Burdock preservation method based on combination of radio frequency and visible light treatment

Abstract

The invention belongs to the technical field of fruit and vegetable fresh-keeping, and discloses a burdock fresh-keeping method based on radio frequency and visible light treatment, which comprises the following steps: cleaning and disinfecting a tray and an inner cavity of a closed container for storage, placing fresh burdock on the tray and then disinfecting the burdock; according to the method, fresh burdock is placed in a tray, the tray and the fresh burdock are placed in a closed container together after disinfection, a radio frequency module and an LED module are arranged in the closed container at the same time, the radio frequency module and the LED module are used for conducting combined treatment of radio frequency and visible light illumination on the burdock at the same time in the storage period, combined treatment is conducted only once in the storage period, and the time of one-time combined treatment is 2 min.

Description

Technical Field

[0001] The present invention belongs to the technical field of fruit and vegetable preservation, and relates to a method for preserving burdock, in particular to a method for preserving burdock based on radio frequency combined with visible light treatment. Background Technique

[0002] As a traditional Chinese medicinal material, burdock is widely used in the field of traditional Chinese medicine and has the effects of clearing heat and detoxifying, promoting blood circulation and removing stasis, and inducing diuresis and reducing swelling. The roots of burdock are rich in dietary fiber, polysaccharides, amino acids, vitamins and minerals, and have certain medicinal value and health care functions. Its main components include volatile oils, flavonoid compounds, phenolic acid compounds, sterol compounds, fatty acids, etc., and have multiple biological activities such as antioxidant, anti-inflammatory and antibacterial. As a Chinese medicinal material, burdock is often used to disperse wind-heat, ventilate the lungs and promote eruption, clear and benefit the throat, as well as clear heat and detoxify, disperse nodules and reduce swelling, and is also applied in modern foods and health products.

[0003] However, the postharvest storage and transportation of burdock have always been important factors affecting its medicinal effects and market value. Burdock has a high water content, and water loss after harvest will affect the stability of its active ingredients, resulting in a decline in medicinal efficacy. Especially during long-term transportation and storage, water loss will accelerate the spoilage and deterioration of burdock, causing its flavor and medicinal components to be lost, thus affecting its quality. Therefore, studying how to effectively retain the water content of burdock, delay water loss after harvest, and maintain its medicinal efficacy and quality is crucial for the processing and market circulation of burdock.

[0004] At present, the preservation technologies of agricultural products such as Chinese medicinal materials can be divided into chemical, biological and physical preservation technologies according to different preservation principles. However, chemical preservatives restrict the green and healthy development of the industry due to their high risk of drug residues, and the operation difficulty and high cost of biological preservation technologies are also not suitable for wide application in the preservation of fresh Chinese medicinal materials. Therefore, developing a safe and effective physical preservation technology that can not only extend the postharvest preservation period of burdock but also does not damage its medicinal value has important research significance and economic value. Summary of the Invention

[0005] Object of the Invention: The object of the present invention is to provide a preservation method based on radio frequency combined with visible light treatment that can effectively delay water loss and browning of burdock and is safe and environmentally friendly. The preservation method is applied to the postharvest storage of fresh burdock.

[0006] Technical Solution: The method for preserving burdock based on radio frequency combined with visible light treatment of the present invention includes the following steps:

[0007] First, clean and disinfect the inner cavities of the tray and the closed container for storage. Place the fresh burdock on the tray and then disinfect the burdock. After disinfection, place the tray and the fresh burdock together in the closed container. The closed container is provided with a radio frequency module and an LED module at the same time. During storage, use the radio frequency module and the LED module to perform radio frequency and visible light illumination treatment on the burdock simultaneously. Only one treatment is performed during storage, and the one-time treatment time is 2 minutes.

[0008] Preferably, the fresh burdock is the burdock taproot with good quality, no cracks, no disease spots, no mechanical damage, no hollow heart, not aged, and uniform thickness. It is the burdock after being washed, the fibrous roots removed, and cut into sections.

[0009] Preferably, the burdock is disinfected with an aqueous solution of NaClO. Further preferably, the concentration of the aqueous solution of NaClO used for disinfection is 200 μL / L, and the disinfection time with the aqueous solution of NaClO is 5 minutes.

[0010] Preferably, the tray is a ceramic tray, and an anti-vibration EPE pearl cotton foam pad is laid inside the tray.

[0011] Preferably, the steps for cleaning and disinfecting the inner cavities of the tray and the closed container for storage are: first wipe with a clean and moist towel and then spray 75% ethanol for disinfection.

[0012] Preferably, the radio frequency output frequency of the radio frequency module is 40.68 MHz, and the radio frequency power is 0.5 - 3 kW.

[0013] Preferably, the light intensity of the LED module is 200 μmol m -2 s -1 , the white light wavelength is 450 nm - 700 nm, the red light is 660 nm, and the blue light is 470 nm.

[0014] It should be noted that the storage period described in the present invention includes the time period of the combined treatment; preferably, the temperature conditions during the storage period are all 15 - 40 °C, and the relative humidity is all 85%.

[0015] Preferably, the distance between the two electrodes of the radio frequency module is 40 cm, and the capacitance rises by 50 mm.

[0016] In a second aspect, based on the method for preserving fresh burdock by combining radio frequency and visible light treatment according to the present invention, the present invention also provides a fresh-keeping device for combining radio frequency and visible light treatment. The inside of the fresh-keeping device is a cavity for storing fresh burdock roots, and it further includes a radio frequency module and an LED module. As Figure 7The figure shows a preferred embodiment of the preservation device of the present invention. The radio frequency module includes two substrates, and the distance between the two substrates is 40 cm. The LED module is arranged on the inner cavity side wall of the storage space between the plates and is composed of a plurality of LED lamp beads.

[0017] Principle of the invention: The present invention combines radio frequency technology with visible light treatment for the preservation of fresh burdock roots. Radio frequency treatment can promote the uniform distribution of intracellular water, improve the structure of the cell wall, make the cells of burdock more stable, thereby reducing water loss and delaying the migration of vacuolar water. The specific spectrum of the LED module can inhibit the growth of microorganisms, reduce oxidation reactions, and further improve the preservation effect of burdock. Through the combined action of radio frequency and visible light, especially blue light, the shelf life of burdock can be effectively extended, its freshness and hardness can be maintained, its post-harvest quality can be kept, the loss of nutrients can be reduced, and economic benefits can be improved.

[0018] Advantages: Compared with the prior art, the present invention has the following advantages: (1) Applying radio frequency technology and visible light in the post-harvest preservation of burdock can effectively maintain the freshness and quality of burdock within 10 days after harvest, while under conventional refrigeration conditions, the water loss of burdock is serious and the quality deteriorates significantly; (2) The treatment of the LED module avoids the use of chemical preservatives, reduces chemical residues, and ensures the safety of food; (3) The method of combining radio frequency and visible light is simple and efficient, and has extremely high practical value in the field of fresh Chinese herbal medicine preservation. Description of the drawings

[0019] Figure 1 It is a diagram of the change in the appearance color of fresh burdock during storage after radio frequency combined with visible light treatment;

[0020] Figure 2 It is a diagram of the overall sensory evaluation of fresh burdock during storage after radio frequency combined with visible light treatment;

[0021] Figure 3 It is a diagram of the weight loss change of fresh burdock during storage after radio frequency combined with visible light treatment;

[0022] Figure 4 It is a diagram of the hardness change of fresh burdock during storage after radio frequency combined with visible light treatment;

[0023] Figure 5 It is a diagram of the change in L of fresh burdock during storage after radio frequency combined with visible light treatment;

[0024] Figure 6 It is a diagram of the change in the a value of fresh burdock during storage after radio frequency combined with visible light treatment;

[0025] Figure 7 It is a schematic diagram of the internal structure of the preservation device for radio frequency combined with visible light treatment of the present invention. Detailed implementation mode

[0026] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings and embodiments. The test materials used in the embodiments can be obtained through conventional channels.

[0027] Example 1

[0028] For the fresh burdock preservation method based on radio frequency combined with visible light treatment, fresh burdock is selected as the experimental object; the specific operation steps are as follows:

[0029] (1) Wear wire gloves, handle gently, and select fresh burdock with good quality and no damage; clean the tray to be used and the treatment cavity of the radio frequency combined with LED lamp equipment, spray and disinfect with 75% ethanol, wipe, and open the treatment cavity door for ventilation. Gently place the selected burdock to be preserved on a ceramic tray lined with EPE pearl cotton.

[0030] (2) Disinfect the burdock with NaClO, with a concentration of 200 μL / L and a time of 5 min.

[0031] (3) Place the fresh burdock in the treatment cavity of the radio frequency combined with LED lamp equipment. The distance between the two electrodes of the equipment is 40 cm, the output frequency is 40.68 MHz, the radio frequency power is 3 kW, the blue light wavelength is 470 nm, and the irradiation intensity is 200 μmol m -2 s -1 , and at the same time process for 2 min, only process once and then store for 10 days; during the storage period, the temperature is kept at 15 °C and the relative humidity is 85%.

[0032] Example 2

[0033] Compared with Example 1, change the light source in step (3) of Example 1 to white light, with a white light wavelength of 450 nm - 700 nm:

[0034] (3) Place the fresh burdock in the treatment cavity of the radio frequency combined with LED lamp equipment. The distance between the two electrodes of the equipment is 40 cm, the output frequency is 40.68 MHz, the radio frequency power is 3 kW, and the white light intensity is 200 μmol m -2 s -1 , and at the same time process for 2 min.

[0035] Example 3

[0036] Compared with Example 3, change the light source in step (3) of Example 1 to red light, with a wavelength of 660 nm:

[0037] (3) Place the fresh burdock in the treatment cavity of the radio frequency combined with LED lamp equipment. The distance between the two electrodes of the equipment is 40 cm, the output frequency is 40.68 MHz, the radio frequency power is 3 kW, and the red light intensity is 200 μmol m -2 s -1 , and treat for 2 minutes simultaneously.

[0038] Comparative Example 1

[0039] Compared with Example 1, change the treatment method in step (3) of Example 1 to storing it in a constant temperature and humidity chamber at 15°C for 10 days.

[0040] (3) Store the burdock in a constant temperature and humidity chamber at 15°C for 10 days.

[0041] Comparative Example 2

[0042] Compared with Example 1, change the treatment method in step (3) of Example 1 to not using light treatment.

[0043] (3) Place the fresh burdock in the treatment cavity of the radio frequency combined with LED lamp equipment. The distance between the two electrodes of the equipment is 40 cm, the output frequency is 40.68 MHz, the radio frequency power is 0.5 - 3 kW, and treat for 2 minutes.

[0044] Comparative Example 3

[0045] Compared with Example 1, change the treatment method in step (3) of Example 1 to not using radio frequency treatment.

[0046] (3) Place the fresh burdock in the treatment cavity of the radio frequency combined with LED lamp equipment. The blue light intensity is 200 μmol m -2 s -1 , and treat for 2 minutes.

[0047] For the above examples and comparative examples, evaluate and test the fresh-keeping effects of burdock with different treatment methods. Sampling of each experimental example and comparative example is carried out at 0, 2, 4, 6, 8, and 10 days of storage to evaluate the change in the sensory quality of the fresh burdock after treatment, and measure the weight loss rate, burdock hardness, browning index, polyphenol oxidase (PPO) activity, and vitamin C content respectively.

[0048] Test Example 1: Appearance Evaluation

[0049] The influence of the radio frequency combined with LED lamp equipment on the appearance of fresh burdock during storage is as Figure 1As shown. During the experiment, no rotting occurred in the cut burdocks of the comparative examples and each example. The browning of the cut pieces was mainly manifested as irregular brown spots, with a lighter color in the initial stage. As the storage time extended, the brown color gradually deepened and the area expanded, ultimately leading to a serious decline in quality. From the color change of the fresh-cut burdock after 10 days of storage, it can be seen that the treatment effects of each example were significantly better than those of the comparative examples. Especially for Example 1, there was almost no color change in the cut pieces before and after treatment, and the effect was the best. However, obvious hollowness and cracking phenomena occurred in Comparative Examples 1 to 3, which preliminarily indicated that the fresh-keeping effect of only the radio frequency group plus only the light group was lower than the combined fresh-keeping effect of the two, indicating that radio frequency combined with LED lights has a synergistic fresh-keeping effect.

[0050] Test Example 2: Sensory quality evaluation

[0051] The influence of the radio frequency combined with LED light equipment on the overall sensory quality of fresh burdock is as Figure 2 shown. Compared with the comparative examples, the radio frequency combined with LED light treatment could better maintain the sensory quality of fresh burdock. In the early stage of storage in the comparative examples, the sensory quality decreased sharply, and the overall score dropped below 5 points when stored for 6 days, losing the sales value. After being stored for 10 days with the radio frequency combined with LED light treatment, the sensory evaluation score was still higher than 4 points. Compared with the comparative examples and other examples, the fresh-keeping effect after the treatment of Example 1 was better during storage, especially after the 6th day.

[0052] Test Example 3: Weight loss test

[0053] The influence of the radio frequency combined with LED light equipment on the weight loss of fresh burdock during storage is as Figure 3 shown. During storage, the weight of the burdock continued to decrease. When stored for the 10th day, the weight loss rate of Comparative Example 1 was 6.8%, that of Comparative Example 2 was 5.7%; the weight loss rate of Comparative Example 3 was 5.1%. The weight loss rates of Example 1, Example 2, and Example 3 were 4.5%, 5.2%, and 5.4% respectively. Among them, the weight loss rate of Example 1 was the lowest.

[0054] Test Example 4: Hardness test

[0055] The influence of the radio frequency combined with LED light equipment on the hardness of fresh burdock is as Figure 4 shown. The hardness of burdock is an important sensory index affecting its post-harvest quality. Due to the high water content of burdock and the relatively fragile cell wall structure, it is extremely easy to lose water and soften after harvest, resulting in a decrease in hardness. From Figure 4 it can be seen that after 2 days of storage, the hardness of the burdock in Comparative Examples 1, 2, and 3 rapidly decreased to 423.6 kg / cm 2 , 419.2 kg / cm 2 , 420.67 kg / cm 2, and it was significantly lower than that of each example until the end of storage. Compared with the initial value, the average hardness of burdock in each example and comparative example decreased by about 37% and 52% respectively on the 10th day. Among them, the hardness value of fresh burdock in Example 1 decreased less. The hardness decreased with the prolongation of storage time, but the treatment with radio frequency combined with LED lamp equipment significantly maintained the better hardness property of burdock, which indicates that radio frequency combined with LED lamp has a synergistic preservation effect, can effectively maintain the better tissue structure of burdock, and delay its postharvest water loss, softening and texture deterioration.

[0056] Test Example 5: Browning Index Test

[0057] The effect of radio frequency combined with LED lamp equipment on the browning of fresh burdock is as Figure 5 and Figure 6 shown. The L value represents brightness, and the lower the L value, the more serious the browning. Figure 5 It can be seen that in the initial stage of storage, the L values of each example treatment were lower than those of the comparative example to varying degrees, which indicates that the brightness of the cut surface decreased after treatment; when stored for 2 days, the two were close and the difference was not significant. After storing for 4 days, the L values of each example treatment generally decreased, but the L value of fresh burdock in the comparative example decreased more significantly, while the decrease in the example treatment was smaller. After storing for 6 days, the difference between the example and the comparative example was significant. After storing for 10 days, the L value of the comparative example was significantly lower than that at the start of storage, while the L values of each example were basically close and higher than those of the comparative example, indicating that radio frequency combined with LED lamp has a synergistic preservation effect. The chromatic aberration a represents the degree of red and green of the color. The higher the a value, the redder the color and the more serious the browning. From Figure 6 the change of the a value, the difference between the comparative example and each example was significant (P<0.05). The a value of the comparative example increased significantly with the storage time and basically remained unchanged after storing for 8 days. Each example increased slightly in the later stage of storage. Test Example 6: Determination of Polyphenol Oxidase (PPO) Activity

[0058] Polyphenol oxidase (PPO) is the core factor causing enzymatic browning of fruits and vegetables. Its catalytic oxidation reaction of phenolic substances will lead to the formation of browning products. To a certain extent, the activity of polyphenol oxidase can reflect the rate of browning product formation of fruits and vegetables, and thus reflect the freshness of fruits and vegetables.

[0059] Determination steps for polyphenol oxidase (PPO) activity: For each group, 40 g of insoluble PVPP was weighed into a 500 mL plastic test tube, and then 40 g of ground burdock powder was weighed into the test tube and stored at -80 °C for subsequent analysis. During analysis, 160 mL of pH 6.8 phosphate buffer was added to each test tube, homogenized, centrifuged at 10000 r / min for 20 min at 4 °C, and the supernatant was the crude enzyme solution. The reaction system for enzyme activity determination was configured as follows: In one tube, 2.5 mL of buffer solution, 0.5 mL of 0.02 mol / L catechol solution, and 0.1 mL of enzyme solution were added. As a control, 2.6 mL of buffer solution and 0.5 mL of 0.02 mol / L catechol solution were added without adding enzyme solution. After shaking well, the absorbance value was measured at 410 nm, recorded every 30 seconds for a total of 10 times, and each sample needed to be measured three times with two parallel samples for each repetition. The activity calculation method was: taking a change in absorbance value of 0.01 per minute as one enzyme activity unit; that is, the calculation formula was: PPO activity (U·g-1·min-1) = (A410nm * VT) / (0.01 * WF * VS * t), where A410nm represented the change in absorbance value; VT represented the total volume of the extraction solution (mL), WF represented the fresh weight (g); VS represented the volume of the enzyme solution used during measurement (mL).

[0060] The determination results are shown in Table 1. It can be seen that the sum of the reduction amplitudes of PPO enzyme activity of Comparative Example 2 and Comparative Example 3 relative to Comparative Example 1 is less than the reduction amplitude of PPO enzyme activity of Example 1 relative to Comparative Example 1, which indicates that the reduction effect of PPO enzyme activity of the radio frequency group alone plus the light group alone is much less than the combined effect of the two.

[0061] Test Example 7: Determination of vitamin C content

[0062] Burdock is rich in vitamin C, and its vitamin C content is higher than that of Chinese yam, which is one of the main nutritional components of burdock. During storage, the retention rate of its vitamin C content can reflect its fresh-keeping effect.

[0063] Determination steps for vitamin C content: 50 g of burdock powder from each group was placed in a 1000 mL volumetric flask, respectively, and extracted with 700 mL of 0.1 mol / L hydrochloric acid in boiling water for 30 min, and then made up to volume with dilute hydrochloric acid. A small amount of the upper-layer solution was centrifuged at high speed and filtered twice with a 0.22 μm filter membrane before use, and then the vitamin C of each group was measured by HPLC. HPLC conditions: Chromatographic column ODS-C18, mobile phase: A 1% acetic acid + acetonitrile (pH = 4.5); B A + methanol (50:50), gradient elution: 0 - 10 min, B from 0 → 80%, 10 - 25 min B was kept at 80%, flow rate was 1 mL / min, wavelength was 275 nm, and temperature was room temperature 25 °C.

[0064] The measurement results are shown in Table 1. It can be seen that the sum of the retention rates of vitamin C content in Comparative Example 2 and Comparative Example 3 relative to Comparative Example 1 is less than the retention rate of vitamin C content in Example 1 relative to Comparative Example 1. This indicates that the effect of retaining vitamin C content by simply superimposing the radio frequency group and the light irradiation group is far inferior to the combined effect of the two.

[0065] Table 1 is a collaborative data table of key indicators of fresh burdock during storage after treatment with radio frequency combined with LED lights.

[0066] Detection index Comparative example 1 Comparative example 2 Comparative example 3 Example 1 P value Browning index (ΔE) 11.2±0.5 5.8±0.2 8.1±0.4 5.0±0.2 ＜0.05 PPO enzyme activity (U / g) 10.0±0.3 8.4±0.5 7.6±0.2 2.5±0.2 ＜0.05 Retention rate of vitamin C (%) 42.7±0.4 53.1±0.6 61.2±0.2 87.6±0.3 ＜0.05

[0067] Based on the above effect evaluation and measurement, it can be concluded that the combined treatment of radio frequency and LED has a significant synergistic effect in burdock preservation.

Claims

1. A preservation method for burdock based on radio frequency combined with visible light processing, characterized in that, It includes the following steps: Clean and disinfect the inner cavities of the tray and the closed container for storage. Place the fresh burdock on the tray and then disinfect the burdock. After disinfection, place the tray and the fresh burdock together in the closed container. An RF module and an LED module are simultaneously provided in the closed container. During storage, the burdock is simultaneously subjected to a combined treatment of RF and visible light illumination using the RF module and the LED module, and the combined treatment is only carried out once during storage. The time for one combined treatment is 2 min.

2. The burdock preservation method according to claim 1, characterized in that, The fresh burdock is the burdock taproot with good quality, no cracks, no disease spots, no mechanical damage, no hollowness, not aged, and uniform thickness, which has been washed, had its fibrous roots removed, and been cut into sections.

3. The burdock fresh-keeping method according to claim 1, characterized in that, The disinfection of the burdock is carried out using an aqueous NaClO solution.

4. The burdock fresh-keeping method according to claim 3, wherein, The concentration of the aqueous NaClO solution is 200 μL / L, and the disinfection time is 5 min.

5. The burdock preservation method according to claim 1, wherein, The steps for cleaning and disinfecting the inner cavities of the tray and the closed container for storage are: first wipe with a clean wet towel and then spray 75% ethanol for disinfection.

6. The burdock fresh-keeping method according to claim 1, wherein, The RF output frequency of the RF module is 40.68 MHz, and the RF power is 0.5 - 3 kW.

7. The burdock fresh-keeping method according to claim 1, characterized in that, The light intensity of the LED module is 200 μmol m -2 s -1 , and the LED module emits white light, red light or blue light.

8. The burdock fresh-keeping method according to claim 1, wherein, The storage period includes the period of combined treatment, and the temperature conditions during the storage period are all 15 - 40 °C, and the relative humidity is all 85%.

9. The burdock preservation method according to claim 1, characterized in that, The distance between the two electrodes of the RF module is 40 cm, and the capacitance rises by 50 mm.

10. A radio frequency combined with visible light processing fresh-keeping device, characterized in that, The interior of the fresh-keeping device is a cavity for storing fresh burdock roots, and the fresh-keeping device further includes the RF module and the LED module described in claim 1.

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