Preparation and application of bio-based active preservative film based on synergistic utilization of rice bran multi-components

Abstract

This invention discloses the preparation and application of a bio-based active preservation film based on the synergistic utilization of multiple components of rice bran. Using defatted rice bran as the raw material, the invention employs bacterial cellulose obtained from the fermentation of defatted rice bran hydrolysate as the structural framework of the membrane matrix. Rice bran protein from the hydrolysis residue of defatted rice bran is prepared into nanoparticles, and a Pickering emulsion is formed by stabilizing thyme essential oil with these nanoparticles. Further, the defatted rice bran-based bacterial cellulose membrane is impregnated and modified with polyvinyl alcohol and glycerol. Then, the rice bran protein-stabilized thyme essential oil Pickering emulsion is coated onto the surface of the modified membrane matrix to obtain a bio-based active preservation film. The resulting preservation film can be used for the preservation and packaging of chilled meat, and can delay microbial proliferation, lipid oxidation, protein spoilage, and color deterioration during the storage of chilled meat.

Description

Technical Field

[0001] This invention belongs to the technical field of food preservation packaging materials, specifically relating to the preparation and application of a bio-based active preservation film based on the synergistic utilization of multiple components of rice bran. In particular, it relates to a bio-based active preservation film with defatted rice bran-based bacterial cellulose as the film matrix, polyvinyl alcohol and glycerol for structural regulation, and rice bran protein-stabilized thyme essential oil Pickering emulsion as the active coating, and its application in the preservation packaging of chilled meat. Background Technology

[0002] Rice bran is an important byproduct of rice processing, rich in lipids, proteins, carbohydrates, and dietary fiber, possessing high potential for resource utilization. However, current rice bran utilization methods are mostly concentrated on feed production, rice bran oil extraction, single protein recovery, or single-path fermentation, still suffering from low overall utilization efficiency, limited product added value, and insufficient synergistic conversion of different components. Existing technologies can utilize rice bran hydrolysate for fermentation to prepare bacterial cellulose, but its applications are mostly focused on bacterial cellulose preparation, structural characterization, or gel food development, with insufficient synergistic utilization of rice bran carbohydrate and protein components within the same food packaging system. Bacterial cellulose possesses good film-forming properties, a nanofiber network structure, and biodegradability, making it suitable as a structural framework for bio-based membrane materials; however, primitive bacterial cellulose membranes are highly hydrophilic, with limited flexibility and active preservation capabilities. On the other hand, while thyme essential oil has certain antibacterial and antioxidant activities, its direct loading into membrane materials leads to easy volatility, poor dispersibility, and rapid release, making it difficult to achieve sustained preservation. Chilled meat is prone to microbial growth, lipid oxidation, protein spoilage, and color deterioration during storage. Traditional petroleum-based packaging materials mainly rely on passive physical barriers, which are insufficient in terms of greenness and active preservation capabilities, making it difficult to meet the needs of green, sustainable, and efficient preservation packaging for chilled meat. Summary of the Invention

[0003] To address the shortcomings of existing technologies, such as insufficient synergistic utilization of multiple components in rice bran, limited barrier properties and flexibility of original bacterial cellulose membranes, easy volatility and rapid release of natural essential oils when directly loaded, and insufficient active preservation capabilities of traditional petroleum-based packaging materials, this invention provides a preparation and application of a bio-based active preservation film based on the synergistic utilization of multiple components in rice bran.

[0004] This invention uses defatted rice bran as a raw material, employs bacterial cellulose derived from defatted rice bran as the structural framework of the membrane matrix, and uses rice bran protein from the hydrolysis residue of defatted rice bran to prepare rice bran protein nanoparticles. Furthermore, it constructs a rice bran protein-stabilized thyme essential oil Pickering emulsion. Simultaneously, the structure of the defatted rice bran-based bacterial cellulose membrane is regulated using polyvinyl alcohol and glycerol. The rice bran protein-stabilized thyme essential oil Pickering emulsion is then loaded onto the surface of the modified membrane matrix, resulting in a bio-based active preservation film that combines structural support, barrier regulation, sustained-release activity, antioxidant properties, and antibacterial functions.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A bio-based active preservation film based on the synergistic utilization of multiple components of rice bran, the bio-based active preservation film comprising a film substrate and an active coating loaded on at least one surface of the film substrate; the film substrate comprises defatted rice bran-based bacterial cellulose, polyvinyl alcohol and glycerin; the active coating comprises rice bran protein-stabilized thyme essential oil Pickering emulsion.

[0007] The defatted rice bran-based bacterial cellulose is used to construct the continuous structural framework of the bio-based active preservation film; the polyvinyl alcohol is used to improve the structural continuity and density of the film substrate; the glycerol is used to improve the flexibility of the film substrate; and the rice bran protein-stabilized thyme essential oil Pickering emulsion is used to endow the bio-based active preservation film with active sustained-release, antioxidant and antibacterial functions.

[0008] As a preferred embodiment of the present invention, the defatted rice bran-based bacterial cellulose is a continuous membrane-like bacterial cellulose prepared by using defatted rice bran hydrolysate as a fermentation substrate, which is purified and used as the structural framework of the membrane matrix.

[0009] As a preferred embodiment of the present invention, the defatted rice bran-based bacterial cellulose is obtained by fermentation using the bacterial cellulose-producing strain Komagataeibacter europaeus KFET1, the preservation number of which is CGMCCNo.26886.

[0010] As a preferred embodiment of the present invention, the membrane substrate is a composite membrane substrate formed by impregnation and modification of defatted rice bran-based bacterial cellulose membrane with a composite solution containing polyvinyl alcohol and glycerol; wherein the mass volume fraction of polyvinyl alcohol is 1%-3% and the mass volume fraction of glycerol is 1%-3%.

[0011] As a preferred embodiment of the present invention, the rice bran protein stabilized thyme essential oil Pickering emulsion is an oil-in-water type Pickering emulsion prepared by using rice bran protein nanoparticles as a solid particle stabilizer and thyme essential oil as the oil phase.

[0012] As a preferred embodiment of the present invention, the rice bran protein nanoparticles are prepared by hydration and ultrasonic treatment of rice bran protein extracted from defatted rice bran hydrolysis residue; the average particle size of the rice bran protein nanoparticles is 100-600 nm; in the rice bran protein stabilized thyme essential oil Pickering emulsion, the volume fraction of thyme essential oil is 10%-50%, and the concentration of rice bran protein is 1%-5% (w / v).

[0013] The present invention also provides a method for preparing the bio-based active food preservation film, comprising the following steps:

[0014] S1. Provides defatted rice bran-based bacterial cellulose membranes and defatted rice bran hydrolysis residue;

[0015] S2. Extract rice bran protein from the defatted rice bran hydrolysis residue, and prepare the rice bran protein into rice bran protein nanoparticles;

[0016] S3. Using the rice bran protein nanoparticles as a solid particle stabilizer and thyme essential oil as the oil phase, prepare a rice bran protein stabilized thyme essential oil Pickering emulsion;

[0017] S4. The defatted rice bran-based bacterial cellulose membrane is impregnated in a composite solution containing polyvinyl alcohol and glycerol, and then dried to obtain a modified membrane substrate;

[0018] S5. The rice bran protein-stabilized thyme essential oil Pickering emulsion is coated onto the surface of the modified film substrate and dried to obtain the bio-based active preservation film.

[0019] In a preferred embodiment of the present invention, rice bran raw material is weighed and subjected to Soxhlet defatting treatment with petroleum ether in step S1 to obtain defatted rice bran. The defatted rice bran is added to ultrapure water to prepare a rice bran suspension. Acetic acid is added for acid-assisted treatment, followed by enzymatic hydrolysis with a complex enzyme, including cellulase, hemicellulase, and xylanase. After enzymatic hydrolysis, the mixture is separated by centrifugation or filtration to obtain defatted rice bran hydrolysate and defatted rice bran hydrolysate residue. The defatted rice bran hydrolysate is sterilized and used as a fermentation substrate, inoculated with a bacterial cellulose-producing strain for static fermentation. The bacterial cellulose-producing strain is *Komagataeibacter europaeus* KFET1, with accession number CGMCC No. 26886 (disclosed in CN117731000A). After fermentation, the formed membrane product is removed, washed with water, treated with alkali, and washed again until neutral to obtain a defatted rice bran-based bacterial cellulose membrane.

[0020] The defatted rice bran hydrolysate is mainly used to prepare defatted rice bran-based bacterial cellulose membranes, and the defatted rice bran hydrolysate residue is further used to extract rice bran protein, thereby achieving the synergistic utilization of the carbohydrate and protein components of defatted rice bran.

[0021] In a preferred embodiment of the present invention, the defatted rice bran hydrolysis residue obtained in S1 is taken in S2, and rice bran protein is extracted using an alkali dissolution and acid precipitation method. The obtained rice bran protein is dispersed in water, the pH is adjusted to fully dissolve the protein, and after centrifugation to remove insoluble matter, the pH is adjusted to near the isoelectric point of the rice bran protein to precipitate the protein. The precipitate is collected, washed, reconstituted, and freeze-dried to obtain rice bran protein powder. The rice bran protein powder is added to deionized water to fully hydrate it, and then subjected to ultrasonic treatment to obtain rice bran protein nanoparticles.

[0022] As a further preferred embodiment of the present invention, the rice bran protein solution, after hydration, is subjected to ultrasonic treatment under ice bath conditions. The ultrasonic power is 200-600 W, and the treatment time is 5-40 min, preferably 360 W for 30 min. The resulting rice bran protein nanoparticles have an average particle size of 100-600 nm, preferably 200-400 nm.

[0023] As a preferred embodiment of the present invention, in step S3, rice bran protein nanoparticles prepared in step S2 are used as solid particle stabilizers, and thyme essential oil is used as the oil phase. The mixture is prepared by high-speed shear homogenization and ultrasonic treatment to obtain rice bran protein stabilized thyme essential oil Pickering emulsion.

[0024] As a further preferred embodiment of the present invention, the thyme essential oil has a volume fraction of 10%-50%, preferably 30%; the rice bran protein concentration is 1%-5% (w / v), preferably 2.8% (w / v); the high-speed shear homogenization speed is 8000-20000 rpm, preferably 15000 rpm; the ultrasonic power is 300-600 W, preferably 500 W; and the ultrasonic time is 5-20 min, preferably 10 min.

[0025] As a preferred embodiment of the present invention, in step S4, the defatted rice bran-based bacterial cellulose membrane obtained in step S1 is used as the structural framework and immersed in a composite solution containing polyvinyl alcohol and glycerol, so that polyvinyl alcohol and glycerol enter the nanofiber network of the defatted rice bran-based bacterial cellulose membrane. After drying, a polyvinyl alcohol / glycerol modified bacterial cellulose membrane matrix is ​​obtained.

[0026] In the composite solution containing polyvinyl alcohol and glycerol, polyvinyl alcohol is used to improve the continuity and density of the membrane substrate, and glycerol is used to improve the flexibility of the membrane substrate. The mass volume fraction of polyvinyl alcohol is 1%-3%, and the mass volume fraction of glycerol is 1%-3%. The impregnation time is 6-24 h, and the drying temperature is 25-45 ℃.

[0027] As a preferred embodiment of the present invention, the rice bran protein stabilized thyme essential oil Pickering emulsion described in S5 is loaded onto the surface of the modified film substrate by single-sided or double-sided coating, preferably by double-sided blade coating, with a total coating amount of 0.5-2.0 mL on both sides.

[0028] This invention also provides the application of the bio-based active preservation film in food preservation packaging. The food is chilled meat, including one or more of chilled beef, chilled pork, chilled mutton, chilled chicken, or chilled fish; the bio-based active preservation film is used to delay microbial proliferation, lipid oxidation, protein spoilage, and color deterioration during the storage of chilled meat.

[0029] The beneficial effects of this invention are as follows:

[0030] (1) This invention takes the synergistic utilization of multiple components of defatted rice bran as its core, uses bacterial cellulose from defatted rice bran as the structural framework of the membrane matrix, and uses rice bran protein in the hydrolysis residue of defatted rice bran as a stabilizer for Pickering emulsion particles, thereby realizing the synergistic utilization of the carbohydrate and protein components of rice bran in the same bio-based active preservation film system and improving the comprehensive utilization value of rice bran resources.

[0031] (2) In this invention, polyvinyl alcohol and glycerol are used to impregnate and modify defatted rice bran-based bacterial cellulose membranes. Polyvinyl alcohol helps to fill the pores of the bacterial cellulose network and improve the continuity and density of the membrane structure. Glycerol helps to improve the flexibility of the membrane substrate, thereby making up for the problem of insufficient flexibility and barrier properties of the original bacterial cellulose membrane.

[0032] (3) The present invention uses rice bran protein nanoparticles to stabilize thyme essential oil to construct a Pickering emulsion and loads it as an active coating on the surface of a modified membrane substrate. This can improve the dispersion stability of thyme essential oil in the membrane material, reduce the volatilization and rapid migration of essential oil, and improve the problem of excessively rapid release and insufficient sustained effect when directly loading essential oil.

[0033] (4) The bio-based active preservation film prepared by the present invention has physical barrier, active slow release, antioxidant and antibacterial functions, which can delay the proliferation of microorganisms, lipid oxidation, protein spoilage and color deterioration during the storage of chilled meat, and is suitable for green preservation packaging of chilled meat.

[0034] (5) The main functional components of the bio-based active preservation film of the present invention are derived from rice bran, an agricultural by-product. It has the characteristics of wide availability of raw materials, prominent bio-based properties, good degradability potential and environmental friendliness, and provides a new technical path for the high-value utilization of agricultural by-products and the development of sustainable food packaging materials. Attached Figure Description

[0035] Figure 1This is a technical roadmap for preparing a bio-based active preservation film based on the synergistic utilization of multiple components of rice bran, as described in this invention.

[0036] Figure 2 This is a physical image of the bio-based active food preservation film of the present invention.

[0037] Figure 3 Appearance, microscopic imaging, dispersibility and rheological characterization of rice bran protein nanoparticles and rice bran protein-stabilized thyme essential oil Pickering emulsion.

[0038] Figure 4 This is a microstructure diagram of the surface and cross-section of a bio-based active food preservation film.

[0039] Figure 5 The graphs show the water vapor barrier properties, oxygen barrier properties, and thyme essential oil release properties of different bio-based active food preservation films. As can be seen from the graphs, DRBCP2G2-E1 has the best effect.

[0040] Figure 6 The figure shows the effect of bio-based active preservation film on the appearance, total bacterial count, volatile basic nitrogen and lipid oxidation of chilled meat during storage. As can be seen from the figure, DRBCP2G2-E1 has the best preservation effect.

[0041] Figure 7 This image shows the changes in appearance of the bio-based active preservation film during its burial in the soil. Detailed Implementation

[0042] The present invention will be further described below with reference to embodiments, but the scope of protection of the present invention is not limited thereto. Within the scope of the technical concept of the present invention, those skilled in the art can make conventional adjustments or equivalent substitutions to the types of raw materials, processing conditions, coating methods, and application objects described in the present invention, and such adjustments or substitutions should all be considered to fall within the scope of protection of the present invention. The overall technical route of the present invention for preparing bio-based active preservation film based on the synergistic utilization of multiple components of rice bran is as follows: Figure 1 As shown, the resulting bio-based active food preservation film is as follows: Figure 2 As shown; the following examples use a circular membrane with a diameter of 90 mm as the specific experimental object.

[0043] Example 1: Preparation of defatted rice bran-based bacterial cellulose membrane and defatted rice bran hydrolysis residue

[0044] As a specific method in this embodiment, 300 g of defatted rice bran was weighed, 1.0 L of ultrapure water was added, 0.5% (v / v) acetic acid was added, and after stirring, a compound enzyme was added, wherein the amount of cellulase added was 0.3 wt%, the amount of hemicellulase added was 0.6 wt%, and the amount of xylanase added was 0.9 wt%. The pH was adjusted to 5.5, and enzymatic hydrolysis was carried out at 50℃ for about 4 h. After centrifugation at 8000 r / min for 5 min, the supernatant was collected as the defatted rice bran hydrolysate, and the precipitate was collected as the defatted rice bran hydrolysate residue.

[0045] The obtained defatted rice bran hydrolysate was sterilized and used as a fermentation substrate. It was inoculated with 10% (v / v) Komagataeibactereuropaeus KFET1 inoculum and statically cultured at 30 °C for 3 days to obtain a continuous membrane-like bacterial cellulose. The obtained membrane-like bacterial cellulose was repeatedly washed with deionized water and then placed in 0.5% NaOH solution at 80 °C for 30 min to remove residual bacteria and impurities. It was then washed with deionized water until neutral to obtain a defatted rice bran-based bacterial cellulose membrane, denoted as DRBC. The obtained DRBC can serve as the structural framework for subsequent bio-based active preservative films.

[0046] In this embodiment, the defatted rice bran hydrolysate is mainly used to prepare defatted rice bran-based bacterial cellulose membranes, and the defatted rice bran hydrolysate residue is further used to extract rice bran protein, thereby achieving the synergistic utilization of the carbohydrate and protein components of defatted rice bran.

[0047] Example 2: Preparation of rice bran protein nanoparticles and rice bran protein-stabilized thyme essential oil Pickering emulsion

[0048] This embodiment provides a method for preparing rice bran protein nanoparticles and rice bran protein-stabilized thyme essential oil Pickering emulsion. The defatted rice bran hydrolysis residue obtained in Example 1 was used to extract rice bran protein using an alkali-dissolution and acid-precipitation method. Specifically: the hydrolysis residue was washed to neutral, stirred at 50 ℃ and pH 11 for 4 h for alkali dissolution, the supernatant was collected by centrifugation, the pH was adjusted to 4.5, and the mixture was incubated overnight at 4 ℃ for precipitation. The precipitate was collected by centrifugation and freeze-dried to obtain rice bran protein.

[0049] The rice bran protein powder was added to deionized water to fully hydrate it, followed by ultrasonic treatment to obtain rice bran protein nanoparticles, denoted as RBPNPs. Specifically, after hydration, the rice bran protein solution was ultrasonically treated under ice bath conditions at a power of 360 W for 30 min.

[0050] Using the rice bran protein nanoparticles as a solid particle stabilizer and thyme essential oil as the oil phase, a rice bran protein-stabilized thyme essential oil Pickering emulsion, denoted as RBP-TEOE, was prepared through high-speed shear homogenization and ultrasonic treatment. The thyme essential oil volume fraction was 30%; the rice bran protein concentration was 2.8% (w / v); the high-speed shear homogenization speed was 15000 rpm; the ultrasonic power was 500 W; and the ultrasonic time was 10 min. The appearance, microscopic imaging, dispersibility, and rheological characterization of the obtained RBPNPs and RBP-TEOE are as follows: Figure 3 As shown.

[0051] Example 3: Preparation of Polyvinyl Alcohol / Glycerol Modified Defatted Rice Bran-Based Bacterial Cellulose Membrane Matrix

[0052] This embodiment provides a method for preparing a modified membrane substrate, and the prepared composite membrane is as follows: Figure 2 As shown. Using the defatted rice bran-based bacterial cellulose membrane obtained in Example 1 as the structural framework, it was impregnated in a composite solution containing polyvinyl alcohol and glycerol. Specifically: polyvinyl alcohol was added to deionized water and heated and stirred at 90 °C until completely dissolved to prepare a 2% (w / v) polyvinyl alcohol solution; after the temperature dropped to approximately 70 °C, glycerol was added to bring the final glycerol concentration to 2% (w / v), and stirring was continued for 1 h to obtain a polyvinyl alcohol / glycerol composite solution. The defatted rice bran-based bacterial cellulose membrane was impregnated in the composite solution for 12 h, then removed and dried at 30 °C to obtain the modified membrane substrate, denoted as DRBCP2G2.

[0053] As controls, DRBCP1 containing only 1% polyvinyl alcohol, DRBCP2 containing only 2% polyvinyl alcohol, and DRBCP2G1 containing 2% polyvinyl alcohol and 1% glycerol can also be prepared separately. These different modified membrane substrates can be used to compare the effects of polyvinyl alcohol and glycerol on the membrane substrate structure, mechanical properties, and barrier properties.

[0054] Example 4: Preparation of Bio-based Active Preservative Film

[0055] This embodiment provides a method for preparing a bio-based active food preservation film based on the synergistic utilization of multiple components of rice bran. The polyvinyl alcohol / glycerol modified bacterial cellulose membrane substrate obtained in Example 3 is used. The rice bran protein-stabilized thyme essential oil Pickering emulsion obtained in Example 2 is coated onto at least one side of the modified membrane substrate. After drying, a bio-based active food preservation film is obtained.

[0056] The coating method is single-sided coating or double-sided coating, preferably double-sided doctor blade coating. The total coating amount of the rice bran protein stabilized thyme essential oil Pickering emulsion is 0.5–2.0 mL, preferably 0.5–1.5 mL.

[0057] As a specific embodiment, a DRBCP2G2 membrane was used as the modified membrane substrate. RBP-TEOE was uniformly coated on both sides of the membrane substrate at a total double-sided coating amount of 0.5 mL, 1.0 mL, and 1.5 mL, respectively. After drying, DRBCP2G2-E0.5, DRBCP2G2-E1, and DRBCP2G2-E1.5 were obtained, respectively. Thyme essential oil was also directly coated on both sides of a 90 mm diameter DRBCP2G2 membrane with a total double-sided coating amount of 300 μL, i.e., 150 μL on each side, to prepare a control membrane directly loaded with essential oil, denoted as DRBCP2G2-TEO.

[0058] The resulting bio-based active food preservation film comprises a film matrix and an active coating loaded on the surface of the film matrix. The film matrix is ​​composed of defatted rice bran-based bacterial cellulose, polyvinyl alcohol, and glycerol; the active coating is composed of a rice bran protein-stabilized thyme essential oil Pickering emulsion. Defatted rice bran-based bacterial cellulose provides the structural framework, polyvinyl alcohol and glycerol regulate the density and flexibility of the film matrix, and the rice bran protein-stabilized thyme essential oil Pickering emulsion imparts the film material with active sustained-release, antioxidant, and antibacterial functions. The surface and cross-sectional microstructures of different bio-based active food preservation films are shown below. Figure 4 As shown.

[0059] Example 5: Evaluation of the barrier properties, release properties, and antioxidant properties of bio-based active food preservation film.

[0060] This embodiment evaluates the performance of the bio-based active food preservation film obtained in Example 4, including its water vapor barrier performance, oxygen barrier performance, thyme essential oil release performance, and free radical scavenging ability. The relevant barrier performance and release performance results are as follows: Figure 5 As shown.

[0061] The specific method for determining water vapor transmission rate is as follows: Approximately 10 g of anhydrous calcium chloride (25 °C, 0% RH) is added to a centrifuge tube as a desiccant. The tube opening is covered with the membrane sample to be tested and sealed with a rubber ring. The tube is then placed in a desiccator containing a saturated potassium nitrate solution to create a test environment of 25 °C and 90% relative humidity. The weight gain of the centrifuge tube is recorded every 12 hours during the measurement period until the mass change stabilizes, and the result is calculated using the following formula:

[0062]

[0063] Where ΔM represents the mass increment of the centrifuge tube during the measurement period (g); D is the thickness of the composite membrane (cm); and A represents the effective permeation area of ​​the membrane sample (cm²). 2 ); T is the time interval between two adjacent weighings (s); ΔP is the difference in water vapor partial pressure across the membrane at 25 °C (Pa).

[0064] Specifically, the method for determining oxygen permeability is as follows: Place 3 g of deoxidizer in a 50 mL centrifuge tube, seal the tube opening with a membrane sample, and weigh the initial mass m1. Then, place the sample in a desiccator containing saturated barium chloride solution at a relative humidity of 85% for 48 hours, and weigh it again. Record the resulting mass as m2. Calculate OP using the formula:

[0065]

[0066] In the formula, t is the measurement time (h), and A is the effective area of ​​the centrifuge tube opening (m²). 2 ).

[0067] The method for determining the release rate of thyme essential oil is as follows: A composite membrane is cut into rectangular samples of 4 cm × 4 cm and placed in a centrifuge tube containing a certain volume of 95% ethanol. A release test is conducted at a constant temperature of 25 °C for 96 h. Samples are taken at set time points, and the absorbance of the simulated solution at a wavelength of 273 nm is measured. The release amount of thyme essential oil is calculated based on the measurement results, and the release rate is calculated using the following formula:

[0068]

[0069] Among them, C t C0 represents the cumulative release of thyme essential oil in the food simulation liquid at the corresponding time point, and C0 represents the initial content of thyme essential oil in the membrane.

[0070] The method for determining the storage loss rate of thyme essential oil is as follows: Cut the sample membrane into appropriately sized pieces, use n-hexane as the extraction solvent, shake thoroughly, and then let it stand at room temperature for 12 h. Centrifuge the extraction system, collect the supernatant, and measure its absorbance at 273 nm. Calculate the thyme essential oil concentration using a standard curve. The storage loss rate is calculated according to the following formula:

[0071]

[0072] Where C0 is the initial concentration of thyme essential oil in the film, C t This represents the residual concentration of thyme essential oil in the film at the corresponding storage time point.

[0073] Antioxidant properties are achieved using ABTS. + Evaluation was performed using free radical scavenging and DPPH free radical scavenging assays. 100 mg of membrane sample was added to 2 mL of 10% ethanol solution, and the mixture was extracted at room temperature in the dark with shaking for 12 h. After centrifugation, the supernatant was used as the membrane extraction buffer; this was then compared with ABTS... + After the free radical solution and DPPH free radical solution react, the change in absorbance is measured and the free radical scavenging rate is calculated.

[0074] The absorbance of a stable ABTS⁺ solution at 734 nm is denoted as A. i The absorbance of the composite membrane after the reaction is denoted as A. f And observe the color change simultaneously. ABTS⁺ free radical scavenging rate is calculated according to the following formula:

[0075]

[0076] The DPPH· free radical scavenging rate was determined by calculating the DPPH· free radical scavenging rate of the sample according to the following formula:

[0077]

[0078] Where A0 is the blank absorbance and A is the sample absorbance.

[0079] The results showed that, compared with the original defatted rice bran-based bacterial cellulose membrane, the introduction of polyvinyl alcohol / glycerol modification and emulsion coating improved the barrier properties and functional activity of the membrane material. Among them, DRBCP2G2-E1 exhibited superior overall performance, with its water vapor permeability reduced to 0.475 × 10⁻⁶. -12 g·cm / (cm 2 With an oxygen permeability of 2.04 g / (h·m·Pa), the oxygen permeability can be reduced to 2.04 g / (h·m·Pa). 2 This unit represents the mass increment per unit time and unit area due to oxygen permeation and absorption by the deoxidizer. Thyme essential oil achieved a cumulative release rate of 82.94% after 96 hours, with approximately 70.7 hours required to reach 80% release, demonstrating good sustained-release performance. The membrane's ABTS... + The free radical scavenging rate and DPPH· free radical scavenging rate can reach 92.46% and 56.77% respectively, indicating that it has strong antioxidant activity.

[0080] Example 6: Application of Bio-based Active Preservative Film in the Preservation of Chilled Meat

[0081] This embodiment provides the application of the bio-based active preservation film in the preservation of chilled meat. Fresh chilled beef was cut into meat samples of roughly the same size and covered or wrapped using different packaging methods. The following treatment groups were set up: uncovered group (CK); polyethylene film packaging group (PE); original defatted rice bran-based bacterial cellulose membrane group (DRBC); polyvinyl alcohol / glycerol modified membrane matrix group (DRBCP2G2); directly loaded thyme essential oil membrane group (DRBCP2G2-TEO); and rice bran protein stabilized thyme essential oil Pickering emulsion active membrane group (DRBCP2G2-E1). The samples were stored at 4 ℃, and beef quality indicators were measured at 0, 2, 4, 6, 8, 10, and 12 days. Changes in appearance, total bacterial count, volatile basic nitrogen, and lipid oxidation degree are as follows: Figure 6 As shown.

[0082] The quality indicators include appearance and color, pH, total bacterial count, volatile basic nitrogen, and thiobarbituric acid reactive substance value. The total bacterial count is used to evaluate the degree of microbial proliferation, volatile basic nitrogen is used to evaluate the degree of protein spoilage, and the thiobarbituric acid reactive substance value is used to evaluate the degree of lipid oxidation.

[0083] The results showed that chilled beef treated with the bio-based active preservative film of this invention exhibited a slower rate of quality deterioration during storage. Compared with the uncovered group, the polyethylene film group, and the original defatted rice bran-based bacterial cellulose film group, the DRBCP2G2-E1 group was more effective in delaying color deterioration, microbial proliferation, lipid oxidation, and protein spoilage in chilled beef. After 12 days of storage, the total bacterial count in the DRBCP2G2-E1 treatment group remained at 5.97 lg CFU / g, the volatile basic nitrogen remained at 14.92 mg / 100 g, and the thiobarbituric acid reactive value was 1.02 mg / kg, indicating that this bio-based active preservative film can delay the quality deterioration of chilled meat and is suitable for green preservation packaging of chilled meat.

[0084] Example 7 Evaluation of the soil burial degradation performance of bio-based active food preservation film

[0085] A 40-day soil burial test was conducted using polyethylene film, virgin defatted rice bran-based bacterial cellulose film, and DRBCP2G2-E1 film as control and test samples, respectively. The appearance changes of different samples during soil burial are shown below. Figure 7 As shown in the figure. The results indicate that the polyethylene film remained largely intact during the burial process, while the original defatted rice bran-based bacterial cellulose film degraded relatively quickly. The DRBCP2G2-E1 film showed significant mass loss and structural damage after 40 days, with a mass loss rate of up to 43.6%, indicating that the bio-based active preservation film described in this invention has certain degradability potential.

Claims

1. A bio-based active food preservation film based on the synergistic utilization of multiple components of defatted rice bran, characterized in that, The bio-based active preservation film includes a film substrate and an active coating loaded on at least one surface of the film substrate; The membrane matrix comprises defatted rice bran-based bacterial cellulose, polyvinyl alcohol, and glycerol; The active coating comprises a rice bran protein-stabilized thyme essential oil Pickering emulsion.

2. The bio-based active food preservation film according to claim 1, characterized in that, The defatted rice bran-based bacterial cellulose is a continuous membrane-like bacterial cellulose obtained by using defatted rice bran hydrolysate as a fermentation substrate. After purification, the continuous membrane-like bacterial cellulose serves as the structural framework of the membrane matrix.

3. The bio-based active food preservation film according to claim 1, characterized in that, The membrane substrate is a composite membrane substrate formed by impregnating and modifying a defatted rice bran-based bacterial cellulose membrane with a composite solution containing polyvinyl alcohol and glycerol; wherein the mass volume fraction of the polyvinyl alcohol is 1%-3% and the mass volume fraction of the glycerol is 1%-3%.

4. The bio-based active food preservation film according to claim 1, characterized in that, The rice bran protein stabilized thyme essential oil Pickering emulsion is an oil-in-water type Pickering emulsion prepared using rice bran protein nanoparticles as a solid particle stabilizer and thyme essential oil as the oil phase.

5. The bio-based active food preservation film according to claim 4, characterized in that, The rice bran protein nanoparticles are prepared by hydration and ultrasonic treatment of rice bran protein extracted from defatted rice bran hydrolysis residue; the average particle size of the rice bran protein nanoparticles is 100-600 nm; in the rice bran protein stabilized thyme essential oil Pickering emulsion, the volume fraction of thyme essential oil is 10%-50% and the concentration of rice bran protein is 1%-5% (w / v).

6. A method for preparing the bio-based active food preservation film according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Provides defatted rice bran-based bacterial cellulose membranes and defatted rice bran hydrolysis residue; S2. Extract rice bran protein from the defatted rice bran hydrolysis residue, and prepare the rice bran protein into rice bran protein nanoparticles; S3. Using the rice bran protein nanoparticles as a solid particle stabilizer and thyme essential oil as the oil phase, prepare a rice bran protein stabilized thyme essential oil Pickering emulsion; S4. The defatted rice bran-based bacterial cellulose membrane is impregnated in a composite solution containing polyvinyl alcohol and glycerol, and then dried to obtain a modified membrane substrate; S5. The rice bran protein stabilized thyme essential oil Pickering emulsion is coated on the surface of the modified film substrate and dried to obtain the bio-based active preservation film; The defatted rice bran-based bacterial cellulose membrane and the rice bran protein are derived from the carbohydrate and protein components of defatted rice bran, respectively.

7. The preparation method according to claim 6, characterized in that, The rice bran protein nanoparticles described in S2 are prepared by rice bran protein hydration and ultrasonic treatment. The ultrasonic treatment power is 200-600 W and the treatment time is 5-40 min.

8. The preparation method according to claim 6, characterized in that, The rice bran protein-stabilized thyme essential oil Pickering emulsion described in S3 was prepared by high-speed shear homogenization and ultrasonic treatment; wherein, the high-speed shear homogenization speed was 8000-20000 rpm, the ultrasonic power was 300-600 W, and the ultrasonic time was 5-20 min.

9. The preparation method according to claim 6, characterized in that, The impregnation time in S4 is 6-24 h, and the drying temperature is 25-45 ℃; the rice bran protein stabilized thyme essential oil Pickering emulsion in S5 is loaded onto the surface of the modified membrane substrate by single-sided or double-sided coating, preferably by double-sided blade coating; when the modified membrane substrate is a circular membrane with a diameter of 90 mm, the total coating amount of the rice bran protein stabilized thyme essential oil Pickering emulsion on both sides is 0.5-1.5 mL, that is, the coating amount on each side is 0.25-0.75 mL; based on a single-sided membrane area of ​​63.62 cm², the coating amount on each side is 3.93-11.79 μL / cm².

10. The application of the bio-based active preservation film according to any one of claims 1-5 in the preparation of food preservation packaging, wherein the food is chilled meat, and the chilled meat includes one or more of chilled beef, chilled pork, chilled mutton, chilled chicken or chilled fish.

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