Fresh-keeping packaging method and system for brasenia schreberi tender shoots

Abstract

The invention relates to the technical field of fresh-keeping packaging of brasenia schreberi tender shoots, in particular to a fresh-keeping packaging method and system for brasenia schreberi tender shoots. The method comprises the following steps: pretreating brasenia schreberi tender shoots to induce pore closing of the brasenia schreberi tender shoots; performing glue protection treatment to form a composite glue protection film on the surfaces of the tender shoots; loading the treated brasenia schreberi tender shoots into a tender shoot packaging box integrated with a controlled atmosphere microcapsule release unit, and sealing, so as to realize shape integrity preservation of the brasenia schreberi tender shoots; sequentially carrying out water bath and ultrahigh pressure sterilization on the sealed tender shoot packaging box; and finally, refrigerating to realize fresh-keeping packaging of the brasenia schreberi tender shoots. On the basis of a box body structure of a multi-layer composite structure, in cooperation with an inner wall anti-sticking design and a built-in controlled atmosphere microcapsule release unit system, morphological integrity preservation of brasenia schreberi tender shoots is achieved, non-acidification and chemical preservative-free high-quality preservation can be achieved in combination with glue protection treatment and gradient physical sterilization of the brasenia schreberi tender shoots, and the preservation effect of the brasenia schreberi tender shoots is improved. And the colloid retention rate is greater than 95%.

Description

Technical Field

[0001] This invention relates to the field of preservation and packaging technology for tender shoots of water shield, and in particular to a method and system for preservation and packaging tender shoots of water shield. Background Technology

[0002] Water shield, especially its tender shoots, is a high-value aquatic vegetable, rich in mucilage and various nutrients. However, its post-harvest physiological activity is vigorous, mainly manifested in high respiration intensity and rapid transpiration water loss, and its surface mucilage layer is extremely easily damaged, leading to rapid browning, softening, and rotting of the tender shoots during storage and transportation, with a shelf life of usually less than a week.

[0003] Currently, the industry mainly relies on two types of traditional techniques for preserving tender shoots of water shield: 1. Chemical treatment methods, such as acid soaking. Although this method can inhibit microorganisms, it will cause the loss of the characteristic gum on the surface of the tender shoots through hydrolysis, and irreversibly change its inherent flavor and texture, failing to meet the market's demand for "no chemical additives, maintaining original flavor" and authentic taste.

[0004] 2. Physical storage methods, such as deep freezing. Although this method can preserve the buds for a long time, it is energy-intensive, and after thawing, the buds become limp and sap seeps out severely, resulting in significant quality deterioration and a substantial reduction in commercial value.

[0005] In recent years, although some studies have attempted to use conventional modified atmosphere packaging, it typically requires complex external gas filling equipment to maintain specific gas ratios (such as low O2 and high CO2), resulting in high equipment investment, complex operation, and difficulty in achieving dynamic and adaptive adjustment of gas concentration inside the packaging. Therefore, developing a packaging solution that can automatically maintain a preservation gas environment under ordinary cold chain conditions without chemical additives, while maximizing the preservation of the morphology, gelatinous texture, and flavor integrity of water shield shoots, has become a pressing technical challenge in this field. Summary of the Invention

[0006] This invention aims to overcome the shortcomings of existing technologies that rely on chemical additives or complex external modified atmosphere packaging for preservation. To this end, this invention provides a method and system for preserving and packaging tender shoots of water shield (Brasenia schreberi), aiming to achieve long-term, high-quality preservation of tender shoots of water shield without the need for chemical preservatives or external modified atmosphere packaging.

[0007] The technical solution of the present invention is as follows: A method for preserving and packaging tender shoots of water shield, comprising: Pretreatment of tender shoots of water shield: Freshly harvested tender shoots of water shield are pretreated to induce stomata closure and inhibit postharvest respiration. Protective coating treatment: A mixed aqueous solution containing sodium alginate and hydroxypropyl methylcellulose (HPMC) is evenly sprayed onto the surface of pretreated water shield shoots, followed by immersion in a 1%–2% (by mass / volume) calcium chloride aqueous solution for 1–3 minutes; wherein the mass concentration of sodium alginate in the mixed aqueous solution is 0.5%–1.5%, and the mass concentration of hydroxypropyl methylcellulose (HPMC) is 0.2%–1.0%. Packaging and sealing: Pack the water shield sprouts, after the protective coating is applied, into special sprout packaging boxes and seal them. The filling volume should be 65% to 70% of the internal volume of the packaging box. Gradient sterilization process: The sealed packaging box is subjected to short-time heat sterilization and ultra-high pressure cold sterilization in sequence; the short-time heat sterilization is water bath sterilization, and the process conditions are: temperature 85℃~88℃, time 8 seconds~12 seconds; the process conditions for ultra-high pressure cold sterilization are: pressure controlled at 320MPa~340MPa, time controlled at 25 seconds~35 seconds; Cold storage: The sterilized packaging boxes are placed in an environment of 0℃~4℃ to preserve the tender shoots of water shield.

[0008] Furthermore, a dedicated sprout packaging box for implementing the above method is provided. The packaging box includes a box body and a lid. The box body has a hollow cavity with a top opening, and its walls are sequentially laminated from the outside to the inside with an outer oxygen-barrier membrane, a middle functional interlayer, and an inner antibacterial membrane. The lid is sealed to the top of the box body to form a closed packaging unit. The sprout packaging box also includes the following functional structures: Selective breathable membrane window: disposed on the side wall of the box, which is a polymer membrane with a higher carbon dioxide (CO2) permeability than oxygen (O2) permeability; Humidity regulating layer: Adhered to the inner side wall of the box, made of sodium carboxymethyl cellulose (CMC) material, with a thickness of 0.4 mm to 0.6 mm; Modified atmosphere microcapsule release unit: uniformly dispersed within the intermediate functional interlayer, the wall material of the unit has humidity-responsive characteristics, and the interior is encapsulated with citric acid-sodium bicarbonate reactants; when the humidity inside the box reaches a preset threshold, the wall material responds and ruptures, triggering the release of carbon dioxide (CO2) gas from the reactants. Anti-stick bumps: evenly distributed on the inner surface of the inner antibacterial film, the bumps are hemispherical, the texture height is 0.2 mm to 0.3 mm, and the spacing between adjacent bumps is 0.8 mm to 1.2 mm; preferably, the bumps and the inner antibacterial film are integrally formed.

[0009] Furthermore, the key components of the sprout packaging box are defined as follows: The outer oxygen barrier membrane is a biodegradable blend of polylactic acid (PLA) and starch, wherein the starch content is 28%–32% by mass. The membrane thickness is 0.03 mm–0.08 mm, and its oxygen permeability is 1% under conditions of 23°C and 50% relative humidity. ~5 .

[0010] In the intermediate functional interlayer, the particle size of the modified atmosphere microcapsule release unit (i.e., microcapsule) is 40 micrometers to 60 micrometers, and the distribution density in the interlayer is 1800 particles / cm³ to 2200 particles / cm³.

[0011] Furthermore, the key process parameters in the method are limited as follows: During the protective coating process, the mixed solution is sprayed out using a high-pressure spray head, with a spray particle size of 30 micrometers to 50 micrometers.

[0012] The main beneficial effects of this invention are as follows: 1. Comprehensive Preservation for Superior Quality: Through a synergistic process chain of "pretreatment - gum preservation - intelligent modified atmosphere - gradient sterilization - refrigeration," the morphology, gum content, color, and flavor of water shield sprouts are comprehensively protected without the use of acidifiers or chemical preservatives. Experiments show that water shield sprouts treated with this invention retain more than 95% of their gum content after 45 days of storage at 0℃~4℃, maintaining their morphology intact, and the total number of microorganisms is effectively controlled.

[0013] 2. High integration and adaptive adjustment significantly reduce overall costs: The core innovation lies in the highly integrated humidity-responsive adaptive modified atmosphere system in the sprout packaging box. This system automatically triggers and releases CO2 based on changes in the humidity of the microenvironment inside the box to inhibit sprout respiration, completely eliminating the need for expensive and bulky external modified atmosphere filling equipment. Through this built-in, self-regulating preservation mechanism, efficient and stable preservation is achieved while significantly reducing equipment investment and operating energy consumption.

[0014] 3. Scientifically designed and suitable for industrial application: The protective coating treatment enhances the physical strength of the tender shoots, ensuring a smooth transition to high-intensity sterilization. The gradient sterilization process, combining short-time heat sterilization at 85℃~88℃ with ultra-high pressure cold sterilization at 320MPa~340MPa, minimizes damage to heat-sensitive components and textures while achieving efficient sterilization. The entire solution has clearly defined parameters, strong consistency, and is fully compatible with modern continuous food production lines, demonstrating excellent prospects for industrial application.

[0015] Based on the same inventive concept, the present invention also provides a packaging system for preserving tender shoots of water shield. This system is configured to perform the packaging method for preserving tender shoots of water shield as described in any of the preceding claims, and particularly includes a dedicated equipment unit for realizing the humidity-responsive modified atmosphere and gradient sterilization functions.

[0016] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

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

[0018] Figure 1 This is a process flow diagram of a method for preserving and packaging tender shoots of water shield provided in an embodiment of the present invention; Figure 2 This is a cross-sectional view of the overall structure of a sprout packaging box provided in one embodiment of the present invention; Figure 3 yes Figure 2 A partially enlarged schematic diagram of the wall structure of the middle box; Figure 4 This is a schematic diagram showing the distribution of raised dot texture on the inner surface of the antibacterial film of the tender sprout packaging box according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the structure of a modified atmosphere microcapsule release unit provided in one embodiment of the present invention; Figure 6 This is a schematic diagram of the gas release mechanism of the modified atmosphere microcapsule release unit under humidity triggering, provided in an embodiment of the present invention.

[0019] Figure label: 1. Box body, 2. Box lid, 3. Selective breathable membrane window, 4. Humidity regulating layer, 5. Outer oxygen barrier membrane, 6. Middle functional interlayer, 7. Inner antibacterial membrane, 8. Raised dots, 9. Modified atmosphere microcapsule release unit, 10. Humidity-responsive wall material. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0021] It should be noted that in the description of this invention, the terms "installation," "connection," and "fixing," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integrally formed connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0022] Furthermore, the terms “first”, “second”, etc., are used for descriptive purposes only to distinguish different objects and should not be construed as indicating or implying relative importance, order of precedence, or quantity limitation.

[0023] Unless otherwise expressly specified and limited, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terms “comprising,” “including,” or similar terms used herein are intended to cover a non-exclusive inclusion, meaning that they include the expressly listed elements but do not exclude the inclusion of other elements not expressly listed, or elements inherent to the method, product, or apparatus.

[0024] For ease of description, the accompanying drawings may only show some of the structures relevant to the present invention, rather than all of them.

[0025] Example 1 This embodiment provides a method for preserving and packaging tender shoots of water shield. This method is a specific implementation of the technical solution of the present invention and is used to describe it in detail, but it is not intended to limit the scope of protection of the present invention.

[0026] Please see Figure 1 The method specifically includes the following steps: S1: Pretreatment of tender shoots of water shield: Fresh tender shoots of water shield after harvest are treated with carbon dioxide (CO2) gas with a volume concentration of 20% for 4 minutes to induce stomata closure and thus inhibit post-harvest respiration. S2: Protective Treatment: Prepare a mixed aqueous solution of sodium alginate and hydroxypropyl methylcellulose (HPMC), wherein the mass concentration of sodium alginate is 1.0% and the mass concentration of HPMC is 0.5%. Spray this mixed solution evenly onto the surface of the pretreated water shield shoots using a high-pressure spray nozzle (spray particle size approximately 40 micrometers). Immediately afterwards, immerse the sprayed shoots in a 1.5% calcium chloride (CaCl2) aqueous solution for 2 minutes.

[0027] Mechanism of protective film formation: During the soaking process, the carboxyl groups in the sodium alginate molecular chain undergo ionic cross-linking with calcium ions in the solution, rapidly forming a three-dimensional network gel structure, which constitutes the basic framework of the protective film; at the same time, hydroxypropyl methylcellulose (HPMC) in the mixed solution interweaves with the sodium alginate network through intermolecular interactions, effectively enhancing the film's flexibility, mechanical strength and adhesion to the surface of the sprout.

[0028] After soaking, remove and drain, and a calcium alginate-hydroxypropyl methylcellulose composite protective film mainly composed of ion cross-linking is formed on the surface of the tender shoots; S3: Packaging and Sealing: Prepare special packaging boxes for the sprouts (the specific structure is described later). Figure 2 The tender shoots of water shield, after being treated with protective adhesive, are placed into the box. During filling, the total volume of the water shield shoots should be controlled to occupy approximately 68% of the internal volume of the packaging box. Then, the box lid is closed and sealed using a heat-sealing method to complete the packaging.

[0029] The intermediate functional interlayer of the sprout packaging box integrates citric acid-sodium bicarbonate microcapsules (i.e., modified atmosphere microcapsule release units). In this embodiment, the average particle size of the modified atmosphere microcapsule release units is approximately 50 micrometers, and the distribution density in the interlayer is approximately 2000 particles / cubic centimeter. S4: Gradient sterilization treatment: The sealed bud packaging boxes are sequentially subjected to short-time heat sterilization and ultra-high pressure cold sterilization. (1) Short-time heat sterilization: The packaging box is passed through a water bath sterilization tank at a temperature of 86℃ for 10 seconds; (2) Ultra-high pressure cold sterilization: Immediately transfer the packaging box after water bath treatment into the ultra-high pressure equipment and treat it under a pressure of 330MPa for 30 seconds.

[0030] S5: Cold storage: Store the packaging boxes of the tender shoots after gradient sterilization in a low-temperature environment of 4℃.

[0031] It should be noted that this embodiment provides a specific packaging box for tender shoots, which is applied to the above-mentioned method for preserving and packaging tender shoots of water shield. Please refer to the relevant documentation for further details. Figures 2 to 5 ,include: Box 1 has a hollow cavity with a top opening. The wall of box 1 consists of an outer oxygen barrier membrane 5, a middle functional interlayer 6, and an inner antibacterial membrane 7, from the outside to the inside. The three membranes are fixedly connected by a hot-pressing composite process.

[0032] It should be noted that the outer oxygen barrier membrane 5 is a biodegradable blend of polylactic acid (PLA) and starch, with a starch content of 30% by mass. The membrane thickness is 0.05 mm. Under conditions of 23°C and 50% relative humidity, its oxygen permeability is 3. .

[0033] Intermediate functional layer 6: It contains uniformly dispersed and integrated modified atmosphere microcapsule release units 9, forming a microcapsule functional layer. In this embodiment, the average particle size of the microcapsules is approximately 50 micrometers, and the distribution density in this interlayer is approximately 2000 particles / cubic centimeter.

[0034] Inner antibacterial membrane 7: A water-soluble membrane made of a blend of konjac glucomannan and chitosan, with a thickness of 0.025 mm. This membrane is uniformly embedded with… Polylysine sustained-release microparticles, the The designed daily release rate of polylysine is 0.08–0.12 mg / day. .

[0035] The lid 2 is sealed to the top of the box body 1 by heat sealing to form a sealed packaging unit; A selectively breathable membrane window 3 is embedded in the side wall of the housing 1. It is a polymer membrane with a higher permeability to carbon dioxide than to oxygen. A humidity regulating layer 4 is fitted onto the inner wall of the box body 1, offset from the selectively breathable membrane window 3. This layer is made of sodium carboxymethyl cellulose (CMC) material and has a thickness of 0.5 mm. It is used to dynamically adsorb or release moisture to balance the humidity inside the packaging. like Figure 4 As shown, a plurality of hemispherical protrusions 8 are evenly distributed on the inner surface of the inner antibacterial film 7. The protrusions 8 and the inner antibacterial film 7 are integrally formed. In this embodiment, the texture height of the protrusions is 0.25 mm, and the spacing between adjacent protrusions is 1.0 mm; like Figure 5 and Figure 6 As shown, the modified atmosphere microcapsule release unit 9 is composed of a wall material 10 (i.e., microcapsule wall) with humidity-responsive properties encapsulating a citric acid-sodium bicarbonate reactant. When the internal humidity of the box 1 is below a preset threshold, the unit is in a stable state; when the internal humidity rises and reaches the preset threshold (in this embodiment, the threshold is approximately 95%), the wall material 10 swells and ruptures due to the humidity response, triggering the internal reactants to react and thus continuously and slowly releasing carbon dioxide gas. The released carbon dioxide gas can effectively inhibit the respiration of the tender shoots of water shield inside the box and, in conjunction with the selectively breathable membrane window 3, maintain a suitable preservation gas environment.

[0036] The humidity response threshold design is based on the following: The humidity response threshold of the modified atmosphere microcapsule release unit is set at 85%–95%. This is designed based on the physiological characteristics of water shield shoots after harvest, where respiration is significantly enhanced in high humidity environments (>90% RH), accompanied by rapid increase in humidity inside the packaging due to transpiration and water loss. This threshold range ensures that the microcapsules activate promptly when the humidity inside the packaging rises to a level unfavorable for preservation due to the respiration and transpiration of the shoots, releasing CO2 to inhibit respiration, thereby achieving adaptive supply of preservative gas and avoiding premature or delayed response.

[0037] To verify the inner antibacterial membrane To determine whether the sustained-release properties of polylysine met the design requirements, a simulated food contact migration test was conducted based on the General Rules for Migration Testing of Food Contact Materials and Articles in the National Food Safety Standard.

[0038] Test conditions Simulated solution: 3% (w / v) acetic acid solution (simulating an acidic food environment); Temperature: 4℃ (simulating actual refrigeration conditions); Time: Continuous monitoring until day 7; Sample: The inner antibacterial membrane material prepared according to the formula of this embodiment was cut into standard test pieces of 10cm×10cm.

[0039] Test methods The test piece was completely immersed in 200 mL of simulated solution, and samples were taken on days 1, 3, 5, and 7. High-performance liquid chromatography (HPLC) was used to determine the concentration of the substance in the simulated solution. Concentration of polylysine.

[0040] Calculation results Based on the measured concentration, the daily release per unit area was calculated. After three parallel experiments, the inner antibacterial film, at 4°C, [achieved optimal results]. The average daily release of polylysine is 0.10±0.02 mg / cm², and the test results consistently fall within the range of 0.08 to 0.12 mg / cm² described in this invention.

[0041] Technical Effect Description This slow-release formulation continuously and slowly releases antibacterial components throughout the refrigeration period, effectively inhibiting the growth of common spoilage bacteria (such as Pseudomonas and Lactobacillus) and pathogenic bacteria (such as Escherichia coli and Staphylococcus aureus) during the storage and transportation of water shield sprouts. Sensory evaluation shows that it does not negatively affect the inherent flavor of water shield sprouts.

[0042] To verify the overall preservation effect of the method described in this embodiment, a comparative experiment was conducted with two traditional preservation methods.

[0043] The process described in steps S1 to S5 above is used for processing. Key process points are summarized below: Pretreatment: 20% CO2 (volume concentration) treatment for 4 minutes.

[0044] Protective coating treatment: Spray with a mixed solution containing 1.0% sodium alginate and 0.5% HPMC (spray particle size approximately 40 micrometers), then soak in 1.5% CaCl2 solution for 2 minutes.

[0045] Packaging: Use Figure 2 The packaging box shown has a filling rate of approximately 68%, and contains citric acid-sodium bicarbonate microcapsules with an average particle size of approximately 50 micrometers and a distribution density of approximately 2000 particles / cubic centimeter.

[0046] Sterilization: Sterilize in an 86℃ water bath for 10 seconds, followed immediately by ultra-high pressure treatment at 330MPa for 30 seconds.

[0047] Storage: Store in a cold storage at 4℃.

[0048] Comparative Example 1 (Acid Pickling Method): Simulating traditional chemical preservation processes. Fresh water shield sprouts were directly soaked in a 1.5% citric acid aqueous solution for 10 minutes, drained, packed into ordinary polyethylene (PE) plastic boxes and sealed, then sterilized in a water bath at 85°C for 10 minutes, and finally refrigerated at 4°C.

[0049] Comparative Example 2 (Quick Freezing Method): Simulating traditional physical preservation processes. Fresh water shield shoots were directly packed into polyethylene (PE) bags and quick-frozen at -35°C to a core temperature of -18°C, then transferred to a -18°C cold storage. Before consumption, they were slowly thawed in 4°C air for approximately 12 hours.

[0050] To objectively evaluate the preservation effect of the method of the present invention, the tender shoots of water shield treated by the method of the present invention (Example 1) and two comparative examples (acid pickling method and quick-freezing method) were tested for key quality and safety indicators at specified storage time points (30 days and 45 days). The specific comparison results are shown in Table 1 below. The experimental conditions, testing methods and data processing methods followed in the comparative experiments are uniformly described as follows.

[0051] Table 1 Comparison of Preservation Effects Note: For details on the specific experimental conditions, methods, and data statistics for each detection indicator, please refer to the following text.

[0052] Experimental conditions 1) Test sample size All experimental groups (the embodiments of this invention, Comparative Example 1, and Comparative Example 2) were set up with 3 independent parallel experimental groups, each containing 10 complete packaging units, i.e., the total sample size n=30. The data in the table are the arithmetic mean of the results of the three parallel groups, and the standard deviation range of the gel retention rate and the total number of microorganisms is also given.

[0053] 2) Core experimental conditions Storage conditions: All packaged products were placed in a constant temperature and humidity incubator at a temperature of (4±0.5)℃ and a relative humidity of (85±5)% to simulate a commercial cold chain storage environment.

[0054] Testing time points: Sampling and testing were conducted after 30 days and 45 days of continuous storage.

[0055] Special treatment conditions (for example 2 only): Before testing, the sample was placed in an environment of (4±1)℃ for 12 hours to slowly thaw, and the various indicators were measured immediately after complete thawing.

[0056] Detection methods Pectin retention rate (%): Referencing the principle of uronic acid content determination in "NY / T 2016-2011 Determination of Pectin Content in Fruits and Their Products," and adapted and optimized for water shield pectin. Specifically, hot water extraction and alcohol precipitation purification were performed, followed by determination of uronic acid content in the extract using the sulfuric acid-carbazole colorimetric method, thus characterizing the relative pectin content. The relative pectin content of samples before and after storage was determined, and calculated using the formula: Pectin retention rate (%) = (Pectin content after storage / Initial pectin content before storage) × 100%.

[0057] Total microbial count (CFU / g): Strictly follow the procedure outlined in GB / T4789.2-2008 Food Hygiene Microbiology Examination: Determination of Total Colony Count.

[0058] Appearance and morphology: Three uniformly trained evaluators conducted blind evaluations under a standard light source box (D65 light source), focusing on recording typical quality deterioration phenomena such as browning, softening, and juice seepage.

[0059] Comprehensive cost (RMB / kg): Based on the pilot production scale (calculated at 100kg / batch), the cost covers the main raw materials, special packaging materials, production energy consumption and equipment depreciation, but does not include labor and logistics costs.

[0060] Data Statistical Processing One-way ANOVA was performed on the experimental data using SPSS 22.0 statistical software. Different letter symbols in the results graph indicate statistical significance at the P < 0.05 level.

[0061] As shown in Table 1, the method of the present invention (Example 1) has achieved the following significant effects: Extremely high gelatin retention rate: After 45 days of storage, the gelatin retention rate is still greater than 95%, which is much higher than that of pickling (60%-70%) and quick-freezing (80%-85%), effectively preserving the core nutrients and taste characteristics of water shield tender shoots.

[0062] Excellent shape and color retention: Throughout the entire storage period, the sprouts remain intact, bright in color, and without obvious browning, wilting, or loss of thawed juice. The appearance quality of the product is significantly better than the two comparison samples.

[0063] Effective microbial control: The total number of microorganisms in the final product is controlled at 5 × 10⁻⁶. 2 Below CFU / g, significantly lower than that of the acid pickling method (≥10). 5 The CFU / g indicates that the gradient sterilization process of the present invention, combined with the built-in antibacterial membrane, provides excellent microbial safety assurance.

[0064] Significant overall cost advantages: The overall cost of the method of this invention is approximately RMB 7.2 / kg, which is lower than that of the acid pickling method (RMB 8.5 / kg) and far lower than that of the quick-freezing method (RMB 12.0 / kg). It achieves high-quality preservation while also providing good economic benefits.

[0065] In summary, this embodiment 1 demonstrates through specific process parameters and comparative experiments that the method for preserving and packaging tender shoots of water shield provided by the present invention, through the coordinated process of "pretreatment - gelatin protection - intelligent modified atmosphere packaging - gradient sterilization - refrigeration", can achieve high-quality preservation of tender shoots of water shield for up to 45 days without the need for chemical acidifiers and complex external equipment. It shows outstanding advantages in terms of gelatin preservation, morphological maintenance, microbial safety and cost control.

[0066] Example 2 This embodiment provides a packaging system for preserving tender shoots of water shield, wherein a method for preserving and packaging tender shoots of water shield is used.

[0067] See Figure 1 The process flow shown in the diagram includes the following functional units in sequence. Each unit is specially configured to collaboratively implement the method described in Example 1 and to adapt to the unique structure of the special sprout packaging box. The system includes: The pretreatment unit is configured as a treatment chamber that can precisely control the gas composition and pressure to implement pretreatment processes, such as providing a CO2 gas environment with a volume concentration of 15% to 25% for 3 to 5 minutes, or providing a vacuum environment with an absolute pressure of -0.03 MPa to -0.02 MPa for 2 to 4 minutes, to induce the closure of stomata in young shoots.

[0068] The adhesive protection unit integrates: Solution preparation and supply module: used to prepare and deliver a mixed aqueous solution of sodium alginate and hydroxypropyl methylcellulose (HPMC) with a mass concentration of 0.5% to 1.5% and 0.2% to 1.0% by mass, as well as a crosslinked solution of calcium chloride (CaCl2) with a mass concentration of 1% to 2%.

[0069] High-pressure spray module: Equipped with a high-pressure nozzle with a spray particle size of 30 micrometers to 50 micrometers to ensure that the mixed solution evenly covers the surface of the tender shoots.

[0070] Crosslinking soaking tank: used to soak the sprayed buds in calcium chloride solution for 1 to 3 minutes to form the calcium alginate-hydroxypropyl methylcellulose composite protective film.

[0071] A dedicated packaging unit, specifically adapted to the sprout packaging box with a composite wall layer structure and built-in modified atmosphere microcapsules as described in Example 1, includes: Packaging box feeding and positioning conveyor line: used to accurately feed and position the special packaging boxes, ensuring that their built-in functional structures (such as selectively breathable membrane windows and humidity regulating layers) are in the predetermined positions in subsequent processes.

[0072] Flexible adaptive filling mechanism: This mechanism matches the anti-sticking protrusions 8 structure on the inner wall of the packaging box and the size of the box. It uses a gentle clamping or pneumatic spreading method to fill the tender shoots of water shield after the protective coating into the box, and precisely controls the filling volume to occupy 65% ​​to 70% of the box's internal volume, so as to avoid damaging the protective coating film on the surface of the tender shoots and the functional layer inside the box.

[0073] Low-temperature rapid heat sealing machine: Its heat sealing temperature, pressure and time parameters are optimized and it is specially used to seal the box body 1 and box cover 2 of the composite wall layer structure. While ensuring the sealing strength, it prevents heat conduction from causing thermal effects on the tender buds and humidity-responsive modified atmosphere microcapsules already put in the box.

[0074] A gradient sterilization unit, specifically configured to implement the aforementioned "short-time thermal sterilization-ultra-high-pressure cold sterilization" gradient sterilization process, includes: Short-time heat sterilization station: A precise temperature-controlled water bath is used, with the temperature set at 85℃~88℃ and the processing time at 8 seconds~12 seconds. This short-time treatment aims to initially kill microorganisms on the surface and shallow layer of the packaging box and create conditions for subsequent ultra-high pressure sterilization.

[0075] Ultra-high pressure cold sterilization station: Using ultra-high pressure processing equipment, the pressure is set to 320 MPa~340 MPa and the processing time is 25 seconds~35 seconds. This station immediately performs high-intensity non-thermal sterilization on the packaging box after heat sterilization to ensure that microorganisms are completely inactivated, while maximizing the preservation of the tender texture and the activity of the built-in microcapsules.

[0076] The two workstations are directly connected by a seamless robotic arm or high-speed conveyor belt, ensuring that the packaging boxes are continuously and rapidly transferred during the sterilization process, achieving a gradient sterilization effect of "heat-pressure" synergy.

[0077] A cold storage unit is a cold storage warehouse or cold chain transportation system in which the temperature can be stably maintained within the range of 0℃ to 4℃. It is used to receive and store packaging boxes that have undergone gradient sterilization treatment in order to achieve long-term preservation.

[0078] An integrated control system that integrates the aforementioned units and possesses the following coordinated control functions: Sequence and Interlock Control: The operation of each unit is controlled in the process flow of "pretreatment - adhesive protection - packaging - gradient sterilization - refrigeration". Interlocks are set between the gradient sterilization unit and the packaging unit. When any sterilization station is abnormal, the upstream packaging process is automatically suspended to prevent products that have not completed the complete sterilization process from flowing downstream.

[0079] Material dynamic balance: Based on the real-time processing volume of the pretreatment unit, the preparation and supply rate of the solution in the adhesive treatment unit are dynamically adjusted to achieve process material balance.

[0080] Process parameter coordination and adaptation: The system stores and calls up filling parameters, heat sealing parameters and sterilization parameters that match the special packaging box structure and gradient sterilization process, ensuring that the overall operation of the system is highly coordinated with the specific packaging method of the present invention.

[0081] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention.

[0082] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.

[0083] Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The reference to "embodiment" herein means that a specific feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily indicate the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0084] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for preserving and packaging of water shield sprouts, characterized by, The application relates to a fresh-keeping packaging method and device for water shield sprouts. The method comprises the following steps: pretreating the collected fresh water shield sprouts to induce stomata closure of the water shield sprouts; uniformly spraying a mixed aqueous solution containing 0.5-1.5% sodium alginate and 0.2-1.0% hydroxypropyl methyl cellulose on the surface of the water shield sprouts, and then immersing the sprayed water shield sprouts in a 1-2% calcium chloride solution for 1-3 minutes to form a calcium alginate-hydroxypropyl methyl cellulose composite protective film on the surface of the sprouts; packing and sealing the water shield sprouts after the protective film forming; wherein the volume of the water shield sprouts in the packing box is controlled to be 65-70% of the internal volume of the packing box; sequentially performing water bath sterilization at 85-88 DEG C for 8-12 seconds and high-pressure sterilization at 320-340 MPa for 25-35 seconds on the sealed packing box; and storing the sterilized packing box in a 0-4 DEG C environment to realize fresh-keeping packaging of the water shield sprouts. The pretreatment of the water shield sprouts comprises the following steps: treating the water shield sprouts with 15-25% CO2 gas for 3-5 minutes, or treating the water shield sprouts in a vacuum environment with an absolute pressure of -0.03 MPa to -0.02 MPa for 2-4 minutes. The packing box comprises the following parts: a box body (1) with a hollow cavity with an open top, and a wall part from outside to inside comprising an outer oxygen barrier film (5), a middle functional layer (6) and an inner antibacterial film (7); a box cover (2) sealingly connected to the top of the box body (1) to form a packaging unit; a selective gas permeation window (3) provided on the side wall of the box body (1), wherein the selective gas permeation window (3) is a high-molecular polymer film with a CO2 permeation rate higher than an O2 permeation rate, and is used for regulating the escape and exchange of O2 and CO2 in the packaging; a humidity adjusting layer (4) attached to the inner side wall of the box body (1), wherein the humidity adjusting layer (4) is made of sodium carboxymethyl cellulose; a plurality of convex points (8) uniformly distributed on the inner wall of the inner antibacterial film (7), wherein the convex points (8) and the inner antibacterial film (7) are integrally formed; and a modified atmosphere microcapsule release unit (9) integrated in the middle functional layer (6), wherein the wall material of the modified atmosphere microcapsule release unit (9) is a humidity-responsive polymer material, and the inside of the modified atmosphere microcapsule release unit (9) is wrapped with a citric acid-sodium bicarbonate reactant; when the humidity in the box body (1) reaches 85-95%, the wall material of the modified atmosphere microcapsule release unit (9) swells and ruptures, and the reactant releases carbon dioxide gas; wherein the carbon dioxide gas released by the modified atmosphere microcapsule release unit (9) and the selective gas permeation window (3) together form a self-adaptive modified atmosphere system: when the carbon dioxide concentration in the box increases due to the release, the selective gas permeation window (3) preferentially permeates carbon dioxide to maintain a suitable gas ratio, and simultaneously inhibits the entry of oxygen, thereby synergistically inhibiting the respiration of the water shield sprouts and prolonging the shelf life. ​ ​ 2. The method for preserving water shield sprout according to claim 1, wherein ​ ​ 3. The method for preserving water shield sprout according to claim 1, wherein ​ ​ ​ ​ ​ ​ ​ ​ 4. The method for preserving water shield sprout according to claim 3, wherein The humidity adjusting layer (4) is made of sodium carboxymethyl cellulose (CMC) material, and has a thickness of 0.4-0.6 mm.

5. The method for preserving water shield sprout according to claim 3, wherein The outer oxygen barrier film (5) is a blended biodegradable film of polylactic acid and starch, wherein the mass content of starch is 28% to 32%, the thickness of the outer oxygen barrier film (5) is 0.03 mm to 0.08 mm, and the oxygen transmission rate thereof is ~ .

6. The method for preserving water shield sprout according to claim 3, wherein The gas adjusting microcapsule releasing unit (9) has a particle size of 40-60 microns, and a distribution density of 1800-2200 particles per cubic centimeter in the intermediate functional interlayer (6).

7. The method for preserving water shield sprout according to claim 3, wherein The inner bacteriostatic film (7) is made of konjac glucomannan and chitosan, is a water-soluble film, has a thickness of 0.02mm-0.03mm, and has a plurality of Polylysine sustained-release microparticles, the The daily release amount of polylysine is 0.08mg / cm2-0.12mg / cm2.

8. The method for preserving water shield sprout according to claim 3, wherein The convex points (8) are hemispherical, have a texture height of 0.2-0.3 mm, and a spacing of 0.8-1.2 mm between adjacent convex points (8).

9. The method for preserving water shield sprout according to claim 1, wherein In the adhesive protection process, the mixed solution of sodium alginate and hydroxypropyl methyl cellulose sprayed by a high-pressure spray head has a particle size of 30-50 microns.

10. A packaging system for preserving tender shoots of water shield, characterized in that, A method for preserving and packaging Potamogeton crispus tender shoots is provided. A method for preserving and packaging Potamogeton crispus tender shoots is provided.

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