A method for maintaining the green color of prefabricated vegetables

Abstract

The present invention discloses a method for maintaining the green color of prefabricated vegetables, belonging to the technical field of prefabricated vegetable processing. The method for maintaining the green color of prefabricated vegetables includes: soaking in a specific color protection solution, soaking in a specific color protection solution under low-pressure conditions, microwave treatment, pulsed electric field treatment or alternating magnetic field treatment. Each process method can be used alone or in combination. Based on the existing production process of prefabricated vegetables, after the vegetables are cut and disinfected, a pretreatment step of the vegetable raw materials is added, and the subsequent production process remains unchanged, which can maintain the green color of the vegetables without obvious change. Through the pretreatment process disclosed by the present invention, the stability of chlorophyll in green vegetables can be significantly improved, and the improvement effect of chlorophyll stability is better after different processes are combined.

Description

Technical Field

[0001] The present invention belongs to the technical field of processed prefabricated vegetables, and particularly relates to a method for maintaining the green color of prefabricated vegetables. Background Art

[0002] Prefabricated dishes are fast-moving consumer goods obtained by using modern standardized assembly-line operations to perform preliminary preparation work on dish raw materials and through industrial processing and packaging processes. Consumers only need to simply heat or stir-fry these products to eat, providing consumers with a delicious, safe, healthy, and fast way of eating. Currently, prefabricated dishes have been widely used in large catering enterprises, large event catering, enterprise and institution canteens, school canteens and other units, and have received favorable comments from consumers. However, for the vegetables in prefabricated dishes, especially green vegetables rich in chlorophyll, after being cut, heated, blended, stirred, frozen / refrigerated, and thawed, their chlorophyll will degrade and turn into yellow-brown, resulting in color deterioration of the products and seriously affecting the commerciality of the products. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for maintaining the green color of prefabricated vegetables. After preprocessing vegetables, especially green vegetables rich in chlorophyll, using this method and then continuing with the current prefabricated dish production process, the color of green vegetables can be maintained, the commerciality of the products can be improved, and the shelf life of the products can be extended.

[0004] To achieve the above purpose, the present invention provides the following technical solutions:

[0005] One of the technical solutions of the present invention: Provide a method for maintaining the green color of prefabricated vegetables, including Method 1 or Method 2.

[0006] Method 1 includes the following steps:

[0007] Immerse the green vegetables in a color protection solution, wash them, and then dehydrate the surface for standby.

[0008] Method 2 includes the following steps:

[0009] Place the green vegetables in a pressure-adjustable device filled with a color protection solution. First, reduce the pressure to 0.001 - 0.008 MPa and maintain it for 10 - 45 minutes, then restore it to normal pressure, repeat the cycle twice, wash them, and then dehydrate the surface for standby.

[0010] The color protection liquid includes color protection liquid A or color protection liquid B. Among them, the components of color protection liquid A include ascorbic acid 0.1 - 1.2 wt.%, ethanol 0 - 10 wt.%, ethylenediaminetetraacetic acid 0.1 - 1.5 wt.%, calcium ascorbate 0.0005 - 0.05 wt.%, magnesium chloride 0 - 0.005 wt.%, potassium citrate 0 - 0.08 wt.%, and sodium alginate 0 - 0.05 wt.%; the components of color protection liquid B include sodium alginate 0.01 - 0.05 wt.%, sodium ascorbate 0.01 - 0.2 wt.%, calcium ascorbate 0.005 - 0.05 wt.%, L - malic acid 0 - 0.01 wt.%, phytic acid 0 - 0.02 wt.%, guar gum 0.02 - 0.1 wt.%, pectin 0.005 - 0.15 wt.%, xanthan gum 0 - 0.2 wt.%, carrageenan 0.02 - 0.1 wt.%, sodium chloride 0 - 0.7 wt.%, α - cyclodextrin 0.05 - 0.5 wt.%, and sodium bicarbonate 0.05 - 1.5 wt.%.

[0011] Preferably, color protection liquid A is a solution containing ascorbic acid 0.5 wt.%, ethanol 5 wt.%, ethylenediaminetetraacetic acid 0.3 wt.%, calcium ascorbate 0.03 wt.%, magnesium chloride 0.002 wt.%, potassium citrate 0.03 wt.%, and sodium alginate 0.02 wt.%; color protection liquid B is a solution containing sodium alginate 0.03 wt.%, sodium ascorbate 0.1 wt.%, calcium ascorbate 0.04 wt.%, L - malic acid 0.01 wt.%, phytic acid 0.01 wt.%, guar gum 0.1 wt.%, pectin 0.1 wt.%, xanthan gum 0.1 wt.%, carrageenan 0.05 wt.%, sodium chloride 0.35 wt.%, α - cyclodextrin 0.36 wt.%, and sodium bicarbonate 0.35 wt.%.

[0012] The green vegetables in the present invention refer to vegetables containing chlorophyll and partially or entirely green in appearance.

[0013] Preferably, the step after surface dehydration in Method 1 or Method 2 further includes a microwave treatment step.

[0014] More preferably, the microwave treatment is specifically: subjecting the surface - dehydrated green vegetables to a microwave treatment of 0.5 - 3.5 kW / kg, with the microwave wavelength of 122 mm, frequency of 2450 MHz, and treatment time of 1 - 8 min.

[0015] Preferably, the step after surface dehydration in Method 1 or Method 2 further includes a pulsed - electric - field treatment step.

[0016] More preferably, the pulsed electric field treatment is specifically as follows: subject the surface-dehydrated green vegetables to a pulsed electric field treatment with an intensity of 2-40 kV / m, a frequency of 34-100 Hz, a square wave with a waveform of 1-6:1, and a treatment time of 1-180 min.

[0017] Preferably, the step of surface dehydration in Method 1 or Method 2 further includes an alternating magnetic field treatment step.

[0018] More preferably, the alternating magnetic field treatment is specifically as follows: subject the surface-dehydrated green vegetables to a magnetic field treatment with an intensity of 10-150 T / m, a frequency of 10-100 Hz, a sine wave waveform, and a treatment time of 60-180 min.

[0019] Preferably, the temperature of the color protection liquid in Method 1 is 50-65 °C, and the soaking time of the green vegetables in the color protection liquid is 10-25 min.

[0020] Preferably, the time for the pressure to drop to the set value in Method 2 is 30 min.

[0021] The color protection principles of each process step of the present invention are as follows:

[0022] Soaking in color protection liquid: Chlorophyll is sensitive to factors such as the pH of the environment, metal ions, and oxygen content. The color protection liquid adjusts factors such as the pH of the environment, metal ions, and oxygen content, thereby improving the stability of chlorophyll.

[0023] Low-pressure soaking: Chlorophyll is relatively evenly distributed in the pulp of green vegetables. Adjusting the internal and external environments of the green vegetable pulp to be consistent, so that chlorophyll is in an appropriate environment of pH, metal ions, and oxygen content, can improve the stability of chlorophyll. Low-pressure soaking can penetrate the color protection liquid into the pulp faster, thereby maintaining the consistency of the internal and external environments of the green vegetable pulp, and thus improving the stability of chlorophyll.

[0024] Microwave treatment: Microwave treatment can change the molecular conformation of chlorophyll degrading enzymes and inactivate the activity of chlorophyll degrading enzymes, thereby improving the stability of chlorophyll.

[0025] Pulsed electric field treatment: Pulsed electric field treatment changes the microscopic structure of green vegetable cells, improves the permeability inside the pulp, promotes the penetration of the color protection liquid, and the color protection liquid improves the stability of chlorophyll, thereby improving the stability of chlorophyll; on the other hand, pulsed electric field treatment inactivates the key enzymes of green vegetable physiological metabolism, delays the aging process of green vegetables, and improves the stability of chlorophyll.

[0026] Alternating magnetic field treatment: Alternating magnetic field treatment affects the vibration frequency of water molecules inside the pulp, activates the superoxide radical metabolism process of green vegetables, improves the antioxidant capacity of vegetables, reduces the attack of superoxide radicals on chlorophyll molecules, and thus improves the stability of chlorophyll.

[0027] The beneficial technical effects of the present invention are as follows:

[0028] Based on the existing production process of prefabricated dishes, after the vegetables are cut and disinfected, a pretreatment step for vegetable raw materials is added, and the subsequent production process remains unchanged, which can maintain the green color of the vegetables without obvious change.

[0029] Through the pretreatment process disclosed in the present invention, the stability of chlorophyll in green vegetables can be significantly improved, and the improvement effect of chlorophyll stability is better after combining different processes. Brief Description of the Drawings

[0030] Figure 1 Shows the influence of different pretreatment processes on the chlorophyll residue rate in scrambled eggs with broccoli. Detailed Description of the Invention

[0031] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention. It should be understood that the terms used in the present invention are only for describing specific embodiments and are not used to limit the present invention.

[0032] In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0033] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention.

[0034] Regarding the terms "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0035] Taking scrambled eggs with broccoli as an example, the embodiments of the present application studied the influence of different pretreatment processes on the stability of chlorophyll in broccoli, and the results are shown in Figure 1, the higher the chlorophyll retention rate, the better the green protection effect of the pretreatment process. Conversely, the green color of the product will turn into yellowish-brown.

[0036] Example 1

[0037] Process 1, soaking in color protection liquid:

[0038] After shaping, cutting, disinfecting, and surface dehydration of fresh broccoli, transfer it to a turnover basket with holes around. Cover the turnover basket and immerse it in the color protection liquid at 55 °C for 15 minutes. The color protection liquid contains 0.5 wt.% ascorbic acid, 5 wt.% ethanol, 0.3 wt.% ethylenediaminetetraacetic acid, 0.03 wt.% calcium ascorbate, 0.002 wt.% magnesium chloride, 0.03 wt.% potassium citrate, and 0.02 wt.% sodium alginate. After treatment, rinse with pure water at 4 °C, and the mass of the pure water is 8 times that of the broccoli. Then, dehydrate the surface of the product, transfer it to the turnover basket after surface dehydration, and quickly transfer it to a transfer warehouse at 4 °C for standby. After storing for 12 h, place the refrigerated product in boiling water for 6.5 min, and then stir-fry it with egg liquid. The mass ratio of broccoli to egg liquid is 5:1. During the stir-frying process, based on the mass of broccoli, add 1.3% edible salt, 1.6% chicken essence, 2.0% oyster sauce, and 2.5% light soy sauce, and the stir-frying time is 8 min. Then, quickly cool the stir-fried broccoli and eggs to 0 °C, randomly pick about 50 g of broccoli from it, and measure the chlorophyll content in it. And take the proportion of the chlorophyll content in the stir-fried sample in the chlorophyll content of fresh broccoli as the chlorophyll retention rate of the sample. The results are shown in Figure 1 .

[0039] Example 2

[0040] Process 2, low-pressure soaking:

[0041] The fresh broccoli is shaped, cut, disinfected, surface dehydrated and then transferred to a vacuum tank, immersed in a color protection solution, with the loading amount being 45% of the volume of the vacuum tank. The pressure of the vacuum tank is reduced to 0.005 MPa, and the pressure reduction time is 30 min. The pressure is maintained for 30 min and then quickly restored to normal pressure. The color protection solution contains 0.03 wt.% sodium alginate, 0.1 wt.% sodium ascorbate, 0.04 wt.% calcium ascorbate, 0.01 wt.% L-malic acid, 0.01 wt.% phytic acid, 0.1 wt.% guar gum, 0.1 wt.% pectin, 0.1 wt.% xanthan gum, 0.05 wt.% carrageenan, 0.35 wt.% sodium chloride, 0.36 wt.% α-cyclodextrin and 0.35 wt.% sodium bicarbonate; the above procedure is repeated 2 times. After treatment, it is rinsed with pure water at 4°C, and the mass of the pure water is 8 times that of the broccoli. Then it is placed in a turnover basket and left to drain in a 4°C environment. Then the surface of the product is surface dehydrated, and after surface dehydration, it is transferred to a turnover basket and then transferred to a 4°C turnover storage for standby. After storage for 12 h, the refrigerated product is placed in boiling water for 6.5 min and then stir-fried with egg liquid. The mass ratio of broccoli to egg liquid is 5:1. During the stir-frying process, based on the mass of the broccoli, 1.3% edible salt, 1.6% chicken essence, 2.0% oyster sauce and 2.5% light soy sauce are added, and the stir-frying time is 8 min. Then, the stir-fried broccoli and eggs are quickly cooled to 0°C, and about 50 g of broccoli is randomly picked out and the chlorophyll content in it is measured. And the ratio of the chlorophyll content in the stir-fried sample to the chlorophyll content in the fresh broccoli is used as the chlorophyll residue rate in the sample. The results are shown in Figure 1 .

[0042] Example 3

[0043] Process 3, microwave treatment:

[0044] The fresh broccoli is shaped, cut, disinfected, surface dehydrated and then transferred into a turnover basket. The turnover basket is transferred into a microwave treatment chamber, and microwave treatment is given at 2.0 kW / kg. The wavelength of the microwave is 122 mm and the frequency is 2450 MHz, and the treatment time is 3 min. Then the turnover basket is transferred to a 4°C turnover storage for standby. After storage for 12 h, the refrigerated product is placed in boiling water for 6.5 min and then stir-fried with egg liquid. The mass ratio of broccoli to egg liquid is 5:1. During the stir-frying process, based on the mass of the broccoli, 1.3% edible salt, 1.6% chicken essence, 2.0% oyster sauce and 2.5% light soy sauce are added, and the stir-frying time is 8 min. Then, the stir-fried broccoli and eggs are quickly cooled to 0°C, and about 50 g of broccoli is randomly picked out and the chlorophyll content in it is measured. And the ratio of the chlorophyll content in the stir-fried sample to the chlorophyll content in the fresh broccoli is used as the chlorophyll residue rate in the sample. The results are shown in Figure 1 .

[0045] Example 4

[0046] Process 4, pulsed electric field treatment:

[0047] After shaping, cutting, disinfecting, and surface dehydration of fresh broccoli, transfer it into a turnover basket. Transfer the turnover basket into the pulsed electric field treatment chamber, and apply a pulsed electric field treatment of 10 kV / m. The frequency of the electric field is 45 Hz, the waveform is a square wave with a ratio of 3:1, and the treatment time is 20 min. Then transfer the product turnover basket to a 4°C turnover storage for standby. After storage for 12 h, place the refrigerated product in boiling water for 6.5 min, and then stir-fry it with egg liquid. The mass ratio of broccoli to eggs is 5:1. During the stir-frying process, based on the mass of broccoli, add 1.3% edible salt, 1.6% chicken essence, 2.0% oyster sauce, and 2.5% light soy sauce, and the stir-frying time is 8 min. Then, quickly cool the stir-fried broccoli and eggs to 0°C, randomly pick about 50 g of broccoli from it, and measure the chlorophyll content. And take the ratio of the chlorophyll content in the stir-fried sample to the chlorophyll content in fresh broccoli as the chlorophyll residue rate in the sample. The results are shown in Figure 1 。

[0048] Example 5

[0049] Process 5, alternating magnetic field treatment:

[0050] After shaping, cutting, disinfecting, and surface dehydration of fresh broccoli, transfer the product into a turnover basket. Transfer the turnover basket into the alternating magnetic field treatment chamber, and apply a magnetic field treatment of 100 T / m. The frequency of the magnetic field is 66 Hz, the waveform is a sine wave, and the treatment time is 60 min. Then transfer the product turnover basket to a 4°C turnover storage for standby. After storage for 12 h, place the refrigerated product in boiling water for 6.5 min, and then stir-fry it with egg liquid. The mass ratio of broccoli to egg liquid is 5:1. During the stir-frying process, based on the mass of broccoli, add 1.3% edible salt, 1.6% chicken essence, 2.0% oyster sauce, and 2.5% light soy sauce, and the stir-frying time is 8 min. Then, quickly cool the stir-fried broccoli and eggs to 0°C, randomly pick about 50 g of broccoli from it, and measure the chlorophyll content. And take the ratio of the chlorophyll content in the stir-fried sample to the chlorophyll content in fresh broccoli as the chlorophyll residue rate in the sample. The results are shown in Figure 1 。

[0051] Example 6

[0052] Process 1 + 3, soaking in color protection solution + microwave treatment:

[0053] The fresh broccoli is shaped, cut, disinfected, surface dehydrated and then transferred to a turnover basket. The turnover basket is capped and immersed in a color protection solution at 55 °C for 15 minutes. The color protection solution contains 0.5 wt.% ascorbic acid, 5 wt.% ethanol, 0.3 wt.% ethylenediaminetetraacetic acid, 0.03 wt.% calcium ascorbate, 0.002 wt.% magnesium chloride, 0.03 wt.% potassium citrate and 0.02 wt.% sodium alginate. After treatment, it is rinsed with purified water at 4 °C, and the mass of the purified water is 8 times that of the broccoli. Then the surface of the product is surface dehydrated, and after surface dehydration, it is transferred to a turnover basket. The turnover basket is transferred to a microwave treatment chamber and given a microwave treatment of 2.0 kW / kg. The wavelength of the microwave is 122 mm and the frequency is 2450 MHz, and the treatment time is 3 min. Then the turnover basket is transferred to a 4 °C turnover storage for standby. After storage for 12 h, the refrigerated product is placed in boiling water for 6.5 min, and then stir-fried with egg liquid. The mass ratio of broccoli to egg liquid is 5:1. During the stir-frying process, based on the mass of the broccoli, 1.3% edible salt, 1.6% chicken essence, 2.0% oyster sauce and 2.5% light soy sauce are added, and the stir-frying time is 8 min. Then, the stir-fried broccoli and eggs are quickly cooled to 0 °C, and about 50 g of the broccoli is randomly picked to measure the chlorophyll content therein. And taking the proportion of the chlorophyll content in the stir-fried sample to the chlorophyll content in the fresh broccoli as the chlorophyll residue rate in the sample, the results are shown in Figure 1 .

[0054] Example 7

[0055] Process 1 + 4, color protection solution immersion + pulsed electric field treatment:

[0056] The fresh broccoli is shaped, cut, disinfected, surface dehydrated and then transferred to a turnover basket. The turnover basket is covered and immersed in a color protection solution at 55°C for 15 minutes. The color protection solution contains 0.5 wt.% ascorbic acid, 5 wt.% ethanol, 0.3 wt.% ethylenediaminetetraacetic acid, 0.03 wt.% calcium ascorbate, 0.002 wt.% magnesium chloride, 0.03 wt.% potassium citrate and 0.02 wt.% sodium alginate. After treatment, it is rinsed with pure water at 4°C, and the mass of the pure water is 8 times that of the broccoli. Then the surface of the product is surface dehydrated. After surface dehydration, it is transferred to a turnover basket, and the turnover basket is transferred to a pulsed electric field treatment chamber for pulsed electric field treatment at 10 kV / m. The frequency of the electric field is 45 Hz, the waveform is a square wave with a ratio of 3:1, and the treatment time is 20 min. Then the product turnover basket is transferred to a 4°C storage for standby. After storage for 12 h, the refrigerated product is placed in boiling water for 6.5 min, and then stir-fried with egg liquid. The mass ratio of broccoli to eggs is 5:1. During the stir-frying process, based on the mass of the broccoli, 1.3% edible salt, 1.6% chicken essence, 2.0% oyster sauce and 2.5% light soy sauce are added, and the stir-frying time is 8 min. Then, the stir-fried broccoli and eggs are quickly cooled to 0°C. Randomly pick about 50 g of the broccoli and measure the chlorophyll content therein. And the ratio of the chlorophyll content in the stir-fried sample to the chlorophyll content in the fresh broccoli is used as the chlorophyll residue rate in the sample. The results are shown in Figure 1 .

[0057] Example 8

[0058] Process 1 + 5, color protection solution immersion + alternating magnetic field treatment:

[0059] Fresh broccoli is shaped, cut, disinfected, surface dehydrated and then transferred to a turnover basket. The turnover basket is covered and immersed in a color protection solution at 55°C for 15 minutes. The color protection solution contains 0.5 wt.% ascorbic acid, 5 wt.% ethanol, 0.3 wt.% ethylenediaminetetraacetic acid, 0.03 wt.% calcium ascorbate, 0.002 wt.% magnesium chloride, 0.03 wt.% potassium citrate and 0.02 wt.% sodium alginate. After treatment, it is rinsed with pure water at 4°C, and the mass of the pure water is 8 times that of the broccoli. Then the surface of the product is surface dehydrated, and after surface dehydration, it is transferred to a turnover basket. The turnover basket is transferred to an alternating magnetic field treatment chamber, and a magnetic field treatment of 100 T / m is applied. The frequency of the magnetic field is 66 Hz, the waveform is a sine wave, and the treatment time is 60 min. And it is quickly transferred to a transfer warehouse at 4°C for standby. After storage for 12 h, the refrigerated product is placed in boiling water for 6.5 min, and then stir-fried with egg liquid. The mass ratio of broccoli to egg liquid is 5:1. During the stir-frying process, based on the mass of the broccoli, 1.3% edible salt, 1.6% chicken essence, 2.0% oyster sauce and 2.5% light soy sauce are added, and the stir-frying time is 8 min. Then, the stir-fried broccoli and eggs are quickly cooled to 0°C, and about 50 g of broccoli is randomly picked from it to measure the chlorophyll content. And the ratio of the chlorophyll content in the stir-fried sample to the chlorophyll content in the fresh broccoli is used as the chlorophyll residue rate in the sample. The results are shown in Figure 1 .

[0060] Example 9

[0061] Process 2 + 3, low-pressure soaking + microwave treatment:

[0062] The fresh broccoli is shaped, cut, disinfected, surface dehydrated and then transferred to a vacuum tank. It is immersed in a color protection solution, and the loading amount is 45% of the volume of the vacuum tank. The pressure of the vacuum tank is reduced to 0.005 MPa, and the pressure reduction time is 30 min. The pressure is maintained for 30 min, and then quickly restored to normal pressure. The color protection solution contains 0.03 wt.% sodium alginate, 0.1 wt.% sodium ascorbate, 0.04 wt.% calcium ascorbate, 0.01 wt.% L-malic acid, 0.01 wt.% phytic acid, 0.1 wt.% guar gum, 0.1 wt.% pectin, 0.1 wt.% xanthan gum, 0.05 wt.% carrageenan, 0.35 wt.% sodium chloride, 0.36 wt.% α-cyclodextrin and 0.35 wt.% sodium bicarbonate; the above procedure is repeated 2 times. After treatment, it is rinsed with pure water at 4°C, and the mass of the pure water is 8 times that of the broccoli. Then it is placed in a turnover basket and left to drain in a 4°C environment. Then the surface of the product is surface dehydrated, and after surface dehydration, it is transferred to a turnover basket. The turnover basket is transferred to a microwave treatment chamber, and microwave treatment is given at 2.0 kW / kg. The wavelength of the microwave is 122 mm and the frequency is 2450 MHz. The treatment time is 3 min, and it is transferred to a 4°C turnover storage for standby. After storage for 12 h, the refrigerated product is placed in boiling water for 6.5 min, and then stir-fried with egg liquid. The mass ratio of broccoli to egg liquid is 5:1. During the stir-frying process, based on the mass of the broccoli, 1.3% edible salt, 1.6% chicken essence, 2.0% oyster sauce and 2.5% light soy sauce are added. The stir-frying time is 8 min. Then, the stir-fried broccoli and eggs are quickly cooled to 0°C, and about 50 g of the broccoli is randomly picked to measure the chlorophyll content. And the ratio of the chlorophyll content in the stir-fried sample to the chlorophyll content in the fresh broccoli is used as the chlorophyll residue rate in the sample. The results are shown in Figure 1 。

[0063] Example 10

[0064] Process 2 + 4, low-pressure immersion + pulsed electric field treatment:

[0065] The fresh broccoli is shaped, cut, disinfected, surface dehydrated and then transferred to a vacuum tank, immersed in a color protection solution, with the loading amount being 45% of the volume of the vacuum tank. The pressure of the vacuum tank is reduced to 0.005 MPa, and the pressure reduction time is 30 min. The pressure is maintained for 30 min, and then quickly restored to normal pressure. The color protection solution contains 0.03 wt.% sodium alginate, 0.1 wt.% sodium ascorbate, 0.04 wt.% calcium ascorbate, 0.01 wt.% L-malic acid, 0.01 wt.% phytic acid, 0.1 wt.% guar gum, 0.1 wt.% pectin, 0.1 wt.% xanthan gum, 0.05 wt.% carrageenan, 0.35 wt.% sodium chloride, 0.36 wt.% α-cyclodextrin and 0.35 wt.% sodium bicarbonate; the above procedure is repeated 2 times. After treatment, it is rinsed with pure water at 4°C, and the mass of the pure water is 8 times that of the broccoli. Then it is placed in a turnover basket and left to drain in a 4°C environment. Then the surface of the product is surface dehydrated, and after surface dehydration, it is transferred to a turnover basket. The turnover basket is transferred to a pulsed electric field treatment chamber, and pulsed electric field treatment is given at 10 kV / m. The frequency of the electric field is 45 Hz, the waveform is a square wave with a ratio of 3:1, the treatment time is 20 min, and it is transferred to a 4°C turnover storage for standby. After storage for 12 h, the refrigerated product is placed in boiling water for 6.5 min, and then stir-fried with egg liquid. The mass ratio of broccoli to egg liquid is 5:1. During the stir-frying process, based on the mass of the broccoli, 1.3% edible salt, 1.6% chicken essence, 2.0% oyster sauce and 2.5% light soy sauce are added, and the stir-frying time is 8 min. Then, the stir-fried broccoli and eggs are quickly cooled to 0°C, and about 50 g of the broccoli is randomly picked to measure the chlorophyll content therein. And taking the proportion of the chlorophyll content in the stir-fried sample to the chlorophyll content in the fresh broccoli as the chlorophyll residue rate in the sample, the results are shown in Figure 1 .

[0066] Example 11

[0067] Process 2 + 5, low-pressure immersion + alternating magnetic field treatment:

[0068] The fresh broccoli is shaped, sliced, disinfected, surface-dehydrated and then transferred to a vacuum tank, immersed in a color protection solution, with the loading amount being 45% of the volume of the vacuum tank. The pressure of the vacuum tank is reduced to 0.005 MPa, and the pressure reduction time is 30 min. The pressure is maintained for 30 min, and then quickly restored to normal pressure. The color protection solution contains 0.03 wt.% sodium alginate, 0.1 wt.% sodium ascorbate, 0.04 wt.% calcium ascorbate, 0.01 wt.% L-malic acid, 0.01 wt.% phytic acid, 0.1 wt.% guar gum, 0.1 wt.% pectin, 0.1 wt.% xanthan gum, 0.05 wt.% carrageenan, 0.35 wt.% sodium chloride, 0.36 wt.% α-cyclodextrin and 0.35 wt.% sodium bicarbonate; the above procedure is repeated 2 times. After treatment, it is rinsed with pure water at 4°C, and the mass of the pure water is 8 times that of the broccoli, and then placed in a turnover basket and left to drain water in an environment at 4°C. Then the surface of the product is surface-dehydrated, and after surface dehydration, it is transferred to a turnover basket. The turnover basket is transferred to an alternating magnetic field treatment chamber, and a magnetic field treatment of 100 T / m is given, the frequency of the magnetic field is 66 Hz, the waveform is a sine wave, the treatment time is 60 min, and it is transferred to a 4°C turnover storage for standby. After storage for 12 h, the refrigerated product is placed in boiling water for 6.5 min, and then stir-fried with egg liquid. The mass ratio of broccoli to egg liquid is 5:1. During the stir-frying process, based on the mass of the broccoli, 1.3% edible salt, 1.6% chicken essence, 2.0% oyster sauce and 2.5% light soy sauce are added, and the stir-frying time is 8 min. Then, the stir-fried broccoli with eggs is quickly cooled to 0°C, and about 50 g of the broccoli is randomly picked out and the chlorophyll content in it is measured. And taking the proportion of the chlorophyll content in the stir-fried sample in the chlorophyll content of the fresh broccoli as the chlorophyll residue rate in the sample, the results are shown in Figure 1 .

[0069] Example 12

[0070] Process 3 + 4, microwave treatment + pulsed electric field treatment:

[0071] After shaping, cutting, disinfecting, and surface dehydration of fresh broccoli, it is transferred into a turnover basket. The turnover basket is transferred into a microwave treatment chamber and given a microwave treatment of 2.0 kW / kg. The wavelength of the microwave is 122 mm, the frequency is 2450 MHz, and the treatment time is 3 min. Then the turnover basket is transferred into a pulsed electric field treatment chamber and given a pulsed electric field treatment of 10 kV / m. The frequency of the electric field is 45 Hz, the waveform is a square wave with a ratio of 3:1, and the treatment time is 20 min. Then the turnover basket is transferred to a 4°C turnover storage for standby. After storage for 12 h, the refrigerated product is placed in boiling water for 6.5 min, and then stir-fried with egg liquid. The mass ratio of broccoli to egg liquid is 5:1. During the stir-frying process, based on the mass of broccoli, 1.3% edible salt, 1.6% chicken essence, 2.0% oyster sauce, and 2.5% light soy sauce are added, and the stir-frying time is 8 min. Then, the stir-fried broccoli and eggs are quickly cooled to 0°C, and about 50 g of broccoli is randomly picked out to measure the chlorophyll content therein. And the proportion of the chlorophyll content in the stir-fried sample to the chlorophyll content in fresh broccoli is used as the chlorophyll residue rate in the sample. The results are shown in Figure 1 。

[0072] Example 13

[0073] Process 3 + 5, microwave treatment + alternating magnetic field treatment:

[0074] After shaping, cutting, disinfecting, and surface dehydration of fresh broccoli, it is transferred into a turnover basket. The turnover basket is transferred into a microwave treatment chamber and given a microwave treatment of 2.0 kW / kg. The wavelength of the microwave is 122 mm, the frequency is 2450 MHz, and the treatment time is 3 min. The turnover basket is transferred into an alternating magnetic field treatment chamber and given a magnetic field treatment of 100 T / m. The frequency of the magnetic field is 66 Hz, the waveform is a sine wave, and the treatment time is 60 min. The turnover basket is transferred to a 4°C turnover storage for standby. After storage for 12 h, the refrigerated product is placed in boiling water for 6.5 min, and then stir-fried with egg liquid. The mass ratio of broccoli to egg liquid is 5:1. During the stir-frying process, based on the mass of broccoli, 1.3% edible salt, 1.6% chicken essence, 2.0% oyster sauce, and 2.5% light soy sauce are added, and the stir-frying time is 8 min. Then, the stir-fried broccoli and eggs are quickly cooled to 0°C, and about 50 g of broccoli is randomly picked out to measure the chlorophyll content therein. And the proportion of the chlorophyll content in the stir-fried sample to the chlorophyll content in fresh broccoli is used as the chlorophyll residue rate in the sample. The results are shown in Figure 1 。

[0075] Example 14

[0076] Process 4 + 5, pulsed electric field treatment + alternating magnetic field treatment:

[0077] The fresh broccoli is shaped, cut, disinfected, and surface dehydrated, then transferred into a turnover basket. The turnover basket is transferred into the pulsed electric field treatment chamber, and given a pulsed electric field treatment of 10 kV / m. The frequency of the electric field is 45 Hz, the waveform is a square wave with a ratio of 3:1, and the treatment time is 20 min. Then the turnover basket is transferred into the alternating magnetic field treatment chamber, and given a magnetic field treatment of 100 T / m. The frequency of the magnetic field is 66 Hz, the waveform is a sine wave, and the treatment time is 60 min. Then the product turnover basket is transferred to a 4°C turnover storage for standby. After storage for 12 h, the refrigerated product is placed in boiling water for 6.5 min, and then stir-fried with egg liquid. The mass ratio of broccoli to eggs is 5:1. During the stir-frying process, based on the mass of broccoli, add 1.3% edible salt, 1.6% chicken essence, 2.0% oyster sauce, and 2.5% light soy sauce, and the stir-frying time is 8 min. Then, the stir-fried broccoli and eggs are quickly cooled to 0°C, and about 50 g of broccoli is randomly picked to measure the chlorophyll content therein. And taking the ratio of the chlorophyll content in the stir-fried sample to the chlorophyll content in the fresh broccoli as the chlorophyll residue rate in the sample, the results are shown in Figure 1 。

[0078] Example 15

[0079] Process 3 + 4 + 5, microwave treatment + pulsed electric field treatment + alternating magnetic field treatment:

[0080] The fresh broccoli is shaped, cut, disinfected, and surface dehydrated, then transferred into a turnover basket. The turnover basket is transferred into the microwave treatment chamber, and given a microwave treatment of 2.0 kW / kg. The wavelength of the microwave is 122 mm and the frequency is 2450 MHz, and the treatment time is 3 min. Then the turnover basket is transferred into the pulsed electric field treatment chamber, and given a pulsed electric field treatment of 10 kV / m. The frequency of the electric field is 45 Hz, the waveform is a square wave with a ratio of 3:1, and the treatment time is 20 min. Then the turnover basket is transferred into the alternating magnetic field treatment chamber, and given a magnetic field treatment of 100 T / m. The frequency of the magnetic field is 66 Hz, the waveform is a sine wave, and the treatment time is 60 min. Then the turnover basket is transferred to a 4°C turnover storage for standby. After storage for 12 h, the refrigerated product is placed in boiling water for 6.5 min, and then stir-fried with egg liquid. The mass ratio of broccoli to egg liquid is 5:1. During the stir-frying process, based on the mass of broccoli, add 1.3% edible salt, 1.6% chicken essence, 2.0% oyster sauce, and 2.5% light soy sauce, and the stir-frying time is 8 min. Then, the stir-fried broccoli and eggs are quickly cooled to 0°C, and about 50 g of broccoli is randomly picked to measure the chlorophyll content therein. And taking the ratio of the chlorophyll content in the stir-fried sample to the chlorophyll content in the fresh broccoli as the chlorophyll residue rate in the sample, the results are shown in Figure 1 。

[0081] Comparative Example 1

[0082] Direct stir-frying:

[0083] The fresh broccoli is shaped, cut, disinfected, surface dehydrated and then quickly transferred to a transfer warehouse at 4 °C for standby. After storage for 12 h, the refrigerated product is placed in boiling water for 6.5 min, and then stir-fried with egg liquid. The mass ratio of broccoli to egg liquid is 5:1. During the stir-frying process, based on the mass of broccoli, 1.3% of edible salt, 1.6% of chicken essence, 2.0% of oyster sauce and 2.5% of light soy sauce are added, and the stir-frying time is 8 min. Then, the stir-fried broccoli and eggs are quickly cooled to 0 °C, and about 50 g of broccoli is randomly selected from it to measure the chlorophyll content. And the ratio of the chlorophyll content in the stir-fried sample to the chlorophyll content in the fresh broccoli is used as the chlorophyll residue rate in the sample. The results are shown in Figure 1 .

[0084] The embodiments described above are only descriptions of the preferred modes of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for maintaining the green color of prefabricated vegetables, characterized in that, Including Method 1 or Method 2, Method 1 includes the following steps: Immerse the green vegetables in a color protection solution, then dehydrate the surface, and subject the surface-dehydrated green vegetables to microwave treatment at 0.5 - 3.5 kW / kg. The wavelength of the microwave is 122 mm, the frequency is 2450 MHz, and the treatment time is 1 - 8 min. Set aside for later use; Method 2 includes the following steps: Place the green vegetables in a pressure-adjustable device filled with a color protection solution. First, reduce the pressure to 0.001 - 0.008 MPa and maintain it for 10 - 45 min, then restore to normal pressure and repeat the cycle twice. After washing, dehydrate the surface, and subject the surface-dehydrated green vegetables to microwave treatment at 0.5 - 3.5 kW / kg. The wavelength of the microwave is 122 mm, the frequency is 2450 MHz, and the treatment time is 1 - 8 min. Set aside for later use; The color protection solution described in Method 1 or Method 2 includes Color Protection Solution A or Color Protection Solution B. Among them, the components of Color Protection Solution A include ascorbic acid 0.1 - 1.2 wt.%, ethanol 0 - 10 wt.%, ethylenediaminetetraacetic acid 0.1 - 1.5 wt.%, calcium ascorbate 0.0005 - 0.05 wt.%, magnesium chloride 0 - 0.005 wt.%, potassium citrate 0 - 0.08 wt.%, and sodium alginate 0 - 0.05 wt.%; the components of Color Protection Solution B include sodium alginate 0.01 - 0.05 wt.%, sodium ascorbate 0.01 - 0.2 wt.%, calcium ascorbate 0.005 - 0.05 wt.%, L-malic acid 0 - 0.01 wt.%, phytic acid 0 - 0.02 wt.%, guar gum 0.02 - 0.1 wt.%, pectin 0.005 - 0.15 wt.%, xanthan gum 0 - 0.2 wt.%, carrageenan 0.02 - 0.1 wt.%, sodium chloride 0 - 0.7 wt.%, α-cyclodextrin 0.05 - 0.5 wt.%, and sodium bicarbonate 0.05 - 1.5 wt.%.

2. A method for maintaining the green color of prefabricated vegetables, characterized in that, Including Method 1 or Method 2, Method 1 includes the following steps: Immerse the green vegetables in a color protection solution, then dehydrate the surface, and subject the surface-dehydrated green vegetables to pulsed electric field treatment at 2 - 40 kV / m. The frequency of the electric field is 34 - 100 Hz, the waveform is a square wave with a ratio of 1 - 6:1, and the treatment time is 1 - 180 min. Set aside for later use; Method 2 includes the following steps: Place the green vegetables in a pressure-adjustable device filled with a color protection solution. First, reduce the pressure to 0.001 - 0.008 MPa and maintain it for 10 - 45 min, then restore to normal pressure and repeat the cycle twice. After washing, dehydrate the surface, and subject the surface-dehydrated green vegetables to pulsed electric field treatment at 2 - 40 kV / m. The frequency of the electric field is 34 - 100 Hz, the waveform is a square wave with a ratio of 1 - 6:1, and the treatment time is 1 - 180 min. Set aside for later use; The color protection solution described in Method 1 or Method 2 includes Color Protection Solution A or Color Protection Solution B. Among them, the components of Color Protection Solution A include ascorbic acid 0.1 - 1.2 wt.%, ethanol 0 - 10 wt.%, ethylenediaminetetraacetic acid 0.1 - 1.5 wt.%, calcium ascorbate 0.0005 - 0.05 wt.%, magnesium chloride 0 - 0.005 wt.%, potassium citrate 0 - 0.08 wt.%, and sodium alginate 0 - 0.05 wt.%; the components of Color Protection Solution B include sodium alginate 0.01 - 0.05 wt.%, sodium ascorbate 0.01 - 0.2 wt.%, calcium ascorbate 0.005 - 0.05 wt.%, L-malic acid 0 - 0.01 wt.%, phytic acid 0 - 0.02 wt.%, guar gum 0.02 - 0.1 wt.%, pectin 0.005 - 0.15 wt.%, xanthan gum 0 - 0.2 wt.%, carrageenan 0.02 - 0.1 wt.%, sodium chloride 0 - 0.7 wt.%, α-cyclodextrin 0.05 - 0.5 wt.%, and sodium bicarbonate 0.05 - 1.5 wt.%.

3. A method for maintaining the green color of prefabricated vegetables, characterized in that, including Method 1 or Method 2, Method 1 includes the following steps: Immerse the green vegetables in the color protection solution, then dehydrate the surface, and apply a magnetic field treatment of 10 - 150 T / m to the surface-dehydrated green vegetables. The frequency of the magnetic field is 10 - 100 Hz, the waveform is a sine wave, and the treatment time is 60 - 180 min. Set aside for later use; Method 2 includes the following steps: Place the green vegetables in a pressure-adjustable device filled with the color protection solution. First, reduce the pressure to 0.001 - 0.008 MPa and maintain it for 10 - 45 min, then restore it to normal pressure, repeat the cycle twice, wash and dehydrate the surface, and apply a magnetic field treatment of 10 - 150 T / m to the surface-dehydrated green vegetables. The frequency of the magnetic field is 10 - 100 Hz, the waveform is a sine wave, and the treatment time is 60 - 180 min. Set aside for later use; The color protection solution described in Method 1 or Method 2 includes Color Protection Solution A or Color Protection Solution B. Among them, the components of Color Protection Solution A include ascorbic acid 0.1 - 1.2 wt.%, ethanol 0 - 10 wt.%, ethylenediaminetetraacetic acid 0.1 - 1.5 wt.%, calcium ascorbate 0.0005 - 0.05 wt.%, magnesium chloride 0 - 0.005 wt.%, potassium citrate 0 - 0.08 wt.%, and sodium alginate 0 - 0.05 wt.%; the components of Color Protection Solution B include sodium alginate 0.01 - 0.05 wt.%, sodium ascorbate 0.01 - 0.2 wt.%, calcium ascorbate 0.005 - 0.05 wt.%, L-malic acid 0 - 0.01 wt.%, phytic acid 0 - 0.02 wt.%, guar gum 0.02 - 0.1 wt.%, pectin 0.005 - 0.15 wt.%, xanthan gum 0 - 0.2 wt.%, carrageenan 0.02 - 0.1 wt.%, sodium chloride 0 - 0.7 wt.%, α-cyclodextrin 0.05 - 0.5 wt.%, and sodium bicarbonate 0.05 - 1.5 wt.%.

4. The method for maintaining the green color of prefabricated vegetables according to any one of claims 1 to 3, characterized in that, The temperature of the color protection liquid described in Method 1 is 50 - 65°C, and the soaking time of green vegetables in the color protection liquid is 10 - 25 min.

5. The method for maintaining the green color of prefabricated vegetables according to any one of claims 1 to 3, characterized in that, The time for the pressure to drop to the set value in Method 2 described above is 30 min.

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