Brasenia schreberi polysaccharide multifunctional composite fresh-keeping liquid as well as preparation method and application thereof

Abstract

The invention provides a brasenia schreberi polysaccharide multifunctional composite fresh-keeping solution as well as a preparation method and application thereof, and belongs to the technical field of fresh-keeping materials, the composite fresh-keeping solution comprises the following components in percentage by mass: 1.5%-3.5% of brasenia schreberi polysaccharide, 0.5%-1.5% of chitosan, 0.4%-1% of eugenol, 0.5%-1% of a plasticizer and the balance of water. The brasenia schreberi polysaccharide is used as a core functional factor, the eugenol natural active component and the chitosan are used as a film-forming carrier, a novel composite fresh-keeping system is constructed through synergistic interaction, the fresh-keeping effect is remarkably improved, the limitation that a traditional fresh-keeping solution is designed for a single category is broken through, fruit and vegetable-meat universality is achieved, and in the fruit and vegetable fresh-keeping process, the fresh-keeping effect is good. Fruit respiration and water evaporation can be inhibited, maturity and senescence are delayed, and color, taste and nutrition are kept; in meat preservation, oxidation of lipid and protein can be inhibited. The prepared fresh-keeping liquid adopts natural active ingredients, and is greener and safer.

Description

Technical Field

[0001] This invention relates to the field of preservation materials technology, specifically to a multifunctional composite preservation liquid containing water shield polysaccharide, its preparation method, and its application. Background Technology

[0002] With the rapid rise and popularization of fresh food e-commerce platforms, cold chain logistics systems, and ready-to-eat consumption models, fruits and meat products continue to undergo complex physiological and biochemical activities after harvesting or slaughter. These activities mainly include respiration, enzymatic reactions, and microbial metabolic processes. These metabolic processes can lead to a series of quality deterioration phenomena in the products, such as moisture loss, tissue browning, spoilage, and the growth and reproduction of pathogenic microorganisms.

[0003] While traditional reliance on chemically synthesized preservatives can delay fruit and vegetable spoilage, it carries potential health risks, prompting the academic community to focus on greener, safer, and more natural preservation solutions. Among these, edible coating technology has garnered significant attention due to its ability to construct a semi-permeable "protective film" on the fruit surface, effectively inhibiting moisture evaporation, respiration climacteric, and oxidative deterioration. Chitosan, with its multiple advantages of being naturally sourced, non-toxic, edible, forming a dense film, and possessing inherent antibacterial activity, has become a star substrate for this type of coating. However, single-function chitosan coatings have limited functionality and cannot simultaneously meet the complex requirements of antibacterial, antioxidant, and anti-browning properties. Therefore, researchers are attempting to develop multifunctional composite edible films to more comprehensively lock in the nutrients of fruits and vegetables, extend shelf life, and improve sensory quality. In current market practice, single-function preservative liquid products are typically designed and developed only for a specific product category. For example, fruit preservative liquids primarily focus on maintaining product freshness and inhibiting the ripening effect of ethylene, while meat preservative liquids emphasize inhibiting microbial growth and maintaining product color. This single-function preservation liquid design leads to repeated formula development, high storage management costs, and potential risks of cross-contamination.

[0004] Therefore, developing a universal preservative liquid product that can be applied to both fruits and vegetables and meat, meeting the preservation needs of different types of fresh products while reducing production and management costs, has become an urgent problem to be solved in the field of preservation materials technology. Summary of the Invention

[0005] In view of the technical problems existing in the background art, the present invention provides a multifunctional composite preservative liquid of water shield polysaccharide, its preparation method and application, aiming to solve the technical problems of existing preservative liquids having single function, limited application range and unsatisfactory preservation effect.

[0006] In a first aspect, the present invention provides a multifunctional composite preservative liquid containing water shield polysaccharide, comprising the following components by mass percentage: 1.5%~3.5% water shield polysaccharide, 0.5%~1.5% chitosan, 0.4%~1% eugenol, 0.5%~1% plasticizer, and the balance being water.

[0007] Preferably, the water shield polysaccharide multifunctional composite preservative liquid comprises the following components by mass percentage: 2.5% water shield polysaccharide, 1.5% chitosan, 0.4% eugenol, 1% plasticizer, and the balance water; Alternatively, the following formula may be used: 3.5% water shield polysaccharide, 1.5% chitosan, 0.7% eugenol, 1% plasticizer, and the remainder water. Alternatively, the formula may contain 3.5% water shield polysaccharide, 1.5% chitosan, 0.4% eugenol, 1% plasticizer, and the remainder water.

[0008] Preferably, the plasticizer includes at least one of glycerol, sorbitol, xylitol, and trehalose.

[0009] Secondly, the present invention provides a method for preparing a multifunctional composite preservative liquid containing water shield polysaccharides, comprising the following steps: Chitosan was dispersed in water and heated to 80-90℃ until completely dissolved. After cooling to room temperature, a plasticizer was added and heated to 40-60℃ and stirred until homogeneous. After cooling to room temperature, water shield polysaccharide and eugenol were added, and the mixture was ultrasonically treated and allowed to stand to obtain a multifunctional composite preservative solution of water shield polysaccharide.

[0010] Preferably, the preparation method of water shield polysaccharide includes the following steps: NaOH solution was added to dried water shield leaf powder, and the mixture was heated and stirred for extraction. Then, concentrated hydrochloric acid was added for neutralization and the mixture was filtered. Ethanol was added to the filtrate for alcohol precipitation. After centrifugation, the precipitate was collected, dried, reconstituted, and concentrated to obtain water shield polysaccharide.

[0011] Preferably, the heating and stirring extraction temperature is 70~90℃, and the heating and stirring extraction time is 1~2h.

[0012] Preferably, the concentration of the NaOH solution is 0.1~1 mol / L, and the volume ratio of the NaOH solution to the water shield leaf powder is (30~50):1.

[0013] Thirdly, the present invention provides an application of a multifunctional composite preservative liquid containing water shield polysaccharide in the preservation of fruits and / or meat products.

[0014] In the technical solution of this invention embodiment, the water shield polysaccharide multifunctional composite preservative liquid has a wide range of applications, is suitable for common fruits, vegetables and meats, and has a good preservation effect.

[0015] Fourthly, the present invention provides a method for preserving fruit, comprising the following steps: soaking the fruit in the multifunctional composite preservative solution of water shield polysaccharide described in the first aspect for 2-5 minutes, and then removing and draining the soaked fruit.

[0016] Fifthly, the present invention provides a method for preserving meat products, comprising the following steps: soaking the meat products in the multifunctional composite preservative solution of water shield polysaccharide described in the first aspect for 2-5 minutes, and then removing and draining the soaked meat products.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a multifunctional composite preservative liquid based on water shield polysaccharides. Water shield polysaccharides serve as the core functional factor, supplemented with eugenol, a natural active ingredient, and chitosan as a film-forming carrier, synergistically constructing a novel composite preservation system. By optimizing the preparation process parameters, the uniform dispersion of each component is ensured, forming a stable composite system. The performance of the preservative liquid can be precisely controlled, allowing it to better adapt to different preservation scenarios. The water shield polysaccharide multifunctional composite preservative liquid can be applied to the surface of fruits, vegetables, and meat products through simple methods such as spraying and soaking. In fruit and vegetable preservation, it effectively inhibits fruit respiration and water evaporation, reduces microbial infection, delays fruit ripening and senescence, and maintains the fruit's color, taste, and nutritional components. In meat preservation, it inhibits lipid and protein oxidation, extending the shelf life of meat.

[0018] Compared to traditional single-function preservative liquids, the multifunctional composite preservative liquid containing water shield polysaccharides of this invention has significant advantages. It breaks through the limitations of traditional preservative liquids designed for a single product category, achieving versatility for both fruits and vegetables and meats, thus reducing R&D and production costs for enterprises. Furthermore, due to the use of natural active ingredients, this preservative liquid is greener and safer, meeting consumers' demand for healthy food. Attached Figure Description

[0019] Figure 1 This is a blank group of blueberry fruits showing changes in appearance during storage during the present invention; Figure 2 The appearance changes of blueberries treated with the compound preservative solution of Example 7 of the present invention during storage; Figure 3 The curves showing the changes in ascorbic acid content in blueberries treated with the compound preservative solution of Example 7 of this invention and the control group during storage are shown. Figure 4 The curves showing the changes in titratable acid content of blueberries treated with the compound preservative solution of Example 7 of this invention and the control group during storage are shown. Figure 5 The curves showing the changes in soluble solids content in blueberries treated with the compound preservative solution of Example 7 of this invention and the control group during storage are shown. Figure 6 The curves show the changes in soluble solids content of blueberries treated with the compound preservative solution of Example 7 of this invention and the control group during storage. Detailed Implementation

[0020] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0021] To address the technical problems of limited functionality, narrow application range, and unsatisfactory preservation effects in existing preservative solutions, this invention provides a multifunctional composite preservative solution containing water shield polysaccharides, its preparation method, and its application. Through the synergistic combination of multiple functional components, it effectively solves the technical bottlenecks of traditional single-component preservative solutions, such as limited preservation function and unstable effects, thereby significantly improving the overall performance and application value of the preservative solution.

[0022] In a first aspect, embodiments of the present invention provide a multifunctional composite preservative liquid containing water shield polysaccharides, comprising the following components by mass percentage: 1.5%~3.5% water shield polysaccharides, 0.5%~1.5% chitosan, 0.4%~1% eugenol, 0.5%~1% plasticizer, and the balance being water.

[0023] In the technical solution of this invention embodiment, chitosan possesses excellent film-forming properties, broad-spectrum antibacterial activity, and is non-toxic, harmless, and biodegradable; water shield polysaccharide has certain adhesiveness, moisturizing properties, and antioxidant and antibacterial effects; eugenol has the function of scavenging oxygen free radicals to achieve antioxidant effects; the combination of water shield polysaccharide and eugenol can enhance antioxidant and antibacterial properties. The synergistic effect of the three significantly improves the preservation effect of the water shield polysaccharide multifunctional composite preservative liquid. The membrane structure formed by chitosan provides a good carrier for other components, allowing them to be evenly distributed on the surface of the object being preserved. The adhesiveness of water shield polysaccharide helps to enhance the stability and adhesion of the membrane, prevents the membrane layer from falling off, and better exerts its moisturizing, antibacterial, and antioxidant effects. Eugenol, on the other hand, plays the function of scavenging oxygen free radicals inside the membrane structure, further inhibiting the oxidation reaction of the object being preserved.

[0024] Furthermore, in some embodiments, the water shield polysaccharide multifunctional composite preservative liquid comprises the following components by mass percentage: 2.5% water shield polysaccharide, 1.5% chitosan, 0.4% eugenol, 1% plasticizer, and the balance water; Alternatively, the following formula may be used: 3.5% water shield polysaccharide, 1.5% chitosan, 0.7% eugenol, 1% plasticizer, and the remainder water. Alternatively, the formula may contain 3.5% water shield polysaccharide, 1.5% chitosan, 0.4% eugenol, 1% plasticizer, and the remainder water.

[0025] In the technical solution of this invention, through experiments and optimization of different proportions of water shield polysaccharide multifunctional composite preservative liquid, these specific component ratios have demonstrated superior preservation performance in practical applications. In fruit and vegetable preservation, it can more effectively inhibit fruit respiration, delay the oxidation process, and better preserve taste and nutrients. In meat product preservation, it can effectively inhibit lipid and protein oxidation, thereby maintaining the quality and nutritional value of meat products.

[0026] Furthermore, in some embodiments, the plasticizer includes at least one of glycerol, sorbitol, xylitol, and trehalose.

[0027] In the technical solution of this invention embodiment, the plasticizer functions to moisturize, regulate osmotic pressure, delay moisture loss, and assist other preservative ingredients in their function. The addition of the plasticizer allows it to interact with components such as chitosan and water shield polysaccharide to form a more stable and uniform membrane structure. The plasticizer component can be conventionally selected as needed, including but not limited to glycerol listed in the embodiments of this invention. Glycerol, as a humectant and film-forming aid, reduces moisture loss by absorbing and locking in moisture, while simultaneously enhancing the membrane's flexibility and adhesion, thus improving overall stability.

[0028] Secondly, embodiments of the present invention provide a method for preparing a multifunctional composite preservative liquid containing water shield polysaccharides, comprising the following steps: Chitosan was dispersed in water and heated to 80-90℃ until completely dissolved. After cooling to room temperature, a plasticizer was added and heated to 40-60℃ and stirred until homogeneous. After cooling to room temperature, water shield polysaccharide and eugenol were added, and the mixture was ultrasonically treated and allowed to stand to obtain a multifunctional composite preservative solution of water shield polysaccharide.

[0029] In the technical solution of this invention embodiment, the preparation method of the water shield polysaccharide multifunctional composite preservative liquid is relatively simple and easy to industrialize. During the preparation process, by precisely controlling the proportions of each component and the reaction conditions, the quality stability of the preservative liquid can be ensured.

[0030] Furthermore, in some embodiments, the preparation method of water shield polysaccharide includes the following steps: NaOH solution was added to dried water shield leaf powder, and the mixture was heated and stirred for extraction. Then, concentrated hydrochloric acid was added for neutralization and the mixture was filtered. Ethanol was added to the filtrate for alcohol precipitation. After centrifugation, the precipitate was collected, dried, reconstituted, and concentrated to obtain water shield polysaccharide.

[0031] In the technical solution of this invention embodiment, the alkaline extraction method for extracting polysaccharides from water shield can improve the polysaccharide yield. The cell walls of water shield contain a large amount of cellulose, hemicellulose, and pectin. Alkaline solution (NaOH) can soften the cell walls and dissolve some of the water-insoluble acidic polysaccharides. Simultaneously, under alkaline conditions, the hydroxyl and carboxyl groups of the polysaccharides ionize, enhancing water solubility and increasing extraction efficiency. Furthermore, the alkaline extraction method maintains the structural stability of the polysaccharides, preserving their biological activity.

[0032] Furthermore, in some embodiments, the heating and stirring extraction temperature is 70~90°C, and the heating and stirring extraction time is 1~2 hours.

[0033] In the technical solution of this invention embodiment, by controlling the temperature and time of heating and stirring extraction, the polysaccharide components in water shield can be more fully dissolved into the solution, thereby improving the polysaccharide extraction rate.

[0034] Furthermore, in some embodiments, the concentration of the NaOH solution is 0.1~1 mol / L, and the volume ratio of the NaOH solution to the water shield leaf powder is (30~50):1.

[0035] In the technical solution of this invention, a suitable NaOH solution concentration can effectively destroy the cell structure of water shield leaves, allowing polysaccharide components to be released, while a reasonable volume ratio ensures sufficient contact and reaction of various substances during the extraction process.

[0036] Thirdly, embodiments of the present invention provide an application of a multifunctional composite preservative liquid containing water shield polysaccharide in the preservation of fruits and / or meat products.

[0037] In the technical solution of this invention embodiment, the water shield polysaccharide multifunctional composite preservative liquid has a wide range of applications, is suitable for common fruits, vegetables and meats, and has a good preservation effect.

[0038] Fourthly, embodiments of the present invention provide a method for preserving fruit, comprising the following steps: soaking the fruit in the multifunctional composite preservative solution of water shield polysaccharide described in the first aspect for 2-5 minutes, and then removing and draining the soaked fruit.

[0039] Fifthly, embodiments of the present invention provide a method for preserving meat products, comprising the following steps: immersing the meat products in the multifunctional composite preservative solution of water shield polysaccharide described in the first aspect for 2-5 minutes, and then removing and draining the soaked meat products.

[0040] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0041] In the following embodiments of the present invention, the specific steps of the extraction method of water shield polysaccharides are as follows: Wash fresh water shield, dry the leaves at 40℃, grind them into powder, take the water shield powder, add 40 times the volume of 0.3mol / L NaOH solution, heat and stir at 70℃ for 2 hours, then add concentrated hydrochloric acid for neutralization, filter and collect the filtrate, add 3 times the volume of 95% ethanol to the filtrate and precipitate overnight; the next day, centrifuge at 4500 r / d for 15 min to collect the precipitate and remove the ethanol; finally, dry with hot air at 50℃ to remove residual ethanol, redissolve in distilled water, concentrate the redissolved product to obtain water shield polysaccharide.

[0042] Example 1 A multifunctional composite preservative liquid containing water shield polysaccharides comprises, by weight percentage: 1.5% water shield polysaccharide, 1.5% chitosan, 1% eugenol, 1% glycerol, and the balance being water.

[0043] The specific steps for preparing the water shield polysaccharide multifunctional composite preservative liquid are as follows: According to the target mass percentage, chitosan was dispersed in water and heated at 80°C for 1 hour until completely dissolved. After the temperature dropped to room temperature, glycerol was added as a plasticizer. The mixture was stirred at 50°C for 1 hour and then cooled to room temperature. Water shield polysaccharide and eugenol were then added. After sonication for 30 minutes, the mixture was allowed to stand to obtain the water shield polysaccharide multifunctional composite preservative liquid.

[0044] Example 2 A multifunctional composite preservative liquid containing water shield polysaccharides comprises, by weight percentage: 2.5% water shield polysaccharides, 0.5% chitosan, 0.7% eugenol, 1% glycerol, and the balance being water.

[0045] The preparation method of the water shield polysaccharide multifunctional composite preservative liquid is the same as that in Example 1.

[0046] Example 3 A multifunctional composite preservative liquid containing water shield polysaccharides comprises, by weight percentage: 2.5% water shield polysaccharides, 1.5% chitosan, 0.4% eugenol, 1% glycerol, and the balance being water.

[0047] The preparation method of the water shield polysaccharide multifunctional composite preservative liquid is the same as that in Example 1.

[0048] Example 4 A multifunctional composite preservative liquid containing water shield polysaccharides comprises, by weight percentage: 3.5% water shield polysaccharides, 0.5% chitosan, 1% eugenol, 1% glycerol, and the balance being water.

[0049] The preparation method of the water shield polysaccharide multifunctional composite preservative liquid is the same as that in Example 1.

[0050] Example 5 A multifunctional composite preservative liquid containing water shield polysaccharides comprises, by weight percentage: 3.5% water shield polysaccharides, 1% chitosan, 0.4% eugenol, 1% glycerol, and the balance being water.

[0051] The preparation method of the water shield polysaccharide multifunctional composite preservative liquid is the same as that in Example 1.

[0052] Example 6 A multifunctional composite preservative liquid containing water shield polysaccharides comprises, by weight percentage: 3.5% water shield polysaccharides, 1.5% chitosan, 0.7% eugenol, 1% glycerol, and the balance being water.

[0053] The preparation method of the water shield polysaccharide multifunctional composite preservative liquid is the same as that in Example 1.

[0054] Example 7 A multifunctional composite preservative liquid containing water shield polysaccharides comprises, by weight percentage: 3.5% water shield polysaccharides, 1.5% chitosan, 0.4% eugenol, 1% glycerol, and the balance being water.

[0055] The preparation method of the water shield polysaccharide multifunctional composite preservative liquid is the same as that in Example 1.

[0056] Comparative Example 1 This comparative example provides a composite preservative solution comprising, by mass percentage: 1.5% chitosan, 3.9% eugenol, 1% glycerol, and the balance being water.

[0057] The preparation method of the composite preservative liquid is the same as that in Example 7.

[0058] Comparative Example 2 This comparative example provides a composite preservative solution comprising, by mass percentage: 3.9% water shield polysaccharide, 1.5% chitosan, 1% glycerol, and the balance water.

[0059] The preparation method of the composite preservative liquid is the same as that in Example 7.

[0060] Comparative Example 3 This comparative example provides a composite preservative solution comprising, by mass percentage: 4.5% water shield polysaccharide, 1.5% chitosan, 0.4% eugenol, 1% glycerol, and the balance being water.

[0061] The preparation method of the composite preservative liquid is the same as that in Example 7.

[0062] Comparative Example 4 The difference between this comparative example and Example 7 is that the water shield polysaccharide is replaced with sodium alginate.

[0063] Test Example 1 Blueberries with similar surface color and firmness were selected and randomly divided into the required number of groups for the preservation experiment. Each group was immersed in the required preservation solution for 2 minutes. Afterward, the blueberries were removed, drained, and air-dried at room temperature before being placed in PET boxes and stored at room temperature. The preservation effect was then measured and analyzed. The spoilage rate and weight loss rate of each group after ten days of storage were statistically analyzed. The calculation methods for each indicator are as follows: (1) Rot rate Following the method described in the literature (Adaptability analysis of strawberry fruit decay index prediction model based on variety and harvest period [J]. Food Science, 2021, 33(20): 294-298), blueberries were classified into four decay grades according to the degree of decay. The formula for calculating the decay rate is as follows: .

[0064] (2) Weight loss rate The weight loss rate of blueberries was determined using a gravity method, with the initial mass of blueberries in each group serving as the baseline. The formula for calculating the weight loss rate is as follows: ; In the formula, W1: initial weight of fruit, g; W2: weight of fruit after storage, g.

[0065] Because the values ​​for weight loss rate and decay rate differed significantly, standardization and weight allocation were used to process the comprehensive evaluation to ensure its accuracy. A higher score indicates a lower weight loss rate and decay rate. The test results for each embodiment and comparative example are shown in Table 1 below.

[0066] Table 1

[0067] As shown in Table 1, the untreated blueberries in the control group exhibited vigorous water evaporation, microbial activity, and respiration under natural conditions, leading to easy rotting and significant weight loss. In contrast, the multifunctional composite preservative solution containing water shield polysaccharides prepared in this invention has a better preservation effect on blueberries, reducing water loss and effectively inhibiting respiration, water evaporation, and the growth of mold and bacteria, thereby delaying blueberry senescence. Example 7 showed the best preservation effect. The ratio of these three components significantly affects the preservation effect. If the concentration of water shield polysaccharide is too low, it cannot form a complete and dense preservative film, resulting in an unsatisfactory preservation effect. If the concentration is too high, it will lead to hypoxia in the internal microenvironment, causing the blueberries to rot quickly. If the concentration of eugenol is too low, its antibacterial ability is insufficient, and it cannot effectively inhibit microbial activity and water evaporation. If the concentration of eugenol is too high, it will dissolve the waxy layer on the surface of the blueberry, causing the blueberries to lose water rapidly, increasing the weight loss rate, and also accelerating the peroxidation of membrane lipids, leading to the rapid rotting of blueberries. Chitosan coating can significantly inhibit the loss of water in blueberries. However, if the concentration of chitosan is too high, it will make the viscosity of the preservative solution too high, which will reduce the preservation efficiency.

[0068] Comparative Examples 2 and 3 show that the combination of eugenol and water shield polysaccharide can achieve a better preservation effect.

[0069] Comparative Example 4 shows that replacing water shield polysaccharide with sodium alginate significantly increased the weight loss and decay rate of blueberries. Compared with sodium alginate, the combination of eugenol, chitosan and water shield polysaccharide has a better preservation effect, indicating that the system of water shield polysaccharide, eugenol and chitosan has uniqueness.

[0070] Changes in the appearance of blueberries in the control group during storage, such as Figure 1 As shown; the appearance changes of blueberries treated with the compound preservative solution described in Example 7 during storage are as follows. Figure 2 As shown in the diagram, in the control group, a small number of blueberries began to show slight skin wrinkling on the third day of storage; in the middle stage, most of the fruit skins began to lose their luster significantly, with a few showing localized dents; in the later stage, most of the fruit showed obvious wrinkling, and a few showed signs of mold. In the preservation group treated with the compound preservative solution described in Example 7, the blueberries maintained their plump state at harvest for the first four days; in the middle stage, a few fruits showed slight skin changes; and in the later stage, most blueberries showed slight wrinkling. This indicates that the compound preservative solution has a certain impact on the appearance changes of blueberries during storage. Although it cannot completely prevent appearance changes, it can slow down the rate of change, thereby extending the shelf life of blueberries.

[0071] Test Example 2 Blueberries with roughly the same surface color and firmness were selected and randomly divided into two groups. The control group received no treatment, while the experimental group was soaked in the composite preservative solution prepared in Example 7 for 2 minutes. The blueberries were then removed, drained, and air-dried at room temperature before being stored in PET boxes at room temperature. The nutritional components of the blueberries in both groups were then measured and analyzed. The specific testing methods are as follows: (1) Ascorbic acid content The 2,6-dichlorophenolindophenol method was used for determination: Weigh 5g of blueberries, place them in a mortar, add 5mL of 2% oxalic acid, grind thoroughly, filter, and collect the filtrate (the gauze can be washed several times with a small amount of 2% oxalic acid solution, and the filtrates can be combined). Adjust the total volume of the filtrate to 25mL with 2% oxalic acid solution. Accurately pipette 1.0mL of standard ascorbic acid solution into a 100mL Erlenmeyer flask, add 9mL of 1% oxalic acid solution, and titrate with 2,6-dichlorophenolindophenol solution until a pale pink color appears, and the titration endpoint should remain unchanged for 15 seconds. Record the volume of 2,6-dichlorophenolindophenol consumed. Accurately pipette two 5mL portions of the filtrate into two separate 100mL Erlenmeyer flasks, and titrate with 2,6-dichlorophenolindophenol until the pale pink color persists. Simultaneously, add 10mL of oxalic acid solution to the Erlenmeyer flask and titrate to the endpoint using the same method, as a blank control.

[0072] The formula for calculating vitamin C content is as follows: ; In the formula, X: the content of reduced ascorbic acid in the sample, mg / 100g; V: the volume of dye consumed by the sample solution during titration, mL; V0: the volume of dye consumed during blank titration, mL; p: the amount of ascorbic acid equivalent to 1 mL of dye solution obtained by standardizing the dye solution with standard reduced ascorbic acid solution, mg / mL; m: the mass of the sample contained in the filtrate taken during titration, g.

[0073] (2) Titratable acid content The acid-base titration method was used for determination: Weigh 5g of sample, add 25mL of deionized water, grind completely, filter, and dilute the filtrate to 50mL. Take 10mL of the filtrate into a 100mL Erlenmeyer flask, add 3-4 drops of phenolphthalein indicator, and titrate with 0.1mol / L NaOH (standardized with potassium hydrogen phthalate) until a faint red color persists for 1 minute. Record the volume of sodium hydroxide solution consumed. Each sample was measured three times, and the average value was taken. Simultaneously, 10mL of deionized water was added to the Erlenmeyer flask, and titrated to the endpoint using the same method to provide a blank control. The formula for calculating the titrable acid is as follows: ; In the formula, V0: the volume of sodium hydroxide standard solution consumed by blueberries, in mL; V1: the volume of sodium hydroxide standard solution consumed by the blank group, in mL; C: the concentration of sodium hydroxide standard titration solution, in mol / L; W: sample mass, in g; F: dilution factor; K: conversion factor of the main acid.

[0074] (3) Soluble solids The soluble solids content is expressed by refractive index (%) using a handheld saccharimeter.

[0075] (4) Anthocyanins Ultraviolet spectrophotometry: Blueberries were ground and extracted with 0.1 mol / L hydrochloric acid-ethanol solution for 1 hour in the dark, followed by filtration to obtain the sample solution. The instrument was calibrated using a blank solvent (0.1 mol / L hydrochloric acid-ethanol solution). The diluted sample was placed in a cuvette, and its absorbance at 530 nm was measured. The relative anthocyanin content = measured absorbance × 10. The anthocyanin concentration at A530 of 0.1 is defined as one unit.

[0076] Figure 3 The graph shows the change in ascorbic acid content in blueberries treated with the compound preservative solution described in Example 7 and the control group during storage. Ascorbic acid content objectively reflects the nutritional value and health benefits of the fruit, and its content is positively proportional to its nutritional value. Figure 3 As shown, after ten days of storage, the ascorbic acid content in the control group decreased from 18.6 mg / 100g to 3.21 mg / 100g, while the ascorbic acid content in the preservative solution group decreased from the initial 18.6 mg / 100g to 6.1 mg / 100g. The ascorbic acid content in both groups showed an overall decreasing trend with prolonged storage time, but the rate of decrease in the ascorbic acid content of the preservative solution group was less than that of the control group. This indicates that the compound preservative solution has certain antioxidant activity and can inhibit the oxidation process of blueberries to a certain extent, thereby extending its shelf life.

[0077] Figure 4 The graph shows the change in titratable acid content of blueberries treated with the compound preservative solution described in Example 7 and the control group during storage. The organic acids in blueberries are titratable acids, which are one of the core parameters for quality evaluation and directly affect the sensory quality and market value of agricultural products. Figure 4As shown, the titratable acid content of blueberries generally decreased with prolonged storage time, with a faster rate of decrease in the early stages and a gradual slowdown in the later stages. Compared to the control group, the titratable acid degradation rate in the preservative solution group was slower. After ten days of storage, the titratable acid content in the control group decreased from 0.64% to 0.24%, while the titratable acid content in the preservative solution group decreased to 0.38%. This demonstrates that the compound preservative solution can reduce the respiration rate of blueberries and slow down the decomposition of organic acids, thereby maintaining the quality and flavor of blueberries.

[0078] Figure 5 The graphs show the changes in soluble solids content in blueberries treated with the compound preservative solution described in Example 7 and in the control group during storage. Both groups of blueberries showed a trend of first increasing and then decreasing soluble solids content during storage. This is because the amount of soluble sugar produced by the body during storage is greater than the amount of soluble solids consumed by blueberries through respiration, hence the upward trend in the early stage of storage and the reverse downward trend in the later stage. On the tenth day of storage, the soluble solids content in the control group decreased to 11.6%, and the soluble solids content in the preservative solution group decreased to 12.9%, with the control group showing a larger overall change. This indicates that the preservation treatment can effectively inhibit the respiration intensity of blueberries, helping to maintain the sugar content and taste quality of blueberries.

[0079] Figure 6 The graphs show the changes in soluble solids content in blueberries treated with the compound preservative solution described in Example 7 and in the control group during storage. The anthocyanin content in the control group decreased significantly on the fourth day, while the anthocyanin content in the preservative solution group decreased relatively more gradually. Comparing the two groups, it was found that during storage, the relative anthocyanin content in the control group decreased from 6.73 to 3.43, while the relative anthocyanin content in the preservative solution group decreased from 6.8 to 4.78. The overall decreasing trend of relative anthocyanin content in the control group was greater than that in the preservative solution group. This indicates that the compound preservative solution can effectively delay the oxidation process of blueberries, thereby extending their shelf life.

[0080] Test Example 3 Commercially available, low-sodium air-dried chicken was used as the experimental material. The chicken was cut into thin, evenly sized slices, then soaked in the compound preservative solution described in Example 7 for 2 minutes. After soaking, the slices were drained, unpackaged, and stored in a 4°C refrigerator. Various indicators were tested every other day until obvious spoilage was observed. Specific test indicators are as follows: (1) Lipid oxidation value determination: Lipid oxidation was measured using the 2-thiobarbituric acid method. The sample (5.0 g) was mixed with 15 mL of 7.5% trichloroacetic acid solution and stirred at 14,000 rpm for 1 minute using a homogenizer (JRJ300-SH). The mixture was then filtered through Whatman filter paper. 5 mL of the filtrate was mixed with 5 mL of 0.02 M 2-thiobarbituric acid reagent, boiled at 95 °C for 30 minutes, and the absorbance at 532 nm was measured using an ELISA reader. A blank control was prepared using 5 mL of distilled water and 5 mL of 2-thiobarbituric acid. The TBARS value was calculated based on the standard calibration curve prepared using 1,1,3,3-tetraethoxypropane and expressed as mg malondialdehyde (MDA) / kg sample.

[0081] (2) Protein oxidation assay: TVB-N was determined using a semi-micro distillation method, referring to Chinese standard GB5009.228-2016. 5 g of the sample was uniformly mixed in 50 mL of deionized water, then filtered. 5 mL of the filtrate was mixed with a 10 g / L MgO suspension and distilled in a distillation apparatus. During distillation, volatile alkaline nitrogen gas flowed into a 20 g / L boric acid solution containing five drops of mixed indicator. After distillation for 5 min, the boric acid absorbent was titrated with a 0.01 M hydrochloric acid standard titration solution. Distilled water controlled by an isotherm was used as a blank control. The amount of TVB-N was calculated using the equation.

[0082] The test results are shown in Table 2 below.

[0083] Table 2

[0084] Table 2 shows that the compound preservative solution exhibited a significant preservation effect in the preservation test of reduced-salt air-dried chicken. Regarding weight loss, the weight loss rate of the preserved group increased slowly throughout the test, while the weight loss rate of the control group increased rapidly over time. By the ninth day, the weight loss rate of the preserved group was only 3%, while that of the control group reached 9%. This indicates that the compound preservative solution can effectively reduce moisture loss during the preservation of reduced-salt air-dried chicken and maintain its weight stability. The difference between the preserved and control groups was even more pronounced in terms of spoilage rate. The control group showed a 20% spoilage rate on the third day, which then rapidly increased to 80% on the ninth day, while the spoilage rate of the preserved group was only 20% by the ninth day. This shows that the compound preservative solution can effectively inhibit the spoilage of reduced-salt air-dried chicken and extend its shelf life. The test results for lipid oxidation value and protein oxidation also demonstrated the advantages of the compound preservative solution. With increasing time, the lipid oxidation value and protein oxidation degree of the control group were significantly higher than those of the preserved group. On the ninth day, the lipid oxidation value of the control group reached 2.73±0.18 mg MDA / kg, and the protein oxidation value was 30.7±1.3 mg / 100g, while the lipid oxidation value of the fresh group was 1.65±0.16 mg MDA / kg, and the protein oxidation value was 16.3±0.4 mg / 100g. This indicates that the compound preservation solution can effectively inhibit the lipid and protein oxidation of the salt-reduced air-dried chicken, thereby maintaining its quality and nutritional value.

[0085] In summary, the multifunctional composite preservative liquid of water shield polysaccharide prepared by this invention not only has a good preservation effect on blueberries, but also performs well in the preservation of low-salt air-dried chicken. It can significantly reduce weight loss and spoilage rate, and inhibit lipid and protein oxidation, providing an effective solution for food preservation.

[0086] It should be noted that the present invention is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments that have the same structure and perform the same effects as the technical concept within the scope of the present invention are included within the scope of the present invention. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of the present invention, are also included within the scope of the present invention.

Claims

1. A multifunctional composite preservative liquid containing water shield polysaccharides, characterized in that, The product comprises the following components by weight percentage: 1.5% to 3.5% water shield polysaccharide, 0.5% to 1.5% chitosan, 0.4% to 1% eugenol, 0.5% to 1% plasticizer, and the balance being water.

2. The multifunctional composite preservative liquid containing water shield polysaccharides according to claim 1, characterized in that, The water shield polysaccharide multifunctional composite preservative liquid comprises the following components by mass percentage: 2.5% water shield polysaccharide, 1.5% chitosan, 0.4% eugenol, 1% plasticizer, and the balance water; Alternatively, the following formula may be used: 3.5% water shield polysaccharide, 1.5% chitosan, 0.7% eugenol, 1% plasticizer, and the remainder water. Alternatively, the formula may contain 3.5% water shield polysaccharide, 1.5% chitosan, 0.4% eugenol, 1% plasticizer, and the remainder water.

3. The multifunctional composite preservative liquid containing water shield polysaccharides according to claim 1, characterized in that, The plasticizer includes at least one of glycerol, sorbitol, xylitol, and trehalose.

4. The preparation method of the multifunctional composite preservative liquid of water shield polysaccharide as described in any one of claims 1 to 3, characterized in that, Includes the following steps: Chitosan was dispersed in water and heated to 80-90°C until completely dissolved. After cooling to room temperature, a plasticizer was added and heated to 40-60°C with stirring until homogeneous. After cooling to room temperature, water shield polysaccharide and eugenol were added, and the mixture was ultrasonically treated and allowed to stand to obtain the water shield polysaccharide multifunctional composite preservative liquid.

5. The method for preparing the multifunctional composite preservative liquid of water shield polysaccharide according to claim 4, characterized in that, The preparation method of the water shield polysaccharide includes the following steps: NaOH solution was added to dried water shield leaf powder, and the mixture was heated and stirred for extraction. Then, concentrated hydrochloric acid was added for neutralization and the mixture was filtered. Ethanol was added to the filtrate for alcohol precipitation. After centrifugation, the precipitate was collected, dried, reconstituted, and concentrated to obtain the water shield polysaccharide.

6. The method for preparing the multifunctional composite preservative liquid of water shield polysaccharide according to claim 5, characterized in that, The temperature for heating and stirring extraction is 70~90℃, and the extraction time is 1~2h.

7. The method for preparing the multifunctional composite preservative liquid of water shield polysaccharide according to claim 5, characterized in that, The concentration of the NaOH solution is 0.1~1 mol / L; the volume ratio of the NaOH solution to the water shield leaf powder is (30~50):

1.

8. The application of the multifunctional composite preservative liquid of water shield polysaccharide as described in any one of claims 1 to 3 in the preservation of fruits and / or meat products.

9. A method for preserving fruit, characterized in that, The process includes the following steps: soaking the fruit in the multifunctional composite preservative solution of water shield polysaccharide as described in any one of claims 1 to 3 for 2 to 5 minutes, and then removing and draining the soaked fruit.

10. A method for preserving meat products, characterized in that, The process includes the following steps: soaking the meat products in the multifunctional composite preservative solution of water shield polysaccharide as described in any one of claims 1 to 3 for 2 to 5 minutes, and then removing and draining the soaked meat products.

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