WO2019085736A1

WO2019085736A1 - Food vacuum freeze-drying and sterilization method and device

Info

Publication number: WO2019085736A1
Application number: PCT/CN2018/110355
Authority: WO
Inventors: 卢允庄
Original assignee: 王一田
Priority date: 2017-10-31
Filing date: 2018-10-16
Publication date: 2019-05-09
Also published as: CN107647246A

Abstract

A food vacuum freeze-drying and sterilization method and device. The method comprises the following steps: put frozen food in a drying chamber, and enabling the frozen food to absorb heat energy under a vacuum state, so that ice in the frozen food sublimates to form steam, and the obtained steam escapes and condenses on the surface of a cold trap; when the food reaches a desired drying degree, inflate negative-pressure saturated steam, so that the temperature of the food reaches a desired pasteurization temperature, and enable the heated food to be kept at the temperature for a period of time; trapping steam in the drying chamber by using a low-temperature ice layer on the surface of the cold trap, so as to reduce the pressure in the drying chamber, evaporate moisture condensed from the food, and reduce the temperature of the food; and remove the vacuum state, and take out the food. The device comprises a drying chamber, a heating device, a negative-pressure steam device, and a vacuum steam-trapping device. By means of the method and the device, freeze-drying and pasteurization treatment can be carried on food, and the quality of the food is kept.

Description

Food vacuum freeze drying and sterilization method and equipment

Technical field

The invention relates to a food processing method, in particular to a method for vacuum freeze drying and sterilization of food. The invention also relates to a food vacuum freeze drying and sterilizing apparatus for treating food products by the method.

Background technique

Vacuum freeze-drying, referred to as lyophilization, is a method of freezing the aqueous material below the eutectic point temperature, causing the water to become ice, and then sublimating the ice to water vapor at a suitable temperature and vacuum. Out, thereby obtaining the technology of the dried product. After lyophilization, the moisture content in the food is low, generally not more than 5%, which inhibits the growth and reproduction of microorganisms and is beneficial for long-term preservation. However, many pathogenic bacteria such as Salmonella, Listeria, and Escherichia coli can survive for a long period of time after vacuum freeze-drying, and can be propagated in large quantities, such as after contact with water. In recent years, food-borne diseases caused by pathogenic bacteria of low-moisture foods have frequently occurred, and sterilization treatment before entering circulation has become a necessary condition for the production of many freeze-dried foods.

In the existing lyophilizer with in-situ sterilization function, the sterilized object generally refers to the equipment in the drying chamber, not the material to be lyophilized. Such as the patent CN200610031825.5 "freeze drying unit and its use of the same solution defrosting, cleaning, sterilization process", CN201210120209.2 "a method and device for online sterilization of freeze dryer", CN201420509624.1 "A freeze dryer sterilization system" and CN201520839764.X "an efficient sterilization and sterilization device for freeze dryers".

For the sterilization of freeze-dried foods, the methods used and the problems are:

After the material is dried, it is sterilized by dry heat, such as microwave heating, hot air heating or radiant heating. However, freeze-dried foods have low moisture content, and ordinary heating is not only difficult to remove pathogenic bacteria with strong heat resistance under low water activity, such as Salmonella and Escherichia coli, and too high heating temperature can easily cause the shape of the product. And color changes and destruction of nutrients.

Patent CN201621458519.5 "A freeze-drying device for food drying and sterilization" first performs microwave sterilization operation on the material, and then performs freezing and cooling. Microwave sterilization uses the heat generated by microwaves to kill microorganisms. On the one hand, there is uneven sterilization. In addition, the local temperature of the materials may be too high to affect the quality, and there is still the possibility of food contamination during the subsequent freezing and drying process.

Patent CN200710134872.7 "A method for the preservation of lyophilized food by nano-silver coating film combined with microwave" proposes that the food raw material is immersed in nano-silver aqueous solution, then freeze-dried, and then enters the microwave sterilization link; patent CN200710134405" A combined sterilization method for the preservation of freeze-dried foods by ozone, ultraviolet and nano silver coating film" lyophilizes the raw materials after coating treatment, and the finished product is sterilized by ozone in the sealed pocket, and then controlled by ultraviolet sterilization auxiliary sterilization method. Microbial content. Although the method achieves a certain bactericidal effect, the food contains nano silver, which is difficult to be widely accepted.

In addition, the lyophilized food is sterilized by a high-pressure steam sterilizer, and although a better sterilization effect can be achieved, there is a problem that the water content increases after the food is sterilized, and the high-temperature and high-pressure steam affects the quality of the food. Moreover, the sterilization method of the existing freeze-dried food generally adopts independent sterilization equipment and processes, and has the problems of poor sterilization effect, cumbersome process, complicated equipment, large occupied space, large energy consumption, and high labor cost.

Summary of the invention

In view of the above problems in the prior art, it is an object of the present invention to provide a method and apparatus for food vacuum freeze drying and sterilization. The food vacuum freeze-drying and sterilizing equipment of the invention can realize the lyophilization and sterilization process in one time in the same set of equipment, saves equipment investment, has short running time, saves energy, reduces operation steps and reduces labor cost.

In order to achieve the above object, an aspect of the invention provides a method for vacuum freeze drying and sterilization of food, comprising:

Pretreating the material, freezing the material to be treated to below the eutectic point temperature and then feeding it into the drying chamber;

The material is evacuated in the drying chamber, and the material absorbs heat under vacuum to sublimate the ice in the material into water vapor and escape from the material and desublimate;

After the material reaches the required degree of dryness, the drying chamber is filled with negative pressure saturated steam, the steam is condensed on the surface of the material and the internal pores, the temperature of the material rises to the desired pasteurization temperature, and the pasteurization temperature is maintained. Stop charging the negative pressure saturated steam after a period of time;

The water vapor in the drying chamber is captured to reduce the pressure in the drying chamber, and the condensed water on the surface of the material and the internal pores evaporates, and the material is cooled;

After the pressure in the cabin drops to the required steam trapping pressure, the air is filled, the vacuum state in the drying chamber is released, and the freeze-drying and sterilization process is ended.

Preferably, after the material is evacuated in the drying chamber, the pressure in the drying chamber is 13 to 130 Pa.

Preferably, the pasteurization temperature is 60 to 90 °C.

Preferably, the time during which the pasteurization temperature is maintained is from 10 to 90 min.

Preferably, wherein the pressure of the negative pressure saturated steam corresponds to a temperature of saturated water that is 0 to 10 ° C higher than the pasteurization temperature.

Preferably, the steam trapping pressure is from 100 to 3000 Pa.

Another aspect of the present invention provides a food vacuum freeze-drying and sterilizing apparatus comprising a drying compartment connected by a pipe, a heating device, a vacuum steaming device, and a vacuum trapping device, wherein the heating device and the negative steaming device a steam pressure device coupled to provide thermal energy for generating a vacuum-saturated steam, the vacuum steam device being coupled to the drying chamber for steam sterilization of a material contained in the drying chamber, the vacuum trapping device A drying chamber connection is used to trap water vapor in the drying chamber to reduce the pressure in the drying chamber.

Preferably, the drying chamber comprises a cylinder, the cylinder body is internally provided with a heating plate assembly, and the heating plate assembly has a water inlet port and a water outlet port connected to the heating device through a pipe, the cylinder body An inlet port connected to the negative pressure steam device and an exhaust port connected to the vacuum trap are provided; the cylinder is further provided with an inlet air valve connected to the inlet port.

Preferably, a control device is further included, and the cylinder is internally provided with a temperature sensor and a vacuum pressure sensor respectively connected to the control device for collecting data.

Preferably, the outer surface of the cylinder is fixedly connected with a uniformly distributed heat exchange tube, and the water inlet and the water outlet of the heat exchange tube are respectively connected to the steam generating device through a pipeline; A counter-radiation panel is disposed inside, and a plurality of thermal insulation pads are disposed between the anti-radiation panel and the cylinder.

Preferably, the heat insulating mat has a thickness of 3 to 10 mm.

Preferably, the heating device comprises a soda water heat exchanger, the inlet of the steam inlet side of the steam-water heat exchanger is connected to a high-pressure steam source through a first steam regulating valve, and the outlet passes through a first one-way valve and a hydrophobic a valve connection; an outlet of one side of the output water of the steam-water heat exchanger is connected to the water inlet port of the heating plate assembly, and an inlet of one side of the input water of the steam-water heat exchanger is sequentially connected to a circulating water pump through the pipeline, Cooling water side of the heat exchanger and the water outlet port of the heating plate assembly; a bypass valve is connected between the inlet and the outlet of the hot water side of the cooling heat exchanger through a bypass line; the cooling A cooling water pump is connected to the inlet of the heat exchanger on the cooling water side.

Preferably, the negative pressure steam device comprises a steam generator, and the hot water outlet of the steam generator is connected in sequence to a hot water pump and a water inlet port of the heat exchange tube on the surface of the cylinder; the steam a hot water inlet of the generator is connected to the water outlet port of the heat exchange tube; the steam generator is provided with an automatic water supply valve connected to a water inlet pipe; a steam tube heater is arranged inside the steam generator The inlet of the coil heater is connected to a high pressure steam source through a second steam regulating valve, and the outlet of the coil heater is connected to a steam trap through a second one-way valve; the steam outlet on the upper part of the steam generator A first negative pressure steam valve is connected to the port; the temperature sensor for measuring the water temperature is disposed in the steam generator chamber, and the temperature sensor is connected to the control device.

Preferably, the vacuum trap comprises a trap, one side of the trap is provided with an opening connected to the exhaust valve of the drying chamber, and the other side is passed through an evacuation valve and a vacuum pump Connected to the trap; a trap consisting of a plurality of sets of metal coils or metal plates is placed in the chamber of the trap, a refrigerant is circulated inside the trap, and an inlet of the trap passes through a refrigerant valve A refrigeration device is connected; a cavity is provided in the cavity of the trap for connecting a second negative pressure steam valve of the negative pressure steam device; and a lower portion of the trap is further provided with a drain valve.

Preferably, the trap is disposed inside or outside the cylinder. .

Compared with the prior art, the food vacuum freeze-drying and sterilization method and apparatus of the present invention have the following advantages:

First, the general food vacuum freeze-drying mainly includes a process of food quick-freezing-pre-vacuum-sublimation drying-de-vacuum, etc. The invention increases the process of vacuum-steam sterilization after the sublimation of the food is finished, and pasteurization is performed. The negative pressure saturated steam corresponding to the temperature temporarily enhances the water activity of the dried food, and utilizes the characteristics of strong steam penetration and latent heat to quickly and efficiently kill the pathogenic bacteria. Sterilization is carried out after the sublimation drying process, the moisture inside the food no longer migrates, the structure of the food is stable, the negative pressure steam does not damage the internal structure of the food, and the sterilization process ensures that the quality of the food does not decrease to the greatest extent.

Secondly, after the steam pasteurization of the food of the invention, the drying chamber is connected with the trap, and the water vapor is trapped by the low temperature ice layer on the surface of the cold trap, so that the pressure in the drying chamber is rapidly decreased, and when the pressure drops below the food temperature. At the corresponding saturation pressure, the condensed water added to the surface of the food and the internal pores evaporates while the temperature of the food drops. The rapid evaporation of condensed water in food and the rapid cooling of food ensure proper storage conditions of food after sterilization.

Third, the steam trapping process of the present invention does not require the activation of the vacuum pump, thereby avoiding the adverse effects of moisture on the vacuum pump lubricating oil and also saving the energy consumption of the vacuum pump.

Fourth, the present invention utilizes the sterilized steam to remove a portion of the ice layer on the surface of the cold trap during the steam trapping process, thereby reducing the energy consumption required for cold trap deicing. This integrated energy utilization of the present invention can save about 35% of energy consumption compared to the independent cold trap de-icing process and the energy consumed by the steam sterilization process.

Fifth, the negative pressure steam generating device used in the present invention not only provides a negative pressure steam source for sterilization, but also the circulation of the hot water on the heat exchange tube of the drying tank body wall realizes temperature control of the drying chamber cylinder body. Avoid condensation of steam on the wall of the cylinder, and negative pressure steam can also quickly defrost the chiller trap.

Sixth, compared with the system equipment for sterilizing the food in the lyophilization device and then moving to the sterilization device for sterilization, the food vacuum freeze-drying and sterilizing device of the invention not only saves equipment investment, but also has short running time. It also saves energy, reduces operating links, and reduces labor costs.

DRAWINGS

Figure 1 is a schematic view showing the structure of a food vacuum freeze drying and sterilizing apparatus of the present invention;

Figure 2 is a partial enlarged view of a portion I of Figure 1.

Main reference mark:

1. Drying cabin; 2. Heating device; 3. Negative pressure steam device; 4. Vacuum steam catching device; 11. Cylinder; 12, heating plate assembly; 13. Temperature sensor; 14. Pressure sensor; ; 16, steam exhaust valve; 17, heat exchange tube; 18, anti-radiation board; 19, insulation pad; 21, cooling water pump; 22, cooling heat exchanger; 23, bypass valve; 24, circulating water pump; Soda water heat exchanger; 26, first steam regulating valve; 27, first check valve; 28, steam trap; 31, hot water pump; 32, negative pressure steam generator; 33, coil heater; One-way valve; 35, temperature sensor; 36, second steam regulating valve; 37, automatic water inlet valve; 38, first negative pressure steam valve; 39, second negative pressure steam valve; 41, trap; Cold trap; 43, vacuum valve; 44, vacuum pump; 45, refrigeration liquid supply valve; 46, drain valve.

Detailed ways

The structure of the present invention will be further described in detail below with reference to the accompanying drawings.

In the traditional lyophilization process of food, lyophilization and sterilization of food are carried out in two separate steps, that is, the food is lyophilized in a lyophilization device and then moved to a sterilizing device for sterilization. In contrast, the food vacuum freeze drying and sterilization method of the present invention may, in some embodiments, include the following steps:

Step 1), pretreating the material, and freezing the material to be processed to below the eutectic point temperature, and then feeding the material into the drying chamber;

Step 2), the material is evacuated in the drying chamber, and the material absorbs heat under vacuum to make the ice in the material sublimate into water vapor and escape from the material and desublimate;

Step 3) After the material reaches the required degree of dryness, the drying chamber is filled with negative pressure saturated steam, the steam is condensed on the surface of the material and the internal pores, and the temperature of the material rises to the desired pasteurization temperature, and is maintained at the bar. The sterilization temperature is stopped for a period of time and then the negative pressure saturated steam is stopped;

Step 4), collecting water vapor in the drying chamber to reduce the pressure in the drying chamber, and the condensed water on the surface of the material and the internal pores evaporates, and the material is cooled;

Step 5), after the pressure in the cabin drops to the required steam trapping pressure, the air is filled, the vacuum state in the drying chamber is released, and the freeze-drying and sterilization process is ended.

1 is a schematic structural view of a food vacuum freeze-drying and sterilizing apparatus according to an embodiment of the present invention, and FIG. 2 is a partial enlarged view of a portion I of FIG.

As shown in Fig. 1, the apparatus of the present invention comprises a drying compartment 1, a heating device 2, a vacuum steaming device 3 and a vacuum trapping device 4 connected by a pipe (not labeled in Fig. 1), wherein the heating device 2 and the device The negative pressure steam device 3 is connected to provide thermal energy for generating negative pressure saturated steam, and the negative pressure steam device 3 is connected to the drying chamber 1 for steam sterilization of the contents of the drying chamber 1 A steam trap 4 is connected to the drying chamber 1 for trapping water vapor in the drying chamber 1 to lower the pressure in the drying chamber 1.

Further, as shown in FIG. 1, the drying chamber 1 comprises a cylinder 11; the cylinder 11 is internally provided with a heating plate assembly 12, comprising two sets of symmetrically arranged heating plate sets (not shown in FIG. 1), two sets of heating plates The water inlet port and the water outlet port are respectively combined and connected to the heating device 2 through a pipe; the cylinder 11 of the drying chamber is internally provided with a temperature sensor 13 and a vacuum pressure sensor 14, and the sensors are connected to the control device. The drying chamber body 11 has an inlet port, and the inlet port is connected to the negative pressure steam device 3 through a pipeline; the drying chamber body 11 has an exhaust port, and the exhaust port passes through the exhaust valve 16 and the pipeline and the vacuum The collecting device 4 is connected; the drying chamber body 11 has an inlet air port, and the inlet air port is connected with an inlet air valve 15 through the pipeline; the outer surface of the drying chamber body 11 is fixedly connected by welding to have a uniform and orderly distribution. The heat exchange tube 17, the water inlet port and the water outlet port of the heat exchange tube 1 are connected to the negative pressure steam device 3 through a pipeline. The interior of the drying chamber body 11 is provided with a counter-radiation plate 18, and a plurality of insulating pads 19 are disposed between the anti-radiation plate 18 and the sterilization chamber cylinder 11. The thickness of the insulating pad 19 is 5 mm, and the end of the anti-radiation plate 18 The portion is fixed to the sterilization chamber cylinder 11 by bolts and nuts.

Further, as shown in FIG. 1, the heating device 2 includes a soda water heat exchanger 25; the inlet of the steam side of the soda water heat exchanger 25 is connected to the high temperature and high pressure steam generated by the boiler through the first steam regulating valve 26, and the outlet passes through the first The check valve 27 is connected to the steam trap 28; the outlet of the water side of the steam-water heat exchanger 25 is connected to the water inlet port of the heating plate assembly 12 through a pipeline, and the inlet of the water side of the steam-water heat exchanger 25 is connected to the circulating water pump through the pipeline in turn. 23. The water outlet port of the hot water side of the heat exchanger 22 and the hot plate assembly 12; the inlet and outlet of the hot water side of the cooling heat exchanger 22 are connected to the bypass valve 23 through the bypass line; the cooling heat exchanger 22 A cooling water pump 21 is connected to the inlet of the cooling water side.

Further, as shown in FIG. 1, the negative pressure steam device 3 includes a steam generator 32; the hot water outlet of the steam generator 32 sequentially connects the hot water pump 31 and the water inlet port of the heat exchange tube 17; the heat of the steam generator 32 The water inlet is connected to the water outlet port of the heat exchange tube 17; the steam generator 32 is provided with an automatic water supply valve 37 connected to the purified water pipe (not shown in FIG. 1); the steam generator 32 is internally provided with a coil heater 33, the disk The inlet of the tube heater 33 is connected to the high temperature and high pressure steam through a line and a steam regulating valve 36, and the outlet is connected to the line between the heating system check valve 27 and the steam trap 28 through the check valve 34; the upper portion of the steam generator 32 A first negative pressure steam valve 38 is connected to the steam outlet port; a temperature sensor 35 for measuring the water temperature is provided inside the steam generator 32.

Still further, as shown in FIG. 1, the vacuum trap 4 includes a trap 41 having a side opening having an opening connected to the exhaust valve (16) of the drying chamber; the other side is connected to the exhaust valve 43 through The vacuum pump 44 is connected; the trap 41 is provided with a cold trap 42 composed of a plurality of sets of metal coils or metal plates. The inside of the metal tube or the metal plate of the cold trap 42 is circulated with a refrigerant, and the refrigerant inlet of the cold trap 42 The refrigerant valve 45 is connected to the refrigeration device; the trap 41 has a second negative pressure steam valve 39 connected to the negative pressure steam device; and a drain valve 46 is disposed at the lower portion of the trap 41.

In addition, the above-described embodiments of the present invention further provide that a suitable device can be selected according to actual conditions. However, it is preferred to implement the food vacuum freeze drying and sterilizing device proposed by the present invention, and the specific work flow can be carried out as follows:

a) The pre-treated and quick-frozen food and its carrier enter the drying chamber.

b) Pre-vacuum: The circulating water pump starts, the water circulation in the heating plate assembly; the refrigerant valve of the cold trap is opened, and the cold trap is cooled; the vacuum pump, the vacuum valve and the exhaust valve are opened, and the pressure in the drying chamber is lowered. In this step, after the material is evacuated in the drying chamber, the pressure in the drying chamber is preferably controlled to be 13 to 130 Pa.

c) Sublimation drying: After the pressure in the drying chamber reaches the working pressure (13-130Pa), the steam regulating valve is opened, the steam-water heat exchanger transfers the heat of the steam to the water on the other side, and the operation of the circulating water pump makes the temperature of the heating plate group When it is raised, the heating plate transfers heat to the food through radiation, and the moisture in the food gradually sublimates after the heat is absorbed. The water vapor sublimated from the material enters the trap through the exhaust valve and condenses on the surface of the cold trap with a lower temperature.

During the sublimation drying process, the first steam regulating valve automatically adjusts the water temperature of the heating plate according to the heat required for sublimation of the material in the process. When the water temperature of the heating plate needs to drop rapidly, close the steam regulating valve and turn on the cooling water pump. When the material reaches the desired degree of drying, the temperature of the heating plate and the material are both close to the set drying temperature, the drying process is finished, the material maintains the original shape but the inside forms a porous structure. Close the exhaust valve, vacuum valve, vacuum pump and refrigerant valve to stop vacuuming and refrigerant supply.

d) Sterilization preparation: the second steam regulating valve and the hot water pump on the negative pressure steam device are turned on, and the coil heater transfers the heat of the steam to the water in the negative pressure steam generator, so that the water temperature rises above the required The sterilization temperature is 0 to 5 ° C and maintained at this temperature, and the temperature of the wall surface of the drying cylinder body also rises; the water temperature of the heating plate group is set to the required sterilization temperature, and the temperature of the heating plate rises.

e) Steam sterilization: the first negative pressure steam valve is opened, the saturated steam in the negative pressure steam generator enters the cavity of the drying chamber, and condenses on the surface of the lower temperature food and inside the pores, and the heat released by the steam condensation process makes The temperature of the food rapidly rises to the required sterilization temperature, and then the opening or start-stop state of the first negative pressure steam valve is adjusted, so that the food temperature is maintained at the sterilization temperature for a period of time, that is, the required sterilization time is reached (30 min). After that, close the first negative pressure steam valve and shut down the hot water pump.

f) Steam trapping: the steam exhaust valve is opened, the steam in the drying chamber enters the trap, and condenses on the surface of the low temperature cold trap frost layer, the pressure in the drying chamber drops, and the pressure drops below the food temperature. At the saturation pressure, the condensed water on the surface of the food and inside the pores evaporates and the temperature of the food drops. During the steam trapping process, the water temperature setting of the heating plate is simultaneously lowered to 25 to 40 ° C, and the temperature of the heating plate is lowered.

g) De-vacuum: When the pressure in the drying chamber drops to the required steam trapping pressure (100-3000 Pa), the steam trapping process ends. As the temperature of the food drops, the condensate on the surface of the food and inside the pores evaporates. After closing the exhaust valve, open the inlet air valve to release the vacuum condition of the drying chamber. At the same time, the second negative pressure steam valve is opened to defrost the unmelted ice layer on the surface of the cold trap until the ice layer on the surface of the cold trap is completely melted, and the second negative pressure steam valve is closed.

h) After the vacuum condition of the drying chamber is released, the food and its load are taken out, and the food is processed and packaged. Open the exhaust valve and drain valve to drain the water from the trap.

Example 1

The following is a description of the workflow of the above embodiment by taking the lyophilization and sterilization process of bovine waste with a water content of 72% as follows:

a) Inoculation and quick freezing: Take several pieces of the raw materials after pre-treatment such as washing and dicing, and inoculate Enterococcus faecalis (ATCC 8459), the inoculation quantity is 8×10 ⁷ cfu/g; then the raw materials are frozen in the frozen storage. After filling to -25 ° C, it is placed in the drying chamber 1 .

b) pre-vacuum: the circulating water pump 31 is started to heat the water in the heating plate; the refrigerant valve 45 of the vacuum trap 4 is opened, the cold trap 42 is cooled; the vacuum pump 44, the vacuum valve 43 and the exhaust valve 16 are opened, and the drying chamber is opened. The pressure in the chamber drops.

c) sublimation drying: after the pressure in the drying chamber reaches the working pressure of 70 Pa, the first steam regulating valve 26 is opened, the soda heat exchanger 25 transfers the heat of the steam to the water on the other side, and the operation of the circulating water pump 31 causes the heating plate group 12 to The temperature rises, the heating plate transfers heat to the food through radiation, and the moisture in the food gradually sublimates after the food absorbs heat. The water vapor sublimated from the material enters the trap 41 through the exhaust valve 16, and is desublimed on the surface of the cold trap 42 having a lower temperature. During the sublimation drying process, the water temperature of the heating plate is set to a plurality of temperature intervals according to the running time, wherein the highest water temperature is controlled at 120 ° C and the cold trap temperature is controlled at -40 ° C.

During the sublimation drying process, the first steam regulating valve 26 automatically adjusts the opening degree according to the heat required for sublimation of the material in the process to adjust the water temperature of the heating plate. When the water temperature of the heating plate needs to rapidly drop, the first steam regulating valve 26 is closed and the cooling water pump 21 is turned on. When the material reaches the desired degree of drying, the temperature of the heating plate and the material are both close to the set drying temperature of 40 ° C, the drying process is finished, the material maintains the original shape but the inside forms a porous structure. The exhaust valve 16, the vacuum valve 43, the vacuum pump 44, and the refrigerant valve 45 are closed, and the vacuuming and refrigerant supply are stopped.

d) Sterilization preparation: The second steam regulating valve 36 and the hot water pump 31 on the negative pressure steam device are turned on, and the coil heater 33 transfers the heat of the steam to the water in the negative pressure steam generator 32, so that the water temperature rises to At 80 ° C and maintained at this temperature, the temperature of the wall surface of the dried casing body 11 also rises; the water temperature of the heating plate group 12 is set to a desired sterilization temperature of 75 ° C, and the temperature of the heating plate rises.

e) steam sterilization: the first negative pressure steam valve 38 is opened, the saturated steam in the negative pressure steam generator 32 enters the cavity of the drying chamber, and condenses on the surface of the lower temperature food and inside the pores, and is released by the steam condensation process. The heat causes the temperature of the food to rise rapidly to the desired sterilization temperature, and then adjusts the opening or the start-stop state of the first negative pressure steam valve to maintain the food temperature at the sterilization temperature for 30 minutes, and then closes the first negative pressure steam valve 38. , shut down the hot water pump 31.

f) Steam trapping: the exhaust valve 16 is opened, the steam in the drying chamber enters the trap, and condenses on the surface of the cold trap, the pressure in the drying chamber drops, and the condensate on the surface of the food and inside the pore evaporates. The food temperature has dropped. During this process, the water temperature setting of the heating plate is lowered to 40 ° C, and the temperature of the heating plate is lowered.

g) De-vacuum: When the pressure in the drying chamber drops to 1500 Pa, the steam trapping process ends. The temperature of the food dropped to 45 ° C, and the condensed water on the surface of the food and inside the pores all evaporated. After the exhaust valve 16 is closed, the inlet air valve 15 is opened to release the vacuum state of the drying chamber. At the same time, the second negative pressure steam valve 39 is opened to defrost the ice layer which is not melted on the surface of the cold trap until the ice layer on the surface of the cold trap is completely melted, and the second negative pressure steam valve 39 is closed.

h) After the vacuum condition of the drying chamber is released, the food and its load are taken out, and the food is processed and packaged. The exhaust valve 16 and the drain valve 46 are opened to discharge the water in the trap.

After testing, the above materials are freeze-dried and sterilized by the method of vacuum freeze-drying and sterilization of the food provided by the embodiments of the present invention, the water content of the raw materials is reduced from 72% to 4%, and the number of implanted Enterococcus faecalis is reduced. 5 logarithmic units, and the sterilization process ensures maximum quality of the food.

The above is a preferred embodiment of the present invention, and it should be noted that those skilled in the art can make several improvements and retouchings without departing from the principles of the present invention. It is also considered to be the scope of protection of the present invention.

Claims

A food vacuum freeze drying and sterilization method, characterized in that it comprises:

Pretreating the material, freezing the material to be treated to below the eutectic point temperature and then feeding it into the drying chamber;

The material is evacuated in the drying chamber, and the material absorbs heat under vacuum to sublimate the ice in the material into water vapor and escape from the material and desublimate;

After the material reaches the required degree of dryness, the drying chamber is filled with negative pressure saturated steam, the steam is condensed on the surface of the material and the internal pores, the temperature of the material rises to the desired pasteurization temperature, and the pasteurization temperature is maintained. Stop charging the negative pressure saturated steam after a period of time;

The water vapor in the drying chamber is captured to reduce the pressure in the drying chamber, and the condensed water on the surface of the material and the internal pores evaporates, and the material is cooled;

After the pressure in the cabin drops to the required steam trapping pressure, the air is filled, the vacuum state in the drying chamber is released, and the freeze-drying and sterilization process is ended.
The food vacuum freeze-drying and sterilizing method according to claim 1, wherein the pressure in the drying chamber is 13 to 130 Pa after the material is evacuated in the drying chamber.
The food vacuum freeze-drying and sterilizing method according to claim 1, wherein the pasteurization temperature is 60 to 90 °C.
The food vacuum freeze-drying and sterilizing method according to claim 1, wherein the pasteurization temperature is maintained for 10 to 90 minutes.
The food vacuum freeze-drying and sterilizing method according to claim 1, wherein the pressure of the negative pressure saturated steam corresponds to a temperature of saturated water that is 0 to 10 ° C higher than the pasteurization temperature.
The food vacuum freeze-drying and sterilizing method according to claim 1, wherein the steam trapping pressure is 100 to 3000 Pa.
a food vacuum freeze-drying and sterilizing apparatus, comprising: a drying chamber connected by a pipe, a heating device, a vacuum steam device, and a vacuum steam catching device, wherein the heating device is connected to the negative pressure steam device to provide Generating heat energy of the negative pressure saturated steam, the negative pressure steam device is connected to the drying chamber to steam sterilize the contents of the drying chamber, and the vacuum trap is connected to the drying chamber for catching The water vapor in the drying chamber is collected to reduce the pressure in the drying chamber.
A food vacuum freeze-drying and sterilizing apparatus according to claim 7, wherein said drying chamber comprises a cylinder, and said cylinder body is internally provided with a heating plate assembly, said heating plate assembly having a pipe and a pipe a water inlet port and a water outlet port connected to the heating device, the cylinder body is provided with an inlet port connected to the vacuum steam device, and an exhaust port connected to the vacuum trap device; There is also an inlet air valve connected to the inlet air port.
The food vacuum freeze-drying and sterilizing apparatus according to claim 8, wherein the food vacuum freeze-drying and sterilizing apparatus further comprises a control device, wherein the cylinder is internally provided with a connection with the control device A temperature sensor and a vacuum pressure sensor for collecting data.
The food vacuum freeze-drying and sterilizing apparatus according to claim 8, wherein the outer surface of the cylinder is fixedly connected with a heat exchange tube uniformly distributed, and the water inlet and the water outlet of the heat exchange tube are respectively The steam generating device is connected to the pipeline.
The food vacuum freeze-drying and sterilizing apparatus according to claim 8, wherein the inside of the cylinder body is provided with a counter-radiation plate, and the heat-insulating pad is arranged between the anti-radiation plate and the cylinder body. .
A food vacuum freeze-drying and sterilizing apparatus according to claim 8, wherein said heating means comprises a soda water heat exchanger, and an inlet of the steam inlet side of said steam-water heat exchanger is connected to a high pressure through a steam regulating valve a steam source, the outlet is connected to a steam trap through a first one-way valve; an outlet of one side of the output water of the steam-water heat exchanger is connected to the water inlet port of the heating plate assembly, and the input water of the steam-water heat exchanger The inlet of one side is connected to a circulating water pump, a hot water side of a cooling heat exchanger and the water outlet port of the heating plate assembly through a pipeline; between the inlet and the outlet of the hot water side of the cooling heat exchanger A bypass valve is connected through the bypass line; a cooling water pump is connected to the inlet of the cooling water side of the cooling heat exchanger.
A food vacuum freeze-drying and sterilizing apparatus according to claim 9, wherein said negative pressure steam device comprises a steam generator, and said hot water outlet of said steam generator is connected to a heat pump and said a water inlet port of the heat exchange tube on the surface of the cylinder; a hot water inlet of the steam generator is connected to a water outlet port of the heat exchange tube; and the steam generator is provided with an automatic connection with a water inlet pipe a water supply valve; a coil heater is disposed inside the steam generator, the inlet of the coil heater is connected to a high pressure steam source through a steam regulating valve, and the outlet of the coil heater passes through a second check valve Connected to a trap; the temperature sensor for measuring the temperature of the water is disposed in the steam generator chamber, and the temperature sensor is coupled to the control device.
A food vacuum freeze-drying and sterilizing apparatus according to claim 7, wherein said vacuum trapping device comprises a trap, and one side of said trap is provided with exhaust gas from said drying chamber An open hole connected to the valve, the other side of which is in communication with a vacuum pump through an evacuation valve; a trap having a plurality of sets of metal coils or metal plates placed inside the chamber of the trap, the inside of the cold trap Circulating a refrigerant, the outlet of the cold trap is connected to a refrigerating device through a refrigerant valve; the chamber of the trap is provided with an opening for connecting a negative pressure steam valve of the negative pressure steam device; The lower portion of the trap is also provided with a drain valve.
A food vacuum freeze-drying and sterilizing apparatus according to claim 14, wherein said trap is disposed inside or outside said drying capsule body.