Preserved fruit production method based on vacuum stir-frying

Abstract

The invention relates to the technical field of food processing, and discloses a preparation method of preserved fruits based on vacuum frying. According to the method, the integrity of pulp is reserved through mechanical denucleation, and an intelligent crushing system is used for monitoring particle size distribution in real time and automatically terminating crushing; dynamically adjusting heating and vacuum parameters by adopting vacuum stir-frying equipment, and keeping the pulp taste; a gradient pressure forming technology and a deformation feedback compensation mechanism are combined to ensure uniform compactness of the preserved fruits; the water content is intelligently balanced by combining a sectional drying process with multi-sensor detection and adopting a staged temperature regulation and air flow circulation strategy. A traditional sugaring technology is broken through, the addition of sugar is reduced through the synergistic effect of vacuum stir-frying and physical dehydration, dietary fibers and heat-sensitive nutritional ingredients are completely reserved, the chewing toughness and storage stability of the product are remarkably improved, and the method has technology advancement and market application potential.

Description

Technical Field

[0001] The present invention relates to the technical field of food processing, and particularly relates to a method for making fruit preserves based on vacuum frying. Background Art

[0002] In the existing process of making fruit preserves, the traditional sugar-preserving process is widely used. However, this method often results in fruit preserves having too high a sugar content, which not only affects the health properties of the product but also limits its market acceptance among consumers who pursue a low-sugar diet. At the same time, it is difficult to precisely control the traditional processing method during the processes of pulp crushing, frying, and forming, which easily causes serious damage to the pulp fiber structure, resulting in poor taste, loose texture, and poor storage stability of the fruit preserves. Summary of the Invention

[0003] Aiming at the above-mentioned existing technical deficiencies, the purpose of the present invention is to provide a method for making fruit preserves based on vacuum frying, so as to solve the problems of too high sugar content and serious damage to the pulp fiber structure in the existing technology of apple fruit preserves.

[0004] To solve the above technical problems, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a method for making fruit preserves based on vacuum frying, and the method includes: Step S100: After the apple fruits are washed, they are subjected to mechanized core removal treatment to retain the complete pulp structure; Step S200: Transmit the cored pulp to the crushing process, monitor the particle size distribution of the crushed pulp through an image analysis module, and stop crushing when the proportion of the target particle size of the pulp reaches the threshold; Step S300: Transmit the crushed pulp to a vacuum frying device, adjust the heating power according to the temperature data of the vacuum frying device and the moisture content data of the pulp until the pulp is fried to a preset moisture content range; Step S400: Transmit the fried pulp to a servo press to perform gradient pressure forming, and trigger a pressure compensation mechanism through deformation state monitoring; Step S500: Perform segmented drying control on the formed pulp, adjust the drying process parameters according to the real-time moisture content, and after reaching the standard, transmit it to a vacuum packaging platform to complete packaging.

[0005] Preferably, in a possible implementation manner of the first aspect, the crushing process is implemented by a two-stage adjustable crushing mechanism for staged crushing: In the initial stage, preliminary crushing is carried out by a toothed disc crushing mechanism, and then fine particle size adjustment is carried out by a pair of roll crushing mechanisms. During the crushing process, the gap size of the crushing mechanism is dynamically adjusted through a hydraulic system; Equipped with an industrial camera, the pulp image in the crushing chamber is collected every 20 seconds, and the image analysis module calculates the particle size distribution data according to the pulp image through the edge detection algorithm; When the proportion of pulp with a particle size of 0.5 - 1 cm exceeds 85% in three consecutive samplings, the crushing operation is automatically terminated and the discharge channel is opened.

[0006] Preferably, in a possible implementation manner of the first aspect, the process of the image analysis module calculating the particle size distribution data includes: After graying the collected pulp image, the Canny edge detection algorithm is used to identify the boundary of the pulp particles; The particle size of each connected region is calculated by the minimum circumscribed rectangle method; A particle size distribution histogram is established to count the volume proportion of each particle size interval.

[0007] Preferably, in a possible implementation manner of the first aspect, the vacuum frying process specifically includes: Planetary stirring frying is carried out in a closed sandwich pot, and the stirring paddle keeps a constant gap with the inner wall of the pot body; During the frying process, the temperature distribution data and the pulp moisture content are collected synchronously; A vacuum degree - temperature correlation model is established to dynamically adjust the output power of the heating system and the working state of the vacuum pump; When it is detected that the moisture content of the material enters the preset target interval, it is automatically switched to the heat preservation mode and the discharge program is started.

[0008] Preferably, in a possible implementation manner of the first aspect, the process of establishing the vacuum degree - temperature correlation model includes: Obtain the corresponding relationship between the temperature distribution characteristics of the material and the water evaporation rate under different vacuum degree gradients; Based on the thermodynamic mass transfer equation, construct a quantitative relationship curve between the vacuum environment and the heat conduction efficiency; Set the vacuum degree threshold interval and divide the corresponding temperature control domain, and establish a linkage control parameter table for the pumping speed of the vacuum pump and the heating power; Verify and correct the model parameters through the change rate of the pulp moisture content collected in real time.

[0009] Preferably, in a possible implementation manner of the first aspect, the vacuum frying equipment is configured with a multi - parameter coupling control system, including: An embedded temperature sensor array arranged circumferentially on the pot body, which collects the temperature distribution in different regions in real time; The near - infrared spectrometer detects the pulp moisture content in real time; Input the temperature distribution and moisture content data into the vacuum - temperature correlation model to dynamically adjust the heating power.

[0010] Preferably, in a possible implementation manner of the first aspect, the gradient pressure forming process specifically includes: Uniformly lay the stir-fried pulp in a forming mold with air holes, and implement pressure control in three stages; During the pressurization process, use a multi-view image sensor to capture the deformation characteristics of the material surface in real time, and calculate the deformation difference rate between the central region and the edge region; When it is detected that the difference rate exceeds the preset safety threshold, automatically trigger the pressure compensation program to perform local pressure relief and re-pressurization operations.

[0011] Preferably, in a possible implementation manner of the first aspect, the implementation manner of the pressure compensation mechanism is: When the deformation rate of the central region is lower than that of the edge region by more than the preset safety threshold, the control system automatically opens the pressure relief valve at the edge of the mold, releases the local pressure and then re-applies the compensation pressure; During the compensation process, adopt a progressive pressure adjustment strategy, and the adjustment amplitude each time does not exceed 8% of the current pressure until the difference in deformation rate between the center and the edge is reduced within the preset safety threshold.

[0012] Preferably, in a possible implementation manner of the first aspect, the segmented drying control process includes: In the initial drying stage, use high-temperature forced convection drying to quickly reduce the moisture on the surface of the material, and the high-temperature range is 65-75 °C; In the equilibrium stage, switch to medium-temperature slow recovery treatment to promote the migration of internal moisture to the surface, and the medium-temperature range is 35-45 °C; In the final drying stage, implement pulsed variable-temperature drying, alternately applying short-term high-temperature air flow impact and normal-temperature static rest.

[0013] The beneficial effects of the present invention are as follows: By introducing the technical solution of the synergistic effect of vacuum frying and physical dehydration, the sugar addition amount of the preserved fruit is effectively reduced, while the dietary fiber and heat-sensitive nutrients in the fruit are completely retained, making the preserved fruit products healthier and more nutritious.

[0014] In addition, the present invention adopts advanced processes such as mechanized pit removal, intelligent crushing monitoring, dynamic adjustment of vacuum frying, gradient pressure forming and segmented drying control, significantly improving the chewing toughness and storage stability of the preserved fruit.

[0015] The whole production process is highly automated and intelligent, not only improving the production efficiency, but also ensuring the stability and consistency of the product quality, with remarkable process advancement and broad market application potential. Description of the Drawings

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0017] Figure 1 This application provides a flowchart of a method for making fruit preserves based on vacuum frying. Detailed implementation manners

[0018] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0019] Embodiment 1: As Figure 1 shown, the present invention provides a method for making fruit preserves based on vacuum frying, including: Step S100: After the apple fruits are washed, they are subjected to mechanized core removal treatment to retain the complete pulp structure.

[0020] In this embodiment, the apple raw materials are processed by a multi-stage cleaning system. In the first stage, a neutral cleaning solution with a pH of 7.0 - 7.5 is used in combination with a low-frequency vibration bubble generating device to efficiently remove the wax layer and agricultural residues while maintaining the integrity of the epidermis. In the second stage, a conical brush group is configured for cleaning. The brushes are made of food-grade silica gel and perform flexible cleaning on the concave parts of the apples in a reverse rotation manner. In the third stage, turbulent flushing is carried out through a 45°C micro-pressure water flow to synchronously activate the permeability of the pulp cell walls.

[0021] The core removal process uses a two-knife head collaborative operation system: a circumferential cutting knife head with an outer diameter of 28 mm locates the boundary of the fruit core and performs spiral cutting at a speed of 3000 r / min. At the same time, a conical thimble with an inner diameter of 10 mm extracts the entire fruit core. The apple pulp after core removal forms a hollow cylinder structure. Residual fruit core fragments are removed by visual inspection, and the intact ring-shaped pulp enters the nitrogen protection storage bin. When the weighing system detects that the material in the bin reaches 35 kg, it triggers the pneumatic conveying system to transport the pulp to the crushing process.

[0022] Step S200: Transmit the core-removed pulp to the crushing process, and monitor the particle size distribution of the crushed pulp through an image analysis module. Stop crushing when the proportion of the target particle size of the pulp reaches the threshold.

[0023] In this embodiment, the apple pitted pulp enters the crushing process through a pneumatic conveying system. The crushing process consists of two-stage adjustable crushing mechanisms: the front stage is a toothed disk crushing module, and the rear stage is configured with a pair of roll crushing modules. The pulp is transitionally connected between the two modules through a pneumatic chute, and the gap size of the crushing mechanism can be dynamically adjusted through a hydraulic system. The toothed disk crushing module adopts a fan-shaped crushing toothed disk group arranged in a double-axis staggered manner, and the surface of the toothed disk is provided with a wavy convex structure. The pair of roll crushing modules includes a pair of alloy steel rolls with a hard chromium plating on the surface, and the surface of the rolls is a honeycomb-like microstructural texture to increase the friction between the pulp and the roll surface.

[0024] The image monitoring system consists of three industrial cameras to form a visual monitoring network. Two of the cameras are installed above the observation window of the crushing chamber at a 45° angle, equipped with an LED ring-shaped supplementary light group. The third camera is installed at the discharge port position to verify the final crushing effect. The camera system synchronously triggers shooting at a cycle of 20 seconds, and each time it collects three groups of image data with different focal lengths and transmits them to the image processing industrial control computer.

[0025] In the image preprocessing stage, an adaptive white balance algorithm is used to eliminate ambient light interference, and Gaussian filtering is used for noise reduction processing. The particle size analysis algorithm is based on the Canny edge detection technology, and the specific process is as follows: The system first converts the RGB image into the HSV color space, and sets a saturation threshold (S>0.3) to distinguish the pulp and background regions; the segmented pulp region is binarized, and the eight-neighborhood connected region labeling method is used to identify independent particles; for each connected region, the particle size is calculated by the minimum circumscribed rectangle method to obtain the values of the major axis (L) and the minor axis (W), and the equivalent diameter is used as the particle size characterization parameter.

[0026] The system automatically eliminates debris noise with an area less than 50 pixels, groups the effective particle size data at 0.1 cm intervals, and estimates the volume proportion of each particle size interval through area weighted statistics to generate a dynamically updated three-dimensional particle size distribution histogram. When it is detected that the cumulative volume proportion in the 0.5 - 1 cm particle size interval exceeds 85% in three consecutive sampling periods, a shutdown instruction is sent to the crushing mechanism and the pneumatic discharge valve is activated.

[0027] The crushing process control system sets a triple verification protection program: After the first compliance, secondary sampling is started, and the interval is shortened to 5 seconds. If three consecutive detections are all compliant, the crushing is determined to be qualified. In the discharging stage, the material in the crushing chamber is driven into the temporary storage bin through the air pressure difference to complete the connection between the crushing process and the frying process.

[0028] Step S300: Transmit the crushed pulp to the vacuum frying equipment, and adjust the heating power according to the temperature data of the vacuum frying equipment and the moisture content data of the pulp until the pulp is fried to the preset moisture content range.

[0029] In this embodiment, the vacuum frying process is completed in a planetary stirring double-layer pot. This equipment adopts a double-layer stainless steel structure, with serpentine steam pipes evenly arranged in the jacket layer, and the flow rate of the heating medium is controlled by an electromagnetic proportional valve. The stirring system adopts a planetary gear drive mechanism, and three groups of special-shaped blades are installed on the main stirring shaft. Each group of blades is distributed at an angle of 120°, and there is a gap of 3.0 ± 0.2 mm from the inner wall of the pot body.

[0030] The temperature monitoring system consists of 32 PT100 platinum resistance temperature sensors to form a circumferential array, which is arranged in four layers along the axial direction of the pot body, and 8 measuring points are evenly configured in each layer. The sensor probe adopts a spring pre-tightening installation structure to ensure close fit with the inner surface of the pot body. The data acquisition module synchronously reads the temperature values of each measuring point with a period of 2 seconds. The near-infrared moisture detection system is integrated at the center position of the pot lid, equipped with an optical fiber probe array to perform a circular scan on the surface of the material, and a full-surface scan of the pot body is completed every 30 seconds to obtain the moisture content of the pulp. During the vacuum frying process, the obtained temperature distribution and moisture content data are input into the vacuum-temperature correlation model to dynamically adjust the heating power.

[0031] The vacuum control system consists of a two-stage Roots pump and a liquid ring vacuum pump to form a composite pumping unit. The vacuum degree regulation adopts a feedforward-feedback composite control strategy: a vacuum degree set value is generated based on the preset process curve, and at the same time, dynamic compensation is performed according to the real-time change rate of the moisture content. When it is detected that the moisture evaporation rate is lower than the threshold, the control system automatically increases the vacuum degree level to enhance the dehydration power.

[0032] The establishment process of the vacuum-temperature correlation model relies on pre-experiment data. In the pre-experiment stage, six groups of vacuum degree gradients are set, which are 10 kPa, 20 kPa, 40 kPa, 60 kPa, 80 kPa, and atmospheric pressure respectively. For each group of experiments, the curves of the parameters such as the central temperature, surface temperature, and moisture evaporation amount of the material changing with time are recorded. Based on the thermodynamic mass transfer equation, a three-variable coupling model including the vacuum degree P (kPa), temperature T (°C), and moisture content M (%) is established:

[0033] where k is the material characteristic coefficient, 、 are the influence indices of the vacuum degree and temperature (obtained by least squares fitting , ), t is the frying time, The equilibrium temperature (65°C is taken in this embodiment). The model divides the frying process into three control regions: the initial rapid dehydration region (P < 30 kPa), the intermediate constant-rate dehydration region (30 kPa ≤ P ≤ 50 kPa), and the later quality optimization region (P > 50 kPa). Each control region corresponds to a linkage control parameter table for the specific vacuum pump speed and heating power. A query table containing 128 working conditions is stored in the PLC controller, and the model parameters are verified and corrected by the change rate of the pulp moisture content collected in real time during the establishment process.

[0034] The operation logic of the multi-parameter coupling control system is as follows: After the crushed apple pulp enters the frying pan, the preheating program is first started to heat the pan body to 55°C; the primary vacuum stage is started to reduce the pressure to 20 kPa. When the average temperature of the material reaches 50°C, it enters the main dehydration stage: if the moisture content is higher than 45%, the heating power is maintained and the secondary vacuum pump is turned on; when the moisture content drops to the range of 30% - 35%, the fuzzy PID control algorithm is started to gradually reduce the heating intensity; when the moisture content approaches the target value (28 ± 2%), it enters the heat preservation and slow steaming stage, the vacuum pump is turned off and a constant temperature of 40°C is maintained for 10 minutes.

[0035] When it is detected that the temperature deviation in the local area exceeds ±3°C, the opening degree of the steam valve in the corresponding area is dynamically adjusted, and the heat convection is strengthened by changing the stirring direction. When the near-infrared sensor continuously detects that the overall moisture content is in the range of 26% - 30% for three times and the standard deviation is less than 1.5%, it is determined that the frying is completed. After the heating system is turned off, the vacuum-breaking valve is opened to slowly restore normal pressure. The discharging mechanism adopts a pneumatic bottom valve design. Driven by 0.5 MPa compressed air, the pulp is transported to the pressurized forming process through a screw conveyor.

[0036] Step S400: Transmit the fried pulp to the servo press to implement gradient pressurized forming, and trigger the pressure compensation mechanism through the deformation state monitoring.

[0037] In this embodiment, the forming process uses a modular servo press unit, and its pressure execution mechanism consists of three independently controlled hydraulic cylinders arranged in a triangular force application layout. The fried pulp is evenly laid in the forming die with air holes. The gradient pressurization process is implemented in three stages: the initial pre-press stage is applied at a rate of 5 kN / s to 30% of the target pressure value, and this stage lasts for 20 seconds to preliminarily densify the material; the main press stage is loaded at a rate of 3 kN / s to 80% of the target pressure and maintained for 60 seconds to achieve plastic deformation; the final press stage is slowly loaded at a rate of 1 kN / s to the full pressure value and held for 120 seconds to complete the shaping.

[0038] The deformation monitoring system consists of three industrial cameras forming an annular vision array. The cameras are installed 1.2 m above the mold at an inclination angle of 30°, constituting a multi-view stereo observation network. The image processing system uses digital image correlation technology to track the displacement changes of natural texture feature points on the surface of the material. The algorithm first divides the reference image into grids, with each unit grid size being 32×32 pixels. The zero-mean normalized cross-correlation function is used to calculate the correlation coefficient matrix before and after deformation. When the correlation coefficient is lower than 0.85, it is determined as an effective displacement point. The displacement gradient tensor is fitted by the least squares method to calculate the strain energy density distribution in each region.

[0039] The deformation difference rate calculation module continuously monitors the strain difference between the central region (a circular area with a diameter of 10 cm) and the edge annular region (a width of 5 cm). The system updates the deformation comparison parameters every 2 seconds. When the axial strain rate in the central region is lower than that in the edge region by more than 15 percentage points, it is determined that the pressure distribution is unbalanced. At this time, the pressure compensation mechanism is activated: First, 12 micro pressure relief valves configured at the edge of the mold are opened to reduce the local pressure to 70% of the current pressure value. After the pressure relief is completed, the compensation pressurization program applies directional pressurization to the central region at a rate of 0.3 kN / s, and gradually restores the pressure in the edge region at a rate of 0.2 kN / s.

[0040] During the compensation process, the pressure adjustment amount is dynamically adjusted according to the real-time change of the deformation difference rate, and the fuzzy PID control algorithm is used to ensure the smoothness of the adjustment process. For example, when it is detected that the deformation difference rate drops from 18% to 12%, the control system automatically adjusts the pressure compensation amplitude from 8% to 5%, effectively suppressing the overshoot phenomenon. The compensation operation continues until the difference in deformation rates between the center and the edge is less than the safety threshold of 5%, ensuring the structural uniformity of the formed body.

[0041] Step S500: Perform segmented drying control on the formed pulp, adjust the drying process parameters according to the real-time moisture content, and transfer it to the vacuum packaging platform for sub-packaging after reaching the standard.

[0042] In this embodiment, the segmented drying process is implemented on a modular intelligent drying line. The drying line adopts a three-section independent temperature zone design, and each temperature zone is equipped with an independent hot air circulation system and a humidity adjustment device. The initial drying section is configured with a high-pressure centrifugal fan and an electric heater to generate forced convection hot air with a maximum temperature of 90°C; the balancing section uses a two-stage PTC ceramic heating element combined with a humidifying spray system to achieve temperature and humidity control; the final drying section integrates a pulse combustion device. The transmission system uses a variable-frequency speed-regulating mesh belt, and the surface of the mesh belt is coated with a food-grade silica gel anti-sticking layer, and the mesh density decreases in a gradient along the transmission direction to meet the requirements of different drying stages.

[0043] When the initial drying stage starts, the formed candied fruits enter the high-temperature zone at a speed of 15 cm / s, and the high-temperature range is 65 - 75°C. The hot air system impacts the surface of the material obliquely at a 45° angle. The temperature control system adopts a feed-forward compensation algorithm to automatically adjust the heating power according to the temperature of the incoming material. A dynamic residence time control is set in this stage. When the dielectric constant sensor detects that the moisture content on the surface layer of the material drops to 25%, the running speed of the mesh belt is increased, and the candied fruits are transferred to the equilibrium stage in advance to prevent excessive hardening of the surface layer.

[0044] In the equilibrium stage, the candied fruits enter a medium-temperature constant-temperature environment, and the medium-temperature range is 35 - 45°C. The control system starts an intermittent gentle breeze circulation mode: every 2 minutes of operation, a low-speed air flow of 0.5 m / s is turned on for 30 seconds to promote the outward diffusion of internal moisture, and then it enters a static tempering state. The humidity sensor array real-time monitors the relative humidity of the environment. When the detected absolute humidity difference reaches 3 g / m³, the dehumidification valve is automatically triggered to update the drying medium. When the near-infrared sensor detects that the moisture content difference between the center and the surface layer of the material is ≤ 3%, the candied fruits are marked as entering the stable migration state, and the transfer section program is started.

[0045] Adaptive pulse drying is implemented in the final drying stage. After the material enters the variable-temperature zone, short-time hot air and normal-temperature static are applied alternately. The control system starts mode selection according to the real-time moisture content distribution: when the overall moisture content > 18%, the high-frequency pulse mode (alternation of 80°C / 2 s hot air and normal temperature for 9 s) is executed; when the moisture content drops to 12% - 18%, it is switched to the medium-frequency pulse mode (alternation of 60°C / 2 s hot air and normal temperature for 18 s); when the moisture content is below 12%, the low-frequency pulse mode (alternation of 40°C / 5 s hot air and normal temperature for 25 s) is enabled until the final moisture content reaches the standard of 10%. After the candied fruits completed the final drying are cooled, they are grabbed by the robotic arm and sent to the vacuum packaging machine to complete the sealed packaging under 10KPa vacuum.

[0046] Example 2: The present invention provides a method for making fruit candied fruits based on vacuum frying, and the method further includes introducing a real-time monitoring of rheological properties and a dynamic pressure regulation system in the gradient pressure forming process.

[0047] Before the fried pulp enters the servo press, the viscoelastic response characteristics of the material are first measured by an online rheological analysis module. This module uses a non-contact ultrasonic probe array to invert the elastic modulus and viscosity coefficient of the pulp by measuring the shear wave propagation rate.

[0048] The forming die is embedded with a micro stress sensor network to capture the stress relaxation behavior of the material during the pressure application process in real time. The system establishes a rheological parameter - pressure response database and automatically generates a pressure gradient curve according to the real-time viscoelastic state of the pulp. When it is detected that the material exhibits high elastic characteristics, the pressure holding time in the pre-pressing stage is extended and the main pressing rate is reduced; if the viscosity of the material is dominant, the pressure peak value in the final pressing stage is increased and the pressure holding period is shortened.

[0049] The control system is equipped with a self-learning function. By comparing historical forming data with the texture indicators of the finished product, it continuously optimizes the matching relationship between rheological parameters and pressure settings. This technology achieves precise adaptation of the forming pressure to the material properties, effectively eliminates texture fluctuations caused by batch differences, and significantly improves the uniformity and structural density of the preserved fruit forming. After forming, the surface finish of the preserved fruit is improved, and the distribution of pores on the cross-section is more uniform, creating an ideal moisture migration path for the subsequent drying process.

[0050] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these changes and modifications.

Claims

1. A method for making fruit preserves based on vacuum frying, characterized in that, The method includes: Step S100: After the apple fruits are washed, they are mechanically pitted to retain the complete pulp structure; Step S200: Transfer the pitted pulp to the crushing process, monitor the particle size distribution of the crushed pulp through the image analysis module, and stop crushing when the proportion of the target particle size of the pulp reaches the threshold; Step S300: Transfer the crushed pulp to the vacuum frying equipment, adjust the heating power according to the temperature data of the vacuum frying equipment and the moisture content data of the pulp until the pulp is fried to the preset moisture content range; Step S400: Transfer the fried pulp to the servo press to perform gradient pressure forming, and trigger the pressure compensation mechanism through the deformation state monitoring; Step S500: Carry out segmented drying control on the formed pulp, adjust the drying process parameters according to the real-time moisture content, and transfer it to the vacuum packaging platform for sub-packaging after reaching the standard.

2. The method for making fruit preserves based on vacuum frying according to claim 1, wherein The crushing process is implemented by a two-stage adjustable crushing mechanism for staged crushing: In the initial stage, preliminary crushing is carried out by a toothed disc crushing mechanism, and then the fine particle size is adjusted by a pair-roller crushing mechanism. During the crushing process, the gap size of the crushing mechanism is dynamically adjusted through the hydraulic system; An industrial camera is equipped to collect the pulp image in the crushing cavity every 20 seconds, and the image analysis module calculates the particle size distribution data according to the pulp image through the edge detection algorithm; When the proportion of the pulp with a particle size of 0.5 - 1 cm exceeds 85% in three consecutive samplings, the crushing operation is automatically terminated and the discharge channel is opened.

3. The method for making fruit preserves based on vacuum frying according to claim 2, characterized in that, The process of the image analysis module calculating the particle size distribution data includes: After the collected pulp image is grayscale processed, the Canny edge detection algorithm is used to identify the boundary of the pulp particles; The particle size of each connected region is calculated by the minimum circumscribed rectangle method; A particle size distribution histogram is established to count the volume proportion of each particle size interval.

4. The method for making fruit preserves based on vacuum frying according to claim 1, wherein, The specific process of the vacuum frying includes: Implement planetary stirring frying in a closed sandwich pot, and keep a constant gap between the stirring paddle and the inner wall of the pot body; During the frying process, the temperature distribution data and the moisture content of the pulp are collected synchronously; Establish a vacuum degree - temperature correlation model to dynamically adjust the output power of the heating system and the working state of the vacuum pump; When it is detected that the moisture content of the material enters the preset target interval, it is automatically switched to the heat preservation mode and the discharge program is started.

5. The method for making fruit preserves based on vacuum frying according to claim 4, characterized in that, The process of establishing the vacuum degree - temperature correlation model includes: Obtain the corresponding relationship between the temperature distribution characteristics of the material and the moisture evaporation rate under different vacuum degree gradients; Construct a quantitative relationship curve between the vacuum environment and the heat conduction efficiency based on the thermodynamic mass transfer equation; Set the vacuum degree threshold interval and divide the corresponding temperature control domain, and establish a linkage control parameter table for the pumping speed of the vacuum pump and the heating power; Verify and correct the model parameters through the change rate of the real-time collected moisture content of the pulp.

6. The method for making fruit preserves based on vacuum frying according to claim 4, wherein, The vacuum frying equipment is configured with a multi-parameter coupling control system, including: An embedded temperature sensor array arranged circumferentially on the pot body to collect the temperature distribution of different regions in real time; A near-infrared spectrometer is used to detect the moisture content of the pulp in real time; Input the temperature distribution and moisture content data into the vacuum - temperature correlation model to dynamically adjust the heating power.

7. The method for making fruit preserves based on vacuum frying according to claim 1, wherein The specific process of the gradient pressure forming includes: Uniformly lay the fried pulp in a forming mold with air holes, and implement pressure control in three stages; During the pressurization process, the deformation characteristics of the material surface are captured in real time by a multi-view image sensor, and the deformation difference rate between the central region and the edge region is calculated; When it is detected that the difference rate exceeds the preset safety threshold, the pressure compensation program is automatically triggered to perform local pressure relief and re-pressurization operations.

8. The method for making fruit preserves based on vacuum frying according to claim 7, wherein, The implementation method of the pressure compensation mechanism is as follows: When the deformation rate of the central region is lower than that of the edge region by more than the preset safety threshold, the control system automatically opens the pressure relief valve at the edge of the mold, releases the local pressure and then reapplies the compensation pressure; During the compensation process, a progressive pressure adjustment strategy is adopted, and the adjustment amplitude each time does not exceed 8% of the current pressure until the difference in deformation rate between the center and the edge is reduced to within the preset safety threshold.

9. The method for making fruit preserves based on vacuum frying according to claim 1, characterized in that, The segmented drying control process includes: In the initial drying stage, high-temperature forced convection drying is used to quickly reduce the moisture on the surface of the material, and the high-temperature range is 65-75°C; In the equilibration stage, it is changed to medium-temperature slow recovery treatment to promote the migration of internal moisture to the surface, and the medium-temperature range is 35-45°C; In the final drying stage, pulsed variable-temperature drying is implemented, alternately applying short-term hot air and normal-temperature static.

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