Edible mushroom freshness indicating type antibacterial composite packaging film as well as preparation method and application thereof

Abstract

The invention relates to the technical field of intelligent packaging and food quality detection, in particular to an edible mushroom freshness indicating type antibacterial composite packaging film and a preparation method and application thereof. The antibacterial peptide in the composite packaging film is self-assembled and wrapped by sodium bicarbonate and calcium chloride to form a calcium carbonate-antibacterial peptide compound, the calcium carbonate-antibacterial peptide compound can be slowly released in a rotten acid environment and is high in food safety, meanwhile, the calcium carbonate-antibacterial peptide compound is fused into the composite packaging film, wider application can be achieved, and practicability is high; the composite packaging film further comprises cactus anthocyanin as a pH sensitive indicator, and visual color monitoring of the deterioration process is realized, so that the deterioration process of the fresh edible mushrooms in the package can be judged by the composite packaging film in the decay process of the fresh edible mushrooms, the composite packaging film is convenient for practitioners to use, and the service life of the fresh edible mushrooms is prolonged. And moreover, spoilage of a packaged article can be effectively inhibited by releasing the antibacterial peptide.

Description

Technical Field

[0001] The present invention relates to the technical field of intelligent packaging and food quality detection, and in particular to an edible fungus freshness indicating antibacterial composite packaging film, a preparation method and application thereof. Background Art

[0002] The edible fungi market is dominated by the sale of fresh mushrooms. In recent years, consumers have put forward higher requirements for the quality of fresh edible fungi. Therefore, the quality control issues in the logistics, storage and transportation of edible fungi have attracted widespread attention. Fresh mushrooms have vigorous metabolism after harvesting, and the consumption of nutrients is fast. As the storage and transportation period is extended, they are prone to corruption and deterioration. Water evaporation and vigorous respiratory metabolism are the most significant phenomena in the deterioration process. The freshness of edible fungi is an important indicator to determine its value. In the e-commerce logistics environment, it is necessary to adopt appropriate quality monitoring technology and improve the edible fungi preservation and circulation mode. It is of great significance to improve the quality of cross-regional and long-distance logistics storage and transportation, extend the shelf life, and promote the loss reduction and quality preservation of edible fungi.

[0003] In order to extend the shelf life of fresh mushrooms, many preservation technologies have been reported, such as irradiation preservation, atmosphere preservation, magnetic field preservation, chemical preservation (1-methylcyclopropene, amino acids, chlorine dioxide and composite preservatives, etc.), ozone preservation, acid electrolyzed water and plasma activated water preservation, plant extract preservation, microbial preservative preservation, antagonistic bacteria preservation, etc. However, there are still many problems in the application of these preservation technologies to fresh edible fungi: ① It is not suitable for large-scale batch processing; ② The investment cost of processing equipment is high; ③ Due to the special morphological structure of edible fungi, the uniformity of liquid preservative spraying, dipping and fumigation distribution is greatly reduced; ④ The most widely used chemical preservatives have been questioned due to safety issues, and the effective ingredients and working principles of some biological preservatives have not yet been clarified. At present, there is an urgent need for efficient, safe and low-cost preservation monitoring and packaging technologies suitable for the logistics, storage and transportation of fresh edible fungi to reduce post-harvest losses and improve economic benefits.

[0004] Edible fungi often undergo pH changes during storage and transportation after harvest. On the one hand, typical physiological changes such as aging and respiration of edible fungi after harvest often lead to rancidity; on the other hand, they are easily infected by bacteria and fungi, causing sugar fermentation to produce organic acids, aldehydes, ketones and CO2, resulting in a decrease in pH and the formation of corrupt flavors. In view of the actual needs of large storage and transportation of fresh edible fungi at the production site and the need for timely distribution, by developing indicator labels based on the pH change characteristics of edible fungi and integrating them into packaging materials to achieve timely monitoring of freshness, the loss of fresh edible fungi can be reduced and economic benefits can be improved. Summary of the invention

[0005] The purpose of the present invention is to provide an antibacterial composite packaging film with freshness indication for edible fungi, and a preparation method and application thereof. The present invention applies the composite packaging film to the storage and transportation of edible fungi, which can not only monitor the change of freshness, intuitively understand and judge the storage and transportation quality, but also respond to the corruption and deterioration state in the package in a timely manner, delay the corruption and deterioration of the edible fungi in the package to a certain extent, and reduce economic losses.

[0006] In order to achieve the above objectives, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing an edible fungus freshness-indicating antibacterial composite packaging film, comprising the following steps:

[0008] (1) mixing an antimicrobial peptide solution, a CaCl2 aqueous solution, and a NaHCO3 aqueous solution to obtain a mixed solution;

[0009] (2) subjecting the mixed solution to a polymerization reaction, and the precipitate is an antimicrobial peptide-CaCO3 complex;

[0010] (3) mixing the antimicrobial peptide-CaCO3 complex with tri-n-butyl citrate and monoglyceride to obtain material A;

[0011] (4) mixing PE resin and material A to obtain modified masterbatch;

[0012] (5) mixing the modified masterbatch with PE resin, and preparing a PE composite packaging film B using a film blowing machine;

[0013] (6) mixing the sodium alginate aqueous solution, cactus anthocyanin and plasticizer, and performing ultrasonic dispersion to obtain an active membrane solution C;

[0014] (7) One side of the packaging film B is treated with cold plasma and then sprayed with active film liquid C to obtain an edible fungus freshness indicating antibacterial composite packaging film.

[0015] Preferably, the solvent of the antimicrobial peptide solution in step (1) is an ethanol solution; the mass ratio of the antimicrobial peptide to the ethanol solution is 1:8-12; the preparation method of the ethanol solution is: mixing anhydrous ethanol and water in a mass ratio of 1:2-3, and the pH value is 9-10.

[0016] Preferably, the mass ratio of antimicrobial peptide, CaCl2 and NaHCO3 in the mixed solution of step (2) is 1-33:200-250:460-500.

[0017] Preferably, the specific process of the polymerization reaction in step (2) is: the mixed solution is first kept at 4°C for 2 minutes, then kept at 7-9°C for 3-5 minutes each time until the temperature reaches 21-27°C, and the reaction is continued for 3 minutes, and the polymerization reaction is completed; the reaction is stirred throughout the reaction, the stirring speed is 80-200 rpm, and the stirring time is 2-5 minutes.

[0018] Preferably, in step (3), the mass ratio of the antimicrobial peptide-CaCO3 complex to tri-n-butyl citrate and monoglyceride is 0.8-1.2:0.4-0.6:0.08-0.12.

[0019] Preferably, in step (4), the mass ratio of PE resin to material A is 90-100:2-6.

[0020] Preferably, in step (5), the mass ratio of the modified masterbatch to the PE resin is 1:1.8-2.4.

[0021] Preferably, in step (6), the mass ratio of the sodium alginate aqueous solution, the cactus anthocyanin and the plasticizer is 100-105:0.8-12:0.08-1.2.

[0022] The present invention also provides an edible fungus freshness-indicating antibacterial composite packaging film prepared by the preparation method.

[0023] The present invention also provides an application of the edible fungus freshness indicating antibacterial composite packaging film in monitoring the freshness of edible fungi or extending the shelf life of edible fungi.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The cactus anthocyanin in the present invention contains a high proportion of acylated anthocyanin and has higher stability than that from other sources. It will show different colors as the pH value changes, and will show obvious color changes in a buffer solution of pH 3 to 10. It has the advantages of color stability, safety and non-toxicity, and can be used as a pH-sensitive indicator to realize visual color monitoring of the deterioration process. During the corruption process of fresh edible fungi, the deterioration process of fresh edible fungi in the package can be judged, which is convenient for practitioners to use.

[0026] The antimicrobial peptide of the present invention has thermal stability, can still maintain its activity when heated at high temperature, and has strong resistance to large ionic strength and high or low pH value. In addition, the antimicrobial peptide has a certain hydrophobicity, and the formation of CaCO3 by NaHCO3 and CaCl2 is conducive to encapsulating the antimicrobial peptide, and the further formation of the CaCO3 shell has a protective effect on the antimicrobial peptide, which reduces the adverse effects of the antimicrobial peptide in the later granulation process on the one hand, and is conducive to the sustained release of the antimicrobial peptide in the fresh-keeping application process on the other hand.

[0027] During the post-harvest deterioration process, edible fungi breathe vigorously and transpire significantly, which makes them prone to opening, water loss, morphological changes, browning, loss of nutrition and flavor, and microbial infection. In the process of logistics, storage and transportation, it is obvious that it is manifested as water transpiration, tissue rancidity, and vigorous respiration and release of a large amount of CO2. In the package, the edible fungi tissue is in contact with the inner active membrane. With the transpiration release of water in the edible fungi tissue and the decrease in pH value caused by tissue rancidity, the carboxyl groups of sodium alginate in the active membrane tend to be protonated, the molecular chains of sodium alginate further shrink, and gaps appear in the active membrane. As the concentration of CO2 in the micro-atmosphere of the package increases, the trigger indicator label changes from light green to orange-yellow, and further changes to light red or even red as the rancidity deteriorates. In this way, through obvious and distinguishable color changes, the freshness changes of fresh edible fungi during logistics, storage and transportation can be intuitively indicated. As the deterioration process gradually intensifies, the active membrane gaps further increase and even partially degrade. The transpiration of water vapor and rancidity trigger the disintegration of the antimicrobial peptide-CaCO3 complex, releasing antimicrobial peptides, producing antimicrobial effects, inhibiting the spread of corruption and reducing losses.

[0028] The advantages of the technology of the present invention are that in response to the storage and transportation needs of fresh edible fungi, a composite packaging film is developed that can not only monitor the quality changes of fresh edible fungi but also respond promptly to corruption and deterioration. It has indication, monitoring and early warning indication label functions, and can release antimicrobial peptides when fresh edible fungi deteriorate, exert an antibacterial effect, prevent corruption, and extend the shelf life of fresh mushrooms. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the response diagram of cactus anthocyanin to pH (3.0-10.0) in Experimental Example 1;

[0030] Figure 2 This is the visible light absorption spectrum of cactus anthocyanin under different pH conditions in Experimental Example 1;

[0031] Figure 3 is the Fourier transform infrared spectra of different composite packaging films in Experimental Example 2;

[0032] Figure 4 Schematic diagram of thermal stability (TG-DSC) analysis of different composite packaging films in Experimental Example 3;

[0033] Figure 5 This is the color response diagram of the composite packaging film to shiitake mushrooms during storage in Experimental Example 4;

[0034] Figure 6 This is a scanning electron microscope image of the composite packaging film in Experimental Example 5. DETAILED DESCRIPTION

[0035] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0036] Materials and equipment used in the embodiments of the present invention

[0037] PE resin: PE (2426K), purchased from Maoming Branch of Sinopec.

[0038] Low temperature ultrafine grinding equipment: SQW-6A low temperature ultrafine grinding machine, purchased from Jinan Yichen Chaowei Grinding Technology Co., Ltd.

[0039] Twin-screw extrusion granulation equipment: SY-6217 twin-screw extrusion granulation machine, purchased from Dongguan Jiutong Machinery Co., Ltd.

[0040] Film blowing equipment: SY-6218-Z-18 / 28 film blowing machine, Dongguan Jiutong Machinery Co., Ltd.

[0041] Cold plasma treatment equipment: HD-1A cold plasma treatment instrument, Jiangsu Changzhou Zhongke Changheng Plasma Technology Co., Ltd.

[0042] The preparation method of cactus anthocyanidin used in the following experiment includes the following steps:

[0043] (1) Wash and chop fresh cactus and place it in a -80°C ultra-low temperature refrigerator for precooling for 72 hours. Then freeze-dry it at -60°C for 45 hours and grind it into 120 mesh powder for later use.

[0044] (2) 500 mL of 75% ethanol solution was prepared and its pH was adjusted to 3 with 1 mol / L hydrochloric acid. 20 g of cactus powder was extracted at 4° C. for 24 h in a dark environment to obtain an extract.

[0045] (3) The extract was vacuum filtered, the filtrate was rotary evaporated at 50°C for 1 h, and finally cooled to room temperature to obtain an extract of cactus anthocyanins, the soluble solid mass concentration of which was 128.2 g / L.

[0046] Example 1

[0047] An edible fungus freshness-indicating antibacterial composite packaging film, the preparation method of which comprises the following steps:

[0048] 1. Preparation of antimicrobial peptide-CaCO3 complex

[0049] (1) After adding 1 / 3 volume ratio of anhydrous ethanol to deionized water at pH 9.1, the antimicrobial peptide Temporin L was dissolved in the ethanol solution to prepare a 10% (g / g) antimicrobial peptide solution;

[0050] (2) Adding CaCl2 aqueous solution and NaHCO3 aqueous solution to the antimicrobial peptide solution of step (1) in sequence, stirring at a speed of 600 rpm for 15 min to prepare a mixed solution, wherein the mass ratio of the total mass of the antimicrobial peptide, CaCl2 and NaHCO3 in the mixed solution to the solvent is 15:100; wherein the mass ratio of the antimicrobial peptide, CaCl2 and NaHCO3 is 1:200:460.

[0051] (3) The mixed solution of step (3) is polymerized by a staged heating process: the temperature is controlled at 4°C and stirred at 200 rpm for 2 minutes; the temperature is increased to 8°C and stirred at 160 rpm for 3 minutes; the temperature is increased to 16°C and stirred at 100 rpm for 5 minutes; the temperature is increased to 24°C and stirred at 80 rpm for 3 minutes, and then allowed to stand at room temperature, precipitation occurs, and there is no fluid disturbance on the liquid surface.

[0052] (4) Collect the precipitate, wash it with deionized water, centrifuge it, remove the supernatant, repeat the operation three times, and obtain the antimicrobial peptide-CaCO3 complex, which is freeze-dried for later use.

[0053] 2. Crush the antimicrobial peptide-CaCO3 complex to 15 μm at low temperature.

[0054] 3. Mix antimicrobial peptide-CaCO3: tri-n-butyl citrate: monoglyceride in a mass ratio of 1:0.5:0.1, and stir evenly to obtain material A;

[0055] 4. Add PE resin and material A in a mass ratio of 96:4 into a twin-screw extruder, blend and granulate to obtain a modified masterbatch with a diameter of 3 mm.

[0056] Among them, the setting parameters of the twin-screw extruder are 155°C in the die zone, 160°C in the fifth zone, 175°C in the fourth zone, 180°C in the third zone, 170°C in the second zone, and 160°C in the first zone, and the screw speed is 50r / min.

[0057] 5. The modified masterbatch was mixed with PE resin in different mass ratios of 1:2, and a PE composite packaging film was prepared by a film blowing machine. The inner side of the film was treated with a cold plasma treatment device for 5 minutes to obtain packaging film B.

[0058] The setting parameters of the film blowing machine are: film head temperature: 155°C, die head gap 0.8mm, blowing ratio: 2.5:1, pulling speed: 10m / min, and the final thickness of the film is 30μm.

[0059] The setting parameters of the cold plasma treatment equipment are Ar as carrier gas, RF power supply, power of 200W, back vacuum of 15Pa, and discharge vacuum of 40Pa.

[0060] 6. Dissolve 2.5 g of sodium alginate in 100 g of deionized water and heat and stir at 90°C for 30 min to fully dissolve it to obtain a sodium alginate aqueous solution; add 1 g of glycerol as a plasticizer to the sodium alginate aqueous solution, add 4% of cactus anthocyanin by mass to the sodium alginate aqueous solution, and ultrasonically disperse to prepare an active membrane liquid C as an indicator label;

[0061] 7. Spray active film liquid C on the inner side of packaging film B, dry at 60° C. and store for later use, to obtain the composite packaging film of the present invention which can not only monitor the quality changes of fresh edible fungi but also respond to corruption and deterioration in a timely manner.

[0062] Example 2

[0063] An edible fungus freshness-indicating antibacterial composite packaging film, the preparation method of which comprises the following steps:

[0064] 1. Preparation of antimicrobial peptide-CaCO3 complex

[0065] (1) After adding 1 / 3 volume ratio of anhydrous ethanol to deionized water at pH 9.1, the antimicrobial peptide Temporin L was dissolved in the ethanol solution to prepare a 10% (g / g) antimicrobial peptide solution;

[0066] (2) CaCl2 solution and NaHCO3 solution were added to the antimicrobial peptide solution of step (1) in sequence, and the mixture was stirred at 600 rpm for 15 min to prepare a mixed solution, wherein the mass ratio of the total mass of the antimicrobial peptide, CaCl2 and NaHCO3 to the solvent in the mixed solution was 9:100; wherein the mass ratio of the antimicrobial peptide, CaCl2 and NaHCO3 was 33:250:500.

[0067] (3) The mixed solution of step (3) is polymerized by a staged heating process: the temperature is controlled at 4°C and stirred at 200 rpm for 2 minutes; the temperature is increased to 8°C and stirred at 160 rpm for 3 minutes; the temperature is increased to 16°C and stirred at 100 rpm for 5 minutes; the temperature is increased to 24°C and stirred at 80 rpm for 3 minutes, and then allowed to stand at room temperature, precipitation occurs, and there is no fluid disturbance on the liquid surface.

[0068] (4) Collect the precipitate, wash it with deionized water, centrifuge it, remove the supernatant, repeat the operation three times, and obtain the antimicrobial peptide-CaCO3 complex, which is freeze-dried for later use.

[0069] 2. Ultrafinely grind the antimicrobial peptide-CaCO3 complex to 15 μm at low temperature.

[0070] 3. Mix antimicrobial peptide-CaCO3: tri-n-butyl citrate: monoglyceride in a mass ratio of 1:0.5:0.1, and stir evenly to obtain material A;

[0071] 4. Add PE resin and material A in a mass ratio of 96:4 into a twin-screw extruder, blend and granulate to obtain a modified masterbatch with a diameter of 3 mm.

[0072] Among them, the setting parameters of the twin-screw extruder are 155°C in the die zone, 160°C in the fifth zone, 175°C in the fourth zone, 180°C in the third zone, 170°C in the second zone, and 160°C in the first zone, and the screw speed is 50r / min.

[0073] 5. The modified masterbatch was mixed with PE resin in different mass ratios of 1:2, and a PE composite packaging film was prepared by a film blowing machine. The inner side of the film was treated with cold plasma for 5 minutes to obtain packaging film B.

[0074] The setting parameters of the film blowing machine are: film head temperature: 155°C, die head gap 0.8mm, blowing ratio: 2.5:1, pulling speed: 10m / min, and the final thickness of the film is 30μm.

[0075] The setting parameters of the cold plasma treatment equipment are Ar as carrier gas, RF power supply, power of 200W, back vacuum of 15Pa, and discharge vacuum of 40Pa.

[0076] 6. Dissolve 2.5 g of sodium alginate in 100 g of deionized water and heat and stir at 90°C for 30 min to fully dissolve it to obtain a sodium alginate aqueous solution; add 1 g of glycerol as a plasticizer to the sodium alginate aqueous solution, add 4% of cactus anthocyanin by mass to the sodium alginate aqueous solution, and ultrasonically disperse to prepare an active membrane liquid C as an indicator label;

[0077] 7. Spray active film liquid C on the inner side of packaging film B, dry at 60° C. and store for later use, to obtain the composite packaging film of the present invention which can not only monitor the quality changes of fresh edible fungi but also respond to corruption and deterioration in a timely manner.

[0078] Comparative Example 1

[0079] No antimicrobial peptides or cactus anthocyanins were added to the raw materials, and the remaining steps were the same as in Example 1.

[0080] Experimental Example 1

[0081] Color development effect of cactus anthocyanins

[0082] Prepare a buffer solution with a pH value of 3.0 to 10.0 using 0.1 mol / L HCl and 0.1 mol / L NaOH. Take 0.2 mL of the cactus anthocyanin in Example 1 and add it to the above buffer solution. Mix well and let stand for 30 minutes. Take a photo to record the color development of the buffer solution (see Figure 1 ), and the absorbance of the solution was measured at 400-700 nm using an ultraviolet spectrophotometer.

[0083] The results are as follows Figure 2 As shown in the figure, as the pH value increases, the color of the solution changes from red to pink (pH = 3.0-5.0), orange (pH = 6.0), light green (pH = 7.0), green (pH = 8.0-9.0) and dark green (pH = 10.0). This shows that cactus anthocyanins have good pH response characteristics. Figure 2 It can also be seen that the visible light absorption spectra of cactus anthocyanins are different under different pH conditions. When pH = 3.0, the maximum absorption peak of the indicator in the visible light region is at 425nm; when pH = 5.0-6.0, the absorption peak intensity at 230nm drops sharply and red-shifts; when pH = 8.0, the absorption peak intensity at 225nm rises sharply; when pH = 9.0, the wavelength of the maximum absorption peak shifts to the right, and the corresponding wavelength is 615nm; when pH = 4.0, 7.0 and 10.0, the absorption peak almost disappears. Therefore, the color of cactus anthocyanins changes significantly, making them suitable as pH-sensitive indicators.

[0084] Experimental Example 2

[0085] Fourier transform infrared spectroscopy (FT-IR) analysis of the composite packaging film of the present invention

[0086] The composite packaging film with the label position indicated on the inside was sprayed with a Fourier transform infrared spectrometer to measure the absorption spectrum of the sample, with a scanning range of 650 to 4000 cm -1 .

[0087] The results are as follows Figure 3 As shown, except 783cm -1 In addition, no new peaks appeared in the composite packaging films of Comparative Example 1 and Examples 1 and 2, and the main peaks were basically the same, but the peak intensities at different wave numbers were slightly different. -1 The peak at 3435 cm gradually shifts to the left (Example 1 and Example 2 shift to 3435 cm -1 and 3432cm -1 The 2586-2929cm of Example 1 belongs to the stretching vibration absorption peak of the hydroxyl group. -1 The peak band at 2929cm -1 There is a peak shift of 2930cm -1 This is related to the stretching vibration of the methylene group (-CH2). The composite packaging film of Example 1 has a -1 The peak intensity at 1632cm -1 The peak at 1040 cm shifts to the left, which may be related to the stretching vibration of C=C in the film. -1The absorption peak at gradually shifted to the left, and the peak intensity weakened, which may be caused by the stretching vibration of CO. Therefore, the addition of cactus anthocyanins did not cause structural changes in the composite packaging film.

[0088] Experimental Example 3

[0089] Thermal stability (TG-DSC) analysis of the composite packaging film of the present invention

[0090] Thermogravimetric analysis was performed using a thermogravimetric analyzer to evaluate the thermal stability of the composite packaging film sprayed with the indicating label position. 10 mg of the sample was weighed in a thermogravimetric microbalance and heated at a heating rate of 20 °C / min in the temperature range of 30 to 600 °C, with nitrogen as the cooling medium at a flow rate of 20 mL / min.

[0091] like Figure 4 As shown, the mass loss of comparative example 1 has four stages: the first stage is in the range of 25-150°C, which is mainly the loss of free water and bound water in the indicator label. In addition, the weight loss of comparative example 1 is higher than that of the composite packaging film of examples 1-2. The second and third stages are in the range of 150-290°C and 290-360°C, respectively, and the mass loss rate decreases rapidly within this range. The fourth stage is above 360°C, and the downward trend of the mass loss rate slows down significantly. The weight loss of examples 1 and 2 can be divided into three stages, namely 25-160°C (mainly caused by water loss), 160-375°C (mainly caused by oxidative decomposition of substances in the indicator label components) and 375-500°C (carbonization decomposition of other substances). Among the three groups of samples, comparative example 1 has the highest mass loss rate at 500°C, which is 9.92%; followed by example 2, which is 6.78%; and example 1 has the lowest mass loss rate, which is only 5.26%. It can be seen that the addition of cactus anthocyanins inhibits thermal degradation and improves stability.

[0092] Experimental Example 4

[0093] Shiitake mushroom freshness monitoring and preservation performance testing

[0094] The mushrooms were stored at 4°C and (85±5)% relative humidity for 12 days, and the color changes of the corresponding composite packaging films were observed.

[0095] The results are as follows Figure 5 As shown, in Examples 1-2, as the storage time increases and the deterioration of fresh shiitake mushrooms after harvesting intensifies, compared with Comparative Example 1, the color of the composite packaging film in Examples 1-2 gradually changes from the initial green and light green to orange-yellow as the pH of the fresh shiitake mushrooms changes, and the color gradually deepens, and in the later stage, it becomes brown-yellow or even red, with obvious color changes. It can be seen that the composite packaging film loaded with cactus anthocyanins has good response characteristics and shows potential application value.

[0096] Experimental Example 5

[0097] SEM scanning electron microscope analysis of the composite packaging film of the present invention

[0098] The composite packaging film sprayed with the indicating label position in Example 1 was cut, and the surface microstructure of the cut composite packaging film was observed and photographed using a scanning electron microscope. Specifically, a 1 cm × 1 cm sample film was dried, and then gold was sprayed on its surface with an acceleration voltage of 15 KV and a magnification of 10K.

[0099] SEM images mainly reflect the interface morphology and microstructure of the composite system. Figure 6 As shown, the packaging film B treated with cold plasma technology is tightly bonded to the active film liquid C without obvious stratification, and the composite film has good compatibility.

[0100] Experimental Example 6

[0101] Microbiological experiments

[0102] The antibacterial performance test used the liquid culture method to explore the inhibitory effect on Staphylococcus aureus, Escherichia coli, Pseudomonas fluorescens, and Bacillus subtilis.

[0103] Different strains were inoculated into nutrient broth at the corresponding optimal temperature, 150 rpm, and cultured for 24 h. Subsequently, 10 8 CFU / mL bacterial suspension. Take 10cm×10cm composite packaging film sprayed with the indicating label position described in Examples 1 to 2 and Comparative Example 1, dissolve it in water at pH=5 and soak it for 20min, add 100μL soaking solution and 100μL bacterial solution to a 96-well plate, measure the initial absorbance of the mixed solution at 600nm using an ELISA instrument, and after static culture at the corresponding temperature of the strain for 24h, measure the initial absorbance at 600nm again, take the culture medium as the blank control, repeat each group of experiments 3 times, take the average value, and the results are listed in Table 1.

[0104] The inhibition rate (IR%) of the film was calculated as follows:

[0105] IR(%)=(A 24 -A0) / A blank ×100%

[0106] Where: A0 is the absorbance value of the initial mixed solution at 600nm, A 24 A is the absorbance of the solution at 600 nm after 24 h of reaction; blank is the absorbance value of the blank control group solution at 600 nm.

[0107] Table 1 Antibacterial properties of composite packaging films

[0108]

[0109] The results are shown in Table 1. After adding antimicrobial peptides and cactus anthocyanins, the composite packaging film of the present invention exhibits good antimicrobial properties, and the inhibition rate of the four strains is more than 89%, which has a good effect of inhibiting bacterial growth. This is mainly because transpiration and tissue acidification trigger the disintegration of the antimicrobial peptide-CaCO3 complex in the package, releasing antimicrobial peptides to produce antibacterial effects, thereby alleviating the quality deterioration of shiitake mushrooms such as decay and deterioration after harvest, and extending the shelf life of shiitake mushrooms after harvest.

[0110] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing an edible fungus freshness-indicating antibacterial composite packaging film, characterized in that: The following steps are involved: (1) mixing an antimicrobial peptide solution, a CaCl2 aqueous solution, and a NaHCO3 aqueous solution to obtain a mixed solution; (2) subjecting the mixed solution to a polymerization reaction, and the precipitate is an antimicrobial peptide-CaCO3 complex; (3) mixing the antimicrobial peptide-CaCO3 complex with tri-n-butyl citrate and monoglyceride to obtain material A; (4) mixing PE resin and material A to obtain modified masterbatch; (5) mixing the modified masterbatch with PE resin, and preparing a PE composite packaging film B using a film blowing machine; (6) mixing the sodium alginate aqueous solution, cactus anthocyanin and plasticizer, and performing ultrasonic dispersion to obtain an active membrane solution C; (7) One side of the packaging film B is treated with cold plasma and then sprayed with active film liquid C to obtain an edible fungus freshness indicating antibacterial composite packaging film.

2. The preparation method according to claim 1, characterized in that: The solvent of the antimicrobial peptide solution in step (1) is an ethanol solution; the mass ratio of the antimicrobial peptide to the ethanol solution is 1:8-12; the preparation method of the ethanol solution is: anhydrous ethanol and water are mixed in a mass ratio of 1:2-3, and the pH value is 9-10.

3. The preparation method according to claim 1, characterized in that: The mass ratio of antimicrobial peptide, CaCl2 and NaHCO3 in the mixed solution of step (2) is 1-33:200-250:460-500.

4. The preparation method according to claim 1, characterized in that: The specific process of the polymerization reaction in step (2) is as follows: the mixed solution is first kept at 4°C for 2 minutes, then kept at 7-9°C for 3-5 minutes each time until the temperature reaches 21-27°C, and the reaction is continued for 3 minutes, and the polymerization reaction is completed; the reaction is stirred throughout the reaction, the stirring speed is 80-200 rpm, and the stirring time is 2-5 minutes.

5. The preparation method according to claim 1, characterized in that: In the step (3), the mass ratio of the antimicrobial peptide-CaCO3 complex to tri-n-butyl citrate and monoglyceride is 0.8-1.2:0.4-0.6:0.08-0.

12.

6. The preparation method according to claim 1, characterized in that: In the step (4), the mass ratio of PE resin to material A is 90-100:2-6.

7. The preparation method according to claim 1, characterized in that: In the step (5), the mass ratio of the modified masterbatch to the PE resin is 1:1.8-2.

4.

8. The preparation method according to claim 1, characterized in that: In the step (6), the mass ratio of the sodium alginate aqueous solution, the cactus anthocyanin and the plasticizer is 100-105:0.8-12:0.08-1.

2.

9. An edible fungus freshness-indicating antibacterial composite packaging film prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the edible fungus freshness indicating antibacterial composite packaging film according to claim 9 in monitoring the freshness of edible fungi or extending the shelf life of edible fungi.

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