Preparation method and application of selenium-enriched kombucha fresh-keeping liquid

Abstract

The invention discloses a preparation method and application of a selenium-rich kombucha fresh-keeping solution, and belongs to the technical field of fruit and vegetable fresh-keeping, and the preparation method comprises the following steps: preparing a kombucha culture solution; inoculating a kombucha strain; applying exogenous selenium; culturing a selenium-rich kombucha liquid; application of the selenium-rich kombucha fresh-keeping liquid; and evaluating the fresh-keeping effect of the shiitake mushrooms. The selenium-rich kombucha fresh-keeping liquid is prepared from various exogenous selenium by utilizing the characteristic of relatively high selenium gathering capacity of microorganisms, and the influence of the selenium-rich kombucha on the nutritional quality, selenium enrichment capacity and antioxidant enzyme activity of the picked shiitake mushrooms is researched by taking the shiitake mushrooms as a test material, so that an effective strategy is provided for improving the quality of the shiitake mushrooms and prolonging the shelf life of the shiitake mushrooms. And a safe and effective selenium-rich mushroom production mode is provided, the additional value of mushrooms is increased, and an effective scheme is provided for promoting the development of the selenium-rich edible mushroom industry.

Description

Technical Field

[0001] The present invention belongs to the technical field of fruit and vegetable preservation, and particularly relates to a preparation method and application of a selenium-rich kombucha preservation solution. Background Art

[0002] Lentinula edodes (Berk.) Pegler is the second largest cultivated edible mushroom in the world and has important edible and economic values. Lentinula edodes can absorb and utilize selenium to synthesize various organic selenium metabolites, such as selenium amino acids and selenium polysaccharides with excellent biological activities, and is an important daily selenium supplement in the food industry.

[0003] Selenium is the active center of selenoenzymes and selenoproteins and has many important biological functions, such as antioxidant, immunomodulatory, and antagonistic effects. Insufficient selenium intake in humans can cause a series of diseases such as abnormal thyroid metabolism, immune dysfunction, diabetes, cardiovascular diseases, and Kashin-Beck disease. It is estimated that about 1 billion people worldwide lack selenium. According to the recommended values of WHO / FAO (26 - 34 μg / Day), 39 - 61% of Chinese residents have a low daily selenium intake. Therefore, it is necessary to supplement sufficient selenium to maintain human health, prevent diseases, and delay aging.

[0004] Kombucha fermentation broth is a traditional acidic tea beverage fermented by various microorganisms such as yeasts, lactic acid bacteria, and acetic acid bacteria. Its fermentation broth contains various nutritional factors and natural antibacterial components (chitosan), which have inhibitory effects on Escherichia coli, Bacillus subtilis, and Staphylococcus aureus. It has the advantages of safety, non-toxicity, and no pollution, and has been widely used in the storage and preservation of fruits and vegetables, but the application of kombucha in the storage and preservation of edible mushrooms has not been reported. Currently, a single preservation method often fails to achieve good preservation effects.

[0005] Based on this, we propose a preparation method and application of a selenium-rich kombucha preservation solution, hoping to solve the deficiencies in the existing technology. Summary of the Invention

[0006] The purpose of the present invention is to provide a preparation method and application of a selenium-rich kombucha preservation solution for the existing problems.

[0007] The present invention is achieved by the following technical solutions: A preparation method of a selenium-rich kombucha preservation solution includes the following steps: S1. Preparation of kombucha culture broth Boil sucrose, tea bags, and distilled water together, filter after boiling, and then transfer the filtrate to a glass wide-mouth bottle and cool it to room temperature to obtain kombucha culture broth (Kombucha Culture Medium, Ku-CM); S2, Inoculation Inoculate the old Kombucha film and the fermentation broth of Kombucha into the above-mentioned Kombucha culture medium (Ku-CM). Place the inoculated culture medium in a dark environment with a day-night temperature of 30°C / 28°C and ferment for 2 weeks to obtain Kombucha culture liquid (Kombucha Culture Liquid, Ku-CL). S3, Addition of Exogenous Selenium Prepare an exogenous selenium mother liquor, take it out and cool it after sterilization, then add the exogenous selenium mother liquor to the Kombucha culture liquid (Ku-CL), place it in an incubator and let it stand for 2 weeks, and then filter and sterilize to obtain selenium-enriched Kombucha fresh preservative liquid (Selenium-Enriched Kombucha Fresh Preservative Liquid, SKFP).

[0008] Furthermore, the mass ratio of the tea bag to sucrose in step S1 is 1:40; The mass-volume ratio of the tea bag to water is 2.5 g:1 L.

[0009] Furthermore, the mass-volume ratio of the old Kombucha film to the fermentation broth of Kombucha in step S2 is 1 g:1 mL; The temperature during fermentation is controlled at 27-29°C.

[0010] Furthermore, the exogenous selenium in step S3 is one of nano-selenium, sodium selenite, and sodium selenate.

[0011] Furthermore, the concentration of the mother liquor in step S3 is 100 mM.

[0012] Furthermore, the temperature during sterilization in step S3 is controlled at 121°C and the time is 15-25 min.

[0013] Furthermore, the filtration and sterilization in step S3 specifically refers to filtration through a 0.22 μm bacterial filter membrane.

[0014] Furthermore, the addition concentrations of exogenous selenium in the selenium-enriched Kombucha fresh preservative liquid (SKFP) in step S3 are as follows: nano-selenium 0.2-1.6 mM, sodium selenate 0.2-0.8 mM, and sodium selenite 0.2-0.8 mM.

[0015] The application of a selenium-enriched Kombucha fresh preservative liquid in the preservation of shiitake mushrooms includes: picking fresh shiitake mushrooms, spraying the above-mentioned selenium-enriched Kombucha fresh preservative liquid on the shiitake mushrooms with a sprayer, evenly spraying to all parts of the shiitake mushrooms, then standing for 8-10 h until a complete protective film is formed on the surface, and then storing in a 4°C refrigerator.

[0016] Furthermore, the processed shiitake mushrooms should be placed in polyethylene bags (0.04 mm thick) measuring 28 cm × 30 cm and further stored in a cold room (maintained at 4 ± 1 °C and 95% relative humidity) for 24 d. During the storage period, 3 strains of fungi were randomly selected from each group every 6 d for the analysis of their physical and chemical indexes and enzyme activities The present invention has the following advantages compared with the prior art: 1. The present invention utilizes the characteristic of strong selenium-accumulating ability of microorganisms, prepares a selenium-enriched kombucha fresh preservative liquid (SKFP) using various exogenous selenium sources, and takes shiitake mushrooms as test materials to study the effects of selenium-enriched kombucha on the postharvest nutritional quality, selenium-accumulating ability and antioxidant enzyme activities of shiitake mushrooms, providing an effective strategy for improving the quality and extending the shelf life of shiitake mushrooms.

[0017] 2. The selenium-enriched kombucha fresh preservative liquid (SKFP) of the present invention is a pollution-free and edible green preservative, and the chitosan rich in kombucha can form an edible coating on the surface of shiitake mushrooms.

[0018] 3. The present invention uses the method of exogenous selenium application to enhance the fresh preservation effect of kombucha. Kombucha has a good organic selenium conversion efficiency, up to 55.76%, which proves that the application of this fresh preservative liquid is beneficial to enhancing the organic selenium content of shiitake mushrooms. After exogenous selenium treatment of kombucha, all three selenium sources can significantly increase the total selenium content and organic selenium content of kombucha, and the total selenium level of shiitake mushrooms is increased by 4.45 - 72.28 times compared with the water treatment group. The main selenium form in shiitake mushrooms is SeMet, and the highest organic selenium content in shiitake mushrooms reaches 15.49 mg / Kg.

[0019] 4. The selenium-enriched kombucha fresh preservative liquid (SKFP) in the present invention improves the sensory quality, hardness, weight loss and MDA level of shiitake mushrooms. And it provides a fresh preservation scheme for improving the quality and efficiency of shiitake mushrooms. Increasing exogenous selenium treatment improves the nutritional quality of shiitake mushrooms and increases the contents of total soluble sugar, soluble protein, free amino acids and ascorbic acid in shiitake mushrooms.

[0020] 5. The present invention uses the method of applying exogenous selenium to kombucha for food fresh preservation, which is simple, safe and effective. By enhancing the fresh preservation energy storage effect of kombucha with exogenous selenium, the operation is simple and easy to promote. And during the fresh preservation process of shiitake mushrooms, the purpose of improving the quality and efficiency of shiitake mushrooms is achieved, which is beneficial to the promotion of the selenium-rich industry. Description of the Drawings

[0021] Figure 1 It is a schematic diagram for the preparation and characterization of the selenium-enriched kombucha fresh preservative liquid (SKFP); Figure 2To evaluate the postharvest quality of Shiitake mushrooms using selenium-enriched Kombucha preservative solution (SKFP); Figure 3 To evaluate the nutritional status of shiitake mushrooms treated with selenium-enriched kombucha preservative solution (SKFP); Figure 4 To evaluate the antioxidant enzyme activities of Lentinus edodes treated with selenium-enriched kombucha preservative solution (SKFP). DETAILED DESCRIPTION

[0022] In order to further explain the present invention, it is described below in conjunction with the following specific embodiments.

[0023] The black tea fungus strains involved in the present invention were purchased from Shandong Zhishi Black Tea Fungus, and the mushrooms involved were purchased from the agricultural material market in Jingzhou City, Hubei Province. Unless otherwise specified, the raw materials, reagents, and equipment involved in the following examples were all obtained from commercial sources.

[0024] When evaluating the preservation effect, the cap of shiitake mushrooms was taken and randomly sampled. Twenty shiitake mushrooms were grouped in each treatment group to measure the total selenium, selenium form, weight loss, hardness, soluble sugar, soluble protein, free amino acids, vitamins, and MDA activity of shiitake mushrooms, and record the values.

[0025] Example 1 Application of selenium-enriched kombucha preservative liquid in shiitake mushroom preservation comprises the following steps: S1. Prepare Kombucha Culture Medium (Ku-CM) by mixing distilled water, sucrose and Kombucha bag in a ratio of 4 L:400 g:10 g. During the preparation, boil the sucrose, black tea bag and distilled water together, filter the mixture after boiling, transfer the filtrate to a glass wide-mouth bottle, and cool it to room temperature to obtain Kombucha Culture Medium (Ku-CM); S2. Complete the kombucha inoculation on the clean bench. Inoculate 10 g of old kombucha bacterial film and 10 mL of kombucha fermentation liquid into every 200 mL of kombucha culture liquid (Ku-CM). Then place it in an incubator for dark culture at a day and night temperature of 30°C / 28°C. Ferment for 2 weeks to obtain kombucha culture liquid (Ku-CL). S3. Prepare a stock solution with a concentration of 100 mM of nano-selenium / sodium selenite / sodium selenate, sterilize it at 121 °C for 20 min, take it out and cool it. Inoculate it into the Kombucha tea fungus liquid (Ku-CL) at ratios of 2%, 4%, 8%, and 16%. Place the inoculated Kombucha tea fungus liquid (Ku-CL) with exogenous selenium in an incubator for static culture for 2 weeks, and then filter and sterilize it through a 0.22 μm bacterial filter membrane. Thus, the Selenium-Enriched Kombucha Fresh Preservative Liquid (SKFP) is successfully prepared; The exogenous selenium in the Selenium-Enriched Kombucha Fresh Preservative Liquid (SKFP) is one of nano-selenium, sodium selenate, and sodium selenite. The added concentration of exogenous selenium in the Selenium-Enriched Kombucha Fresh Preservative Liquid (SKFP) is 0.2 - 1.6 mM nano-selenium, 0.2 - 0.8 mM sodium selenate, or 0.2 - 0.8 mM sodium selenite; S4. Take several freshly harvested shiitake mushrooms, spray 10 mL of the above-mentioned preservative liquid on each mushroom with a sprayer, evenly spray it on all parts of the shiitake mushrooms, and let it stand for about 8 h until a complete protective film is formed on the surface. Then store it in a 4 °C refrigerator. Among them, the best can extend the preservation time of shiitake mushrooms by about 20 d.

[0026] Example 2 1. Use a hydride generation-atomic fluorescence spectrometer (HG-AFS) to determine the total selenium and selenium species in the Selenium-Enriched Kombucha Fresh Preservative Liquid (SKFP), and evaluate its organic selenium conversion ability and its application in improving the quality and efficiency of shiitake mushrooms.

[0027] The specific operation is as follows: Accurately weigh and measure 2 mL of the Selenium-Enriched Kombucha Fresh Preservative Liquid (SKFP) into a digestion tube, add 10 mL of HNO3 and 2 mL of H2O2 respectively, mix evenly, and then place it in a microwave digestion instrument for digestion. The instrument parameters are set as follows: initial temperature 50 °C, programmed temperature increase: 50 - 120 °C, keep warm for 2 min at 120 °C for 12 min; 120 - 150 °C, keep warm for 5 min at 150 °C for 6 min, 150 - 180 °C, keep warm for 20 min at 180 °C for 10 min. After the digestion is completed and cooled, transfer it to a graphite digestion instrument and continue to heat until almost dry, then add 5 mL of hydrochloric acid (6 mol / L) and continue to heat until the solution becomes clear. After cooling, transfer it to a 10 mL volumetric flask, add 2.5 mL of potassium ferricyanide solution (100 g / L), add water to make up the volume to 10 mL, mix well, filter it with a 0.45 μm filter membrane, and wait for measurement.

[0028] 2. The selenium species in the selenium-enriched kombucha preservation solution (SKFP) were determined using a liquid chromatography-atomic fluorescence spectrometer (LC-AFS) with a negative high voltage of 280 V, a lamp current of 60 mA, a carrier gas flow rate of 300 mL / min, a shielding gas flow of 800 mL / min, an injection volume of 1 mL, and a delay time of 1 min. Three biological and technical replicates were set for each group of samples.

[0029] Accurately weigh 2 mL of the selenium-enriched kombucha preservation solution into a 10 mL centrifuge tube, add 10 mL of protease XIV (8 mg / mL Sigma Aldrich, USA), mix well, place it on a shaker at 120 rpm and 37 °C for 16 h, then take it out after ultrasonication in an ultrasonic cleaner for 30 min, centrifuge at 12,000 rpm and 4 °C for 15 min, and filter with a 0.22 μm filter membrane for further measurement. The injection volume is 100 μL. The model of the anion exchange column is COLUMN PRP-X100 10 μm 250×2.1 mm, the negative high voltage is 320 V, the lamp current is 80 mA, and the carrier gas flow rate is 600 mL / min. Three biological replicates were set for each group of samples.

[0030] As Figure 1 shown, with the increase in the concentration of exogenous selenium treatment, the total selenium content in the selenium-enriched kombucha preservation solution (SKFP) showed an increasing trend, indicating that kombucha has a certain selenium absorption capacity. Among them, compared with the control group, the total selenium content in the nano-selenium treatment group increased by 2.4 times, 3.3 times, 4.7 times, and 5.4 times respectively. The total selenium content in the sodium selenate treatment group increased by 10.8 times, 25.8 times, and 43.8 times respectively compared with the control group; the total selenium content in the sodium selenite treatment group increased by 5.4 times, 10.1 times, and 19.0 times respectively compared with the control group. Kombucha has a high organic selenium conversion efficiency, and its main selenium species is SeMet, which provides a guarantee for the quality improvement and efficiency increase plan of Lentinula edodes. The organic selenium conversion efficiencies in the sodium selenate treatment group were 10.59%, 55.76%, and 52.29% respectively; the organic selenium conversion efficiencies in the sodium selenite treatment group were 2.75%, 34.62%, and 27.51% respectively.

[0031] Example 3 Use a Cannon camera to take pictures every 6 d to observe the phenotype of Lentinula edodes after treatment with the selenium-enriched kombucha preservation solution (SKFP).

[0032] The test results are as Figure 2 shown. At 18 d in the middle and late stages of the treatment, 30 students were invited to give sensory scores to the Lentinula edodes in different treatment groups (5 Lentinula edodes in each treatment group). A protective film was formed on the surface of the Lentinula edodes treated with the selenium-enriched kombucha preservation solution, and the phenomenon of water loss and shrinkage during the preservation process of Lentinula edodes was significantly improved.

[0033] The TMS-PRO texture analyzer equipped with a cylindrical probe (6 mm in diameter) was used to measure the mushroom caps. A penetration depth of 5 mm was applied at a penetration speed of 2.0 mm / s, and the hardness was obtained from the force-time curve and expressed in Newtons (N). The weight loss rate was calculated from the weight measured every 3 days, and each measurement was repeated 3 times.

[0034] The test results showed ( Figure 2 ), in the 0.8 mM and 1.6 mM SKFP-Nano-Se treatment groups, the weight loss of the shiitake mushrooms decreased by 22.8% and 25.7%, respectively. In the 0.2 mM, 0.4 mM, and 0.8 mM SKFP-SeNa treatment groups, the weight loss of the shiitake mushrooms decreased by 72.8%, 83.8%, and 68.4%, respectively. In the 0.2 mM, 0.4 mM, and 0.8 mM SKFP-SeNi treatment groups, the weight loss of the shiitake mushrooms decreased by 68.4%, 77.9%, and 61.0%, respectively. In the 0.2 mM, 0.4 mM, 0.8 mM, and 1.6 mM SKFP-Nano-Se treatment groups, the hardness of the shiitake mushrooms increased by 1.53-fold, 1.13-fold, 1.19-fold, and 1.47-fold, respectively. In the 0.2 mM, 0.4 mM, and 0.8 mM SKFP-SeNa treatment groups, the hardness of the shiitake mushrooms increased by 1.66-fold, 1.34-fold, and 1.37-fold, respectively. In the 0.2 mM, 0.4 mM, and 0.8 mM SKFP-SeNi treatment groups, the hardness of the shiitake mushrooms increased by 2.26-fold, 1.90-fold, and 1.47-fold, respectively. The hardness of the simple Kombucha treatment group (KEP) increased by 1.44-fold.

[0035] Example 4 The nutritional quality indexes (total selenium, selenium species, soluble sugar, soluble protein, free amino acid, ascorbic acid) of the shiitake mushrooms treated with the selenium-rich Kombucha preservation solution (SKFP) were evaluated to examine its preservation effect and selenium enrichment ability.

[0036] As Figure 3 shown, after treatment with SKFP, the selenium indexes of the shiitake mushrooms were also significantly improved. In the 0.4 mM SKFP-SeNi treatment group, the total selenium content of the shiitake mushrooms reached 15.49 mg / kg, which was 72.28-fold higher than that of the control group. The main selenium species in the shiitake mushrooms was SeMet.

[0037] Table 1 Total selenium and selenium species contents of shiitake mushrooms The soluble protein content of the shiitake mushrooms was determined using Coomassie Brilliant Blue G-250. Please refer to Figure 3, the decrease in the content of soluble proteins by [X] times is considered an important indicator of tissue senescence and a sensitive indicator of tissue damage. The content in the Kombucha treatment group was 1.38 times that of the water control group. In the 0.2 mM / 0.4 mM / 0.8 mM / 1.6 mM SKFP-Nano-Se treatment groups, the soluble protein content in Lentinula edodes was 0.90 times, 1.32 times, 1.06 times, and 0.89 times that of the control group. In the 0.2 mM, 0.4 mM, 0.8 mM SKFP-SeNa treatment groups, the soluble protein content in Lentinula edodes was 1.21 times, 0.79 times, and 1.42 times that of the control group. In the 0.2 mM, 0.4 mM, 0.8 mM SKFP-SeNi treatment groups, the soluble protein content in Lentinula edodes was 1.81 times, 1.18 times, and 1.68 times that of the control group.

[0038] The soluble sugar content in Lentinula edodes was determined by the anthrone colorimetric method. Carbohydrates are organic osmotic regulators for plants to actively adapt to stress. The content in the Kombucha treatment group was 1.16 times that of the water control group. In the 0.2 mM / 0.4 mM / 0.8 mM / 1.6 mM SKFP-Nano-Se treatment groups, the soluble sugar content in Lentinula edodes was 1.00 times, 1.04 times, 1.00 times, and 1.05 times that of the control group. In the 0.2 mM, 0.4 mM, 0.8 mM SKFP-SeNa treatment groups, the soluble protein content in Lentinula edodes was 1.03 times, 1.09 times, and 1.02 times that of the control group. In the 0.2 mM, 0.4 mM, 0.8 mM SKFP-SeNi treatment groups, the soluble protein content in Lentinula edodes was 1.07 times, 1.05 times, and 1.04 times that of the control group.

[0039] The method for determining ascorbic acid in Lentinula edodes is as follows. Weigh 0.2 g of the Lentinula edodes pileus, add 5 mL of oxalic acid-EDTA solution and grind it into a homogenate. Then add 2 mL of oxalic acid-EDTA solution to wash the mortar and pestle, and transfer it to a 10 mL centrifuge tube, and make the volume of each tube up to 7 mL. After ultrasonicating the homogenate for 15 min, centrifuge the liquid at 4000 rpm for 10 min, and take 1 mL of the supernatant and measure it in the same way as the standard tube.

[0040] The determination of free amino acids and MDA in Lentinula edodes was carried out using commercial enzyme activity assay kits according to the manufacturer's instructions. They were purchased from Solarbio (BC0595-100T / 96S) and Nanjing Jiancheng Bioengineering Institute, Ltd, Nanjing, China (A003-1-2) respectively. Amino acids are essential nutrients for the human body and play extremely important roles in the prevention and recovery of human diseases. The L. edodes treated with Kombucha was 1.23 times that of the water control group. In the 0.2 mM / 0.4 mM / 0.8 mM / 1.6 mM SKFP-Nano-Se treatment groups, the soluble sugar content of L. edodes was 1.62 times, 1.37 times, 1.89 times, and 2.45 times that of the control group. In the 0.2 mM, 0.4 mM, 0.8 mM SKFP-SeNa treatment groups, the soluble protein content of L. edodes was 1.45 times, 2.00 times, and 1.42 times that of the control group. In the 0.2 mM, 0.4 mM, 0.8 mM SKFP-SeNi treatment groups, the soluble protein content of L. edodes was 1.00 times, 0.67 times, and 2.58 times that of the control group.

[0041] A total of 12 treatment groups (including 3 replicates) were set up in the experiment, including a water treatment group (CK), a Kombucha treatment group, and different concentrations of SKFP-Nano-Se (0.2 - 1.6 mM), SKFP-SeNa (0.2 - 0.8 mM), and SKFP-SeNi (0.2 - 0.8 mM). Determination of antioxidant enzyme activities (SOD, CAT, PAL, GSH-pX). Under ice bath conditions, the L. edodes pileus tissue (0.5 g) was homogenized with 5 mL of 0.1 Mm PBS (pH 7.8). The homogenate was centrifuged at 10,000 × g for 20 min at 4°C, and the supernatant was collected and used as a crude enzyme extract for the determination of SOD, CAT, PAL, and GSH-pX enzyme activities. The activities of antioxidant enzymes were measured using a commercial enzyme activity assay kit (Nanjing Jiancheng Bioengineering Institute, Ltd, Nanjing, China) according to the manufacturer's instructions.

[0042] Superoxide dismutase (SOD) plays an important role in the antioxidant defense mechanism. In the samples of all treatment groups, the decline rate of the preservation solution treatment group slowed down to varying degrees. Among them, the enzyme activity of the Kombucha treatment group samples increased by 13.31% compared with that of the water treatment group. The enzyme activities of the 0.2 mM, 0.4 mM, 0.8 mM, and 1.6 mM SKFP-Nano-Se treatment groups increased by 40.41%, 31.38%, 40.41%, and 46.05% respectively. The enzyme activities of the preservation solution treatment groups prepared with 0.2 mM, 0.4 mM, and 0.8 mM SKFP-SeNa increased by 81.83%, 24.10%, and 34.03% respectively. The enzyme activities of the preservation solution treatment groups prepared with 0.2 mM, 0.4 mM, and 0.8 mM sodium selenite decreased by 42.21%, 8.75%, and 19.58% respectively.

[0043] Catalase plays an important role in the process of H2O2 degradation and can protect the stability and integrity of cells. Among them, the enzyme activity of the Kombucha treatment group samples increased by 17.50% compared with that of the water treatment group. The enzyme activities of the 0.2 mM, 0.4 mM, 0.8 mM, and 1.6 mM SKFP-Nano-Se treatment groups increased by 191.88%, 43.55%, 67.46%, and 149.31% respectively. The enzyme activities of the 0.2 mM, 0.4 mM, and 0.8 mM SKFP-SeNa treatment groups increased by 189.36%, 154.95%, and 121.51% respectively. The enzyme activities of the 0.2 mM, 0.4 mM, and 0.8 mM SKFP-SeNi treatment groups decreased by 185.08%, 138.03%, and 115.48% respectively.

[0044] Glutathione peroxidase (GSH-pX) specifically catalyzes the reduction reaction of reduced glutathione (GSH) to hydrogen peroxide, which can play a role in protecting the integrity of the cell membrane structure and function. Among them, the enzyme activity of the Kombucha treatment group samples was 1.49 times that of the water treatment group. The enzyme activities of the 0.2 mM, 0.4 mM, 0.8 mM, and 1.6 mM SKFP-Nano-Se treatment groups increased by 2.54 times, 2.88 times, 3.28 times, and 2.57 times respectively. The enzyme activities of the 0.2 mM, 0.4 mM, and 0.8 mM SKFP-SeNa treatment groups were 2.36 times, 2.87 times, and 3.32 times that of the control group respectively. The enzyme activities of the 0.2 mM, 0.4 mM, and 0.8 mM SKFP-SeNi treatment groups were 2.85 times, 3.27 times, and 4.00 times that of the control group respectively.

[0045] PAL enzyme activity is an important indicator for detecting browning of mushroom tissues. Under the treatment of selenium-rich preservation solution, the PAL level of Lentinula edodes remains at a relatively low level. In this measurement, the PAL enzyme activity in the Kombucha preservation solution treatment group decreased by 10.44%. The enzyme activities in the 0.2 mM, 0.4 mM, 0.8 mM, and 1.6 mM SKFP-Nano-Se treatment groups decreased by 39.45%, 40.98%, 49.01%, and 41.90% respectively. The enzyme activities in the 0.2 mM, 0.4 mM, and 0.8 mM SKFP-SeNa treatment groups decreased by 56.20%, 47.30%, and 40.40% respectively compared to the clear water control group. The enzyme activities in the 0.2 mM, 0.4 mM, and 0.8 mM SKFP-SeNi treatment groups decreased by 49.34%, 59.96%, and 64.61% respectively compared to the clear water control group.

[0046] As described above, it is only the preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes should be covered within the protection scope of the present invention.

Claims

1. A preparation method of a selenium-rich kombucha preservation solution, characterized in that, It includes the following steps: S1. Preparation of Kombucha culture solution Boil sucrose, black tea bags and distilled water together. After boiling, filter it, and then transfer the filtrate to a wide-mouth glass bottle and cool it to room temperature to obtain the Kombucha culture solution; S2. Inoculation Inoculate the old Kombucha film and the fermentation broth of Kombucha into the above-mentioned Kombucha culture solution. Place the inoculated culture solution in a dark environment with a day-night temperature of 30°C / 28°C and ferment for 2 weeks to obtain Kombucha liquid; S3. Addition of exogenous selenium Prepare an exogenous selenium mother liquor, take it out and cool it after sterilization, then add the exogenous selenium mother liquor to the Kombucha liquid, place it in an incubator and let it stand for 2 weeks, and then filter and sterilize to obtain the selenium-enriched Kombucha preservative solution.

2. The preparation method of a selenium-rich kombucha preservation solution according to claim 1, characterized in that, In step S1, the mass ratio of the black tea bag to sucrose is 1:40; The mass-volume ratio of the black tea bag to water is 2.5 g:1 L.

3. The preparation method of a selenium-rich kombucha preservation solution according to claim 1, characterized in that, In step S2, the mass-volume ratio of the old Kombucha film to the fermentation broth of Kombucha is 1 g:1 mL; The temperature during fermentation is controlled at 27-29°C.

4. The preparation method of a selenium-rich kombucha preservation solution according to claim 1, characterized in that, In step S3, the exogenous selenium is one of nano-selenium, sodium selenite, and sodium selenate.

5. The preparation method of a selenium-rich kombucha preservation liquid according to claim 4, characterized in that, The concentration of the mother liquor in step S3 is 100 mM.

6. The preparation method of a selenium-rich kombucha preservation solution according to claim 1, characterized in that, In step S3, the temperature during sterilization is controlled at 121°C and the time is 15-25 min.

7. The preparation method of a selenium-rich kombucha preservation solution according to claim 1, characterized in that, In step S3, the filtration and sterilization specifically refer to filtration through a 0.22 μm bacterial filter membrane.

8. The selenium-enriched Kombucha preservative solution prepared by the preparation method of the selenium-enriched Kombucha preservative solution according to any one of claims 1 to 7.

9. Application of the selenium-enriched Kombucha preservative solution according to claim 8 in the preservation of Lentinula edodes.

10. Use of the selenium-enriched kombucha preservation solution according to claim 9 in the preservation of shiitake mushrooms, characterized in that, Take freshly harvested Lentinula edodes, use a sprayer to spray the above-mentioned selenium-enriched Kombucha preservative solution on the Lentinula edodes. After evenly spraying all parts of the Lentinula edodes, let it stand for 8-10 h until a complete protective film is formed on the surface, and then store it in a 4°C refrigerator.

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