Pretreatment method for improving unfreezing quality of vegetables
By performing cold air dehydration and drying of fruits and vegetables and low temperature uniform humidity treatment pretreatment methods, the problems of cell damage and quality deterioration after thawing during the freezing process are solved, and higher thawing quality and lower production costs are achieved.
Patent Information
- Application Number
- CN202411260412.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-10
- Publication Date
- 2025-02-11
AI Technical Summary
During the freezing process, fruit and vegetable cells are damaged due to the formation of ice crystals, resulting in deterioration of quality after thawing. Especially the loss of drip drip and the reduction of hardness when thawing after freezing, affecting the quality of the thawed product.
A pretreatment method is adopted, which involves dehydrating and drying the vegetables in cold air and then uniformly wetted at low temperatures, allowing the moisture to re-diffusion and distribution within the product to form a suitable ice crystal structure to reduce cell damage.
Through this pretreatment method, the water loss of vegetables during freezing and thawing is significantly reduced, the hardness and crispness are maintained, the quality of thawed vegetables is improved, and the production cost is reduced.
Smart Images
Figure CN119404897A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of fruit and vegetable food storage and processing, and particularly relates to a pretreatment method for improving vegetable thawing quality. Background Art
[0002] Most fruits and vegetables are highly perishable and have a short shelf life. Freezing is a standard method for preserving perishable agricultural products such as fruits and vegetables, and it can increase the supply during the off-season. However, during the freezing process, the water in the cells of the plant tissues of fruits and vegetables increases in volume due to the formation of ice. After thawing, the quality of fruits and vegetables deteriorates due to cell damage and texture loss. There are many factors that affect the degree of freeze damage to fruits and vegetables, and one of the key factors is the freezing rate. Freezing methods are divided into very slow freezing (<0.1cm / h), slow freezing (0.1-0.5cm / h), normal freezing (0.5-1cm / h), rapid freezing (1-10cm / h) and ultra-fast freezing (>10cm / h) according to their freezing rate. The freezing rate affects the changes in the state of water in the cell structure. In plant cells, water exists in the form of vacuolar, cytosolic or extracellular water. Vacuolar water is essential for maintaining cell turgor pressure and the firmness and crispness of the product. The water in the cytoplasm interacts with proteins and solutes in the cytoskeleton to maintain membrane integrity. Slow freezing usually starts from the extracellular space, where ice formation reduces the amount of liquid water and increases the concentration of extracellular solutes. This process leads to the formation of large extracellular ice crystals, cell dehydration, and deformation. In addition, cell shrinkage leads to loss of membrane integrity and ultimately cell collapse. During rapid freezing, smaller and more evenly distributed intracellular and extracellular ice crystals are formed. Faster heat dissipation leads to less cell shrinkage and deformation. However, ultra-fast freezing at ultra-low temperatures can lead to freeze fracture or cell membrane puncture due to the rapid expansion of water.
[0003] Other factors that affect freezing damage are the physical properties of plant tissues, such as the porosity of intercellular spaces and cell size. Cell size is generally related to tissue porosity, and small cells are usually more tightly packed than large cells embedded in large intercellular spaces. Large void spaces can cause internal stresses because they affect heat and mass transfer during freezing. In addition, these air gaps may favor the formation of extracellular ice. In addition, the cell wall composition and hardness of different cell types can affect the freezing characteristics of different products. Currently, some efforts have been reported to develop new pretreatment and freezing methods to reduce cell damage during freezing, so as to obtain a texture as close to fresh products as possible after thawing, such as pressure-assisted freezing, ultrasound-assisted freezing, etc. However, these new technologies are often accompanied by higher energy costs, environmental impacts, or additional infrastructure investment. Summary of the invention
[0004] In order to solve the technical problem in the prior art that freezing plant tissues with high water content will cause cell damage by forming ice crystals, and such damage will cause drip loss and reduced hardness, thereby reducing the quality of thawed products, the present invention mainly provides a pretreatment method for improving the thawing quality of vegetables, and a method for treating vegetables using the pretreatment method, and the specific scheme is as follows:
[0005] A pretreatment method for improving the thawing quality of vegetables comprises the following steps:
[0006] a. Dehydrate and dry the vegetables in cold air to obtain dried vegetables;
[0007] b. Immediately treat the dried vegetables at low temperature to make the water diffuse and distribute again inside the product; thus obtaining the pretreated vegetables.
[0008] Furthermore, the vegetable is tuberose cauliflower.
[0009] Furthermore, the dehydration and drying in step a is carried out at a temperature of 0.5 to 5° C., a relative humidity of 70 to 85%, and a time of 3 to 6 hours.
[0010] Furthermore, the low temperature in step b is 0-3°C; and the humidity equalization treatment is balanced at a relative humidity of 60-80% for 7-12 hours.
[0011] A method for processing vegetables using the above-mentioned pretreatment method for improving the thawing quality of vegetables comprises the following steps: freezing the pretreated vegetables and then storing them in frozen form; thawing the frozen vegetables in running water to obtain thawed vegetables.
[0012] Furthermore, the pretreated vegetables are frozen at -30 to -35°C, and after the center temperature of the frozen products is below -18°C, they are frozen at -22 to -18°C; the equivalent diameter of the ice crystals in the frozen vegetables is 40 to 55 μm.
[0013] Furthermore, the frozen vegetables are thawed in running water at 14-20° C. to obtain thawed vegetables.
[0014] A pretreatment device for improving the thawing quality of vegetables, comprising a shell, a partition arranged in the inner cavity of the shell and dividing the inner cavity into a humidity equalization bin and a dehydration bin; the partition is provided with a first vent that passes through the humidity equalization bin and the dehydration bin; the humidity equalization bin is provided with a cold air blower connected to an external constant humidity cold air source; a vegetable drying board is obliquely provided in the dehydration bin; a plurality of through holes are evenly distributed on the vegetable drying board; a fan for supplying air to the vegetable drying board is provided at a side of the vegetable drying board away from the first vent and in the humidity equalization bin; the front side of the shell is opened to form a door opening, and a door body is provided at the position of the door opening to seal the door opening when closed.
[0015] Furthermore, a second vent is provided outside the first vent; a sealing plate is rotatably provided inside the partition to control the connection or closing of the first vent and the second vent; a rotating groove for the sealing plate to rotate is provided inside the partition at the sealing plate position; a plurality of horizontally arranged anti-slip plates are evenly distributed on the surface of one side of the vegetable drying board close to the first vent;
[0016] A temperature sensor and a humidity sensor are arranged in the dehydration bin.
[0017] Furthermore, a grid is provided on the outside of the shell at the position of the humidity equalization bin; a refrigeration device and a humidity control device which can generate an external constant humidity cold air source and are connected to the air cooler are provided in the space formed by the grid and the shell.
[0018] By adopting the above scheme, the method of the present invention has the following advantages:
[0019] 1. The present invention adopts convection dehydration technology to pre-treat fruits and vegetables through mild dehydration, thereby reducing the extracellular ice volume before slow freezing and improving the texture quality of thawed products. It is economical, practical and suitable for industrial production.
[0020] 2. The drip loss of the frozen vegetable thawed samples treated by the method of the present invention is significantly reduced. The reduction in drip loss means that the water retention capacity of the night-scented cauliflower is enhanced during the freezing and thawing process, which not only reduces the loss of nutrients with water, but also makes the thawed night-scented cauliflower closer to the fresh state in taste and appearance.
[0021] 3. The pretreatment method of the present invention retains more total number of surviving cells in the dehydrated and frozen sample. More surviving cells help maintain the physiological activity and metabolic function of the tuberose, thereby extending its fresh-keeping period and shelf life.
[0022] 4. The present invention reduces the freezing expansion of night-scented cauliflower, which has a positive effect on its texture. The improved texture means that the night-scented cauliflower tastes more crisp and tender, increasing the consumer's eating satisfaction. Therefore, compared with the traditional freezing method, pre-treatment and freezing, reducing drip loss and retaining higher hardness effectively improve the thawing quality of night-scented cauliflower.
[0023] 5. Compared with traditional freezing, the pretreatment of the equipment of the present invention does not increase energy consumption, which can significantly reduce production costs in large-scale production and improve the economic benefits and market competitiveness of enterprises.
[0024] 6. The pretreatment equipment of the present invention can ensure that the cold air is quickly subjected to moisture uniformity treatment after dehydration and drying, thereby avoiding the drastic temperature change when switching equipment that affects the effect of the pretreatment, and also avoiding the energy consumption of precooling and pre-starting when multiple equipment are used in conjunction.
[0025] 7. When the equipment of the present invention is used for pretreatment, cold air convection can be achieved between the first through-hole and the second through-hole under the action of the fan, so that the cold air is dried more fully and evenly, thereby improving the pretreatment effect and efficiency. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Figure 1 It is a structural schematic diagram of an embodiment of the device.
[0027] Figure 2 AA' is a cross-sectional view of an embodiment of the device.
[0028] Figure 3 This is a photo of the tuberose after thawing in Example 1.
[0029] In the figure: 1-shell; 11-grid; 12-door; 13-partition; 2-humidity equalization chamber; 21-refrigeration equipment; 22-air cooler; 23-first air vent; 24-second air vent; 25-rotating groove; 26-sealing plate; 3-dehydration chamber; 31-vegetable drying board; 32-anti-skid plate; 33-through hole; 34-fan. DETAILED DESCRIPTION
[0030] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. 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.
[0031] Device Embodiment
[0032] like Figure 1 , Figure 2 As shown, the present embodiment provides a pretreatment device for improving the thawing quality of vegetables, comprising a shell 1, a partition 13 arranged in the inner cavity of the shell 1 and dividing the inner cavity into a humidity equalization bin 2 and a dehydration bin 3; a first air vent 23 penetrating the humidity equalization bin 2 and the dehydration bin 3 is provided on the partition 13; the humidity equalization bin 2 is provided with a cold air fan 22 connected to an external constant humidity cold air source; a vegetable drying board 31 is obliquely provided in the dehydration bin 3; a plurality of through holes 33 are evenly distributed on the vegetable drying board 31; a fan 34 for supplying air to the vegetable drying board 31 is provided in the humidity equalization bin 2 at a side of the vegetable drying board 31 away from the first air vent 23; the front side of the shell 1 is opened to form a door opening, and a door body 12 is provided at the door opening position to seal the door opening when closed.
[0033] Preferably, a second air vent 24 is provided on the outer side of the first air vent 23; a sealing plate 26 is rotatably provided inside the partition 13 for controlling the passage or closing of the first air vent 23 and the second air vent 24; a rotating groove 25 for the sealing plate 26 to rotate is provided inside the partition 13 at the position of the sealing plate 26; a plurality of horizontally arranged anti-slip plates 32 are evenly distributed on the surface of one side of the vegetable drying board 31 close to the first air vent 23; a temperature sensor and a humidity sensor are provided in the dehydration bin 3.
[0034] Preferably, a grid 11 is provided on the outside of the shell 1 at the position of the humidity equalization bin 2; a refrigeration device 21 and a humidity control device which can generate an external constant humidity cold air source and are connected to a cold air blower 22 are provided in the space formed by the grid 11 and the shell 1.
[0035] Based on the above structure, the pretreatment equipment for improving the thawing quality of vegetables of the present invention, when performing pretreatment, starts the refrigeration equipment 21 and the humidity control equipment, and the sealing plate 26 rotates to fully open the first vent 23 and the second vent 24. When the temperature and humidity in the dehydration bin 3 reach the temperature and humidity required for cold dehydration and drying, the flower buds of the night-scented flower are spread on the vegetable drying board 31 in the dehydration bin 3, and the fan 34 blows the night-scented flower on the vegetable drying board 31. The cold air in the bin convects with the gas in the upper humidity bin 2 under the action of the first vent 23 and the second vent 24, takes away the moisture of the night-scented flower and maintains the balance of temperature and humidity. When the fan blows, the night-scented flower is stabilized on the vegetable drying board 31 under the action of the anti-slip plate 32. After the drying is completed, the sealing plate 26 closes the first vent 23 and the second vent 24, and the night-scented flower is transferred to the humidity bin on the partition 13. After the humidity treatment is completed, the pretreatment is completed.
[0036] Embodiment 1:
[0037] a. Dehydrate and dry the night-scented flower buds in cold air at 1°C and a relative humidity of 75% for 5 hours to obtain dried night-scented flowers;
[0038] b. The dried night-scented flowers were immediately equilibrated at 0°C and 70% relative humidity for 10 hours to allow the water to diffuse and distribute again within the product to complete the wet treatment; the pretreated night-scented flowers were obtained;
[0039] c. Freeze the pretreated night-scented flowers at -30 to -35°C until the center temperature of the frozen product is below -18°C, and then store at -22 to -18°C;
[0040] d. Thawing the frozen tuberose in running water at 15°C to obtain thawed tuberose.
[0041] Each embodiment and comparative example is based on the steps of embodiment 1, adopts the equipment embodiment, and performs treatment with reference to the treatment conditions of Table 1.
[0042] Table 1:
[0043]
[0044]
[0045] Determination of drip loss rate:
[0046] Under the premise of ensuring the surface cleanliness, the samples of night-scented cauliflower of each embodiment and comparative example are weighed in an environment of 15-25°C. Then, the samples are placed in a waterproof bag and sealed, and quickly placed in a circulating water bath thawing device at 15-25°C to be fixed, and water is added to make the liquid level higher than the sample. At the same time, it is ensured that the sealing part of the waterproof bag is higher than the water surface, and no water can seep in the whole process, and the thawing cycle is carried out. When the central temperature of the sample is between -2°C and 3°C, the sample is taken out, and the waterproof bag and the outer packaging bag are removed under the same conditions of 15-25°C. The sample is spread in a single layer on a drain tray, covered with a plastic film to prevent surface water loss, and drained until the mass difference between two consecutive weighings does not exceed 0.2% of the sample mass. The drip loss rate of the sample is calculated according to the formula W=(m-m0) / m×100. Where: W—drip loss rate in the sample, %; m—total mass of the sample and packaging before thawing; m0—total mass of the sample and packaging after thawing.
[0047] Texture (hardness) determination:
[0048] The hardness of the night-scented cauliflower of each embodiment and comparative example was measured using the HDP / VB mold of the texture analyzer, wherein the descent speed of the probe was set to 2.0 mm / s and the strain force was 80%. Within a specific range, the greater the hardness, the better the crispness of the night-scented cauliflower. The flower buds of the night-scented cauliflower were selected for measurement, and 8 parallel measurements were performed, and the final result was taken as the average value. The texture improvement rate of the sample was calculated according to the formula T1=(Y-Y1) / Y1×100.
[0049] Wherein: T1 is the texture improvement rate of the sample, %; Y is the hardness of the sample after thawing, g; Y1 is the hardness of the tuberose sample after thawing of Comparative Example 1, g.
[0050] The texture retention rate of the sample is calculated according to the formula T2=(Y0-Y) / Y0×100.
[0051] Where: T2——texture retention rate of the sample, %; Y—hardness of the sample after thawing, g; Y0—hardness of the fresh tuberose sample, g.
[0052] Equivalent diameter determination:
[0053] The sample holders of the night-scented cauliflower of each embodiment and comparative example were fixed on the workbench of the freezing microtome, and the samples were sliced into 7-9 μm thick slices and attached to a glass slide. The images were collected by a digital slice scanner. The microscope images of the ice crystal state were observed using Caseview software, and three different areas were randomly selected from the same image with the help of Image pro plus software for calculation. According to Di=2(A i / π) 0.5 The formula is used for calculation. Where: Di is the equivalent diameter, μm; Ai is the cross-sectional area, μm 2 The test results are shown in Table 2.
[0054] Table 2:
[0055]
[0056]
[0057] It can be seen from Table 2 that compared with the high-energy-consuming traditional freezing of Comparative Examples 1 to 3, the pretreatment method and treatment equipment of the present invention can significantly reduce the ice crystal equivalent diameter of the night-scented cauliflower product when it is frozen, with less cell damage, higher tissue cell survival rate, and an average hardness increase of 40 to 55% during thawing, and a droplet loss rate reduction of 15 to 19%. Figure 3 It can be seen that the thawed tuberose of the present invention is closer to the fresh state in taste and appearance. The method and device of the present invention provide technical support for the quick freezing processing of tuberose.
[0058] For those skilled in the art, various other corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all of these changes and deformations should fall within the protection scope of the claims of the present invention.
Claims
1. A pretreatment method for improving the thawing quality of vegetables, characterized in that: The following steps are involved: a. Dehydrate and dry the vegetables in cold air to obtain dried vegetables; b. Immediately treat the dried vegetables at low temperature to make the water diffuse and distribute again inside the product; thus obtaining the pretreated vegetables.
2. The pretreatment method for improving the thawing quality of vegetables according to claim 1, characterized in that: The vegetable is tuberose cauliflower.
3. The pretreatment method for improving the thawing quality of vegetables according to claim 1, characterized in that: The dehydration and drying in step a is carried out at a temperature of 0.5 to 5° C., a relative humidity of 70 to 85%, and a time of 3 to 6 hours.
4. The pretreatment method for improving the thawing quality of vegetables according to claim 1, characterized in that: The low temperature in step b is 0-3°C; the humidity equalization treatment is to balance at a relative humidity of 60-80% for 7-12 hours.
5. A method for treating vegetables using the pretreatment method for improving the thawing quality of vegetables according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: freezing the pretreated vegetables and then storing them in frozen form; thawing the frozen vegetables in running water to obtain thawed vegetables.
6. The method for treating vegetables according to the pretreatment method for improving the thawing quality of vegetables according to claim 5, characterized in that: The pretreated vegetables are frozen at -30 to -35°C, and after the center temperature of the frozen products is below -18°C, they are frozen at -22 to -18°C; the equivalent diameter of ice crystals in the frozen vegetables is 40 to 55 μm.
7. The pretreatment method for improving the thawing quality of vegetables according to claim 5, characterized in that: The frozen vegetables are thawed in running water at 14-20°C to obtain thawed vegetables.
8. A pretreatment device for improving the thawing quality of vegetables, characterized in that: The invention comprises a shell (1), a partition (13) arranged in the inner cavity of the shell (1) and dividing the inner cavity into a humidity equalizing chamber (2) and a dehydration chamber (3); the partition (13) is provided with a first vent (23) penetrating the humidity equalizing chamber (2) and the dehydration chamber (3); the humidity equalizing chamber (2) is provided with a cold air fan (22) connected to an external constant humidity cold air source; a vegetable drying board (31) is obliquely arranged in the dehydration chamber (3); a plurality of through holes (33) are evenly distributed on the vegetable drying board (31); a fan (34) for supplying air to the vegetable drying board (31) is provided in the humidity equalizing chamber (2) at a side of the vegetable drying board (31) away from the first vent (23); the front side of the shell (1) is open to form a door opening, and a door body (12) is provided at the position of the door opening to seal the door opening when closed.
9. The pretreatment equipment for improving the thawing quality of vegetables according to claim 8, characterized in that: A second ventilation hole (24) is arranged outside the first ventilation opening (23); a sealing plate (26) is rotatably arranged inside the partition (13) for controlling the first ventilation hole (23) and the second ventilation hole (24) to be connected or closed; a rotating groove (25) for rotating the sealing plate (26) is arranged inside the partition (13) at the position of the sealing plate (26); a plurality of horizontally arranged anti-slip plates (32) are evenly distributed on a surface of one side of the vegetable drying board (31) close to the first ventilation opening (23); and a temperature sensor and a humidity sensor are arranged inside the dehydration bin (3).
10. The pretreatment equipment for improving the thawing quality of vegetables according to claim 8, characterized in that: A grid (11) is provided on the outside of the shell (1) at the position of the humidity equalization bin (2); a refrigeration device (21) and a humidity control device that can generate an external cold air source and is connected to the cold air blower (22) are provided in the space formed by the grid (11) and the shell (1).