Edible fresh-keeping agent capable of rapidly forming film, preparation method and application of edible fresh-keeping agent in fresh-keeping of mashed shrimps

Abstract

The invention discloses an edible preservative capable of rapidly forming a film. The preservative is a chitosan-sodium alginate-acetic acid bacteria fermentation liquor-calcium chloride composite film (CSAC); the weight ratio of the cane sugar to the sodium alginate to the chitosan to the distilled water in the mixed solution is (4-6): (0.5-2): (1-3): 100, and the weight ratio of the mixed solution of the cane sugar to the sodium alginate to the chitosan to the acetic bacteria fermentation supernatant is 10: (1-3). The fresh-keeping application result of the mashed shrimps shows that after CSAC treatment, the change of color and luster of the mashed shrimps can be effectively reduced, the MDA content and TVB-N increase in tissues are delayed, the pH of the mashed shrimps is reduced, the water-retaining property is improved, and the comprehensive fresh-keeping effect is optimal. According to the method disclosed by the invention, acetic acid bacteria fermentation liquor is innovatively introduced into a chitosan-sodium alginate composite membrane system, and in-situ rapid membrane formation on the surface of the mashed shrimp is realized by utilizing calcium ion crosslinking. The CSAC film realizes comprehensive and efficient regulation and control of smooth color, protein stability, lipid oxidation, pH and water binding capacity of prawns through a synergistic effect of biological activity of a physical barrier and acetic acid bacteria metabolite.

Description

Technical Field

[0001] The present invention relates to the technical field of food preservation, and in particular to a fast-film-forming edible preservative, a preparation method and application thereof in preserving shrimp slips. Background Art

[0002] Shrimp slips, a semi-fluid food made from fresh shrimp as the main raw material, are widely popular for their delicate taste and rich nutrition. However, shrimp slips are extremely susceptible to microbial contamination and oxidation during processing and storage, resulting in a decline in quality and a shortened shelf life. Traditional preservation methods mainly include refrigeration and the addition of chemical preservatives, but these methods have certain limitations. Although refrigeration can slow the growth rate of microorganisms, it cannot completely inhibit their growth and will also have a certain impact on the taste and nutritional content of shrimp slips. The use of chemical preservatives poses a food safety risk and may cause potential harm to human health. Therefore, the development of a safe, efficient and environmentally friendly shrimp slip preservation technology is of great practical significance.

[0003] In recent years, with the increasing awareness of food safety and environmental protection, edible cling film has received widespread attention as a new type of fresh-keeping material. Edible cling film is a film made from natural edible materials through a certain processing technology. It has good biocompatibility and degradability, is non-toxic and harmless to the human body, and can effectively block oxygen, moisture and microorganisms during the preservation process, thereby extending the shelf life of food. At present, the research on edible cling film mainly focuses on the selection of materials and the optimization of preparation technology. Common edible cling film materials include polysaccharides, proteins and lipids. However, the existing edible cling film still has some shortcomings in terms of film forming speed, mechanical properties and preservation effect, which limits its promotion in practical applications.

[0004] In the field of shrimp slip preservation, studies have shown that composite film (CSAC) has a good preservation effect on shrimp slips. Experiments were conducted on shrimp slips prepared from common fresh shrimp. The shrimp slips were treated with composite film (CSAC) and other preservatives, such as sodium chloride solution, melatonin solution, salicylic acid solution, calcium chloride solution, and distilled water. The shrimp slips were stored at 4°C and their color, malondialdehyde (MDA) content, volatile basic nitrogen (TVB-N) content, pH value, and moisture distribution were measured on the first, third, fifth, seventh, and tenth days. The results showed that shrimp slips treated with composite film (CSAC) effectively slowed color changes, delayed the increase in MDA and TVB-N content in the tissue, reduced pH value, and improved water retention. The overall preservation effect was superior to that achieved with other preservatives. This shows that composite film (CSAC) preservation of shrimp slips is an effective, feasible and safe preservation method, which can effectively extend the storage time of shrimp slips, maintain the sensory quality of shrimp slips and extend their shelf life.

[0005] However, existing composite films (CSAC) have several issues during their preparation, such as slow film formation and a need for improved mechanical properties. This has limited their effectiveness in shrimp slip preservation. Therefore, the present invention aims to develop a fast-forming edible cling film. By optimizing the preparation process and material formulation, this film formation speed is increased while maintaining good preservation effectiveness. This approach further enhances its application in shrimp slip preservation, providing a novel solution for the development of shrimp slip preservation technology. Summary of the Invention

[0006] The purpose of the present invention is to provide a fast film-forming edible preservative for shrimp slip preservation, which has fast film-forming and good preservation effect.

[0007] Furthermore, the present invention also provides a method for preparing the above-mentioned fast-film-forming edible preservative.

[0008] Furthermore, the present invention also provides an application method of the above-mentioned fast-film-forming edible preservative.

[0009] The technical solution adopted in the present invention is:

[0010] A fast-film-forming edible preservative,

[0011] The preservative is a mixture of a mixed solution of sucrose, sodium alginate and chitosan and a supernatant of acetic acid bacteria fermentation;

[0012] The weight ratio of sucrose, sodium alginate, chitosan and distilled water in the mixed solution of sucrose and sodium alginate is (4-6): (0.5-2): (1-3): 100, and the weight ratio of the mixed solution of sucrose, sodium alginate and chitosan to the acetic acid bacteria fermentation supernatant is 10: (1-3).

[0013] Wherein, the acetic acid bacteria fermentation supernatant is the supernatant obtained by acetic acid bacteria fermentation culture.

[0014] The acetic acid bacteria fermentation supernatant may be prepared by the following method:

[0015] The freeze-dried strain of acetic acid bacteria was inoculated into a sterilized liquid culture medium at an inoculum rate of 4%-6%, and cultured at 30°C at 100-140 r / min on a shaker for 24-48 hours. After fermentation, the culture medium was centrifuged, the precipitate was discarded, and the cell-free supernatant was obtained by filtration using a 0.22 μm microporous filter membrane. The supernatant was aliquoted and stored at 4°C.

[0016] Among them, the freeze-dried strain of acetic acid bacteria was inoculated into the sterilized liquid culture medium at a 5% inoculum, placed in a shaking incubator at 120 r / min and 30°C for 48 hours, centrifuged after fermentation, discarded the precipitate, and filtered through a 0.22 μm microporous filter membrane to obtain a cell-free supernatant, which was then packaged and stored at 4°C.

[0017] The culture medium is a liquid culture medium with a sucrose mass fraction of 4%-6%, a peptone mass fraction of 0.6%-0.8%, a yeast extract mass fraction of 1%-15%, a sodium citrate mass fraction of 0.1%-0.2%, a KHPO4 mass fraction of 0.1%-0.2%, a glacial acetic acid volume fraction of 0.5%-2%, and anhydrous ethanol volume fraction of 1%-3%.

[0018] The culture medium is a liquid culture medium with a sucrose mass fraction of 5%, a peptone mass fraction of 0.7%, a yeast extract mass fraction of 1.2%, a sodium citrate mass fraction of 0.15%, a KHPO4 mass fraction of 0.16%, a glacial acetic acid volume fraction of 1%, and anhydrous ethanol volume fraction of 2%.

[0019] Preferably, the weight ratio of sucrose, sodium alginate, chitosan and distilled water in the mixed solution of sucrose and sodium alginate is 5:1:2:100, and the weight ratio of the mixed solution of sucrose, sodium alginate and chitosan to the acetic acid bacteria fermentation supernatant is 5:1.

[0020] A method for preparing the above-mentioned fast film-forming edible preservative comprises the following steps:

[0021] 1) Inoculate the freeze-dried acetic acid bacteria strain into the sterilized liquid culture medium at a rate of 4%-6%, place it in a shaking incubator at 100-140 rpm and 30°C for 24-48 hours. After the fermentation is complete, the bacterial concentration of the fermentation liquid is 10 7 ~10 8 CFU / mL, the fermentation broth was centrifuged at 4000 r / min for 10 min, the precipitate was discarded, and the cell-free supernatant was obtained by filtration using a 0.22 μm microporous membrane and stored at 4 °C;

[0022] 2) Preparation of composite membrane solution: Heat distilled water to 70°C in a water bath, add sucrose and sodium alginate, stir until the sucrose and sodium alginate are completely dissolved, remove from the solution, cool to 60°C, add chitosan, and continue stirring until dissolved. After cooling to room temperature, add the acetic acid bacteria fermentation supernatant and stir evenly for later use. After dissolution is complete, coarsely filter through a 200-mesh filter cloth, divide into sterilized glass bottles, and store at 4°C.

[0023] Among them, the preparation process must comply with the GB 2760 food additive standard and the heavy metal content must meet the quality requirements of lead ≤1.0mg / kg and arsenic ≤0.5mg / kg.

[0024] An application method of a fast-film-forming edible preservative,

[0025] Step (1) chopping fresh shrimp into pieces to prepare shrimp paste, immersing the shrimp paste into a calcium chloride solution having a mass fraction of 0.5% to 2% and then quickly removing the shrimp paste;

[0026] In step (2), the mixture is immersed in the fast-film-forming edible preservative according to any one of claims 1 to 7 and quickly fished out.

[0027] Preferably, the application method of the fast film-forming edible preservative is:

[0028] Step (1) chopping fresh shrimp into pieces to prepare shrimp paste, immersing the shrimp paste into a 1% calcium chloride solution by mass fraction, and then quickly removing the shrimp paste;

[0029] In step (2), the mixture is immersed in the fast-film-forming edible preservative according to any one of claims 1 to 7 and quickly fished out.

[0030] Compared with the prior art, the fast-film-forming edible preservative of the present invention is a mixture of a mixed solution of sucrose, sodium alginate and chitosan and a supernatant of acetic acid bacteria fermentation; wherein the weight ratio of sucrose, sodium alginate, chitosan and distilled water in the mixed solution of sucrose and sodium alginate is (4-6): (0.5-2): (1-3): 100, and the weight ratio of the mixed solution of sucrose, sodium alginate and chitosan to the supernatant of acetic acid bacteria fermentation is 10: (1-3).

[0031] The application in shrimp slip preservation, comprehensive test results show that it has the following advantages:

[0032] (1) The chitosan-sodium alginate-acetic acid bacteria fermentation product composite film can effectively slow down the color change of shrimp slips after treatment, effectively delay the increase of MDA content and TVB-N in tissues, reduce the pH of shrimp slips, and improve the water retention of shrimp slips. The comprehensive preservation effect is better than that of other preservatives.

[0033] (2) The present invention extracts the fermentation broth of acetic acid bacteria and discards the acetic acid bacteria, thereby retaining the antibacterial substances and solving the problem of poor stability of acetic acid bacteria;

[0034] (3) By preparing biological preservatives, problems such as drug residues, environmental pollution, and drug resistance of microorganisms caused by the use of chemical preservatives in fruits and vegetables can be solved;

[0035] (4) The preservative can quickly form a thin film on the surface of the shrimp slips for cold preservation without adding a drying process, saving production time and cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The UV-visible absorption spectrum of the composite film formed by the preservative of the present invention;

[0037] Figure 2 This is a scanning electron microscope image of the composite film formed by the preservative of the present invention;

[0038] Figure 3 The effects of the experimental example and comparative ratio on the L*, a* and ΔE* of shrimp slips after treatment with preservatives;

[0039] Figure 4 This is a diagram showing the color change of shrimp slips after treatment with the experimental and comparative preservatives;

[0040] Figure 5 The TVB-N content of shrimp slips after treatment with preservatives in experimental example and comparative example;

[0041] Figure 6 The changes of MDA content in shrimp slips after treatment with preservatives for experimental example and comparative example;

[0042] Figure 7 The pH value changes of shrimp slips after treatment with the experimental example and comparative example preservatives. DETAILED DESCRIPTION

[0043] In order to better demonstrate the technical solutions and beneficial effects of the present invention, the technical solutions of the present invention are further described below in conjunction with embodiments, but this does not limit the scope of protection of the present invention.

[0044] The raw materials are purchased from the following sources:

[0045] Acetic acid bacteria, Jining Xiangyuan Biotechnology Co., Ltd.

[0046] Sodium alginate, Sinopharm Chemical Reagent Co., Ltd.

[0047] Chitosan, Sinopharm Chemical Reagent Co., Ltd.

[0048] Sucrose, Sinopharm Chemical Reagent Co., Ltd.

[0049] The remaining materials were commercially available.

[0050] Example 1

[0051] A method for preparing a fast-forming edible fresh-keeping film comprises the following steps:

[0052] 1) Preparation of acetic acid bacteria fermentation products: The freeze-dried acetic acid bacteria strain was inoculated into a liquid culture medium containing 5% sucrose, 0.7% peptone, 1.2% yeast extract, 0.15% sodium citrate, 0.16% KHPO4, 1% glacial acetic acid, and 2% anhydrous ethanol. The inoculum size was 5% and the culture medium was sterilized and incubated at 120 rpm and 30°C for 48 h. After the fermentation was completed, the fermentation broth (10 7 ~10 8 CFU / mL) were centrifuged at 4000 r / min for 10 min, the precipitate was discarded, and the cell-free supernatant was obtained by filtration using a 0.22 μm microporous membrane filter. The supernatant was aliquoted and stored at 4°C for a short period of time.

[0053] 2) Preparation of composite membrane solution: Add distilled water to a beaker, heat to 70°C in a water bath, add 5% sucrose by weight of the distilled water and 1% sodium alginate by weight of the distilled water, stir with a glass rod until the additives are completely dissolved, remove, cool to 60°C, add 2% chitosan by weight of distilled water, and continue stirring until dissolved; after cooling to room temperature, add 20% acetic acid bacteria fermentation supernatant by weight of distilled water, stir evenly and set aside; after dissolution is complete, coarse filter through 200 mesh filter cloth, divide into sterilized glass bottles, and store at 4°C. The preparation process must comply with the GB 2760 food additive standard and the heavy metal content must meet the quality requirements of lead ≤1.0 mg / kg and arsenic ≤0.5 mg / kg.

[0054] Example 2

[0055] 1) Preparation of acetic acid bacteria fermentation products: The freeze-dried acetic acid bacteria strain was inoculated into a liquid culture medium containing 4% sucrose, 0.6% peptone, 1.5% yeast extract, 0.2% sodium citrate, 0.1% KHPO4, 0.5% glacial acetic acid, and 1% anhydrous ethanol. The inoculum size was 5% and the culture medium was placed in a shaker at 100 rpm and 30°C for 48 h. After the fermentation was completed, the fermentation broth (10 7 ~10 8 CFU / mL) were centrifuged at 4000 r / min for 10 min, the precipitate was discarded, and the cell-free supernatant was obtained by filtration using a 0.22 μm microporous membrane filter. The supernatant was aliquoted and stored at 4°C for a short period of time.

[0056] 2) Preparation of composite membrane solution: Add distilled water to a beaker, heat to 70°C in a water bath, add 4% sucrose by weight of distilled water and 2% sodium alginate by weight of distilled water, stir with a glass rod until the additives are completely dissolved, remove, cool to 60°C, add 3% chitosan by weight of distilled water, and continue stirring until dissolved; after cooling to room temperature, add 30% acetic acid bacteria fermentation supernatant by weight of distilled water, stir evenly and set aside; after dissolution, filter through 200 mesh filter cloth, divide into sterilized glass bottles, and store at 4°C. The preparation process must comply with the GB 2760 food additive standard and the heavy metal content must meet the quality requirements of lead ≤1.0 mg / kg and arsenic ≤0.5 mg / kg.

[0057] Example 3

[0058] 1) Preparation of acetic acid bacteria fermentation products: The freeze-dried acetic acid bacteria strain was inoculated into a liquid culture medium containing 6% sucrose, 0.8% peptone, 1% yeast extract, 0.1% sodium citrate, 0.2% KHPO4, 2% glacial acetic acid, and 3% anhydrous ethanol. The inoculum size was 5% and the culture medium was placed in a shaker at 140 rpm and 30°C for 24 h. After the fermentation was completed, the fermentation broth (10 7 ~10 8 CFU / mL) were centrifuged at 4000 r / min for 10 min, the precipitate was discarded, and the cell-free supernatant was obtained by filtration using a 0.22 μm microporous membrane filter. The supernatant was aliquoted and stored at 4°C for a short period of time.

[0059] 2) Preparation of composite membrane solution: Add distilled water to a beaker, heat to 70°C in a water bath, add 4% sucrose by weight of the distilled water and 0.5% sodium alginate by weight of the distilled water, stir with a glass rod until the additives are completely dissolved, remove, cool to 60°C, add 1% chitosan by weight of distilled water, and continue stirring until dissolved; after cooling to room temperature, add 10% acetic acid bacteria fermentation supernatant by weight of distilled water, stir evenly and set aside; after dissolution, filter through 200 mesh filter cloth, divide into sterilized glass bottles, and store at 4°C. The preparation process must comply with the GB 2760 food additive standard and the heavy metal content must meet the quality requirements of lead ≤1.0 mg / kg and arsenic ≤0.5 mg / kg.

[0060] Chop the fresh shrimp into small pieces and prepare shrimp paste. Divide into small portions of equal weight and set aside.

[0061] Experimental Example 1

[0062] 1) Chopping fresh shrimp into pieces to prepare shrimp paste, immersing the mixture in a 1% calcium chloride ion solution and then quickly removing the mixture;

[0063] 2) Immerse the mixture in the fast-film-forming edible preservative prepared in Example 1 and quickly remove the mixture.

[0064] 3) The shrimp slips were placed in a fresh-keeping box and stored in a refrigerator at 4° C. for 10 days, and images of their appearance were taken.

[0065] Experimental Example 2

[0066] 1) Chopping fresh shrimp into pieces to prepare shrimp paste, immersing the mixture in a 1% calcium chloride ion solution and then quickly removing the mixture;

[0067] 2) Immerse the mixture in the fast-film-forming edible preservative prepared in Example 2 and quickly remove the mixture.

[0068] 3) The shrimp slips were placed in a fresh-keeping box and stored in a refrigerator at 4° C. for 10 days, and images of their appearance were taken.

[0069] Experimental Example 3

[0070] 1) Chopping fresh shrimp into pieces to prepare shrimp paste, immersing the mixture in a 1% calcium chloride ion solution and then quickly removing the mixture;

[0071] 2) Immerse the mixture in the fast-film-forming edible preservative prepared in Example 2 and quickly remove the mixture.

[0072] 3) The shrimp slips were placed in a fresh-keeping box and stored in a refrigerator at 4° C. for 10 days, and images of their appearance were taken.

[0073] Comparative Example 1

[0074] 1) Prepare 1.0% sodium chloride solution;

[0075] 2) Soak the shrimp in 1.0% sodium chloride solution and remove quickly;

[0076] 3) The shrimp slips were placed in a fresh-keeping box and stored in a refrigerator at 4° C. for 10 days, and images of their appearance were taken.

[0077] Comparative Example 2

[0078] This comparative example discloses a method for preserving shrimp paste with a melatonin solution, which comprises the following steps:

[0079] 1) Prepare 100 μmol / L melatonin solution;

[0080] 2) Soaking the shrimp slips in a melatonin solution;

[0081] 3) The shrimp slips were placed in a fresh-keeping box and stored in a refrigerator at 4° C. for 10 days, and images of their appearance were taken.

[0082] Comparative Example 3

[0083] This comparative example discloses a method for preserving shrimp paste with a 0.1 mmol / L salicylic acid solution, the specific steps being:

[0084] 1) Prepare 0.1 mmol / L salicylic acid solution;

[0085] 2) soaking the shrimp slips in a salicylic acid solution for treatment;

[0086] 3) The shrimp slips were placed in a fresh-keeping box and stored in a refrigerator at 4° C. for 10 days, and images of their appearance were taken.

[0087] Comparative Example 4

[0088] This comparative example discloses a method for preserving shrimp paste with a 1% calcium chloride solution, the specific steps being:

[0089] 1) Prepare 1% calcium chloride solution;

[0090] 2) Soaking the shrimp slips in 1% calcium chloride solution for treatment;

[0091] 3) Store the shrimp slips in a fresh-keeping box at 4°C for 10 days and take photos of their appearance.

[0092] Comparative Example 5

[0093] This comparative example discloses a method for preserving shrimp paste with distilled water, which comprises the following steps:

[0094] 1) Soak the shrimp slips in distilled water for processing;

[0095] 2) The shrimp slips were placed in a fresh-keeping box and stored in a refrigerator at 4°C for 10 days, and images of their appearance were taken.

[0096] Comparative Example 6

[0097] Preparation of plastic wrap:

[0098] Weigh an appropriate amount of sodium alginate in water, heat and stir at 80°C until it is completely dissolved to prepare a 2% sodium alginate solution, then add glycerol (based on the mass of sodium alginate, glycerol is added 25%), stir in a water bath at 80°C for 30 minutes, and perform ultrasonic degassing and defoaming. Using the solution casting method, pour the film-forming liquid into an 18cm×12cm mold and dry it in an oven at 50°C for 6 hours. After the film is dried, pour a calcium chloride solution with a concentration of (1% to 6%) on the surface of the film, cross-link for 3 minutes, clean the residual calcium chloride on the surface of the film with deionized water, and dry it at a temperature of 35°C and a humidity of 50% to form a film;

[0099] 1) Soak the shrimp slips and seal them with the above film;

[0100] 2) The shrimp slips were placed in a fresh-keeping box and stored in a refrigerator at 4°C for 10 days, and images of their appearance were taken.

[0101] Comparative Example 7

[0102] Preparation of plastic wrap:

[0103] Take a beaker and add distilled water. Heat it in a water bath to 70°C, then add 5% sucrose by weight of distilled water and 1% sodium alginate by weight of distilled water. Stir with a glass rod until the additives are completely dissolved. Then take out and cool to 60°C. Add 2% chitosan by weight of distilled water and continue stirring until dissolved. Pack into sterilized glass bottles and store at 4°C. The preparation process must comply with the GB 2760 food additive standard and the heavy metal content must meet the quality requirements of lead ≤1.0 mg / kg and arsenic ≤0.5 mg / kg.

[0104] The shrimp slips after preservation in the comparative example and experimental example were subjected to the following tests, and the appearance pictures taken were as follows: Figure 4 As shown, through Figure 4 It can be clearly seen that the color of the shrimp slips treated with CSAC on the 10th day is the smallest compared with the color on the 1st day, while the color of the shrimp slips treated with other preservatives on the 10th day is significantly different from that on the 1st day, changing from gray on the 1st day to orange-yellow on the 10th day.

[0105] Verification experiment:

[0106] 1 Structural characterization of composite fresh-keeping materials

[0107] 1.1 Determination of UV-visible absorption spectrum and infrared spectrum

[0108] The composite film (CSAC) prepared in Example 1 (the film peeled off from the surface of the shrimp slip in step 3 of Example 1) was dried and 0.5 cm 2 After the size is measured, the Fourier transform infrared spectrometer is used to adjust the test resolution to 4cm-1, and the composite film (CSAC) is scanned at 400-4000cm-1. The sampling point is cleaned before each test to ensure that there is no residual sample from the previous test. After the test is completed, the experimental data is recorded. UV-visible spectral determination: The prepared composite film (CSAC) is formulated into 1 mg / mL and scanned at full wavelength using a UV-visible spectrophotometer. After setting the instrument parameters, a blank substrate is used as a reference for baseline correction, and then the sample is placed in the light path and a full spectrum scan is performed in the wavelength range of 200-500nm. The curve of the change of absorption intensity with wavelength is recorded, such as Figure 1 The results show that CSAC has significant short-wave ultraviolet absorption capacity, likely due to the electronic transition response of the amino groups of chitosan and the carboxylic acid groups of sodium alginate to ultraviolet light. CSAC's low absorbance in the visible light region of 400-500nm indicates that it has good light transmittance, meeting the transparency requirements of packaging materials.

[0109] 1.2 SEM analysis

[0110] The composite film (CSAC) prepared in Example 1 (the film peeled off from the surface of the shrimp slip in step 3 of Example 1) was dried and 0.5 cm 2The surface morphology of the composite film (CSAC) was observed using a scanning electron microscope and recorded and analyzed. Figure 2 As shown in the figure, the CSAC surface is crack-free at different magnifications, demonstrating its high mechanical strength, effectively preventing breakage during transportation and handling, which could compromise the freshness of the shrimp. Furthermore, the rough structure facilitates close adhesion to the shrimp slip surface, forming a stable protective barrier that blocks external contaminants and maintains the shrimp slip's quality. Overall, the porous, rough, and uniform structure of the composite membrane provides a combination of moisturizing, antibacterial, and antioxidant properties for shrimp slip preservation, effectively extending its shelf life and maintaining its quality.

[0111] 1.3 Determination of color difference

[0112] The surface color difference of the shrimp slips in the experimental and comparative examples was measured using a colorimeter. The color change of the shrimp slips was represented by L*, a*, b*, and ΔE* values. ΔE* was calculated using the following formula: L1*, a1*, and b1* represent the values ​​measured on the first day.

[0113] ΔE*=√((L*-L1*) 2 +(a*-a1*) 2 +(b*-b1*) 2 )

[0114] The results are as follows Figure 3 As shown, color difference is an important indicator of food spoilage. During storage, enzymatic reactions within shrimp cause polyphenol oxidase to convert colorless monophenols into bisphenols, especially under aerobic conditions. These bisphenols then evolve into highly reactive quinones, which readily bind to proteins or amino acids, leading to the formation of melanin. This process causes shrimp to appear black and red. The growth and reproduction of certain microorganisms can produce pigments, causing changes in the appearance of food color. In addition to the effects of microbial pigment production, chemical changes in foods such as lipids and proteins can also cause changes in the appearance of food color. The spoilage of shrimp slips is often accompanied by a decrease in the L* value (reduced brightness). L* represents the brightness of the black and white surfaces of shrimp slips, ranging from 0 (pure black) to 100 (pure white). L* monitors whether the food color has shifted in brightness due to factors such as aging and oxidation.

[0115] 1.4 Determination of volatile basic nitrogen

[0116] According to the microdiffusion method specified in GB 5009.228-2016 "National Food Safety Standard Determination of Volatile Basic Nitrogen in Food", the volatile basic nitrogen (TVB-N) of the experimental and comparative shrimp slips was tested. The results are as follows: Figure 5As shown in the data, the TVB-N content in shrimp slips treated with all preservatives showed an upward trend with increasing storage time. The TVB-N content in shrimp slips treated with CSAC on the tenth day was significantly lower (P<0.05) than that in shrimp slips treated with other preservatives, at 5.68 mg / 100 g. Since TVB-N content is positively correlated with the degree of spoilage in shrimp slips, the data comparison shows that the TVB-N content in shrimp slips treated with CSAC is significantly lower than that in the groups treated with other preservatives, indicating that the shrimp slips treated with the CSAC composite film have the lowest degree of spoilage and that CSAC has an effective preservation ability for shrimp slips.

[0117] 1.5 Determination of malondialdehyde

[0118] According to the instructions of the malondialdehyde determination kit purchased from Nanjing Jiancheng Bioengineering Institute, malondialdehyde (MDA) in the shrimp slips of the experimental example and the comparative example was determined. The results are as follows Figure 6 As shown in the figure, the MDA content in shrimp slips showed an increasing trend with increasing storage time. Among all preservatives, the increase in MDA content in shrimp slip tissue in the CSAC treatment group was significantly less than that in the other treatment groups. Among the other treatment groups, the increase in MDA content in shrimp slip tissue in the salicylic acid and melatonin treatment groups was less than that in the sodium chloride and calcium chloride treatment groups. However, the increase in MDA content in shrimp slip tissue in all of the above treatment groups was less than that in the distilled water treatment group, indicating that all of the above treatment groups have a certain effect in delaying the increase in MDA content in shrimp slip tissue, and CSAC is the most effective in delaying the increase in MDA content in shrimp slip tissue.

[0119] 1.6PH determination

[0120] According to GB 5009.237-2016 "Determination of pH value of food in national food safety standard", the experimental and comparative shrimp slips were tested. The results are as follows: Figure 7 As shown in Figure 2, during shrimp slip storage, nutrients are broken down or other products are produced by microorganisms, enzymes, or various reactions, altering the pH of the shrimp slip. Measuring the pH of shrimp slips is an important indicator of their quality. Studies have shown that the pH increase after shrimp slips spoil is due to the protein content of shrimp slips. Under the action of endogenous enzymes and microorganisms, the protein is broken down into a series of alkaline compounds, such as trimethylamine, histamine, and indole. This leads to a continuous increase in pH across all treatment groups. The degree of pH increase is related to the degree of spoilage.

[0121] Studies have shown that the preservative film formed by the preservative of the present invention has good light transmittance, can absorb short-wave ultraviolet rays, has good mechanical strength, and has a good preservative effect on shrimp slips. By comparing the color of shrimp slips treated with the preservative to form a composite film, the TVB-N content in the tissue, the MDA content in the tissue, the pH of the shrimp slips, and the changes in the moisture distribution of the shrimp slips, the preservative effect of the composite film is better than that of other experimental groups. Compared with traditional preservatives, the composite film formed by the preservative of the present invention has the significant advantage of combining acetic acid bacteria fermentation products with chitosan-sodium alginate base film to construct a triple synergistic preservation system. Breaking through the traditional single preservation mechanism, the antibacterial properties of chitosan, the film-forming properties of sodium alginate, and the antioxidant properties of acetic acid bacteria products achieve multi-target preservation, forming a dual protection of physical barriers and bioactive ingredients. It can stabilize the color of shrimp slips, reduce protein decomposition and fat oxidation in shrimp slips, improve the water retention of shrimp slips, and extend the shelf life of shrimp slips.

[0122] To explore the preservation effect of cling film prepared from acetic acid bacteria metabolites on shrimp slips, shrimp slips prepared from common fresh shrimp were used as test material. This method involves forming a thin film on the surface of shrimp slips by preparing a composite film of acetic acid bacteria metabolites with chitosan, sodium alginate, and calcium chloride. The shrimp slips were then treated with sodium chloride solution, melatonin solution, salicylic acid solution, calcium chloride solution, and distilled water and stored at 4°C. The preparation of the chitosan-sodium alginate-acetic acid bacteria product composite film (CSAC) and its preservation effect on shrimp slips were analyzed by comparing the color, MDA, TVB-N, pH, and moisture distribution of the shrimp slips on days 1, 3, 5, 7, and 10. The physical properties of the CSAC were analyzed by SEM analysis, UV-visible absorption spectroscopy, and infrared absorption spectroscopy. Comprehensive test results show that CSAC-treated shrimp slips can effectively slow color changes, delay increases in MDA content and TVB-N in tissue, lower the pH of shrimp slips, and improve their water retention. The overall preservation effect is superior to that of other preservatives. Therefore, preserving shrimp slips with a chitosan-sodium alginate-acetic acid bacteria product-calcium chloride composite film (CSAC) is an effective, feasible, and safe method for preserving shrimp slips, effectively extending their storage time, maintaining their sensory quality, and extending their shelf life.

Claims

1. A fast film-forming edible preservative, characterized by: The preservative is a mixture of a mixed solution of sucrose, sodium alginate and chitosan and a supernatant of acetic acid bacteria fermentation; The weight ratio of sucrose, sodium alginate, chitosan and distilled water in the mixed solution of sucrose and sodium alginate is (4-6): (0.5-2): (1-3): 100, and the weight ratio of the mixed solution of sucrose, sodium alginate and chitosan to the acetic acid bacteria fermentation supernatant is 10: (1-3).

2. The fast film-forming edible preservative according to claim 1, characterized in that: The acetic acid bacteria fermentation supernatant is a supernatant obtained by acetic acid bacteria fermentation culture.

3. The fast film-forming edible preservative according to claim 2, characterized in that: The acetic acid bacteria fermentation supernatant may be prepared by the following method: The freeze-dried strain of acetic acid bacteria was inoculated into a sterilized liquid culture medium at an inoculum rate of 4%-6%, and cultured at 30°C at 100-140 r / min on a shaker for 24-48 hours. After fermentation, the culture medium was centrifuged, the precipitate was discarded, and the cell-free supernatant was obtained by filtration using a 0.22 μm microporous filter membrane. The supernatant was aliquoted and stored at 4°C.

4. The fast film-forming edible preservative according to claim 3, characterized in that: The freeze-dried strain of acetic acid bacteria was inoculated into the sterilized liquid culture medium at a 5% inoculum size and cultured at 30°C in a shaking incubator at 120 r / min for 48 h. After fermentation, the culture was centrifuged, the precipitate was discarded, and the cell-free supernatant was obtained by filtration using a 0.22 μm microporous filter membrane. The supernatant was aliquoted and stored at 4°C.

5. The fast film-forming edible preservative according to claim 3 or 4, characterized in that: The culture medium is a liquid culture medium with a sucrose mass fraction of 4%-6%, a peptone mass fraction of 0.6%-0.8%, a yeast extract mass fraction of 1%-1.5%, a sodium citrate mass fraction of 0.1%-0.2%, a KHPO4 mass fraction of 0.1%-0.2%, a glacial acetic acid volume fraction of 0.5%-2%, and anhydrous ethanol volume fraction of 1%-3%.

6. The fast film-forming edible preservative according to claim 5, characterized in that: The culture medium is a liquid culture medium with a sucrose mass fraction of 5%, a peptone mass fraction of 0.7%, a yeast extract mass fraction of 1.2%, a sodium citrate mass fraction of 0.15%, a KHPO4 mass fraction of 0.16%, a glacial acetic acid volume fraction of 1%, and anhydrous ethanol volume fraction of 2%.

7. The fast film-forming edible preservative according to claim 1, characterized in that: The weight ratio of sucrose, sodium alginate, chitosan and distilled water in the mixed solution of sucrose and sodium alginate is 5:1:2:100, and the weight ratio of the mixed solution of sucrose, sodium alginate and chitosan to the acetic acid bacteria fermentation supernatant is 5:

1.

8. A method for preparing the fast film-forming edible preservative according to any one of claims 1 to 7, characterized in that The following steps are involved: 1) Inoculate the freeze-dried acetic acid bacteria strain into the sterilized liquid culture medium at a rate of 4%-6%, place it in a shaking incubator at 100-140 rpm and 30°C for 24-48 hours. After the fermentation is complete, the bacterial concentration of the fermentation liquid is 10 7 ~10 8 CFU / mL, the fermentation broth was centrifuged at 4000 r / min for 10 min, the precipitate was discarded, and the cell-free supernatant was obtained by filtration using a 0.22 μm microporous membrane and stored at 4 °C; 2) Preparation of composite membrane solution: Heat distilled water to 70°C in a water bath, add sucrose and sodium alginate, stir until the sucrose and sodium alginate are completely dissolved, remove, cool to 60°C, add, and continue stirring until dissolved; after cooling to room temperature, add acetic acid bacteria fermentation supernatant, stir evenly, and set aside; after dissolution, coarsely filter through 200-mesh filter cloth, divide into sterilized glass bottles, and store at 4°C.

9. A method for applying a fast-film-forming edible preservative, characterized in that: Step (1) chopping fresh shrimp into pieces to prepare shrimp paste, immersing the mixture in a calcium chloride solution having a mass fraction of 0.5% to 2% and then quickly removing the mixture; In step (2), the mixture is immersed in the fast-film-forming edible preservative according to any one of claims 1 to 7 and quickly fished out.

10. A method for applying a fast-film-forming edible preservative, characterized in that: Step (1) chopping fresh shrimp into pieces to prepare shrimp paste, immersing the shrimp paste into a 1% calcium chloride solution by mass fraction, and then quickly removing the shrimp paste; In step (2), the mixture is immersed in the fast-film-forming edible preservative according to any one of claims 1 to 7 and quickly fished out.

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