Magnetic field assisted fruit and vegetable freezing method

Abstract

The invention provides a magnetic field assisted fruit and vegetable freezing method which can be applied to the technical field of food processing and storage. The magnetic field assisted fruit and vegetable freezing method comprises the following steps: performing cooling treatment on fruits and vegetables according to a preset duration to obtain fruits and vegetables to be frozen; working parameters are determined based on the mapping relation between the fruits and vegetables to be frozen and the working parameters, the working parameters comprise magnetic field intensity and magnetic field frequency, the magnetic field intensity is larger than or equal to 2 mT, and the magnetic field frequency is larger than or equal to 50 Hz; after the magnetic field environment in the freezing process is adjusted according to the working parameters, the to-be-frozen fruits and vegetables are placed in the magnetic field environment to be frozen, target fruits and vegetables are obtained under the condition that the to-be-frozen fruits and vegetables meet preset conditions, and the target fruits and vegetables are transferred to the target environment.

Description

Technical Field

[0001] The present invention relates to the technical field of food processing and storage, and in particular to a method for magnetic field-assisted freezing of fruits and vegetables. Background Art

[0002] Freezing is a physical method for long-term preservation of food. In the frozen state, chemical reactions, microbial activities and cell metabolic reactions in food are greatly restricted, making food less likely to spoil. However, freezing has been shown to have some adverse effects on food quality, including mechanical damage, freeze concentration, freezer burn, recrystallization, etc. In order to minimize the deterioration of food quality caused by freezing, some new physical field technologies are used to assist in food freezing, but the freezing effect of the physical field freezing technology currently used is not good, and the quality of frozen food needs to be improved. Summary of the invention

[0003] In view of the above problems, the present disclosure provides a method for magnetic field-assisted freezing of fruits and vegetables to improve the freezing effect.

[0004] According to a first aspect of the present disclosure, a method for magnetic field-assisted freezing of fruits and vegetables is provided, comprising: cooling fruits and vegetables for a predetermined time to obtain fruits and vegetables to be frozen; determining working parameters based on a mapping relationship between the fruits and vegetables to be frozen and working parameters, wherein the working parameters include magnetic field intensity and magnetic field frequency, and the magnetic field intensity is ≥2mT and the magnetic field frequency is ≥50Hz; after adjusting the magnetic field environment during the freezing process according to the working parameters, the fruits and vegetables to be frozen are placed in the magnetic field environment for freezing, and when the fruits and vegetables to be frozen meet preset conditions, target fruits and vegetables are obtained, and the target fruits and vegetables are transferred to the target environment.

[0005] According to an embodiment of the present disclosure, determining the working parameters based on the mapping relationship between the fruits and vegetables to be frozen and the working parameters includes: determining the types of fruits and vegetables to be frozen; and determining the working parameters according to the mapping relationship between the types of fruits and vegetables to be frozen and the working parameters.

[0006] According to an embodiment of the present disclosure, the magnetic field strength includes 2~6mT, and the magnetic field frequency includes 50~90Hz.

[0007] According to an embodiment of the present disclosure, the working parameters also include wind speed, wherein the wind speed is ≤1.5 m / s.

[0008] According to an embodiment of the present disclosure, placing the fruits and vegetables to be frozen in a magnetic field environment for freezing includes: placing the fruits and vegetables to be frozen in a uniform magnetic field for freezing.

[0009] According to an embodiment of the present disclosure, the magnetic field environment includes a one-dimensional alternating magnetic field.

[0010] According to an embodiment of the present disclosure, cooling fruits and vegetables for a predetermined time to obtain fruits and vegetables to be frozen includes: cooling fruits and vegetables for a predetermined time to reduce the respiration intensity of fruits and vegetables to obtain fruits and vegetables to be frozen, wherein the predetermined time is ≥ 10 hours.

[0011] According to an embodiment of the present disclosure, fruits and vegetables are cooled for a predetermined time to obtain fruits and vegetables to be frozen, including: after cooling the fruits and vegetables for a predetermined time, the core temperature of the fruits and vegetables is measured, and in response to the core temperature satisfying a threshold range, the fruits and vegetables to be frozen are obtained, wherein the core temperature includes 6~10℃.

[0012] According to an embodiment of the present disclosure, when the fruits and vegetables to be frozen meet preset conditions, target fruits and vegetables are obtained and transferred to a target environment, including: measuring the central temperature of the fruits and vegetables to be frozen, and in response to the central temperature of the fruits and vegetables to be frozen being less than -18°C, obtaining the target fruits and vegetables and transferring the target fruits and vegetables to the target environment.

[0013] A second aspect of the present disclosure provides fruits and vegetables frozen with the assistance of a magnetic field, including: the time for the fruits and vegetables to pass through the maximum ice crystal formation zone is less than 20 minutes.

[0014] According to the embodiments of the present disclosure, after cooling the fruits and vegetables, fruits and vegetables to be frozen are obtained. Based on the mapping relationship between the fruits and vegetables to be frozen and the working parameters, the parameter values ​​of the magnetic field strength and the magnetic field frequency are determined, wherein the magnetic field strength is ≥ 2mT and the magnetic field frequency is ≥ 50Hz, so as to determine the magnetic field environment in which the fruits and vegetables to be frozen are frozen, and then the fruits and vegetables to be frozen are placed in the above-mentioned magnetic field environment for freezing. By reasonably setting the working parameters of the fruits and vegetables in the magnetic field freezing process, the freezing process is accelerated, the freezing effect is improved, and the quality of the frozen fruits and vegetables is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above contents and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0016] Figure 1 A schematic diagram of a device for a method for magnetic field-assisted freezing of fruits and vegetables according to an embodiment of the present disclosure is schematically shown;

[0017] Figure 2 A flow chart of a method for magnetic field-assisted freezing of fruits and vegetables according to an embodiment of the present disclosure is schematically shown;

[0018] Figure 3A Schematically showing the microstructure result of common frozen bamboo shoots according to an embodiment of the present disclosure;

[0019] Figure 3B Schematically showing the microstructure result of magnetic field-assisted freezing of bamboo shoots according to an embodiment of the present disclosure;

[0020] Figure 4 The freezing curve diagram under different working parameters according to the embodiment of the present disclosure is schematically shown;

[0021] Figure 5 A bar graph schematically shows the weight loss variation of bamboo shoots under different working parameters according to an embodiment of the present disclosure;

[0022] Figure 6 A bar chart schematically shows pH variation of bamboo shoots under different working parameters according to an embodiment of the present disclosure;

[0023] Figure 7 A bar graph schematically shows changes in shading of bamboo shoots under different working parameters according to an embodiment of the present disclosure;

[0024] Figure 8 A bar graph schematically shows the sugar content change of bamboo shoots under different working parameters according to an embodiment of the present disclosure;

[0025] Fig.9A Schematically shows a low-resolution nuclear magnetic resonance spectrum result diagram of a sample when the magnetic field strength is 2 mT according to an embodiment of the present disclosure;

[0026] Fig. 9B Schematically shows a low-resolution nuclear magnetic resonance spectrum result diagram of a sample when the magnetic field strength is 4 mT according to an embodiment of the present disclosure;

[0027] Fig. 9C The figure schematically shows the result of low-resolution nuclear magnetic resonance spectrum of the sample when the magnetic field strength is 6 mT according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0028] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0029] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0030] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0031] When using expressions such as "at least one of A, B, and C, etc.", they should generally be interpreted according to the meaning of the expression commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0032] Fruits and vegetables are one of the types of food needed in daily life. They can provide the human body with abundant water, carbohydrates, proteins, vitamins and minerals, and play an important role in maintaining normal physiological functions of the human body. The intake of fruits and vegetables is also one of the important indicators for measuring human nutritional health. In recent years, the annual output of fruits and vegetables is about 1 billion tons, but the comprehensive cold chain circulation rate is low and the spoilage rate is high, resulting in a huge waste of social resources.

[0033] Freezing is a physical method for long-term food preservation, which can better preserve the appearance, taste and nutritional value of food than other methods. In the frozen state, chemical reactions, microbial activities and cell metabolic reactions in food are greatly restricted, making food less likely to spoil. However, freezing has been shown to have some adverse effects on food quality, including mechanical damage, freeze concentration, freezer burn, recrystallization, etc., which limits the widespread application of this technology in food preservation.

[0034] In order to minimize the degradation of food quality caused by freezing, some new physical field technologies, such as ultrasound, microwaves and electromagnetic fields, are being used to assist in food freezing. Among them, magnetic fields have attracted more attention due to their ability to maintain high quality, and therefore show potential in reducing freezing damage to food. However, the freezing effect of the magnetic field freezing technology currently used is not good, and the quality of frozen food needs to be improved. In addition, the magnetic field intensity is relatively high, and the Joule heat generated is relatively large, which has an adverse effect on the freezing process of food.

[0035] In view of this, an embodiment of the present invention provides a method for magnetic field-assisted freezing of fruits and vegetables, wherein the fruits and vegetables are subjected to a cooling treatment to obtain the fruits and vegetables to be frozen, and the parameter values ​​of the magnetic field strength and the magnetic field frequency are determined based on the mapping relationship between the fruits and vegetables to be frozen and the working parameters, wherein the magnetic field strength is ≥ 2mT and the magnetic field frequency is ≥ 50Hz, so as to determine the magnetic field environment in which the fruits and vegetables to be frozen are frozen, and then the fruits and vegetables to be frozen are placed in the above magnetic field environment for freezing. By reasonably setting the working parameters of the fruits and vegetables during the magnetic field freezing process, the freezing effect of the fruits and vegetables is improved, and the quality of the frozen fruits and vegetables is improved.

[0036] The method for magnetic field-assisted freezing of fruits and vegetables in the disclosed embodiment can be implemented by a magnetic field-assisted freezing device, which can be an air-cooled magnetic field freezing device, specifically, a forced air blowing magnetic field freezing device, which is used to provide a stable magnetic field and a stable temperature.

[0037] Figure 1 The following is a schematic diagram of a device for a method for magnetic field-assisted freezing of fruits and vegetables according to an embodiment of the present disclosure.

[0038] like Figure 1 As shown, the magnetic field assisted freezing device 100 includes a thermocouple 101, a magnetic field coil 102, a fan 103, an AC power supply 104, a temperature controller 105, a data collector 106 and a Gauss meter 107. The thermocouple 101 is mainly used to monitor the temperature changes of fruits and vegetables during the freezing process, so as to understand the temperature information of fruits and vegetables in real time. The magnetic field coil 102 is a key component for generating a magnetic field. When a current passes through the magnetic field coil, a magnetic field will be generated around it. The Gauss meter 107 is used to measure the strength of the magnetic field. During the freezing process, the fan 103 can promote air circulation so that the cold air is evenly distributed in the device to ensure that all parts of the fruits and vegetables can fully contact the cold air and achieve rapid and uniform freezing. The temperature controller 105 is used to control and adjust the temperature in the freezing device. The data collector 106 is mainly responsible for collecting and recording various data during the operation of the device, and can collect temperature data measured by the thermocouple 101, magnetic field strength data measured by the Gauss meter 107, etc. The AC power supply 104 provides power for the entire device.

[0039] It should be understood that Figure 1 The number of device settings in the figure is only for reference. Depending on the actual situation, there may be device modules with any number and functions.

[0040] Figure 2 The flowchart of the method for magnetic field-assisted freezing of fruits and vegetables according to an embodiment of the present disclosure is schematically shown.

[0041] like Figure 2 As shown, the magnetic field assisted freezing method 200 of fruits and vegetables in this embodiment includes operations S210 to S230.

[0042] In operation S210, the fruits and vegetables are cooled for a predetermined period of time to obtain fruits and vegetables to be frozen.

[0043] In operation S220, the working parameters are determined based on the mapping relationship between the fruits and vegetables to be frozen and the working parameters.

[0044] In operation S230, after adjusting the magnetic field environment during the freezing process according to the working parameters, the fruits and vegetables to be frozen are placed in the magnetic field environment for freezing. When the fruits and vegetables to be frozen meet the preset conditions, the target fruits and vegetables are obtained and transferred to the target environment.

[0045] According to the embodiments of the present disclosure, the cooling treatment may be to place the fruits and vegetables before freezing in a low-temperature environment for storage for a period of time to reduce the activity of enzymes inside the fruits and vegetables, thereby reducing the respiration intensity of the fruits and vegetables; it may also be to pre-cool the fruits and vegetables before freezing by air cooling, so that the field heat and respiratory heat of the fruits and vegetables are quickly taken away by cold air; it may also be to soak the fruits and vegetables before freezing in cold water to quickly reduce the temperature.

[0046] Magnetic field can inhibit the nucleation of ice crystals, significantly reduce the size of ice crystals, reduce mechanical damage to food, and increase supercooling, speed up freezing, promote food refrigeration and extend shelf life. Magnetic field-assisted freezing can also effectively inhibit the conversion of fixed water to free water in frozen fruits and vegetables and improve the water molecule binding capacity of frozen fruits and vegetables.

[0047] According to an embodiment of the present disclosure, the working parameters include magnetic field strength and magnetic field frequency, the magnetic field strength is ≥ 2mT, and the magnetic field frequency is ≥ 50Hz. Under different working parameters, the freezing effect is different. For example, when the magnetic field strength is large, a large amount of Joule heat will be generated, which will have an adverse effect on the freezing process. Therefore, selecting appropriate magnetic field strength and magnetic field frequency will help to form smaller ice crystals when freezing fruits and vegetables, inhibit the growth of ice crystals, and thus maintain the integrity of the cell structure of fruits and vegetables, retain the nutrients of fruits and vegetables, and improve the freezing quality of fruits and vegetables during the freezing process.

[0048] The following will take bamboo shoots as an example to describe the method of magnetic field-assisted freezing of fruits and vegetables of the disclosed embodiment: refrigerate the bamboo shoots for 12 hours to obtain the bamboo shoots to be frozen, determine the magnetic field strength to be 2mT, and the magnetic field frequency to be 70Hz. According to the working parameters, adjust the magnetic field environment during the freezing process, use anemometer, thermostat and gauss meter to calibrate the environmental conditions, and ensure that the wind speed, temperature and magnetic field strength meet the predetermined requirements. Then place the bamboo shoots in a magnetic field environment for freezing. When the bamboo shoots are frozen to meet the preset conditions, transfer the small bamboo shoots to end the freezing process.

[0049] The damage of ice crystals formed by freezing to the cell structure and the further dripping and softening of the texture of the sample after thawing are considered to be the main reasons for the deterioration of sample quality caused by freezing. Therefore, reducing the damage of freezing to cells is the key to improving the quality of frozen products.

[0050] In order to evaluate the effect of the magnetic field-assisted freezing method on the internal microstructure of bamboo shoots, the method of directly observing the gaps in the tissues of freeze-dried samples was used to visually display the ice crystal morphology after freezing. At the same time, a control group was set up to better compare the effect of magnetic field-assisted freezing on the freezing process of fruits and vegetables: the bamboo shoots in the control group were not added with a magnetic field, but in order to eliminate the thermal effect caused by the magnetic field of the coil, the calorific value of the coil in the control group was the same as that of the experimental group.

[0051] First, the bamboo shoots were freeze-dried: the middle part of the frozen bamboo shoot samples was cut into 0.3 mm thick slices using a cryostat, the temperature of the cryostat was set to -25°C, the 0.3 mm thick bamboo shoot slices were placed between a slide and a cover glass that had been cooled to -30°C in advance, and the slide and cover glass containing the samples were placed in a freeze dryer for freeze drying. The dried samples were then placed under an optical microscope for photography and video, and the photographed images were processed and analyzed using image analysis software to obtain information such as the total area of ​​ice crystals, the average area of ​​ice crystals, the proportion of ice crystal area, and the maximum ice crystal area.

[0052] Figure 3A The microscopic microstructure result diagram of ordinary frozen bamboo shoots according to an embodiment of the present disclosure is schematically shown. Figure 3B The microscopic microstructure result diagram of magnetic field-assisted freezing of bamboo shoots according to an embodiment of the present disclosure is schematically shown.

[0053] like Figure 3A and Figure 3B As shown in the figure, the ice crystal area of ​​bamboo shoots after magnetic field assisted freezing is smaller than that of bamboo shoots without magnetic field assisted freezing. Specifically, the ice crystal area can be reduced by 60.7% and the proportion of ice crystal area in the maximum range can be reduced by 80.8%, indicating that magnetic field assisted freezing of fruits and vegetables can effectively reduce the ice crystal area and the proportion of ice crystal area in the maximum range, thereby improving the effect of freezing fruits and vegetables.

[0054] According to the embodiment of the present disclosure, after cooling the fruits and vegetables, the fruits and vegetables to be frozen are obtained. Based on the mapping relationship between the fruits and vegetables to be frozen and the working parameters, the parameter values ​​of the magnetic field strength and the magnetic field frequency are determined, wherein the magnetic field strength is ≥ 2mT and the magnetic field frequency is ≥ 50Hz, so as to determine the magnetic field environment in which the fruits and vegetables to be frozen are frozen, and then the fruits and vegetables to be frozen are placed in the above magnetic field environment for freezing. By reasonably setting the working parameters of the fruits and vegetables in the magnetic field freezing process, the freezing effect of the fruits and vegetables is improved, and the quality of the frozen fruits and vegetables is improved.

[0055] According to the embodiments of the present disclosure, the magnetic field strength includes 2~6mT, and the magnetic field frequency includes 50~90Hz.

[0056] The above working parameters are further explained below in conjunction with specific embodiments.

[0057] The small bamboo shoots with similar appearance size were peeled, the heads and tails were removed, and then cut into 10cm sections, each weighing 10g±1g. The working parameters of the magnetic field assisted freezing device were set, the magnetic field strength was set to 2, 4, and 6mT, and the magnetic field frequency was set to 50, 70, and 90Hz, respectively. A control group was set at the same time, and a total of 12 groups of control groups and treatment groups were obtained. Before the freezing began, the anemometer, thermostat, and gauss meter were used to calibrate the environmental conditions to ensure that the wind speed, temperature, and magnetic field strength all met the predetermined requirements. The magnetic field strength generated by the Helmholtz coil was measured using a digital millitesla meter. The above-mentioned bamboo shoot samples to be frozen were placed in a magnetic field assisted freezing device for freezing. After the freezing was completed, the frozen samples were transferred to a refrigerator at 10°C for thawing for 4 hours, and then the bamboo shoot samples of the treatment group and the control group were subjected to relevant inspections. Specifically, the thawing weight loss, color change, pH, moisture distribution, and other indicators of the bamboo shoots after thawing were detected to analyze the freezing effect of fruits and vegetables subjected to magnetic field assisted freezing under the above working parameters. To ensure the reliability of the results, each group of experiments was repeated 3 times, and the average value was taken as the final result.

[0058] The working parameter conditions of the treatment group and the control group are as follows: MF1 - alternating magnetic field strength 2mT, magnetic field frequency 50Hz; MF2 - alternating magnetic field strength 2mT, magnetic field frequency 70Hz; MF3 - alternating magnetic field strength 2mT, magnetic field frequency 90Hz; MF4 - alternating magnetic field strength 4mT, magnetic field frequency 50Hz; MF5 - alternating magnetic field strength 4mT, magnetic field frequency 70Hz; MF6 - alternating magnetic field strength 4mT, magnetic field frequency 90Hz; MF7 - alternating magnetic field strength 6mT, magnetic field frequency 50Hz; MF8 - alternating magnetic field strength 6mT, magnetic field frequency 70Hz; MF9 - alternating magnetic field strength 6mT, magnetic field frequency 90Hz; CK1 - the heat generated by the coil when the reference alternating magnetic field strength is 2mT. Based on this, a current of the same power is passed through the heating wire to eliminate the thermal effect brought by the magnetic field of the coil. CK2——Refer to the heating value of the coil when the alternating magnetic field strength is 4mT. Based on this, the same power current is passed through the heating wire to eliminate the thermal effect caused by the coil magnetic field. CK3——Refer to the heating value of the coil when the alternating magnetic field strength is 6mT. Based on this, the same power current is passed through the heating wire to eliminate the thermal effect caused by the coil magnetic field. Note: When the alternating magnetic field strength is the same, the heating value of the coil remains basically unchanged at frequencies of 50Hz, 70Hz, and 90Hz.

[0059] By recording the changes in the center temperature of bamboo shoots under different working parameters, the temperature-time freezing curve of bamboo shoots was obtained. The freezing parameters can be obtained through this curve and used to evaluate the effects of freezing dynamics and electromagnetic fields on the freezing process. Specifically, the paperless recorder records the changes in the center temperature of bamboo shoots under the action of the magnetic field in real time, recording every 2 seconds, from the initial temperature of 25°C until the target end temperature of -18°C is reached. The freezing curves of each group and the time required for each group in the precooling stage, phase change stage and supercooling stage were recorded.

[0060] By recording the temperature changes and the time required for each stage of the freezing process of each group of bamboo shoots, it was found that there was no supercooling phenomenon in the different treatment groups. The freezing time required for bamboo shoots frozen in the magnetic field intensity of 2-6mT and the magnetic field frequency of 50-90Hz was significantly shortened, and the freezing time required for the MF4 group was significantly shorter than that of the other groups. Compared with the control group, the freezing time of bamboo shoots samples in the MF4 treatment group was shortened by 20.06%.

[0061] Figure 4 The freezing curve diagram under different working parameters according to the embodiment of the present disclosure is schematically shown.

[0062] Figure 4 The freezing curves of four groups of samples are included, such as Figure 4 As shown in the figure, the freezing time of MF1, MF2, and MF3 is shorter than that of CK1, which means that when fruits and vegetables are in a magnetic field environment with an alternating magnetic field strength of 2mT and a magnetic field frequency of 50Hz~90Hz, the time required to reach the target end temperature of -18℃ from the initial temperature of 25℃ is shorter than the time required when no magnetic field assisted freezing is performed, indicating that the method of magnetic field assisted freezing of fruits and vegetables helps to shorten the freezing time and improve the freezing effect. In addition, when the magnetic field strength is 2mT and the magnetic field frequency is 70Hz, the required freezing time is the smallest.

[0063] The weight loss of bamboo shoots before and after freezing was characterized by using a precision electronic balance to record the weight of each treatment group and control group before freezing and the weight of the sample after thawing. After thawing, the sample was weighed immediately after gently wiping the surface moisture of the sample with absorbent paper. The weight change rate was calculated based on the value related to the initial value. Each group of experimental samples was set up for 3 repeated tests. The change rate calculation formula is shown in the following formula (1):

[0064] (1)

[0065] Among them, m0 represents the weight before freezing, m1 represents the weight after freezing, and WL represents the weight change rate.

[0066] Figure 5 A bar chart schematically shows the weight loss changes of bamboo shoots under different working parameters according to an embodiment of the present disclosure.

[0067] like Figure 5 As shown in the figure, compared with the control group, the three magnetic field frequencies of 2mT magnetic field strength can reduce the weight loss rate, among which the MF1 group has the largest reduction, reaching 25.37%. When the magnetic field intensity is 4mT, with the increase of magnetic field frequency, the weight loss first remains unchanged and then increases. Compared with the control group, the three magnetic field frequencies of 4mT magnetic field strength can reduce the weight loss rate, among which the MF4 group has the largest reduction, reaching 20.05%. When the magnetic field intensity is 6mT, with the increase of magnetic field frequency, the weight loss first decreases and then increases. Compared with the control group, the three magnetic field frequencies of 6mT magnetic field strength can reduce the weight loss rate, among which the MF8 group has the largest reduction, reaching 16.51%. When the magnetic field frequency is 50Hz and 70Hz, the weight loss gradually increases with the increase of magnetic field intensity. However, when the magnetic field frequency is 70Hz, the weight loss first increases and then decreases with the increase of magnetic field intensity. When the magnetic field intensity is low, the 50 Hz magnetic field frequency has a significant effect on reducing weight loss, but when the magnetic field intensity increases to 6 mT, the 70 Hz magnetic field frequency has a significant effect on reducing weight loss.

[0068] The pH of bamboo shoots before and after freezing was characterized to observe the changes in bamboo shoots before and after freezing.

[0069] Figure 6 A bar chart schematically shows pH changes of bamboo shoots under different working parameters according to an embodiment of the present disclosure.

[0070] like Figure 6 As shown in the figure, the pH of the samples in the alternating magnetic field treatment group was higher than that in the control group. Except for the MF8 and MF9 groups, the other test groups were significantly different from the control group (p<0.05). At 2mT magnetic field strength, with the increase of magnetic field frequency, pH increased first and then decreased. The pH of the MF2 group increased the most compared with the control group, which was 4.01%. At 4mT magnetic field strength, with the increase of magnetic field frequency, pH gradually decreased. The pH of the MF4 group increased the most compared with the control group, which was 3.31%. At 6mT magnetic field strength, with the increase of magnetic field frequency, pH gradually decreased. The pH of the MF7 group increased the most compared with the control group, which was 1.31%.

[0071] The shading degree and sugar content of bamboo shoots before and after freezing were characterized. 3g of sample was cut into 6 sections of the same length and placed in a clean beaker. 40mL of distilled water was added to the beaker, and then the beaker was placed in a speed-controlled oscillator for 1 hour. The mixed solution after shaking was measured by a high-precision sugar refractometer, and 3 values ​​were measured each time and the average value was taken.

[0072] Figure 7 A bar graph schematically shows the change in shading degree of bamboo shoots under different working parameters according to an embodiment of the present disclosure.

[0073] like Figure 7 As shown in the figure, alternating magnetic field intensity and frequency can effectively reduce the shading degree (P<0.05). At 2mT magnetic field intensity, as the magnetic field frequency increases, the shading degree first increases and then decreases. At 4mT magnetic field intensity, as the magnetic field frequency increases, the shading degree first decreases and then increases. At 6mT magnetic field intensity, as the magnetic field frequency increases, the shading degree gradually decreases. Among them, compared with the control group, the MF5 group had the largest decrease in all magnetic field treatment groups.

[0074] Figure 8 A bar chart schematically shows the sugar content change of bamboo shoots under different working parameters according to an embodiment of the present disclosure.

[0075] like Figure 8 As shown in the figure, the trend of sugar content is basically consistent with the obscuration degree, and high obscuration degree is usually associated with higher sugar content, because sugar can increase the obscuration degree of the sample tissue fluid.

[0076] The color change of bamboo shoots before and after freezing was characterized, and the surface moisture of the thawed samples was wiped with absorbent paper. The color value of bamboo shoot samples was measured using a handheld colorimeter, and 3 parallel experiments were performed for each group of samples. After correction with a standard white box and a black box, the test plane was directly placed on the sample surface, and the L*, a*, and b* values ​​measured in the CIELAB color space were used to characterize the sample color value, where △L* represents lightness, and a* and b* represent chromaticity. The △E value is the total color difference, and the calculation formula is as follows:

[0077] (2)

[0078] Among them, △E represents the total color difference, △L* represents the brightness change, △a* represents the chromaticity change from the red to green color gamut, △b* represents the chromaticity change from the yellow to blue color gamut, L0* represents the brightness before freezing, L1* represents the brightness after freezing, a0* represents the chromaticity of the red to green color gamut before freezing, a1* represents the chromaticity of the red to green color gamut before freezing, b0* represents the chromaticity of the yellow to blue color gamut before freezing, and b1* represents the chromaticity of the yellow to blue color gamut before freezing.

[0079] Table 1 shows the color changes of bamboo shoots under different working parameters:

[0080]

[0081] Compared with directly freezing bamboo shoots, alternating magnetic field can reduce the change of ∆E value of bamboo shoot samples. As shown in Table 1, when the magnetic field strength is 2mT, the decrease of ∆E value gradually increases with the increase of magnetic field frequency. When the magnetic field strength is 4mT, the decrease of ∆E value first increases, then decreases, and then increases again with the increase of magnetic field frequency. When the magnetic field strength is 6mT, the decrease of ∆E value gradually increases with the increase of magnetic field frequency. The decrease of ∆E value reaches the lowest point at 4mT and 90Hz (p < 0.05), with a decrease of 21.27%.

[0082] The moisture state and distribution of bamboo shoots before and after freezing were characterized. About (3.00±0.05) g of thawed bamboo shoot samples were weighed and placed in a nuclear magnetic resonance tube, which was then placed in a low-field nuclear magnetic resonance analyzer (NMR, Shanghai Newmai Electronics, NMI20). The transverse relaxation time T2 signal of water protons in bamboo shoot samples was determined using the CPMG (Carr-purcell-meiboom-gillsequence) pulse sequence. The main parameters were set as follows: repeated sampling time interval TW=2000 ms, sampling frequency SW=100kHz, cumulative scanning times NS=8, echo number NECH=2000, the number of iterations for batch inversion was 300,000, and 3 repeated tests were set for each group of experimental samples.

[0083] A typical proton NMR spectrum has three typical peaks, namely bound water (A21 0.1-10 ms), fixed water (A22 10-100 ms) and free water (A23 > 100 ms). The transverse relaxation time T2 of the water in the treated group samples can be divided into four different water populations observed at 0-1 ms (T2b1), 1-10 ms (T2b2), 10-100 ms (T21) and 100-1000 ms (T22). The shortest relaxation times T2b1 and T2b2 represent strongly bound water (very strongly bound to macromolecules) and weakly bound water (strongly bound to macromolecules), respectively, with the fastest relaxation rate and the lowest mobility; the T21 peak relaxation time is medium, indicating that the water is immobile and has low mobility. T21 represents the fixed water in the dense network of bamboo shoot fibers; the T22 peak relaxation time is the longest, indicating free water with the highest mobility. T22 represents the free water in the space between fiber bundles, which depends on the size of the capillary force. The peak area ratios appearing in each time period are the contents of different forms of water corresponding to P2a, P2b, P21, and P22. The peak area percentage content P2 represents the sample's ability to bind water molecules. The shorter the T2 value, the stronger the sample's ability to bind water molecules, and vice versa. P2 represents the relative water content of the corresponding group. The larger the P2, the higher the relative water content of the recombinant group, and vice versa.

[0084] Fig.9AThe figure schematically shows the low-resolution nuclear magnetic resonance spectrum result of the sample when the magnetic field strength is 2mT according to an embodiment of the present disclosure. Fig. 9B The figure schematically shows the low-resolution nuclear magnetic resonance spectrum result of the sample when the magnetic field strength is 4 mT according to an embodiment of the present disclosure. Fig. 9C The figure schematically shows the result of low-resolution nuclear magnetic resonance spectrum of the sample when the magnetic field strength is 6 mT according to an embodiment of the present disclosure.

[0085] like Figure 9A to Figure 9C As shown in the figure, the transverse relaxation time T2 of the sample water in the control group can only be observed at 1-10 ms (T2b2), 10-100 ms (T21) and 100-1000 ms (T22), but not 0-1 ms (T2b). The possible reason is that the magnetic field treatment can shift the transverse relaxation time T2 of the sample water to the left. Compared with the control group, the treatment of the alternating magnetic field can increase the fixed water and bound water in the sample and reduce the free water.

[0086] The T22 of bamboo shoots frozen by magnetic field assisted changed significantly compared with the control group (P < 0.05), indicating that magnetic field assisted freezing treatment had a significant effect on the moisture state of bamboo shoots. The T22 of samples of each freezing method under different intensities and different magnetic field frequencies of the alternating magnetic field was significantly reduced (P < 0.05). The T22 peaks of bamboo shoots samples in each control group and treatment group were the largest, indicating that most of the water in the samples was highly fluid free water. The order of T22 of bamboo shoots samples in the control group and treatment group was: CK2>CK3>CK1>MF6>MF9>MF3>MF7>MF2>MF8>MF1>MF4>MF5. This indicates that the binding ability of samples in the control group to water molecules was weaker than that in the experimental group (P < 0.05). This shows that the treatment caused the fluidity of the remaining water in the sample to decrease, and the magnetic field treatment reduced the formation of free water in the sample after thawing. This may be due to the dripping loss of highly fluid water after thawing, while the fluidity of the remaining water in the sample in the treatment group was low, and magnetic field assisted freezing helped to improve the binding ability of water molecules in the sample after thawing.

[0087] As shown in Table 2, freezing and thawing changed the water fluidity of bamboo shoots, and the area and position of the T22 peak of bamboo shoots treated with different treatments changed significantly. Compared with the control group, the P22 of samples of each freezing method under different intensities and frequencies of alternating magnetic field was significantly reduced (P<0.05), and the reduction range was MF1>MF9>MF3>MF6>MF8>MF4>MF7>MF5>MF2. Among the three control groups, CK2 had the largest P22, followed by CK3, and CK1 had the smallest P22, but the P22 of the three control groups was >0.9811, which may be because the ice crystals formed by freezing destroyed the cell structure of bamboo shoots and further destroyed the water binding state. After thawing, the original water binding state cannot be completely restored, resulting in an increase in the proportion of free water. Comparing the effects of different magnetic field-assisted freezing methods, the samples of treatment groups MF1 and MF5 showed the most obvious effects (P<0.05), with their P22 and T22 values ​​being smaller, and P2a and T2a values ​​being larger. This may be because the magnetic field assisted treatment inhibited the formation of large ice crystals, reduced the damage of ice crystals to the bamboo shoot fiber network structure, and reduced the exposure of hydrophobic groups, thereby inhibiting the increase in the mobility of fixed water. Correspondingly, the fixed water content (P21) of the magnetic field assisted treatment group was significantly higher than that of other control groups (P < 0.05), indicating that the magnetic field assisted treatment effectively inhibited the conversion of fixed water to free water in the frozen bamboo shoot samples. On the contrary, the P22 and T22 values ​​of the control group CK2 were larger, and the P2a and T2a values ​​were undetectable. These results show that applying appropriate magnetic field intensity and frequency can delay the increase in water mobility of bamboo shoot samples, and the effect of the magnetic field improves the freezing process of the samples, reduces freezing damage, and thus better maintains the water state of the frozen samples. This may be because the magnetic field can induce the formation of small ice crystals.

[0088] Table 2 shows the changes in moisture distribution area of ​​bamboo shoots under different working parameters:

[0089]

[0090] The above results all indicate that magnetic field-assisted freezing with a magnetic field strength of 2-6 mT and a magnetic field frequency of 50-90 Hz can delay the fluidity of water in bamboo shoots samples, and the effect of delaying the fluidity of water in bamboo shoots samples is best when the magnetic field strength is 2 mT and the magnetic field frequency is 90 Hz or the magnetic field strength is 2 mT and the magnetic field frequency is 70 Hz.

[0091] According to the embodiments of the present disclosure, when the magnetic field intensity ranges from 2 to 6 mT and the magnetic field frequency ranges from 50 to 90 Hz, compared with freezing without magnetic field assisted freezing, magnetic field assisted freezing can reduce the weight loss of frozen fruits and vegetables, reduce the loss of nutrients in frozen fruits and vegetables, such as reducing the loss of sugar content, and can reduce the color change of fruits and vegetables during the freezing process. More importantly, it can inhibit the conversion of fixed water to free water in frozen fruits and vegetables, delay the fluidity of water in frozen fruits and vegetables, and better maintain the water state of frozen fruits and vegetables. By reasonably setting the working parameter range, mechanical damage and nutrient loss during the freezing process of fruits and vegetables can be effectively reduced, and the effect of freezing fruits and vegetables can be improved.

[0092] According to an embodiment of the present disclosure, determining the working parameters based on the mapping relationship between the fruits and vegetables to be frozen and the working parameters includes: determining the types of the fruits and vegetables to be frozen; and determining the working parameters according to the mapping relationship between the types of the fruits and vegetables to be frozen and the working parameters.

[0093] According to the embodiments of the present disclosure, fruits and vegetables include various types, such as apples, bananas, etc., vegetables, berries, etc. Different types of fruits and vegetables have different respiration intensities, water contents, and nutrient contents, and different sensitivities to magnetic fields. Therefore, it is necessary to select appropriate magnetic field strength and magnetic field frequency according to the types of fruits and vegetables to improve the freezing effect and freezing quality of fruits and vegetables in the magnetic field assisted freezing process.

[0094] The mapping relationship between the types of fruits and vegetables to be frozen and the working parameters includes the corresponding relationship between different types of fruits and vegetables and magnetic field strength and magnetic field frequency. The above corresponding relationship can be based on historical test data of different types of fruits and vegetables under different working parameters, and the corresponding relationship list between the types of fruits and vegetables and the working parameters can be obtained by analysis for search.

[0095] For example: bamboo shoots are subjected to magnetic field assisted freezing. According to the historical test data of magnetic field assisted freezing of bamboo shoots in a magnetic field assisted freezing device, a corresponding list of bamboo shoots, working parameters and freezing quality is obtained. Based on the above correspondence list, the optimal working parameters of the bamboo shoots are determined as follows: the magnetic field intensity is 2mT, and the magnetic field frequency is 70Hz.

[0096] In addition, the correspondence between different types of fruits and vegetables and magnetic field strength and magnetic field frequency can also be calculated by a neural network algorithm for optimizing and predicting working parameters, wherein the neural network algorithm for optimizing and predicting working parameters can be trained using historical samples and corresponding working parameters.

[0097] According to an embodiment of the present disclosure, based on the mapping relationship between the fruits and vegetables to be frozen and the working parameters, determining the working parameters also includes: determining the working parameters based on the mapping relationship between the volume and shape of the fruits and vegetables to be frozen and the working parameters. Fruits and vegetables of different volumes and shapes have different abilities to conduct heat in the magnetic field, which in turn affects the effect of magnetic field-assisted freezing. Therefore, it is necessary to select appropriate magnetic field strength and magnetic field frequency according to the volume and shape of the fruits and vegetables to improve the freezing effect and freezing quality of the fruits and vegetables during the magnetic field-assisted freezing process.

[0098] According to the embodiments of the present disclosure, different types of fruits and vegetables have different sensitivities to magnetic fields. Based on the mapping relationship between different types of fruits and vegetables and working parameters, appropriate working parameters can be determined according to the types of fruits and vegetables to be frozen. The working parameters can be optimized based on actual conditions, thereby improving the freezing effect and quality of fruits and vegetables.

[0099] According to an embodiment of the present disclosure, the working parameters also include wind speed, wherein the wind speed is ≤1.5 m / s.

[0100] During the freezing process, the wind speed will affect the freezing time of the freezing process. When the wind speed increases, the air flow on the surface of fruits and vegetables will accelerate, and the rate of heat transfer will also accelerate. The amount of heat taken away from the surface of fruits and vegetables per unit time will increase, allowing the fruits and vegetables to dissipate heat to the surrounding environment faster, thereby shortening the freezing time. However, the relationship between wind speed and freezing time is also affected by other factors, such as magnetic field strength. Therefore, the embodiments of the present disclosure study the freezing time of the freezing process under different wind speeds and different magnetic field strengths.

[0101] The freezing time of bamboo shoot samples with different magnetic field strengths and wind speeds was tested at a magnetic field frequency of 70 Hz. The test results are shown in Table 3 below:

[0102] Table 3 shows the time required for the sample to cool from the initial temperature to -18°C under different wind speeds and different magnetic field strengths.

[0103]

[0104] As shown in Table 3, the freezing time is shorter when the magnetic field is assisted in freezing, but the higher the wind speed, the shorter the freezing time. When the wind speed is 1-1.5 m / s, the freezing time is shorter than that of other treatment groups. It is worth noting that the treatment time of 1.5 m / s wind speed is shorter than that of other wind speeds, and the treatment time of 2 mT and 70 Hz combination is the shortest.

[0105] According to the embodiments of the present disclosure, during magnetic field-assisted freezing, wind speed has a significant impact on the freezing time of the freezing process. Under different magnetic field strengths and different wind speeds, the freezing time of fruits and vegetables is different. When the wind speed is ≤1.5m / s, the freezing time is shorter. When the magnetic field strength is 2mT and the magnetic field frequency is 70Hz, the freezing time is shortest when the wind speed is 1.5m / s.

[0106] According to an embodiment of the present disclosure, placing the fruits and vegetables to be frozen in a magnetic field environment for freezing includes: placing the fruits and vegetables to be frozen in a uniform magnetic field for freezing.

[0107] A uniform magnetic field can be formed by a Helmholtz coil, which consists of two identical circular coils. When equal current flows through the two coils, an almost uniform magnetic field will be generated between them. Near the center area of ​​the two coils, due to the symmetry of the two coils, the magnetic field in this area is mainly along the axial direction and evenly distributed.

[0108] Placing the to-be-frozen fruits and vegetables in a uniform magnetic field for freezing includes placing the to-be-frozen fruits and vegetables on the axis of the Helmholtz coil in the same direction for freezing.

[0109] According to the embodiments of the present disclosure, placing the fruits and vegetables to be frozen in a uniform magnetic field for freezing can ensure that when the fruits and vegetables are frozen in the magnetic field environment, the magnetic field environment of each part of the fruits and vegetables is the same, for example, the same magnetic field strength and magnetic field frequency, thereby ensuring that the freezing effect of each part of the fruits and vegetables is the same, reducing the decrease in the freezing effect of the entire fruits and vegetables due to poor local freezing effect, and improving the freezing effect and freezing quality of fruits and vegetables during magnetic field-assisted freezing.

[0110] According to an embodiment of the present disclosure, the magnetic field environment includes a one-dimensional alternating magnetic field.

[0111] The alternating magnetic field can be excited by passing alternating current through a coil to form an electromagnetic field.

[0112] The multi-dimensional alternating magnetic field requires a combination of multiple coils or magnetic field sources in different directions, such as multiple mutually perpendicular electromagnets or coil arrays. In magnetic field-assisted freezing, when a multi-dimensional alternating magnetic field is used for magnetic field-assisted freezing, it is necessary to control the magnetic field strength and the magnitude of the magnetic field frequency through a multi-dimensional coil, and multiple independently controlled power supplies are required to supply power to magnetic field sources in different directions, so as to accurately adjust the magnetic field strength, frequency and phase in each direction. The control of the working parameters is difficult. In addition, the magnetic field environment formed by the multi-dimensional alternating magnetic field is also more complex. Accordingly, in order to meet the formation of a multi-dimensional alternating magnetic field, it is necessary to design more complex devices and equipment, which increases the difficulty of applying magnetic field-assisted freezing of fruits and vegetables.

[0113] Compared with multi-dimensional alternating magnetic fields, one-dimensional alternating magnetic fields are usually generated by a single or a group of coils with specific shapes and winding methods. The direction of the magnetic field changes periodically along a specific axis. It can be powered by a single AC power supply. The intensity and frequency of the magnetic field can be controlled by adjusting the frequency, voltage and other parameters of the power supply. The control operation of the working parameters is simpler and the control difficulty is small. In addition, good uniformity can be achieved in a certain area near the axis of the one-dimensional alternating magnetic field. The devices and equipment required for the one-dimensional alternating magnetic field are simpler, and the manufacturing cost of the devices and equipment is low, which helps the method of magnetic field-assisted freezing of fruits and vegetables to achieve a wider application.

[0114] According to the embodiments of the present disclosure, by adopting a one-dimensional alternating magnetic field, the working parameters can be better controlled, making the operation of the method of magnetic field-assisted freezing of fruits and vegetables simpler, which helps to achieve a wider application of the method of magnetic field-assisted freezing of fruits and vegetables.

[0115] According to an embodiment of the present disclosure, cooling fruits and vegetables for a predetermined time to obtain fruits and vegetables to be frozen includes: cooling fruits and vegetables for a predetermined time to reduce the respiration intensity of fruits and vegetables to obtain fruits and vegetables to be frozen, wherein the predetermined time is ≥ 10 hours.

[0116] According to the embodiments of the present disclosure, fruits and vegetables often show a high respiration intensity before being frozen. This is because in a natural room temperature environment, cells still maintain relatively active physiological metabolic activities and continuously consume the nutrients stored in the fruits and vegetables themselves, which brings difficulties to the subsequent storage and preservation of fruits and vegetables. Therefore, before freezing fruits and vegetables, they need to be cooled to reduce the activity of enzymes inside fruits and vegetables, so as to reduce the respiration intensity of fruits and vegetables.

[0117] The fruits and vegetables are cooled for a predetermined time, which may be 10 hours, 12 hours, or 16 hours, and may be determined based on the type and volume of the fruits and vegetables, and is not limited here.

[0118] According to an embodiment of the present disclosure, fruits and vegetables are cooled for a predetermined time to obtain fruits and vegetables to be frozen, including: after the fruits and vegetables are cooled for a predetermined time, the central temperature of the fruits and vegetables is measured, and when the central temperature meets a threshold range, the fruits and vegetables to be frozen are obtained, and the central temperature includes 6~10℃.

[0119] After cooling the fruits and vegetables for a predetermined time, the temperature of the center of the fruits and vegetables can be measured by a thermocouple, where the center of the fruits and vegetables is the geometric center of the fruits and vegetables, and the thermocouple can be a T-type thermocouple. Specifically, after cooling the fruits and vegetables for a predetermined time, insert the T-type thermocouple into the geometric center of the fruits and vegetables, and the paperless recorder records the changes in the center temperature of the fruits and vegetables, with a measurement accuracy of ±0.01°C. When the measured center temperature is 6~10°C, the cooling process is completed and used for subsequent freezing of fruits and vegetables.

[0120] According to the embodiments of the present disclosure, fruits and vegetables are cooled for a predetermined period of time so that the core temperature of the fruits and vegetables meets a threshold value, and then the fruits and vegetables are subjected to magnetic field-assisted freezing. This can effectively reduce the respiration intensity of fruits and vegetables before freezing, thereby improving the subsequent freezing effect and the quality of frozen fruits and vegetables.

[0121] According to an embodiment of the present disclosure, when the fruits and vegetables to be frozen meet preset conditions, target fruits and vegetables are obtained and transferred to a target environment, including: measuring the central temperature of the fruits and vegetables to be frozen, and in response to the central temperature of the fruits and vegetables to be frozen being less than -18°C, obtaining the target fruits and vegetables and transferring the target fruits and vegetables to the target environment.

[0122] According to the embodiments of the present disclosure, the central temperature of fruits and vegetables is less than -18°C, which is the temperature standard for good freezing of fruits and vegetables. When the temperature is lower than -18°C, the growth and reproduction activities of most microorganisms (such as bacteria, molds and yeasts) will be greatly restricted. In addition, in an environment of -18°C, it becomes difficult for the active center of the enzyme to bind to the substrate, the reaction rate is significantly reduced, the activity of the enzyme related to respiration is greatly reduced, and the respiration is almost stopped. Therefore, this is used as the standard temperature for complete freezing.

[0123] According to the embodiment of the present disclosure, the method for measuring the core temperature of fruits and vegetables to be frozen is the same as the method for measuring the core temperature of fruits and vegetables after cooling treatment, which will not be repeated here. The difference is that the change of the core temperature of fruits and vegetables under the action of the magnetic field is recorded in real time by a paperless recorder, once every 2 seconds, from the initial temperature of 25°C until the target end temperature of -18°C is reached.

[0124] Transfer the target fruits and vegetables to the target environment. The target fruits and vegetables can be potatoes, bamboo shoots, green beans, chestnuts, etc. The target environment is set according to actual needs. It can be a thawing environment of 0~4℃ or a water bath environment with a certain heating temperature.

[0125] Based on the above method of magnetic field-assisted freezing of fruits and vegetables, the time for the target fruits and vegetables to pass through the maximum ice crystal formation zone is less than 20 minutes.

[0126] The maximum ice crystal formation zone refers to the temperature range in which the center temperature of fruits and vegetables drops from -1°C to -5°C during the freezing process. Within this temperature range, nearly 80% of the water in fruits and vegetables can be frozen into ice, and the amount of ice crystals generated is the largest. The time to pass through the maximum ice crystal formation zone indicates the time required for the center temperature of fruits and vegetables to drop from -1°C to -5°C. If the time to pass through the maximum ice crystal formation zone is shorter, the smaller the ice crystals formed and the more evenly distributed they are, and the less damage to cells there will be, which helps to maintain the quality of fruits and vegetables. On the contrary, if the time to pass through this temperature zone is longer, the ice crystals formed will be larger, which may puncture the cell membrane, resulting in severe juice loss after thawing, affecting the value of the food.

[0127] According to the embodiments of the present disclosure, by adopting the above-mentioned magnetic field-assisted freezing method for fruits and vegetables to freeze fruits and vegetables, the time for the target fruits and vegetables to pass through the maximum ice crystal formation zone is less than 20 minutes, which effectively shortens the time for fruits and vegetables to pass through the maximum ice crystal formation zone, helps to form small and uniform ice crystals, reduces damage to cells, improves the quality of fruit and vegetable freezing, and improves the freezing effect of fruits and vegetables.

[0128] The flow charts and block diagrams in the accompanying drawings illustrate the possible architecture, functions and operations of the systems, methods and computer program products according to various embodiments of the present disclosure. In this regard, each box in the flow chart or block diagram can represent a module, a program segment, or a part of a code, and the above-mentioned module, program segment, or a part of a code contains one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram or flow chart, and the combination of the boxes in the block diagram or flow chart can be implemented with a dedicated hardware-based system that performs a specified function or operation, or can be implemented with a combination of dedicated hardware and computer instructions.

[0129] It will be appreciated by those skilled in the art that the features described in the various embodiments of the present disclosure may be combined and / or combined in a variety of ways, even if such combinations or combinations are not explicitly described in the present disclosure. In particular, without departing from the spirit and teachings of the present disclosure, the features described in the various embodiments of the present disclosure may be combined and / or combined in a variety of ways. All of these combinations and / or combinations fall within the scope of the present disclosure.

[0130] The embodiments of the present disclosure are described above. However, these embodiments are only for illustrative purposes and are not intended to limit the scope of the present disclosure. Although the embodiments are described above, this does not mean that the measures in the various embodiments cannot be used in combination to advantage. Without departing from the scope of the present disclosure, those skilled in the art may make a variety of substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. A method for magnetic field-assisted freezing of fruits and vegetables, characterized in that: The method comprises: Cooling the fruits and vegetables for a predetermined period of time to obtain the fruits and vegetables to be frozen; Based on the mapping relationship between the fruits and vegetables to be frozen and the working parameters, the working parameters are determined, wherein the working parameters include magnetic field strength and magnetic field frequency, the magnetic field strength is ≥ 2mT, and the magnetic field frequency is ≥ 50Hz; After adjusting the magnetic field environment during the freezing process according to the working parameters, the fruits and vegetables to be frozen are placed in the magnetic field environment for freezing. When the fruits and vegetables to be frozen meet the preset conditions, target fruits and vegetables are obtained and transferred to the target environment.

2. The method according to claim 1, characterized in that The determining of the working parameters based on the mapping relationship between the fruits and vegetables to be frozen and the working parameters includes: Determining the type of fruits and vegetables to be frozen; The working parameters are determined according to the mapping relationship between the types of fruits and vegetables to be frozen and the working parameters.

3. The method according to claim 1 or 2, characterized in that: The magnetic field strength includes 2-6 mT, and the magnetic field frequency includes 50-90 Hz.

4. The method according to claim 1, characterized in that: The working parameters also include wind speed, wherein the wind speed is ≤1.5m / s.

5. The method according to claim 1, characterized in that Placing the fruits and vegetables to be frozen in the magnetic field environment for freezing comprises: The fruits and vegetables to be frozen are placed in a uniform magnetic field for freezing.

6. The method according to any one of claims 1 to 5, characterized in that The magnetic field environment includes a one-dimensional alternating magnetic field.

7. The method according to claim 1, characterized in that The step of cooling the fruits and vegetables for a predetermined period of time to obtain the fruits and vegetables to be frozen comprises: The fruits and vegetables are subjected to a cooling treatment for a predetermined time so that the respiration intensity of the fruits and vegetables is reduced, thereby obtaining fruits and vegetables to be frozen, wherein the predetermined time is ≥10 hours.

8. The method according to claim 7, characterized in that The step of cooling the fruits and vegetables for a predetermined period of time to obtain the fruits and vegetables to be frozen comprises: After cooling the fruits and vegetables for a predetermined period of time, measuring the core temperature of the fruits and vegetables, and obtaining the fruits and vegetables to be frozen in response to the core temperature satisfying a threshold range, wherein the core temperature includes 6-10°C.

9. The method according to claim 1, characterized in that: When the fruits and vegetables to be frozen meet preset conditions, target fruits and vegetables are obtained, and the target fruits and vegetables are transferred to a target environment, including: The core temperature of the fruits and vegetables to be frozen is measured, and in response to the core temperature of the fruits and vegetables to be frozen being less than -18°C, the target fruits and vegetables are obtained, and the target fruits and vegetables are transferred to a target environment.

10. The method according to claim 1, characterized in that The time for the target fruits and vegetables to pass through the maximum ice crystal formation zone is less than 20 minutes.

Images