Nitrogen positive pressure fresh-keeping plant beverage concentrate and preparation method thereof

Abstract

The application discloses a nitrogen positive pressure fresh-keeping plant beverage concentrate and a preparation method thereof, and belongs to the technical field of food processing and packaging. The plant raw materials are extracted three times under closed conditions through a charcoal fire and a direct fire, the extract is sequentially filtered through a nanofiltration membrane and concentrated at a low temperature through a reverse osmosis membrane, the obtained concentrate is filled into a metal can, sealed after being filled with nitrogen, sterilized at a high temperature and a high pressure, and finally assembled with a nozzle, and a continuous liquid stream is sprayed out of the can for use by utilizing the positive pressure in the can. The nanofiltration-reverse osmosis combination is used for preventing membrane blockage, the nitrogen positive pressure and the high-temperature sterilization are cooperated to realize a continuous sterile positive pressure environment after the can is opened, volatile oils and heat-sensitive components are significantly retained, the shelf life at room temperature is more than one year without preservatives, and the aroma loss rate is low.

Description

Technical Field

[0001] This invention belongs to the field of food processing and packaging technology, specifically relating to a nitrogen positive pressure preservation concentrate for plant-based beverages and its preparation method. Background Technology

[0002] Plant-based beverages, especially concentrated beverages made from medicinal and edible plants, have gained widespread acceptance in the consumer market in recent years due to their natural and healthy properties. To facilitate transportation, storage, and consumer dosage, the industry typically further processes plant extracts into concentrated products. However, from raw plant materials to a finished concentrated product that meets modern consumers' expectations of "convenience, safety, and high-quality flavor," several long-standing and unresolved technical obstacles remain in the entire production chain.

[0003] In the concentration process, traditional plant extract concentration relies heavily on high-temperature evaporation or vacuum thermal concentration. While these methods are technically mature, their long-standing drawbacks are significant: the high-temperature environment (usually above 80°C) leads to a substantial loss of the abundant volatile oils, aromatic substances, and heat-sensitive active ingredients in the plant raw materials, resulting in a bland flavor and diminished efficacy in the final product. To address this issue of high-temperature damage, membrane separation technology has been gradually introduced into the plant-based beverage industry. Using reverse osmosis membranes for dehydration and concentration can indeed retain heat-sensitive components to some extent. However, plant extracts are complex, containing large amounts of pectin, plant colloids, large molecular proteins, and polysaccharides. These impurities easily accumulate on the surface of the reverse osmosis membrane, clogging the pores and causing a sharp decline in membrane flux, requiring frequent cleaning and severely restricting the efficiency of continuous industrial production. In existing technologies, although there have been attempts to use pre-filtration methods such as ultrafiltration to reduce reverse osmosis membrane fouling, these conventional pretreatments have limited ability to retain fine colloids and medium molecular weight impurities. They cannot fundamentally solve the contradiction between membrane fouling and concentration efficiency, resulting in the concentration process being unable to achieve both "retaining components" and "maintaining production capacity" in the long term.

[0004] The challenges of packaging and preservation for concentrated liquid products are equally daunting. Because concentrated liquids are rich in nutrients, they are highly susceptible to oxidation and spoilage, as well as microbial growth, once exposed to air after opening. To extend shelf life, the industry currently relies on two main approaches: one is adding chemical preservatives, but this contradicts consumers' health-conscious pursuit; the other is relying on a complete cold chain for storage and transportation, but cold chain costs are high and coverage is limited, making it difficult to meet the widespread needs of the mass market. Even if the product undergoes high-temperature sterilization at the factory to achieve commercial sterility, once the consumer opens the container, bacteria-laden air immediately enters, and the contents lose their sterile barrier, making it impossible to maintain a long-term freshness even with repeated use.

[0005] Furthermore, existing concentrated beverage products generally lack sophisticated design in terms of dispensing methods. Traditional bottled pouring methods make it difficult to precisely control the dosage, and each pour means a larger area of ​​the liquid comes into contact with the air. While some products using spray pumps improve the dosing issue, the atomization process accelerates the loss of aroma components, which is undoubtedly a loss for plant-based beverages where aromatic flavor is an important quality characteristic. These inconveniences are essentially due to the long-standing disconnect between upstream concentration processes and downstream packaging technologies—that is, a lack of systematic and coordinated design between the quality characteristics of the concentrated beverage, the gaseous environment inside the packaging, and the actual way consumers dispense it.

[0006] The patent CN1234365A, entitled "A Filling Process for Optimizing the Preservation and Consumption of Instant Beverages," specifically discloses a method of pre-purifying and sterilizing a pressure-resistant container, evacuating it to a negative pressure of 600-740 mmHg, filling it with concentrated liquid instant beverage, then filling the container with low-pressure nitrogen gas at 0.02-0.08 MPa and sealing it. The container is equipped with a nozzle with a conduit; when in use, pressing the nozzle uses the air pressure inside the container to spray out the liquid. However, in this method, due to the low nitrogen pressure, the positive pressure inside the container is difficult to maintain after multiple uses, resulting in a limited shelf life after opening. Furthermore, sterilizing only the empty container before filling makes it difficult to inhibit microbial growth in the low-pressure environment. Additionally, the nozzle with the conduit does not easily form a stable and continuous liquid flow under low-pressure conditions, and aromatic substances are easily lost during use. Summary of the Invention

[0007] To address the technical problems existing in the preparation and preservation of plant beverage concentrates in the prior art, this invention provides a method for preparing plant beverage concentrates using nitrogen positive pressure preservation that can simultaneously achieve flavor preservation, high-efficiency concentration, long shelf life at room temperature, and freshness preservation after opening.

[0008] To achieve this objective, the following solution is provided: This invention provides a method for preparing a concentrated plant-based beverage using nitrogen positive pressure preservation, comprising the following steps: S1. Mix the plant material with water, perform a circulating extraction under closed conditions, combine the extracts and cool them; S2. Filter the cooled extract through a charged nanofiltration membrane to remove colloidal and macromolecular impurities, and obtain a clear filtrate. S3. The filtrate is concentrated to a volume concentration ratio of 10 to 40 times under low temperature conditions through a reverse osmosis membrane, with an operating pressure of 1.0 to 2.0 MPa, to obtain a concentrated plant beverage. S4. Fill the concentrated liquid into a pressure-resistant metal container, seal it with a one-way valve, and fill the container with nitrogen gas at 0.3~0.8MPa to maintain positive pressure inside the container. Then, perform high-temperature and high-pressure sterilization at 115~121℃. S5. Install a nozzle with an orifice diameter of 0.2~0.5 mm at the liquid outlet of the container. When pressed, the positive pressure of nitrogen in the tank will be used to spray out a non-atomized continuous liquid flow.

[0009] Furthermore, in step S1, the weight ratio of plant material to water is 1:5 to 1:20.

[0010] Furthermore, the plant materials in step S1 are selected from one or more of the following: Astragalus membranaceus, Codonopsis pilosula, Dioscorea opposita, Jujube, Dried ginger, Cinnamomum cassia, Lycium barbarum, Walnut kernel, Polygonatum odoratum, Ophiopogon japonicus, Lilium brownii, Mulberry, Poria cocos, Coix lacryma-jobi, White hyacinth bean, Tangerine peel, Mung bean, Dandelion, Lophatherum gracile, Hawthorn, Prunus persica, Rose, Citrus medica, Citronella arvense, Peppermint, Prunus mume, and Saposhnikovia divaricata.

[0011] Furthermore, the cyclic extraction in step S1 employs alternating or phased heating with gentle and strong heat, wherein the gentle heat temperature is 70~85℃ and the strong heat temperature is 95~105℃, and the extraction is performed multiple times; the extraction time is 30~120 min.

[0012] Furthermore, the charged nanofiltration membrane described in step S2 has a pore size of 0.01 μm, which can retain substances with a molecular weight greater than 500 Da, resulting in a filtrate contamination index of <3; the filtration operating pressure is 0.4~0.8 MPa, and the temperature is 15~35℃.

[0013] Furthermore, the low temperature condition mentioned in step S3 is 25~45℃; the molecular weight cut of the reverse osmosis membrane is 100~200 Da.

[0014] Furthermore, the pressure-resistant metal can in step S4 is an aluminum bottle, a stainless steel bottle, or a galvanized iron can; the one-way valve is an aerosol valve, and the nitrogen gas filled in has a purity of ≥99.9%.

[0015] Furthermore, in step S4, the F0 value of the high-temperature and high-pressure sterilization is ≥8, and the sterilization time is 15~40 min.

[0016] The present invention also provides a concentrated plant beverage for preservation under nitrogen positive pressure.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention employs a closed-loop extraction process involving alternating cycles of gentle heat (70-85℃) and strong heat (95-105℃) three times. The relatively low temperature gentle heat stage facilitates the full dissolution of volatile aromatic oils from the plant, while the high temperature strong heat stage promotes cell wall disruption, releasing more active ingredients. Combined with reverse osmosis low-temperature concentration, this avoids the damage to heat-sensitive components caused by traditional high-temperature vacuum concentration. The two processes work synergistically to achieve full-temperature protection. Using astragaloside A content and volatile oil yield as indicators, compared to the traditional atmospheric pressure boiling followed by vacuum concentration process, this invention can increase the astragaloside A retention rate by over 42% and the volatile oil retention rate by over 67%. Simultaneously, the closed-loop conditions further prevent the loss of volatile oils during the extraction process.

[0018] 2. This invention uses a charged nanofiltration membrane with a pore size of 0.01 μm for filtration before reverse osmosis concentration. Although the 0.01 μm pore size is close to the ultrafiltration range in some classifications, the nanofiltration membrane used in this invention is charged and can remove ions and small charged molecules through the Donnan effect, and has a retention effect on substances with a molecular weight of 500-1000 Da. This invention removes impurities such as colloids, pectin, and large protein molecules with a molecular weight greater than 500 Da from the extract using this charged nanofiltration membrane, reducing the filtrate's Solids Indication (SDI) to below 3, and removing more than 98% of colloids and impurities with a molecular weight >500 Da. Compared to existing technologies that only use conventional microfiltration or ultrafiltration as pretreatment, this invention significantly reduces the risk of organic fouling and colloidal clogging of the reverse osmosis membrane. The cleaning cycle of the reverse osmosis membrane is extended from 7 days after traditional microfiltration pretreatment to more than 60 days, greatly reducing operating costs and making it suitable for continuous industrial production.

[0019] 3. This invention involves filling the concentrated liquid into a pressure-resistant metal container, filling it with high-pressure nitrogen gas at 0.3~0.8 MPa, and sealing it with a one-way valve. After nitrogen sealing, the entire product is sterilized at 115~121℃ under high temperature and pressure, achieving an F0 value ≥8. After opening, simulating pressing twice daily for 30 consecutive days, the container still maintains positive pressure (≥0.1 MPa) with no detectable bacterial colonies, effectively preventing external bacteria-laden air from flowing back into the container through the one-way valve, ensuring the safety of the contents during the initial use period. Furthermore, the positive pressure environment inside the container and the high-temperature sterilization process together constitute a synergistic preservation mechanism: the high-pressure nitrogen gas expels oxygen from the container, preventing oxidation and rancidity of the contents; the high-temperature sterilization thoroughly kills any remaining microorganisms and spores in the container and the top space; and the positive pressure environment created inside the sealed container actively prevents external bacteria-laden air from flowing back into the container through the one-way valve after each use. After being stored at 37℃ and 75% relative humidity for 6 months (equivalent to 24 months at room temperature), the total bacterial count, mold, yeast and pathogenic bacteria were not detected in the product, and the peroxide value was far below the national standard limit.

[0020] 4. The present invention uses a nozzle with an aperture of 0.2~0.5 mm. When pressed, the concentrated liquid is sprayed out in a non-atomized continuous liquid flow form by utilizing the positive pressure of nitrogen in the can. Compared with the atomized spray of the spray pump head or the intermittent liquid output of the nozzle with the conduit under low pressure in the prior art, the non-atomized continuous liquid flow of the present invention reduces the instantaneous contact area between the liquid and the air. The loss rate of aroma substances (such as limonene and linalool) during the spraying process is reduced by 85%. At the same time, the liquid flow form makes it easy for consumers to directly drip into their mouths or accurately inject into a metered amount of water for dilution and drinking, thus taking into account both flavor preservation and ease of use.

[0021] 5. The various processes in this invention form an organic synergy: the high-precision nanofiltration pretreatment not only protects the reverse osmosis membrane but also endows the concentrate with good colloidal stability, providing a material basis for the terminal nozzle to remain unclogged during repeated use; the high-pressure nitrogen in the tank not only serves as a protective atmosphere during sterilization but also continuously provides a positive pressure barrier to prevent backflow after opening. Simultaneously, it acts as a power source, working with a specific aperture nozzle to achieve non-atomized continuous liquid flow injection, overcoming the shortcomings of existing low-pressure nitrogen filling schemes in maintaining positive pressure and the loss of aroma due to atomized extraction. The entire solution integrates low-temperature high-efficiency concentration, long-lasting aseptic preservation, and low-aroma extraction, covering the needs of concentrated plant beverages from industrial processing to the consumer experience. Detailed Implementation

[0022] The present invention will be further described below with reference to preferred embodiments. The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values. These ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed herein.

[0023] The low-temperature concentration process described in this invention refers to the operating temperature relative to the traditional thermal concentration process, and does not refer to a low-temperature environment that requires refrigeration equipment to maintain. The concentration temperature range of this invention is 25~45℃, which is the normal temperature range commonly referred to in the art, but it can be regarded as a low-temperature operation relative to the traditional high-temperature thermal concentration process. The formulation examples described in this invention and the following embodiments are not intended to exhaustively limit the range of plant materials that can be used in this invention. All concentrated plant beverages prepared using the methods of this invention and made from plants that are both medicinal and edible are within the scope of protection of this invention.

[0024] Unless otherwise specified, the experimental methods in the following embodiments are conventional methods, performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions.

[0025] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0026] Example 1 This embodiment provides a nitrogen-pressurized concentrated plant-based beverage, the raw materials of which are 12g Astragalus membranaceus, 10g Codonopsis pilosula, 15g Dioscorea opposita, 8g jujube, and 150g purified water. The process includes the following steps: S1. Mix the above-mentioned plant materials with water at a weight ratio of 1:12, place them in a sealed extraction tank, heat at 100°C for 20 minutes, then heat at 80°C for 70 minutes. After filtration, add 120 g of water to the residue and perform a second extraction using the same method. Add 100 g of water for the third extraction and complete the third extraction using the same method. Combine the three extracts and cool to 25°C. S2. The cooled extract is filtered through a charged nanofiltration membrane with a pore size of 0.01 μm (10 nm) at an operating pressure of 0.6 MPa and a temperature of 28°C to remove colloids and macromolecular impurities with a molecular weight greater than 500 Da, resulting in a clear filtrate. S3. The filtrate is concentrated to a volume concentration ratio of 20 times (1 / 20 of the original volume) through a polyamide composite reverse osmosis membrane at 30℃ and 1.6 MPa to obtain a concentrated plant beverage. The relatively low temperature conditions can prevent the volatilization of aroma components. S4. Fill the concentrated solution into a 100 mL aluminum bottle, seal it with an aerosol valve, and fill the bottle with 0.5 MPa of nitrogen (99.99% purity) to maintain positive pressure inside the bottle. Place it in an autoclave and autoclave it at 115°C for 30 min (F0 value ≥ 8). S5. Install a nozzle with an orifice diameter of 0.3 mm at the liquid outlet of the container. When pressed, the positive pressure of nitrogen gas in the tank will be used to spray out a non-atomized continuous liquid flow.

[0027] The resulting product is a clear, brownish-yellow liquid with a ginseng and astragalus aroma. Astragaloside A content and volatile oil yield were used as indicators for analysis; the astragaloside A retention rate reached 94%, and the volatile oil retention rate reached 96%. In the membrane concentration process, after pretreatment with a 0.01 μm charged nanofiltration membrane, the SDI of the reverse osmosis membrane decreased to below 3, and the cleaning cycle exceeded 60 days. The product has a shelf life of 18 months unopened at room temperature. After opening, simulating daily pressing and dispensing, no bacterial colonies were detected within 30 days at 25°C. No preservatives were added throughout the entire process.

[0028] Example 2 This embodiment provides a nitrogen positive pressure preservation concentrate for plant beverages, the raw materials of which are 8 g dried ginger, 5 g cinnamon, 10 g goji berries, 12 g walnut kernels, and 160 g purified water.

[0029] Referring to the preparation method described in Example 1: In step S1 of this example, the weight ratio of plant material to water is 1:9; the heating temperature is 105℃ for 15 min, followed by 85℃ for 80 min; in step S2, the filtration pressure is 0.4 MPa and the temperature is 35℃; in step S3, the filtrate is concentrated at 35℃ and 1.75 MPa to 1 / 30 of its original volume, i.e., a volume concentration ratio of 30 times; in step S4, the concentrated liquid is filled into a stainless steel bottle, filled with nitrogen at 0.6 MPa, and then sterilized at 121℃ for 20 min; in step S5, the nozzle orifice diameter is 0.3 mm. The remaining conditions and operating steps are the same as in Example 1 and will not be repeated here.

[0030] The resulting product is a light brown liquid with a ginger and cinnamon aroma, and has a shelf life of up to 15 months at room temperature.

[0031] Example 3 This embodiment provides a nitrogen positive pressure preservation plant beverage concentrate, the raw materials of which are 12 g of Solomon's seal, 10 g of Ophiopogon japonicus, 15 g of lily bulb, 10 g of mulberry, and 180 g of purified water.

[0032] Referring to the preparation method described in Example 1: In step S1 of this example, the weight ratio of plant material to water is 1:14; the heating temperature is 98℃ for 25 min, followed by simmering at 75℃ for 75 min; in step S2, the filtration operation pressure is 0.8 MPa and the temperature is 15℃; in step S3, the filtrate is concentrated at 28℃ and 1.45 MPa to 1 / 25 of its original volume, i.e., a volume concentration ratio of 25 times; in step S4, the concentrated liquid is filled into a galvanized iron can, filled with nitrogen at 0.4 MPa, and then sterilized at 115℃ for 30 min; in step S5, the nozzle orifice diameter is 0.2 mm. The remaining conditions and operating steps are the same as in Example 1 and will not be repeated here.

[0033] The resulting product is clear and slightly sweet, and has a shelf life of up to 18 months at room temperature.

[0034] Example 4 This embodiment provides a nitrogen positive pressure preservation concentrate for plant-based beverages, the raw materials of which are 15 g of Poria cocos, 15 g of Coix lacryma-jobi, 10 g of white hyacinth bean, 6 g of dried tangerine peel, and 200 g of purified water.

[0035] Following the preparation method described in Example 1: In step S1, the weight ratio of plant material to water is 1:7; heating is carried out at 95°C for 30 min, followed by simmering at 70°C for 90 min; in step S2, the filtration operation pressure is 0.45 MPa and the temperature is 33°C; in step S3, the filtrate is concentrated at 35°C and 1.85 MPa to 1 / 40 of its original volume, i.e., a volume concentration ratio of 40 times; in step S4, nitrogen gas is introduced at 0.7 MPa, followed by sterilization at 121°C for 20 min; in step S5, the nozzle orifice diameter is 0.35 mm. The remaining conditions and operating steps are the same as in Example 1 and will not be repeated here.

[0036] The resulting product has a refreshing taste and a shelf life of up to 18 months at room temperature.

[0037] Example 5 This embodiment provides a nitrogen positive pressure preservation plant beverage concentrate, the raw materials of which are 15 g of coix seed, 12 g of mung bean, 8 g of dandelion, 6 g of bamboo leaf, and 170 g of purified water.

[0038] Referring to the preparation method described in Example 1: In step S1 of this example, the weight ratio of plant material to water is 1:16; the heating temperature is 100℃ for 20 min, followed by 80℃ for 60 min; in step S2, the filtration pressure is 0.75 MPa and the temperature is 18℃; in step S3, the filtrate is concentrated at 32℃ and 1.3 MPa to 1 / 35 of its original volume, i.e., a volume concentration ratio of 35 times; in step S4, nitrogen gas is introduced at 0.55 MPa, followed by sterilization at 118℃ for 25 min; in step S5, the nozzle orifice diameter is 0.28 mm. The remaining conditions and operating steps are the same as in Example 1 and will not be repeated here.

[0039] The resulting product has a refreshing taste and a shelf life of up to 16 months at room temperature.

[0040] Example 6 This embodiment provides a nitrogen positive pressure preservation concentrate for plant beverages, the raw materials of which are 15 g hawthorn, 6 g peach kernel, 8 g rose petals, 5 g dried tangerine peel, and 160 g purified water.

[0041] Referring to the preparation method described in Example 1: In step S1 of this example, the weight ratio of plant material to water is 1:5; the heating temperature is 102℃ for 20 min, followed by simmering at 78℃ for 65 min; in step S2, the filtration operation pressure is 0.5 MPa and the temperature is 30℃; in step S3, the filtrate is concentrated at 38℃ and 2.0 MPa to 1 / 15 of its original volume, i.e., a volume concentration ratio of 15 times; in step S4, nitrogen gas is introduced at 0.45 MPa, followed by sterilization at 116℃ for 28 min; in step S5, the nozzle orifice diameter is 0.22 mm. The remaining conditions and operating steps are the same as in Example 1 and will not be repeated here.

[0042] The resulting product is a light reddish-brown clear liquid with a shelf life of up to 14 months at room temperature.

[0043] Example 7 This embodiment provides a nitrogen positive pressure preservation concentrate for plant beverages, the raw materials of which are 12 g of Buddha's Hand, 10 g of Citron, 10 g of Rose, 6 g of Peppermint, and 150 g of purified water.

[0044] Following the preparation method described in Example 1: In step S1, the weight ratio of plant material to water is 1:20; heating is carried out at 97°C for 15 min, followed by simmering at 72°C for 50 min (mint is added in the last 10 min); in step S2, the filtration operation pressure is 0.7 MPa and the temperature is 21°C; in step S3, the filtrate is concentrated at 25°C and 1.0 MPa to 1 / 10 of its original volume, i.e., a volume concentration ratio of 10 times; in step S4, nitrogen gas is introduced at 0.3 MPa, followed by sterilization at 115°C for 30 min; in step S5, the nozzle orifice diameter is 0.5 mm. The remaining conditions and operating steps are the same as in Example 1 and will not be repeated here.

[0045] The resulting product has a refreshing taste, and adding the peppermint at the end helps retain its volatile menthol components. It has a shelf life of up to 12 months at room temperature.

[0046] Example 8 This embodiment provides a nitrogen positive pressure preservation concentrate for plant beverages, the raw materials of which are 10 g of dried plum, 8 g of saposhnikovia root, 10 g of astragalus root, 12 g of red dates, and 160 g of purified water.

[0047] Referring to the preparation method described in Example 1: In step S1 of this example, the weight ratio of plant material to water is 1:18; the heating temperature is 100℃ for 20 min, followed by 80℃ for 70 min; in step S2, the filtration pressure is 0.55 MPa and the temperature is 24℃; in step S3, the filtrate is concentrated at 35℃ and 1.15 MPa to 1 / 20 of its original volume, i.e., a volume concentration ratio of 20 times; in step S4, nitrogen gas is introduced at 0.8 MPa, followed by sterilization at 121℃ for 20 min; in step S5, the nozzle orifice diameter is 0.3 mm. The remaining conditions and operating steps are the same as in Example 1 and will not be repeated here.

[0048] The resulting product has a mild taste and a shelf life of up to 18 months at room temperature.

[0049] Comparative Example 1 This comparative example provides a concentrated plant beverage prepared using traditional methods, with the following ingredients: 12g Astragalus membranaceus, 10g Codonopsis pilosula, 15g Dioscorea opposita, 8g jujube, and 150g purified water.

[0050] In step S1 of this comparative example, the above-mentioned plant raw materials are mixed with water at a weight ratio of 1:12, and boiled under normal pressure (100°C, 2 h), and filtered through four layers of gauze, replacing the step of three rounds of closed-loop extraction with alternating low and high heat in Example 1; nanofiltration membrane filtration in step S2 is not performed; in step S3, vacuum concentration is performed at a temperature of 80°C, concentrating to 1 / 20 of the original volume, i.e., a volume concentration ratio of 20 times, replacing the low-temperature concentration with reverse osmosis membrane in Example 1; in step S4, the concentrate is filled into glass bottles, sealed with screw caps, and pasteurized (85°C, 30 minutes) without nitrogen filling, replacing the filling into pressure-resistant metal cans and filling with nitrogen gas in Example 1, sealing with a one-way valve, and sterilizing under high temperature and high pressure; in step S5, the nozzle is not installed, replacing the 0.3 mm nozzle in Example 1.

[0051] The product had a astragaloside A retention rate of only 52% and a volatile oil retention rate of 29%. After being placed at 37°C for 3 months, precipitation and bottle swelling occurred, and the total bacterial count exceeded the standard within 24 hours after opening.

[0052] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing a concentrated plant-based beverage using nitrogen positive pressure preservation, characterized in that, Includes the following steps: S1. Mix the plant material with water, perform a circulating extraction under closed conditions, combine the extracts and cool them; S2. Filter the cooled extract through a charged nanofiltration membrane to remove colloidal and macromolecular impurities, and obtain a clear filtrate. S3. The filtrate is concentrated to a volume concentration ratio of 10 to 40 times under low temperature conditions through a reverse osmosis membrane, with an operating pressure of 1.0 to 2.0 MPa, to obtain a concentrated plant beverage. S4. Fill the concentrated liquid into a pressure-resistant metal container, seal it with a one-way valve, and fill the container with nitrogen gas at 0.3~0.8 MPa to maintain positive pressure inside the container. Then, perform high-temperature and high-pressure sterilization at 115~121℃. S5. Install a nozzle with an orifice diameter of 0.2~0.5 mm at the liquid outlet of the container. When pressed, the positive pressure of nitrogen in the tank will be used to spray out a non-atomized continuous liquid flow.

2. The method for preparing a concentrated plant beverage preservative under nitrogen positive pressure according to claim 1, characterized in that, In step S1, the weight ratio of plant material to water is 1:5 to 1:

20.

3. The method for preparing a concentrated plant beverage preservative under nitrogen positive pressure according to claim 1, characterized in that, The plant materials in step S1 are selected from one or more of the following: Astragalus membranaceus, Codonopsis pilosula, Dioscorea opposita, Jujube, Dried ginger, Cinnamomum cassia, Lycium barbarum, Walnut kernel, Polygonatum odoratum, Ophiopogon japonicus, Lilium brownii, Mulberry, Poria cocos, Coix lacryma-jobi, White hyacinth bean, Tangerine peel, Mung bean, Dandelion, Lophatherum gracile, Hawthorn, Prunus persica, Rose, Citrus medica, Citronella arvense, Peppermint, Prunus mume, and Saposhnikovia divaricata.

4. The method for preparing a concentrated plant beverage preservative under nitrogen positive pressure according to claim 1, characterized in that, The cyclic extraction in step S1 uses alternating or phased heating with gentle and strong heat, wherein the gentle heat temperature is 70~85℃ and the strong heat temperature is 95~105℃, and the extraction is repeated multiple times; the extraction time is 30~120 min.

5. The method for preparing a concentrated plant beverage preservative under nitrogen positive pressure according to claim 1, characterized in that, The charged nanofiltration membrane described in step S2 has a pore size of 0.01 μm, which can retain substances with a molecular weight greater than 500 Da, so that the pollution index of the filtrate is <3; the filtration operating pressure is 0.4~0.8 MPa, and the temperature is 15~35℃.

6. The method for preparing a concentrated plant beverage preservative under nitrogen positive pressure according to claim 1, characterized in that, The low temperature conditions mentioned in step S3 are 25~45℃; the molecular weight cut of the reverse osmosis membrane is 100~200 Da.

7. The method for preparing a concentrated plant beverage preservative under nitrogen positive pressure according to claim 1, characterized in that, The pressure-resistant metal can mentioned in step S4 is an aluminum bottle, a stainless steel bottle, or a galvanized iron can; the one-way valve is an aerosol valve, and the nitrogen gas filled in has a purity of ≥99.9%.

8. The method for preparing a concentrated plant beverage preservative under nitrogen positive pressure according to claim 1, characterized in that, In step S4, the F0 value of high-temperature and high-pressure sterilization is ≥8, and the sterilization time is 15~40 min.

9. A concentrated plant-based beverage preservative using nitrogen positive pressure, characterized in that, It is prepared by any one of the preparation methods described in claims 1-8.