Method for improving quality of postharvest tomato fruits by utilizing light in cooperation with exogenous electric field

Abstract

The invention belongs to the technical field of fruit and vegetable fresh-keeping storage, and discloses a method for improving the quality of picked tomato fruits by using light in cooperation with an exogenous electric field, and the method comprises the following steps: disinfecting freshly picked tomato fruits, and disinfecting a container and a device for placing the tomato fruits; the disinfected tomato fruits are placed in a closed device to be stored, periodical regulation and control treatment is carried out in the storage period and in the storage space, and the periodical regulation and control treatment means that a low-frequency polarization electric field and blue light irradiation are applied to the tomato fruits at the same time according to the fixed interval time. According to the method, the biological rhythm of the tomatoes is regulated and controlled through cooperation of blue light and the electric field, senescence of the picked tomatoes can be delayed, so that the fresh-keeping period of the tomatoes is prolonged, and meanwhile the nutritional quality of the tomatoes, especially the nutritional ingredient lycopene, can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of fresh-keeping storage of fruits and vegetables, and particularly relates to a method for improving the quality of postharvest tomato fruits by using light in cooperation with an external electric field. Background Technique

[0002] The postharvest ripening process of tomato fruits is regulated by environmental factors such as temperature, humidity, and light, which directly affect respiratory metabolism, ethylene release, and cell homeostasis, resulting in nutrient loss and quality deterioration. Among the existing regulation means, it has been reported that LED light treatment can activate the light signal pathway and regulate the synthesis of pigment substances in fruits and vegetables; however, the ability of a single light source treatment to maintain the postharvest quality of fruits and vegetables is limited. The intervention of an external physical field can regulate the postharvest ripening and senescence of fruits and vegetables by changing the transmembrane potential and inhibiting the activity of the key enzyme for ethylene synthesis, but its induction efficiency for the pigment synthesis pathway is insufficient. Currently, most of the similar technologies adopt single light treatment or physical field treatment. For example, although light treatment can induce the synthesis of lycopene precursors, it is accompanied by a sharp increase in the amount of ethylene synthesis, accelerating fruit softening; while electric field treatment can effectively delay the degree of membrane lipid peroxidation, but has no significant effect on the improvement of nutritional qualities such as lycopene and anthocyanin. It is worth noting that lycopene, as the member with the strongest antioxidant activity in the carotenoid family, its long-chain polyunsaturated olefin molecular structure endows it with super strong free radical scavenging ability (100 times higher than vitamin E). Clinical data of the American Cancer Institute show that daily intake of 15 mg of lycopene can significantly reduce the risk of cardiovascular diseases by 26%, and inhibit DNA oxidative damage by quenching singlet oxygen, reducing the incidence of epithelial tumors such as breast cancer and prostate cancer. This characteristic with both nutritional and pharmacological values makes it have important development potential in the fields of functional foods and dietary supplements. Therefore, it is urgent to develop a new type of cooperative regulation technology to directionally activate the accumulation of nutrients such as lycopene while maintaining the storage quality of fruits. By establishing a new model of the coupling effect between the light field and the electric field, it is expected to break through the limitations of the single field effect on the regulation of the metabolic network and achieve a synergistic gain effect of 1 + 1 > 2, which has important industrial significance for improving the added value of postharvest treatment technology. Summary of the Invention

[0003] Object of the Invention: The object of the present invention is to provide a safe, efficient, and precise method for using photoelectric cooperation to regulate the storage quality of postharvest tomato fruits and improve the enrichment of nutrients such as lycopene to improve their nutritional quality.

[0004] Technical Solution: The present invention discloses a method for improving the quality of postharvest tomato fruits by using light in cooperation with an external electric field. It should be noted that the light in the present invention refers to blue light, and the external electric field refers to a low-frequency polarization electric field. Therefore, the method for improving the quality of postharvest tomato fruits by using light in cooperation with an external electric field is to simultaneously treat the picked tomato fruits with blue light and an applied low-frequency polarization electric field.

[0005] The method for improving the quality of postharvest tomato fruits by using light in cooperation with an external electric field includes the following steps:

[0006] Disinfect the freshly picked tomato fruits, and disinfect the containers and devices for placing the tomato fruits; place the disinfected tomato fruits in a closed device for storage, and perform periodic regulation treatment during the storage period and in the storage space. The periodic regulation treatment refers to simultaneously applying a low-frequency polarized electric field and blue light irradiation to the tomato fruits at fixed intervals;

[0007] Preferably, the freshly picked tomato fruits are tomato fruits without mechanical damage, diseases and pests, and with uniform size;

[0008] Preferably, the specific operation of the disinfection is to gently wipe with 75% ethanol for disinfection;

[0009] Preferably, the output voltage of the low-frequency polarized electric field is 2500 - 3000V, the current is 1 - 5mA, and the frequency is 50 - 60Hz; further preferably, the tomato fruits are placed at a position about 10 - 15 cm away from the electric field plate, and the field strength is about 20 - 30 kV / m;

[0010] Preferably, the wavelength range of the blue light irradiation is 460nm - 480nm, and the light density range of the blue light irradiation is 200 - 300 μmol m 2 s - 1;

[0011] Preferably, the low-frequency polarized electric field and the blue light irradiation are carried out simultaneously, and the treatment time is 3 hours continuously at a fixed time period every day;

[0012] Preferably, the temperature conditions during the storage period including the periodic regulation treatment are all 12℃ - 15℃, and the relative humidity is 80% - 85%.

[0013] Principle of the invention: The biological clock of tomatoes can sense and respond to external light signals, regulate its own physiological rhythm, and thus affect its own metabolism and the accumulation of secondary metabolites. Compared with other spectral regions, blue light is more easily absorbed by photosynthetic pigments and can enhance the secondary metabolites in tomatoes. The electric field regulates the expression pattern of the core genes of the biological clock by affecting the signal transduction pathway related to the biological clock, thereby achieving precise regulation of the nutritional quality of postharvest tomato fruits. In the present invention, the biological rhythm of tomatoes is regulated by the cooperation of blue light and the electric field, and it is found that the cooperation of the two can delay the senescence of postharvest tomato fruits, thereby extending the shelf life of tomato fruits. At the same time, it can also improve the nutritional quality of tomato fruits, especially the nutritional component lycopene.

[0014] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages: (1) By the synergistic action of light and electric field, the biological clock of postharvest tomato fruits is regulated, the ripening and senescence of tomato fruits are significantly delayed, the loss of nutrients is effectively reduced, the quality of postharvest tomatoes is maintained, and their shelf life is extended. (2) The present invention adopts physical regulation, which is green, safe and pollution-free, and the regulation method has low cost and can be widely promoted on a large scale. Brief Description of the Drawings

[0015] Figure 1 It is a graph showing the change of weight loss rate of tomato fruits during 28 days of storage in the examples and comparative examples;

[0016] Figure 2 It is a graph showing the change of soluble solid content of tomato fruits during 28 days of storage in the examples and comparative examples;

[0017] Figure 3 It is a graph showing the change of lycopene content of tomato fruits during 28 days of storage in the examples and comparative examples;

[0018] Figure 4 It is a graph showing the change of anthocyanin content of tomato fruits during 28 days of storage in the examples and comparative examples;

[0019] Figure 5 It is a physical picture of tomato fruits after 28 days of storage in Example 1.

[0020] Figure 6 It is a physical picture of tomato fruits after 28 days of storage in Example 2;

[0021] Figure 7 It is a physical picture of tomato fruits after 28 days of storage in Comparative Example 1;

[0022] Figure 8 It is a physical picture of tomato fruits after 28 days of storage in Comparative Example 2;

[0023] Figure 9 It is a physical picture of tomato fruits after 28 days of storage in Comparative Example 3. Detailed Embodiments

[0024] The technical solution of the present invention will be further described below in conjunction with the examples. The test materials used in the examples can be obtained through conventional channels.

[0025] Example 1 Light Synergy Electric Field Treatment Group

[0026] The method for improving the quality of postharvest tomatoes by light synergy with external electric field in the present invention:

[0027] (1) Wear gloves, handle gently, select tomato fruits picked in the same batch, without mechanical damage and pests and diseases. Gently wipe the fruits with 75% ethanol for disinfection, and scrub and disinfect the trays and equipment for placing the fruits. Place the fruits on the trays.

[0028] (2) Place the tomatoes in a collaborative fresh-keeping device equipped with LED lights and an electric field. The output voltage of the low-frequency polarization electric field is 3000 V, the current is 5 mA, and the frequency is 50 Hz. The tomato fruits are placed at a position about 10 cm away from the electric field plate, and the electric field strength is about 30 kV / m. Set the LED light illumination color to blue, and the illumination intensity is 250 μmol m 2 s - 1. The electric field and light are co-treated for 28 days. The treatment time period every day is 08:00 - 11:00, and the storage temperature in the fresh-keeping device is 15 °C, and the relative humidity is 85%. During the 28 days of storage, samples are taken every 7 days to observe the changes in fruit quality and other index determinations.

[0029] Example 2 Light-Coordinated Electric Field Treatment Group

[0030] The difference between Example 2 and Example 1 is only that the output voltage of the low-frequency polarization electric field is 2500 V, and the rest of the operations and parameters are the same.

[0031] Control Example 1 Single Blue Light Treatment Group

[0032] Compared with Example 1, change step (2) in Example 1 to not perform electric field treatment, and the rest of the operations are the same as in Example 1.

[0033] Control Example 2 Single Low-Frequency Polarization Electric Field Treatment

[0034] Compared with Example 1, change step (2) in Example 1 to not perform light treatment, and the rest of the operations are the same as in Example 1.

[0035] Control Example 3 Blank Treatment Group

[0036] Compared with Example 1, change step (2) in Example 1 to not perform light treatment and not perform electric field treatment, and the rest of the operations are the same as in Example 1.

[0037] For the tomato fruits treated in different ways in the above examples and control examples, study the quality. At the same time, samples are taken at 0, 7, 14, 21, and 28 d of storage, and the changes in the weight loss rate, soluble solid content, lycopene content, and anthocyanin content of the tomato fruits are respectively tested. The test data results are shown in Figures 1 to 4 .

[0038] Weigh the tomato fruits on the 0th, 7th, 14th, 21st, and 28th days. Calculate the weight loss rate of the tomato fruits according to the following formula (1). In formula (1), w0 represents the weight of the tomato fruits on the 0th day, in grams (g), and w n represents the weight of the tomato fruits on the nth day, in grams (g):

[0039]

[0040] As Figure 1 is the calculation result of the weight loss rate of the tomato fruits. It can be seen that during the storage period from 0 to 28 days, the fruit weight continued to decrease. Although the single blue light treatment and the low-frequency polarization electric field treatment reduced the weight loss rate of the tomato fruits to a certain extent, the effect was far less than the synergistic treatment of blue light and low-frequency polarization electric field on the tomato fruits. On the 28th day of storage, the weight loss rate of the tomato fruits in the synergistic treatment group of blue light and low-frequency polarization electric field in Example 1 and Example 2 of the present invention was half of that of the blank treatment group, effectively reducing the loss of water and nutrients, maintaining the quality of postharvest tomatoes, and extending their shelf life. However, there was no significant difference between Example 1 and Example 2. As Figure 5 , Figure 6 , Figure 7 , Figure 8 and Figure 9 show the physical photos of the tomato fruits in Example 1-2 and Comparative Example 1-3 after 28 days of storage. It can be clearly seen that the quality of the tomato fruits in Example 1-2 is significantly better than that of the tomato fruits in Comparative Example 1-3.

[0041] Grind and crush a part of the sampled tomato fruit samples in a mortar. After squeezing out the juice with a gauze, use a portable digital sugar meter to measure, and the result is expressed as a mass fraction (%). As Figure 2 is the measurement result of the soluble solids content of the tomato fruits. It can be seen that in Example 1 and Example 2 of the present invention, the synergistic treatment group of blue light and low-frequency polarization electric field effectively maintained the soluble solids content in the tomato fruits, reduced the loss of nutrients, and maintained the quality of the tomato fruits compared with the single blue light or electric field treatment group and the blank treatment group.

[0042] Crush a part of the above sampled tomatoes and extract them with acetone. After filtering through a 0.45 μm filter membrane, inject them into a high performance liquid chromatograph. Use a C18 chromatographic column, and the mobile phase is; Mobile phase A is a mixed solution of acetonitrile: methanol: ethyl acetate (70:10:9), the flow rate is 1 mL / min, the detection wavelength is 472 nm, and the external standard method is used for quantification. As Figure 3It is the measurement result of lycopene content in tomato fruit. It can be seen that the lycopene content in the light-synergistic electric field treatment group is much higher than that in comparative examples 1 to 3, and it can be seen from the measurement results on the 14th, 21st and 28th days that the increased content in Example 1 relative to comparative example 3, i.e. the blank treatment group, is higher than the sum of the increased contents in comparative example 1 and comparative example 2 relative to comparative example 3, which proves that the blue light and low-frequency polarized electric field synergistic treatment method of the present invention has an extremely significant effect on the enrichment of lycopene in postharvest tomatoes, can effectively enrich lycopene, and improve the nutritional value and economic value of postharvest tomatoes.

[0043] Take 0.2 g of the pulp of the tomato fruit sampled above and grind it into powder with liquid nitrogen, then add 600 μL of methanol solution containing 1% hydrochloric acid, and soak the mixture in the dark at 4°C overnight. Subsequently, add 400 μL of chloroform and 400 μL of water in turn, vortex mix thoroughly, and centrifuge at 4°C and 10000xg for 5 minutes. Then, measure the absorbance value at wavelengths of 530nm and 657nm. The anthocyanin content is calculated according to the value of A530-0.33*A657 per gram of fresh weight. Figure 4 The results of the determination of anthocyanin content in tomato fruit are as follows: the synergistic treatment of blue light and low-frequency polarized electric field in Examples 1 and 2 of the present invention has significant effects on the accumulation of anthocyanins in tomato fruit compared with Comparative Examples 1 to 3. Therefore, the light-synergistic electric field treatment of the present invention can increase the anthocyanin content in tomatoes, thereby improving the quality of tomato fruit.

Claims

1. A method for improving the quality of postharvest tomato fruits by using light in cooperation with an external electric field, characterized in that, The method includes the steps of: disinfecting freshly picked tomato fruits, and disinfecting the containers and devices for placing the tomato fruits; placing the disinfected tomato fruits in a closed device for storage, and performing periodic regulation treatment during the storage period and in the storage space, where the periodic regulation treatment refers to simultaneously applying a low-frequency polarized electric field and blue light irradiation to the tomato fruits at fixed time intervals.

2. The method for improving the quality of postharvest tomato fruits by using light in cooperation with an external electric field according to claim 1, characterized in that The freshly picked tomato fruits are tomato fruits without mechanical damage, pests and diseases, and of uniform size.

3. The method for improving the quality of postharvest tomato fruits by using light in cooperation with an external electric field according to claim 1, wherein, The specific operation of the disinfection is to gently wipe with 75% ethanol for disinfection.

4. The method for improving the quality of postharvest tomato fruits by using light in cooperation with an external electric field according to claim 1, wherein, The output voltage of the low-frequency polarized electric field is 2500 - 3000V, the current is 1 - 5mA, and the frequency is 50 - 60Hz.

5. The method for improving the quality of postharvest tomato fruits by using light in cooperation with an external electric field according to claim 4, characterized in that, The tomato fruits are placed at a position about 10 - 15 cm away from the electric field plate, and the field strength is about 20 - 30 kV / m.

6. The method for improving the quality of postharvest tomato fruits by using light in cooperation with an external electric field as claimed in claim 1, wherein The wavelength range of the blue light irradiation is 460 nm to 480 nm, and the light density range of the blue light irradiation is 200 to 300 μmol m 2 s - 1 7. A method for improving the quality of postharvest tomato fruits by using light in cooperation with an external electric field according to claim 1, characterized in that, The low-frequency polarized electric field and the blue light irradiation treatment are carried out simultaneously, and the treatment time is 3h continuously in a fixed time period every day.

8. A method for improving the quality of postharvest tomato fruits by using light in cooperation with an external electric field as claimed in claim 1, characterized in that The temperature conditions during the storage period including the periodic regulation treatment are all 12°C - 15°C, and the relative humidity is 80% - 85%.

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