Portulaca oleracea composite coating preservative, preparation method and method for edible mushroom preservation

Abstract

The present application relates to a composite coating preservative of Portulaca oleracea, a preparation method and a method for preserving edible fungi, and belongs to the technical field of edible fungi coating preservation packaging. The problem that the film of Portulaca oleracea is easily affected by the environment and may be damaged in a dense structure for a long time in a high-humidity environment, thereby reducing the preservation effect, is solved. A composite coating preservative of Portulaca oleracea comprises the following components in percentage by volume: glycerol 7-9%, sodium alginate 25-35%, carrageenan 0.17-2.5%, and Portulaca oleracea reagent. The preservation requirements of Pleurotus eryngii are comprehensively considered, so that the weight loss rate and the malondialdehyde content of the Pleurotus eryngii slices can be effectively reduced, and the hardness can be improved. The present application selects natural raw material Portulaca oleracea to extract substances with strong antioxidant properties to enhance the effect of the preservation coating, and can also ensure the structural stability in a high-humidity environment, thereby improving the preservation effect.

Description

TECHNICAL FIELD

[0001] The present application relates to a composite coating film preservative, a preparation method and a method for preserving edible fungi, and belongs to the technical field of edible fungi coating film preservation packaging. BACKGROUND

[0002] In recent years, Pleurotus eryngii has attracted much attention. It can not only be eaten, but also has certain food therapy and medicinal value. One of the characteristics of Pleurotus eryngii is that the fungus is thick and nutritious, and the taste is excellent, so it is called the combination of almonds and abalone, and is also known as almond abalone mushroom, and is praised as "shiitake mushroom king". Compared with dried shiitake mushrooms, tremella and black fungus, Pleurotus eryngii has higher protein and moisture content, richer mannitol and free amino acid content, and lower fat and total sugar content, and is particularly suitable for the elderly. In addition, Pleurotus eryngii also contains rich sterols, which can lower blood lipids, cholesterol and other effects, and is listed as one of the most potential edible and medicinal fungi in the 21st century. Pleurotus eryngii has such high development and utilization value, in order to control the quality decline in post-harvest storage and transportation, its post-production physiology and biochemistry and post-harvest preservation techniques Pleurotus eryngii has thick and tender fungus, delicious taste, and excellent commodity value. On the one hand, it has high edible value, with high protein, low fat and low heat; on the other hand, it also has high medicinal value, and has certain preventive effect on viral diseases and stomach diseases. The tyrosinase contained therein can lower cholesterol and blood pressure, and the trypsin, maltase and protease contained in food can help digestion, thereby improving nutritional value. The mushroom polysaccharide and isoprotein in the fermentation extract can inhibit the occurrence and development of tumors, prevent vascular sclerosis, improve human immunity, and have many medicinal effects. At present, the research on the storage and preservation of edible fungi mainly uses low-temperature preservation, controlled atmosphere storage, irradiation preservation, coating preservation, ozone treatment and other technologies to treat edible fungi, so as to improve the storage quality of edible fungi and prolong the shelf life. With the continuous progress and innovation of edible fungus coating technology, the coating method has been applied in many different ways.

[0003] The coating film preservative prepared by Portulaca oleracea has become a common physical preservation method. By forming a thin and transparent film on the surface of edible fungi, not only can mechanical damage and pathogenic bacteria be inhibited, but also gas exchange can be effectively prevented, thereby delaying the respiration of edible fungi and physiological aging. At present, many studies have focused on the application of Portulaca oleracea composite coating film, such as adding clove extract for strawberry preservation, composite coating film of chitosan, ginger juice and garlic extract for the storage quality and preservation effect of fresh-cut lotus root, and acid-soluble chitosan combined with cinnamon essential oil for Pleurotus eryngii preservation. Researchers usually determine the best formula of Portulaca oleracea composite coating film by preservation effect, and develop Portulaca oleracea composite preservative with good biological compatibility and excellent antibacterial performance by using molecular design and chemical modification technology, which becomes an important research field of Portulaca oleracea composite coating film preservation. For example: the application of a kind of Portulaca oleracea preservative, preparation method and application, with the publication number CN107865036A, discloses a preservative with Portulaca oleracea alcohol as the main active ingredient, the composition is Portulaca oleracea alcohol extract 0.5%-5%, emulsifier 0.3%-0.5%, and the rest is water. The preservative is mainly used for fresh meat products. However, different proportions of Portulaca oleracea preservative have different functions. Among them, the application of nano-SiOx can significantly improve the preservation, water resistance, transparency and mechanical properties of Portulaca oleracea coating film; by combining sodium ethylene sulfate salt with Portulaca oleracea, the antibacterial ability of Portulaca oleracea can be significantly improved, thereby effectively improving its disease resistance; thiolated Portulaca oleracea is used to improve the preservation effect of Pleurotus eryngii. The function of Portulaca oleracea preservative with different proportions will lead to differences in its use range.

[0004] The cutting method used in the harvesting of Pleurotus eryngii may reduce the disease resistance of Pleurotus eryngii. With the progress of maturation process, the consumption of oxygen will accelerate the loss of nutrients, causing the deterioration of Pleurotus eryngii and the destruction of fruiting body tissue, thereby leading to a sharp decline in early storage quality. In order to prolong the shelf life, it is essential to evaluate the quality change of Pleurotus eryngii, so for various edible fungi, in order to maintain their commodity traits and nutritional value, appropriate preservation measures need to be taken, and the possibility of contact between edible fungi and the outside world needs to be blocked from the source. Because the Portulaca oleracea film is easily affected by the environment, long-term exposure to high humidity environment may cause damage to the dense structure of the film, thereby reducing its preservation effect.

[0005] Therefore, it is urgent to propose a Portulaca oleracea composite coating film preservative, a preparation method and a method for preserving edible fungi to solve the above technical problems. SUMMARY

[0006] The present application aims to solve the problem that the Portulaca oleracea film is easily affected by the environment, and the compact structure of the film may be damaged when being in a high humidity environment for a long time, thereby reducing the preservation effect, and provides a Portulaca oleracea composite coating preservative, a preparation method and a method for preserving edible fungi. In the following, a brief summary of the present application is given to provide a basic understanding of some aspects of the present application. It should be understood that this summary is not an exhaustive summary of the present application. It is not intended to determine the key or important parts of the present application, nor to limit the scope of the present application.

[0007] Technical scheme of the present application:

[0008] The reagent components of the Portulaca oleracea composite coating preservative are as follows in terms of volume percentage: glycerol 7%-9%, sodium alginate 25%-35%, carrageenan 0.17%-2.5%, and Portulaca oleracea reagent.

[0009] Preferably, the reagent components of the Portulaca oleracea composite coating preservative are as follows in terms of volume percentage: glycerol 8%, sodium alginate 30%, carrageenan 0.2%, and Portulaca oleracea reagent 61.8%.

[0010] The preparation method of the Portulaca oleracea composite coating preservative is used to prepare a Portulaca oleracea composite coating preservative, and comprises the following steps:

[0011] Step I: heating the Portulaca oleracea extract to a suitable temperature;

[0012] Step II: adding sodium alginate to the Portulaca oleracea extract and continuously stirring until uniform;

[0013] Step III: adding glycerol and continuously stirring until uniform;

[0014] Step IV: adding carrageenan and continuously stirring until uniform;

[0015] Step V: adjusting the pH to a suitable value.

[0016] Preferably, in Step I, the Portulaca oleracea extract is heated to 60°C, and in Step IV, acetic acid is added to adjust the pH to 3.

[0017] The method for preserving edible fungi using the Portulaca oleracea composite coating preservative comprises the following steps:

[0018] Step one: treating the edible fungi;

[0019] Step two: coating the treated edible fungi with the coating.

[0020] Preferably, Step one comprises the following steps:

[0021] Step 1.1: screening edible fungi: screening even size, consistent maturity, no mechanical damage of pleurotus eryngii;

[0022] Step 1.2: slicing: pleurotus eryngii is sliced into 5 cm in diameter and 1 cm in thickness;

[0023] Step two comprises the following steps:

[0024] Step 2.1: coating preservative: pleurotus eryngii slices are placed in the prepared spilanthes acmella coating solution (preservative) for 1 min, then taken out with tweezers and naturally dried;

[0025] Step 2.2: refrigerate for standby.

[0026] The present application has the following beneficial effects:

[0027] The present application comprehensively considers the preservation needs of pleurotus eryngii, which not only can effectively reduce the weight loss rate and malondialdehyde content of pleurotus eryngii slices, improve its hardness, but also can ensure the structural stability in high humidity environment, thereby improving its preservation effect;

[0028] The preservative coating of the present application can effectively prevent pleurotus eryngii from being contaminated by the outside world, thereby playing a role in preventing corrosion and moisture; when the appropriate amount of glycerol is used, it can not only play the role of improving water resistance, but also not cause the coating structure to be too loose, thereby achieving the best preservation effect; using appropriate amount of sodium alginate can improve the water isolation effect of the coating;

[0029] The whiteness value and sensory score of the mushroom after carrageenan coating treatment are good, and the problems of suspension and inability to drain caused by too high concentration can be avoided. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a flow chart of the edible fungus preservation method using the spilanthes acmella composite coating preservative;

[0031] Figure 2 is a comparison chart of reducing power;

[0032] Figure 3 is a comparison chart of DPPH free radical scavenging capacity;

[0033] Figure 4 is a comparison chart of hydroxyl radical scavenging capacity;

[0034] Figure 5 is the influence of solid-liquid ratio on clearance rate;

[0035] Figure 6 is the influence of time on clearance rate;

[0036] Figure 7 is the influence of temperature on clearance rate;

[0037] Figure 8 Effect of ratio of material to liquid and extraction time on removal rate;

[0038] Figure 9 Effect of ratio of material to liquid and temperature on removal rate;

[0039] Figure 10 Effect of ratio of material to liquid and time on removal rate;

[0040] Figure 11 Effect of coating treatment on weight loss rate of Pleurotus eryngii;

[0041] Figure 12 Effect of coating treatment on weight loss rate of Pleurotus eryngii;

[0042] Figure 13 Effect of glycerol usage on cell membrane permeability of Pleurotus eryngii;

[0043] Figure 14 Effect of sodium alginate addition on cell membrane permeability of Pleurotus eryngii;

[0044] Figure 15 Effect of carrageenan addition on cell membrane permeability of Pleurotus eryngii;

[0045] Figure 16 Effect of Portulaca oleracea complex coating preservative on hardness of Pleurotus eryngii;

[0046] Figure 17 Effect of Portulaca oleracea complex coating preservative on color value of Pleurotus eryngii;

[0047] Figure 18 Effect of Portulaca oleracea complex coating preservative on respiration intensity of Pleurotus eryngii;

[0048] Figure 19 Effect of Portulaca oleracea complex coating preservative on malondialdehyde content of Pleurotus eryngii;

[0049] Figure 20 Effect of Portulaca oleracea complex coating preservative on weight loss rate of Pleurotus eryngii;

[0050] Figure 21 Effect of Portulaca oleracea complex coating preservative on soluble protein content of Pleurotus eryngii;

[0051] Figure 22 Effect of Portulaca oleracea complex coating preservative on free amino acid content of Pleurotus eryngii. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be described below by specific embodiments shown in the drawings. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present application. In addition, in the following description, the description of the known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present application.

[0053] Specific embodiment one: combination Figures 1-22 In this embodiment, the purslane composite coating preservative for edible fungi is prepared by using purslane as the main raw material. The reagent components of the purslane composite coating preservative are as follows in terms of volume percentage: glycerol 7%-9%, sodium alginate 25%-35%, carrageenan 0.17%-2.5%, and the rest is purslane reagent. The purslane composite coating preservative can induce the lignification of the surface wounds of edible fungi, thereby inhibiting the invasion of pathogenic microorganisms on edible fungi. The composite coating for edible fungi can increase the antibacterial spectrum characteristics of single coating. The purslane composite coating preservative can be used as an effective supplement for low-temperature preservation and controlled atmosphere storage to obtain better preservation effect.

[0054] Specific embodiment two: combination Figures 1-22 In this embodiment, the purslane composite coating preservative for edible fungi is prepared by using purslane as the main raw material. The reagent components of the purslane composite coating preservative are as follows in terms of volume percentage: glycerol 8%, sodium alginate 30%, carrageenan 0.2%, and purslane reagent 61.8%. This parameter is the optimal parameter, which can effectively reduce the weight loss rate and malondialdehyde content of apricot mushroom slices and improve the hardness thereof. After storage at 10℃ for 10 days, the preservation effect is good, and the intact rate of apricot mushroom slices reaches 90%.

[0055] The present application is directed to the preservation characteristics of apricot mushroom and other edible fungi, and the optimization of the purslane composite preservation film-forming liquid (preservative), which includes the following steps:

[0056] Step 1: screening apricot mushrooms, which are commercially available, and selecting fruiting bodies that are uniform in size, free of pests and diseases, and stored at low temperature. Uniformly sized, mature, uniformly sliced (diameter of about 5 cm and thickness of about 1 cm) apricot mushrooms that are free of mechanical damage are prepared for use. Experimental reagents are prepared, as shown in Tables 9 and 10.

[0057] Table 9: Experimental reagents

[0058]

[0059] Table 10: Experimental instruments

[0060]

[0061] Step 2: detection:

[0062] Effect of coating treatment on weight loss rate of Pleurotus eryngii (Pleurotus eryngii slices): In order to explore the preservation effect of coating treatment on stored food, two groups of samples were set up: one group was treated with coating, and the other group was not treated as a control group; Next, the two groups of samples were stored for 10 days, and the weight loss rate was detected every day to observe the changes of the food during storage;

[0063] Effect of film-forming solution concentration on weight loss rate of Pleurotus eryngii: The concentration of the film-forming solution directly affects the performance of Pleurotus eryngii slices; Glycerol, carrageenan and sodium alginate were mixed in a ratio of 1:1:1 and the pH was adjusted to 3; On this basis, film-forming agents with concentrations of 0.1%, 0.3%, 0.5%, 0.7% and 0.9% were prepared and the samples were coated; After treatment, the samples were stored for 10 days and their changes were observed;

[0064] Effect of glycerol on film performance (cell membrane permeability): The mixture of glycerol, sodium alginate and carrageenan can significantly improve the toughness and ductility of the coating, making it more flexible and less prone to breakage; The ratio of the mixture is 10:1:1, the total concentration is 0.6%, and the pH is adjusted to 3;

[0065] Effect of sodium alginate and purslane extract ratio on film performance (cell membrane permeability): The ratio of the mixture of sodium alginate and purslane is set to 2:1, the mass ratio of glycerol is 8%, the total concentration is 0.6%, and the pH is adjusted to 3; The final mixture ratio is set to 3:1, 2:1, 1:1, 1:2 and 1:3;

[0066] Effect of carrageenan addition on film performance (cell membrane permeability): The color of the carrageenan preparation is milky white; During the coating process, the amounts of carrageenan and purslane are 1:1:1, the mass ratio of glycerol is 8%, the total concentration is 0.6%, and the pH is adjusted to 3; The amount of carrageenan used is 0%, 10%, 20%, 30%, 40% and 50% to ensure the quality and effect of the coating;

[0067] Measurement of cell membrane permeability: The relative conductivity of mushroom slices was measured using a DDS-307 conductivity meter; In the experiment, ten mushroom slices were selected from the same part, and a punch with a diameter of 1 cm was used; 40 ml of conductivity was added and recorded as P0; The second conductivity was measured after 10 minutes and recorded as P1; The beaker was heated to boiling for 10 minutes and recorded as P2;

[0068] Conductivity = (P1-P0) / (P2-P0) x 100% (1)

[0069] The higher the relative conductivity, the greater the degree of damage to the cell membrane, and the more serious the loss of Pleurotus eryngii tissue; it can also be manifested by the speed of tissue permeation; after the Pleurotus eryngii is picked, the permeability of the cell membrane will gradually increase over time, and the original organic matter and ions will diffuse more quickly to the outside of the cell, which also speeds up the speed of cell spoilage;

[0070] Determination of weight loss rate: weight loss rate = (fresh weight before storage - fresh weight after storage) / fresh weight before storage × 100% (2)

[0071] Statistical analysis: first, the experimental data were analyzed by Microsoft Excel 2003 software, and the optimal combination was analyzed by orthogonal table to find the optimal experimental process;

[0072] Step 3: Effect of coating treatment on the weight loss rate of Pleurotus eryngii: as shown in Figure 11 During the storage process, the water content of Pleurotus eryngii slices also increased with the continuous increase of the weight loss rate, which indicated that the coating of purslane could effectively prevent the evaporation of water on the surface of Pleurotus eryngii cells, thereby reducing the loss of water in the cells, making the shelf life of Pleurotus eryngii longer;

[0073] Effect of film-forming solution concentration on the weight loss rate of Pleurotus eryngii: as shown in Figure 12 When the concentration of the film-forming solution is low, it will lead to imperfect film structure and prolong the drying time; on the contrary, if the concentration is high, it will lead to reduced fluidity, thereby affecting the flow of gas and making the distribution of the film more uneven. When the total concentration of the film-forming agent of Pleurotus eryngii reaches 0.7%, it can effectively maintain the osmotic pressure balance of Pleurotus eryngii, thereby reducing its weight loss rate and achieving good moisturizing effect, which is 10.5%;

[0074] Effect of glycerol on film performance (cell membrane permeability): as shown in Figure 13 Due to the addition of glycerol, the structure of the film has changed significantly, thereby enhancing its hydrophilicity, making water vapor easily cross, and also enhancing the isolation effect of the coating, reducing the permeation of water. However, if the amount of glycerol added exceeds the normal range, it will affect the hygroscopicity of the film, therefore, the best amount of addition should be around 8%;

[0075] Effect of sodium alginate addition amount on film performance (cell membrane permeability): as shown in Figure 14As shown in the table, without adding sodium alginate, the cell membrane permeability of Pleurotus eryngii is as high as 21.7%. However, with the addition of sodium alginate, its effect on the cell membrane gradually becomes more and more obvious, and until 30% of the input, its effect on the cell membrane is reduced to 10.9%. This shows that sodium alginate can improve the water retention performance of Pleurotus eryngii by reducing its cell membrane permeability. In addition, the increase of the content of sodium alginate component will also lead to the increase of the coating thickness, which is not conducive to the combination of components. Therefore, when using Pleurotus eryngii coating, the amount of sodium alginate needs to be controlled to avoid excessive side effects, so as to achieve the best water retention effect.

[0076] The effect of the amount of carrageenan on the film performance (cell membrane permeability): as shown in the table, Figure 15 Without adding carrageenan, the cell membrane permeability of Pleurotus eryngii slices is as high as 20%. However, with the addition of carrageenan, its effect on the cell membrane gradually becomes more and more obvious, and until 40% of the input, its effect on the cell membrane is reduced to 9%. This shows that carrageenan can improve the water retention performance of Pleurotus eryngii by reducing its cell membrane permeability. In addition, the increase of the content of carrageenan will also lead to the increase of the coating thickness, which is not conducive to the combination; therefore, when using Pleurotus eryngii coating, the amount of carrageenan needs to be controlled to avoid excessive side effects, so as to achieve the best water retention effect;

[0077] The coating can effectively prevent Pleurotus eryngii from being contaminated by the outside world, thereby playing a role in preventing corrosion and moisture. If no coating treatment is performed, the weight loss rate of Pleurotus eryngii will increase significantly, eventually leading to a decrease in its quality, and even a loss of 15.65%. In order to obtain better preservation effect, the concentration of the preservative of Pleurotus eryngii must be just right to ensure its thickness and quality. The experimental results show that at a concentration of 0.7%, the preservation effect of Pleurotus eryngii is the best, and the weight loss rate is also reduced. The addition of glycerol in the coating of spilanthes acmella improves the function of blocking water and makes the film more soft, thereby reducing the water resistance. It is found through research that when the amount of glycerol used is 8%, it can not only improve the water resistance, but also not cause the coating structure to be too loose, thereby achieving the best preservation effect. It is recommended to adjust the concentration of carrageenan to 0.2% for preparation, which can ensure that the whiteness value and sensory score of Pleurotus eryngii after carrageenan coating treatment are good, and at the same time, can avoid the problems of suspension and inability to drain caused by too high concentration. It can be seen from the experimental results that the coating treatment of 0.2% carrageenan has the best preservation effect on Pleurotus eryngii, so it is also recommended to use this concentration for preparation. The use of appropriate amount of sodium alginate can improve the water resistance of the coating, but when the amount is too much, it not only cannot further improve the insulation effect, but also has the opposite effect, reducing the effect of the coating. The present application selects the strong antioxidant substances extracted from the natural raw material spilanthes acmella to enhance the preservation effect of the coating, and also ensures the structural stability in a high humidity environment, thereby improving the preservation effect.

[0078] Specific implementation method three: Combining Figures 1-22 This embodiment describes a method for preparing a purslane composite coating preservative, which includes the following steps:

[0079] Step 1: Heat the purslane extract to a suitable temperature;

[0080] Step II: Add sodium alginate to the purslane reagent, keep the temperature constant and stir continuously until homogeneous, for about 60 seconds;

[0081] Step 3: Add glycerin, maintain a constant temperature and stir continuously until well mixed, about 60 seconds;

[0082] Step IV: Add carrageenan, and stir continuously at a constant temperature for about 60 seconds until homogeneous.

[0083] Step V: Adjust the pH to a suitable value and refrigerate for later use;

[0084] The optimization method for purslane reagent includes the following steps:

[0085] Step i: Select 500 g of purslane and prepare the experimental reagents as shown in Table 1;

[0086] Table 1. Reagents for Purslane Extraction Experiment

[0087]

[0088] Step ii: The reducing power, DPPH free radical scavenging ability, and hydroxyl free radical scavenging ability of the anhydrous ethanol extract and the water extract were determined respectively, and the extraction method was selected by comprehensive consideration. Through optimization of extraction conditions, it was found that the water extract was stronger than the anhydrous ethanol extract after the reducing power and DPPH content determination. Therefore, water extraction was selected.

[0089] Determination of reducing power: First, the extract of purslane (purslane reagent) 1 mL in a test tube, add 2.5 mL of 0.2 mol / L phosphate buffer and 1% K3Fe6, mixed evenly to form a mixture; the mixture is placed in a constant temperature water bath at 55°C, heated to 20 min, then quickly cooled, and then add 10% trichloroacetic acid, centrifuged at 3000 r / min for 10 min; the supernatant 2.5 mL with distilled water and 0.1% FeCl3 solution were mixed, and then placed for 10 min; finally, the absorbance was measured at a wavelength of 700 nm, using the corresponding extract as a reference, see "Anti-tumor effect of water-soluble polysaccharides from yellow peach and free radical scavenging and immune activity" Chen Liuyong, Meng Xianjun, Jia Wei, et al. [J]. Food Science, 2004, according to the formula, the reducing power = absorbance of the extract sample - absorbance of the control group, according to Figure 2 It can be seen that the reducing power of the water extract is significantly greater than that of the anhydrous ethanol extract when the concentration is between 0 and 4;

[0090] Determination of DPPH free radical scavenging capacity: the corresponding DPPH concentration and reaction time of each sample can be calculated: 4 mL of prepared DPPH solution, 1 mL of purslane extract, 4 mL of 95% ethanol, and the final DPPH concentration is 0.0792 mol / mL; at a wavelength of 517 nm, the sample absorbance As minus the control liquid absorbance A8, the formula clearance rate, see "Determination of the ability of grape seed proanthocyanidin to scavenge free radicals by DPPH method" Li Chunyang, Xu Shiying, Wang Zhaon. [J]. Journal of Food and Biotechnology, 2006, 25:25-27: clearance rate (%) = (A C -A S ) / A C × %100;

[0091] Hydroxyl radical scavenging capacity: as shown in Figure 4 , with the increase of the concentration of purslane extract, its hydroxyl radical scavenging capacity also increases accordingly, see "Extraction of purslane polysaccharide and its activity in scavenging hydroxyl radicals" Zhu Xiaohua, Wu Xiangyang, Yang Luqing, Fan Qunyan, Mao Guanghua. [J]. Journal of Jiangsu University (Medical Edition), 2007, (01); at a concentration of 11 mg / mL, the hydroxyl radical scavenging rate of water extract reached 77.46%, while at the same concentration, the hydroxyl radical scavenging rate of anhydrous ethanol extract reached 39.53%; through research, it is found that compared with anhydrous ethanol, water extract has better hydroxyl radical scavenging capacity, and purslane polysaccharide also has the ability to scavenge hydroxyl radicals; in summary, water extract is adopted;

[0092] Step III: Experimental method: First, set the initial factors, liquid ratio 30:1, time 15 min, temperature 24℃, change any factor, the other two factors remain unchanged, and evaluate the effect of each factor on the results with DPPH clearance rate as the index;

[0093] That is, under the conditions of liquid ratio water to purslane extract 10:1, 20:1, 30:1, 40:1, 50:1, determine the optimal liquid ratio; under the conditions of time 50 min, 60 min, 70 min, 80 min, 90 min, determine the optimal time; under the conditions of temperature 60℃, 70℃, 80℃, 90℃, 100℃, determine the optimal temperature;

[0094] Second, Response surface methodology (RSM) is a commonly used optimization experiment method, which is a test design method based on mathematical model, through collecting experimental data and analysis, to help analyze the functional relationship between experimental variables and response variables, and determine the optimal experimental parameter configuration, as shown in Table 2:

[0095] Table 2 Design of response surface method experiment

[0096]

[0097] Step IV: Experimental results (single factor experiment results); the optimal extraction conditions: liquid ratio 29.2:1, temperature 74.6℃, time 66.5min; the best clearance rate is 32.21%; the relative deviation is 2.9%, indicating that the optimal extraction conditions are obtained;

[0098] The effect of liquid ratio on clearance rate: as shown in Figure 5 , the clearance rate increases with the increase of liquid ratio, and reaches the maximum value of 80.17% when the liquid ratio is 30:1, which is 6.62 percentage points higher than the minimum value of 73.55%, and increases by 43.68%, indicating that the compounds in purslane water extract are mainly converted from bound state to free state; as shown in Table 3, when the liquid ratio is 30:1 and 40:1 (P>0.05), the clearance rate is 32.17%, reaching the maximum; when the liquid ratio is 30:1~40:1, the conversion effect of purslane water extract compounds will decrease with the increase of liquid ratio;

[0099] Table 3 Effect of liquid ratio on clearance rate

[0100]

[0101] Effect of time on clearance rate: Figure 6It can be seen that when the time is 50 min~80 min, the clearance rate gradually increases with time, and the maximum value is 81.99% at 80 min, which is 13.06 percentage points higher than the minimum value of 68.93%, an increase of 85.95%, and then the clearance rate slowly decreases with time, indicating that the concentration ratio is appropriate; Table 4 shows that when the time is 50 min, the pH value reaches the minimum value of 4.66, and when the time is 70 min-80 min, the pH is the lowest and the clearance rate is the highest; The results show that the time is 70 min;

[0102] Table 4 Effect of time on clearance rate

[0103]

[0104] Effect of temperature on clearance rate: According to Figure 7 It can be seen that the effect of temperature on the clearance rate has certain regularity; when the temperature is between 60℃ and 70℃, the clearance rate increases with the increase of temperature, and reaches the highest peak at 70℃, about 83.55%; compared with the minimum value of 70.44%, the value increases by 13.11 percentage points, an increase of 78.55%; this shows that when the temperature is low, the clearance rate increases; but when the temperature exceeds 70℃, the clearance rate will decrease with the increase of temperature; therefore, the results show that the suitable temperature is 80℃;

[0105] Table 5 Effect of temperature on clearance rate

[0106]

[0107] Step V: Response surface test design results: The results of the test are analyzed by Design Expert 8.0 software, and the results are shown in Table 8;

[0108] Table 6 Response surface analysis factor and level table

[0109]

[0110] Table 7 Response surface test results

[0111]

[0112] Table 8 Regression analysis table

[0113]

[0114] Note: * is significant (P<0.05), ** is extremely significant (P<0.01)

[0115] Y=81.46+1.77X1+1.35X2–0.26X3–4.90X1 2-3.55X2 2 –6.78X3 2 As shown in Table 8, based on the principle of the F-test in regression analysis, the probability P-value can be used to determine the significance of a variable on the response value (clearance rate) in the experiment. The smaller the P-value, the higher the significance of the corresponding variable. In this experiment, the model's P-value is small, therefore it has high significance because P<0.0001. Furthermore, the lack-of-fit term of the model is not significant. The Radj2 value is 90.87%, indicating that the model can explain approximately 90.87% of the clearance rate variation. The experimental results are not significantly different from the model calculation results. Additionally, the P-value of X1 is less than 0.05, indicating that among the three factors, the feed-to-liquid ratio has the most significant impact on the clearance rate.

[0116] Depend on Figures 8-10 As shown, the selected range can produce the optimal response value (clearance rate), indicating that the experiment is reasonable and reflects the trend of the influence of the three factors on the response value. The extreme value condition at the center of the contour line can make the first-order partial derivative of the regression equation zero, thus ensuring the optimal point of the surface. Therefore, the phase code values ​​of the three factors can be obtained based on this condition. Based on the code value conversion, after experimental comparison, the optimal extraction conditions were determined to be: material-liquid ratio 29:2:1, temperature 74.6℃, and time 66.5 min. Optimization of the film-forming solution: by measuring the content of sodium alginate, glycerol, and carrageenan in the purslane coating solution and analyzing the cell membrane permeability conductivity, the optimal liquid-material ratio was found to be 8% glycerol, 30% sodium alginate, and 0.2% carrageenan.

[0117] Step ⅵ: Perform one-way ANOVA on the experimental results, with a significance level of 0.05; use GraphPadPrism 6.0 and Origin 9.0 software to plot the results.

[0118] Specific implementation method four: Combination Figures 1-22 This embodiment describes the preparation method of the purslane composite coating preservative. In step I, fruiting bodies (purslane) of uniform size and free from pests and diseases are selected, i.e., purslane of uniform size and maturity are screened. The juice is extracted and filtered to prepare purslane sample solution, thereby separating and extracting purslane to obtain purslane sample solution. The purslane sample solution (purslane reagent) is stored at low temperature. The purslane reagent is heated to 60°C. In step IV, acetic acid is added to adjust the pH to 3.

[0119] Specific Implementation Method Five: Combining Figures 1-22 This embodiment describes a method for preserving edible fungi using a purslane composite coating preservative. The method includes the following steps:

[0120] Step one: Edible fungi are treated;

[0121] Step two: The treated edible fungi are coated with paint for film treatment. The method of preparing edible fungi coating greatly blocks the contact between microorganisms and Pleurotus eryngii slices, prolonging the shelf life. The best portulaca oleracea composite coating treatment effectively maintains the appearance and sensory quality of Pleurotus eryngii and effectively controls the quality during storage.

[0122] Specific embodiment six: combined Figures 1-22 This embodiment is used for the preservation method of edible fungi. Step one includes the following steps:

[0123] Step 1.1: Select edible fungi: commercially available, select uniform size, no pests and diseases of fruiting bodies (Pleurotus eryngii), select uniform size, uniform maturity, no mechanical damage of Pleurotus eryngii, and clean before use;

[0124] Step 1.2: Slicing: Pleurotus eryngii slices are uniform slices with a diameter of about 5 cm and a thickness of about 1 cm;

[0125] Step two includes the following steps:

[0126] Step 2.1: Apply preservative: place the Pleurotus eryngii slices in the prepared portulaca oleracea coating solution (preservative) and stand for 1 min, then take out with tweezers and dry naturally; The portulaca oleracea coating solution forms a thin coating on the Pleurotus eryngii slices after natural air drying, thereby reducing contact with air; inhibit respiration and prevent microbial invasion;

[0127] Step 2.2: Cold storage for standby, the cold storage temperature is below 4℃, before eating, select Pleurotus eryngii with complete appearance, uniform size, no browning, corruption and deterioration, wash the Pleurotus eryngii slices completely with clean water, and drain the water;

[0128] It also includes step three: quality detection, including physiological quality and storage quality, using table 9, table 10, Pleurotus eryngii can be subjected to step three after step 2.1 is completed;

[0129] Table 9 Experimental reagents

[0130]

[0131] Table 10 Experimental instruments

[0132]

[0133] 3.1 Determination of the effect of coating on the physiological quality of postharvest Pleurotus eryngii:

[0134] Hardness determination: The surface of Pleurotus eryngii slices was determined by TA.XT. plus texture analyzer, which was fixed on the texture analyzer operating table in advance. A cylindrical flat-end probe (P / 2) with a diameter of 2.00 mm was selected. The test point was the center point of the slice. The compression test mode was selected. The pre-test speed was 1.00 mm / s, the test and post-test speeds were 2.00 mm / s, the compression depth was 6.00 mm, the contact trigger force was 5.00 g, and the force-time relationship curve image was automatically generated. The highest peak of the image was used as the hardness index. The results were expressed as mean ± standard deviation. The effect of the composite coating preservative on the hardness of Pleurotus eryngii is shown in Figure 16 As shown in Fig. 2, after the degradation of polysaccharides and proteins, the fruiting bodies of Pleurotus eryngii became soft and the water content was greatly reduced. The Pleurotus eryngii slices showed wrinkles, which affected their hardness. The hardness of the Pleurotus eryngii treated by coating decreased more slowly than that of the untreated Pleurotus eryngii. On the 6th day, the hardness of the treated Pleurotus eryngii increased by 17% compared with that of the untreated Pleurotus eryngii.

[0135] Color value determination: The color value of Pleurotus eryngii slices was measured by ULtraScan XE colorimeter to determine the average value. L-0 was black and L-100 was white. The larger the L value, the whiter the color and the lighter the browning degree. The effect of the composite coating preservative on the color value of Pleurotus eryngii is shown in Figure 17 As shown in Fig. 3, browning and wilting occurred easily during storage, which not only affected the appearance quality, but also reduced the nutritional value and commercial value. Therefore, in order to maintain the quality of Pleurotus eryngii, some measures can be taken. It was found that the whiteness value of Pleurotus eryngii decreased during storage. The control group browning faster in the later stage, while the coating treatment group did not change significantly in the early stage. Therefore, the use of composite preservative coating treatment can delay the decrease of whiteness value, which is beneficial to maintain the quality of Pleurotus eryngii.

[0136] Malondialdehyde content determination: The reaction system was 3.0% trichloroacetic acid solution, 1.0 mL 0.5% thiobarbituric acid and 1 mL extract. After uniform mixing, it was placed in a boiling water bath for 30 min. After taking out, it was quickly centrifuged at 1000 r for 10 min with tap water. The supernatant was measured at 532 nm and 600 nm wavelength to calculate the MDA content. The effect of the composite coating preservative on the respiration intensity of Pleurotus eryngii is shown in Figure 18 As shown in Fig. 4, during storage, Pleurotus eryngii could not intake enough nutrients from the culture medium, so their respiration was limited and they could not effectively utilize their own nutrients to meet the storage needs. Therefore, effective control of the respiration intensity of Pleurotus eryngii can effectively ensure their storage quality. After comparison, it was found that the use of composite coating preservative could reduce the respiration intensity of Pleurotus eryngii, which had a significant difference compared with the control group without using this method. It is beneficial to its preservation during storage.

[0137] The effect of composite coating film preservative on the content of malondialdehyde of Pleurotus eryngii is shown in Table 2. Figure 19 As shown in Table 2, the experimental results show that the content of malondialdehyde of the Pleurotus eryngii sample treated with 0.75% Portulaca oleracea coating film is lower than that of other groups on the 4th day, which indicates that the coating film can effectively inhibit the lipid oxidation rate of the cell membrane and achieve the effect of preservation; however, the content of malondialdehyde of the Pleurotus eryngii sample treated with 1.25% Portulaca oleracea coating film is higher than that of the blank group, which may be due to the fact that the concentration of the coating film treatment agent is too large, and during the natural drying process, some samples do not form completely; in this case, the cells can still perform respiration, resulting in incomplete coverage of the sample surface by the coating film, which affects the experimental results to some extent. This makes the preservation effect fail to achieve the expected purpose; one of the possible reasons is that the film does not form completely before bagging. Therefore, the coating film concentration and operation method are adjusted to ensure that the film can form fully and achieve better preservation effect;

[0138] Physiological quality of Pleurotus eryngii slices after coating: after the degradation of polysaccharides and proteins, the fruiting bodies of Pleurotus eryngii become soft and the water content is greatly reduced, the Pleurotus eryngii slices wrinkle, and then affect the hardness; the hardness of the Pleurotus eryngii treated by coating decreases more slowly than that of the untreated Pleurotus eryngii; the coating treatment using the composite preservative can delay the decrease of whiteness value, effectively reduce the content of malondialdehyde and respiration intensity, which is beneficial to maintain the quality of Pleurotus eryngii;

[0139] 3.2 Determination of the effect of coating on the storage quality of postharvest Pleurotus eryngii:

[0140] 3.21 Experimental content:

[0141] Method for determining free amino acids:

[0142] Pretreatment: weigh an appropriate amount of Pleurotus eryngii slices into a 10m centrifuge tube, add 2.5M hydrochloric acid to dissolve and make up to volume; purification: add 5mL of methanol, 5mL of water, 2.50 mL of sample solution, 1.50 mL of 0.02 M hydrochloric acid, and make up to 5.00 mL with 0.02 M hydrochloric acid after column, and filter through a 0.45μm membrane before machine;

[0143] Determination of weight loss rate: weight loss rate = (fresh weight before storage - fresh weight after storage) / fresh weight before storage x 100%;

[0144] Soluble protein content: Take an appropriate amount of frozen sample into a test tube and add 10 mL of distilled water. After ice bath slurry, centrifuge at 4 ℃ and 12000 rpm for 20 min. Collect the supernatant, which is the extract, and store it at low temperature for later use. Take 0.40 mL of the extract and determine its absorbance value at 595 nm using the same method as for plotting the quasi-curve. The soluble protein content in the sample is expressed as the mass of soluble protein contained in each gram of fresh weight (FW) of tissue, in μg / g FW. Repeat three times, and the results are expressed as mean ± standard deviation.

[0145] Soluble protein content (mg / g) = M D ×V / V S ×M(3)

[0146] 3.22 Effect of composite coating preservative on weight loss rate of king oyster mushroom: such as Figure 20 As shown in the experimental results, the weight loss rate of king oyster mushroom samples treated with purslane extract increased with prolonged storage time. However, when coated with purslane preservative solution, the water content of the king oyster mushroom samples was higher than that of untreated samples. This indicates that purslane preservative solution can provide good protection and maintain the freshness of king oyster mushrooms. The best preservation effect was achieved when using a 0.75% concentration of purslane extract.

[0147] 3.23 Effect of composite coating preservative on the soluble protein content of king oyster mushroom: such as Figure 21 As shown, soluble proteins can enhance the water-retention capacity of cells, thereby effectively protecting cellular life substances and biomembranes from the influence of the external environment. This characteristic provides essential protection for organisms to survive in extreme environments, and therefore has very important biological significance. The soluble protein content of *Pleurotus eryngii* slices treated with purslane coating solution showed an overall decreasing trend; the soluble protein content decreased rapidly in each group from 0 to 5 days, slowed down from 5 to 7 days, and the degree of decrease became consistent after 8 days; after 8 days, the difference in soluble protein content between the treatment group and the control group became insignificant (P>0.05); during 8 to 10 days, the decrease in soluble protein in the control group was lower than that in the treatment group, and the difference was significant (P<0.05). This may be due to the decrease in the synthesis of aging-related enzyme proteins caused by purslane. In summary, there were certain differences among the treatment groups during the 5-8 day storage period, but over time, the treatment groups had little effect on the soluble protein content of *Pleurotus eryngii*.

[0148] 3.24 Effect of composite coating preservative on the soluble protein content of king oyster mushroom: such as Figure 22As shown, during the long storage process, the content of soluble protein gradually decreases over time, while the content of free amino acid increases; for example, the Portulaca oleracea coated apricot mushroom slices, during the 6 d storage process, the content of free amino acid gradually increased and reached the highest point at this time, the concentration was 1.2%, then began to decline; after 10 d of storage, the total amount of free amino acid increased significantly, reaching more than 1.3%, much higher than the 1.0% of the Portulaca oleracea composite coating group, which may be due to the high permeability of apricot mushroom, a large amount of free amino acid is needed to ensure the post-ripening effect; by reducing the content of free amino acid in the mushroom, the delicious taste of apricot mushroom can be effectively maintained; the present application is designed for the ratio of edible fungi, and the characteristics of edible fungi are comprehensively considered, and data analysis is carried out through rigorous experiments, which proves that the present application can effectively reduce the weight loss rate and malondialdehyde content of apricot mushroom slices, and can improve the hardness, and has good preservation effect.

[0149] Storage quality influence: with the passage of time, the influence of each treatment group on the soluble protein content of apricot mushroom is not big. The content of soluble protein gradually decreases, and the content of free amino acid increases.

[0150] It should be noted that in the above examples, as long as the technical solutions are not contradictory, they can be arranged and combined, and those skilled in the art can exhaust all possibilities according to the mathematical knowledge of arrangement and combination, so the present application will not explain the technical solutions after arrangement and combination one by one, but it should be understood that the technical solutions after arrangement and combination have been disclosed by the present application.

[0151] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Those skilled in the art can make various changes and modifications to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a purslane composite coating preservative, characterized in that: A purslane composite coating preservative reagent composition, by volume percentage: 7%-9% glycerol, 25%-35% sodium alginate, 0.17%-2.5% carrageenan, and purslane aqueous extract; The method includes the following steps: Step 1: Heat the purslane aqueous extract to a suitable temperature; Step II: Add sodium alginate to the purslane water extract and stir continuously until well mixed; Step 3: Add glycerin and stir continuously until well combined; Step IV: Add carrageenan and stir continuously until well combined; Step V: Adjust the pH to the appropriate value.

2. The method for preparing the purslane composite coating preservative according to claim 1, characterized in that: The reagent composition of a purslane composite coating preservative, by volume percentage, is: glycerin 8%, sodium alginate 30%, carrageenan 0.2%, and purslane water extract 61.8%.

3. The method for preparing the purslane composite coating preservative according to claim 1, characterized in that: In step I, the purslane aqueous extract is heated to 60°C. In step IV, acetic acid is added to adjust the pH to 3.

4. A method for preserving edible fungi using a purslane composite coating preservative, characterized in that: The purslane composite coating preservative prepared by any one of the preparation methods described in claims 1-3 includes the following steps: Step 1: Process the edible fungi; Step 2: Apply a coating to the processed edible fungi.

5. The method for preserving edible fungi using the purslane composite coating preservative according to claim 4, characterized in that: Step one includes the following steps: Step 1.1: Screening edible fungi: Screen king oyster mushrooms that are uniform in size, consistent in maturity, and free from mechanical damage; Step 1.2: Slicing: Slice the king oyster mushrooms into pieces 5 cm in diameter and 1 cm thick; Step two includes the following steps: Step 2.1: Apply preservative: Place the sliced ​​king oyster mushrooms in the prepared purslane coating preservative and let stand for 1 minute. Then remove them with tweezers and let them air dry naturally. Step 2.2: Refrigerate for later use.

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