Fruit and vegetable fresh-keeping film and lotus root storage and fresh-keeping method

Abstract

The invention provides a fruit and vegetable fresh-keeping film and a storage and fresh-keeping method of lotus sprouts, and the fruit and vegetable fresh-keeping film is prepared by the following steps: (1) weighing 2-5 parts of lotus root starch, dissolving in 80-100 parts of water, and gelatinizing in a water bath at 80-90 DEG C for 30-60 minutes; (2) adding 1-3 parts of glycerol and 20-60 parts of microemulsion, and uniformly stirring and mixing; (3) carrying out vacuum degassing on the obtained membrane liquid for 20-30 minutes, wherein the vacuum degree is 0.07-0.1 MPa; and (4) casting on a clean glass plate to form a film, drying in an incubator at 40-55 DEG C for 4-6 hours, and uncovering the film to obtain the preservative film. The storage and fresh-keeping method of the lotus sprouts comprises the following steps: cleaning the lotus sprouts, soaking the cleaned lotus sprouts in diluted micro-emulsion, fishing out the soaked lotus sprouts, and naturally airing the fished lotus sprouts; and wrapping the lotus sprouts with a preservative film, and storing. The quality guarantee period of the lotus sprouts can be prolonged to 20 days, and the good taste and appearance of the lotus sprouts are kept.

Description

Technical Field

[0001] The invention relates to the field of storage and preservation of agricultural products, in particular to a storage and preservation method of fruit and vegetable fresh-keeping film and lotus root stems. Background Art

[0002] Lotus stems are a kind of aquatic vegetables with strong regional characteristics, mainly produced in Hubei, Anhui, Hunan and other places in my country. The Compendium of Materia Medica says that lotus stems have the function of "relieving irritability and toxins, and removing blood stasis". Li Shizhen also said that lotus stems have the same function as lotus roots. Fresh lotus stems have a crisp and tender taste, and can be stir-fried, mixed, fried, steamed, deep-fried, sautéed, or eaten raw.

[0003] The growth and harvesting of lotus stems have a certain seasonality, and they mainly grow from May to August each year. As young lotus roots, the water content of lotus stems is as high as over 95%, and the enzyme activity and respiration intensity are much higher than those of mature lotus roots. Their hardness is not as great as those of lotus roots, and their skin is thinner and more delicate. Lotus stems stored at room temperature (28°C) begin to lose water, shrink, and brown one day after being harvested. By the third day of storage, the stems completely turn brown and shrink, and lose their edible value. The preservation of lotus stems is difficult, and in actual production, common preservation methods for lotus stems include low-temperature storage, immersion in water, packaging in fresh-keeping bags, and treatment with fresh-keeping liquid.

[0004] Low temperature (4℃) storage can extend the shelf life of lotus stems, but after 5 days of storage, the stems will still show symptoms such as browning, blackening, lignification, softening and rotting. Vacuum packaging is a common preservation method, which can effectively reduce the browning of lotus stems and keep them bright white. However, vacuum-packed lotus stems generally have a shelf life of 9-12 days and often produce odor, softening and water loss.

[0005] The deterioration of lotus stems has caused great difficulties in their post-harvest transportation, storage and processing, resulting in huge economic losses. Summary of the invention

[0006] In view of the deficiencies of the above-mentioned prior art, the present invention provides a fruit and vegetable preservative film and a storage and preservation method for lotus root stems. The preservative film has a good preservation effect on lotus root stems, can extend the shelf life of lotus root stems to 20 days, and maintain the good taste and appearance of the lotus root stems.

[0007] The technical solution provided by the present invention is a fruit and vegetable fresh-keeping film, which is prepared by the following method: (1) weighing 2-5 parts of lotus root starch by weight and dissolving it in 80-100 parts of water, and gelatinizing it in a water bath at 80-90° C. for 30-60 minutes; (2) adding 1-3 parts of glycerol and 20-60 parts of microemulsion, and stirring and mixing them evenly; (3) vacuum degassing the obtained film liquid for 20-30 minutes, and the vacuum degree is 0.07-0.1MPa; (4) casting the degassed film liquid into a film, drying it in an incubator at 40-55° C. for 4-6 hours, and peeling off the film to obtain the fresh-keeping film;

[0008] The microemulsion is prepared from the following components, calculated by weight: 1-2 parts of sorbic acid, 1-2 parts of carvacrol, 1-4 parts of caprylic decanoate, 3-8 parts of polyethylene glycol, 12-32 parts of Tween 80, 0-2 parts of chitosan, 0-1.2 parts of acetic acid and 41-112 parts of water.

[0009] Furthermore, the preparation method of the microemulsion comprises the following steps:

[0010] (1) uniformly mixing Tween 80, sorbic acid, carvacrol, caprylic decanoate, and polyethylene glycol according to a weight ratio to form a mixed solution;

[0011] (2) preparing an acetic acid aqueous solution, adding chitosan, and obtaining a chitosan-acetic acid aqueous solution;

[0012] (3) Adding the chitosan-acetic acid aqueous solution obtained in step (2) dropwise to the mixed solution obtained in step (1) while stirring until the entire system changes from clear to turbid and then to clear again, thereby obtaining a microemulsion.

[0013] Furthermore, the fruit and vegetable fresh-keeping film is used for the storage and preservation of lotus stems.

[0014] A method for storing and preserving lotus stems, using the above-mentioned fruit and vegetable preservative film, comprises the following steps:

[0015] (1) Cleaning of lotus stems

[0016] The harvested lotus stems are washed to remove the sludge residue and the bottom 2-3 cm long portion of the lotus stems is removed; the washed lotus stems are immersed in cold water for precooling;

[0017] (2) Fresh-keeping packaging of lotus stems

[0018] The lotus stems processed in step (1) are immersed in the diluted microemulsion, then picked up and naturally dried; the lotus stems are wrapped with plastic wrap and stored.

[0019] Furthermore, the temperature of the cold water is 0-4°C, and the pre-cooling time is 20-30 minutes.

[0020] Furthermore, the microemulsion is diluted with water, the dilution multiple of the microemulsion is 100-200 times, the ratio of lotus stem to the diluted microemulsion liquid during soaking is (1:2-4) g / mL, and the soaking time is 8-12 min.

[0021] Furthermore, the storage conditions are a temperature of -1-4°C and a humidity of 70-90%.

[0022] Beneficial effects of the present invention:

[0023] (1) The lotus stem deteriorates rapidly. It turns completely brown within 3 days of storage at room temperature (25°C), only 5-8 days at low temperature (4°C), and only 9-12 days in vacuum packaging. The lotus stem treated by the present invention can extend the shelf life of the lotus stem to 20 days and maintain the good taste and appearance of the lotus stem.

[0024] (2) The microemulsion prepared by the present invention exerts the synergistic antibacterial and antioxidant effects of sorbic acid and carvacrol, and can be further made into a fresh-keeping film. Both of them have good antibacterial effects on pathogenic fungi of lotus stems, and their combined use has a good fresh-keeping effect on lotus stems.

[0025] (3) The fresh-keeping ingredients used in the present invention are green and safe, the prepared microemulsion and fresh-keeping film are edible, and the preparation method is simple, economical and efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is the appearance picture of the microemulsion and the preservative film prepared by the present invention;

[0027] Figure 2 This is a diagram showing the effects of lotus stems stored for 20 days in Examples 1 / 4 / 5 and Comparative Examples 1-3 of the present invention;

[0028] Figure 3 This is a graph showing changes in the total number of bacteria during storage of lotus stems in Examples 1 / 4 / 5 and Comparative Examples 1-3 of the present invention;

[0029] Figure 4 This is a graph showing changes in the total number of molds and yeasts during storage of lotus stems in Examples 1 / 4 / 5 and Comparative Examples 1-3 of the present invention;

[0030] Figure 5 It is a data graph of the color difference values ​​of lotus stems during storage of Examples 1 / 4 / 5 and Comparative Examples 1-3 of the present invention;

[0031] Figure 6 It is a data chart of the hardness values ​​of lotus stems during storage of Examples 1 / 4 / 5 and Comparative Examples 1-3 of the present invention. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0033] Example 1

[0034] A method for storing and preserving fruit and vegetable fresh-keeping film and lotus root stems, comprising the following steps:

[0035] 1. Preparation of microemulsion: (1) Weigh 1 part of sorbic acid, 1 part of carvacrol, 1 part of caprylic acid glyceride, 3 parts of polyethylene glycol, and 12 parts of Tween 80, mix well to prepare a mixed solution; (2) Take 0.4 parts of acetic acid, dissolve it in 41 parts of water to prepare an acetic acid aqueous solution, add 0.6 parts of chitosan to obtain a chitosan-acetic acid aqueous solution; (3) While stirring the mixed solution in (1), add the chitosan-acetic acid aqueous solution in (2) drop by drop until the whole system changes from clear to turbid and then to clear. The microemulsion is obtained.

[0036] 2. Preparation of cling film: (1) Weigh 4 parts of lotus root starch and dissolve it in 100 parts of water, and gelatinize it in a water bath at 85°C for 60 minutes; (2) Add 1.2 parts of glycerol and 25 parts of microemulsion, and stir to mix evenly; (3) Vacuum degas the obtained film liquid for 20 minutes, and the vacuum degree is 0.08MPa; (4) Cast it into a film on a clean glass plate, dry it in an incubator at 50°C for 4 hours, and then peel off the film to obtain the cling film.

[0037] 3. Cleaning of lotus stems: Clean the harvested lotus stems to remove sludge and residue, and remove the 2-3 cm long part at the bottom of the stems; immerse the cleaned lotus stems in 0℃ cold water for precooling for 30 minutes.

[0038] 4. Packaging and storage of lotus stems: Soak the cleaned lotus stems in 100-fold diluted microemulsion for 10 minutes, pick them up and dry them naturally; wrap them with plastic wrap and store them in an environment of -0.5℃ and 80% humidity.

[0039] Observe the lotus stems regularly and test the number of microorganisms, color value, hardness value, etc. of the lotus stems. The total number of bacteria in the lotus stems shall be tested according to GB4789.2-2022; the total number of molds and yeasts shall be tested according to GB4789.15-2016; the hardness of the lotus stems shall be tested by a texture analyzer equipped with a P / 2 probe; the color difference of the lotus stems shall be tested by a colorimeter, and the L, a*, and b* values ​​shall be recorded. According to the formula ΔE=[(L f -L i ) 2 +(a f -a i ) 2 +(b f -b i ) to calculate the color difference value. i 、a i , b i is the initial measured value of the sample, L f 、a f , b f These are the measured values ​​of samples at different experimental stages.

[0040] Example 2

[0041] A method for storing and preserving fruit and vegetable fresh-keeping film and lotus root stems, comprising the following steps:

[0042] 1. Preparation of microemulsion: (1) Weigh 2 parts of sorbic acid, 2 parts of carvacrol, 4 parts of caprylic acid glyceride, 8 parts of polyethylene glycol, and 32 parts of Tween 80, mix well to prepare a mixed solution; (2) Take 1.2 parts of acetic acid, dissolve it in 112 parts of water to prepare an acetic acid aqueous solution, add 2 parts of chitosan to obtain a chitosan-acetic acid aqueous solution; (3) While stirring the mixed solution in (1), add the chitosan-acetic acid aqueous solution in (2) drop by drop until the whole system changes from clear to turbid and then to clear. The microemulsion is obtained.

[0043] 2. Preparation of cling film: (1) Weigh 5 parts of lotus root starch and dissolve it in 100 parts of water, and gelatinize it in a 90°C water bath for 30 minutes; (2) Add 3 parts of glycerol and 60 parts of microemulsion, and stir to mix evenly; (3) Vacuum degas the obtained film liquid for 30 minutes, and the vacuum degree is 0.07 MPa; (4) Cast it on a clean glass plate, dry it in an incubator at 50°C for 6 hours, and then peel off the film to obtain the cling film.

[0044] 3. Cleaning of lotus stems: Clean the harvested lotus stems to remove sludge and residue, and remove the 2-3 cm long part at the bottom of the stems; immerse the cleaned lotus stems in 4°C cold water for precooling for 20 minutes.

[0045] 4. Packaging and storage of lotus stems: Soak the cleaned lotus stems in 200-fold diluted microemulsion for 8 minutes, pick them up and dry them naturally; wrap them with plastic wrap and store them in an environment of 4°C and 90% humidity.

[0046] Example 3

[0047] A method for storing and preserving fruit and vegetable fresh-keeping film and lotus root stems, comprising the following steps:

[0048] 1. Preparation of microemulsion: (1) Weigh 1 part of sorbic acid, 2 parts of carvacrol, 3 parts of caprylic acid glyceride, 8 parts of polyethylene glycol, and 24 parts of Tween 80, mix well to make a mixed solution; (2) Weigh 90 parts of water, excluding acetic acid and chitosan; (3) While stirring the mixed solution in (1), add the water in (2) drop by drop until the whole system changes from clear to turbid and then to clear. The microemulsion is obtained.

[0049] 2. Preparation of cling film: (1) Weigh 2 parts of lotus root starch and dissolve it in 80 parts of water, and gelatinize it in a water bath at 85°C for 30 minutes; (2) Add 1 part of glycerol and 20 parts of microemulsion, and stir to mix evenly; (3) Vacuum degas the obtained film liquid for 25 minutes, and the vacuum degree is 0.08MPa; (4) Cast it into a film on a clean glass plate, dry it in an incubator at 40°C for 6 hours, and then peel off the film to obtain the cling film.

[0050] 3. Cleaning of lotus stems: Clean the harvested lotus stems to remove sludge and residue, and remove the 2-3 cm long part at the bottom of the stems; immerse the cleaned lotus stems in 2°C cold water for precooling for 25 minutes.

[0051] 4. Packaging and storage of lotus stems: Soak the cleaned lotus stems in 150-fold diluted microemulsion for 12 minutes, pick them up and dry them naturally; wrap them with plastic wrap and store them in an environment of -1°C and 70% humidity.

[0052] Example 4

[0053] A method for storing and preserving lotus stems comprises the following steps:

[0054] 1. Preparation of microemulsion: (1) Weigh 1 part of sorbic acid, 1 part of carvacrol, 1 part of caprylic acid glyceride, 3 parts of polyethylene glycol, and 12 parts of Tween 80, mix well to prepare a mixed solution; (2) Take 0.4 parts of acetic acid, dissolve it in 41 parts of water to prepare an acetic acid aqueous solution, add 0.6 parts of chitosan to obtain a chitosan-acetic acid aqueous solution; (3) While stirring the mixed solution in (1), add the chitosan-acetic acid aqueous solution in (2) drop by drop until the whole system changes from clear to turbid and then to clear. The microemulsion is obtained.

[0055] 2. Cleaning of lotus stems: Clean the harvested lotus stems, remove the sludge residue and the 2-3 cm long part at the bottom of the stems; immerse the cleaned lotus stems in 0℃ cold water for precooling for 30 minutes.

[0056] 3. Packaging and storage of lotus stems: Soak the cleaned lotus stems in 100-fold diluted microemulsion for 10 minutes, pick them up and air dry them naturally; pack them in ordinary fresh-keeping bags with a thickness of 0.07 mm and store them in an environment of -0.5℃ and 80% humidity.

[0057] 4. Observe the lotus stems regularly and test the number of microorganisms, color value, hardness value, etc. of the lotus stems.

[0058] Example 5

[0059] A method for storing and preserving lotus stems comprises the following steps:

[0060] 1. Preparation of microemulsion: (1) Weigh 1 part of sorbic acid, 1 part of carvacrol, 1 part of caprylic acid glyceride, 3 parts of polyethylene glycol, and 12 parts of Tween 80, mix well to prepare a mixed solution; (2) Take 0.4 parts of acetic acid, dissolve it in 41 parts of water to prepare an acetic acid aqueous solution, add 0.6 parts of chitosan to obtain a chitosan-acetic acid aqueous solution; (3) While stirring the mixed solution in (1), add the chitosan-acetic acid aqueous solution in (2) drop by drop until the whole system changes from clear to turbid and then to clear. The microemulsion is obtained.

[0061] 2. Preparation of cling film: (1) Weigh 16 parts of lotus root starch and dissolve it in 100 parts of water, stirring to mix evenly; (2) Add 5 parts of glycerol and 25 parts of microemulsion, stirring to mix evenly; (3) Cast the obtained liquid into a film on a clean glass plate, dry it in an incubator at 40°C for 12 hours, and then peel off the film to obtain a cling film.

[0062] 3. Cleaning of lotus stems: Clean the harvested lotus stems to remove sludge and residue, and remove the 2-3 cm long part at the bottom of the stems; immerse the cleaned lotus stems in 0℃ ice water for precooling for 30 minutes.

[0063] 4. Packaging and storage of lotus stems: Wrap the cleaned lotus stems with plastic wrap and store them in an environment of 4°C and 80% humidity.

[0064] 5. Observe the lotus stems regularly and test the number of microorganisms, color value, hardness value, etc. of the lotus stems.

[0065] Comparative Example 1

[0066] 1. Prepare fresh-keeping solution: weigh 1g potassium sorbate and 2g ascorbic acid and dissolve them in 1L water. The concentration of potassium sorbate in the fresh-keeping solution is 0.1% and the concentration of ascorbic acid is 0.2%.

[0067] 2. Cleaning of lotus stems: Clean the harvested lotus stems to remove sludge and residue, and remove the 2-3 cm long part at the bottom of the stems; immerse the cleaned lotus stems in 0℃ ice water for precooling for 30 minutes.

[0068] 3. Soak the cleaned lotus stems in the above-mentioned preservative solution for 10 minutes, pick them up and dry them naturally; pack them in a fresh-keeping bag with a thickness of 0.07 mm and store them in an environment of -0.5℃ and 80% humidity.

[0069] 4. Observe the lotus stems regularly and test the number of microorganisms, color value, hardness value, etc. of the lotus stems.

[0070] Comparative Example 2

[0071] 1. Cleaning of lotus stems: Clean the harvested lotus stems, remove the sludge residue and the 2-3 cm long part at the bottom of the stems; immerse the cleaned lotus stems in 0℃ ice water for precooling for 30 minutes.

[0072] 2. Packaging and preservation of lotus stems: Place the cleaned lotus stems in a fresh-keeping bag with a thickness of 0.12 mm, vacuum pack them, and store them in an environment of 4°C and 80% humidity.

[0073] 3. Observe the lotus stems regularly and test the number of microorganisms, color value, hardness value, etc. of the lotus stems.

[0074] Comparative Example 3

[0075] 1. Cleaning of lotus stems: Clean the harvested lotus stems to remove sludge and residue, and remove the 2-3 cm long part at the bottom of the stems; immerse the cleaned lotus stems in 0℃ ice water for precooling for 30 minutes.

[0076] 2. Packaging and storage of lotus stems: Wrap the lotus stems with a 0.05 mm thick plastic wrap and store them in an environment of 4°C and 80% humidity.

[0077] 3. Observe the lotus stems regularly and test the number of microorganisms, color value, hardness value, etc. of the lotus stems.

[0078] In order to understand the performance of the microemulsion and preservative film prepared by the present invention, the following tests were also conducted: the minimum inhibitory concentration (MIC) of sorbic acid, carvacrol, potassium sorbate, and the microemulsion of Example 1 against Alternaria alternata, Fusarium solani, and Fusariumannulatum was tested by a two-fold dilution method, and the results are shown in Table 1;

[0079] The particle size, PDI value, and ζ potential of the microemulsion were tested using a Nano ZS nanoparticle size potential analyzer, and the results are shown in Table 2;

[0080] The thickness of the cling film is measured with a micrometer. The measurement method of tensile strength and elongation at break is as follows: the cling film is cut into strips of 50×20 mm in length and width, and then a tensile test is performed on a texture analyzer until it breaks. The effective tensile length is set to 30 mm and the tensile speed is set to 3 mm / s. Before the test, the film is balanced for 2 days in an environment of 25°C and 50% relative humidity. The tensile strength and elongation at break are calculated according to the formula: TS=F / (d×W), E / %=(L-L0) / L×100, where F is the maximum pressure when the film breaks, N; d is the thickness of the film; W is the width of the film; L is the extension length of the film, and L0 is the initial length of the film. The results are shown in Table 3.

[0081] The water permeability was measured with reference to the national standards "Test method for water vapor permeability of plastic film and sheet - Cup method" (GB1037) and "Test method for packaging materials - Water vapor permeability" (GB / T16928). The results are shown in Table 3.

[0082] The oxygen permeability was measured with reference to the national standards “Oxygen permeability test for packaging materials, plastic films and sheets” (GB / T19789) and “Gas permeability test method for plastic films and sheets - pressure difference method” (GB / T1038). The results are shown in Table 3.

[0083] The antibacterial activity of the membrane was determined by the shake flask method. 2 The film was sterilized by ultraviolet irradiation, cut into pieces and added to 10 mL of PDB culture medium. At the same time, 1 mL of 2×10 6CFU / mL of mold spore solution, and 1mL of sterile saline was added to the blank group. The bacterial solution was placed on a shaker at 28°C and 150r / min and cultured for 48h. The absorbance of the bacterial solution at 600nm was observed using an ELISA instrument. The antibacterial rate of the film (%) = [(A0-A i ) / A0]×100%, A0 is the absorbance of the bacterial solution in the blank control group, A i is the absorbance of the bacterial solution in the experimental group. The antibacterial results are shown in Table 3.

[0084] Table 1 Minimum inhibitory concentration (MIC) (g / kg) against Alternaria alternata, Fusarium solani, and Fusariumannulatum

[0085]

[0086] The minimum inhibitory concentrations of potassium sorbate, sorbic acid, and carvacrol against three major pathogens of lotus stems were tested respectively. The antibacterial effect of sorbic acid was better than that of potassium sorbate. Potassium sorbate is often used in production, mainly because sorbic acid has poor water solubility and is inconvenient to use directly, but it is still the sorbic acid molecule that exerts the antibacterial function. The antibacterial effect of directly using sorbic acid is better.

[0087] The combined use of sorbic acid and carvacrol has a better antibacterial effect on the three pathogenic bacteria than using them alone, and the use of the two together can achieve a synergistic effect. Sorbic acid and carvacrol are both insoluble in water. After the two are made into microemulsions, the disadvantages of their insolubility in water can be changed, the water solubility is increased by more than 10 times, and the antibacterial performance is stronger than that of sorbic acid and carvacrol monomers.

[0088] Table 2 Particle size, PDI value, zeta potential value of microemulsion of Examples 1-3

[0089] Particle size PDI value Zeta potential Example 1 Microemulsion 485nm 0.304 +25.62 Example 2 Microemulsion 524nm 0.410 +28.64 Example 3 Microemulsion 17nm 0.162 -1.76

[0090] When chitosan-acetic acid aqueous solution is used as the dispersed phase (Example 1, Example 2), the particle size of the microemulsion is about 500nm and is positively charged; when water is used as the dispersed phase (Example 3), the particle size is smaller, about 17nm, and is negatively charged. The microemulsions of the three examples are evenly dispersed and have high stability.

[0091] Table 3 Physical parameters and antibacterial properties of cling film

[0092]

[0093] The preservative film prepared by the invention is about 0.11 mm thick, has high transparency, and has certain tensile strength and barrier properties, which can block oxygen, thereby reducing the rate of oxidation and browning of lotus stems; at the same time, the preservative film also maintains certain air permeability, so that the lotus stems will not have anaerobic respiration. The antibacterial rate of the preservative film against three kinds of molds is more than 80%, and the antibacterial property is relatively strong.

[0094] from Figure 2-6 It can be seen that the lotus stem preservation method described in the present invention, through the combined use of microemulsion and preservative film (Example 1), can maintain a low number of microorganisms, good quality and appearance of the lotus stem during the storage period of 20 days, and the effect is better than that of a single microemulsion and preservative film. Compared with the preservative commonly used in actual production (combination of potassium sorbate and ascorbic acid) (Comparative Example 1), the present invention has better effects in reducing the number of microorganisms and reducing the color difference value, and the preservation effect is also better than the two storage methods commonly used in actual production (Comparative Example 2, Comparative Example 3). Although vacuum packaging (Comparative Example 2) can maintain a low color difference value of the lotus stem and maintain the bright white color of the lotus stem, the vacuum-packed lotus stem is prone to anaerobic respiration, and the lotus stem gradually produces odor, which reduces the hardness and collapses and softens the tissue. The lotus stem packaged with ordinary preservative film (Comparative Example 3) oxidizes and browns rapidly, and the microorganisms reproduce rapidly, so the lotus stem quickly loses its edible value. The combined use of microemulsion and plastic wrap (Example 1) can maintain the best quality of lotus stems. After 20 days of storage, the total number of bacteria in the lotus stems was 5.15log (CFU / g), the total number of molds and yeasts was 2.05log (CFU / g), the L value was 62.3, the a* value was 4.82, the b* value was 16.4, the color difference value was ΔE was 11.67, and the hardness value was 376.

[0095] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A fruit and vegetable fresh-keeping film, characterized in that: The fruit and vegetable cling film is prepared according to the following method: (1) weighing 2-5 parts of lotus root starch and dissolving it in 80-100 parts of water, and gelatinizing it in a water bath at 80-90° C. for 30-60 minutes; (2) adding 1-3 parts of glycerol and 20-60 parts of microemulsion, and stirring and mixing them evenly; (3) vacuum degassing the obtained film liquid for 20-30 minutes, and the vacuum degree is 0.07-0.1 MPa; (4) casting the degassed film liquid into a film, drying it in an incubator at 40-55° C. for 4-6 hours, and then peeling off the film to obtain the cling film; The microemulsion is prepared from the following components, calculated by weight: 1-2 parts of sorbic acid, 1-2 parts of carvacrol, 1-4 parts of caprylic decanoate, 3-8 parts of polyethylene glycol, 12-32 parts of Tween 80, 0-2 parts of chitosan, 0-1.2 parts of acetic acid and 41-112 parts of water.

2. A fruit and vegetable fresh-keeping film according to claim 1, characterized in that: The preparation method of the microemulsion comprises the following steps: (1) uniformly mixing Tween 80, sorbic acid, carvacrol, caprylic decanoate, and polyethylene glycol according to a weight ratio to form a mixed solution; (2) preparing an acetic acid aqueous solution, adding chitosan, and obtaining a chitosan-acetic acid aqueous solution; (3) Adding the chitosan-acetic acid aqueous solution obtained in step (2) dropwise to the mixed solution obtained in step (1) while stirring until the entire system changes from clear to turbid and then to clear again, thereby obtaining a microemulsion.

3. The use of a fruit and vegetable preservative film according to claim 1, characterized in that: Used for storage and preservation of lotus root stems.

4. A method for storing and preserving lotus stems, using the fruit and vegetable preservative film as claimed in claim 1 or 2, characterized in that: The steps include: (1) Cleaning and processing of lotus stems The harvested lotus stems are washed to remove the sludge residue and the bottom 2-3 cm long portion of the lotus stems is removed; the washed lotus stems are immersed in cold water for precooling; (2) Fresh-keeping packaging of lotus stems The lotus stems processed in step (1) are immersed in the diluted microemulsion, picked up and naturally dried; the lotus stems are wrapped with plastic wrap and stored.

5. The method for storing and preserving lotus stems according to claim 4, characterized in that: The temperature of the cold water is 0-4°C, and the pre-cooling time is 20-30 minutes.

6. The method for storing and preserving lotus stems according to claim 4, characterized in that: The dilution multiple of the microemulsion is 100-200 times, the ratio of lotus stem to the diluted microemulsion liquid during soaking is (1:2-4) g / mL, and the soaking time is 8-12 minutes.

7. The method for storing and preserving lotus stems according to claim 4, characterized in that: The storage conditions are a temperature of -1-4°C and a humidity of 70-90%.

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