Eutectic composite film, preparation method thereof and application of eutectic composite film in pork preservation

Abstract

The invention discloses a eutectic composite film as well as a preparation method and application thereof in pork preservation, and belongs to the technical field of food preservation. The preparation method of the hesperetin eutectic composite membrane comprises the following steps: (1) uniformly mixing pretreated bagasse powder with sodium alginate, whey protein, lotus root starch and glycerol, and adding cinnamon essential oil to obtain an SLB mixed membrane solution; and (2) mixing the SLB mixed film liquid with a preservative, carrying out ultrasonic treatment, and drying and shaping to obtain the eutectic composite film. The eutectic composite film is prepared by taking SLB as a film forming substrate, adding glycerol as a plasticizer and taking hesperetin, berberine hydrochloride, a physical mixture of hesperetin and berberine hydrochloride or hesperetin-berberine hydrochloride pharmaceutical eutectic as a preservative. The eutectic composite film is proved to be capable of remarkably inhibiting the pork from decaying under the condition of normal temperature and prolonging the shelf life of the pork.

Description

Technical Field

[0001] The present invention relates to the technical field of food preservation, and particularly relates to a eutectic composite film, a preparation method thereof, and an application thereof in pork preservation. Background Art

[0002] With the rapid development of fresh food supermarkets and the continuous improvement of the cold chain logistics system, chilled fresh pork has gradually become the first choice of consumers due to its high quality, showing broad market prospects. Pork is widely popular because of its unique flavor and high nutritional value, and is rich in vitamin B and abundant fatty acids. Pork is prone to microbial contamination and spoilage during storage, transportation, and sales, which poses a major challenge to the food industry. Inhibiting microorganisms is crucial for preserving pork and ensuring its safety. Therefore, the development of environmentally friendly and sustainable food packaging films is of great significance in the food packaging industry.

[0003] As an active packaging material, antibacterial films are a favorable choice for food packaging and can extend the shelf life of food. However, existing food active packaging films are usually composed of a single component, which results in their relatively single performance and makes it difficult to meet the needs of complex food preservation. Sodium alginate (SA), as a kind of natural polysaccharide biodegradable material, has the advantages of long polymer chain length, easy availability, and non-toxicity, and is a green candidate material for manufacturing food packaging films. Lotus root starch (LRS) is a natural, multifunctional, and environmentally friendly starch, and its unique physical and chemical properties make it one of the ideal raw materials for the development of food packaging films. Sugarcane bagasse (SCB) is the fiber residue remaining after sugarcane is squeezed for sugar. Sugarcane bagasse fibers can be compounded with natural polymers (such as starch and chitosan) to make food packaging materials with good mechanical properties and barrier properties.

[0004] Hesperetin (Hes) is a natural flavonoid compound and a powerful antioxidant. Although hesperetin is a valuable and safe biopreservative, due to its hydrophobicity, it sometimes precipitates and is not easily dispersed in the polymer matrix. Research shows that using eutectic technology to prepare hesperetin into a drug eutectic is an effective method to improve its hydrophobicity. Berberine hydrochloride (Ber) is an isoquinoline alkaloid with strong antibacterial activity and few side effects, and is often used as an antibacterial agent for food preservation. However, there is no report on preparing a composite film with hesperetin or berberine hydrochloride. Summary of the Invention

[0005] The object of the present invention is to provide a eutectic composite film, a preparation method thereof, and an application in pork preservation, so as to solve the problems existing in the above-mentioned prior art. The present invention uses SLB as a film-forming substrate, adds glycerol as a plasticizer, and uses hesperetin, berberine hydrochloride, a physical mixture of hesperetin + berberine hydrochloride, or a eutectic of hesperetin-berberine hydrochloride as a preservative to prepare a eutectic composite film. It has been verified that the eutectic composite film can significantly inhibit pork spoilage and extend the shelf life of pork at room temperature.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The present invention provides a preparation method of a eutectic composite film, comprising the following steps:

[0008] (1) Mix the pretreated bagasse powder evenly with sodium alginate, whey protein, lotus root starch, and glycerol, and add cinnamon essential oil to obtain an SLB mixed film solution;

[0009] (2) Mix the SLB mixed film solution with a preservative, perform ultrasonic treatment, and then dry and shape it to obtain the eutectic composite film;

[0010] The preservative is any one of hesperetin, berberine hydrochloride, a physical mixture of hesperetin + berberine hydrochloride, and a eutectic of hesperetin-berberine hydrochloride.

[0011] Further, the pretreatment method of the bagasse powder is to perform water bath treatment and alkali heat treatment on the bagasse, and then dry and crush it;

[0012] The temperature of the water bath treatment is 65 - 75 °C, and the time is 1.5 - 3 h;

[0013] The alkali heat treatment is to mix the bagasse after water bath treatment with 4% sodium hydroxide according to a mass ratio of 1:18 - 22 and then heat-treat it; the temperature of the alkali heat treatment is 65 - 75 °C, and the time is 1.5 - 3 h.

[0014] Further, the mass ratio of the pretreated bagasse powder, sodium alginate, whey protein, lotus root starch, glycerol, and cinnamon essential oil is 1 - 1.5:3 - 5:1 - 3:2 - 4:1 - 3:0.05 - 0.2.

[0015] Further, the physical mixture of hesperetin + berberine hydrochloride is obtained by mixing hesperetin and berberine hydrochloride according to a molar ratio of 1:1.

[0016] Further, the eutectic of hesperetin-berberine hydrochloride is the eutectic of hesperetin-berberine hydrochloride disclosed in CN 115650941 A.

[0017] Further, the volume ratio of the SLB hybrid film solution to the preservative is 100 - 200:1 - 2.

[0018] Further, the concentration of the preservative is 0.03 - 0.05 mol / L.

[0019] Further, in step (1), the temperature during mixing is 65 - 75 °C, the rotation speed is 1500 - 2500 r / min, and the time is 25 - 40 min.

[0020] Further, in step (2), the power of the ultrasonic treatment is 200 W, the frequency is 25 kHz, and the time is 15 - 25 min.

[0021] The present invention also provides a eutectic composite film prepared by the above preparation method.

[0022] The present invention also provides the application of the above eutectic composite film in pork preservation, and the pork preservation includes inhibiting the weight loss rate, microbial growth, lipid oxidation and pH value increase during pork storage, and extending the shelf life of pork.

[0023] The present invention discloses the following technical effects:

[0024] The present invention adopts a simple and convenient co - blending film - forming strategy combined with eutectic technology to successfully prepare a novel eutectic composite film for meat preservation with stable structure. The eutectic composite film uses SLB as the film - forming substrate, adds glycerol as a plasticizer, and is prepared with hesperetin, berberine hydrochloride, a physical mixture of hesperetin + berberine hydrochloride or a drug eutectic of hesperetin - berberine hydrochloride as the preservative. It has been verified that using the eutectic composite film of the present invention to package pork can significantly inhibit the weight loss rate, microbial growth, lipid oxidation and pH value increase during pork storage at room temperature, and can extend the shelf life of pork up to 6 days at most.

[0025] The present invention adopts a simple and convenient co - blending film - forming strategy combined with eutectic technology to successfully prepare a novel eutectic composite film for meat preservation with stable structure, which has high stability, low cost, can realize the long - term and continuous release of the biological preservative, not only maintains the color of pork but also inhibits its spoilage when used for pork preservation, and further extends the shelf life of pork, having broad commercial prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the following - described drawings are only some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0027] Figure 1 Transparency detection results of SLB, SLB / Hes, SLB / Ber, SLB / Hes+Ber, and SLB / Hes-Ber composite films;

[0028] Figure 2 Surface and cross-sectional views of SLB, SLB / Hes, SLB / Ber, SLB / Hes+Ber, and SLB / Hes-Ber composite films;

[0029] Figure 3 X-ray diffraction patterns of SLB, SLB / Hes, SLB / Ber, SLB / Hes+Ber, and SLB / Hes-Ber composite films;

[0030] Figure 4 DSC curves of SLB, SLB / Hes, SLB / Ber, SLB / Hes+Ber, and SLB / Hes-Ber composite films;

[0031] Figure 5 Infrared absorption spectra of SLB, SLB / Hes, SLB / Ber, SLB / Hes+Ber, and SLB / Hes-Ber composite films;

[0032] Figure 6 Operation diagrams for preserving pork using different composite films;

[0033] Figure 7 Appearance changes of pork in different composite film treatment groups during storage;

[0034] Figure 8 Weight loss rate changes of pork in different composite film treatment groups during storage;

[0035] Figure 9 pH changes of pork in different composite film treatment groups during storage;

[0036] Figure 10 Total viable count (TVC) changes of pork in different composite film treatment groups during storage;

[0037] Figure 11 TBARS value changes of pork in different composite film treatment groups during storage. Detailed implementation manners

[0038] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0039] It should be understood that the terms used in the present invention are only for describing particular embodiments and are not intended to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0040] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0041] Without departing from the scope or spirit of the present invention, various improvements and variations can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the present invention specification are obvious to those skilled in the art. The present invention specification and examples are merely exemplary.

[0042] Regarding the use of "comprising", "including", "having", "containing", etc. herein, they are all open-ended terms, meaning including but not limited to.

[0043] Example 1 Preparation of Eutectic Composite Film

[0044] 1. Preparation of Bagasse Powder

[0045] Peel and wash the bagasse, add distilled water until it covers the surface of the bagasse, heat in a water bath at 70 °C for 2 h, and continuously stir during this period. After heating, rinse the attachments on the surface of the bagasse with distilled water, drain the water, add a 4% sodium hydroxide solution according to the mass ratio of bagasse: sodium hydroxide = 1:20, magnetically stir at 70 °C for 2 h, and then repeatedly rinse with distilled water until the rinse liquid is transparent and the solution pH is lower than 8. Dry the bagasse at 60 °C, pulverize it, and sieve it to obtain bagasse powder with a particle size less than 200 mesh.

[0046] 2. Preparation of Film-forming Solution and Eutectic Composite Film

[0047] Disperse 4 g of sodium alginate, 1.2 g of bagasse powder, 2 g of whey protein, 3 g of lotus root starch and 2 g of glycerol in 150 mL of distilled water. Place the membrane solution in a thermostatic magnetic water bath and stir it at 70 °C and 2000 r / min for 30 min until it is evenly mixed. Then cool the membrane solution to room temperature and filter it through a 20-mesh sieve to remove insoluble powder masses. Add 100 mg of cinnamon essential oil to the filtrate, stir evenly, and obtain the SLB mixed membrane solution for standby.

[0048] Mix 150 mL of the SLB mixed membrane solution with 1.17 mL of hesperetin (Hes), berberine hydrochloride (Ber), physical mixture of hesperetin + berberine hydrochloride (Hes+Ber), and hesperetin-berberine hydrochloride drug co-crystal (Hes-Ber) with a molar concentration of 0.04 mol / L respectively. After stirring evenly, perform ultrasonic treatment (200 W, 25 kHz) for 20 min to finally obtain the composite membrane solution. Pour the SLB mixed membrane solution and the composite membrane solution onto a glass plate coated with glycerol respectively to make their thickness uniform, and place them in a drying oven at 55 °C for 5 h to form films. Name the above-prepared composite membranes as SLB, SLB / Hes, SLB / Ber, SLB / Hes+Ber, and SLB / Hes-Ber respectively.

[0049] The preparation method of the above physical mixture of hesperetin + berberine hydrochloride (Hes+Ber) is as follows: Mix hesperetin and berberine hydrochloride according to a molar ratio of 1:1, add DMSO solution to make it completely dissolved, and obtain.

[0050] The above hesperetin-berberine hydrochloride drug co-crystal (Hes-Ber) is the hesperetin-berberine hydrochloride drug co-crystal disclosed in CN 115650941 A.

[0051] Performance verification of the co-crystal composite membrane in Example 2

[0052] Verify the structure and performance of the composite membranes SLB / Hes, SLB / Ber, SLB / Hes+Ber, and SLB / Hes-Ber prepared in Example 1. The specific process is as follows:

[0053] 1. Characterization of the co-crystal composite membrane

[0054] 1.1 X-ray powder diffraction analysis

[0055] The SLB, SLB / Hes, SLB / Ber, SLB / Hes+Ber, and SLB / Hes-Ber composite films were tested on a Rigaku MiniFlex600 diffractometer using Cu target Kα rays as the light source, with a voltage of 40 kV, a current of 15 mA, a scanning range set at 3 - 70° (2θ), a scanning speed of 10° / min, and a step size of 0.02° (2θ). The obtained data were processed using the software Origin 2021.

[0056] 1.2 Thermal analysis

[0057] Differential scanning calorimetry (DSC): The SLB, SLB / Hes, SLB / Ber, SLB / Hes+Ber, and SLB / Hes-Ber composite films were tested using a NETZSCH STA449 F5 synchronous thermal analyzer with nitrogen as the protective gas, a heating temperature range of 26 - 600 °C, and a heating rate of 10 °C / min.

[0058] 1.3 Infrared spectroscopy analysis

[0059] The SLB, SLB / Hes, SLB / Ber, SLB / Hes+Ber, and SLB / Hes-Ber composite films were tested using a Spectrum Two Fourier transform infrared spectrometer. The composite films were first dried in a forced-air oven at 40 °C for 4 h, then an appropriate amount was taken and thoroughly ground and mixed with dried potassium bromide under an infrared lamp. An appropriate amount was placed in a mold, and the sample was pressed into a transparent thin film, which was then put into the infrared spectrometer for scanning. The scanning range was 4000 - 500 cm -1 , with an average of 1 scan, and a spectral resolution of 4 cm -1 .

[0060] 1.4 Morphology of the composite films

[0061] The morphology and transparency of each composite film were recorded using a camera. The surface and cross-sectional microstructures of the SLB, SLB / Hes, SLB / Ber, SLB / Hes+Ber, and SLB / Hes-Ber composite films were observed using a scanning electron microscope. For the cross-section, the thin film was frozen in liquid nitrogen and quickly broken to ensure a clear and complete cross-section, and then a gold layer was coated using an ion sputtering coater.

[0062] 2. Preservation ability of the composite films for pork

[0063] Select fresh pork tenderloin that can be purchased in local supermarkets, remove the fat and connective tissue exposed to the external environment, and cut it into 5g cubes of the same size. Randomly divide it into a control group, an SLB group, an SLB / Hes group, an SLB / Ber group, an SLB / Hes+Ber group, and an SLB / Hes-Ber group. Then, place the pork in a sterilized glass jar, cover the bottle mouth with the prepared eutectic composite film, and wrap it tightly. The group without covering the composite film on the bottle mouth is the control group. Store the pork at room temperature for 12 days, and randomly select 3 pieces of pork from each group for index determination during the storage period.

[0064] 2.1 Appearance changes

[0065] Recorded the appearance of the pork with a digital camera every other day.

[0066] 2.2 Weight loss rate (WLR)

[0067] Within 0 - 12 days, the weight loss rate of the pork during storage was measured by the gravimetric method. The calculation formula for the weight loss rate is as follows:

[0068]

[0069] Among them, W0 is the initial weight of the pork, g; W S is the weight of the pork after preservation and storage for multiple days, g.

[0070] 2.3 pH

[0071] When taking out the pork samples at different storage days, weigh one piece (5g), add 50 mL of distilled water and stir evenly, soak for 30 min, then centrifuge at 3000 r for 10 min, and take the supernatant to measure the pH with a pH meter.

[0072] 2.4 Determination of total bacterial count

[0073] When taking out the pork samples at different storage days, aseptically transfer them to a stomacher bag containing 50 ml of sterile PBS solution, homogenize them, and take the supernatant. Dilute the supernatant to 10 -3 times, then take 200 μL and spread it on the solid LB broth medium. Set 3 parallels for each group, place it in a refrigerator at 4 - 8 °C for infiltration for 2 h, and continuously shake and culture at 37 °C for 24 h, then perform colony counting and statistical analysis of the results.

[0074] 2.5 Determination of thiobarbituric acid value (TBARS)

[0075] Add 5 g of ground pork to 50 mL of distilled water, stir to homogenize, then add trichloroacetic acid with a concentration of 7.5% containing 0.1% EDTA (disodium ethylenediaminetetraacetate). After homogenization, filter through filter paper, aspirate 5 mL of the filtrate, and add 5 mL of 0.02 mol / L thiobarbituric acid solution. Boil in a water bath for 20 min. After cooling to room temperature, aspirate 3 mL of the supernatant and place it in a cuvette to measure the absorbance value at 532 nm. The TBARS value is expressed as the mass of malondialdehyde in the sample per unit mass, mg MDA / kg, and is calculated according to the following formula:

[0076] TBARS of the pork sample = (OD 532nm / W) × 9.24

[0077] where OD 532nm is the absorbance value of each sample solution, W is the weight (g) of each pork sample, and 9.24 is a constant.

[0078] 3. Results

[0079] 3.1 Preparation of eutectic composite membranes

[0080] Figure 1 are the appearance diagrams of each composite membrane. It can be seen that compared with the SLB membrane, the SLB / Hes, SLB / Ber, SLB / Hes+Ber, and SLB / Hes-Ber composite membranes show an obvious trend of darkening and yellowing. This color change is attributed to the inherent color of the added Ber. However, the composite film still maintains a high degree of transparency during the entire color change process, laying a foundation for practical applications.

[0081] 3.2 Morphology of eutectic composite membranes

[0082] Figure 2 are the SEM diagrams of each composite membrane. It can be seen that the surface of the SLB substrate membrane is relatively rough, and cracks are found in the cross-section. The surfaces of the SLB / Hes, SLB / Ber, SLB / Hes+Ber, and SLB / Hes-Ber composite membranes are all smooth, uniform, and continuous, indicating good compatibility between Hes, Ber, Hes+Ber, Hes-Ber, and SLB. Small particles are evenly distributed in the cross-sections of SLB / Hes, SLB / Ber, and SLB / Hes+Ber, indicating that SLB / Hes, SLB / Ber, and SLB / Hes+Ber can be evenly dispersed into the film matrix. The appearance of small particles is due to the partial aggregation of Hes, Ber, and Hes+Ber particles, which may hinder the molecular bonding of the polymer and damage the network formation, resulting in a decrease in compatibility. The cross-section of the SLB / Hes-Ber composite film is uniform, dense, and the cracks are reduced, indicating that Hes-Ber can form good cross-linking with the SLB membrane and has good compatibility.

[0083] 3.3 X-ray powder diffraction analysis

[0084] Figure 3 are the X-ray diffraction patterns of each composite film. It can be seen that the SLB base film exhibits an amorphous structure, which is characterized by a broad diffraction band from 2θ = 13.2° to 26.1°. The diffraction patterns of all composite films are very similar to that of the SLB base film. All eutectic composite films exhibit a broad diffraction peak within 2θ = 13.2° to 26.1°, indicating the presence of an amorphous crystal structure in the material. Therefore, the addition of Hes, Ber, and the composite films of Hes+Ber and Hes-Ber to the SLB base film does not introduce any additional diffraction peaks, indicating good compatibility between the SLB base film and these added compounds.

[0085] 3.4 Thermal stability analysis of eutectic composite films

[0086] Thermal stability is very important for materials used in packaging applications. Therefore, it is necessary to study the thermal stability of the composite films. Figure 4 are the DSC curves of each composite film. It can be seen that the highest decomposition temperatures of the SLB, SLB / Hes, SLB / Ber, SLB / Hes+Ber, and SLB / Hes-Ber composite films are 295, 300, 302, 304, and 305 °C, respectively. The thermal stability of the eutectic composite films is slightly enhanced compared to the SLB base film, which is attributed to the uniform dispersion of compound particles in the film and the formation of more hydrogen bonds with the SLB substrate film, making its structure denser and more complex, thus preventing thermal decomposition. The results show that the addition of the compound has the ability to improve the thermal stability of the composite film, which is beneficial to the preservation of cooked food.

[0087] 3.5 Infrared spectroscopy analysis of eutectic composite films

[0088] Figure 5 are the infrared absorption spectra of each composite film. The characteristic peaks of the SLB substrate film are located at 3273, 2931, 1366, 1036, and 777 cm -1 , which are attributed to the stretching vibration peak of O-H, the stretching vibration peak of C-H, the stretching vibration of C-C bond, the stretching vibration peak of C-O, and the bending vibration of C-H bond, respectively. Due to the presence of -COOH, at 1633 cm -1The stretching vibration of C=O was also observed here. Compared with the SLB substrate membrane, with the addition of Hes, Ber, Hes+Ber, and Hes-Ber, most of the characteristic bands and peaks of the eutectic composite membrane are very similar to those of the SLB membrane. Among them, the O-H peak and the C=O peak show red shift and blue shift respectively, and the broadening of the peaks indicates the formation of more hydrogen bonds. The absorption peaks of the composite membrane are different in strength and shift, because Hes, Ber, Hes+Ber, and Hes-Ber bind to -COOH in SLB or form intermolecular hydrogen bonds, resulting in different degrees of weakening and shifting of the absorption peaks. The existence of hydrogen bonds keeps good compatibility between the membrane matrices.

[0089] 3.6 Preservation ability of eutectic composite membrane for fresh pork

[0090] In order to further evaluate the effectiveness of SLB, SLB / Hes, SLB / Ber, SLB / Hes+Ber, and SLB / Hes-Ber composite membranes in extending the shelf life of food, a 12-day observation experiment was carried out on fresh pork. Figure 6 It is an operation diagram for preserving pork with different composite membranes. Figure 7 It shows the appearance changes of pork in different composite membrane treatment groups during 12 days of preservation. It can be seen that the pork in the control group began to show signs of shrinkage and dullness on the second day, and after the 4th day, white mold spots of different degrees appeared on the surface of the pork. Compared with the control group, the pork in the groups using eutectic composite membranes (SLB, SLB / Hes, SLB / Ber, SLB / Hes+Ber, and SLB / Hes-Ber) maintained a brighter appearance.

[0091] 3.7 Analysis of weight loss rate

[0092] Figure 8 It shows the changes in the weight loss rate of pork in different composite membrane treatment groups during storage. It can be seen that at the end of storage (the 12th day), the weight loss rates of the SLB, SLB / Hes, SLB / Ber, SLB / Hes+Ber, and SLB / Hes-Ber groups were 50%, 46.42%, 44.31%, 45.11%, and 41.09% respectively, which were significantly lower than that of the control group (72.38%), indicating that they are more effective in restricting the water vapor loss of pork. Among them, the SLB / Hes-Ber eutectic composite membrane group had the lowest weight loss, which was due to its denser film structure, effectively preventing the passage of water vapor.

[0093] 3.8 pH

[0094] Figure 9pH changes of pork in different composite film treatment groups during storage. It can be seen that the initial pH of the pork samples was approximately 5.45, and during storage, the pH of all treatment groups increased slowly over time. This is due to the alkaline substances produced by protein decomposition. The composite films added with Hes, Ber, Hes+Ber, and Hes-Ber all had a better delaying effect on the increase in pork pH than the control group. Specifically, the SLB / Hes-Ber eutectic composite film > SLB / Hes+Ber composite film > SLB / Ber composite film > SLB / Hes composite film > non-coated film. The pH of the control group pork reached 6.63 on the 4th day, exceeding the limit value of 6.5, indicating pork spoilage. The SLB / Hes-Ber film had the most significant inhibitory effect on pork pH changes and pork spoilage. This is because at the beginning of storage, Hes-Ber slowly released Hes and Ber, effectively inhibiting the growth of microorganisms. And because pork releases alkaline substances during storage, Hes-Ber released a large amount of encapsulated Hes and Ber, further inhibiting the growth of microorganisms.

[0095] 3.9 Total viable count analysis

[0096] Figure 10 Total viable count (TVC) of pork in different composite film treatment groups during storage. This is an important indicator to measure the spoilage state of meat. It can be seen that during storage, the TVC of each group showed a significant upward trend. On the 2nd day, the TVC of the control group reached 6.0 lg CFU / g, exceeding the limit value of the national standard (6.00 lg CFU / g). On the contrary, the pork samples stored in the composite film showed TVC values below this critical limit on the 4th day, and the SLB / Hes-Ber eutectic composite film was still within the acceptable range during the 6-day storage period. Figure 10 The results show that the addition of Hes, Ber, Hes+Ber, and Hes-Ber can enhance the antibacterial effect of the SLB-based film. The SLB, SLB / Hes, SLB / Ber, SLB / Hes+Ber, and SLB / Hes-Ber composite films effectively inhibited the growth of bacteria in pork, thus extending its shelf life.

[0097] 3.10 Thiobarbituric acid reactive substances (TBARS)

[0098] TBARS values are often used as an important indicator to evaluate the degree of lipid oxidation. The TBARS value of fresh pork is approximately 0.17 mg / kg. Generally speaking, when the TBARS value of pork exceeds 0.6 mg MDA / kg, the pork will emit an unpleasant smell and cannot be eaten. Figure 11TBARS values of pork in different composite film treatment groups during storage. It can be seen that during storage, the TBARS values of each group of samples showed a continuous upward trend. The TBARS value of pork in the control group increased rapidly and reached 0.74 mg MDA / kg after 4 days of storage. The TBARS value of pork wrapped with composite films increased at a slower rate. Among them, the SLB, SLB / Hes, and SLB / Ber films reached 0.78, 0.76, and 0.72 mg MDA / kg on the 6th day, respectively, while the SLB / Hes+Ber film reached 0.76 mg MDA / kg only on the 8th day. The effect of the SLB / Hes-Ber film was the most significant, and the TBARS value was only 0.76 mg MDA / kg on the 10th day. It is shown that the slow release of Hes and Ber in the eutectic composite film can delay the ability of pork to produce TBARS.

[0099] The embodiments described above are only for describing the preferred mode of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention should fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a eutectic composite film, characterized in that, It includes the following steps: (1) Mix the pretreated bagasse powder evenly with sodium alginate, whey protein, lotus root starch, and glycerol, and add cinnamon essential oil to obtain the SLB mixed film solution; (2) Mix the SLB mixed film solution with a preservative, perform ultrasonic treatment, and then dry and shape it to obtain the eutectic composite film; The preservative is any one of hesperetin, berberine hydrochloride, a physical mixture of hesperetin + berberine hydrochloride, and a drug eutectic of hesperetin-berberine hydrochloride.

2. The preparation method according to claim 1, characterized in that, The pretreatment method of the bagasse powder is to perform water bath treatment and alkali heat treatment on the bagasse, and then dry and crush it; The temperature of the water bath treatment is 65 - 75 °C, and the time is 1.5 - 3 h; The alkali heat treatment is to mix the bagasse after water bath treatment with 4% sodium hydroxide according to a mass ratio of 1:18 - 22 and then perform heat treatment; the temperature of the alkali heat treatment is 65 - 75 °C, and the time is 1.5 - 3 h.

3. The preparation method according to claim 1, wherein The mass ratio of the pretreated bagasse powder, sodium alginate, whey protein, lotus root starch, glycerol, and cinnamon essential oil is 1 - 1.5:3 - 5:1 - 3:2 - 4:1 - 3:0.05 - 0.

2.

4. The preparation method according to claim 1, characterized in that The physical mixture of hesperetin + berberine hydrochloride is obtained by mixing hesperetin and berberine hydrochloride according to a molar ratio of 1:

1.

5. The preparation method according to claim 1, wherein, The volume ratio of the SLB mixed film solution to the preservative is 100 - 200:1 - 2.

6. The preparation method according to claim 1, wherein The concentration of the preservative is 0.03 - 0.05 mol / L.

7. The preparation method according to claim 1, characterized in that, In step (1), the temperature during mixing is 65 - 75 °C, the rotation speed is 1500 - 2500 r / min, and the time is 25 - 40 min.

8. The preparation method according to claim 1, characterized in that, In step (2), the power of the ultrasonic treatment is 200 W, the frequency is 25 kHz, and the time is 15 - 25 min.

9. The eutectic composite film prepared by the preparation method according to any one of claims 1 - 8.

10. Use of the eutectic composite film according to claim 9 in the preservation of pork, characterized in that, The pork preservation includes inhibiting the weight loss rate, microbial growth, lipid oxidation, and pH value increase during the storage of pork, and extending the shelf life of pork.

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