A eutectic composite film, a preparation method thereof and application thereof in pork preservation

Abstract

The application discloses a co-crystal composite film and a preparation method and application thereof in pork preservation, and belongs to the technical field of food preservation. The preparation method of the hesperetin co-crystal composite film comprises the following steps: (1) uniformly mixing pretreated bagasse powder, sodium alginate, whey protein, lotus root starch and glycerol, and adding cinnamon essential oil to obtain an SLB mixed film liquid; and (2) mixing the SLB mixed film liquid with a preservative, carrying out ultrasonic treatment, and drying and shaping to obtain the co-crystal composite film. The SLB is used as a film forming substrate, the glycerol is added as a plasticizer, and the hesperetin, berberine hydrochloride, a physical mixture of hesperetin and berberine hydrochloride or a hesperetin-berberine hydrochloride drug co-crystal is used as a preservative to prepare a co-crystal composite film. It is verified that the co-crystal composite film can significantly inhibit pork corruption and prolong the shelf life of pork under normal temperature conditions.

Description

Technical Field

[0001] This invention relates to the field of food preservation technology, and in particular to a eutectic composite film, its preparation method, and its application in pork preservation. Background Technology

[0002] With the rapid development of fresh food supermarkets and the continuous improvement of cold chain logistics systems, chilled pork, due to its high quality, is gradually becoming the preferred choice for consumers, demonstrating a broad market prospect. Pork is widely popular for its unique flavor and high nutritional value, being rich in vitamin B and fatty acids. However, pork is susceptible to microbial contamination and spoilage during storage, transportation, and sales, posing a significant challenge to the food industry. Inhibiting microorganisms is crucial for preserving pork and ensuring its safety. Therefore, developing environmentally friendly and sustainable food packaging films is of great significance in the food packaging industry.

[0003] Antibacterial films, as an active packaging material, are a favorable choice for food packaging, extending shelf life. However, existing active food packaging films are typically composed of a single component, resulting in limited performance and difficulty in meeting the complex preservation needs of food. Sodium alginate (SA), a biodegradable natural polysaccharide, possesses advantages such as long polymer chains, easy availability, and non-toxicity, making it a green candidate material for manufacturing food packaging films. Lotus root starch (LRS), a natural, multifunctional, and environmentally friendly starch, has unique physicochemical properties that make it an ideal raw material for food packaging film development. Sugarcane bagasse (SCB), the fibrous residue remaining after sugarcane extraction, can be compounded with natural polymers (such as starch and chitosan) to create food packaging materials with good mechanical and barrier properties.

[0004] Hesperetin (Hes) is a natural flavonoid compound and a powerful antioxidant. Although hesperetin is a valuable and safe biopreservative, its hydrophobic nature sometimes causes it to precipitate and is not easily dispersed in polymer matrices. Studies have shown that preparing hesperetin into drug cocrystals using cocrystallization technology 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 are currently no reports on the preparation of composite films using hesperetin or berberine hydrochloride. Summary of the Invention

[0005] The purpose of this invention is to provide a eutectic composite film, its preparation method, and its application in pork preservation, thereby solving the problems existing in the prior art. This invention uses SLB as the film-forming substrate, adds glycerol as a plasticizer, and uses hesperidin, berberine hydrochloride, a physical mixture of hesperidin and berberine hydrochloride, or a hesperidin-berberine hydrochloride drug eutectic as a preservative to prepare a eutectic composite film. Verification has shown that this eutectic composite film can significantly inhibit pork spoilage and extend the shelf life of pork under room temperature conditions.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] This invention provides a method for preparing a eutectic composite film, comprising the following steps:

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

[0009] (2) The SLB mixed membrane solution is mixed with a preservative, ultrasonically treated, and then dried and shaped to obtain the eutectic composite membrane;

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

[0011] Furthermore, the pretreatment method for the sugarcane bagasse powder is to subject the sugarcane bagasse to water bath treatment and alkaline heat treatment, followed by drying and pulverizing.

[0012] The water bath treatment is carried out at a temperature of 65-75℃ for 1.5-3 hours.

[0013] The alkaline heat treatment involves mixing sugarcane bagasse after water bath treatment with 4% sodium hydroxide at a mass ratio of 1:18-22 and then heating the mixture. The temperature of the alkaline heat treatment is 65-75℃, and the time is 1.5-3 hours.

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

[0015] Furthermore, the physical mixture of hesperidin and berberine hydrochloride is obtained by mixing hesperidin and berberine hydrochloride in a molar ratio of 1:1.

[0016] Furthermore, the hesperidin-berberine hydrochloride drug cocrystal is the hesperidin-berberine hydrochloride drug cocrystal disclosed in CN 115650941 A.

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

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

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

[0020] Furthermore, in step (2), the ultrasonic treatment has a power of 200W, a frequency of 25kHz, and a duration of 15-25min.

[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-mentioned eutectic composite membrane in pork preservation, wherein the pork preservation includes inhibiting the weight loss rate, microbial growth, lipid oxidation and pH rise of pork during storage, thereby extending the shelf life of pork.

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

[0024] This invention employs a simple and convenient blending film-forming strategy combined with eutectic technology to successfully prepare a novel structurally stable eutectic composite film for meat preservation. This eutectic composite film uses SLB as the film-forming substrate, adds glycerol as a plasticizer, and uses hesperidin, berberine hydrochloride, a physical mixture of hesperidin and berberine hydrochloride, or a hesperidin-berberine hydrochloride pharmaceutical eutectic as the preservative. Verification has shown that using the eutectic composite film of this invention to package pork can significantly inhibit weight loss, microbial growth, lipid oxidation, and pH rise during pork storage at room temperature, extending the shelf life of pork by up to 6 days.

[0025] This invention employs a simple and convenient blending film-forming strategy combined with eutectic technology to successfully prepare a novel eutectic composite film for meat preservation with stable structure. It features high stability, low cost, and the ability to achieve long-term and continuous release of biological preservatives. When used for pork preservation, it not only maintains the color of pork but also inhibits its spoilage and further extends the shelf life of pork, showing broad commercial prospects. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 The transparency test results are for 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 membranes;

[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 for SLB, SLB / Hes, SLB / Ber, SLB / Hes+Ber and SLB / Hes-Ber composite membranes;

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

[0032] Figure 6 Diagrams illustrating the operation of using different composite films to preserve pork;

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

[0034] Figure 8 The changes in weight loss rate of pork in different composite membrane treatment groups during storage;

[0035] Figure 9 pH changes in pork treated with different composite membranes during storage;

[0036] Figure 10 The changes in total viable bacteria (TVC) in pork treated with different composite membranes during storage;

[0037] Figure 11 The changes in TBARS values ​​of pork treated with different composite films during storage. Detailed Implementation

[0038] Various exemplary embodiments of the present invention will now 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, features, and embodiments of the present invention.

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

[0040] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0041] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0042] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0043] Example 1: Preparation of Eutectic Composite Film

[0044] 1. Preparation of sugarcane bagasse powder

[0045] Peel and wash the sugarcane bagasse, then add distilled water until it covers the surface of the bagasse. Heat in a 70°C water bath for 2 hours, stirring constantly. After heating, rinse the surface of the bagasse with distilled water to remove any adhering substances, drain the water, and add a 4% sodium hydroxide solution at a mass ratio of sugarcane bagasse to sodium hydroxide of 1:20. Stir magnetically at 70°C for 2 hours, then rinse repeatedly with distilled water until the rinsing solution is transparent and the pH is below 8. Dry the bagasse at 60°C, pulverize it, and sieve it to obtain bagasse powder with a particle size of less than 200 mesh.

[0046] 2. Preparation of film-forming solution and eutectic composite film

[0047] Disperse 4g sodium alginate, 1.2g sugarcane bagasse powder, 2g whey protein, 3g lotus root starch, and 2g glycerol in 150mL distilled water. Place the membrane solution in a constant temperature magnetic water bath and stir for 30min at 70℃ and 2000r / min until homogeneous. Then cool the membrane solution to room temperature and filter it through a 20-mesh screen to remove insoluble powder clumps. Add 100mg cinnamon essential oil to the filtrate and stir well to obtain the SLB mixed membrane solution for later use.

[0048] 150 mL of SLB mixed membrane solution was mixed with 1.17 mL of hesperidin (Hes), berberine hydrochloride (Ber), a physical mixture of hesperidin and berberine hydrochloride (Hes+Ber), and a hesperidin-berberine hydrochloride drug eutectic (Hes-Ber) with a molar concentration of 0.04 mol / L, respectively. After stirring evenly, the mixture was ultrasonically treated (200 W, 25 kHz) for 20 min to obtain the final composite membrane solution. The SLB mixed membrane solution and the composite membrane solution were respectively poured onto glass plates coated with glycerol to ensure uniform thickness, and dried in a 55℃ drying oven for 5 h to form films. The composite membranes obtained above were named SLB, SLB / Hes, SLB / Ber, SLB / Hes+Ber, and SLB / Hes-Ber, respectively.

[0049] The preparation method of the above-mentioned physical mixture of hesperidin and berberine hydrochloride (Hes+Ber) is as follows: Hesperidin and berberine hydrochloride are mixed at a molar ratio of 1:1, and DMSO solution is added to dissolve them completely.

[0050] The aforementioned hesperidin-berberine hydrochloride drug cocrystal (Hes-Ber) is the hesperidin-berberine hydrochloride drug cocrystal disclosed in CN 115650941 A.

[0051] Example 2: Performance Verification of the Eutectic Composite Membrane

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

[0053] 1. Characterization of eutectic composite films

[0054] 1.1 X-ray powder diffraction analysis

[0055] SLB, SLB / Hes, SLB / Ber, SLB / Hes+Ber, and SLB / Hes-Ber composite films were tested on a Rigaku MiniFlex 600 diffractometer using Cu target Kα rays as the light source, with a voltage of 40 kV and a current of 15 mA. The scanning range was set to 3–70° (2θ), the scanning speed to 10° / min, and the step size to 0.02° (2θ). The obtained data were processed using Origin 2021 software.

[0056] 1.2 Thermal Analysis

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

[0058] 1.3 Infrared Spectroscopy Analysis

[0059] 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 at 40°C for 4 hours, then a suitable amount was thoroughly ground and mixed with dried potassium bromide under an infrared lamp. A suitable amount was placed in a mold, and the sample was pressed into a transparent sheet, which was then scanned using the infrared spectrometer. The scanning range was 4000–500 cm⁻¹. -1 With an average of one scan, the spectral resolution is 4 cm⁻¹. -1 .

[0060] 1.4 Morphology of Composite Membranes

[0061] The morphology and transparency of each composite film were recorded using a camera. The surface and cross-sectional microstructure 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 film was frozen in liquid nitrogen and rapidly broken to ensure a clear and intact cross-section, and then a gold layer was applied using an ion sputtering coater.

[0062] 2. The preservation ability of composite film for pork

[0063] Fresh pork tenderloin, available in local supermarkets, was selected. Exposed fat and connective tissue were removed, and the meat was cut into 5g cubes. Patients were randomly assigned to four groups: control group, SLB group, SLB / Hes group, SLB / Ber group, SLB / Hes+Ber group, and SLB / Hes-Ber group. The pork was then placed in sterilized glass jars, and the jar openings were covered tightly with the prepared eutectic composite membrane. The control group had its jar openings not covered with the composite membrane. The pork was stored at room temperature for 12 days. During this period, three pieces of pork were randomly selected from each group for testing.

[0064] 2.1 Changes in appearance

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

[0066] 2.2 Weight Loss Rate (WLR)

[0067] The weight loss rate of pork during storage was determined by gravimetric method within 0-12 days. The formula for calculating the weight loss rate is as follows:

[0068]

[0069] Where W0 is the initial weight of the pork, in grams; W S The weight of pork after it has been preserved and stored for several days, in grams.

[0070] 2.3 pH

[0071] Pork samples were taken out after different storage days. One piece (5g) was weighed, added to 50mL of distilled water and stirred evenly. After soaking for 30min, it was centrifuged at 3000r for 10min. The pH of the supernatant was measured with a pH meter.

[0072] 2.4 Determination of total bacterial count

[0073] Pork samples were removed after different storage days, aseptically transferred to gastric bags containing 50 ml of sterile PBS solution, homogenized, and the supernatant was collected. The supernatant was then diluted to 10. -3 Then, 200 μL was spread on LB broth solid medium, with 3 replicates per group. The medium was placed in a refrigerator at 4–8 °C for 2 h to infiltrate, and then continuously shaken at 37 °C for 24 h before colony counting and statistical analysis.

[0074] 2.5 Determination of Thiobarbituric Acid Value (TBARS)

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

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

[0077] Among them, OD 532nm , where is the absorbance value for 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 film

[0080] Figure 1 The images show the appearance of each composite film. It is evident that, compared to the SLB film, the SLB / Hes, SLB / Ber, SLB / Hes+Ber, and SLB / Hes-Ber composite films exhibit a significant darkening and yellowing trend. This color change is attributed to the inherent color of the added Ber. However, the composite films maintain high transparency throughout the color change process, demonstrating their potential for practical applications.

[0081] 3.2 Morphology of Eutectic Composite Films

[0082] Figure 2 SEM images of the composite films are shown. It can be seen that the surface of the SLB substrate film is relatively rough, and cracks are observed in the cross-section. The surfaces of the SLB / Hes, SLB / Ber, SLB / Hes+Ber, and SLB / Hes-Ber composite films are smooth, uniform, and continuous, indicating good compatibility between Hes, Ber, Hes+Ber, Hes-Ber, and SLB. Small particles are uniformly 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 uniformly dispersed in the film matrix. The presence of small particles is due to partial aggregation of Hes, Ber, and Hes+Ber particles, which may hinder polymer molecular bonding, disrupt network formation, and lead to decreased compatibility. In contrast, the SLB / Hes-Ber composite film has a uniform and dense cross-section with fewer cracks, indicating that Hes-Ber can form good cross-links with the SLB film and has good compatibility.

[0083] 3.3 X-ray powder diffraction analysis

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

[0085] 3.4 Thermal stability analysis of eutectic composite film

[0086] Thermal stability is crucial for materials used in packaging applications. Therefore, it is necessary to study the thermal stability of composite films. Figure 4 The DSC curves for each composite membrane are shown. It can be seen that the maximum decomposition temperatures of the SLB, SLB / Hes, SLB / Ber, SLB / Hes+Ber, and SLB / Hes-Ber composite membranes are 295, 300, 302, 304, and 305 °C, respectively. The eutectic composite membrane exhibits slightly enhanced thermal stability compared to the SLB base membrane. This is attributed to the uniform dispersion of compound particles within the film and the formation of more hydrogen bonds with the SLB base membrane, resulting in a denser and more complex structure that prevents pyrolysis. The results indicate that the addition of the compound enhances the thermal stability of the composite membrane, which is beneficial for the preservation of cooked food.

[0087] 3.5 Infrared Spectroscopic Analysis of Eutectic Composite Film

[0088] Figure 5 The infrared absorption spectra of each composite membrane are shown. The characteristic peaks of the SLB substrate membrane are located at 3273, 2931, 1366, 1036, and 777 cm⁻¹. -1 The peaks at 1633 cm⁻¹ are attributed to the stretching vibrations of OH, CH, C / C bond, CO, and CH bond, respectively. The presence of -COOH at this peak contributes to the peak at 1633 cm⁻¹. -1C=O stretching vibrations were also observed. Compared to the SLB substrate film, with the addition of Hes, Ber, Hes+Ber, and Hes-Ber, most of the characteristic bands and peaks of the eutectic composite film are very similar to those of the SLB film. The OH peak and C=O peak show red shifts and blue shifts, respectively, and the peak broadening indicates the formation of more hydrogen bonds. The absorption peaks of the composite film exhibit varying intensities and shifts because Hes, Ber, Hes+Ber, and Hes-Ber bind to the -COOH groups in the SLB or interact with intermolecular hydrogen bonds, resulting in varying degrees of weakening and shifting of the absorption peaks. The presence of hydrogen bonds maintains good compatibility between the film and the substrate.

[0089] 3.6 The effect of eutectic composite film on pork preservation

[0090] To further evaluate the effectiveness of SLB, SLB / Hes, SLB / Ber, SLB / Hes+Ber, and SLB / Hes-Ber composite films in extending the shelf life of food, a 12-day observational experiment was conducted on fresh pork. Figure 6 The diagram illustrates the operation of using different composite films to preserve pork. Figure 7 The appearance changes of pork treated with different composite films during the 12-day shelf life are shown. 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 fourth day, varying degrees of white mold spots appeared on the surface of the pork. Compared with the control group, the pork treated with eutectic composite films (SLB, SLB / Hes, SLB / Ber, SLB / Hes+Ber, and SLB / Hes-Ber) maintained a brighter appearance.

[0091] 3.7 Weight Loss Analysis

[0092] Figure 8 The changes in weight loss rate of pork treated with different composite membranes during storage are shown. It can be seen that at the end of storage (day 12), 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, significantly lower than the control group (72.38%), indicating that they are more effective in limiting water vapor loss in pork. Among them, the SLB / Hes-Ber eutectic composite membrane group had the lowest weight loss, which is due to its denser membrane structure, effectively preventing the passage of water vapor.

[0093] 3.8 pH

[0094] Figure 9The pH changes of pork treated with different composite membranes during storage are shown. The initial pH of the pork samples was approximately 5.45. During storage, the pH of all treatment groups slowly increased over time. This is due to the alkaline substances produced by protein decomposition. The composite membranes with added Hes, Ber, Hes+Ber, and Hes-Ber were all more effective than the control group in delaying the increase in pork pH, specifically: SLB / Hes-Ber eutectic composite membrane > SLB / Hes+Ber composite membrane > SLB / Ber composite membrane > SLB / Hes composite membrane > uncoated membrane. The pH of the control group pork reached 6.63 on day 4, exceeding the limit of 6.5, indicating pork spoilage. The SLB / Hes-Ber membrane showed the most significant inhibitory effect on pH changes and pork spoilage. This is because Hes-Ber slowly releases Hes and Ber at the beginning of storage, effectively inhibiting microbial growth. Furthermore, because pork releases alkaline substances during storage, Hes-Ber releases a large amount of encapsulated Hes and Ber, further inhibiting the growth of microorganisms.

[0095] 3.9 Total Colony Count Analysis

[0096] Figure 10 The total viable count (TVC) of pork treated with different composite membranes during storage is a crucial indicator of meat spoilage. It is evident that the TVC in all groups showed a significant upward trend during storage. On day 2, the TVC in the control group reached 6.01 g CFU / g, exceeding the national standard limit (6.001 g CFU / g). Conversely, pork samples stored in the composite membrane showed TVC values ​​below this critical limit on day 4, while the SLB / Hes-Ber eutectic composite membrane remained within acceptable limits during the 6-day storage period. Figure 10 The results showed that the addition of Hes, Ber, Hes+Ber and Hes-Ber could enhance the antibacterial effect of the SLB substrate membrane. The SLB, SLB / Hes, SLB / Ber, SLB / Hes+Ber and SLB / Hes-Ber composite membranes effectively inhibited the growth of bacteria in pork, thereby extending its shelf life.

[0097] 3.10 Thiobarbituric acid reactants (TBARS)

[0098] The TBARS value is often used as an important indicator for evaluating 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 odor and should not be eaten. Figure 11The TBARS values ​​of pork treated with different composite membranes were shown during storage. It can be seen that the TBARS values ​​of all samples showed a continuous upward trend during storage. The TBARS value of the control group pork increased rapidly, reaching 0.74 mg MDA / kg after 4 days of storage. The TBARS value of pork wrapped in composite membranes increased more slowly. Specifically, the SLB, SLB / Hes, and SLB / Ber membranes reached 0.78, 0.76, and 0.72 mg MDA / kg on day 6, respectively, while the SLB / Hes+Ber membrane only reached 0.76 mg MDA / kg on day 8. The SLB / Hes-Ber membrane showed the most significant effect, with a TBARS value of only 0.76 mg MDA / kg by day 10. This indicates that the slow release of Hes and Ber from the eutectic composite membrane can delay the formation of TBARS in pork.

[0099] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a eutectic composite film, characterized in that, Includes the following steps: (1) The pretreated bagasse powder is mixed evenly with sodium alginate, whey protein, lotus root starch and glycerin, and cinnamon essential oil is added to obtain SLB mixed membrane solution; the mass ratio of the pretreated bagasse powder, sodium alginate, whey protein, lotus root starch, glycerin and cinnamon essential oil is 1-1.5:3-5:1-3:2-4:1-3:0.05-0.2; (2) The SLB mixed membrane solution is mixed with the preservative, ultrasonically treated, and then dried and shaped to obtain the eutectic composite membrane; the volume ratio of the SLB mixed membrane solution to the preservative is 100-200:1-2; the concentration of the preservative is 0.03-0.05 mol / L; The preservative is any one of hesperidin, berberine hydrochloride, a physical mixture of hesperidin and berberine hydrochloride, and a hesperidin-berberine hydrochloride drug eutectic. The physical mixture of hesperidin and berberine hydrochloride is obtained by mixing hesperidin and berberine hydrochloride in a molar ratio of 1:

1.

2. The preparation method according to claim 1, characterized in that, The pretreatment method for the sugarcane bagasse powder is to subject the sugarcane bagasse to water bath treatment and alkaline heat treatment, followed by drying and pulverizing. The water bath treatment is carried out at a temperature of 65-75℃ for 1.5-3 hours. The alkaline heat treatment involves mixing sugarcane bagasse after water bath treatment with 4% sodium hydroxide at a mass ratio of 1:18-22 and then heating the mixture. The temperature of the alkaline heat treatment is 65-75℃, and the time is 1.5-3 hours.

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

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

5. The eutectic composite film prepared by the preparation method according to any one of claims 1-4.

6. The application of the eutectic composite film according to claim 5 in pork preservation, characterized in that, The pork preservation method includes inhibiting weight loss, microbial growth, lipid oxidation, and pH increase during pork storage, thereby extending the shelf life of pork.

Images