Sweet potato storage pretreatment equipment and pretreatment method

Abstract

The present invention relates to the field of sweet potato storage technology, and discloses a sweet potato storage pretreatment device and a pretreatment method, wherein the sweet potato storage pretreatment device comprises a callus chamber and a cooling chamber with inlet and outlet doors arranged opposite to each other, the end of the callus chamber away from the cooling chamber is connected to a first air supply fan, a heating device is installed between the outlet of the first air supply fan and the callus chamber; the end of the cooling chamber away from the callus chamber is connected to a second air supply fan. The sweet potato storage pretreatment device can effectively accelerate the formation of sweet potato root callus tissue and shorten the pretreatment time by pretreatment of sweet potatoes with high temperature and short-time callus-cooling before post-harvest storage using a green and pollution-free physical method, thereby achieving the purpose of reducing sweet potato storage decay and water loss, ensuring storage quality, and extending the storage period.

Description

Technical Field

[0001] The invention relates to the technical field of sweet potato storage, and in particular to sweet potato storage pretreatment equipment and a pretreatment method. Background Art

[0002] Sweet potato tubers are large in size, contain a lot of water, have thin skin and tender flesh. They are susceptible to mechanical damage such as abrasions, punctures, cuts, bruises and crushing during field harvesting, transportation and storage. In order to reduce the loss of sweet potatoes after harvest and prevent the invasion of pathogens, the sweet potatoes should be properly pretreated after harvest, cleaned to remove soil-borne microorganisms on the surface, and promoted to heal the wound before storage, which helps to improve the disease resistance of sweet potatoes, extend the storage period and ensure the storage quality. The pretreatment methods currently used in production practice mainly include callus pretreatment, cleaning pretreatment and chemical agent pretreatment.

[0003] Callus pretreatment is mainly based on the traditional low-temperature heating callus pretreatment technology. This technology usually involves picking the sweet potatoes and directly piling them up in storage facilities. After the sweet potatoes are stored, the temperature is raised to 30℃~37℃. The treatment time is usually 2~7 days, and then ventilation and cooling are carried out to enter the storage cycle. Currently, there is no special equipment for callus pretreatment of sweet potatoes on the market and in research. Traditional low-temperature heating callus is usually carried out in heated cold storage or earth pits.

[0004] Chemical reagent pretreatment mainly involves spraying chemicals to stimulate wound healing. Chemical treatment usually involves spraying or soaking exogenous hormones such as abscisic acid (ABA), benzothiazole (BTH) and salicylic acid (SA) before storage. The potatoes are then dried and stored in warehouses. This method mainly involves stimulating the sweet potatoes with exogenous chemical reagents to promote self-healing of wounds during storage.

[0005] Cleaning pretreatment mainly includes water cleaning or chemical cleaning, which mainly relies on water flushing, sodium hypochlorite solution flushing, lime spraying, pesticide soaking or spraying, and fungicide flushing to remove the soil on the surface of the sweet potato and inactivate soil-borne microorganisms, then drain and store them in warehouses.

[0006] At present, the above three mainstream pretreatment methods all have some defects, resulting in poor storage effect of sweet potatoes. Low-temperature heating callus pretreatment has a long cycle, large human and material resources, difficult to control conditions, high energy consumption, uneven callus effect, and unobvious cooling effect, resulting in the final sweet potato residual temperature cannot be dissipated, easy to rot during storage, and unable to meet production needs. Cleaning pretreatment and chemical agent pretreatment involve food safety and irregular use of chemical reagents. Exogenous hormone drugs are expensive, and spraying, soaking and other methods are prone to cause the surface of sweet potatoes to be moist, and the draining time is insufficient, which will accelerate the rot during storage. Summary of the invention

[0007] The embodiment of the invention provides a sweet potato storage pretreatment device and a pretreatment method, which are used to solve the problems that the existing sweet potato pretreatment has a long treatment cycle, poor effect and cannot meet production needs.

[0008] An embodiment of the present invention provides a sweet potato storage pretreatment device, comprising a healing chamber and a cooling chamber with entry and exit doors arranged opposite to each other, wherein the end of the healing chamber away from the cooling chamber is connected to a first air supply fan, and a heating device is installed between the outlet of the first air supply fan and the healing chamber; the end of the cooling chamber away from the healing chamber is connected to a second air supply fan.

[0009] The embodiment of the present invention also provides a pretreatment method using the sweet potato storage pretreatment equipment as described above, comprising:

[0010] Wash the sweet potatoes after being put into the basket;

[0011] The cleaned sweet potato basket containing sweet potatoes is sent into a callus room, wherein the temperature in the callus room is 60° C. to 65° C., the relative humidity is 20% to 30%, and the wind speed is at least 0.5 m / s, and the callus treatment is performed for 20 min to 40 min;

[0012] The sweet potatoes after callus treatment are moved into a cooling room, wherein the temperature of the cooling room is 15° C. to 20° C., the relative humidity is 20% to 30%, and the wind speed is at least 0.5 m / s, for cooling treatment;

[0013] After the temperature of the sweet potatoes drops below 18° C., the sweet potatoes are taken out for storage.

[0014] The sweet potato storage pretreatment equipment and pretreatment method provided by the embodiment of the present invention, wherein the sweet potato storage pretreatment equipment performs high-temperature short-time callus treatment on the sweet potato through a callus chamber, uses heat shock to regulate metabolic pathways and high-temperature to kill epidermal microorganisms, so that the injured periderm of the sweet potato heals quickly, forming a biological barrier to resist external disease microorganisms, and then uses a cooling chamber to quickly cool the callus-injured sweet potato with strong wind, quickly reducing the residual temperature of the callus-injured sweet potato, avoiding the increase and loss of respiratory intensity during storage, and reducing the rot in the early stage of storage. The sweet potato storage pretreatment equipment can effectively accelerate the formation of sweet potato root callus tissue and shorten the pretreatment time by performing high-temperature short-time callus-cooling pretreatment on the sweet potato before postpartum storage with a green and pollution-free physical method, thereby achieving the purpose of reducing the rot and water loss of the sweet potato during storage, ensuring the storage quality, and extending the storage period. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 It is a structural schematic diagram of a sweet potato storage pretreatment device in an embodiment of the present invention;

[0017] Figure 2 yes Figure 1 A top view of the sweet potato storage pretreatment equipment;

[0018] Figure 3 This is a process flow chart of a pretreatment process of sweet potatoes before storage in an embodiment of the present invention;

[0019] Figure 4 Schematic diagram of stacking the same batch of sweet potatoes when using the sweet potato storage pretreatment equipment in an embodiment of the present invention, wherein a represents the upper sweet potato sampling point, b represents the middle sweet potato sampling point, and c represents the bottom sweet potato sampling point;

[0020] Figure 5 It is a temperature monitoring change result diagram of each temperature sensor in the healing chamber of the present invention;

[0021] Figure 6 It is a humidity monitoring change result diagram of each humidity sensor in the wound healing chamber of the present invention;

[0022] Figure 7 It is a graph showing the measurement results of the skin and core temperatures of the same batch of sweet potatoes at different placement points after the callus treatment of the present invention;

[0023] Figure 8 This is a graph showing the temperature measurement results of the skin and the core of the same batch of sweet potatoes at different placement points after the cooling treatment of the present invention;

[0024] Fig. 9 This is a graph showing the L* value test results after storage of Example 1 and Comparative Examples 1 to 4;

[0025] Fig.10 This is a graph showing the a* value test results after storage of Example 1 and Comparative Examples 1 to 4;

[0026] Fig.11 This is a graph showing the b* value test results after storage of Example 1 and Comparative Examples 1 to 4;

[0027] Fig.12 This is a graph showing the browning degree test results of sweet potatoes after storage in Example 1 and Comparative Examples 1 to 4;

[0028] Fig.13 1 is a graph showing the respiration intensity test results of sweet potatoes after storage in Example 1 and Comparative Examples 1 to 4;

[0029] Fig.14 1 is a graph showing the results of the internal hardness test of the sweet potato tissue after storage in Example 1 and Comparative Examples 1 to 4;

[0030] Fig.15 is a graph showing the results of the head and tail hardness test of sweet potatoes after storage in Example 1 and Comparative Examples 1 to 4;

[0031] Fig.16 1 is a graph showing the results of the sweet potato cell membrane permeability test after storage of Example 1 and Comparative Examples 1 to 4;

[0032] Fig.17 This is a graph showing the test results of malondialdehyde content in sweet potatoes after storage in Example 1 and Comparative Examples 1 to 4;

[0033] Fig.18 1 is a graph showing the test results of the incidence of chilling injury of sweet potatoes after storage in Example 1 and Comparative Examples 1 to 4;

[0034] Fig.19 It is a test result diagram of the rot rate of sweet potatoes after storage of Example 1 and Comparative Examples 1 to 4;

[0035] Fig. 20 This is a graph showing the weight loss rate test results of sweet potatoes after storage in Example 1 and Comparative Examples 1 to 4;

[0036] Fig.21 It is a graph showing the test results of the sweet potato starch content after storage of Example 1 and Comparative Examples 1 to 4;

[0037] Fig. 22 It is a test result diagram of soluble sugar content of sweet potatoes after storage in Example 1 and Comparative Examples 1 to 4;

[0038] Fig.23 It is a graph showing the test results of ascorbic acid content of sweet potatoes after storage in Example 1 and Comparative Examples 1 to 4.

[0039] Description of reference numerals:

[0040] 1. Healing room; 2. Cooling room; 3. First air supply fan;

[0041] 4. Second air supply fan; 5. Main air supply duct; 6. Heating device;

[0042] 7. Return air duct; 8. Downward air supply duct; 9. Top window;

[0043] 10. Three-way regulating valve; 11. Front-end temperature and humidity sensor; 12. End temperature and humidity sensor;

[0044] 13. Electric air inlet valve; 14. Dehumidification fan; 15. Slide rail;

[0045] 16. Sweet potato basket; 17. Air outlet valve of healing chamber; 18. Air outlet of cooling chamber;

[0046] 19. Air scoop; 20. Cleaning room; 21. Sprinkler head;

[0047] 22. Drain outlet; 23. Control box; 24. Wet curtain. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "first" and "second" are for the purpose of clearly describing the numbering of product components and do not represent any substantial difference. The terms "upper", "lower", "left", "right", etc. are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0050] It should be noted that, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense, for example, it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the invention can be understood in specific circumstances.

[0051] like Figure 1 to Figure 2 As shown, a sweet potato storage pretreatment device provided by an embodiment of the present invention comprises a healing chamber 1 and a cooling chamber 2 with inlet and outlet doors arranged opposite to each other, a first air supply fan 3 is connected to the end of the healing chamber 1 away from the cooling chamber 2, and a heating device 6 is installed between the outlet of the first air supply fan 3 and the healing chamber 1. A second air supply fan 4 is connected to the end of the cooling chamber 2 away from the healing chamber 1.

[0052] Specifically, the healing chamber 1 and the cooling chamber 2 are arranged opposite to each other. Both the healing chamber 1 and the cooling chamber 2 can be hollow boxes with openings at both ends. The size of the boxes can be reasonably designed according to needs. In a specific embodiment, the volume of the healing chamber 1 and the cooling chamber 2 is 12m 3 , and can process 700kg to 800kg of sweet potatoes at one time.

[0053] The end of the healing chamber 1 away from the cooling chamber 2 is connected to the outlet of the first air supply fan 3 through the wind scoop 19, the heating device 6 and the main air supply pipe 5 in sequence; the end of the healing chamber 1 facing the cooling chamber 2 is provided with a first inlet and outlet door that can be opened and closed. After opening the first inlet and outlet door, the sweet potatoes to be processed can be placed in the healing chamber 1, and the sweet potatoes after the healing process are completed can also be moved out of the healing chamber 1. In addition, a healing chamber air outlet valve 17 can be installed on the first inlet and outlet door, and the healing chamber air outlet valve 17 can be a manual air valve or an electric air valve. By opening the first air supply fan 3 and the healing chamber air outlet valve 17 (or directly opening the first inlet and outlet door), a tunnel ventilation mode can be formed in the healing chamber 1. The first air supply fan 3 can be a centrifugal fan, and a frequency converter can be added as needed to adjust the wind speed in the healing chamber 1. The heating device 6 can be an electric heater, and more specifically, the electric heater can use a PTC thermistor material as a heating element, and at the same time has a strengthened overload protection function.

[0054] The end of the cooling chamber 2 facing away from the healing chamber 1 is connected to the outlet of the second air supply fan 4 through the wind scoop 19 and the air supply pipe in turn; the cooling chamber 2 is provided with a second inlet and outlet door that can be opened and closed at the end facing the healing chamber 1. After opening the second inlet and outlet door, the sweet potatoes after the healing process can be placed in the cooling chamber 2, or the sweet potatoes after the cooling process can be moved out of the cooling chamber 2 and finally placed in a storage cellar or a cold storage for storage. In addition, a cooling chamber air outlet 18 can also be installed on the second inlet and outlet door, and the cooling chamber air outlet 18 can be a shutter air outlet or other air outlet structure. By opening the second air supply fan 4 and the cooling chamber air outlet 18 (or directly opening the second inlet and outlet door), a tunnel ventilation mode can be formed in the cooling chamber 2. The second air supply fan 4 can be a centrifugal fan, and a frequency converter can be added as needed to adjust the wind speed in the cooling chamber 2.

[0055] When in use, the sweet potatoes can be first put into baskets in the area between the callus chamber 1 and the cooling chamber 2, and after being neatly stacked, they can be moved to the left to the callus chamber 1 for callus treatment. After the callus treatment is completed, the sweet potatoes can be directly moved to the right from the callus chamber 1 to the cooling chamber 2 for cooling treatment. After the cooling treatment is completed, they can be unloaded from the area between the callus chamber 1 and the cooling chamber 2. In addition, the callus chamber 1 and the cooling chamber 2 can be put into use simultaneously and continuously. When the cooling chamber 2 is processing the previous batch of sweet potatoes, the next batch of sweet potatoes can be moved to the callus chamber 1 for callus treatment, thereby improving the overall processing speed.

[0056] The present embodiment provides a kind of sweet potato storage pretreatment equipment, which performs high-temperature short-time callus treatment on sweet potatoes through the callus chamber 1, uses heat shock to regulate metabolic pathways and high temperature to kill epidermal microorganisms, so that the injured periderm of the sweet potato can heal quickly, forming a biological barrier against external disease microorganisms, and then uses strong wind to quickly cool the callus-injured sweet potatoes through the cooling chamber 2, so as to quickly reduce the residual temperature of the callus-injured sweet potatoes, avoid the increase and loss of respiratory intensity during storage, and reduce the rot in the early stage of storage. The sweet potato storage pretreatment equipment can effectively accelerate the formation of sweet potato root callus tissue and shorten the pretreatment time by performing high-temperature short-time callus-cooling pretreatment on sweet potatoes before postpartum storage with a green and pollution-free physical method, thereby achieving the purpose of reducing sweet potato storage rot and water loss, ensuring storage quality, and extending the storage period.

[0057] Furthermore, if Figure 1 and Figure 2 As shown, it also includes a slide rail 15 and a loading trolley (not shown in the figure), one end of the slide rail 15 extends into the healing chamber 1, and the other end of the slide rail 15 extends into the cooling chamber 2. The loading trolley can slide along the slide rail 15. Specifically, the loading trolley can be an electric flatbed truck or a trolley, and the loading trolley can easily and labor-savingly realize the translation of sweet potatoes between the healing chamber 1 and the cooling chamber 2. A plurality of sweet potato baskets 16 made of plastic material can be loaded on the loading trolley.

[0058] Furthermore, if Figure 1 As shown, a return air duct 7 is provided above the healing chamber 1, the inlet of the return air duct 7 is connected to the inner chamber of the healing chamber 1, and the outlet of the return air duct 7 is connected to the inlet of the first air supply fan 3. A lower air supply duct 8 is provided below the healing chamber 1, the inlet of the lower air supply duct 8 is connected to the outlet of the heating device 6, and the outlet of the lower air supply duct 8 is connected to the inner chamber of the healing chamber 1. By providing the lower air supply duct 8 and the return air duct 7, hot air can pass through the inner chamber of the healing chamber 1 from bottom to top, forming a box-type ventilation mode.

[0059] Furthermore, if Figure 1 and Figure 2 As shown, a plurality of openable top windows 9 are installed on the top of the healing room 1 in the length direction, and the inlet of the return air duct 7 is connected to the inner chamber of the healing room 1 through the top window 9. The top window 9 can be a manual push window or an electric push window. The return air duct 7 can be provided with a plurality of inlets, and each inlet is arranged one by one with the top window 9. The lower air supply duct 8 can also be provided with a plurality of outlets along the length direction of the healing room 1 to ensure uniform air discharge.

[0060] Furthermore, if Figure 1 As shown, the outlet of the heating device 6 is connected to the inlet of the lower air supply duct 8 and the air inlet of the healing chamber 1 through the three-way regulating valve 10. Specifically, the valve body of the three-way regulating valve 10 can be directly integrated with the wind scoop 19, the lower air supply duct 8 is arranged in the wind scoop 19 and forms an intersection at the neck of the wind scoop 19, and the three-way regulating valve 10 also includes a valve plate rotatably arranged at the intersection, and the rotating shaft of the valve plate can extend to the outside of the wind scoop 19 to form a handle, or can be directly connected to a motor to achieve electric control.

[0061] By rotating the valve plate, the inlet of the lower air supply duct 8 can be completely blocked. At this time, the air outlet of the first air supply fan 3 enters the inner chamber from the air inlet of the healing chamber 1, forming tunnel ventilation; or the valve plate can completely block the air inlet of the healing chamber 1. At this time, the air outlet of the first air supply fan 3 enters the inner chamber from the lower air supply duct 8, and the top window 9 can also be opened in conjunction with the three-way regulating valve 10 (or opened manually alone), thereby forming box ventilation; or the valve plate can be kept in the middle position, so that the air outlet can enter the inner chamber of the healing chamber 1 from the air inlet of the healing chamber 1 and the lower air supply duct 8 at the same time, forming tunnel and box synchronous ventilation. Generally, when the sweet potato processing volume is small, tunnel ventilation can be used alone; when the sweet potato processing volume is large, box ventilation can be used alone. The hot air can be recycled through box ventilation, which is beneficial to improve the heat utilization rate and save energy.

[0062] Furthermore, if Figure 1 and Figure 2As shown, a cleaning chamber 20 is also included between the healing chamber 1 and the cooling chamber 2, and a plurality of spray heads 21 are installed in the cleaning chamber 20. The spray heads 21 can be used to rinse the sweet potatoes loaded in the sweet potato basket 16 with clean water, so that all large pieces of dirt on the surface of the sweet potatoes are washed away. A drain port 22 is also provided at the bottom of the cleaning chamber 20, and the sewage accumulated in the cleaning chamber 20 is discharged in time through the drain port 22, and can be collected and processed in a centralized manner.

[0063] Furthermore, if Figure 1 As shown, a temperature sensor and a humidity sensor are installed in the healing chamber 1, and the healing chamber 1 is also equipped with an electric air inlet valve 13 and a dehumidification fan 14 connected to the control box 23. Specifically, the front section, middle section and end section, the upper and lower parts, and the left and right sides of the healing chamber 1 can be provided with temperature sensors and humidity sensors as needed. In a specific embodiment, the front section of the healing chamber 1 is provided with a front temperature and humidity sensor 11, and the end section is provided with a terminal temperature and humidity sensor 12. The temperature sensor, the humidity sensor, the first air supply fan 3, the heating device 6, the electric air inlet valve 13 and the dehumidification fan 14 are all electrically connected to the control box 23 installed outside the healing chamber 1. When the humidity in the healing room 1 is higher than the set humidity, the humidity sensor collects data to the control box 23. After judgment, the control box 23 issues a command to open the electric air inlet valve 13 and the dehumidification fan 14. The outside air enters the healing room through the electric air inlet valve 13, and the indoor humid air is discharged from the healing room 1 through the dehumidification fan 14. When the humidity in the healing room 1 is lower than or equal to the set humidity, the electric air inlet valve 13 and the dehumidification fan 14 are stopped. The temperature and humidity in the healing room 1 are controlled by the temperature sensor and the humidity sensor to keep them appropriate. Further, if Figure 1 As shown, a wet curtain 24 is installed between the outlet of the second air supply fan 4 and the cooling chamber 2. Specifically, the wet curtain 24 can be installed in the wind scoop 19. The wet curtain 24 can provide cooling capacity for the cooling chamber 2. When the air supply of the second air supply fan 4 passes through the wet curtain 24, a large amount of water evaporates, thereby reducing the air supply temperature, and then enters the cooling chamber 2, causing the indoor temperature to drop rapidly. Sweet potatoes are generally harvested and stored in the autumn in the north. At this time, the ambient temperature is relatively low, about 15°C to 20°C, and the wind at the ambient temperature can be used to cool the sweet potatoes. If the equipment is put into use in the south or in summer, it can be considered to install or invest in a wet curtain 24.

[0064] Furthermore, the outsides of the healing chamber 1 and the cooling chamber 2 are both provided with a heat-insulating layer, which is composed of three layers from the outside to the inside, namely, a color steel plate, a heat-insulating benzene plate and a snowflake plate lining.

[0065] like Figure 3 As shown, the embodiment of the present invention also provides a pretreatment method using the sweet potato storage pretreatment equipment as described above, comprising:

[0066] Step S300: Clean the sweet potatoes after being put into the basket. Specifically, the cleaning can be performed directly in the cleaning chamber 20, or manually outside the equipment.

[0067] Step S400: Send the cleaned sweet potato basket containing sweet potatoes into the callus chamber 1, where the temperature in the callus chamber 1 is 60°C to 65°C, the relative humidity is 20% to 30%, and the wind speed is at least 0.5 m / s, and the callus treatment is performed for 20min to 40min.

[0068] Step S500: moving the sweet potato after the callus treatment into a cooling chamber 2, wherein the temperature of the cooling chamber 2 is 15° C. to 20° C., the relative humidity is 20% to 30%, and the wind speed is at least 0.5 m / s, for cooling treatment;

[0069] Step S600: After the temperature of the sweet potatoes drops below 18° C., take out the sweet potatoes for storage.

[0070] Furthermore, before step S300, the method further includes:

[0071] Step S100: Clean the harvested fresh sweet potatoes, remove soil impurities on the surface, and remove sweet potatoes with diseases and insect pests.

[0072] Step S200: The selected sweet potatoes are placed in the sweet potato baskets 16 respectively. The height of the sweet potato baskets is less than or equal to two-thirds of the height of the sweet potato baskets 16. After the baskets are filled, they are placed in a cool and ventilated place for processing.

[0073] The following is explained with reference to a specific embodiment.

[0074] The variety of sweet potato tubers used in this embodiment is red sweet potato 'Yanshu 25', produced in Sishui, Shandong. This embodiment provides a method for pretreating damaged sweet potatoes, comprising the following steps:

[0075] Step S100, selection: cleaning the soil impurities on the surface of the sweet potato tubers of the harvested fresh sweet potatoes (including damaged sweet potatoes), and removing the sweet potatoes with diseases and insect pests.

[0076] Step S200, basketing: put sweet potatoes of different specifications into sweet potato baskets 16 (length×width×height of 510mm×320mm×155mm), respectively. Figure 4 As shown, the sweet potato basket is not higher than the two-thirds position in the sweet potato basket 16 ( Figure 4 Each batch of sweet potatoes is stacked in twelve baskets. After the baskets are loaded, they are placed in a cool and ventilated place for processing.

[0077] Step S300, cleaning: rinse the loaded sweet potatoes with clean water to remove all the large pieces of dirt on the surface of the sweet potatoes; the cleaning can be done manually outside the equipment, or the loaded sweet potato baskets 16 can be directly stacked in two rows horizontally and vertically (such as Figure 4 As shown), and placed on the loading trolley of the above-mentioned sweet potato storage pretreatment equipment, and pushed into the cleaning chamber 20 for automatic cleaning.

[0078] Step S400, high temperature short-time callus pretreatment: The treatment site of this experiment is located at the pilot test site in Sishui, Shandong. On October 20, 2019, the local temperature was 15.5°C. Half an hour before the treatment, the heating device 6 is turned on for preheating, and the first air supply fan 3 and the second air supply fan 4 are started at the same time to adjust the wind speed. Then the loading trolley loaded with sweet potatoes is sent into the callus chamber 1 through the slide rail 15, and the sweet potatoes are placed in a constant temperature and humidity callus chamber 1 with a temperature of 60°C to 65°C, a relative humidity of 20% to 30%, and a wind speed of 0.5m / s for heat shock treatment for 25min.

[0079] Step S500, cooling pretreatment: the wounded sweet potatoes are placed on the cart and then enter the cooling chamber 2 with strong wind rapid cooling along the slide rail 15, the temperature is the ambient temperature, the relative humidity is 20% to 30%, the wind speed is 1m / s, and the cooling treatment is carried out for 10 minutes.

[0080] Step S600, storage: after the temperature of the sweet potato root tubers drops below 18°C, they are stored in a storage cellar or cold storage at a temperature of 13±1°C and a relative humidity of 80% to 90%.

[0081] (I) Equipment performance verification: The following tests the equipment temperature and humidity parameters during the healing and cooling process of the sweet potatoes after selection, basketing and cleaning in the sweet potato storage pretreatment equipment of this embodiment to illustrate the stability of the equipment during the healing and cooling process and the uniformity of the sweet potatoes after pretreatment.

[0082] (1) Selection and basketing: Fresh sweet potatoes with regular appearance, uniform size (weight 200g-300g), no damage and no pests and diseases are selected from the fields. They are harvested in Sishui, Shandong and basketed according to Figure 4 The method shown is carried out and waits for the equipment to be pre-processed.

[0083] (2) High temperature short-time wound healing-strong wind cooling pretreatment: The sweet potatoes were pretreated according to the pretreatment method of the above embodiment.

[0084] (3) Equipment data collection: During the actual operation of the equipment, the temperature and humidity data collected by each temperature and humidity sensor probe in the healing chamber 1 are collected and recorded every minute.

[0085] (4) Determination of sample surface and core temperature: After each batch of sweet potatoes was subjected to heat shock callus pretreatment or cooling pretreatment according to the pretreatment method of the above embodiment, Figure 4 The surface temperature and the core temperature of the sweet potatoes in the upper, middle and lower layers of the same batch of 12 baskets in two rows are measured in the following manner: immediately after the pre-treated sweet potatoes are taken out of the sweet potato basket 16, three points are randomly measured at the upper, middle and lower sides of each sweet potato using a probe thermometer, and the surface and internal temperatures are recorded respectively, and the average value of all sampling points is calculated.

[0086] Figure 5 It shows the change of temperature detected by each temperature sensor probe in the callus chamber 1 during the high-temperature short-time callus of the sweet potato in the callus chamber 1. The test results show that the callus chamber 1 in the equipment has uniform temperature control and small fluctuations during the "high-temperature short-time callus" process. Among the temperature monitored by the temperature sensors in six different positions, including the top, bottom, front, middle and back, the highest was 64.84°C and the lowest was 63.02°C, with a temperature difference of only 1.82°C. The test results show that the callus chamber 1 in the equipment of the present invention has good temperature stability when processing 750kg of results in large quantities, and can evenly heat and heat-shock the sweet potatoes in different positions to ensure the heat-shock effect.

[0087] Figure 6 It shows the change of humidity detected by each humidity sensor probe in the callus chamber 1 during the high-temperature short-time callus of the sweet potato. Since the pretreatment process of the equipment involves a cleaning process, a large amount of moisture will be attached to the surface of the sweet potato, which will not only affect the processing uniformity of the subsequent "high-temperature short-time heat shock" process, but also cause a high humidity load on the components inside the equipment, affecting the service life of the equipment. Therefore, the above problems can be solved by setting an electric air inlet valve and a dehumidification fan in the equipment. The test results show that the humidity of the callus chamber 1 in the equipment is well controlled during the "high-temperature short-time callus" process. The average humidity of the six probes is 25.45%, and the humidity fluctuation is within 2.5%. The test results show that the callus chamber 1 in the equipment of the present invention has good humidity stability when processing 750kg in large quantities, and will not cause the problem of excessive humidity in the narrow chamber, thereby ensuring the heat shock effect.

[0088] Figure 7It shows the temperature of the sweet potato skin and the core (i.e., the center of the sweet potato) after the batch of sweet potatoes has undergone the high-temperature short-time callus process in the callus chamber 1. After the heat shock pretreatment in the callus chamber 1, the skin temperature of the sweet potato is generally lower than the core temperature, and the skin temperature is between 37.78℃ and 39.70℃, and the difference in the sweet potato skin temperature at each sampling point does not exceed 2℃; the core temperature is between 40.22℃ and 40.88℃, and the difference in the sweet potato core temperature at each sampling point does not exceed 0.7℃. The test results show that the "high-temperature short-time heat shock" equipment in the equipment of the present invention has a uniform heating effect on the sweet potato, and there is no large temperature difference, which ensures that the sweet potatoes at different positions in the same batch can be well heat-shocked.

[0089] Figure 8 It shows the temperature of the sweet potato skin and the core (i.e., the center of the sweet potato) after the batch of sweet potatoes has been rapidly cooled by the strong wind in the cooling chamber 2. In the traditional sweet potato pretreatment process, there is no special design for the cooling process after heating, which usually leads to uneven heat dissipation of the stacked sweet potatoes after heating, and slow heat dissipation during storage, which stimulates the premature aging of the sweet potatoes and the formation of respiratory condensation water on the surface of the sweet potatoes, thereby causing a large amount of rotting. In the integrated pretreatment equipment of the present invention, the sweet potatoes are specially cooled by the cooling chamber 2. The test results show that after the cooling pretreatment in the cooling chamber 2, the skin temperature of the sweet potatoes is also lower than the core temperature. The skin temperature drops rapidly from 37.78℃ to 39.70℃ after heat shock to 14.82℃ to 15.44℃, and the difference in the skin temperature of the sweet potatoes at each sampling point does not exceed 1℃; the core temperature drops from 40.22℃ to 40.88℃ after heat shock to 15.26℃ to 16.58℃, and the difference in the core temperature of the sweet potatoes at each sampling point does not exceed 1.5℃. The test results show that the "cooling" device in the equipment of the present invention has an obvious cooling effect on the sweet potatoes after heat shock, and the cooling effect is uniform without a large temperature difference, ensuring that the sweet potatoes in different positions of the same batch can be well cooled and pre-treated, thereby ensuring the quality of the sweet potatoes during the storage process.

[0090] (II) Testing and verification of various properties of sweet potatoes after pretreatment: The following is a comparative verification of various performance indicators of sweet potatoes after wound healing and cooling pretreatment in the sweet potato storage pretreatment equipment through 1 embodiment and 4 comparative examples. In order to avoid the influence of wound differences on the test results, this experiment was conducted on sweet potato tubers after artificial injury.

[0091] The specific method is as follows:

[0092] (1) Selection: Fresh sweet potatoes with regular appearance, uniform size (weight 200 g to 300 g), no damage and no pests and diseases were selected from the fields and harvested locally in Sishui, Shandong.

[0093] (2) Artificial injury: To ensure the accuracy of the experiment, the sweet potatoes used in the experiment were artificially wounded. After the skin scraper and the hole puncher (20 mm in diameter) were wiped and disinfected with 95% ethanol, a circular mark with a radius of 1 cm was made on each sweet potato using the hole puncher, and then a skin scraper was used to scrape a wound with a diameter of 2 cm and a depth of 3 mm on the sweet potato surface along the hole punch mark. Each sweet potato was divided into 6 wounds at the top, middle and bottom; the skin scraper was a stainless steel foot file (190 mm long, 26 mm wide and 15 mm thick).

[0094] (3) Randomly sample the artificially damaged sweet potatoes and use them as samples for Example 1 and Comparative Examples 1 to 4, with 400 sweet potatoes in each group and three replicates.

[0095] Example 1 An experiment was conducted according to the sweet potato storage pretreatment method provided in this embodiment, and steps S100 to S600 were performed in sequence.

[0096] Comparative Example 1 is a blank control without any pretreatment. After steps S100 and S200, no washing-wounding-cooling treatment is performed, and step S600 is directly performed, that is, the sweet potatoes are selected, packed in baskets, and directly placed in an environment with a temperature of 13±1°C and a relative humidity of 80-90%, and stored in a constant temperature artificial climate chamber.

[0097] Comparative Example 2 adopts the most common sweet potato washing-low-temperature short-time callus pretreatment method currently used in commercial, experimental and agricultural applications (actual production and experimental research). The treatment is basically the same as that in Example 1, except that: after steps S100 to S300, in step S400, a long-term low-temperature heat shock treatment is carried out in a storage pit or storage warehouse, the heat shock treatment temperature is 35°C, the heat shock time is 2 days, and then step S500 is not performed, and step S600 is performed directly.

[0098] Comparative Example 3 adopts a commonly used method for cleaning and pre-treating sweet potatoes, which is basically the same as the process of Example 1, except that: after steps S100 to S300, step S600 is directly performed, that is, selection, basketing, cleaning and direct storage are performed.

[0099] Comparative Example 4 adopts a method for pretreating sweet potatoes using the equipment of the present invention but without performing a cleaning step, which is basically the same as the treatment in Example 1, except that: after steps S100 to S200, step S300 is not performed, and steps S400 to S600 are directly performed, that is, after picking and basketing, no cleaning is performed, and the equipment of the present invention is directly used for high-temperature short-time healing and cooling pretreatment, and then storage is performed.

[0100] (3) Test sampling: The day of treatment is designated as Day 0, and the sweet potatoes of Example 1 and Comparative Examples 1 to 4 are sampled every 7 days, with the amount of sweet potatoes of each group sampled each time being not less than 10 kg. The last sampling is on the 35th day of storage, for Tests 1 to 5 (color, browning, respiration, hardness, and cell membrane permeability, respectively). The remaining samples are stored at -20°C and awaiting Tests 6 to 12;

[0101] After 7 days of wound healing (the wound healing period starts from the time of wound formation and ends at the end of storage) in Example 1 and Comparative Examples 1 to 4, samples were taken from each treatment for the remaining tests. Specifically, samples were taken from Example 1 and Comparative Examples 2 to 4 on the 7th day of storage after treatment; samples were taken from Comparative Example 1 on the 5th day of storage after 2 days of heat shock treatment.

[0102] The test results are as follows:

[0103] (a) Test 1: Color test

[0104] The color determination method is as follows: The color difference of the sweet potato wound is determined using a 3nh spectrophotometer, and the L*, a*, and b* values ​​are measured perpendicular to the tissue part of the sweet potato root tuber, and the data are recorded and averaged. 20 sweet potato root tubers are taken for each treatment for determination.

[0105] This test observed the cut surface color of the sweet potato tubers of the embodiment and each comparative example, and found that the L*, a* and b* values ​​of the sweet potatoes after the treatment and storage in Example 1 were obtained by measuring the color difference of the sweet potato flesh tissue during storage, and the effect of heat shock treatment on the color of sweet potatoes during storage was comprehensively analyzed. Figures 9 to 11It can be seen that there is no significant difference in L*, a* and b* values ​​between the groups of sweet potatoes in the early stage of storage (0d, 7d and 14d), but as the storage time increases, the L* and b* values ​​of the sweet potatoes in Comparative Example 1 without any pretreatment show a trend of a sharp increase in a* value. After observation, the color of the sweet potato tissue gradually changes from light brown to brown. The L* values ​​of Comparative Examples 3 and 4 obviously drop to below 60, but are significantly higher than Comparative Example 1. The L* values ​​of Comparative Example 2 and Example 1 maintain the highest brightness after 35 days of storage, and there is no significant difference between the two groups. The results of the L* value show that the four pretreatment methods can effectively improve the final brightness of the fruit compared with the untreated group, and significantly inhibit the process of color dimming, and the brightness improvement of Example 1 and Comparative Example 2 is the greatest. In addition to Comparative Example 1, the a* values ​​of Comparative Examples 3 and 4 also show a trend of a sharp increase, but are less than Comparative Example 1. The a* values ​​of Example 1 and Comparative Example 2 showed a downward trend, indicating that the pretreatment methods of Example 1 and Comparative Example 2 can effectively inhibit the degree of fruit browning and reddening. Except for Comparative Example 1, the b* values ​​of the other four groups were slightly different, and the decline was small, basically maintaining the original color b* value of the sweet potato.

[0106] (b) Test 2: Browning test

[0107] Browning degree determination method: Randomly select 6 sweet potato samples from each treatment group and cut them horizontally. After placing them at room temperature for 4 hours, use a colorimeter to determine the color difference (L*, a*, b*) inside the sweet potato tissue. Calculate the total color difference △E based on the color difference between the two times, which is the browning degree. The calculation formula is as follows:

[0108]

[0109] Where: △L, △a, △b are the color difference values ​​of the sweet potato samples before and after browning.

[0110] Browning is the main characteristic of ripening, aging and physiological decline of fruits and vegetables. During the storage process, as time goes by, the fruit and vegetable tissues are more likely to brown. The main manifestation is the change of fruit and vegetable color from bright to dull. Therefore, the color difference of two sweet potato cross sections under the same conditions and at the same time can be used to calculate the total color difference △E and evaluate the browning degree of sweet potato tubers.

[0111] According to the effect of heat shock treatment on the browning degree of sweet potato during storage, Fig.12It can be seen that the browning degree of the sweet potato tissue shows a gradual upward trend. There is no significant difference between the groups when the storage reaches the 7th day. After that, the browning degree of Example 1 rises sharply and reaches 77.8 when the storage reaches 35 days. However, there is no significant difference between Example 2 and Example 4 at each sampling point, and the browning degree is low, and the browning degree is maintained at about 40 at 35 days. In the process of 0d to 28d, the browning degree of Example 3 is close to that of Example 2 and Example 4, but it increases to 59.0 at 35d, indicating that the sweet potato pretreated with Example 3 is easily affected by browning in the later stage of storage. Example 1 is the most effective group in inhibiting browning among the five pretreatment methods. The browning degree during storage is always maintained at the lowest level. The final browning degree of 35d is 38.9, which is significantly lower than the other four groups. The test experimental results show that the sweet potato treated with the equipment and pretreatment process of the present invention can effectively reduce the browning degree of the sweet potato after storage, which proves that the physiological aging process of the sweet potato is effectively delayed.

[0112] (c) Test 3: Breathing intensity test

[0113] Respiration intensity determination method: Respiration intensity was determined using a fruit and vegetable respirometer (model FS-3080A). Five sweet potatoes were randomly selected from each example, weighed, and placed in the fruit and vegetable respirometer for determination. The respiration intensity of each treatment was calculated using the respiration intensity software, and the average value was taken, repeated three times, and expressed in mg / kg·h.

[0114] The respiratory metabolism of fruits and vegetables is closely related to the synthesis and decomposition of a variety of organic macromolecules. Sweet potatoes without any pretreatment usually have an obvious respiratory peak in the early stage of storage, metabolizing a large amount of carbon dioxide and water vapor. This phenomenon is called "sweating" in actual production. In the case of poor ventilation in storage conditions, a large amount of water vapor condenses and adheres to the surface of the sweet potatoes, which can easily cause rot and have a negative impact on the storage of sweet potatoes. Fig.13From the effects of different pretreatment technologies on the respiration intensity of sweet potatoes during storage, it can be seen that the respiration intensity of sweet potatoes treated in each group shows different trends. The untreated group of Comparative Example 1 showed an obvious respiration peak on the 7th day, after which the respiration intensity continued to decline; the sweet potatoes in the cleaning pretreatment group of Comparative Example 3 also showed a respiration peak on the 7th day of storage, and the peak value of the respiration intensity was significantly higher than that of Comparative Example 1, and showed a downward trend after the respiration peak. This shows that the cleaning treatment may increase the respiration intensity of sweet potatoes due to exogenous physical stimulation. The other three callus pretreatment groups all showed an inhibitory effect on the respiration intensity of sweet potatoes, and no obvious peaks appeared during storage. There was no significant difference in the respiration intensity between Example 1 and Comparative Example 4, and Comparative Example 2 showed a small increase in respiration intensity after 14 days. It shows that the heat shock in the post-harvest callus pretreatment can effectively inhibit the abnormal fluctuation of the respiration intensity of sweet potatoes during storage, and the sweet potato groups (Example 1 and Comparative Example 4) treated by the equipment of the present invention have the most obvious inhibition on the respiration intensity.

[0115] (d) Test 4: Hardness test

[0116] Hardness determination method: Cut the sweet potato into cylinders, take the potato flesh tissues from the head, tail and middle parts of the sweet potato and place them on the loading plate of the texture analyzer respectively, use a cylindrical probe to determine the hardness of the sweet potato tissue and take the average value, which is the hardness of the sweet potato tissue.

[0117] The hardness of fruits and vegetables is an important indicator of their storage quality. During storage, the hardness of fruits and vegetables will gradually decrease and soften as they age. However, sweet potatoes may become flocculated due to water loss, causing their hardness to increase sharply. Fig.14 It can be seen that the hardness of the sweet potato tissue gradually decreases with the extension of storage time. The hardness of the untreated group, Example 1, begins to decrease rapidly after the 7th day, and the final hardness of the middle part of the sweet potato is only 3.87g. This may be due to the fact that the sweet potato wound has not healed completely, the sweet potato defense ability has decreased, and the aging process of the sweet potato has been accelerated. The final hardness of the middle part of the sweet potato after the four pretreatment methods is generally higher than that of Example 1. Among them, the sweet potato hardness of Example 1 decreases the slowest, and the final hardness of the middle part is the highest, reaching 5.91g. Fig.15It can be seen that the hardness of the head and tail parts of the sweet potato has a different trend of change. The hardness of the two ends of the sweet potato in Comparative Examples 1 and Comparative Examples 3 has a sharp upward trend since 21 days. This phenomenon may be caused by two reasons: first, the sweet potato is subjected to low temperature stress during storage, resulting in cold damage to the sweet potato, which causes the two ends to become flocculent and harden; second, the two ends of the sweet potato are the fibrous root parts of the tuber, which are mainly used to absorb soil nutrients, and the cell membrane permeability is strong. During storage, due to improper storage environment, it causes serious water loss and shrinkage, resulting in hardening. However, since the sweet potatoes of Example 1, Comparative Examples 2 and Comparative Examples 4 have all undergone the callus pretreatment process, the hardness of the head and tail parts is consistent with the change trend of the tissue, and the hardness shows a downward trend. Among them, the decline rate of Example 1 is slower, and the final head and tail hardness maintains the highest value, which is consistent with the result of the hardness of the middle part. This shows that the heat shock in the post-harvest callus pretreatment has a positive effect on delaying the decline of the hardness of the sweet potato, and the hardness protection effect of the sweet potato after the equipment pretreatment of the present invention is the best.

[0118] (e) Test 5: Cell membrane permeability test

[0119] Method for determining cell membrane permeability: first use a 15mm diameter puncher to randomly take the potato flesh tissue inside the sweet potato tissue, and then use a stainless steel knife to cut the potato flesh tissue into small discs. During the measurement, take 30 cut small discs and place them in a 50mL centrifuge tube, pour in 20mL of distilled water to soak, stir evenly with a mixer and pour off the water, repeat the washing three times, and place them on absorbent paper to absorb the moisture on the surface of the slices. Place the slices in a 500mL beaker, add two-thirds of distilled water, and measure its initial conductivity r1 after standing at room temperature for 60 minutes. Then, boil the distilled water in the beaker for 10 minutes, and measure it again as r0 after cooling. Calculation of results:

[0120]

[0121] Where: R e is the relative conductivity; r1 is the conductivity of the extract of sweet potato living tissue; r0 is the conductivity of the extract after the sweet potato living tissue is killed.

[0122] The strength of the stress resistance of fruits and vegetables and the degree of damage can be expressed by the size of the conductivity. When fruits and vegetables continue to age with the extension of storage time or are affected by cold damage, diseases and other adverse effects, the cell membrane of the fruit and vegetable tissue will be damaged, and the electrolyte in the cell membrane will leak out, which will cause the conductivity of the extract to increase. Fig.16It can be seen that with the extension of storage time, the cell membrane permeability of each group of treatments showed a trend of gradual increase. At the 7th day of storage, the cell membrane permeability of each group of treatments increased significantly and there was no significant difference. This is because the damaged sweet potato root wounds are in the process of healing and the cell membrane permeability is high. After 14d to 35d of storage, except for Example 1, the cell membrane permeability of the remaining groups gradually increased. The cell membrane permeability of the untreated group in Comparative Example 1 increased the most, eventually reaching 0.849%, which was significantly higher than that of the other pretreated groups. The final cell membrane permeability of the sweet potato pretreated by cleaning in Comparative Example 3 was second only to that of Comparative Example 1, and was significantly higher than that of the sweet potato cell membrane permeability of Comparative Example 2 and Comparative Example 4, which shows that cleaning pretreatment may not be a good help for long-term storage of sweet potatoes. The cell membrane permeability of Example 1 decreased slightly on the 14th day and then increased. The final cell membrane permeability was the lowest among all pretreatment groups (0.72%), which shows that the equipment and pretreatment process of the present invention have a positive effect on increasing the cell membrane permeability of sweet potatoes during storage, which can enhance its healing effect and delay the aging process of sweet potatoes.

[0123] (f) Test 6: Malondialdehyde content test

[0124] Method for determining the content of malondialdehyde: weigh 1g of sweet potato sample, add 5mL of 100g / L trichloroacetic acid (TCA) solution, grind and homogenize, centrifuge (4℃, 10000r / min, 20min), collect the supernatant, and keep it at low temperature for later use. Take 2mL of supernatant, add 2mL of 0.67% thiobarbituric acid (TBA), mix and keep warm in a boiling water bath for 20min, cool and centrifuge once, and measure the absorbance at 450nm, 532nm and 600nm respectively. According to the absorbance value of the solution, first calculate the content of malondialdehyde in the reaction mixture, and then calculate the content of malondialdehyde in each gram of fresh weight of tissue sample, expressed in μmol / g FW.

[0125] C(μmol / L)=6.45×(OD532-OD600)–0.56×OD450

[0126] Wherein: OD532, OD600, OD450 represent the absorbance values ​​measured at 532nm, 600nm and 450nm respectively.

[0127]

[0128] Wherein: C is the concentration of malondialdehyde in the reaction mixture, μmol / L; V is the total volume of the sample extract, mL; Vs is the volume of the sample extract taken during the determination, mL; m is the sample mass, g.

[0129] When fruits and vegetables are subjected to adverse stresses such as aging, cold damage, and disease during storage, ROS free radicals produced in the tissues can induce peroxidation of unsaturated fatty acids in membrane lipids to generate malondialdehyde (MDA). Therefore, the level of MDA content can reflect the degree of damage to fruit and vegetable tissue cells due to aging, cold damage, and disease. Fig.17 It can be seen that during the storage of sweet potatoes, the MDA content of each group of treatments showed a trend of first rising, then falling, and then rising again. On the 7th day of storage, the MDA of all groups showed a small peak and then fell. This is because the sweet potato wounds in the early stage of storage produced a large amount of active oxygen in the healing process to promote wound healing. In the middle and late stages of storage, the MDA content gradually increased. When stored for 35 days, the untreated group of Comparative Example 1 had the highest MDA content (4.267 μmol / g), and the cleaning treatment group of Comparative Example 3 had the second highest MDA content and no significant difference from Comparative Example 1. The final MDA content of Comparative Example 2, Comparative Example 4 and Example 1 was lower than that of the above two groups, among which the 35d MDA content of Example 1 was the lowest (3.334 μmol / g). It shows that clear water pretreatment and no treatment have no obvious effect on the aging and adverse stress of sweet potatoes. Several callus pretreatment methods can effectively delay the accumulation of MDA content in sweet potato storage, reduce the peroxidation damage of sweet potatoes, and thus slow down the aging of sweet potatoes. Among them, the sweet potatoes treated by the equipment and pretreatment process of the present invention have the best effect.

[0130] (g) Test 7: Chilling damage test

[0131] Method for measuring chilling injury: During the storage period of sweet potatoes, the chilling injury incidence rate of sweet potatoes is counted and calculated according to the standards of the sweet potato chilling injury index grade table, as shown in the following table.

[0132] Table 1 Sweet potato chilling injury index grade table

[0133]

[0134]

[0135] The calculation formula of chilling damage rate is as follows:

[0136]

[0137] Chilling injury is an adverse phenomenon that occurs when the temperature of fruits and vegetables is lower than the specific cold sensitivity line during storage, affecting the final storage and edibility. It is reported that the chilling injury of sweet potatoes is mostly flocculent, waterlogged and rotten without microorganisms. Fig.18As shown, during the entire storage period, the chilling injury rate of each group of treatments showed a gradual upward trend as the storage time was extended. On the 7th day of storage, the chilling injury rate of sweet potatoes in each group was low, all below 0.12%. Starting from the 14th day, the chilling injury incidence of the cleaning pre-treated sweet potatoes in Comparative Example 3 increased significantly, and showed a sharp upward trend on the 21st day. This may be because the sweet potatoes were not dried by strong wind after the cleaning pre-treatment, and the surface humidity of the sweet potatoes was too high, resulting in a high water activity, which made the sweet potatoes more susceptible to chilling injury. The sweet potatoes in the untreated group of Comparative Example 1 increased significantly on the 21st day, and increased sharply on the 28th day, and the final chilling injury incidence was slightly lower than that of Comparative Example 3. The final chilling injury incidence of the sweet potatoes in the other three callus pre-treated groups was less than half of that in Comparative Examples 1 and 3, among which Example 1 had the best effect, with a final chilling injury incidence of 0.877%, significantly lower than the other four groups. This shows that the heat shock process of callus pre-treatment significantly improves the cold resistance of sweet potatoes and can improve the final storage quality of sweet potatoes.

[0138] (h) Test 8: Decay rate test

[0139] Method for determining the rot rate: During the storage period of sweet potatoes, the rot rate of sweet potatoes is counted and calculated according to the standards of the sweet potato rot index grade table, as shown in the following table.

[0140] Table 2 Sweet potato rot index grade table

[0141]

[0142] The decay rate is calculated as follows:

[0143]

[0144] The rot rate is an important indicator to measure the storage effect of sweet potatoes. Sweet potatoes have thin skin, high water content, and are easily scratched. During storage, the damaged parts are very susceptible to infection by pathogens, causing the sweet potatoes to rot. Fig.19 It can be seen that the rot rate of sweet potatoes during storage shows a trend of gradual increase. When stored for 7 days, the rot rate of each group is not higher than 0.2%, and there is no significant difference. After the 7th day, it began to rise gradually. Among them, the rising trend of the rot rate of comparative example 1 and comparative example 4 was significantly higher than that of the other three groups. On the 35th day, the rot rates of comparative example 1 and comparative example 4 were 4.9% and 2.76%, respectively. The final rot rate of the remaining three groups was lower than 1.2%, less than half of that of comparative example 4. Among them, Example 1 has the best effect on rot inhibition (0.54%), only a few sweet potatoes have dull skin and local mildew spots appear at the wound, which may be due to improper humidity control during storage, causing mold growth. The results of the rot rate show that the callus pretreatment has a certain effect on the rot rate, but the sweet potatoes that have not been cleaned and pretreated cannot control their rot rate well. The sweet potatoes pretreated by the device of the present invention have the best inhibitory effect on the rot rate.

[0145] (i) Test 9: Weight loss test

[0146] Method for determining weight loss rate: The weight loss rate of sweet potatoes was determined by weighing method. 30 sweet potato tubers were selected for each treatment and divided into three groups of 10 tubers in each group. The weight of the sweet potatoes was tracked and measured. The weight loss rate of each group of sweet potatoes was calculated according to the following formula, and then the average value was calculated.

[0147]

[0148] Transpiration is the main reason for the weight loss of fruits and vegetables. When fruits and vegetables are mechanically damaged or infected by diseases, the transpiration rate of water is accelerated and the weight of fruits and vegetables is reduced. The formation of callus tissue can effectively prevent water transpiration, reduce weight loss, and maintain good commercial quality. Fig. 20 It can be seen that the weight loss rate of sweet potatoes during the entire storage period generally shows a trend of gradual increase as the storage time is extended. The water loss phenomenon of sweet potatoes in the untreated group, Example 1, is the most serious from 14 days to 35 days, which is greater than that of the other four treatment groups, and the final weight loss rate reaches 17.82%. The cleaning pretreatment of Example 3 can keep the weight loss rate of sweet potatoes significantly lower than that of Example 1 before 21 days, but it rises sharply after 21 days, and the final weight loss rate is not much different from that of the comparative example, reaching 16.87%. Among the other three callus pretreatment groups, Example 1 and Comparative Example 4 can stabilize the final weight loss rate within 10%, and the effect of water loss is obviously controlled. It shows that the weight loss of sweet potatoes can be effectively reduced by the equipment and pretreatment of the present invention, so as to achieve the purpose of maximizing the reduction of product loss after storage.

[0149] (j) Test 10: Starch content test

[0150] Determination method of starch content: Determination of starch: It is determined by acid hydrolysis method and expressed in mass fraction (%).

[0151] Starch is the most common energy supply substrate for tuber crops in the postharvest process. Fig.21 It can be seen that due to the consumption of energy storage substances in the sweet potato during storage, the starch content in the sweet potato shows an overall downward trend, with a small rebound in the middle. During storage, the starch content of Example 1 decreases more slowly as a whole, and the peak of a small rebound occurs on the 21st day. Comparative Example 4 was also treated with the equipment of the present invention, and the change trend was the same as that of Example 1. The starch content of the sweet potatoes in the untreated group of Comparative Example 1 decreased most seriously, and decreased by 75% compared with the initial origin. The experimental results show that the sweet potatoes treated with the equipment of the present invention and pretreatment can retain more starch content during storage, thereby obtaining sweet potatoes with better edible and sales quality.

[0152] (k) Test 11: Soluble sugar content test

[0153] The soluble sugar content was determined by phenol-sulfuric acid method and expressed as mass fraction (%).

[0154] Soluble sugar is an important energy storage substance in fruit and vegetable tissues. Its content is closely related to the quality and storage of fruits and vegetables. Sweet potatoes with high sweetness are more likely to be favored by consumers. Fig. 22 As shown, the soluble sugar content of sweet potatoes shows a trend of gradual increase with the extension of storage time, which is opposite to the change trend of starch. The soluble sugar content of sweet potatoes in Example 1 has the fastest rising rate in the initial stage, because the sweet potatoes consume energy for rapid wound healing after being pretreated by the equipment of the present invention. After 35 days of storage, the soluble sugar content of sweet potatoes in Example 1 and Comparative Example 2 reached 7.73% and 7.67%, which are the highest among all pretreated groups. The final soluble sugar content of the sweet potatoes in Comparative Example 1 is only 6.54%. Combining the results of starch content and soluble sugar content, it is found that if no treatment is performed on Comparative Example 1, it may lead to greater metabolic consumption of sweet potatoes during storage, thereby causing the loss of starch and sugar, affecting sales quality. This result shows that the equipment and pretreatment of the present invention can effectively reduce the metabolic consumption of sweet potatoes during storage, better maintain the edible quality of sweet potatoes, and are of great significance to actual production.

[0155] (l) Test 12: Ascorbic acid content test

[0156] Determination method of ascorbic acid: Determined by spectrophotometer, expressed as the mass of ascorbic acid contained in 100g fresh weight of sample, i.e. mg / 100g.

[0157] Ascorbic acid content is one of the important indicators for evaluating the nutritional quality and storage effect of fruits and vegetables. As the freshness of fruits and vegetables decreases, the ascorbic acid content also decreases. Therefore, the ascorbic acid content reflects the quality effect of fruits and vegetables during storage. Fig.23 The experimental results shown show that the ascorbic acid content of the sweet potato in Example 1 has the least downward trend, and the ascorbic acid content at 35 days is significantly higher than that of other groups, and is reduced by 44.6% compared with the initial level. The decrease in Comparative Example 1 is the most significant, and it finally decreases by 83.8% compared with the initial level. The other three pretreatment groups are respectively between Example 1 and Comparative Example 1, which shows that although other pretreatment methods can effectively retain the ascorbic acid content of sweet potatoes after storage and ensure the quality after storage; however, the effect of pretreatment by the equipment and process of the present invention is more prominent.

[0158] It can be seen from the above embodiments that the sweet potato storage pretreatment equipment and pretreatment method provided by the present invention, wherein the sweet potato storage pretreatment equipment performs high-temperature short-time callus treatment on the sweet potato through the callus chamber 1, uses heat shock to regulate metabolic pathways and high-temperature to kill epidermal microorganisms, so that the injured periderm of the sweet potato is quickly healed, forming a biological barrier against external disease microorganisms, and then the sweet potato after callus is quickly cooled by strong wind through the cooling chamber 2, so as to quickly reduce the residual temperature of the sweet potato after callus, avoid the increase and loss of respiratory intensity during storage, and reduce the rot in the early stage of storage. The sweet potato storage pretreatment equipment can effectively accelerate the formation of sweet potato root callus tissue and shorten the pretreatment time by performing high-temperature short-time callus-cooling pretreatment on the sweet potato before postpartum storage with a green and pollution-free physical method, thereby achieving the purpose of reducing sweet potato storage period rot and water loss, ensuring storage quality, and extending the storage period.

[0159] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A sweet potato storage pretreatment device, characterized in that: It comprises a healing chamber and a cooling chamber with inlet and outlet doors arranged opposite to each other, the end of the healing chamber away from the cooling chamber is connected to a first air supply fan, a heating device is installed between the outlet of the first air supply fan and the healing chamber; the end of the cooling chamber away from the healing chamber is connected to a second air supply fan; A return air duct is provided above the healing chamber, the inlet of the return air duct is connected to the inner chamber of the healing chamber, and the outlet of the return air duct is connected to the inlet of the first air supply fan; a lower air supply duct is provided below the healing chamber, the inlet of the lower air supply duct is connected to the outlet of the heating device, and the outlet of the lower air supply duct is connected to the inner chamber of the healing chamber; A plurality of openable top windows are installed on the top of the healing room in the length direction, and the inlet of the return air duct is connected to the inner chamber of the healing room through the top windows; The outlet of the heating device is connected to the inlet of the lower air supply duct and the air inlet of the healing chamber through a three-way regulating valve.

2. The sweet potato storage pretreatment equipment according to claim 1, characterized in that: The invention also comprises a cleaning chamber arranged between the healing chamber and the cooling chamber, wherein a plurality of spray heads are installed in the cleaning chamber.

3. The sweet potato storage pretreatment equipment according to claim 1, characterized in that: The healing room is equipped with a temperature sensor and a humidity sensor, and is also equipped with an electric air inlet valve and a moisture exhaust fan electrically connected to the humidity sensor.

4. The sweet potato storage pretreatment equipment according to claim 1, characterized in that: A wet curtain is installed between the outlet of the second air supply fan and the cooling chamber.

5. The sweet potato storage pretreatment equipment according to any one of claims 1 to 4, characterized in that: It also includes a slide rail and a loading trolley, one end of the slide rail extends into the healing chamber, and the other end of the slide rail extends into the cooling chamber; the loading trolley can slide along the slide rail.

6. A pretreatment method using the sweet potato storage pretreatment equipment according to any one of claims 1 to 5, characterized in that: include: Wash the sweet potatoes after being put into the basket; The cleaned sweet potato basket containing sweet potatoes is sent into a callus room, wherein the temperature in the callus room is 60° C. to 65° C., the relative humidity is 20% to 30%, and the wind speed is at least 0.5 m / s, and the callus treatment is performed for 20 min to 40 min; The sweet potatoes after callus treatment are moved into a cooling room, wherein the temperature of the cooling room is 15° C. to 20° C., the relative humidity is 20% to 30%, and the wind speed is at least 0.5 m / s, for cooling treatment; After the temperature of the sweet potatoes drops below 18° C., the sweet potatoes are taken out for storage.

7. The pretreatment method according to claim 6, characterized in that: Before the sweet potatoes after being put into the baskets are cleaned, the method further comprises: Clean the harvested fresh sweet potatoes, remove the dirt and impurities on the surface, and remove the sweet potatoes with diseases and insect pests; The selected sweet potatoes are placed in sweet potato baskets respectively, and the height of the sweet potato baskets is less than or equal to two-thirds of the height of the sweet potato baskets.

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