freeze-dried strips of Dendrobium huoshanense are packaged to obtain the finished product.

2. The method according to claim 1, characterized in that: In step 2, the pre-cutting is performed by cutting in half, or by making radial cuts but not cutting.

3. The method according to claim 1, characterized in that: In step 2, the fixing liquid is a mixed solution consisting of one or two of calcium chloride, calcium lactate and calcium ascorbate.

4. The method according to claim 3, characterized in that: The concentration of the fixing solution is 0.8-2.5%.

5. The method according to claim 4, characterized in that: The volume of the fixing solution used is 2.5-4 L / kg, based on the fresh weight of Dendrobium huoshanense.

6. The method according to claim 3, characterized in that: The fixing liquid is calcium chloride or calcium lactate, or a mixed solution of calcium chloride and calcium ascorbate or calcium lactate and calcium ascorbate.

7. The method according to claim 6, characterized in that: The concentration of the fixing solution is 1.5-2.0%, the pH is 3.5-4.5, and the temperature is 35-45°C.

8. The method according to claim 1, characterized in that: The freeze-dried dendrobium strips obtained in step 4 are placed in a low-temperature grinder for 80-100 seconds, passed through an 80-mesh sieve, and the dendrobium stem bark and debris are removed to obtain the dendrobium freeze-dried powder.

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