Liquid food sterilization method based on cooperation of magnetic induction electric field and composite bacteriostatic agent

Abstract

The invention provides a liquid food sterilization method based on synergy of a magnetic induction electric field and a compound bacteriostatic agent, which comprises the following steps: firstly, adding the prepared compound bacteriostatic agent into liquid food, standing, and triggering citric acid release by utilizing glucose oxidase in the compound bacteriostatic agent to catalyze acid production so as to realize primary bacteriostasis; then, a magnetic induction electric field is started, L-alanine and alanyl-glycine are induced to be synergistically released, bacterial spores are efficiently promoted to be converted from a dormant state to a nutritional state, meanwhile, the magnetic field drives magnetic particles to move, thyme essential oil nano-emulsion is released through mechanical extrusion, and the germinated spores are killed immediately; and long-term bacteriostasis is realized through slow release of the essential oil subsequently. According to the scheme, the industrial problems that an existing low-temperature sterilization technology is low in spore inactivation efficiency, and an efficient natural bacteriostatic agent is unstable, difficult to dissolve or affects flavor are effectively solved, the commercial sterile requirement is met under the mild condition, and the shelf life of liquid food is remarkably prolonged.

Description

Technical Field

[0001] This invention belongs to the field of liquid food sterilization technology, specifically relating to a liquid food sterilization method based on the synergistic effect of magnetic induction electric field and composite antibacterial agent. Background Technology

[0002] Sterilization of liquid foods (such as fruit and vegetable juices, milk, etc.) is a crucial process for ensuring food safety and extending shelf life. Traditional heat sterilization technologies, such as pasteurization and ultra-high temperature (UHT) sterilization, while effectively killing microorganisms, inevitably have adverse effects on the flavor, color, and nutritional components of the food due to prolonged high-temperature processing, leading to a decline in product quality. To overcome the drawbacks of heat processing, low-temperature sterilization technology has emerged and become a research hotspot in the food processing field.

[0003] Among numerous low-temperature sterilization technologies, magnetic induction electric field technology has shown great potential due to its advantages such as uniform heating, low sterilization temperature, and strong penetration. This technology induces an induced electric field inside food through a high-frequency alternating magnetic field, thereby causing irreversible damage to microbial cell membranes and biomolecules, achieving sterilization. However, those skilled in the art have found in practice that existing magnetic induction electric field technology still has significant limitations, especially when processing liquid foods containing bacterial spores, where the results are unsatisfactory. Bacterial spores are dormant forms of certain bacteria under adverse environments, possessing a dense cortex and shell structure, exhibiting strong resistance to physical stress, electric fields, and radiation. Magnetic induction electric fields are highly effective at killing active vegetative bacteria, but have little effect on dormant spores. Simply increasing the magnetic field strength or extending the processing time to inactivate spores not only leads to a sharp decrease in energy efficiency but may also have negative effects due to overheating, violating the original intention of low-temperature sterilization and potentially damaging the flavor and nutrition of the food. Therefore, how to efficiently and gently inactivate bacterial spores in liquid foods is a key bottleneck in achieving commercial sterilization and widely promoting the application of low-temperature sterilization technology.

[0004] On the other hand, to compensate for the shortcomings of physical sterilization, adding natural antibacterial agents has become an effective auxiliary strategy. Natural ingredients such as lysozyme, glucose oxidase, and thyme essential oil have received widespread attention due to their safety and high efficacy. However, these highly effective antibacterial ingredients also face many challenges in practical applications. First, many enzyme preparations (such as glucose oxidase) are easily inactivated in complex food systems, and their action depends on specific substrates and pH environments, limiting their effectiveness. Second, although plant essential oils (such as thyme essential oil) have broad-spectrum antibacterial properties, they are poorly soluble in water, volatile, chemically unstable, and their strong characteristic flavor can easily damage the original flavor of food. Direct addition not only results in low sterilization efficiency but may also affect the acceptability of the product. Currently, although some studies have attempted to encapsulate essential oils using technologies such as microencapsulation, how to ensure their stability while achieving controllable and targeted release under specific triggering conditions remains a problem that urgently needs to be solved.

[0005] Therefore, there is an urgent need in this field to develop a novel synergistic sterilization method that can organically combine physical field sterilization with chemical antibacterial action, in order to achieve efficient and simultaneous killing of vegetative bacteria and spores in liquid food under mild processing conditions, while taking into account product quality and shelf life. Summary of the Invention

[0006] Technical Problem to be Solved: To address the aforementioned technical problems, the purpose of this invention is to provide a method for sterilizing liquid food based on the synergistic effect of a magnetic induction electric field and a composite antibacterial agent. First, the prepared composite antibacterial agent is added to the liquid food and allowed to stand. The glucose oxidase inside the food catalyzes acid production, triggering the release of citric acid and achieving initial antibacterial action. Subsequently, a magnetic induction electric field is activated, inducing the synergistic release of L-alanine and alanyl-glycine, efficiently promoting the transformation of bacterial spores from a dormant state to a nutrient state. Simultaneously, the magnetic field drives the movement of magnetic particles, mechanically releasing thyme essential oil nanoemulsion, instantly killing germinating spores. Long-term antibacterial action is then achieved through the sustained release of the essential oil.

[0007] Technical solution: A method for sterilizing liquid food based on the synergistic effect of magnetic induction electric field and composite antibacterial agent, comprising the following steps: S1. Add 0.1-0.5% compound antibacterial agent to the liquid food to be processed, stir at 100-200 rpm to disperse evenly, and let stand at room temperature for 30-60 minutes; S2. After the settling period, turn on the magnetic induction electric field device and process for 10-60 seconds to obtain sterilized liquid food.

[0008] Furthermore, the preparation steps of the compound antibacterial agent in step S1 are as follows: (1) Dissolve gelatin in water and stir evenly at 50-60℃ to obtain a gelatin solution with a concentration of 8-10%; (2) Add citric acid to the gelatin solution and react at 60-70℃ for 2-4 hours to obtain a citric acid-gelatin composite solution; (3) Dissolve β-cyclodextrin in water and stir at 55-65℃ to prepare a β-cyclodextrin solution with a concentration of 5-10%; then mix thyme essential oil and Tween 80 at a mass ratio of (2-4):1 by vortexing to obtain an oil phase mixture; finally, add the oil phase mixture dropwise to the β-cyclodextrin solution under high-speed shearing at 10000-12000rpm, place it in an ice water bath, sonicate at 400-600W for 2-4min, and let it stand overnight at 4℃ to obtain a thyme essential oil / β-cyclodextrin encapsulated nanoemulsion; (4) Add 1-2 mg / mL glucose oxidase, 5-10 mg / mL Ala-Gly-Fe3O4@pullulan polysaccharide, 2-5 mg / mL L-alanine and thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to the citric acid-gelatin composite solution in sequence, then add 1-3% CaCl2 and mix evenly to obtain the composite antibacterial agent.

[0009] Furthermore, in step (2), the mass ratio of citric acid to gelatin is 1:(4-5).

[0010] Furthermore, in step (3), the volume ratio of the oil phase mixture to the β-cyclodextrin solution is 1:(10-20).

[0011] Furthermore, the preparation steps of Ala-Gly-Fe3O4@pulllan polysaccharide in step (4) are as follows: Step 1. Mix Fe3O4 nanoparticles with a 1-5% pullulan polysaccharide solution and stir at 400-500 rpm for 1.5-2 hours to obtain Fe3O4@pullulan polysaccharide dispersion; Step 2. Add 0.1-0.5M ethylenediamine to the Fe3O4@pullulan polysaccharide dispersion, react at pH 8-9 and 50-60℃ for 4-6 hours to obtain aminated Fe3O4@pullulan polysaccharide; Step 3. Mix aminated Fe3O4@pullulan with 1-5 mg / mL Ala-Gly solution at a volume ratio of 1:(1-3) and stir at room temperature for 12-24 h to obtain Ala-Gly-Fe3O4@pullulan.

[0012] Furthermore, in step (4), the volume ratio of thyme essential oil / β-cyclodextrin inclusion nanoemulsion to citric acid-gelatin composite solution is 1:(5-10).

[0013] Furthermore, the parameters of the magnetic induction electric field in step S2 are: excitation voltage of 500-800V, frequency of 50-100kHz, field strength of 50-100 V / cm, and induced current density of 0.1-0.3A / cm. 2 .

[0014] Furthermore, the liquid food includes fruit juice, vegetable juice, and milk.

[0015] Beneficial effects: This invention prepares a composite antibacterial agent that can be added to liquid foods for sterilization. The composite antibacterial agent uses gelatin hydrogel microspheres as a framework, encapsulating citric acid, glucose oxidase, Ala-Gly-Fe3O4@pullulan, L-alanine, and thyme essential oil nanoemulsion. Citric acid reacts with the hydroxyl groups in gelatin molecules, covalently linking to the gelatin molecular chain via ketal bonds; glucose oxidase (GOD) is physically co-encapsulated; Ala-Gly-Fe3O4@pullulan is physically dispersed in the gelatin microspheres; L-alanine binds to the gelatin through electrostatic interactions; and thyme essential oil / β-cyclodextrin inclusion nanoemulsion is encapsulated within a three-dimensional gel network. The preparation of Ala-Gly-Fe3O4@pullulan in this invention is specifically as follows: First, Fe3O4@pullulan core is prepared, then ethylenediamine is added to aminate pullulan (introducing amino active sites), and finally alanyl-glycine (Ala-Gly) is loaded onto it. The amino group reacts with the carboxyl group in the alanyl-glycine molecule to form a stable peptide bond. This invention utilizes a composite antibacterial agent and a magnetic induction electric field to synergistically kill bacteria. The specific sterilization mechanism is as follows: (1) First, add the compound antibacterial agent to the liquid food and let it stand. Water enters the microspheres and activates GOD. GOD catalyzes the glucose in the liquid food to generate gluconic acid. The pH inside the microspheres drops to <5.0, triggering the hydrolysis of ketal bonds and the release of citric acid, which initially inhibits the growth of Gram-positive bacteria. (2) After standing for a certain period of time, the magnetic induction electric field device is activated. At this time, citric acid is released and the local pH drops to 4.0-4.5 (lower than the isoelectric point of gelatin, 4.5-5.2). The charge of gelatin changes from negative to positive, destroying the electrostatic interaction with L-alanine, and L-alanine is released. After the magnetic induction electric field is activated, the high-frequency vibration accelerates the shedding of alanyl-glycine. Both are spore germination inducers, and their synergistic release can significantly improve the spore germination rate. In addition, the short peptide structure of alanyl-glycine is more easily recognized by peptidases on the spore surface, accelerating the transformation of spores from a dormant state to a nutrient state, laying the foundation for subsequent sterilization. When the magnetic induction electric field is turned on, the Ala-Gly-Fe3O4@pulllan polysaccharide particles dispersed in the three-dimensional network of gelatin microspheres generate high-frequency vibration and rotation. The violent movement of these magnetic particles will generate continuous shear force and compression on the surrounding dense gelatin gel network. This mechanical force from the inside out will directly act on the thyme essential oil / β-cyclodextrin nanoemulsion droplets embedded in the gel network, squeezing the droplets out of the pores of the gel network and killing the germinating spores. (3) With the release of citric acid, L-alanine and alanyl-glycine, a low pH environment (4.0-5.0) is maintained around the microspheres. The gel network gradually swells under acidic conditions. The remaining thyme essential oil / β-cyclodextrin encapsulated in the gel network gradually diffuses to the outside of the microspheres as the gel swells. At the same time, β-cyclodextrin slightly dissociates at low pH and continues to release thyme essential oil, achieving slow and continuous release. Thyme essential oil has broad-spectrum antibacterial activity. Its main components (such as carvacrol and thymol) can destroy the bacterial cell membrane structure and cause leakage of cell contents. Slow release can ensure that the concentration of essential oil in food is maintained at an effective antibacterial concentration, avoiding excessive concentration that would change the flavor of food. At the same time, it achieves long-term antibacterial effect and extends the shelf life of food. Detailed Implementation

[0016] The present invention will be further described below with reference to embodiments. These embodiments are illustrative of the present invention, but the present invention is not limited to these embodiments: Example 1

[0017] A method for sterilizing liquid food based on the synergistic effect of magnetic induction electric field and composite antibacterial agent includes the following steps: (1) Fe3O4 nanoparticles were mixed with a 3% pullulan polysaccharide solution and stirred at 500 rpm for 2 h to obtain Fe3O4@pullulan polysaccharide dispersion; (2) Add 0.3M ethylenediamine to the Fe3O4@pullulan polysaccharide dispersion, react at pH 8 and 60℃ for 5 h to obtain aminated Fe3O4@pullulan polysaccharide; (3) Mix aminated Fe3O4@pulllan polysaccharide with 4 mg / mL Ala-Gly solution at a volume ratio of 1:1 and stir at room temperature for 20 h to obtain Ala-Gly-Fe3O4@pulllan polysaccharide; (4) Dissolve gelatin in water and stir at 60°C until homogeneous to obtain a gelatin solution with a concentration of 8%; (5) Add citric acid to the gelatin solution, with a mass ratio of citric acid to gelatin of 1:4, and react at 60°C for 4 hours to obtain a citric acid-gelatin composite solution; (6) Dissolve β-cyclodextrin in water and stir at 65°C to prepare a β-cyclodextrin solution with a concentration of 8%; then mix thyme essential oil and Tween 80 at a mass ratio of 4:1 by vortexing to obtain an oil phase mixture; finally, add the oil phase mixture dropwise to the β-cyclodextrin solution at a high speed of 10000rpm with a volume ratio of 1:15, place it in an ice water bath, sonicate at 400W for 4min, and let it stand overnight at 4°C to obtain a thyme essential oil / β-cyclodextrin encapsulated nanoemulsion; (7) Add 2 mg / mL glucose oxidase, 5 mg / mL Ala-Gly-Fe3O4@pullulan polysaccharide, 4 mg / mL L-alanine and thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to the citric acid-gelatin composite solution in sequence, wherein the volume ratio of thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to citric acid-gelatin composite solution is 1:5, then add 2% CaCl2 and mix evenly to obtain the composite antibacterial agent; (8) Add 0.1% compound antibacterial agent to the apple juice to be treated, stir at 200 rpm to disperse evenly, and let stand at room temperature for 30 min; (9) After the static period, turn on the magnetic induction electric field device with an excitation voltage of 500V, a frequency of 50 kHz, an electric field strength of 50 V / cm, and an induced current density of 0.2A / cm. 2 Process for 40 seconds to obtain sterilized apple juice.

[0018] Example 2 A method for sterilizing liquid food based on the synergistic effect of magnetic induction electric field and composite antibacterial agent includes the following steps: (1) Fe3O4 nanoparticles were mixed with a 3% pullulan polysaccharide solution and stirred at 500 rpm for 2 h to obtain Fe3O4@pullulan polysaccharide dispersion; (2) Add 0.3M ethylenediamine to the Fe3O4@pullulan polysaccharide dispersion, react at pH 8 and 60℃ for 5 h to obtain aminated Fe3O4@pullulan polysaccharide; (3) Mix aminated Fe3O4@pulllan polysaccharide with 4 mg / mL Ala-Gly solution at a volume ratio of 1:3 and stir at room temperature for 20 h to obtain Ala-Gly-Fe3O4@pulllan polysaccharide; (4) Dissolve gelatin in water and stir at 60°C until homogeneous to obtain a gelatin solution with a concentration of 8%; (5) Add citric acid to the gelatin solution, with a mass ratio of citric acid to gelatin of 1:4, and react at 60°C for 4 hours to obtain a citric acid-gelatin composite solution; (6) Dissolve β-cyclodextrin in water and stir at 65°C to prepare a β-cyclodextrin solution with a concentration of 8%; then mix thyme essential oil and Tween 80 at a mass ratio of 4:1 by vortexing to obtain an oil phase mixture; finally, add the oil phase mixture dropwise to the β-cyclodextrin solution at a high speed of 10000rpm with a volume ratio of 1:15, place it in an ice water bath, sonicate at 400W for 4min, and let it stand overnight at 4°C to obtain a thyme essential oil / β-cyclodextrin encapsulated nanoemulsion; (7) Add 2 mg / mL glucose oxidase, 5 mg / mL Ala-Gly-Fe3O4@pullulan polysaccharide, 4 mg / mL L-alanine and thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to the citric acid-gelatin composite solution in sequence, wherein the volume ratio of thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to citric acid-gelatin composite solution is 1:5, then add 2% CaCl2 and mix evenly to obtain the composite antibacterial agent; (8) Add 0.1% compound antibacterial agent to the carrot juice to be treated, stir at 200 rpm to disperse evenly, and let stand at room temperature for 30 min; (9) After the static period, turn on the magnetic induction electric field device with an excitation voltage of 500V, a frequency of 50 kHz, an electric field strength of 50 V / cm, and an induced current density of 0.2A / cm. 2 Process for 40 seconds to obtain sterilized carrot juice.

[0019] Example 3 A method for sterilizing liquid food based on the synergistic effect of magnetic induction electric field and composite antibacterial agent includes the following steps: (1) Fe3O4 nanoparticles were mixed with a 3% pullulan polysaccharide solution and stirred at 500 rpm for 2 h to obtain Fe3O4@pullulan polysaccharide dispersion; (2) Add 0.3M ethylenediamine to the Fe3O4@pullulan polysaccharide dispersion, react at pH 8 and 60℃ for 5 h to obtain aminated Fe3O4@pullulan polysaccharide; (3) Mix aminated Fe3O4@pulllan polysaccharide with 4 mg / mL Ala-Gly solution at a volume ratio of 1:2 and stir at room temperature for 20 h to obtain Ala-Gly-Fe3O4@pulllan polysaccharide; (4) Dissolve gelatin in water and stir at 60°C until homogeneous to obtain a 10% gelatin solution; (5) Add citric acid to the gelatin solution, with a mass ratio of citric acid to gelatin of 1:4, and react at 60°C for 4 hours to obtain a citric acid-gelatin composite solution; (6) Dissolve β-cyclodextrin in water and stir at 65°C to prepare a β-cyclodextrin solution with a concentration of 8%; then mix thyme essential oil and Tween 80 at a mass ratio of 4:1 by vortexing to obtain an oil phase mixture; finally, add the oil phase mixture dropwise to the β-cyclodextrin solution at a high speed of 10000rpm with a volume ratio of 1:15, place it in an ice water bath, sonicate at 400W for 4min, and let it stand overnight at 4°C to obtain a thyme essential oil / β-cyclodextrin encapsulated nanoemulsion; (7) Add 2 mg / mL glucose oxidase, 5 mg / mL Ala-Gly-Fe3O4@pullulan polysaccharide, 4 mg / mL L-alanine and thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to the citric acid-gelatin composite solution in sequence, wherein the volume ratio of thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to citric acid-gelatin composite solution is 1:5, then add 2% CaCl2 and mix evenly to obtain the composite antibacterial agent; (8) Add 0.1% compound antibacterial agent to the milk to be treated, stir at 200 rpm to disperse evenly, and let stand at room temperature for 30 min; (9) After the static period, turn on the magnetic induction electric field device with an excitation voltage of 500V, a frequency of 50kHz, a field strength of 50V / cm, and an induced current density of 0.2A / cm. 2 Process for 40 seconds to obtain sterilized milk.

[0020] Example 4 A method for sterilizing liquid food based on the synergistic effect of magnetic induction electric field and composite antibacterial agent includes the following steps: (1) Fe3O4 nanoparticles were mixed with a 3% pullulan polysaccharide solution and stirred at 500 rpm for 2 h to obtain Fe3O4@pullulan polysaccharide dispersion; (2) Add 0.3M ethylenediamine to the Fe3O4@pullulan polysaccharide dispersion, react at pH 8 and 60℃ for 5 h to obtain aminated Fe3O4@pullulan polysaccharide; (3) Mix aminated Fe3O4@pulllan polysaccharide with 4 mg / mL Ala-Gly solution at a volume ratio of 1:2 and stir at room temperature for 20 h to obtain Ala-Gly-Fe3O4@pulllan polysaccharide; (4) Dissolve gelatin in water and stir at 60°C until homogeneous to obtain a 10% gelatin solution; (5) Add citric acid to the gelatin solution, with a mass ratio of citric acid to gelatin of 1:5, and react at 60°C for 4 hours to obtain a citric acid-gelatin composite solution; (6) Dissolve β-cyclodextrin in water and stir at 65°C to prepare a β-cyclodextrin solution with a concentration of 8%; then mix thyme essential oil and Tween 80 at a mass ratio of 4:1 by vortexing to obtain an oil phase mixture; finally, add the oil phase mixture dropwise to the β-cyclodextrin solution at a high speed of 10000rpm with a volume ratio of 1:15, place it in an ice water bath, sonicate at 400W for 4min, and let it stand overnight at 4°C to obtain a thyme essential oil / β-cyclodextrin encapsulated nanoemulsion; (7) Add 2 mg / mL glucose oxidase, 5 mg / mL Ala-Gly-Fe3O4@pullulan polysaccharide, 4 mg / mL L-alanine and thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to the citric acid-gelatin composite solution in sequence, wherein the volume ratio of thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to citric acid-gelatin composite solution is 1:5, then add 2% CaCl2 and mix evenly to obtain the composite antibacterial agent; (8) Add 0.1% compound antibacterial agent to the apple juice to be treated, stir at 200 rpm to disperse evenly, and let stand at room temperature for 30 min; (9) After the static period, turn on the magnetic induction electric field device with an excitation voltage of 500V, a frequency of 50kHz, a field strength of 50V / cm, and an induced current density of 0.2A / cm. 2 Process for 40 seconds to obtain sterilized apple juice.

[0021] Example 5 A method for sterilizing liquid food based on the synergistic effect of magnetic induction electric field and composite antibacterial agent includes the following steps: (1) Fe3O4 nanoparticles were mixed with a 3% pullulan polysaccharide solution and stirred at 500 rpm for 2 h to obtain Fe3O4@pullulan polysaccharide dispersion; (2) Add 0.3M ethylenediamine to the Fe3O4@pullulan polysaccharide dispersion, react at pH 8 and 60℃ for 5 h to obtain aminated Fe3O4@pullulan polysaccharide; (3) Mix aminated Fe3O4@pulllan polysaccharide with 4 mg / mL Ala-Gly solution at a volume ratio of 1:2 and stir at room temperature for 20 h to obtain Ala-Gly-Fe3O4@pulllan polysaccharide; (4) Dissolve gelatin in water and stir at 60°C until homogeneous to obtain a 10% gelatin solution; (5) Add citric acid to the gelatin solution, with a mass ratio of citric acid to gelatin of 1:5, and react at 60°C for 4 hours to obtain a citric acid-gelatin composite solution; (6) Dissolve β-cyclodextrin in water and stir at 65°C to prepare a β-cyclodextrin solution with a concentration of 8%; then mix thyme essential oil and Tween 80 at a mass ratio of 4:1 by vortexing to obtain an oil phase mixture; finally, add the oil phase mixture dropwise to the β-cyclodextrin solution at a high speed of 10000rpm with a volume ratio of 1:15, place it in an ice water bath, sonicate at 400W for 4min, and let it stand overnight at 4°C to obtain a thyme essential oil / β-cyclodextrin encapsulated nanoemulsion; (7) Add 2 mg / mL glucose oxidase, 8 mg / mL Ala-Gly-Fe3O4@pullulan polysaccharide, 4 mg / mL L-alanine and thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to the citric acid-gelatin composite solution in sequence, wherein the volume ratio of thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to citric acid-gelatin composite solution is 1:5, then add 2% CaCl2 and mix evenly to obtain the composite antibacterial agent; (8) Add 0.1% compound antibacterial agent to the apple juice to be treated, stir at 200 rpm to disperse evenly, and let stand at room temperature for 30 min; (9) After the static period, turn on the magnetic induction electric field device with an excitation voltage of 500V, a frequency of 50 kHz, a field strength of 50V / cm, and an induced current density of 0.2A / cm. 2 Process for 40 seconds to obtain sterilized apple juice.

[0022] Example 6 A method for sterilizing liquid food based on the synergistic effect of magnetic induction electric field and composite antibacterial agent includes the following steps: (1) Fe3O4 nanoparticles were mixed with a 3% pullulan polysaccharide solution and stirred at 500 rpm for 2 h to obtain Fe3O4@pullulan polysaccharide dispersion; (2) Add 0.3M ethylenediamine to the Fe3O4@pullulan polysaccharide dispersion, react at pH 8 and 60℃ for 5 h to obtain aminated Fe3O4@pullulan polysaccharide; (3) Mix aminated Fe3O4@pulllan polysaccharide with 4 mg / mL Ala-Gly solution at a volume ratio of 1:2 and stir at room temperature for 20 h to obtain Ala-Gly-Fe3O4@pulllan polysaccharide; (4) Dissolve gelatin in water and stir at 60°C until homogeneous to obtain a 10% gelatin solution; (5) Add citric acid to the gelatin solution, with a mass ratio of citric acid to gelatin of 1:5, and react at 60°C for 4 hours to obtain a citric acid-gelatin composite solution; (6) Dissolve β-cyclodextrin in water and stir at 65°C to prepare a β-cyclodextrin solution with a concentration of 8%; then mix thyme essential oil and Tween 80 at a mass ratio of 4:1 by vortexing to obtain an oil phase mixture; finally, add the oil phase mixture dropwise to the β-cyclodextrin solution at a high speed of 10000rpm with a volume ratio of 1:15, place it in an ice water bath, sonicate at 400W for 4min, and let it stand overnight at 4°C to obtain a thyme essential oil / β-cyclodextrin encapsulated nanoemulsion; (7) Add 2 mg / mL glucose oxidase, 10 mg / mL Ala-Gly-Fe3O4@pullulan polysaccharide, 4 mg / mL L-alanine and thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to the citric acid-gelatin composite solution in sequence, wherein the volume ratio of thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to citric acid-gelatin composite solution is 1:8, then add 2% CaCl2 and mix evenly to obtain the composite antibacterial agent; (8) Add 0.1% compound antibacterial agent to the apple juice to be treated, stir at 200 rpm to disperse evenly, and let stand at room temperature for 30 min; (9) After the static period, turn on the magnetic induction electric field device with an excitation voltage of 5000V, a frequency of 50kHz, a field strength of 50V / cm, and an induced current density of 0.2A / cm. 2 Process for 40 seconds to obtain sterilized apple juice.

[0023] Example 7 A method for sterilizing liquid food based on the synergistic effect of magnetic induction electric field and composite antibacterial agent includes the following steps: (1) Fe3O4 nanoparticles were mixed with a 3% pullulan polysaccharide solution and stirred at 500 rpm for 2 h to obtain Fe3O4@pullulan polysaccharide dispersion; (2) Add 0.3M ethylenediamine to the Fe3O4@pullulan polysaccharide dispersion, react at pH 8 and 60℃ for 5 h to obtain aminated Fe3O4@pullulan polysaccharide; (3) Mix aminated Fe3O4@pulllan polysaccharide with 4 mg / mL Ala-Gly solution at a volume ratio of 1:2 and stir at room temperature for 20 h to obtain Ala-Gly-Fe3O4@pulllan polysaccharide; (4) Dissolve gelatin in water and stir at 60°C until homogeneous to obtain a 10% gelatin solution; (5) Add citric acid to the gelatin solution, with a mass ratio of citric acid to gelatin of 1:5, and react at 60°C for 4 hours to obtain a citric acid-gelatin composite solution; (6) Dissolve β-cyclodextrin in water and stir at 65°C to prepare a β-cyclodextrin solution with a concentration of 8%; then mix thyme essential oil and Tween 80 at a mass ratio of 4:1 by vortexing to obtain an oil phase mixture; finally, add the oil phase mixture dropwise to the β-cyclodextrin solution at a high speed of 10000rpm with a volume ratio of 1:15, place it in an ice water bath, sonicate at 400W for 4min, and let it stand overnight at 4°C to obtain a thyme essential oil / β-cyclodextrin encapsulated nanoemulsion; (7) Add 2 mg / mL glucose oxidase, 10 mg / mL Ala-Gly-Fe3O4@pullulan polysaccharide, 4 mg / mL L-alanine and thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to the citric acid-gelatin composite solution in sequence, wherein the volume ratio of thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to citric acid-gelatin composite solution is 1:10, then add 2% CaCl2 and mix evenly to obtain the composite antibacterial agent; (8) Add 0.1% compound antibacterial agent to the apple juice to be treated, stir at 200 rpm to disperse evenly, and let stand at room temperature for 30 min; (9) After the static period, turn on the magnetic induction electric field device with an excitation voltage of 500V, a frequency of 50kHz, a field strength of 50V / cm, and an induced current density of 0.2A / cm. 2 Process for 40 seconds to obtain sterilized apple juice.

[0024] Example 8 A method for sterilizing liquid food based on the synergistic effect of magnetic induction electric field and composite antibacterial agent includes the following steps: (1) Fe3O4 nanoparticles were mixed with a 3% pullulan polysaccharide solution and stirred at 500 rpm for 2 h to obtain Fe3O4@pullulan polysaccharide dispersion; (2) Add 0.3M ethylenediamine to the Fe3O4@pullulan polysaccharide dispersion, react at pH 8 and 60℃ for 5 h to obtain aminated Fe3O4@pullulan polysaccharide; (3) Mix aminated Fe3O4@pulllan polysaccharide with 4 mg / mL Ala-Gly solution at a volume ratio of 1:2 and stir at room temperature for 20 h to obtain Ala-Gly-Fe3O4@pulllan polysaccharide; (4) Dissolve gelatin in water and stir at 60°C until homogeneous to obtain a 10% gelatin solution; (5) Add citric acid to the gelatin solution, with a mass ratio of citric acid to gelatin of 1:5, and react at 60°C for 4 hours to obtain a citric acid-gelatin composite solution; (6) Dissolve β-cyclodextrin in water and stir at 65°C to prepare a β-cyclodextrin solution with a concentration of 8%; then mix thyme essential oil and Tween 80 at a mass ratio of 4:1 by vortexing to obtain an oil phase mixture; finally, add the oil phase mixture dropwise to the β-cyclodextrin solution at a high speed of 10000rpm with a volume ratio of 1:15, place it in an ice water bath, sonicate at 400W for 4min, and let it stand overnight at 4°C to obtain a thyme essential oil / β-cyclodextrin encapsulated nanoemulsion; (7) Add 2 mg / mL glucose oxidase, 10 mg / mL Ala-Gly-Fe3O4@pullulan polysaccharide, 4 mg / mL L-alanine and thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to the citric acid-gelatin composite solution in sequence, wherein the volume ratio of thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to citric acid-gelatin composite solution is 1:8, then add 2% CaCl2 and mix evenly to obtain the composite antibacterial agent; (8) Add 0.5% compound antibacterial agent to the apple juice to be treated, stir at 200 rpm to disperse evenly, and let stand at room temperature for 30 min; (9) After the static period, turn on the magnetic induction electric field device with an excitation voltage of 500V, a frequency of 50kHz, a field strength of 50V / cm, and an induced current density of 0.2A / cm. 2 Process for 40 seconds to obtain sterilized apple juice.

[0025] Example 9 A method for sterilizing liquid food based on the synergistic effect of magnetic induction electric field and composite antibacterial agent includes the following steps: (1) Fe3O4 nanoparticles were mixed with a 3% pullulan polysaccharide solution and stirred at 500 rpm for 2 h to obtain Fe3O4@pullulan polysaccharide dispersion; (2) Add 0.3M ethylenediamine to the Fe3O4@pullulan polysaccharide dispersion, react at pH 8 and 60℃ for 5 h to obtain aminated Fe3O4@pullulan polysaccharide; (3) Mix aminated Fe3O4@pulllan polysaccharide with 4 mg / mL Ala-Gly solution at a volume ratio of 1:2 and stir at room temperature for 20 h to obtain Ala-Gly-Fe3O4@pulllan polysaccharide; (4) Dissolve gelatin in water and stir at 60°C until homogeneous to obtain a 10% gelatin solution; (5) Add citric acid to the gelatin solution, with a mass ratio of citric acid to gelatin of 1:5, and react at 60°C for 4 hours to obtain a citric acid-gelatin composite solution; (6) Dissolve β-cyclodextrin in water and stir at 65°C to prepare a β-cyclodextrin solution with a concentration of 8%; then mix thyme essential oil and Tween 80 at a mass ratio of 4:1 by vortexing to obtain an oil phase mixture; finally, add the oil phase mixture dropwise to the β-cyclodextrin solution at a high speed of 10000rpm with a volume ratio of 1:15, place it in an ice water bath, sonicate at 400W for 4min, and let it stand overnight at 4°C to obtain a thyme essential oil / β-cyclodextrin encapsulated nanoemulsion; (7) Add 2 mg / mL glucose oxidase, 10 mg / mL Ala-Gly-Fe3O4@pullulan polysaccharide, 4 mg / mL L-alanine and thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to the citric acid-gelatin composite solution in sequence, wherein the volume ratio of thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to citric acid-gelatin composite solution is 1:8, then add 2% CaCl2 and mix evenly to obtain the composite antibacterial agent; (8) Add 0.4% compound antibacterial agent to the apple juice to be treated, stir at 200 rpm to disperse evenly, and let stand at room temperature for 30 min; (9) After the static period, turn on the magnetic induction electric field device with an excitation voltage of 500V, a frequency of 100 kHz, a field strength of 100V / cm, and an induced current density of 0.2A / cm. 2 Process for 40 seconds to obtain sterilized apple juice.

[0026] Example 10 A method for sterilizing liquid food based on the synergistic effect of magnetic induction electric field and composite antibacterial agent includes the following steps: (1) Fe3O4 nanoparticles were mixed with a 3% pullulan polysaccharide solution and stirred at 500 rpm for 2 h to obtain Fe3O4@pullulan polysaccharide dispersion; (2) Add 0.3M ethylenediamine to the Fe3O4@pullulan polysaccharide dispersion, react at pH 8 and 60℃ for 5 h to obtain aminated Fe3O4@pullulan polysaccharide; (3) Mix aminated Fe3O4@pulllan polysaccharide with 4 mg / mL Ala-Gly solution at a volume ratio of 1:2 and stir at room temperature for 20 h to obtain Ala-Gly-Fe3O4@pulllan polysaccharide; (4) Dissolve gelatin in water and stir at 60°C until homogeneous to obtain a 10% gelatin solution; (5) Add citric acid to the gelatin solution, with a mass ratio of citric acid to gelatin of 1:5, and react at 60°C for 4 hours to obtain a citric acid-gelatin composite solution; (6) Dissolve β-cyclodextrin in water and stir at 65°C to prepare a β-cyclodextrin solution with a concentration of 8%; then mix thyme essential oil and Tween 80 at a mass ratio of 4:1 by vortexing to obtain an oil phase mixture; finally, add the oil phase mixture dropwise to the β-cyclodextrin solution at a high speed of 10000rpm with a volume ratio of 1:15, place it in an ice water bath, sonicate at 400W for 4min, and let it stand overnight at 4°C to obtain a thyme essential oil / β-cyclodextrin encapsulated nanoemulsion; (7) Add 2 mg / mL glucose oxidase, 10 mg / mL Ala-Gly-Fe3O4@pullulan polysaccharide, 4 mg / mL L-alanine and thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to the citric acid-gelatin composite solution in sequence, wherein the volume ratio of thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to citric acid-gelatin composite solution is 1:8, then add 2% CaCl2 and mix evenly to obtain the composite antibacterial agent; (8) Add 0.4% compound antibacterial agent to the apple juice to be treated, stir at 200 rpm to disperse evenly, and let stand at room temperature for 30 min; (9) After the static period, turn on the magnetic induction electric field device with an excitation voltage of 500V, a frequency of 80 kHz, a field strength of 80 V / cm, and an induced current density of 0.2A / cm. 2 Process for 40 seconds to obtain sterilized apple juice.

[0027] Comparative Example 1 The difference between this comparative example and Example 10 is that Ala-Gly-Fe3O4@pullulan was not added, as detailed below: A method for sterilizing liquid food based on the synergistic effect of magnetic induction electric field and composite antibacterial agent includes the following steps: (1) Dissolve gelatin in water and stir at 60°C until homogeneous to obtain a 10% gelatin solution; (2) Add citric acid to the gelatin solution, with a mass ratio of citric acid to gelatin of 1:5, and react at 60℃ for 4 hours to obtain a citric acid-gelatin composite solution; (3) Dissolve β-cyclodextrin in water and stir at 65°C to prepare a β-cyclodextrin solution with a concentration of 8%; then mix thyme essential oil and Tween 80 at a mass ratio of 4:1 by vortexing to obtain an oil phase mixture; finally, add the oil phase mixture dropwise to the β-cyclodextrin solution at a high speed of 10000rpm with a volume ratio of 1:15, place it in an ice water bath, sonicate at 400W for 4min, and let it stand overnight at 4°C to obtain a thyme essential oil / β-cyclodextrin encapsulated nanoemulsion; (4) Add 2 mg / mL glucose oxidase, 4 mg / mL L-alanine and thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to the citric acid-gelatin composite solution in sequence, wherein the volume ratio of thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to citric acid-gelatin composite solution is 1:8, then add 2% CaCl2 and mix evenly to obtain the composite antibacterial agent; (5) Add 0.4% compound antibacterial agent to the apple juice to be treated, stir at 200 rpm to disperse evenly, and let stand at room temperature for 30 min; (6) After the static period, turn on the magnetic induction electric field device with an excitation voltage of 500V, a frequency of 80kHz, an electric field strength of 80V / cm, and an induced current density of 0.2A / cm. 2 Process for 40 seconds to obtain sterilized apple juice.

[0028] Comparative Example 2 The difference between this comparative example and Example 10 is that L-alanine was not added, as detailed below: A method for sterilizing liquid food based on the synergistic effect of magnetic induction electric field and composite antibacterial agent includes the following steps: (1) Fe3O4 nanoparticles were mixed with a 3% pullulan polysaccharide solution and stirred at 500 rpm for 2 h to obtain Fe3O4@pullulan polysaccharide dispersion; (2) Add 0.3M ethylenediamine to the Fe3O4@pullulan polysaccharide dispersion, react at pH 8 and 60℃ for 5 h to obtain aminated Fe3O4@pullulan polysaccharide; (3) Mix aminated Fe3O4@pulllan polysaccharide with 4 mg / mL Ala-Gly solution at a volume ratio of 1:2 and stir at room temperature for 20 h to obtain Ala-Gly-Fe3O4@pulllan polysaccharide; (4) Dissolve gelatin in water and stir at 60°C until homogeneous to obtain a 10% gelatin solution; (5) Add citric acid to the gelatin solution, with a mass ratio of citric acid to gelatin of 1:5, and react at 60°C for 4 hours to obtain a citric acid-gelatin composite solution; (6) Dissolve β-cyclodextrin in water and stir at 65°C to prepare a β-cyclodextrin solution with a concentration of 8%; then mix thyme essential oil and Tween 80 at a mass ratio of 4:1 by vortexing to obtain an oil phase mixture; finally, add the oil phase mixture dropwise to the β-cyclodextrin solution at a high speed of 10000rpm with a volume ratio of 1:15, place it in an ice water bath, sonicate at 400W for 4min, and let it stand overnight at 4°C to obtain a thyme essential oil / β-cyclodextrin encapsulated nanoemulsion; (7) Add 2 mg / mL glucose oxidase, 10 mg / mL Ala-Gly-Fe3O4@pullulan polysaccharide and thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to the citric acid-gelatin composite solution in sequence, wherein the volume ratio of thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to citric acid-gelatin composite solution is 1:8, then add 2% CaCl2 and mix evenly to obtain the composite antibacterial agent; (8) Add 0.4% compound antibacterial agent to the apple juice to be treated, stir at 200 rpm to disperse evenly, and let stand at room temperature for 30 min; (9) After the static period, turn on the magnetic induction electric field device with an excitation voltage of 500V, a frequency of 80kHz, a field strength of 80V / cm, and an induced current density of 0.2A / cm. 2 Process for 40 seconds to obtain sterilized apple juice.

[0029] Comparative Example 3 The difference between this comparative example and Example 10 is that the thyme essential oil / β-cyclodextrin-encapsulated nanoemulsion was not added, as detailed below: A method for sterilizing liquid food based on the synergistic effect of magnetic induction electric field and composite antibacterial agent includes the following steps: (1) Fe3O4 nanoparticles were mixed with a 3% pullulan polysaccharide solution and stirred at 500 rpm for 2 h to obtain Fe3O4@pullulan polysaccharide dispersion; (2) Add 0.3M ethylenediamine to the Fe3O4@pullulan polysaccharide dispersion, react at pH 8 and 60℃ for 5 h to obtain aminated Fe3O4@pullulan polysaccharide; (3) Mix aminated Fe3O4@pulllan polysaccharide with 4 mg / mL Ala-Gly solution at a volume ratio of 1:2 and stir at room temperature for 20 h to obtain Ala-Gly-Fe3O4@pulllan polysaccharide; (4) Dissolve gelatin in water and stir at 60°C until homogeneous to obtain a 10% gelatin solution; (5) Add citric acid to the gelatin solution, with a mass ratio of citric acid to gelatin of 1:5, and react at 60°C for 4 hours to obtain a citric acid-gelatin composite solution; (6) Add 2 mg / mL glucose oxidase, 10 mg / mL Ala-Gly-Fe3O4@pullulan polysaccharide and 4 mg / mL L-alanine to the citric acid-gelatin composite solution in sequence, then add 2% CaCl2 and mix well to obtain the composite antibacterial agent. (7) Add 0.4% compound antibacterial agent to the apple juice to be treated, stir at 200 rpm to disperse evenly, and let stand at room temperature for 30 min; (8) After the static period, turn on the magnetic induction electric field device with an excitation voltage of 500V, a frequency of 80kHz, a field strength of 80V / cm, and an induced current density of 0.2A / cm. 2 Process for 40 seconds to obtain sterilized apple juice.

[0030] Comparative Example 4 The difference between this comparative example and Example 10 is that a magnetic induction electric field was not used, as detailed below: A method for sterilizing liquid food based on the synergistic effect of magnetic induction electric field and composite antibacterial agent includes the following steps: (1) Fe3O4 nanoparticles were mixed with a 3% pullulan polysaccharide solution and stirred at 500 rpm for 2 h to obtain Fe3O4@pullulan polysaccharide dispersion; (2) Add 0.3M ethylenediamine to the Fe3O4@pullulan polysaccharide dispersion, react at pH 8 and 60℃ for 5 h to obtain aminated Fe3O4@pullulan polysaccharide; (3) Mix aminated Fe3O4@pulllan polysaccharide with 4 mg / mL Ala-Gly solution at a volume ratio of 1:2 and stir at room temperature for 20 h to obtain Ala-Gly-Fe3O4@pulllan polysaccharide; (4) Dissolve gelatin in water and stir at 60°C until homogeneous to obtain a 10% gelatin solution; (5) Add citric acid to the gelatin solution, with a mass ratio of citric acid to gelatin of 1:5, and react at 60°C for 4 hours to obtain a citric acid-gelatin composite solution; (6) Dissolve β-cyclodextrin in water and stir at 65°C to prepare a β-cyclodextrin solution with a concentration of 8%; then mix thyme essential oil and Tween 80 at a mass ratio of 4:1 by vortexing to obtain an oil phase mixture; finally, add the oil phase mixture dropwise to the β-cyclodextrin solution at a high speed of 10000rpm with a volume ratio of 1:15, place it in an ice water bath, sonicate at 400W for 4min, and let it stand overnight at 4°C to obtain a thyme essential oil / β-cyclodextrin encapsulated nanoemulsion; (7) Add 2 mg / mL glucose oxidase, 10 mg / mL Ala-Gly-Fe3O4@pullulan polysaccharide, 4 mg / mL L-alanine and thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to the citric acid-gelatin composite solution in sequence, wherein the volume ratio of thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to citric acid-gelatin composite solution is 1:8, then add 2% CaCl2 and mix evenly to obtain the composite antibacterial agent; (8) Add 0.4% compound antibacterial agent to the apple juice to be treated, stir at 200 rpm to disperse evenly, and let stand at room temperature for 30 minutes to obtain sterilized apple juice.

[0031] Comparative Example 5 The difference between this comparative example and Example 10 is that only a magnetically induced electric field is used, as detailed below: The apple juice to be processed was placed in a magnetic induction electric field device with an excitation voltage of 500V, a frequency of 80kHz, an electric field strength of 80V / cm, and an induced current density of 0.2A / cm. 2 Process for 40 seconds to obtain sterilized apple juice.

[0032] Performance testing: (1) Sterilization rate Refer to the national standard GB 4789.2-2022, "National Food Safety Standard - Microbiological Examination of Food - Determination of Total Colony Count".

[0033] Take liquid food samples before and after treatment, perform appropriate serial dilutions, spread them on plate counting agar, incubate at 37°C for 48 hours, and count the samples. Calculate the sterilization rate using the following formula: Sterilization rate (%) = (1-N / N0) × 100% In the formula: N0 and N are the total number of colonies before and after treatment, respectively.

[0034] Table 1. Sterilization rate of liquid foods prepared in Examples 1-10 and Comparative Examples 1-5

[0035] As shown in Table 1, Example 10 exhibited the best bactericidal effect, with a bactericidal rate of 98.2%, fully demonstrating the powerful synergistic bactericidal effect between the magnetic induction electric field and the composite antibacterial agent. In contrast, the bactericidal rates of Comparative Examples 1-5 were significantly lower than those of the Examples. This indicates that the absence of any key component, such as any of the components in Ala-Gly-Fe3O4@pullulan polysaccharide, thyme essential oil / β-cyclodextrin encapsulated nanoemulsion, or magnetic induction electric field, would lead to a reduction in the bactericidal effect.

[0036] (2) Spore-killing effect Bacillus subtilis spores were added to the liquid food to be processed to prepare a sample solution containing bacterial spores (spore concentration of 10). 6 (CFU / mL), and then sterilization was carried out sequentially using the sterilization methods of Examples 1-10 and Comparative Examples 1-5. The sterilization effect was expressed as logN0 / N t (CFU / mL) indicates the sterilization logarithm.

[0037] Table 2. Spore-killing effect of liquid foods prepared in Examples 1-10 and Comparative Examples 1-5

[0038] As shown in Table 2, the number of Bacillus subtilis spores in Example 10 decreased by 6.9 log values, meeting the requirements for commercial sterility, while the logN0 / N ratio of Comparative Examples 1-5 was significantly lower. t The size is significantly smaller than that of the previous example, indicating that the synergistic effect of the magnetic induction electric field and the composite antibacterial agent has a significant effect on killing spores in liquid food.

[0039] (3) Turbidity The sterilized apple juice prepared in Example 10 and Comparative Examples 1-5 was selected, gently shaken, and poured into a turbidimeter-specific sample bottle. The turbidimeter was calibrated and the readings were taken. The average value was calculated after three measurements.

[0040] Table 3. Turbidity of apple juice prepared in Example 10 and Comparative Examples 1-5

[0041] Turbidity is a key indicator for evaluating the physical stability, sensory quality, and process effectiveness of liquid foods after sterilization. Table 3 shows that Example 10 showed a slight increase in turbidity compared to the control group. This is because the addition of the composite antibacterial agent introduced some microscopic particles, which were uniformly dispersed in the juice, increasing light scattering. However, the system stability was good, and the particles did not aggregate or settle. Comparative Example 1 (no magnetic particles), Comparative Example 2 (lacking L-alanine), and Comparative Example 3 (lacking nanoemulsion) had little impact on turbidity. However, Comparative Example 4 showed that the absence of a magnetically induced electric field caused the entire synergistic release mechanism to fail. The components in the composite antibacterial agent (especially gelatin microspheres and nanoemulsion) failed to be triggered for release as designed, potentially leading to abnormal swelling, aggregation, or local precipitation in an acidic environment, thus significantly increasing light scattering. Furthermore, drastic changes in local pH could cause pectin or protein denaturation and aggregation in the juice, further increasing turbidity. Comparative Example 5 demonstrated that simple magnetically induced electric field treatment itself did not introduce additional particles or cause material aggregation; the turbidity was almost identical to that of the original apple juice.

[0042] (4) Sensory evaluation The sterilized apple juice prepared in Example 10 and Comparative Examples 1-5 was subjected to sensory evaluation.

[0043] Table 4 Sensory Evaluation Criteria

[0044] Table 5 Sensory Evaluation Results

[0045] As shown in Table 5, Example 10 achieved excellent sensory quality while achieving efficient sterilization; Comparative Examples 1-3 suffered varying degrees of loss in flavor, aroma, or taste due to the lack of a single key component (magnetic particles, L-alanine, essential oil nanoemulsion); Comparative Example 4 did not use a magnetic induction electric field, resulting in a significant decrease in the overall sensory score of the apple juice; Comparative Example 5 only used a magnetic induction electric field, which could maximize the preservation of sensory quality, but could not solve the fundamental problem of sterilization, so the overall sensory score also decreased slightly.

[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the technical solutions of the present invention, shall still fall within the scope of protection of the present invention.

Claims

1. A method for sterilizing liquid food based on the synergistic effect of magnetic induction electric field and composite antibacterial agent, characterized in that, Includes the following steps: S1. Add 0.1-0.5% compound antibacterial agent to the liquid food to be processed, stir at 100-200 rpm to disperse evenly, and let stand at room temperature for 30-60 minutes; S2. After the settling period, turn on the magnetic induction electric field device and process for 10-60 seconds to obtain sterilized liquid food.

2. The method for sterilizing liquid food based on the synergistic effect of magnetic induction electric field and composite antibacterial agent according to claim 1, characterized in that, The preparation steps of the compound antibacterial agent in step S1 are as follows: (1) Dissolve gelatin in water and stir evenly at 50-60℃ to obtain a gelatin solution with a concentration of 8-10%; (2) Add citric acid to the gelatin solution and react at 60-70℃ for 2-4 hours to obtain a citric acid-gelatin composite solution; (3) Dissolve β-cyclodextrin in water and stir at 55-65℃ to prepare a β-cyclodextrin solution with a concentration of 5-10%; then mix thyme essential oil and Tween 80 at a mass ratio of (2-4):1 by vortexing to obtain an oil phase mixture; finally, add the oil phase mixture dropwise to the β-cyclodextrin solution under high-speed shearing at 10000-12000rpm, place it in an ice water bath, sonicate at 400-600W for 2-4min, and let it stand overnight at 4℃ to obtain a thyme essential oil / β-cyclodextrin encapsulated nanoemulsion; (4) Add 1-2 mg / mL glucose oxidase, 5-10 mg / mL Ala-Gly-Fe3O4@pullulan polysaccharide, 2-5 mg / mL L-alanine and thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to the citric acid-gelatin composite solution in sequence, and then add 1-3% CaCl2 and mix evenly to obtain the composite antibacterial agent.

3. The method for sterilizing liquid food based on the synergistic effect of magnetic induction electric field and composite antibacterial agent according to claim 2, characterized in that, In step (2), the mass ratio of citric acid to gelatin is 1:(4-5).

4. The method for sterilizing liquid food based on the synergistic effect of magnetic induction electric field and composite antibacterial agent according to claim 2, characterized in that, In step (3), the volume ratio of the oil phase mixture to the β-cyclodextrin solution is 1:(10-20).

5. The method for sterilizing liquid food based on the synergistic effect of magnetic induction electric field and composite antibacterial agent according to claim 2, characterized in that, The preparation steps of Ala-Gly-Fe3O4@pulllan polysaccharide in step (4) are as follows: Step 1. Mix Fe3O4 nanoparticles with a 1-5% pullulan polysaccharide solution and stir at 400-500 rpm for 1.5-2 hours to obtain Fe3O4@pullulan polysaccharide dispersion; Step 2. Add 0.1-0.5M ethylenediamine to the Fe3O4@pullulan polysaccharide dispersion, react at pH 8-9 and 50-60℃ for 4-6 hours to obtain aminated Fe3O4@pullulan polysaccharide; Step 3. Mix aminated Fe3O4@pullulan with 1-5 mg / mL Ala-Gly solution at a volume ratio of 1:(1-3) and stir at room temperature for 12-24 h to obtain Ala-Gly-Fe3O4@pullulan.

6. The method for sterilizing liquid food based on the synergistic effect of magnetic induction electric field and composite antibacterial agent according to claim 2, characterized in that, In step (4), the volume ratio of thyme essential oil / β-cyclodextrin encapsulated nanoemulsion to citric acid-gelatin composite solution is 1:(5-10).

7. The method for sterilizing liquid food based on the synergistic effect of magnetic induction electric field and composite antibacterial agent according to claim 1, characterized in that, The parameters of the magnetic induction electric field in step S2 are: excitation voltage of 500-800V, frequency of 50-100kHz, field strength of 50-100 V / cm, and induced current density of 0.1-0.3A / cm. 2 .

8. The method for sterilizing liquid food based on the synergistic effect of magnetic induction electric field and composite antibacterial agent according to claim 1, characterized in that: The liquid foods include fruit juice, vegetable juice, and milk.

Images