Low-temperature microencapsulation processing method of pet food

Abstract

The invention relates to the technical field of pet food processing, and particularly discloses a pet food low-temperature microencapsulation processing method which comprises the following steps: (a) vacuum low-temperature rolling and permeating; (b) carrying out microwave-ultraviolet synergistic sterilization; (c) freezing and micro-crushing; (d) embedding the two-phase micro-capsule; and (e) gradient drying: during the production of the food for old dogs, 0.2% methionine restrictive hydrolysis peptide is added in the step (a); when the high-activity probiotic pet food is produced, the addition amount of the probiotics is greater than or equal to 5 * 10 CFU / g; when the low-sensitivity formula pet food is produced, the enzymolysis time in the step (a) is prolonged to 60 minutes; through six innovations of low-temperature activity protection chain, physicochemical synergistic sterilization, precise embedding control, mild dehydration water control, formula module adaptation and energy precise management, the problems of activity loss, insufficient precision and low energy efficiency in pet food processing are solved; core indexes such as vitamin retention rate, probiotic survival amount, micro-capsule binding force, moisture control precision and the like have outstanding progress, and development of functional pet food is promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of pet food processing, in particular to a low-temperature microencapsulation processing method for pet food. Background Art

[0002] With the development of refined pet nutrition, the global functional pet food market is expected to reach $36.8 billion in 2025. The core demands include: Efficient delivery of active ingredients: Probiotic intestinal survival rate must be greater than 80% (AAFCO standard), and vitamin heat-sensitive loss must be less than 10%; Precise nutrition customization: phosphorus content of kidney disease grain is ≤0.3%, and allergen residue of hypoallergenic grain is ≤100ppm (FEDIAF guidelines); Safety and stability: Commercially sterile (total colony count <10 CFU / g), shelf life ≥18 months.

[0003] However, the existing processing technology has "three contradictions": Contradiction 1: Conflict between sterilization safety and ingredient activity: Thermal sterilization cannot achieve both low temperature and high efficiency; Contradiction 2: The imbalance between encapsulation accuracy and mass production efficiency. The coefficient of variation (CV) of electrostatic spray microcapsule particle size is greater than 15%, resulting in uneven release. Contradiction three: The separation between process universality and formula specificity. Universal processes cannot meet special needs such as kidney disease / probiotics / hypoallergenicity. Summary of the Invention

[0004] The present invention addresses the above-mentioned deficiencies in the prior art and provides a method for low-temperature microencapsulation of pet food. To achieve the above-mentioned objectives, the following technical solutions are provided: The following steps are involved: (a) Vacuum low-temperature tumbling penetration: The raw meat was cut into 5±0.2 mm³ particles, placed in a vacuum tumbling machine, and tumbled for 40 min at a vacuum degree of -0.08 MPa and a temperature of 35-45°C. A composite enzymatic hydrolysate was simultaneously injected, wherein the mass ratio of papain to neutral protease in the composite enzymatic hydrolysate was 1:2, and the total concentration was 0.3%; Among them, the 5mm³ particle size: Experimental verification shows that this size maintains the integrity of meat fibers while increasing the penetration efficiency of the enzymatic hydrolyzate by 40% (compared to 3mm³ over-crushed and 7mm³ uneven penetration); The vacuum tumbling machine adopts an intermittent forward and reverse mode, wherein forward rotation for 10 minutes and reverse rotation for 5 minutes constitute one cycle, with a total of 3 cycles. The composite enzymatic hydrolysate is added with 0.1% trehalose and 0.05% tea polyphenols as heat-sensitive protective agents, and the composite enzymatic hydrolysate is injected in three pulses: 40% at the 0th minute, 30% at the 15th minute, and 30% at the 30th minute. Compound enzymatic hydrolysate formula: Enzyme ratio basis: papain cuts the hydrophobic bonds of proteins, neutral proteases hydrolyze the hydrophilic regions, and the hydrolysis rate increases by 35% at a 1:2 ratio (SDS-PAGE detection shows that small molecule peptides account for 85%). Heat-sensitive protective agent: add 0.1% trehalose (to increase the glass transition temperature of the ingredients) and 0.05% tea polyphenols (to inhibit Maillard reaction browning); Pulse injection strategy: Inject in three times (40%-30%-30%) to avoid excessive enzymatic hydrolysis caused by local high concentration, and improve the hydrolysis uniformity to more than 90%.

[0005] (b) Microwave-UV synergistic sterilization: The product from step (a) is placed in a multi-band microwave field, in which 2450MHz and 915MHz microwaves are alternately irradiated. The 2450MHz microwave (fast heating but shallow penetration) and 915MHz microwave (deep penetration but slow heating) are switched every 30 seconds to overcome the problem of uneven heating of a single frequency. The measured temperature difference between the center and the surface of the material is ≤1.5°C (the temperature difference of traditional single-frequency microwaves is >7°C). At the same time, 254nm ultraviolet rays are combined with spirally arranged lamps to achieve a sterilization intensity distribution uniformity of 95%, and the processing time is 8 minutes. A 16-point fiber optic temperature measurement network constructs a three-dimensional temperature cloud map of the material in real time, dynamically limiting the maximum temperature to ≤50°C. The multi-band microwave field is composed of three independent waveguides, of which the 2450MHz waveguide power is 1.5-2.5kW, the 915MHz waveguide power is 1.0-1.8kW, and the UV irradiation intensity is 120±10μW / cm². Temperature control uses an optical fiber sensor array inserted into the material with a penetration depth of 30-50% of the material thickness to monitor the three-dimensional temperature field inside the material in real time.

[0006] Each sensor unit contains four sets of optical fiber interfaces: The first input optical fiber and the first output optical fiber are used for column-wise signal transmission; The second input optical fiber and the second output optical fiber are used for horizontal signal transmission; Column-wise series connection: Each column of units is connected end to end in series through the first input / output optical fiber and terminated at a dedicated optical transceiver module; Row-wise series connection: Each row of units is connected end to end in series through the second input / output optical fiber and terminated at a dedicated optical transceiver module.

[0007] This avoids the high cost of configuring a separate optical transceiver module for each sensor, achieves precise unit positioning through row and column cross-modulation, and overcomes the limitation of serial arrays that cannot distinguish signal sources.

[0008] (c) Frozen micro-crushing: The sterilized material from step (b) is rapidly frozen to -35°C using liquid nitrogen at a rate of 0.75 kg / kg of raw material. Rapid cooling at a rate of ≥25°C / s forms fine ice crystals (<5 μm), creating a honeycomb-like porous structure (porosity 60-65%) that provides anchor points for microcapsule embedding. The micro-crusher is then operated at 20,000 rpm using a titanium alloy blade (HRC 58-60) with a 0.1 mm blade gap to ensure a particle size of 50-100 μm. During the crushing process, nitrogen gas at -40°C is continuously introduced to maintain a low temperature environment to prevent pre-oxidation and inactivation of the probiotics.

[0009] (d) Dual-phase microencapsulation: The microparticles obtained in step (c) are placed on the receiving electrode of a coaxial electrostatic spray device. A mixed solution containing vitamins and probiotics is used as the core material, and a wall material solution is used as the shell material. The coaxial electrostatic spray device is used to atomize the mixed solution to form core-shell microcapsules. The relative humidity of the environment in which the core-shell microcapsules are formed is ≤30%, which is closed-loop controlled by a dew point sensor. In addition, a 0.1% glacial acetic acid solution is simultaneously atomized and sprayed during the spraying process to induce molecular cross-linking of the gelatin wall material at the isoelectric point (pH≈4.0), resulting in core-shell microcapsules with an average particle size of 80 μm. Under the action of electrostatic force, the microcapsules are deposited on the surface of the microparticles and embedded in their porous structure to obtain a microcapsule-matrix complex.

[0010] Among them, the golden ratio of the wall material solution is: gelatin (film-forming body): pectin (gastric acid barrier): medium-chain triglyceride MCT (moisture barrier layer) = 3:1:1. After in vitro simulation verification, the core material release rate in the gastric fluid environment is <5% within 2 hours; 0.5% nano-titanium dioxide is added to the wall material solution as a light barrier agent.

[0011] The core material is composed of vitamin A, vitamin D, vitamin E and freeze-dried Lactobacillus plantarum powder (≥1×10¹¹ CFU / g), among which the mass ratio of vitamin A, vitamin D and vitamin E is 1:0.2:1.5.

[0012] Precise control of electrostatic spray: Coaxial needle: The inner needle (core material channel) has an inner diameter of 0.3 mm and is used to deliver a mixture containing vitamins and probiotics. The outer needle (shell material channel) has an inner diameter of 0.8 mm and is used to deliver the wall material solution. The high-voltage electric field is applied to the potential difference between the injection unit needle and the receiving plate, with a voltage value of 15 kV. The receiving distance refers to the vertical distance between the tip of the coaxial needle and the receiving plate, which is set to 12 cm. A 1000fps high-speed camera coupled with a convolutional neural network (CNN) algorithm was used to identify the core-shell microcapsule particle size in real time, automatically adjusting the voltage to maintain the microcapsule particle size at 80±5μm and keeping the coefficient of variation (CV) of the microcapsule size ≤5%. Core material protection enhancement: 30nm nano titanium dioxide is added to block ultraviolet rays and reduce the loss of vitamin photolysis.

[0013] (e) Gradient drying: The embedded microcapsule-matrix complexes from step (d) were subjected to gradient drying. The first stage was fluidized bed drying (40°C): a gentle airflow was used to remove surface water, and the moisture content was reduced to 25% over 15 minutes to prevent microcapsule adhesion. The second stage was vacuum microwave drying (30°C): internal bound water was removed by pulsed radiation (on 15 seconds / off 10 seconds) at 30°C and a vacuum of -0.08 MPa in a vacuum microwave drying chamber. The power was 0.8 W / g to prevent local overheating. The third stage was dehumidification drying (25°C): low-temperature dehumidification was performed in a rotary dehumidification drying chamber at 25°C and a dew point of -15°C to a final moisture content of 6%, thereby locking in the stability of the microcapsule structure.

[0014] In the third stage, the NIRS-PLS model was used to control moisture fluctuations to ≤±0.3%. A near-infrared spectrometer (NIRS) was used to scan the materials online, and the moisture content was predicted using a partial least squares regression model (PLS). Model parameters included: wavelength range: 1200-2400nm, number of principal components: 8, and calibration set determination coefficient R²≥0.995. The dehumidifier air volume was controlled based on feedback from the predicted value to ensure that the final moisture fluctuation was ≤±0.3%.

[0015] On the basis of the above, when producing elderly dog ​​food, 0.2% methionine-restricted hydrolyzed peptide is added in step (a), and the core material in step (d) contains 1.0% α-ketoglutaric acid; when producing highly active probiotic pet food: step (d) uses a double-layer wall material: the inner layer is chitosan that dissolves at pH>6.5, and the outer layer is gelatin-pectin, and the amount of probiotics added is ≥5×10¹ 0 CFU / g; When producing hypoallergenic formula pet food: extend the enzymatic hydrolysis time in step (a) to 60 min, and control the degree of hydrolysis DH = 35±2%.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention solves the industry problem of "high loss of heat-sensitive ingredients": it achieves a disruptive breakthrough through a triple low-temperature protection mechanism: during the vacuum tumbling and penetration stage, the enzymatic hydrolysis temperature is strictly controlled below 45°C, thereby improving the retention rate of vitamin precursors; during the microwave-UV synergistic sterilization stage, dual-frequency microwave and UV sterilization are used to greatly improve the survival rate of probiotics; during the gradient drying stage, the three-stage temperature of fluidized bed-vacuum microwave-dehumidification drying decreases step by step, thereby improving the vitamin retention rate of the final product.

[0017] 2. This invention breaks through the bottleneck of the contradiction between "sterilization safety and activity protection". 2450MHz microwaves and 915MHz microwaves alternate every 30 seconds, and cooperate with the 16-point fiber optic temperature field for real-time control, so that the temperature difference between the center and the surface of the material is ≤1.5°C (the temperature difference of traditional single-frequency microwaves is >7°C), eliminating local overheating damage; the ultraviolet lamps are spirally arranged to directly destroy microbial DNA, forming a synergistic effect with the microwave thermal effect, doubling the sterilization efficiency at the same temperature.

[0018] 3. This invention solves the chronic technical problem of "insufficient microcapsule embedding precision" through structural innovation: liquid nitrogen rapid freezing (cooling rate ≥ 25°C / s) forms a honeycomb porous matrix (porosity 62±3%), providing an anchor point for electrostatic embedding; material breakthrough: the wall material has a golden ratio of gelatin-pectin-MCT (3:1:1), and the barrier performance is many times better than that of a single layer of gelatin; 0.1% glacial acetic acid is simultaneously sprayed in to induce gelatin isoelectric point cross-linking, thereby improving the microcapsule-matrix bonding strength and increasing the attachment rate.

[0019] 4. The present invention adopts three-stage gradient drying and mild dehydration (40°C fluidized bed → 30°C vacuum microwave → 25°C dehumidification), which greatly reduces the microcapsule rupture rate and drying crack rate.

[0020] 5. The present invention realizes the unity of "process versatility and formula specificity". In response to the differentiated needs of kidney disease food, probiotic food, and low-allergy food, the present invention solves the customization problem through modular process adaptation and reduces costs.

[0021] 6. Energy saving and consumption reduction are beneficial to sustainability. Liquid nitrogen quick freezing replaces compression refrigeration, and vacuum microwave pulse drying replaces thermal drying. Compared with traditional high-energy consumption processes, energy consumption is reduced through precise energy management to achieve green manufacturing.

[0022] This technical solution systematically solves the difficult problems of "activity loss, insufficient precision, and low energy efficiency" in pet food processing through six major innovations: low-temperature active protection chain, physical and chemical synergistic sterilization, precise encapsulation control, gentle dehydration and water control, formula module adaptation, and precise energy management. It has made outstanding progress in core indicators such as vitamin retention rate, probiotic survival, microcapsule binding force, and moisture control accuracy, and has promoted the development of functional pet food. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a process flow chart of the present invention; Figure 2 This is the timing diagram of enzyme solution pulse injection; Figure 3 is a cross-sectional view of the core-shell microcapsule structure; Figure 4 Flowchart for microcapsule-matrix complex formation; In the figure: 1-core material; 2-wall material; 3-UV barrier layer. DETAILED DESCRIPTION The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0024] Combine Figure 1 、 Figure 2 、 Figure 3 , Example 1: Standard process Ingredients: Chicken breast (protein ≥18%), cut into 5.0 mm³ particles (calibrated with a laser micrometer); (a) Vacuum tumbling penetration; Equipment: Vacuum tumbler (-0.08MPa, 40℃); Parameters: forward 10min / reverse 5min×3 cycles; Enzyme hydrolysate: papain: neutral protease = 1:2 (total concentration 0.3%), containing 0.1% trehalose + 0.05% tea polyphenols; Injection: pulsed (0min: 40%, 15min: 30%, 30min: 30%); Output: Degree of hydrolysis DH=32% (HPLC monitoring); (b) Microwave-UV synergistic sterilization Microwave: 2450MHz (2.0kW) + 915MHz (1.5kW) alternating (30s switching); UV: 254nm, 125μW / cm² (radiometer calibrated); Temperature: Real-time monitoring by optical fiber array, center temperature ≤49.5℃ (3D cloud map); Sterilization effect: total colony count decreased by 5.2 log CFU / g; (c) Cryo-microfragmentation Liquid nitrogen freezing: cooling rate 28°C / s (verified by infrared thermal imaging camera); Crushing: cross titanium alloy cutter head (HRC 59), 20,000 rpm, nitrogen gas at -40°C (oxygen content ≤ 0.5%); Microparticles: particle size D90 = 95 μm (laser diffraction method); (d) Biphasic microencapsulation, e.g. Figure 4 As shown, Core material 1: Vitamin A / D / E (1:0.2:1.5) + Lactobacillus plantarum (≥1×10¹¹ CFU / g); Wall material 2: gelatin-pectin-MCT = 3:1:1, containing 0.5% nano-TiO2 (30nm) to form UV shielding layer 3; Electrostatic spray: voltage 15kV, high-speed camera + CNN algorithm dynamic voltage regulation (particle size 80±3μm, CV=3.8%); Simultaneously spray 0.1% glacial acetic acid to induce gelatin cross-linking (FTIR verification of amide bond peak 1630 cm⁻¹); Composite: microcapsule embedding depth ≥55 μm (SEM), binding force 42 nN (AFM); (e) Gradient drying Stage 1: 40°C fluidized bed (1.2 m / s) → moisture content 25% (15 min); Stage 2: 30°C vacuum microwave (pulse on 15s / off 10s) → moisture content 8% (power density 0.8W / g); Stage 3: Dehumidification at 25°C (dew point -15°C) → final moisture 6.0±0.3% (NIRS-PLS model control); Example 2: Kidney disease food for elderly dogs Recipe Adjustment: Step (a): adding 0.2% methionine-restricted hydrolyzed peptide; Step (d): The core material contains 1.0% α-ketoglutaric acid, and the voltage is increased to 18kV (wall thickness 12.1μm). Final product specifications: Phosphorus content: 0.28% (dry basis); Degree of protein hydrolysis: DH=36% (HPLC); Example 3: Highly active probiotic food Recipe Adjustment: Step (d): Double-layer wall material: inner layer chitosan (92% deacetylation, pH 6.8 dissolution), outer layer gelatin-pectin; Probiotics added: 5.3×10¹ 0 CFU / g; Lyophilization protective agent: trehalose: inulin = 1:2 (accounting for 30% of the core material mass); Effect verification: Accelerated test (40℃ / 75%RH, 3 months): viable bacteria survival rate 91.2%; Intestinal fluid release rate: ≤5% in 2 hours, ≥90% in 6 hours (in vitro simulation); Example 4: Hypoallergenic Formula Recipe Adjustment: Step (a): Extend the enzymatic hydrolysis time to 60 min and control DH=35±2%; Allergen detection: molecular weight> 10kDa protein residue ≤ 45ppm; allergenicity evaluation: Skin allergy test (guinea pig): positive rate 4%; Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A low-temperature microencapsulation method for pet food, characterized by: The following steps are involved: (a) Vacuum low-temperature tumbling penetration: The raw meat was cut into 5±0.2 mm³ particles, placed in a vacuum tumbling machine, and tumbled for 40 min at a vacuum degree of -0.08 MPa and a temperature of 35-45°C. A composite enzymatic hydrolysate was simultaneously injected, wherein the composite enzymatic hydrolysate contained papain and neutral protease in a mass ratio of 1:2, with a total concentration of 0.3%; (b) Microwave-UV synergistic sterilization: The product from step (a) is placed in a multi-band microwave field, wherein 2450 MHz and 915 MHz microwaves are alternately irradiated, and 254 nm UV irradiation is combined. The treatment time is 8-10 min, and the center temperature of the material is controlled to be ≤50°C; (c) Freezing micro-crushing: The sterilized material from step (b) was rapidly frozen to -35°C using liquid nitrogen to form a porous structure, and then pulverized into particles of 50-100 μm in a high shear micro-crusher at 20,000 rpm; (d) Dual-phase microencapsulation: The microparticles obtained in step (c) are placed in a coaxial electrostatic spray device. A mixture containing vitamins and probiotics is used as the core material, and a wall material solution is used as the shell material. The coaxial electrostatic spray device is used to atomize the core-shell microcapsules. The obtained core-shell microcapsules have an average particle size of 80 μm. A 1000 fps high-speed camera coupled with a convolutional neural network algorithm is used to identify the particle size of the core-shell microcapsules in real time. When the particle size deviates from 80±5 μm, the voltage of the coaxial electrostatic spray device is dynamically adjusted. Under the action of the electrostatic force, the core-shell microcapsules are deposited on the surface of the microparticles and embedded in the porous structure thereof, thereby producing a microcapsule-matrix complex. (e) Gradient drying: The embedded microcapsule-matrix complexes of step (d) were subjected to gradient drying treatment, including the following steps: first, drying in a fluidized bed dryer at 40°C and a wind speed of 1.2 m / s to a moisture content of 25%; second, pulse drying in a vacuum microwave drying chamber at 30°C and a vacuum degree of -0.08 MPa to a moisture content of 8%; and third, dehumidification and drying in a rotary dehumidification drying chamber at 25°C and a dew point temperature of -15°C to a final moisture content of 6%.

2. The low-temperature microencapsulation method for pet food according to claim 1, wherein: The vacuum tumbling machine adopts an intermittent forward and reverse mode, wherein forward rotation for 10 minutes and reverse rotation for 5 minutes constitute one cycle, with a total of 3 cycles. 0.1% trehalose and 0.05% tea polyphenols are added to the composite enzymatic hydrolysate as heat-sensitive protective agents, and the composite enzymatic hydrolysate is injected in three pulses: 40% at the 0th minute, 30% at the 15th minute, and 30% at the 30th minute.

3. The low-temperature microencapsulation method for pet food according to claim 1, wherein: The multi-band microwave field in step (b) is composed of three sets of independent waveguides, wherein the 2450MHz waveguide power is 1.5-2.5kW, the 915MHz waveguide power is 1.0-1.8kW, the ultraviolet irradiation intensity is 120±10μW / cm², and the temperature control adopts an optical fiber sensor array inserted into the material to monitor the three-dimensional temperature field inside the material in real time.

4. The low-temperature microencapsulation method for pet food according to claim 1, wherein: The liquid nitrogen cooling rate in step (c) is ≥25°C / s, the high shear crusher is equipped with a cross-shaped titanium alloy blade head with a blade gap of 0.1 mm, and -40°C nitrogen is continuously introduced during the crushing process to maintain a low temperature environment.

5. The low-temperature microencapsulation method for pet food according to claim 1, wherein: 0.5% nano-titanium dioxide is added to the wall material solution in step (d) as a light barrier agent. The core material is composed of vitamin A, vitamin D, vitamin E and plant lactobacillus freeze-dried powder, wherein the mass ratio of vitamin A, vitamin D and vitamin E is 1:0.2:1.

5.

6. The low-temperature microencapsulation method for pet food according to claim 1, wherein: The drying time of the first stage in step (e) is 15±1 min; the working cycle of the second stage is irradiation for 15 s and power off for 10 s, the power density is 0.8 W / g, and the air flow speed in the third stage is 0.5 m / s.

7. The low-temperature microencapsulation method for pet food according to claim 1, wherein: In step (d), 0.1% glacial acetic acid solution is simultaneously atomized and sprayed during the spraying process to induce molecular cross-linking of the gelatin wall material at the isoelectric point.

8. The low-temperature microencapsulation method for pet food according to claim 1, wherein: When producing elderly dog ​​food, 0.2% methionine-restricted hydrolyzed peptide is added in step (a), and the core material in step (d) contains 1.0% α-ketoglutaric acid; when producing highly active probiotic pet food: the amount of probiotics added is ≥5×10¹ 0 CFU / g; When producing hypoallergenic formula pet food: the enzymatic hydrolysis time in step (a) is extended to 60 min.

9. The low-temperature microencapsulation method for pet food according to claim 1, wherein: In the step (d), the wall material solution comprises gelatin, pectin and medium chain triglycerides, and the mass ratio of the three is 3:1:

1.

10. The low-temperature microencapsulation method for pet food according to claim 1, characterized in that: The third stage in step (e) controls the moisture fluctuation to ≤±0.3% through the NIRS-PLS model.

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