Freeze-dried rice production device and method based on multi-stage conditioning

Abstract

The application provides a kind of freeze-dried rice production device and production method based on multi-order conditioning, relating to food processing technical field, including accurate soaking device, superheated steam conditioning device, segmented cooking equipment, ice water quenching washing device, ultrasonic draining and tray laying device, double modal quick-freezing equipment, low-temperature vacuum freeze-drying bin and nitrogen filling packaging machine connected in sequence, each device realizes signal transmission and parameter linkage of full-process electric control elements through central control system (PLC), forming a complete multi-order conditioning equipment system. Through eight-order continuous conditioning, especially the synergistic effect of "superheated steam conditioning-segmented cooking-ice water quenching", the gelatinization of rice grains is uniform, the hardness after rehydration is more ideal, solving the problem of "soft outside and hard inside" of traditional products; the removal rate of surface free starch is relatively high, the soup after rehydration is clear, and there is no paste soup phenomenon, fundamentally solving the problems of nutrient destruction and harmful substance generation caused by high-temperature processing.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of food processing, and particularly relates to a freeze-dried rice production device and method based on multi-stage conditioning. BACKGROUND

[0002] As a kind of dehydrated instant food, freeze-dried rice has been widely used in many fields due to its light weight, long shelf life, good nutrient retention after rehydration and other advantages. However, the existing freeze-dried rice production technology still has some defects, such as: it is difficult to balance the gelatinization degree of the surface and the inside of the rice grains during the cooking stage, it is difficult to restore the fluffy texture after rehydration, the taste is soft and inelastic, and the phenomenon of soft outside and hard inside is common; another defect is that the traditional soaking process leads to high water absorption difference of rice grains, and the water content fluctuates greatly after cooking, so the time needs to be set according to the highest water content during freeze-drying, causing energy waste, traditional heat conduction oil heating plate layer, uneven heat transfer, slow water sublimation rate, high energy consumption; in addition: the residual lipase on the surface of the rice grains can catalyze the hydrolysis of fat to produce free fatty acids, and then oxidation reaction occurs, the traditional process cannot effectively remove the surface free amino acids, and Maillard reaction occurs with reducing sugar during storage, the product is brown and has stale taste, ordinary vacuum packaging has residual oxygen, which accelerates the oxidation reaction, and after frequent opening, it is more prone to moisture and mildew, leading to quality problems such as stale taste and halitosis of freeze-dried rice during the shelf life. SUMMARY

[0003] The present application aims to overcome the problems of hard rice core after rehydration, poor taste, long freeze-drying cycle, and easy deterioration during the shelf life in the existing freeze-dried rice production, and provides a freeze-dried rice production device and method based on multi-stage conditioning.

[0004] A freeze-dried rice production device and method based on multi-stage conditioning, comprising: a precise soaking device, a superheated steam conditioning device, a segmented cooking equipment, an ice water quenching and washing device, an ultrasonic draining and tray laying device, a dual-mode quick-freezing equipment, a low-temperature vacuum freeze-drying bin and a nitrogen filling packaging machine connected in sequence, each device realizes signal transmission and parameter linkage of all process electric control elements through a central control system (PLC), forming a complete multi-stage conditioning equipment system.

[0005] Optionally, the precision soaking device is used as the core equipment of the first conditioning stage, the inlet end is connected with the quantitative discharge port of the raw material bin through the conveying belt, and the outlet end is seamlessly connected with the feeding port of the superheated steam conditioning device through the inclined conveying belt, so that the rice grains can be continuously conveyed to the next process after cleaning and soaking. The precision soaking device is internally provided with a quantitative screw conveyor, three-stage cleaning tanks, a constant-temperature soaking tank, a water quality adjusting module and an automatic water supply system. The motor of the quantitative screw conveyor is connected with the central control system through the RS485 communication protocol, and the conveying amount can be automatically adjusted according to the processing capacity of the subsequent process. Each stage of the three-stage cleaning tanks is provided with a liquid level sensor and a water inlet electromagnetic valve. The liquid level signal is transmitted to the central control system in real time. When the liquid level is lower than the set value, such as half of the tank volume, the system automatically opens the water inlet electromagnetic valve to supply water. The third-stage cleaning tank uses pure water, and a flowmeter is installed on the water inlet pipeline of the third-stage cleaning tank. The flow signal is fed back to the system to maintain a stable cleaning water amount. The constant-temperature soaking tank is internally provided with a Pt100 temperature sensor and a drop-in liquid level sensor. The temperature signal is linked with the controller of the heating device, and the liquid level signal is associated with the electromagnetic valve of the automatic water supply system, so that the water temperature in the tank is stably maintained at 30℃, and the water-rice ratio is accurately controlled at 1.5:1. The metering pump of the water quality adjusting module is connected with the central control system through an analog signal, and food-grade phosphate can be automatically added at 0.1% of the rice weight. The pH sensor in the soaking tank monitors the pH value of the solution in real time. When the pH deviates from the set range, the system automatically adjusts the addition amount of the metering pump, so that the rice grains are quantitatively conveyed, impurities are cleaned, constant-temperature and constant-ratio soaking is achieved, and water quality is adjusted. Through the precise control of the water penetration rate and uniformity, a foundation is laid for the subsequent gelatinization.

[0006] Optionally, the superheated steam conditioning device undertakes the second-stage conditioning function. The discharge port is connected with the feeding port of the pressurized cooking section of the segmented cooking equipment through a mesh belt conveyor, and a material buffer hopper is arranged at the joint of the conveying belt to avoid the accumulation or spilling of rice grains. The device comprises an ultrasonic vibration draining sieve, a sealed steam cabin and a superheated steam generator. The vibration frequency and amplitude of the ultrasonic vibration draining sieve are adjusted through a frequency converter. The frequency converter is in communication with the central control system through the Modbus protocol. The system can adjust the vibration parameters according to the detection of the water film on the surface of the rice grains, so that no water droplets are left on the surface of the rice grains after draining for 30s. The cabin body of the sealed steam cabin adopts a double-layer insulation structure, and is internally provided with a K-type thermocouple and an infrared thermometer. The thermocouple is used to monitor the steam temperature in the cabin, and the infrared thermometer directly detects the surface temperature of the rice grains. The signals of the two are transmitted to the central control system. The system controls the temperature in the cabin by adjusting the steam output pressure of the superheated steam generator. The discharge end of the sealed steam cabin is provided with a mesh belt with adjustable speed. The frequency signal of the mesh belt motor is sent by the central control system, so as to ensure that the processing time of the rice grains in the cabin is long enough. After the water film on the surface of the rice grains is removed, the surface starch is slightly gelatinized through the precise control of the superheated steam to form a protective layer against excessive gelatinization.

[0007] Optionally, the segmented cooking device realizes third-order conditioning gelatinization depth gradient control, and the segmented cooking device comprises a pressurized cooking section, a turnover conveying mechanism and an atmospheric pressure supplementing section. The feeding port of the pressurized cooking section is connected with the outlet of the mesh belt conveyor of the superheated steam conditioning device through a sealing type feeding valve to avoid steam leakage. The discharge end of the pressurized cooking section is connected with the feeding port of the atmospheric pressure supplementing section through the turnover conveying mechanism. The atmospheric pressure supplementing section is a mesh belt type steam box. The cabin body of the pressurized cooking section is provided with a pressure sensor and a temperature sensor. The pressure signal is linked with the proportional controller of the steam inlet valve, and the temperature signal forms a closed loop control with the pressure signal to ensure that the cabin pressure is stably maintained at 0.12 MPa, and the corresponding temperature is 108℃. The cabin body is wrapped with a heating jacket. The power controller of the heating jacket is connected with the central control system to compensate for heat loss. The turnover conveying mechanism is composed of a stainless steel chain plate and a turnover blade. The running speed of the chain plate is adjusted through a frequency converter. The frequency converter receives the control signal of the central control system. The turnover frequency of the turnover blade is fixed to ensure that the rice grains can be uniformly turned over during the conveying process to avoid local overheating. The steam box of the atmospheric pressure supplementing section is provided with a temperature sensor, and the steam inlet pipeline is provided with an electromagnetic valve. The temperature signal is transmitted to the central control system. When the temperature in the box is lower than 100℃, the system automatically opens the electromagnetic valve to supplement steam. The mesh belt speed of the steam box matches the discharge speed of the pressurized cooking section to ensure that the residence time of the rice grains in the atmospheric pressure supplementing section is 5 min. Through pressurized-atmospheric pressure segmented cooking, uniform gelatinization of the rice grains from the outside to the inside is realized, and the gelatinization degree of the surface and the center is balanced.

[0008] Optionally, the ice water quenching rinsing device is responsible for the fourth conditioning, i.e. structure fixation and surface purification. The feeding port of the spiral propelling cooling tank is connected with the discharge port of the atmospheric pressure make-up section of the segmented cooking device through a chute, and the discharge end of the cooling tank is connected with the feeding hopper of the ultrasonic draining and tray laying device through a lifting conveyor belt. The ice water quenching rinsing device comprises an ice water storage tank, a spiral propelling cooling tank, a high-pressure atomizing nozzle group and a temperature control module. The ice water storage tank is provided with a refrigerating unit and is internally provided with a temperature sensor. The temperature signal is linked with the controller of the refrigerating unit to ensure that the water temperature in the tank is stably maintained at 2℃. The storage tank and the cooling tank are connected through a circulating water pump. The start and stop of the water pump is controlled by the liquid level sensor in the cooling tank. The spiral blade of the spiral propelling cooling tank is made of stainless steel. The rotating speed of the blade is adjusted through a speed reducer. The control signal of the speed reducer comes from the central control system to control the residence time of the rice in the cooling tank to be 60s. The high-pressure atomizing nozzle group is installed at the upper part of the spiral propelling cooling tank. The number of nozzles is determined according to the width of the tank body. A pressure sensor and an electromagnetic flowmeter are installed on the water inlet pipeline of the nozzle. The pressure signal is linked with the frequency converter of the high-pressure pump to ensure that the working pressure of the nozzle is stably maintained at 0.15MPa. The flow signal is fed back to the system to maintain the stable amount of rinsing water. The water temperature of the nozzle is controlled at 4℃ through a cold water machine and a temperature control module. The rinsing time is automatically calculated by the central control system according to the speed of the conveyor belt. The cooked rice can be quickly cooled and the surface sizing and free starch can be removed. The starch network structure is fixed and the oxidation substrate is reduced.

[0009] Optionally, the ultrasonic draining and tray laying device performs the fifth conditioning, i.e. water content uniformization treatment. A vibrating feeder is arranged below the feeding hopper of the ultrasonic draining and tray laying device. The outlet of the feeder is aligned with the feeding end of a low-frequency high-amplitude ultrasonic vibrating screen. The discharge end of the ultrasonic vibrating screen is connected with the conveyor belt of an automatic tray laying machine. The discharge end of the automatic tray laying machine is connected with the feeding port of the dual-mode quick freezing device through an AGV trolley. The ultrasonic draining and tray laying device comprises a low-frequency high-amplitude ultrasonic vibrating screen, an automatic tray laying machine and a thickness control module. The vibrating frequency and amplitude of the ultrasonic vibrating screen are adjusted through a special controller. The controller is connected with the central control system through a digital signal. The system can adjust the vibrating time according to the moisture detection result of the rice to ensure that the surface of the drained rice is dry and the moisture content is controlled within 65-68%.

[0010] Optionally, the sixth order of conditioning is completed by the dual-mode quick freezing device, the feeding port of the liquid nitrogen spraying tunnel is connected with the track of the AGV trolley, the discharging end of the liquid nitrogen spraying tunnel is connected with the feeding port of the strong wind deep freezing warehouse through the transition conveying belt, and the discharging end of the strong wind deep freezing warehouse is provided with an automatic tray pushing device to push the frozen tray to the feeding platform of the low-temperature vacuum freeze-drying bin. The device comprises a liquid nitrogen spraying tunnel, a strong wind deep freezing warehouse, a conveying belt and a temperature monitoring system. The liquid nitrogen spraying tunnel is internally provided with liquid nitrogen nozzles which are uniformly distributed on both sides and the top of the tunnel. An electromagnetic valve and a mass flow meter are installed on the liquid nitrogen supply pipeline of the nozzle. The opening and closing signals of the electromagnetic valve and the flow signals of the flow meter are transmitted to the central control system. The system adjusts the liquid nitrogen supply according to the temperature sensor signals in the tunnel to ensure that the temperature in the tunnel is maintained at -196℃, and the residence time of the rice in the tunnel is controlled to be 90s by the conveying belt speed.

[0011] Optionally, the seventh order of conditioning is realized by the low-temperature vacuum freeze-drying bin. The feeding platform of the bin is connected with the automatic tray pushing device of the dual-mode quick freezing device, the discharging end of the bin body is connected with the inert gas protection channel through a sealing door, and the other end of the channel is connected with the feeding port of the nitrogen filling packaging machine. The freeze-drying bin comprises a vacuum bin body, a plurality of heating plates, a CO2 circulation heating system, a vacuum pump group and a temperature and pressure control system. A vacuum degree sensor is installed on the inner wall of the vacuum bin body. The sensor signal is connected with the controller of the vacuum pump group to ensure that the vacuum degree in the bin is always ≤20Pa. The plurality of heating plates are uniformly distributed in the bin body. Each heating plate is provided with a Pt100 temperature sensor. The temperature signal is transmitted to the central control system. The system controls the temperature of the heating plate by adjusting the valve opening degree of the CO2 circulation heating system according to the preset curve -45℃→-25℃→-5℃→25℃→45℃. The heating rate is accurately adjusted by a PID controller. The CO2 tank of the CO2 circulation heating system is provided with a liquid level sensor and a pressure sensor. The liquid level signal is used to remind the addition of CO2. The pressure signal is connected with the controller of the booster pump to ensure the stable system pressure. During the freeze-drying process, the moisture content in the bin is indirectly monitored by a vacuum gauge. When the moisture content is ≤5%, the system sends a freeze-drying completion signal to realize the low-temperature vacuum freeze-drying of rice. The accurate temperature control curve accelerates the ordered sublimation of different combined water.

[0012] Optionally, the nitrogen filling packaging machine performs the eighth-stage conditioning storage environment optimization work, the feeding port of which is connected with the outlet of the inert gas protection channel, the inside of the packaging machine is sequentially provided with a vacuum chamber, a nitrogen filling chamber and a sealing mechanism, and the discharge end is connected with the conveying belt of the quality sorting system, the outlet of the qualified products of the sorting system is connected with the finished product bin through the conveying belt, the nitrogen filling packaging machine comprises an automatic film feeding mechanism, a vacuum-nitrogen-sealing device, an oxygen concentration detector and a quality sorting module, the film tension of the automatic film feeding mechanism is adjusted through a tension controller, the controller is connected with the central control system to ensure stable film conveying, the vacuum degree sensor signal of the vacuum chamber is linked with the controller of the vacuum pump to ensure the vacuum degree, a mass flow meter and an electromagnetic valve are installed on the nitrogen supply pipeline of the nitrogen filling chamber, the signal of the flow meter is transmitted to the central control system, the system adjusts the nitrogen filling amount according to the packaging size to ensure that the oxygen concentration in the packaging is less than 1%, and the heating temperature and sealing time of the sealing mechanism are adjusted through a temperature controller and a time relay, both of which are linked with the central control system, and the qualified products are conveyed to the finished product bin to realize the low-oxygen packaging of the freeze-dried rice and delay the quality deterioration during the storage period through environmental regulation.

[0013] Optionally, the central control system of the entire production device adopts a touch screen as a man-machine interaction interface, can display the running parameters, device states and production data of each device in real time, and supports parameter setting, fault alarm and data storage.

[0014] The method for producing freeze-dried rice by using the above device realizes the accurate quality regulation of rice grains from raw materials to finished products through eight-stage continuous conditioning, and comprises the following steps:

[0015] First-stage conditioning, moisture pre-distribution regulation:

[0016] The selected rice is conveyed to the three-stage cleaning tank through the quantitative screw conveyor, is cleaned with tap water (flow rate: 10-15 L / min) for 2 min to remove surface impurities, and is then cleaned with pure water for 1 min; the cleaned rice grains enter the constant-temperature soaking tank, are soaked in 30℃ warm water for 35 min, the 30℃ warm water can promote the limited swelling of the starch particles of the rice grains without causing gelatinization, and the soaking water-rice ratio is strictly controlled to be 1.5:1; 0.1% (based on the weight of the rice) of food-grade phosphate (sodium pyrophosphate and sodium tripolyphosphate are mixed at a ratio of 1:1) is added to the soaking water as a water quality regulator through a water quality adjusting device to maintain the pH of the soaking liquid at 6.5-7.0, the phosphate can chelate calcium and magnesium ions in the water to prevent them from combining with the starch and affecting the subsequent gelatinization, and at the same time, the phosphate can enhance the hardness of the rice grains to avoid excessive soaking and cause fragmentation.

[0017] Second-stage conditioning, surface starch pre-gelatinization:

[0018] The soaked rice is transported to an ultrasonic vibration draining sieve, and a surface water film is removed by vibration for 30 s. The ultrasonic draining can efficiently remove the surface moisture, and avoid slow temperature rise of the surface in subsequent cooking. Then, the rice is transported into a superheated steam cabin, and is treated in a superheated steam environment at 100-110 DEG C for 15 s. The surface starch of the rice is slightly gelled. The superheated steam can quickly raise the surface temperature of the rice, and make the surface starch molecules partially expand and form a weak gel structure, which lays a foundation for uniform gelatinization in subsequent cooking, and reduces excessive dissolution of starch in the cooking process.

[0019] Third-stage conditioning, gelatinization depth gradient regulation:

[0020] The conditioned rice is first transported into a pressurized cooking section, and is cooked at 0.12 MPa for 8 min. The pressurized cooking can accelerate the starch gelatinization process, and make the heat quickly penetrate to the center of the rice, so as to solve the problem of insufficient center gelatinization in traditional cooking. After the rice is uniformly turned by a turnover conveying device, the rice is transported into a normal-pressure supplementary cooking section, and is further cooked in a saturated steam environment at 100 DEG C for 5 min, so that the overall gelatinization degree of the rice reaches 85-90%, and the difference between the surface and the center gelatinization degree is less than or equal to 5%.

[0021] Fourth-stage conditioning, structure fixation and surface purification:

[0022] The cooked rice is immediately dropped into a spiral propelling cooling tank, and is quickly cooled in ice water at 2 DEG C for 60 s, so that the center temperature of the rice is reduced from 95-100 DEG C to below 15 DEG C. The ice water rapid cooling can quickly terminate the starch gelatinization reaction, fix the internal structure of the rice, and make the starch molecule chains contract to form a more stable network structure. During the cooling process, a high-pressure atomizing nozzle group is started at the same time, and the rice is atomized and rinsed by using pure water at 0.15 MPa pressure and 4 DEG C for 20 s. The high-pressure atomizing rinsing can efficiently remove the surface free starch, avoid the formation of a hard shell after freeze-drying, and wash away most of the lipase, so as to delay oxidation from the source.

[0023] Fifth-stage conditioning, moisture uniformization treatment:

[0024] The rinsed rice is transported to a low-frequency high-amplitude ultrasonic vibration sieve, and is drained for 30-40 s to be dry on the surface. At this time, the moisture content of the rice is controlled to be 65-68%. The low-frequency high-amplitude ultrasonic vibration can effectively remove the free moisture between the rice without damaging the structure of the rice. Then, the rice is uniformly laid on a freeze-drying tray by an automatic tray laying machine. The laying thickness is 3-5 cm, and the thickness error is less than or equal to ±0.5 cm. The accurately controlled laying thickness and uniformity are the key to ensure the consistency of the subsequent freeze-drying rate, and avoid incomplete drying caused by local over-thickness or energy waste caused by over-thin.

[0025] Sixth-stage conditioning, microstructure regulation:

[0026] The laid rice is first sent into a liquid nitrogen spraying tunnel, and is treated for 90 seconds under the spraying of liquid nitrogen at -196°C to make the surface of the rice grains glassified instantaneously to a depth of 100-200 pm. The instant glassification of the liquid nitrogen can form uniform micro-pores on the surface of the rice grains as a sublimation channel for water in the subsequent freeze-drying; then the rice grains are sent to a strong wind freezer at -38°C, and are frozen for 40-60 min under a wind speed of 8-10 m / s to reduce the temperature of the center of the rice grains to ≤-18°C, so as to avoid the damage to the starch network structure caused by large ice crystals formed in the traditional slow freezing, and to accelerate the freezing rate.

[0027] Seventh conditioning, control of moisture gradient sublimation:

[0028] The tray of the quick-frozen rice is sent into a freeze-drying chamber, and after the chamber is closed, a vacuum pump is started, and at the same time, the temperature of the heating plate layer is rapidly reduced to -45°C and maintained for 1 h. The pre-freezing strengthening can ensure that all the water is crystallized, so as to avoid the collapse of the structure caused by liquid water in the freeze-drying process; then a CO2 circulation heating system is started, and the temperature of the plate layer is controlled according to the following temperature curve:

[0029] First stage: -45°C→-25°C (temperature rising rate 1°C / min), maintained for 3 h (initial stage of sublimation drying, 80% free water is removed);

[0030] Second stage: -25°C→-5°C (temperature rising rate 0.5°C / min), maintained for 5 h (later stage of sublimation drying, residual free water is removed);

[0031] Third stage: -5°C→25°C (temperature rising rate 1°C / min), maintained for 4 h (initial stage of desorption drying, bound water is removed);

[0032] Fourth stage: 25°C→45°C (temperature rising rate 2°C / min), maintained for 2 h (later stage of desorption drying, deep dehydration);

[0033] During the whole freeze-drying process, the vacuum degree in the chamber is always controlled to be ≤20 Pa, and the moisture content of the final product is ≤5%. The stepwise temperature rising curve cooperates with the vacuum environment to make the water in different combined states sublimate in turn.

[0034] Eighth conditioning, optimization of storage environment:

[0035] After the freeze-drying is completed, the rice is taken out from the freeze-drying bin under the protection of inert gas and is immediately transported to a nitrogen filling packaging machine; the packaging machine is first vacuumized to be less than or equal to 10 Pa, and then is filled with food-grade nitrogen (purity is greater than or equal to 99.99%) to make the oxygen concentration in the packaging be less than or equal to 1%, so that the low-oxygen environment (oxygen is less than or equal to 1%) can effectively inhibit fat oxidation and microbial growth; the nitrogen is used as inert gas, has stable chemical properties and has no influence on the flavor of food, and then heat sealing is performed (sealing temperature is 180-200 DEG C, and time is 1-2 s); the high-barrier packaging material can long-term maintain the low-oxygen environment, and thus the quality of the product can be ensured to be stable during storage. In this stage, the shelf life is greatly prolonged through storage environment regulation.

[0036] The application provides a freeze-dried rice production device and production method based on multi-stage conditioning, and has the following beneficial effects:

[0037] Through eight-stage continuous conditioning, especially the synergistic effect of "superheated steam conditioning - segmented cooking - ice water quenching", the gelatinization of rice grains is uniform, the hardness after rehydration is more ideal, the problem of "soft outside and hard inside" of traditional products is solved, the removal rate of surface free starch is relatively high, and the soup after rehydration is clear and has no paste soup phenomenon.

[0038] In addition, the microstructure formed by the double-mode quick freezing is cooperated with the high-efficiency heat transfer of the CO2 circulation heating freeze-drying, so that the freeze-drying period is effectively shortened, the production efficiency is improved, and the energy consumption is reduced; meanwhile, no external additives are added, the raw material cost is not additionally increased, and the production cost is reduced.

[0039] In addition, the application removes lipase through pressure rinsing and insulates oxidation through nitrogen filling packaging, so that the shelf life of the product can be prolonged without adding preservatives, there is no obvious stale taste and halitosis during storage, and the quality stability is significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical scheme of the embodiments of the application, the drawings of the embodiments will be briefly introduced below.

[0041] The drawings described in the following description only relate to some embodiments of the application, rather than limiting the application.

[0042] In the drawings:

[0043] Figure 1 The installation sequence of each device of the production line of the application is shown;

[0044] Figure 2 The structure diagram of the precise soaking device of the application is shown;

[0045] Figure 3 The structure diagram of the superheated steam conditioning device of the application is shown;

[0046] Figure 4 The structural schematic diagram of the segmented cooking device is shown;

[0047] Figure 5 The structural schematic diagram of the ice water quenching rinsing device is shown;

[0048] Figure 6 The structural schematic diagram of the ultrasonic draining and tray laying device is shown;

[0049] Figure 7 The structural schematic diagram of the dual-mode quick freezing device is shown.

[0050] List of reference signs

[0051] 1, precise soaking device; 11, quantitative screw conveyor; 12, three-stage cleaning tank; 13, constant temperature soaking tank; 2, superheated steam conditioning device; 21, ultrasonic vibration draining sieve; 22, closed steam cabin; 23, superheated steam generator; 3, segmented cooking device; 31, pressurized cooking section; 32, overturning conveying mechanism; 33, atmospheric pressure steam supplementing section; 4, ice water quenching rinsing device; 41, ice water storage tank; 42, screw propelling type cooling tank; 43, high pressure atomizing spray head group; 5, ultrasonic draining and tray laying device; 51, ultrasonic vibration sieve; 52, automatic tray laying machine; 6, dual-mode quick freezing device; 61, liquid nitrogen spraying tunnel; 62, strong wind deep freezing warehouse; 63, conveying belt; 7, low temperature vacuum freeze-drying bin; 71, vacuum bin body; 72, multi-layer heating plate; 8, nitrogen filling packaging machine. DETAILED DESCRIPTION

[0052] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be described clearly and completely below with reference to the drawings of the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the described embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0053] Embodiment: please refer to the attached Figures 1-7 :

[0054] The application provides a multi-stage conditioning-based freeze-dried rice production device and method, which comprises a precise soaking device 1, an overheated steam conditioning device 2, a segmented cooking equipment 3, an ice water quenching and rinsing device 4, an ultrasonic draining and tray placing device 5, a dual-mode quick-freezing equipment 6, a low-temperature vacuum freeze-drying bin 7 and a nitrogen filling packaging machine 8 connected in sequence, forming an eight-stage continuous conditioning equipment system. The precise soaking device 1 is internally provided with a quantitative screw conveyor 11, a three-stage cleaning tank 12, a constant-temperature soaking tank 13, a water quality adjusting module and an automatic water replenishing system. The motor of the quantitative screw conveyor 11 is connected with the central control system through an RS485 communication protocol. Each stage of the three-stage cleaning tank 12 is provided with a liquid level sensor and a water inlet electromagnetic valve. The liquid level signal is transmitted to the central control system in real time. The third stage of the cleaning tank uses pure water, and a flow meter is installed on the water inlet pipeline thereof. The constant-temperature soaking tank 13 is internally provided with a Pt100 temperature sensor and an input liquid level sensor. The temperature signal is linked with the controller of the heating device, and the liquid level signal is associated with the electromagnetic valve of the automatic water replenishing system. The overheated steam conditioning device 2 comprises an ultrasonic vibration draining sieve 21, a sealed steam cabin 22 and an overheated steam generator 23. The vibration frequency and amplitude of the ultrasonic vibration draining sieve 21 are adjusted through a frequency converter. The frequency converter is communicated with the central control system through a Modbus protocol. The cabin body of the sealed steam cabin 22 adopts a double-layer insulation structure and is internally provided with a K-type thermocouple and an infrared thermometer. The signals of the two are transmitted to the central control system. The system controls the temperature in the cabin by adjusting the steam output pressure of the overheated steam generator 23. A mesh belt is arranged at the discharge end of the sealed steam cabin 22, and the frequency signal of the mesh belt motor is sent by the central control system. The segmented cooking equipment 3 comprises a pressurized cooking section 31, a turnover conveying mechanism 32 and a normal-pressure steam supplementing section 33. The cabin body of the pressurized cooking section 31 is provided with a pressure sensor and a temperature sensor, and is wrapped with a heating jacket outside. The power controller of the heating jacket is connected with the central control system. The turnover conveying mechanism 32 is composed of a stainless steel chain plate and a turnover blade. The running speed of the chain plate is adjusted through a frequency converter. The frequency converter receives the control signal of the central control system. The turnover frequency of the turnover blade is fixed. The ice water quenching and rinsing device 4 comprises an ice water storage tank 41, a spiral propelling cooling tank 42, a high-pressure atomizing nozzle group 43 and a temperature control system. The ice water storage tank 41 is provided with a refrigerating unit and is internally provided with a temperature sensor. The temperature signal is linked with the controller of the refrigerating unit. The storage tank and the cooling tank are connected through a circulating water pump. The spiral blade of the spiral propelling cooling tank 42 is made of stainless steel. The rotating speed of the blade is adjusted through a speed reducer. The control signal of the speed reducer comes from the central control system. The high-pressure atomizing nozzle group 43 is installed at the upper portion of the spiral propelling cooling tank 42. A pressure sensor and an electromagnetic flowmeter are installed on the water inlet pipeline of the nozzle.The ultrasonic draining and tray placing device 5 comprises a low-frequency high-amplitude ultrasonic vibrating screen 51, an automatic tray placing machine 52 and a thickness control module. A vibrating feeder is arranged below the feeding hopper of the ultrasonic draining and tray placing device 5. The outlet of the feeder is aligned with the feeding end of the low-frequency high-amplitude ultrasonic vibrating screen 51. The discharging end of the ultrasonic vibrating screen 51 is connected with the conveying belt of the automatic tray placing machine 52. The discharging end of the automatic tray placing machine 52 is connected with the feeding port of the double-mode quick-freezing equipment 6 through an AGV trolley. A laser thickness gauge is arranged above the conveying belt of the automatic tray placing machine 52. The detection signal of the thickness gauge is transmitted to the central control system. The double-mode quick-freezing equipment 6 comprises a liquid nitrogen spraying tunnel 61, a conveying belt 63 and a strong wind deep-freezing warehouse 62. The feeding port of the liquid nitrogen spraying tunnel 61 is connected with the track of the AGV trolley. The discharging end of the liquid nitrogen spraying tunnel 61 is connected with the feeding port of the strong wind deep-freezing warehouse 62 through a transition conveying belt 63. The automatic tray pushing device is arranged at the discharging end of the strong wind deep-freezing warehouse 62. The low-temperature vacuum freeze-drying bin 7 comprises a vacuum bin body 71, a plurality of heating plates 72, a CO2 circulation heating system, a vacuum pump set and a temperature and pressure control module. A vacuum degree sensor is arranged on the inner wall of the vacuum bin body 71. The sensor signal is linked with the controller of the vacuum pump set. The plurality of heating plates 72 are uniformly distributed in the bin body. Each heating plate is provided with a Pt100 temperature sensor. The temperature signal is transmitted to the central control system. The system controls the temperature of the heating plate by adjusting the valve opening degree of the CO2 circulation heating system. The temperature is raised according to the preset curve -45℃→-25℃→-5℃→25℃→45℃. The temperature rising rate is accurately adjusted through the PID controller. The CO2 storage tank of the CO2 circulation heating system is provided with a liquid level sensor and a pressure sensor. The nitrogen filling packaging machine 8 comprises an automatic film feeding mechanism, a vacuum-nitrogen filling-sealing device, an oxygen concentration detector and a quality sorting module.

[0055] In the embodiment of the present disclosure, the inlet end of the precise soaking device 1 is connected with the quantitative discharging port of the raw material bin through a conveying belt. The outlet end is seamlessly connected with the feeding port of the superheated steam conditioning device 2 through an inclined conveying belt.

[0056] In the embodiment of the present disclosure, the superheated steam conditioning device 2 undertakes the second-stage conditioning function. The discharging port is connected with the feeding port of the pressurized cooking section 31 of the segmented cooking equipment 3 through a mesh belt conveyor. A material buffer hopper is arranged at the joint of the conveying belt.

[0057] In the embodiment of the present disclosure, the feeding port of the pressurized cooking section 31 is connected with the outlet of the mesh belt conveyor of the superheated steam conditioning device 2 through a sealing type feeding valve. The discharging end of the pressurized cooking section 31 is connected with the feeding port of the atmospheric pressure steam supplementing section 33 through a turnover conveying mechanism 32. A temperature sensor is arranged in the steam tank of the atmospheric pressure steam supplementing section 33. An electromagnetic valve is arranged on the steam inlet pipeline. The temperature signal is transmitted to the central control system.

[0058] In the embodiment of the present disclosure, the feeding port of the spiral propelling cooling tank 42 is connected with the discharge port of the atmospheric pressure make-up section 33 of the sectional cooking device 3 through a chute, and the discharge end of the cooling tank is connected with the feeding hopper of the ultrasonic draining tray device 5 through a lifting conveyor belt.

[0059] In the embodiment of the present disclosure, the liquid nitrogen spray nozzle is installed in the liquid nitrogen spray tunnel 61, the electromagnetic valve and the mass flow meter are installed on the liquid nitrogen supply pipeline of the nozzle, and the switch signal of the electromagnetic valve and the flow signal of the flow meter are transmitted to the central control system. The temperature sensor and the wind speed sensor are installed in the body of the strong wind freezing warehouse 62.

[0060] In the embodiment of the present disclosure, the feeding port of the nitrogen filling packaging machine 8 is connected with the outlet of the inert gas protection channel, the discharge end is connected with the conveying belt of the mass sorting system, the outlet of the qualified products of the sorting system is connected with the finished product warehouse through the conveying belt, the tension of the film roll of the automatic film feeding mechanism is adjusted by the tension controller, the controller is connected with the central control system, the vacuum degree sensor signal of the vacuum chamber is linked with the controller of the vacuum pump, the mass flow meter and the electromagnetic valve are installed on the nitrogen supply pipeline of the nitrogen filling chamber, the flow meter signal is transmitted to the central control system, and the heating temperature and the sealing time of the sealing mechanism are adjusted by the temperature controller and the time relay, both of which are linked with the central control system.

[0061] The production method of the embodiment is carried out in the following steps:

[0062] First-stage conditioning and precise soaking: after the rice grains are cleaned, they are soaked in warm water at 30℃ for 35min, the soaking water to rice ratio is 1.5:1, and 0.1% food-grade phosphate is added to the soaking water;

[0063] Second-stage conditioning, draining and superheated steam conditioning: after soaking, the rice grains are drained by ultrasonic vibration until no water film is left on the surface, and then treated by superheated steam at 100-110℃ for 15s;

[0064] Third-stage conditioning and sectional cooking: the rice grains first enter the pressurized cooking section (0.12MPa, 108℃) for cooking for 8min, and then enter the atmospheric pressure make-up section (100℃) for cooking for 5min after being turned over;

[0065] Fourth-stage conditioning, ice water quenching and rinsing: the cooked rice is immediately dropped into 2℃ ice water for cooling for 60s, and at the same time, rinsed by atomized pure water spray at 0.15MPa and 4℃ for 20s;

[0066] Fifth-stage conditioning, draining and tray laying: the rinsed rice is drained by a low-frequency high-amplitude ultrasonic vibration screen until the surface is dry;

[0067] Sixth-stage conditioning and double-mode quick freezing: first treated by liquid nitrogen spraying (-196℃) for 90s, and then put into a strong wind freezing warehouse at -38℃, and frozen until the center temperature is ≤-18℃;

[0068] Seventh order of conditioning, low temperature vacuum assisted freeze-drying: the frozen rice is placed in the freeze-drying chamber, the plate temperature is raised according to the curve of -45℃ (1h)→-25℃ (3h)→-5℃ (5h)→25℃ (4h)→45℃ (2h), and the vacuum degree in the chamber is always ≤20Pa;

[0069] Eighth order of conditioning, storage environment optimization:

[0070] After freeze-drying is completed, the rice is taken out from the freeze-drying chamber under the protection of inert gas and immediately transported to a nitrogen filling packaging machine. The packaging machine is first vacuumized to ≤10Pa, then filled with food-grade nitrogen to make the oxygen concentration in the package ≤1%, and then heat sealed.

Claims

1. A multi-stage tempering-based freeze-dried rice production device, characterized by, The device system of eight-stage continuous conditioning is formed by sequentially connecting the precise soaking device (1), the superheated steam conditioning device (2), the segmented cooking equipment (3), the ice water quenching and rinsing device (4), the ultrasonic draining and tray placing device (5), the double-mode quick freezing equipment (6), the low-temperature vacuum freeze-drying bin (7) and the nitrogen filling packaging machine (8). The precise soaking device (1) is internally provided with a quantitative screw conveyor (11), three-stage cleaning tanks (12), a constant-temperature soaking tank (13), a water quality adjusting module and an automatic water supplement system. The motor of the quantitative screw conveyor (11) is connected with the central control system through an RS485 communication protocol. Each stage of the three-stage cleaning tanks (12) is provided with a liquid level sensor and a water inlet electromagnetic valve. The liquid level signal is transmitted to the central control system in real time. Pure water is used in the third-stage cleaning tank, and a flowmeter is installed on the water inlet pipeline of the third-stage cleaning tank. The constant-temperature soaking tank (13) is internally provided with a Pt100 temperature sensor and a drop-in liquid level sensor. The temperature signal is linked with the controller of the heating device, and the liquid level signal is associated with the electromagnetic valve of the automatic water supplement system. The superheated steam conditioning device (2) comprises an ultrasonic vibration draining screen (21), a sealed steam cabin (22) and a superheated steam generator (23). The vibration frequency and amplitude of the ultrasonic vibration draining screen (21) are adjusted through a frequency converter. The frequency converter is communicated with the central control system through a Modbus protocol. The cabin body of the sealed steam cabin (22) adopts a double-layer insulation structure and is internally provided with a K-type thermocouple and an infrared thermometer. The signals of the two are transmitted to the central control system. The system controls the temperature in the cabin by adjusting the steam output pressure of the superheated steam generator (23). A mesh belt is arranged at the discharge end of the sealed steam cabin (22), and the frequency conversion signal of the mesh belt motor is sent by the central control system. The segmented cooking equipment (3) comprises a pressurized cooking section (31), a turnover conveying mechanism (32) and a normal-pressure steam supplement section (33). The cabin body of the pressurized cooking section (31) is provided with a pressure sensor and a temperature sensor, and is wrapped with a heating jacket. The power controller of the heating jacket is connected with the central control system. The turnover conveying mechanism (32) is composed of a stainless steel chain plate and a turnover blade. The running speed of the chain plate is adjusted through a frequency converter. The frequency converter receives the control signal of the central control system. The turnover frequency of the turnover blade is fixed. The ice water quenching and rinsing device (4) comprises an ice water storage tank (41), a spiral propelling cooling tank (42), a high-pressure atomizing nozzle group (43) and a temperature control system. The ice water storage tank (41) is provided with a refrigerating unit and a temperature sensor. The temperature signal is linked with the controller of the refrigerating unit. The storage tank and the cooling tank are connected through a circulating water pump. The spiral blade of the spiral propelling cooling tank (42) is made of stainless steel. The rotating speed of the blade is adjusted through a speed reducer. The control signal of the speed reducer comes from the central control system. The high-pressure atomizing nozzle group (43) is installed on the upper part of the spiral propelling cooling tank (42). A pressure sensor and an electromagnetic flowmeter are installed on the water inlet pipeline of the nozzle. The ultrasonic draining and tray placing device (5) comprises a low-frequency high-amplitude ultrasonic vibrating screen (51), an automatic tray placing machine (52), and a thickness control module. A vibrating feeder is arranged below the feeding hopper of the ultrasonic draining and tray placing device (5). The outlet of the feeder is aligned with the feeding end of the low-frequency high-amplitude ultrasonic vibrating screen (51). The discharging end of the ultrasonic vibrating screen (51) is connected with the conveying belt of the automatic tray placing machine (52). The discharging end of the automatic tray placing machine (52) is connected with the feeding port of the double-mode quick-freezing equipment (6) through an AGV trolley. A laser thickness gauge is installed above the conveying belt of the automatic tray placing machine (52). The detection signal of the thickness gauge is transmitted to a central control system. The double-mode quick-freezing equipment (6) comprises a liquid nitrogen spraying tunnel (61), a conveying belt (63), and a strong wind deep-freezing warehouse (62). The feeding port of the liquid nitrogen spraying tunnel (61) is connected with the track of the AGV trolley. The discharging end of the liquid nitrogen spraying tunnel (61) is connected with the feeding port of the strong wind deep-freezing warehouse (62) through a transition conveying belt (63). The discharging end of the strong wind deep-freezing warehouse (62) is provided with an automatic tray pushing device. The low-temperature vacuum freeze-drying bin (7) comprises a vacuum bin body (71), a multi-layer heating plate (72), a CO2 circulation heating system, a vacuum pump set, and a temperature and pressure control module. A vacuum degree sensor is installed on the inner wall of the vacuum bin body (71). The sensor signal is linked with the controller of the vacuum pump set. The multi-layer heating plate (72) is uniformly distributed in the bin body. Each heating plate is provided with a temperature sensor. The temperature signal is transmitted to the central control system. The system controls the temperature of the heating plate by adjusting the valve opening degree of the CO2 circulation heating system. The temperature is raised according to a preset curve -45℃→-25℃→-5℃→25℃→45℃. The heating rate is accurately adjusted through a PID controller. The CO2 storage tank of the CO2 circulation heating system is provided with a liquid level sensor and a pressure sensor. The nitrogen filling packaging machine (8) comprises an automatic film feeding mechanism, a vacuum-nitrogen filling-sealing device, an oxygen concentration detector, and a quality sorting module.

2. The multi-stage conditioning-based freeze-dried rice production device according to claim 1, characterized in that, The inlet end of the precise soaking device (1) is connected with the quantitative discharging port of the raw material bin through a conveying belt. The outlet end is seamlessly connected with the feeding port of the superheated steam conditioning device (2) through an inclined conveying belt.

3. The multi-stage conditioning-based freeze-dried rice production device according to claim 2, characterized in that, The discharging port of the superheated steam conditioning device (2) is connected with the feeding port of the pressurized cooking section (31) of the segmented cooking equipment (3) through a mesh belt conveyor. A material buffer hopper is arranged at the joint of the conveying belts.

4. The multi-stage conditioning-based freeze-dried rice production device according to claim 3, characterized by, The feeding port of the pressurized cooking section (31) is connected with the outlet of the mesh belt conveyor of the superheated steam conditioning device (2) through a sealing type feeding valve. The discharging end of the pressurized cooking section (31) is connected with the feeding port of the atmospheric pressure steam supplementing section (33) through a turnover conveying mechanism (32). A temperature sensor is installed in the steam tank of the atmospheric pressure steam supplementing section (33). An electromagnetic valve is arranged on the steam inlet pipeline. The temperature signal is transmitted to the central control system.

5. The multi-stage conditioning-based freeze-dried rice production device according to claim 4, characterized in that, The feeding port of the spiral propelling type cooling tank (42) is connected with the discharging port of the atmospheric pressure steam supplementing section (33) of the segmented cooking equipment (3) through a chute. The discharging end of the cooling tank is connected with the feeding hopper of the ultrasonic draining and tray placing device (5) through a lifting type conveying belt.

6. The multi-stage conditioning-based freeze-dried rice production device according to claim 5, characterized by, The liquid nitrogen spraying tunnel (61) is internally provided with liquid nitrogen nozzles, and an electromagnetic valve and a mass flow meter are installed on the liquid nitrogen supply pipeline of the nozzles; the switch signal of the electromagnetic valve and the flow signal of the flow meter are transmitted to the central control system; and the body of the strong wind freezing warehouse (62) is provided with a temperature sensor and a wind speed sensor.

7. The multi-stage conditioning-based freeze-dried rice production device according to claim 6, characterized by, The feed inlet of the nitrogen filling packaging machine (8) is connected with the outlet of the inert gas protection channel, the discharge end is connected with the conveying belt of the mass sorting system, the outlet of the qualified products of the sorting system is connected with the finished product bin through the conveying belt, the tension of the film roll of the automatic film feeding mechanism is adjusted through a tension controller, the controller is connected with the central control system, the vacuum degree sensor signal of the vacuum chamber is linked with the controller of the vacuum pump, a mass flow meter and an electromagnetic valve are installed on the nitrogen supply pipeline of the nitrogen filling chamber, the flow meter signal is transmitted to the central control system, and the heating temperature and the sealing time of the sealing mechanism are adjusted through a temperature controller and a time relay, and both are linked with the central control system.

8. A method for producing multi-step conditioning-based freeze-dried rice using the multi-step conditioning-based freeze-dried rice production apparatus according to claim 1, characterized by, The method comprises the following steps: First conditioning and precise soaking: after the rice grains are cleaned, they are soaked in warm water at 30°C for 35 min, the soaking water to rice ratio is 1.5:1, and 0.1% food-grade phosphate is added to the soaking water; Second conditioning, draining and superheated steam conditioning: after soaking, the rice grains are drained by ultrasonic vibration until no water film is left on the surface, and then treated by superheated steam at 100-110°C for 15 s; Third conditioning, segmented cooking: the rice grains first enter a pressurized cooking section, are cooked at 0.12 MPa and 108°C for 8 min, are turned over and then enter an atmospheric pressure supplementary cooking section, and are cooked at 100°C for 5 min; Fourth conditioning, ice water quenching and rinsing: the cooked rice is immediately cooled in 2°C ice water for 60 s, and rinsed by atomized pure water mist at 0.15 MPa and 4°C for 20 s; Fifth conditioning, draining and tray laying: the rinsed rice is drained by a low-frequency high-amplitude ultrasonic vibration sieve until the surface is dry; Sixth conditioning, double-mode quick freezing: the rice is first sprayed by liquid nitrogen at -196°C for 90 s, and then placed in a strong wind freezing warehouse at -38°C until the center temperature is ≤-18°C; Seventh conditioning, low-temperature vacuum-assisted freeze-drying: the quick-frozen rice is placed in a freeze-drying bin, the bin layer temperature is raised according to a curve of -45°C for 1 h→-25°C for 3 h→-5°C for 5 h→25°C for 4 h→45°C for 2 h, and the vacuum degree in the bin is always ≤20 Pa; Eighth conditioning, storage environment optimization: after the freeze-drying is completed, the rice is taken out from the freeze-drying bin under inert gas protection, immediately conveyed to a nitrogen filling packaging machine, vacuumized by the packaging machine to ≤10 Pa, filled with food-grade nitrogen gas to make the oxygen concentration in the packaging ≤1%, and then heat sealed.

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