Preparation process of fruit and vegetable ultra-micro powder by differential pressure pretreatment coupled with gradient enzymolysis

Abstract

The application discloses a fruit and vegetable superfine powder preparation process of differential pressure pretreatment coupled with gradient enzymolysis, which comprises raw material pretreatment, mild transient pressure difference cycle wall breaking, gradient composite enzymolysis, low-temperature drying, crushing and in-situ embedding, and low-temperature vacuum pasteurization. The application solves the problems of insufficient wall breaking, low enzymolysis efficiency, loss of active ingredients caused by high-temperature drying, easy oxidation and moisture absorption of powder, insufficient product stability and the like in traditional fruit and vegetable powder processing, and the prepared fruit and vegetable superfine powder is uniform in particle size, high in active ingredient retention rate and excellent in storage stability, the process flow is simple, the production cost is controllable, and the process is suitable for industrialized large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, specifically relating to a process for preparing ultrafine fruit and vegetable powder, and more particularly to a process for preparing highly active ultrafine fruit and vegetable powder by pressure difference pretreatment coupled with gradient enzymatic hydrolysis and heat pump-microwave combined low-temperature drying. Background Technology

[0002] Fruit and vegetable powder is a powdered product made from fresh fruits or vegetables through processes such as washing, cutting, enzyme inactivation, drying, dehydration, and pulverization. It is rich in nutrients such as polyphenols, flavonoids, vitamins, dietary fiber, minerals, and plant-based active substances, and is one of the important forms of deep processing of fruits and vegetables. According to the type of raw materials, it can be divided into fruit powder, vegetable powder, and compound fruit and vegetable powder; according to the particle size, it can be divided into ordinary fruit and vegetable powder and ultrafine fruit and vegetable powder. Compared with traditional fresh fruits and vegetables, fruit and vegetable powder has a lower moisture content and smaller volume-to-weight ratio, making it easier to store, transport, and preserve for a long time. It can effectively extend the utilization period of fruit and vegetable raw materials, reduce fresh fruit loss, and provide a stable and convenient ingredient form for subsequent food processing.

[0003] Fruit and vegetable ultrafine powder is a micron-sized powder obtained by ultrafine grinding of fruit and vegetable materials, with a particle size typically ranging from 10 to 50 μm. Due to its small particle size and high cell wall breakage rate, it has a large specific surface area, good resolubility, and readily soluble active ingredients such as polyphenols and vitamins, resulting in high bioavailability. It can be directly mixed with water for drinking and can also be used as a functional ingredient in solid beverages, meal replacement powders, baked goods, health products, and other fields, showing broad application prospects.

[0004] Existing methods for preparing ultrafine fruit and vegetable powders typically involve mechanical pulverization or high-temperature drying followed by pulverization. While mechanical pulverization can achieve micron-level particle sizes, it results in low cell wall disruption and limited dissolution of intracellular active ingredients. High-temperature drying easily degrades heat-sensitive components such as polyphenols and vitamins. Although vacuum freeze-drying can better preserve active ingredients, it requires significant equipment investment, has a long cycle time, and high energy consumption. Ultrafine powders have a large specific surface area and high surface energy, making them prone to oxidation, browning, moisture absorption, and clumping during processing and storage. Furthermore, they lack directional stabilization protection, leading to poor product stability. In addition, the dense cell wall structure of fruits and vegetables makes it difficult to fully release intracellular active ingredients during direct pulverization, affecting the retention of powder activity and reconstituted quality.

[0005] CN102138663B discloses a processing method for vitamin-rich fermented nutritional fruit and vegetable powder, which adopts a compound enzyme treatment combined with yeast aerobic fermentation-spray drying process. After the fruit and vegetable juice is hydrolyzed by a compound enzyme of cellulase and pectinase, it is prepared and sterilized, then inoculated with yeast and fermented at 28-32℃ for 40-60 hours. The concentrated liquid is spray dried at 180-200℃ to produce powder. Its shortcomings are that the fermentation cycle is long and the production efficiency is low. The high temperature of spray drying can easily cause the degradation of heat-sensitive vitamins. In addition, it only uses fruit and vegetable juice as substrate and does not utilize the dietary fiber of fruit pulp, resulting in low raw material utilization rate.

[0006] CN118020924A discloses a kale powder with dietary therapeutic effects and its processing method, which adopts vacuum freeze-drying combined with multi-component compound ultra-fine pulverization process; although freeze-drying can retain nutrients, it requires large equipment investment, long cycle and high energy consumption; the co-pulverization of multi-component materials results in large differences in raw material characteristics, poor uniformity of powder particle size, no directional stabilization treatment of active ingredients, and insufficient product stability. Summary of the Invention

[0007] To address the shortcomings of the existing technologies, this invention provides a process for preparing ultrafine fruit and vegetable powders by pressure differential pretreatment coupled with gradient enzymatic hydrolysis. Through gentle instantaneous pressure differential cell disruption, two-stage gradient enzymatic hydrolysis to release nutrients, heat pump-microwave low-temperature drying to preserve vitality and reduce costs, airflow ultrafine pulverization with simultaneous in-situ embedding to prevent agglomeration, and low-temperature vacuum pasteurization to control microorganisms and reduce heat loss, this process achieves a synergistic improvement in nutrient retention, enzymatic hydrolysis and drying efficiency, storage stability, and industrial feasibility.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A process for preparing ultrafine powders of fruits and vegetables by pressure difference pretreatment coupled with gradient enzymatic hydrolysis includes the following steps:

[0010] S1. Raw material pretreatment: Select fresh fruits and vegetables, wash and remove inedible parts, cut into 6-12mm pieces / slices, drain water, and obtain pretreated fruits and vegetables.

[0011] S2. Mild Instantaneous Pressure Difference Cyclic Disruption: Place the pretreated fruit and vegetable materials in an intermittent pressure difference treatment tank, heat it at a uniform rate to 85-92℃, and maintain the temperature and pressure for 4-6 minutes; reduce the pressure inside the tank from 0.3-0.4MPa to atmospheric pressure within 0.5-1.0s to complete one pressure difference disruption cycle; repeat the cycle 3 times, with a 3-minute interval between adjacent cycles, to obtain disrupted fruit and vegetable blocks;

[0012] S3, Gradient compound enzymatic hydrolysis: The cell wall-breaking blocks are pulped to ≤2mm; 0.03%-0.05% pectinase (by weight of the pulp) is added, and the pH is adjusted to 3.9-4.1. Enzymatic hydrolysis is carried out at 46-48℃ for 1 hour; then 0.04%-0.06% cellulase and 0.02%-0.03% hemicellulase are added, and enzymatic hydrolysis is carried out at pH 5.0-5.3 and 51-53℃ for 2.5 hours; the enzymes are inactivated in an 85℃ water bath for 3 minutes, and the solution is cooled to room temperature to obtain the enzymatic hydrolysate.

[0013] S4. Low-temperature drying: Spread the slurry 6-9mm in a tray, pre-dry with a heat pump at 45-55℃ until the moisture content is 18%-22%, configure the microwave power according to the material amount of 0.2-0.5kW / kg, use pulse intermittent heating (heating for 10-20s, intermittent for 5-10s alternating), control the material temperature ≤55℃, and dry until the final moisture content of the material is ≤4.5% to obtain dried fruit and vegetable materials;

[0014] S5. Crushing and In-situ Encapsulation: After coarsely crushing the dried fruits and vegetables to a particle size ≤1mm, feed them into an airflow ultrafine pulverizer. Nitrogen gas is introduced into the pulverizing chamber for slight positive pressure protection. The pulverizing pressure is 0.6-0.8MPa and the classifier frequency is 90-110Hz. Prepare an encapsulation solution with a mass ratio of gum arabic to maltodextrin of 1:2-3 and a solid content of 9%-11%. During the pulverization process, the encapsulation solution is sprayed with high-pressure micro-mist at a spraying rate of 4%-5% of the dry material mass. The ultrafine pulverization is carried out until the powder particle size meets the requirement of D50 of 10-20μm, resulting in in-situ encapsulated ultrafine fruit and vegetable powder.

[0015] S6. Low-temperature vacuum pasteurization: The in-situ embedded fruit and vegetable ultrafine powder is treated at a vacuum degree of 0.08MPa and a temperature of 78-82℃ for 8-12 minutes. After cooling, it is filled with nitrogen and packaged to obtain the finished fruit and vegetable ultrafine powder.

[0016] Furthermore, in step S2, the temperature is uniformly increased to 85-90℃ and held at pressure for 4-6 minutes.

[0017] Further, in step S3, the pectinase activity is ≥30000U / g, the cellulase activity is ≥40000U / g, and the hemicellulase activity is ≥20000U / g.

[0018] Furthermore, in step S4, the preferred parameters for the heat pump pre-drying are: drying temperature 48-52℃, wind speed 3.5m / s, and drying time 4-6h.

[0019] Furthermore, in step S5, spraying is achieved by 2-4 high-pressure atomizing nozzles evenly distributed in the circumferential direction on the inner wall of the crushing chamber, with an atomization pressure of 0.3-0.5MPa and a droplet size of ≤50μm; depending on the moisture content of the material, spraying is performed intermittently in 2-3 times, with an interval of 20-40s between each spraying.

[0020] Furthermore, in step S6, the preferred parameters for the low-temperature vacuum pasteurization are: vacuum degree 0.08 MPa, sterilization temperature 78-82℃, and processing time 8-12 min.

[0021] Furthermore, the fruit and vegetable ingredients are one or a combination of several of the following: kale, broccoli, radish sprouts, Chinese kale, apple, carrot, pumpkin, spinach, mango, strawberry, blueberry, mulberry, kiwi, and tomato.

[0022] The present invention has the following beneficial effects:

[0023] (1) Instantaneous pressure difference pretreatment has the combined effect of cell wall disruption and inactivation of endogenous oxidases, inhibiting enzymatic browning; segmented gradient enzymatic hydrolysis matches the optimal conditions of each enzyme, improves the dissolution rate of active substances, shortens the hydrolysis time, and improves processing efficiency.

[0024] (2) The material is heated at low temperature throughout the heat pump-microwave combined low temperature drying process, and the heat-sensitive components are highly retained. Compared with the freeze drying process, the equipment investment, energy consumption and drying time are significantly reduced, taking into account both product quality and production economy.

[0025] (3) Using nitrogen protection for room temperature pulverization avoids thermal degradation of active ingredients. Combined with intermittent atomization for in-situ film formation, no external anti-caking agent is needed, which effectively reduces the moisture absorption and clumping of powder and improves storage stability.

[0026] (4) Low-temperature vacuum pasteurization can inhibit non-enzymatic browning and ensure microbial safety. The entire line adopts commercial standard equipment, with low investment and is suitable for industrial production of various fruit and vegetable raw materials. Detailed Implementation

[0027] The present invention will be further described below with reference to embodiments and comparative examples. The raw materials, reagents, and equipment used in the following embodiments are all commercially available products. Unless otherwise specified, all steps were performed in accordance with food GMP standards.

[0028] Example 1: A process for preparing ultrafine fruit and vegetable powder using pressure difference pretreatment coupled with gradient enzymatic hydrolysis, comprising the following steps:

[0029] S1. Raw material pretreatment: Select 8kg of fresh kale, wash and remove inedible parts, cut into 8mm pieces, drain water, and obtain pretreated kale material.

[0030] S2. Mild instantaneous pressure difference circulation cell disruption: Place the pretreated material in a 50L intermittent pressure difference treatment tank, heat it to 88℃ at a uniform rate, and maintain the temperature and pressure for 5 minutes; reduce the pressure inside the tank from 0.35MPa to atmospheric pressure within 0.8s, and repeat the cycle 3 times with a 3-minute interval between adjacent cycles.

[0031] S3, Gradient Complex Enzymatic Hydrolysis: The cell wall-breaking blocks are pulped to ≤2mm; 0.04% (by weight of fruit pulp) of pectinase (enzyme activity 30000U / g) is added, and the pH is adjusted to 4.0 with citric acid. Enzymatic hydrolysis is carried out at 47℃ with low-speed stirring (60r / min) for 1 hour. Then, 0.05% cellulase (40000U / g) and 0.025% hemicellulase (20000U / g) are added, and the pH is adjusted to 5.1 with sodium citrate. Enzymatic hydrolysis is carried out at 52℃ with low-speed stirring for 2.5 hours. The enzymes are then inactivated in an 85℃ water bath for 3 minutes, and cooled to room temperature.

[0032] S4. Low-temperature drying: The slurry is spread into a tray to a thickness of 8mm. The heat pump drying temperature is 50℃, the air velocity is 3.5m / s, and the drying time is 5 hours until the material moisture content is 20%. The power is 3.5kW (configured based on a material quantity of 0.35kW / kg), with pulse heating alternating with 15s and intermittent heating with 8s, the material temperature is ≤52℃, and the drying time is 1.5 hours until the final moisture content is 4.2%.

[0033] S5. Crushing and In-situ Encapsulation: After coarsely crushing the dried fruits and vegetables to a particle size ≤1mm, feed them into an airflow ultrafine pulverizer. Nitrogen gas is introduced into the crushing chamber for slight positive pressure protection. The crushing pressure is 0.7MPa, and the classifying wheel frequency is 100Hz. Prepare a composite encapsulation solution in advance: dissolve 12g of gum arabic and 30g of maltodextrin in 420mL of pure water, with a solid content of 10%, and stir until dissolved. During the crushing process, apply the encapsulation solution using high-pressure micro-mist spray, with an application rate of 4.5% of the dry material mass. Continue crushing until the D50 is 12.5μm to obtain in-situ encapsulated ultrafine fruit and vegetable powder.

[0034] S6. Low-temperature vacuum pasteurization: The in-situ embedded kale ultrafine powder is placed into a vacuum sterilization tank, treated at a vacuum degree of 0.08MPa and 80℃ for 10 minutes, and then cooled to room temperature. It is then packaged in an aluminum foil bag filled with nitrogen to obtain the finished kale ultrafine powder.

[0035] Example 2, a process for preparing ultrafine fruit and vegetable powder by pressure difference pretreatment coupled with gradient enzymatic hydrolysis, includes the following steps:

[0036] S1. Raw material pretreatment: Select 5kg of apples (Red Fuji) and 3kg of carrots, wash and remove inedible parts, cut into 10mm cubes, drain water, and obtain pretreated fruit and vegetable materials.

[0037] S2. Mild instantaneous differential pressure circulation cell disruption: Place the pretreated material in a 50L intermittent differential pressure treatment tank, heat it to 85℃ at a uniform rate, and maintain the temperature and pressure for 6 minutes; reduce the pressure inside the tank from 0.30MPa to atmospheric pressure within 1.0s, and repeat the cycle 3 times with a 3-minute interval.

[0038] S3, Gradient Complex Enzymatic Hydrolysis: The cell wall-breaking blocks are pulped to ≤2mm; 0.05% (by weight of the fruit pulp) of pectinase (enzyme activity 30000U / g) is added, and the pH is adjusted to 3.9 with citric acid. Enzymatic hydrolysis is carried out at 48℃ with low-speed stirring (60r / min) for 1 hour. Then, 0.06% (40000U / g) of cellulase and 0.03% (20000U / g) of hemicellulase are added, and the pH is adjusted to 5.3 with sodium citrate. Enzymatic hydrolysis is carried out at 51℃ with low-speed stirring for 2.5 hours. The enzymes are then inactivated in an 85℃ water bath for 3 minutes, and the mixture is cooled to room temperature.

[0039] S4. Low-temperature drying: The slurry is spread into a tray to a thickness of 8mm. The heat pump drying temperature is 52℃, the air velocity is 3.5m / s, and the drying time is 4 hours until the material moisture content is 18%. The power is 4.1kW (configured based on a material quantity of 0.4kW / kg), with pulse heating alternating between 10s and 5s intervals. The material temperature is ≤55℃, and the drying time is 1 hour until the final moisture content is 3.8%.

[0040] S5. Crushing and In-situ Encapsulation: After coarsely crushing the dried fruits and vegetables to a particle size ≤1mm, feed them into an airflow ultrafine pulverizer. Nitrogen gas is introduced into the crushing chamber for slight positive pressure protection. The crushing pressure is 0.8MPa, and the classifying wheel frequency is 110Hz. Prepare a composite encapsulation solution in advance: dissolve 15g of gum arabic and 30g of maltodextrin in 450mL of pure water, with a solid content of 10%, and stir until dissolved. During the crushing process, apply the encapsulation solution using high-pressure micro-mist spray, with an application rate of 5.0% of the dry material mass. Continue crushing until the D50 is 10.8μm to obtain in-situ encapsulated ultrafine fruit and vegetable powder.

[0041] S6. Low-temperature vacuum pasteurization: The in-situ embedded apple-carrot ultrafine powder is placed into a vacuum sterilization tank, treated at a vacuum degree of 0.08MPa and 82℃ for 8 minutes, and then cooled to room temperature. It is then packaged in an aluminum foil bag filled with nitrogen to obtain the finished apple-carrot composite ultrafine powder.

[0042] Example 3, a process for preparing ultrafine fruit and vegetable powder by pressure difference pretreatment coupled with gradient enzymatic hydrolysis, includes the following steps:

[0043] S1. Raw material pretreatment: 6kg of broccoli, wash and remove inedible parts, cut into 10mm pieces, drain water to obtain pretreated broccoli material.

[0044] S2. Mild instantaneous pressure difference circulation cell disruption: Place the pretreated material in a 50L intermittent pressure difference treatment tank, heat it to 90℃ at a uniform rate, and maintain the temperature and pressure for 4 minutes; reduce the pressure in the tank from 0.30MPa to atmospheric pressure within 1.0s, and repeat the cycle 3 times with a 3-minute interval.

[0045] S3, Gradient Complex Enzymatic Hydrolysis: The cell wall-breaking blocks are pulped to ≤2mm; 0.05% of the pulp mass of pectinase (enzyme activity 30000U / g) is added, and the pH is adjusted to 4.1 with citric acid. Enzymatic hydrolysis is carried out at 46℃ with low-speed stirring (60r / min) for 1 hour. Then, 0.04% cellulase (40000U / g) and 0.02% hemicellulase (20000U / g) are added, and the pH is adjusted to 5.0 with sodium citrate. Enzymatic hydrolysis is carried out at 53℃ with low-speed stirring for 2.5 hours. The enzymes are then inactivated in an 85℃ water bath for 3 minutes, and the mixture is cooled to room temperature.

[0046] S4. Low-temperature drying: Slurry spread in trays 7mm thick, heat pump drying temperature 48℃, wind speed 3.5m / s, drying for 5 hours until the material moisture content is 20%. Power 1.8kW (configured based on material quantity 0.3kW / kg), pulse heating for 20s / intermittent 10s alternating, material temperature ≤55℃, drying for 2 hours until the final moisture content is 4.0%.

[0047] S5. Crushing and In-situ Encapsulation: The dried fruit and vegetable materials are coarsely crushed to a particle size ≤1mm and then fed into an airflow ultrafine pulverizer. Nitrogen gas is introduced into the crushing chamber for slight positive pressure protection. The crushing pressure is 0.68MPa and the classifying wheel frequency is 100Hz. A composite encapsulation solution is prepared in advance: 10g of gum arabic and 20g of maltodextrin are dissolved in 300mL of pure water, with a solid content of 10%, and stirred until dissolved. During the crushing process, the encapsulation solution is sprayed using high-pressure micro-mist, with a spraying amount of 4.0% of the dry material mass. Crushing continues until the D50 is 11.6μm, yielding in-situ encapsulated broccoli ultrafine powder.

[0048] S6. Low-temperature vacuum pasteurization: The in-situ embedded broccoli ultrafine powder is placed into a vacuum sterilization tank, treated at a vacuum degree of 0.08MPa and 78℃ for 12 minutes, and then cooled to room temperature. It is then packaged in an aluminum foil bag filled with nitrogen to obtain the finished broccoli ultrafine powder.

[0049] Comparative Example 1: Pretreatment without instantaneous pressure difference for cell disruption (other aspects are the same as in Example 1):

[0050] Take the same batch of kale as in Example 1, omit step S2 (instantaneous pressure difference cell disruption pretreatment), directly pulp the cut material and perform two-stage gradient enzymatic hydrolysis, and the remaining steps and parameters are the same as in Example 1.

[0051] Comparative Example 2: Single-stage compound enzymatic hydrolysis (no segmented enzymatic hydrolysis, otherwise the same as in Example 1):

[0052] Take the same batch of kale as in Example 1. Step S2, instantaneous pressure difference cell wall disruption pretreatment, is the same as in Example 1, but step S3 is changed to a one-time compound enzymatic hydrolysis: simultaneously add 0.04% pectinase, 0.05% cellulase, and 0.025% hemicellulase, compromise pH 4.6, temperature 50℃, and inactivate the enzyme after 3.5h of enzymatic hydrolysis. The remaining steps and parameters are the same as in Example 1.

[0053] Comparative Example 3: Ultrafine pulverization followed by external embedding (non-in-situ embedding, otherwise consistent with Example 1):

[0054] Take the same batch of kale as in Example 1. Steps S1-S4 are the same as in Example 1. Step S5 is changed to: first, under the same conditions, ultrafinely pulverize to D50=12.5μm (without spraying the embedding liquid during the pulverization process), then mix the ultrafine powder and the wall material powder (gum arabic: maltodextrin = 1:2.5, with a total addition amount of 5% of the mass of the ultrafine powder) in a V-type mixer for 30 minutes. The remaining steps are the same as in Example 1.

[0055] Comparative Example 4: Hot air drying (without heat pump-microwave combination, otherwise the same as Example 1):

[0056] Step S4 is changed to: spread the enzyme-inactivating slurry on a tray, dry it with hot air at 80°C and 3m / s until the moisture content is ≤5%, and the remaining steps are the same as in Example 1.

[0057] Detection method:

[0058] Cell wall disruption rate: The counting method was used with optical microscopy. A small amount of the disrupted material (after step S2 and before enzymatic digestion in step S3) was diluted and prepared into a slide. The number of intact cells and disrupted cells was counted under a microscope. Cell wall disruption rate = number of disrupted cells / total number of cells × 100%.

[0059] Juice yield: Weigh the pretreated material mass M1, filter and collect the juice after enzymatic hydrolysis. Juice yield = juice mass / M1 × 100%.

[0060] Total polyphenol release enhancement rate: The total polyphenol content of the enzymatic hydrolysate was determined by the Folin-Ciocalteu method; with the unbroken directly enzymatically hydrolyzed sample as the benchmark, the total polyphenol release enhancement rate = (sample polyphenol content − benchmark polyphenol content) / benchmark polyphenol content × 100%.

[0061] Vitamin C retention rate: The VC content in the finished product was determined by 2,6-dichlorophenolindophenol titration; with the VC content of the slurry before drying as the initial value, the vitamin C retention rate was calculated as: (VC content of finished product / initial VC content) × 100%.

[0062] D50 particle size: The volume average particle size D50 of the powder was obtained by dry laser particle size analyzer.

[0063] 30-day agglomeration rate: The powder was placed in a sealed chamber at 25℃ and 75% relative humidity for 30 days; the agglomeration rate was calculated by sieving using a 100-mesh sieve with vibration, and the agglomeration rate was calculated as: mass of residual agglomerates on the sieve / total mass of the sample × 100%.

[0064] The results are shown in Table 1 below:

[0065] Table 1

[0066] Cell wall breakage rate (%) 93.2 87.3 91.8 45.6 93.0 92.9 93.2 Juice yield (%) 81.2 83.6 79.6 71.5 75.3 81.2 81.2 Total polyphenol release enhancement rate (%) 43.8 50.6 47.3 19.5 26.8 43.8 43.5 Vitamin C retention rate (%) 83.8 86.8 84.5 82.6 83.8 83.5 43.8 D50 particle size (μm) 12.5 10.8 11.6 16.8 13.6 12.8 14.1 30-day clumping rate (%) 5.2 4.8 4.9 10.6 5.2 18.5 5.2

[0067] As shown in Table 1, this invention effectively enhances the extraction and release of nutrients through a synergistic technology of gentle instantaneous pressure differential cell disruption and gradient enzymatic hydrolysis. The combined heat pump-microwave low-temperature drying process maximizes the retention of active nutrients while controlling production energy consumption and costs. Simultaneous in-situ encapsulation via ambient temperature airflow ultrafine pulverization improves moisture absorption and agglomeration defects while preparing ultrafine powders. Low-temperature vacuum pasteurization achieves low-oxygen, gentle sterilization, resulting in superior nutrient retention compared to high-temperature infrared sterilization. Nitrogen-filled packaging further extends shelf life. The various processes in this invention work synergistically, utilize general-purpose industrial equipment throughout, and are cost-effective, facilitating industrial-scale promotion by food companies. This invention possesses significant substantive features and represents a remarkable advancement.

[0068] The above embodiments are merely illustrative of the technical solutions of the present invention and are not intended to limit the invention. The process conditions, raw material types, and test data mentioned in the specification are only used to assist in understanding the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims; equivalent substitutions, reasonable adjustments to parameters, and simple modifications to the structure or process made by those skilled in the art based on the disclosed concept of the present invention without inventive effort are all within the scope of protection of the present invention.

Claims

1. A process for preparing ultrafine fruit and vegetable powder using pressure difference pretreatment coupled with gradient enzymatic hydrolysis, characterized in that, Includes the following steps: S1. Raw Material Pretreatment: Select fresh fruits and vegetables, wash and remove inedible parts, cut into 6-12mm pieces / slices, drain water, and obtain pretreated fruit and vegetable materials; S2. Mild Instantaneous Pressure Difference Cyclic Disruption: Place the pretreated fruit and vegetable materials in an intermittent pressure difference treatment tank, heat to 85-92℃ at a uniform rate, and maintain constant temperature and pressure for 4-6 minutes; reduce the pressure inside the tank from 0.3-0.4MPa to atmospheric pressure within 0.5-1.0s, completing one pressure difference disruption cycle; repeat 3 cycles, with a 3-minute interval between adjacent cycles, to obtain disrupted fruit and vegetable blocks; S3. Gradient Compound Enzymatic Hydrolysis: Pulp the disrupted blocks to ≤2mm; add 0.03%-0.05% pectinase by weight of the fruit pulp, adjust the pH to 3.9-4.1, and hydrolyze at 46-48℃ for 1 hour; then add 0.04%-0.06% cellulase and 0.02%-0.03% hemicellulase, pH... 5.0-5.3, 51-53℃ for 2.5h enzymatic hydrolysis; 85℃ water bath for 3min enzyme inactivation, cooling to room temperature to obtain enzymatic hydrolysate; S4, low-temperature drying: spread the hydrolysate 6-9mm in a tray, pre-dry with a heat pump at 45-55℃ to a moisture content of 18%-22%, microwave power configured according to material quantity of 0.2-0.5kW / kg, using pulse intermittent heating (heating for 10-20s, intermittent for 5-10s), controlling the material temperature ≤55℃, drying to a final moisture content ≤4.5%, obtaining dried fruit and vegetable material; S5, crushing and in-situ embedding: coarsely crush the dried fruit and vegetable material to a particle size ≤1mm. The powder is then fed into an airflow ultrafine pulverizer. Nitrogen gas is introduced into the pulverizing chamber for slight positive pressure protection. The pulverizing pressure is 0.6-0.8 MPa and the classifier frequency is 90-110 Hz. An encapsulation solution with a mass ratio of gum arabic to maltodextrin of 1:2-3 and a solid content of 9%-11% is prepared. During the pulverization process, the encapsulation solution is sprayed with high-pressure micro-mist at a rate of 4%-5% of the dry material mass. The powder is pulverized until the particle size meets the following requirement: D50 is 10-20 μm, resulting in in-situ encapsulated fruit and vegetable ultrafine powder. S6, Low-temperature vacuum pasteurization: The in-situ encapsulated fruit and vegetable ultrafine powder is treated at a vacuum degree of 0.08 MPa and a temperature of 75-85℃ for 6-15 minutes. After cooling, it is packaged with nitrogen to obtain the finished fruit and vegetable ultrafine powder.

2. The process for preparing ultrafine fruit and vegetable powder by pressure difference pretreatment coupled with gradient enzymatic hydrolysis according to claim 1, characterized in that, In step S2, the temperature is raised to 85-90℃ and held at pressure for 4-6 minutes.

3. The process for preparing ultrafine fruit and vegetable powder by pressure difference pretreatment coupled with gradient enzymatic hydrolysis according to claim 1, characterized in that, In step S3, the pectinase activity is ≥30000U / g, the cellulase activity is ≥40000U / g, and the hemicellulase activity is ≥20000U / g.

4. The process for preparing ultrafine fruit and vegetable powder by pressure difference pretreatment coupled with gradient enzymatic hydrolysis according to claim 1, characterized in that, In step S4, the heat pump pre-drying temperature is 48-52℃, the wind speed is 3.5m / s, and the drying time is 4-6h.

5. The process for preparing ultrafine fruit and vegetable powder by pressure difference pretreatment coupled with gradient enzymatic hydrolysis according to claim 1, characterized in that, In step S5, high-pressure micro-mist spraying is achieved by 2-4 nozzles evenly distributed in the circumferential direction on the inner wall of the pulverizing chamber. The atomization pressure is 0.3-0.5MPa, the droplet size is ≤50μm, and the spraying is carried out intermittently in 2-3 times with an interval of 20-40s.

6. The process for preparing ultrafine fruit and vegetable powder by pressure difference pretreatment coupled with gradient enzymatic hydrolysis according to claim 1, characterized in that, In step S6, the vacuum degree is 0.08 MPa, the sterilization temperature is 78-82℃, and the processing time is 8-12 min.

7. The method according to claim 1, characterized in that, The fruit and vegetable ingredients are one or a combination of several of the following: kale, radish sprouts, Chinese kale, apple, carrot, spinach, broccoli, mango, strawberry, blueberry, mulberry, etc.